The 43rd Annual International Meeting of the Electron Spin Resonance Spectroscopy Group of the Royal Society of Chemistry

Cardiff University 21st – 25th March 2010 Contents

Conference programme...... F1

Sponsors...... F5

EPR at Cardiff – A brief history...... F6

Bruker Prize Lecture...... F7

Jeol Prize Lectures...... F8

Information for delegates...... F9

Excursion and free time...... F12

Map...... F13

RSC ESR Group Committee...... F14

Conference Proceedings...... F15

Next meeting...... F16

Conference lectures...... T1 - T43

Conference posters...... P1 - P35

Title index...... R1

Author index...... R5

Contact details...... R7

Conference Programme All lectures will be in the Large Chemistry Lecture Theatre (LCLT), Main Building. All Poster presentations will be held in the Viriamu Jones Gallery, Main Building. Sunday 21st March 14.00 – 17.30 Registration Viriamu Jones Gallery, Main Building 18.00 – 19.30 Dinner Aberdare Hall 19.30 – 21.30 RSC Wine Reception Council Chamber, Main Building

Monday 22nd March 07.00 – 08.45 Breakfast Parc Hotel 08.00 – 08:50 Registration Viriamu Jones Gallery, Main Building Session 1 Chair: David Collison 08.55 – 09.00 Peter J. Knowles Welcome note Keynote Lecture: Stereoselective 09.00 – 09.40 Damien M. Murphy interactions in asymmetric metal complexes probed by EPR spectroscopy EPR as a probe of spin density distribution in 09.50 – 10.05 Mark Whiteley organometallic radicals with extended carbon chain ligands EPR spectroelectrochemistry applied to main 10.10 – 10.25 René T. Boeré group compounds 10.30 – 11.00 Tea & Coffee Viriamu Jones Gallery, Main Building Session 2 Chair: Rachel Haywood Invited Lecture: Cyclodextrin-included 11.00 – 11.20 Victor Chechik nitroxides The dienolic compound PG3, a novel 11.25 – 11.40 Béatrice Tuccio cheletropic trap for nitric oxide EPR detection DEER measurements of a Cytochrome P450 11.45 – 12.00 Alice Bowen and Ferredoxin complex to determine the docked structure. Molecular structure refinement by direct 12.05 – 12.20 Matthew Krzystyniak atomic coordinate fitting to ESR spectra 12.30 – 13.45 Lunch Viriamu Jones Gallery, Main Building Session 3 Chair: Damien Murphy Jeol Student Prize Talk: Coexistence of quantum and classic behaviour in EMR 14.00 – 14.15 Lisa Castelli spectra of magnetic nanoparticles and molecular nanomagnets. Jeol Student Prize Talk: CW and pulsed Hans Moons 14.20 – 14.35 EPR characterization of soluble metal

phthalocyanines lacking C-H bonds Jeol Student Prize Talk: Electron spin 14.40 – 14.55 Richard M. Brown coherence times of metallofullerenes Tea & Coffee: 15.00 – 16.30 Viriamu Jones Gallery, Main Building Posters (EVEN) Session 4 Chair: John H. Enemark Invited Lecture: Surface stabilized inorganic 16.30 – 16.50 Elio Giamello radical and radical ions On the formation of O - radicals by 16.55 – 17.10 Tomas Risse 2 adsorption of O2 on thin MgO films Quantum information storage using electron 17.15 – 17.30 John J. L. Morton and nuclear spins in silicon 18.00 – 19.30 Dinner Aberdare Hall 19.30 – 21.00 JEOL Reception Council Chamber, Main Building Free bar 21.00 – 22.30 Graduate Centre, Student’s Union (sponsored by JEOL)

F1 Tuesday 23rd March 07.00 - 08.45 Breakfast Parc Hotel Session 5 Chair: Christopher Kay Keynote Lecture: Pulsed EPR spectroscopy 09.00 – 09.40 John H. Enemark and DFT calculations for “difficult” nuclei EPR-HYSCORE study of quinone binding in 09.50 – 10.05 Bruno Guigliarelli respiratory nitrate reductase: molecular basis for the adaptation to aerobiosis Understanding the catalytic mechanism of methane production by methyl-coenzyme M 10.10 – 10.25 Jeffrey Harmer reductase with labeled substrates and substrate analogues 10.30 – 11.00 Tea & Coffee Viriamu Jones Gallery, Main Building Session 6 Chair: David Norman Invited Lecture: Analysis of magnetic interactions in EPR and ENDOR: an 11.00 – 11.20 Reinhard Kappl approach to electronic and structural properties of redox centres in enzymes PELDOR on DNA: orientations, dynamics, 11.25 – 11.40 Olav Schiemann bending, non-covalent labelling and protein binding Extreme sensitivity and distance 11.45 – 12.00 David G. Norman measurement: PELDOR on deuterated proteins An EPR study of dehaloperoxidase from 12.05 – 12.20 Dimitri A. Svistunenko Amphitrite ornate – an oxygen storing globin with a peroxidase function Delegate Group Outside Viriamu Jones Gallery (entrance to 12.30 – 12.35 Photograph Main Building) 12.35 – 13.45 Lunch Council Chamber, Main Building 14.00 – 17.00 Excursion Cardiff Castle 18.00 – 19.20 Dinner Aberdare Hall Session 7 Chair: David Collison Bruker Lecture: The Fidelity of Spin 19.30 – 20.45 Ron Mason Trapping 20.45 – 21.30 Bruker Reception Council Chamber, Main Building Free Bar 21.30 – 22.30 Graduate Centre, Student’s Union (sponsored by Bruker)

F2

Wednesday 24th March 07.00 – 08.45 Breakfast Parc Hotel Session 8 Chair: Fraser MacMillian 09.00 – 09.40 A. William Rutherford Keynote Lecture: EPR of Photosystem II Distance measurements in a WALP23 polypeptide labeled with a nitroxide radical 09.50 – 10.05 Maxim Yulikov and a lanthanide complex: relaxation enhancement, DEER and cw power saturation Probing flexibility in porphyrin-based 10.10 – 10.25 Janet Lovett molecular wires using DEER. 10.30 – 11.00 Tea & Coffee Viriamu Jones Gallery, Main Building Session 9 Chair: Takeji Takui Invited Lecture: Time-resolved high-field EPR spectroscopy on natural 11.00 – 11.20 Oleg G. Poluektov photosynthesis: primary electron transfer reactions in photosystem I. Prediction of motional EPR spectra from 11.25 – 11.40 Vasily S. Oganesyan Molecular Dynamics (MD) simulations Neuroglobin: a continuing challenge for EPR 11.45 – 12.00 Maria Ezhevskaya spectroscopy High performance, high power, high 12.05 – 12.20 Graham Smith bandwidth, pulsed EPR at 94 GHz 12.30 – 13.45 Lunch Council Chamber, Main Building Session 10 Chair: A. William Rutherford Invited Lecture: Photosensitzed formation 14.00 – 14.20 Tadeusz Sarna of free radicals and singlet oxygen by a Pd- bacteriochlorophyll derivarive SDSL and EPR spectroscopy applied for 14.25 – 14.40 Johann P. Klare structural and functional studies on human guanylate binding protein I A novel tool to selectively resolve distances 14.45 – 15.00 Fraser MacMillan in complex macromolecular structures Nano graphites studied by Electron 15.05 – 15.20 Antonio Barbon Paramagnetic Resonance: An insight on the nature of the signals Tea & Coffee: 15.25 – 16.15 Viriamu Jones Gallery, Main Building Posters (ODDS) Session 11 Chair: Ron Mason Invited Lecture: EPR investigation of 16.15 – 16.35 Sabine Van Doorslaer cationic radicals for organic electronics applications Electron dynamics in lithium ammonia 16.40 – 16.55 Kiminori Maeda solutions probed by X- and W-band Pulse EPR Analytical derivatives of spin dynamics 17.00 – 17.15 Ilya Kuprov simulations Optimization of dynamic nuclear polarization 17.20 – 17.35 Maria-Teresa Türke experiments in aqueous solution at 15 MHz/9.7 GHz for a shuttle DNP spectrometer 17.45 – 18.00 AGM ESR Group RSC LCLT (all welcome to attend)

19.00 – 19.30 Pre-dinner drinks Aberdare Hall 19.30 – 21.00 Banquet Aberdare Hall

F3

Thursday 25th March 07.00 - 08.45 Breakfast Parc Hotel Session 12 Chair: Ilya Kuprov Keynote Lecture: Pulse-based electron magnetic resonance spin technology and a 09.00 – 09.40 Takeji Takui chemists’ materials challenge: A few steps towards molecular spin quantum computers and quantum information processing EPR studies of linked antiferromagnetic 09.50 – 10.05 Floriana Tuna rings: towards quantum information processing Molecular magnets as qubits: extending the 10.10 – 10.25 Christopher J. Wedge phase coherence time 10.30 – 11.00 Tea & Coffee Viriamu Jones Gallery, Main Building Session 13 Chair: Victor Chechik DNA radical-intermediates in UVA-irradiated 11.00 – 11.15 Rachel M. Haywood DNA-riboflavin/melanin systems? Investigating a cell signalling protein using 11.20 – 11.35 Richard Ward PELDOR Pulsed EPR studies of the excited triplet 11.40 – 11.55 Vasileia Filidou state in diethyl fullerene malonate Uncoupled spins spaced by an insulating 12.00 – 12.15 Stephen Sproules tetraphoshine unit: A little D measured by cw EPR 12.30 – 13.45 Lunch Aberdare Hall, Main Building CONFERENCE END - DEPARTURE

F4 Conference Sponsors:

We are grateful to our sponsors: Cardiff University, Bruker Biospin, JEOL UK, The Royal Society of Chemistry and Penderyn.

F5 EPR at Cardiff – A brief history

EPR research in the School of Chemistry, Cardiff University, dates back to the mid-1960s. The first EPR group was established by Alwyn Gwynne Evans (1912 – 2004). Based on his growing interests in the technique, A.G. Evans hosted a meeting in the Main Building, School of Chemistry at Cardiff University (known then as University College Cardiff) on 18/12/1968 to discuss the formation of 'An ESR Group of the Chemical Society'. This group has remained active over the years, so we are pleased to host the 43rd International meeting of the Group, following on from previous conferences at Cardiff in 1978, 1983, 1988 and 1994.

A.G. Evans was interested in the reactions of radical cations and quickly realised the importance of ESR spectroscopy in probing these systems. In collaboration with his former PhD student, Jeff C. Evans (1938-1990) at Cardiff, they developed expertise in the characterisation of radical cations and anions using solution ENDOR techniques during the 70s and 80s. During this time, Christopher C. Rowlands, joined the group having completed his PhD with A.G. Evans in 1977. C.C. Rowlands was also heavily involved in the organisation of the annual ESR conference, taking on the roles as Secretary & Treasurer of the ESR group of the RSC from 1987-1997. C.C. Rowlands was the Director of the National ENDOR facility (1996-2003) and his research interests, particularly in heterogeneous photochemistry, remained until his early retirement in 2003.

Following the untimely death of J.C. Evans in 1990, Bryn Mile (1936-2008) joined the group from 1990 – 1995. B. Mile was interested in the reactions of metal atoms with organic molecules using cryochemical techniques.

Dr. Damien Murphy subsequently joined the EPR group at Cardiff University in 1996. The current research group houses a range of EPR equipment, dedicated to specific projects, and based on five spectrometers, including X-band cw-EPR (Bruker EMX), X-band single crystal Ultra High Vacuum EPR-XPS (Bruker EMX), X-band cw-EPR (Varian), X-/Q-band cw-ENDOR spectroscopy (Bruker ESP300), and X-band Pulsed EPR (Bruker ELEXSYS E580) with PELDOR and ENDOR accessories. The research interests of the current group focus on EPR and ENDOR to study paramagnetic complexes in homogeneous systems and at heterogeneous oxide surfaces, with a major emphasis in catalysis.

D.M. Murphy, 2010

F6

Bruker Prize Lecture and Reception

Since 1986 Bruker BioSpin has generously sponsored an annual lectureship and prize, given to a scientist who has made major contributions to the application of ESR spectroscopy in chemical or biological systems.

We are pleased to announce that The Bruker Prize 2010 has been awarded to:

Ronald P. Mason

National Institute of Environmental Health Sciences, North Carolina, USA

The lecture will take place on Tuesday 23rd March in the Large Chemistry Lecture Theatre (19.30), followed by the Bruker-sponsored Wine Reception in the Council Chamber and a Free Bar in the Graduate Centre also kindly sponsored by Bruker.

The title of his lecture will be:

The Fidelity of Spin Trapping

Previous winners of the Bruker Lectureship

1986 M.C.R. Symons 1995 H.M. McConnell 2004 W.L. Hubbell 1987 K. Möbius 1996 B. M. Hoffman 2005 K.-P. Dinse 1988 H. Fischer 1997 K.A. McLauchlan 2006 Yu.D. Tsvetkov 1989 J.S. Hyde 1998 J.R. Pilbrow 2007 D. Goldfarb 1990 J.H. Freed 1999 J. Schmidt 2008 E.J.J. Groenen 1991 E. de Boer 2000 D. Gatteschi 2009 G. Jeschke 1992 G. Feher 2001 J. Hütterman 1993 N. M. Atherton 2002 G.R & S.S Eaton 1994 A. Schweiger 2003 W. Lubitz F7

JEOL student prize lectures

The JEOL competition is open to postgraduates in their 2nd or 3rd year and postdoctoral fellows in their 1st year. The 15 minutes lectures are judged by the ESR Spectroscopy Group Committee on the basis of their scientific content and delivery. An engraved medal and monetary prize are generously provided by JEOL for the winner of the presentation, to be presented at the conference banquet.

This year, the competition will take place during the Monday afternoon session. The 2010 lectures, selected on the basis of the abstracts submitted, will be:

Coexistence of quantum and classic behaviour in EMR spectra of magnetic nanoparticles and molecular nanomagnets Lisa Castelli, Università di Firenze, Italy

CW and pulsed EPR characterization of soluble metal phthalocyanines lacking C-H bonds Hans Moons, University of Antwerp, Belgium

Electron spin coherence times of metallofullerenes Richard M. Brown, Oxford University, UK

The wine reception on Monday evening is kindly sponsored by JEOL, followed by a Free Bar in the Graduate Centre, also kindly sponsored by JEOL.

F8 Information for delegates

Location All conference events will take place in the Cathays Campus of Cardiff University (see University Map) including lectures, receptions, meals and banquet. Specific room locations are described below in the relevant section.

Detailed instructions on how to arrive at the Cathays Campus can be found at the following link: http://www.cardiff.ac.uk/locations/directions/index.html

Accommodation will be in The Parc (Thistle) Hotel. The Hotel is situated on the junction of Park Place and Queen Street (see University Map). Please note, if arriving at the hotel by Taxi ensure to ask for The Parc (Thistle) Hotel; as there is another nearby hotel called The Park Plaza, and it often creates confusion! Your room will be booked in your name, so you may go directly to the hotel before registration (particularly if you have luggage) if you wish.

Location & Registration Conference registration will take place on Sunday afternoon between 14.00 – 17.30 in the Viriamu Jones Gallery, which is situated within the Main Building (Building 39 on the University Map). Entry to the Viriamu Jones Gallery is either from the rear of the Main Building (via Park Place) or via the front of the Main Building (via Museum Avenue). The desk will remain open for the duration of the conference.

Tea and Coffee Breaks Tea and coffee will be served in the Viriamu Jones Gallery during the morning and afternoon.

Meals Breakfast will be served in The Parc (Thistle) Hotel. Please ask the receptionist for exact times. Lunches will be served in the following venues: Monday 22nd March Cold Fork Buffet Viriamu Jones Gallery Tuesday 23rd March Cold Fork Buffet Council Chamber Wednesday 24th March Cold Fork Buffet Council Chamber Thursday 25th March Cold Fork Buffet Aberdare Hall All evening meals (dinners) will be served in Aberdare Hall Dining Room (Building 22, University Map), including the Banquet.

Receptions All wine receptions will be held in the Council Chamber of the Main Building. The sponsors of the wine receptions are given in the programme guide. On Monday and Tuesday evenings the wine receptions will be followed by an open bar in the Graduate Centre. This is located within the Student Union’s building (Building 38 on University Map) opposite the Main Building; directions will be given in the evening. The pre-banquet drinks reception will be held in Aberdare Hall. There is also a nice, traditional and secluded Welsh Pub (called the Pen & Wig) serving a range of beers which is half distance between the Main Building F9 and the Hotel (it is located on a small side street called Park Grove, adjoining St. Andrews Place and Museum Place on the University Map; close to building 50).

Shops A small coffee shop is located in the Main Building (just behind the Viriamu Jones gallery). A range of larger shops, with cash machines, are available in the Cardiff University Students Union building, directly across from the Main Building (Building 38 University Maps). Finally, the Parc (Thistle) Hotel is situated in the Main Shopping area of Cardiff City Centre. An enormous range of shops and retail stores, based in three different shopping centres, are all within 10 minutes walk of the Hotel (see highlighted area of Map).

Accompanying Persons Accompanying persons have access to all meals and social events. We do not offer a specific programme for accompanying persons, but there are many places of interest in the local vicinity of Cardiff University, all within walking distance of the hotel. Please speak to a local organizer for further information.

Lectures & Speaker Information All lectures will be held in the Large Chemistry Lecture Theatre (LCLT) on the 1st floor of the Main Building.

A range of AV equipment is available including data projectors, overhead projectors and slide projectors. Speakers are requested to upload their presentation a day prior to their talk (although facilities for Laptop computers and Macs are available). Please hand in your file (pdf or ppt) to the registration desk or to a local organiser. Make sure you enable the option when saving your presentation to avoid font and figure corruption.

Please allow time at the end of all lectures for discussions. Keynote lectures will be 40 minutes + 10 minutes of discussion, Invited lectures will be 20 minutes + 5 minutes of discussion, while contributed lectures and JEOL student Prize talks will be 15 minutes + 5 minutes of discussion. Please would all speakers ensure they keep strictly to the time schedule for their talks. Chairs are also advised to adhere to their session time schedule.

Poster Sessions Posters will be displayed in the Viriamu Jones Gallery and should be displayed for the duration of the conference. There will be two poster sessions; the first on Monday afternoon for EVEN numbered posters, and the second on Wednesday afternoon for ODD numbered posters. Please remove your posters on Thursday morning. Posters will be mounted using velcro sticky labels which will be provided. Poster boards will accommodate A0 size.

Left Luggage There is a left luggage facility available at the hotel. For delegates wishing to leave directly from the University, please speak to a local organiser on the day of

F10 your departure. A secure room close to the lecture theatre has been set aside for left luggage.

Internet Access Wireless internet access is available throughout The Parc (Thistle) Hotel via your own laptop at the following rates (please check with the hotel to confirm rates): £6 for 60 minutes £10 for 24 hours Unfortunately, the hotel does not have a general access computer for guests.

Free internet access (including Wireless access throughout the Main Building) at the University will be available. Delegates wishing to make use of this facility are asked to contact a local organiser preferably before their arrival in Cardiff, as only a limited number of guest user accounts will be made available to us. Usernames/passwords to access the accounts will be available at registration.

Cardiff University is registered for Eduroam access. Delegates whose home institute is also registered with this service can access the internet through their own account. Instructions for accessing this facility can be found by following the link: http://www.cardiff.ac.uk/insrv/it/network/wireless/eduroam.html

Car Parking Car parking in and around the Main Building of Cardiff University, which is effectively a city centre location, is extremely difficult. Public parking around the Main Building is by meter (Pay & Display).

Alternatively, The Parc Thistle Hotel has a private/secure on-site car park, which is available to hotel guests at a small cost. Delegates are asked to organise this themselves directly with the hotel.

Transport Around Cardiff All events & locations taking place during the conference are held within 10 minutes walking distance (including the hotel, lectures and dinners). Delegates wishing to visit the waterside development of Cardiff Bay are advised to use the train service which runs from Cathays Station (situated behind the Students Union building) and Cardiff Queen Street station (less than 5 minutes walk from the hotel) directly to Cardiff Bay station (see University Map). The journey time is only 5 minutes, and the service runs every 10 minutes. Tickets can be purchased directly from a ticket machine on the station platform (at Cathays Station) or from the ticket office (at Queen Street station).

Taxis Delegates can arrange taxi hire through The Parc (Thistle) Hotel reception desk, or alternatively directly themselves with the following companies. Capital Cabs +44(0)2920 777777 Dragon Taxis +44(0)2920 333333

F11 Excursion and Free Time– Tuesday 23rd March

Cardiff Castle Cardiff Castle is one of Wales' leading heritage attractions and a site of international significance. Located at the heart of the capital, within beautiful parklands, the Castle's walls and fairytale towers conceal 2,000 years of history.

The Roman fort at Cardiff was probably established at the end of the 50s AD, on a strategic site that afforded easy access to the sea. Archaeological excavations made during the 1970s indicate that this was only the first of four forts, each a different size, that occupied the present site. Remains of the Roman wall can be seen today. Inside the walls, each breathtaking room has its own special theme, including Mediterranean gardens and Italian and Arabian decoration.

The Castle passed through the hands of many noble families until in 1766, it passed by marriage to the Bute family. The 2nd Marquess of Bute was responsible for turning Cardiff into the world's greatest coal exporting port. The Castle and Bute fortune passed to his son John, the 3rd Marquess of Bute, who by the 1860s was reputed to be the richest man in the world.

Please Note: Due to space restrictions inside the Castle, the maximum group size per tour is limited to 25 people. We have therefore arranged for several tours during the afternoon, starting at different times. There will be a “sign-up” sheet available at the registration desk for you to sign against an allocated time-slot. Please ensure you are at the Castle entrance at the correct time.

National Museum Cardiff The National Museum of Wales is located in the Civic Centre, within easy walking distance of the hotel. Entrance to the museum is free, so delegates are warmly invited to visit the museum in their own time. The museum houses Wales’s national archaeology, art, geology and natural history collections as well as major touring and temporary exhibitions.

Cardiff Bay – Europe’s Largest Waterfront Development Cardiff Docks, as it was then called, was the world's largest coal exporting port during the Industrial Revolution. Cardiff Bay has recently been turned into a vast freshwater lake with the introduction of a barrage and is now home to a number of attractions such as Techniquest Science Discovery Centre (ideal for all the family), Craft in the Bay, The Welsh Assembly at the Pierhead, Butetown History and Arts Centre, Goleulong 2000 Lightship, the Norwegian Church Arts Centre and the brand new Wales Millennium Centre, a stunning and international arts centre. Cardiff Bay is easy to reach from the hotel or University (5 minutes by train), so weather permitting, is an ideal place to spend the afternoon.

F12 Map 4 University and City Centre Additional Street Information Index

All Nations Centre B7 89 Adam Street F2 Albany Road F5 BritishCouncil E 3 53 Allensbank Road D7 Cardiff International Australia Road B6 Arena E 1 84 Basil P lace E 4 Birchwood L ane F7 E 1 Central Library 80 Birchwood Road E 7 Central PoliceStation D3 54 Boulevard de Nantes D3 Braeval Street E 5 MAP 5 City Hall D3 55 Brandreth Road E 7 Coach Station D1 86 Bridge Street E 2 Brydges P lace D4 LawCourts D3 56 Bute Street E 1 Post Office: Queens Arcade D2 71 Bute Terrace E 1 Temple of Peace D3 36 Canada Road C7 Castle Street D2 University of Cathays Terrace D5 Wales Registry D3 51 Cathedral Road B3 RoyalWelsh College Catherine Street D4 Central Link F1 of Music andDrama C3 48 Charles Street E 2 WelshAssembly Churchill Way E 2 Government Offices D4 29 City Road E 4 Clare Street C1 Welsh Assembly Map2 D2 96 Claude Road F5 Coburn Street E 4 Hospital Cogan Terrace D4 University Hospital Accident College Road D3 andE mergency Unit C7 1 Colum Drive D4 Colum Road C4 Attractions Colum P lace C5 Cardiff Bay Corbett Road D4 Visitor Centre Map2 D2 97 Cottrell Road F5 CowbridgeRoadE ast A2 Cardiff Castle D2 64 Crown Way C6 Llandaff Cathedral Map2 B4 90 Crwys Road D5 National Museum and CustomHouse Street E 1 Dalcross Street E 5 D3 Gallery of Wales 52 Dalton Street D5 Techniquest Map2 D2 94 Daviot Street E 5 Despenser Street C2 Theatres Duke Street D2 NewTheatre E 3 61 Dumfries P lace E 3 E ast Grove F3 ShermanTheatre E 3 40 E xcelsior Way A6 Chapter Arts Centre A2 62 Fairoak Road D6 Fanny Street D5 Concert Halls Fitzalan Place F2 St David’s Hall D2 76 Fitzhamon E mb C2 Fitzroy Street E 4 University Concert Hall C4 19 Flora Street D5 University Buildings Wales Millennium Gordon Road E 3 Centre Map2 D2 96 Glossop Road F3 Halls of Residence Glynrhondda Street E 4 ShoppingArea Cinemas Greyfriars Road D2 Harriet Street E 4 Cineworld E 2 83 PedestrianisedShoppingArea Hayes Bridge Road E 1 Odeon Map2 D2 92 Herbert Street E 1 P UniversityCar Parks Vue D1 99 High Street D2 Hill’s Street E 2 P PublicCar Parks Sport King EdwardVII Ave D3 Kingsway D2 Athletic Stadium Map2 B3 88 Lake Road East E 7 Cardiff CityFC A1 87 Lake RoadWest E 7 Cardiff RFC D2 78 L eckwith Road A1 LlanbleddianGardens E 4 Cardiff Tennis Club D3 57 Llandaff Road A3 Glamorgan County L landough Street D4 Llantwit Street E 3 Aberdare Hall Cricket Club B3 32 Lower Cathedral Road C2 MaindyAthletic Stadium/ L owther Road E 4 Swimming Pool C5 6 Mackintosh P lace E 6 Maindy Road D4 Millennium Stadium D1 81 Mary Ann Street E 2 Main Building Superbowl Map2 D4 91 May Street D5 WelshInstituteof Sport C3 44 Mill L ane E 1 Minny Street D5 Shopping Miskin Street E 4 Moira P lace F2 Capitol Centre E 2 68 Monthermer Road E 6 Cardiff Bay Moy Road E 5 Retail Park Map2 C2 93 Mundy P lace D4 Museum Avenue D3 CastleArcade D2 72 Museum P lace E 3 Student Union Central Market D2 75 Neville Street C2 New Zealand Road C6 Queen’s Arcade D2 71 Newfoundland Road B6 Queen’sWest D2 65 Newport Road F3 Royal Arcade D1 82 Ninian Road E 6 Ninian Park Road B1 St David’s Centre E 2 73 North Road C5 St David’s 2 E 2 85 P ark P lace D4 Penarth Road D1 Penylan Road F6 R esidences P lasnewydd Road F4 Queen Street E 2 Aberconway Hall C4 12 Rhymney Street E 4 Aberdare Hall C4 22 Rhymney Terrace E 5 Richards Street E 5 Allensbank House D7 98 Richmond Road E 4 Cartwright Court E 6 4 Ruthin Gardens D4 Colum Hall C4 13 Salisbury Road E 4 Schooner Way F1 E 3 Gordon Hall 43 Senghennydd Road D4 Hodge Hall D4 17 Severn Grove A3 Roy Jenkins Hall D5 8 Severn Road A2 St Andrew’s P lace E 3 SenghennyddCourt E 3 47 St J ohn Street D2 SenghennyddHall E 3 46 St Mary Street D1 St Peter’s Street F3 Talybont North/South B6 5 Parc Thistle Hotel StationTerrace E 2 Talybont Court B5 7 Strathnairn Street F5 University Hall and Stuttgart Strasse E 3 Conference Centre F7 2 The Friary D2 The Hayes E 2 The P arade F3 L ibraries The Walk F3 Thesiger Street E 4 Aberconway & Guest C5 11 Tudor Street C1 Arts& SocialStudies D4 18 Ty Draw Road F6 Bute& Architecture D3 45 Ty Gwyn Road F7 Duthie Library Map5 112 Tyndall Street F1 Julian Hodge Wellfield Road F5 Resource Centre C4 14 Wellington Street B2 West Grove E 3 Law D4 18 Westgate Street D2 Legal PracticeLibrary D4 28 Whitchurch Road D6 Music D4 23 Windsor P lace E 3 Biomedical Sciences D4 35 Windsor Road F2 Wood Street D1 Science D3 39 Woodville Road D5 Senghennydd E 3 42 Working Street D2 Trevithick E 3 58 Wyverne Road E 4 Cathays Park Campus (Map 4) Tel Switchboard: 029 2087 4000 Map 5 Heath Park Campus

Aberconway Building C5 11 CUBRIC D4 30 Graduate Centre D3 38 Occupational Safety, Research andCommercial ARCCA C3 33 Day Care Services D3 41 Health Centre D4 37 Health and Division F3 66 E nvironmental Unit D4 37 Architecture D3 45 Development and History & Residences and Catering B6 3 Biosciences D4,D3 35 39 Alumni Relations D3 41 Archaeology D4 16 Optometry and VisionSciences D4 15 Security Centre D4 35 Business School C5 11 E arth andOcean Humanities Building D4 16 Sciences D3 39 * Bute Building D3 45 Human Resources F3 66 Pharmacy C3 33 Social Sciences 31 42 49 50 E astgate House F3 59 D4,E3,D3*,E3 Careers Service C4 25 International Development Physics and andE nglish Language Sports Centre Centre for AdvancedStudies E ngineering E 3 58 Astronomy E 3 58 Services D3 41 –Talybont B6 3 in the Social Sciences D3 41 E nglish Communication Planning F3 66 D4 Journalism,Media and Student Support Centre for Professional andPhilosophy 16 Psychology D4,D4* 9 27* Cultural Studies D3 45 Centre D4 31 Legal Studies D4 28 E states Division F3 66 JulianHodgeBuildingC4 14 Public Relations and Students’Union D3 38 Chaplaincy C4,D4 10 26 E uropean Studies Law D4,D4* 24 28* Communications D3 41 Chemistry D3*,E 339* 50 (E uropean Languages Tower Building D4 27 F3 andPolitics) D4 24 Lifelong Learning E 3 42 Purchasing 66 City andRegional Trevithick Building E 3 58 Queen’s Buildings E 3 58 Planning D3 49 E ye Clinic D4 15 Main Building D3 39 Welsh D4 16 Computing Centre D3 41 Finance Division F3 66 Mathematics E 3 42 RedwoodBuilding C3 33 Welsh Centre for Postgraduate Computer Science E 3 58 Fitness & Squash McKenzie House F3 66 Religious and Pharmaceutical * Governance and Centre–Park Place D4 34 Music D4,D4* 20 23 Theological Studies D4 16 E ducation C4 21 Compliance F3 66 Glamorgan Building D3 49 Nursing F3 59 Registry F3 66 * Indicates main site Heath Park Campus (Map 5) Tel Switchboard: 029 2074 7747 TheUniversity sharestheHeathPark CampuswiththeUniversity Hospital of Wales(UHW). Brecknock House 101 Dental School/Hospital 106 Medical School 110 Nursing& Midwifery 116 Student SupportF13 Centre 103 Cardiff Medicentre 102 Glamorgan House 107 Monmouth House 111 Pembroke House 113 Tenovus Building 118 Postgraduate Medical and TyˆDewi Sant Building 116 Cardigan House 103 Healthcare Studies 116 NeuaddMeirionnydd 122 Dental E ducation 122 HenryWellcome TyˆMaeth 119 Carmarthen House 104 NewLectureTheatre complex 114 Research Building 108 Radnor House 115 Wales Heart Denbigh House 105 Institute of Medical Genetics 109 NHS LiaisonUnit 103 Sports& SocialClub 117 ResearchInstitute 120

Committee of the ESR Spectroscopy Group of the Royal Society of Chemistry

Prof David Collison (Chairman) University of Manchester (2007-2010) Dr Chris Kay (Secretary) University College London (2006-2011) Dr Victor Chechik (Treasurer) University of York (2005-2010) Dr Fraser MacMillian University of East Anglia (2007-2010) Dr Damien Murphy Cardiff University (2008-2011) Dr Rachel Haywood RAFT Institute (2008-2011) Dr Christiane Timmel Oxford University (2009-2012) Dr David Norman University of Dundee (2009-2012) Dr Ilya Kuprov (Web master) Oxford University (2009-2012)

(see http://www.esr-group.org/)

Local Organising Committee (Cardiff University)

Dr Damien Murphy Dr Emma Carter Ms Lucia McDyre Ms Marie-Elena Owen

F14 Publication of Conference Proceedings

The publishers of Magnetic Resonance in Chemistry (Wiley) have agreed to use one of this year’s issues for papers submitted as part of the Cardiff RSC ESR Conference. Quality and refereeing standards will be the same as for any individual submission to this journal. If there are sufficient papers of good quality to fill one issue, then that issue will be dedicated solely to the RSC ESR Conference. Fewer papers will mean sharing an issue with normally submitted articles.

This year’s Bruker Lecturer, Ron Mason, has agreed to write a mini-review for the issue. The topics of papers should be in line with the normal subject matter of the journal, and hence involve applications of EPR spectroscopy to chemistry (physical, organic, inorganic), biochemistry, medicinal chemistry or materials chemistry.

For information to authors, please visit http://www3.interscience.wiley.com/journal/117935720/grouphome/ForAuthors.html

Articles can be submitted to the journal at any time, and in the covering letter authors should indicate that they wish the article to be considered for publication in the special issue. The absolute deadline for submission will be 1 July 2010, but earlier submission will be much appreciated. However, authors should indicate their intention to submit an article whilst at the conference, or before.

F15 The 44th Annual International Meeting of the Electron Spin Resonance Spectroscopy Group of the Royal Society of Chemistry

will be held at

3 - 7 April 2011

Further details will be available on http://www.esr-group.org/

F16 Stereoselective interactions in asymmetric metal complexes probed by EPR spectroscopy

Damien M. Murphy

School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK.

Asymmetric synthesis is concerned with the preparation of optically pure compounds of vital importance in the pharmaceutical, agrochemical, fragrance and flavour industries. Since the chemical properties of individual enantiomers can be very different when they interact with other chiral molecules a range of strategies have been developed to produce single enantiomer compounds. Within this field of asymmetric synthesis, asymmetric catalysis is one ideal method for synthesizing these highly desired single enantiomer compounds.

To obtain optimal chiral multiplication, catalysts should strictly differentiate enantiotopic groups or faces of prochiral molecules. For that reason, homogeneous metal complexes are ideal candidates since the catalytic activity can be determined based on the choice of central metal (Cu, Mn, Co, Fe, Cr, etc) whilst reactivity and enantioselectivity can be moderated using the chiral organic ligands coordinated to the metal centre. Ligands with central chirality, axial chirality and planar chirality are all easily tailored in other to fine tune the desired selectivities.

Despite the phenomenal success and wide-spread use of these asymmetric homogeneous catalysts, many key problems associated with the (enantio)selectivity remains unclear, particularly the mode of the highly efficient stereochemical communication between catalyst and substrate and the rationale of tuning the catalytic activity by adjusting the metal-ligand system itself. Therefore over the past number of years, we have sought to investigate specifically the nature of the stereochemical communication between the chiral substrates and asymmetric binding sites in these homogeneous complexes, using a combination of EPR, ENDOR, HYSCORE and DFT. Our initial focus centred on the salen ligand [1,6-bis(2-hydroxyphenyl)-2,5-diazahexa- 1,5-diene], a versatile class of ligand for homogeneous asymmetric catalysis, since it has widely used for a range of asymmetric transformation, including epoxidation, epoxide ring opening, and Diels-Alder reactions. We have found that a range of weak interactions, which are crucial for chiral discrimination, can be identified using EPR techniques. Just like enzymes, which exploit hydrogen bonding between the active site and substrate, together with nonbonded dipole-dipole, electrostatic, and steric interactions, which orient the substrate and stabilize the transition state leading to high levels of stereoselectivity, our recent results have shown that asymmetric complexes behave in a similar fashion by exploiting similar interactions. In this talk, an overview of our recent results in this field will be presented, illustrating how weak outer sphere interactions which can control enantioselectivites, can be successfully probed by EPR.

T1 EPR as a Probe of Spin Density Distribution in Organometallic Radicals with Extended Carbon Chain Ligands

Mark Whiteley*, Neil J. Brown**, Ruth Edge***, Emma C. Fitzgerald*, Hannah N. Lancashire*, David Collison***, Joseph J.W. McDouall* and Paul J. Low**.

*School of Chemistry, University of Manchester, Manchester, M13 9PL, UK **Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK ***EPSRC National Service for EPR Spectroscopy, School of Chemistry, University of Manchester, Manchester, M13 9PL, UK

EPR investigations have been carried out on a series of 17-electron radical cations + [Mo{(C≡C)n-R}(dppe)(η-C7H7)] (dppe = Ph2PCH2CH2PPh2) and related carbon chain z+ bridged bimetallics [{Mo(dppe)(η-C7H7)}2(μ-C≡C-X-C≡C)] (z = 1 or 2).

z+

Ph2 Ph2 P Ph P 2 Mo P P {C C} R Mo C C X C C Mo n Ph P 2 P Ph2 Ph2

The solution, X band EPR spectra of these systems exhibit excellent resolution of hyperfine couplings to 95/97Mo, 31P and 1H of the cycloheptatrienyl ring, consistent with localisation of spin density at the metal centre. However, in selected cases, additional hyperfine couplings are observed providing direct experimental evidence for spin delocalisation onto the carbon chain ligand. The molecular design and experimental techniques employed in these examples will be discussed.

3250 3300 3350 3400 3450 3500 3550 B/G

The X-band solution EPR spectrum of PBE0 spin density (isosurface 0.004 au) + + [Mo(C≡CPh)(dppe)(η-C7H7)] of [Mo(C≡CPh)(dppe)(η-C7H7)]

The results of the EPR work are complemented by DFT calculations, which confirm some delocalisation of spin density onto the unsaturated carbon chain ligand.

T2 EPR Spectroelectrochemistry applied to Main Group Compounds

René T. Boeré*, Tracey L. Roemmele*

* Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, AB Canada, T1K3M4

We present recently developed methodologies directed to the electrochemical generation of free radicals in situ in an electron paramagnetic resonance (EPR) resonant cavity with the goal of characterizing the products of voltammetric processes of main group compounds. There has been a relative paucity of thorough electrochemical studies among main group compounds by comparison with either organic or metal coordination chemistry, a situation that our research group is trying to rectify.

We illustrate the advantages of our methods by demonstrating the characterization of free radicals formed via one-electron transfer at a number of different kinds of main group compounds such as those illustrated in Figure 1. S 0/- 0/- N N S4N4 S2N2 S3N3 R R N N S NN +/0 +/0 R' P P R' R3E (E = P, As) NN

Figure 1.

The design and operation of both ambient temperature and low temperature electrochemical cells for use with standard TE110 cavities will be discussed. Some of the quirks and challenges associated with this technique will also be presented.

References 1. R.T. Boeré and T.L. Roemmele, Coordination Chemistry Reviews, 2000, 210, 369- 445. 2. R.T. Boeré, A.M. Bond, T. Chivers, S.W. Feldberg and T.L. Roemmele, Inorganic Chemistry, 2007, 46, 5569-5607. 3. R.T. Boeré, A.M. Bond, S. Cronin, N.W. Duffy, P. Hazendonk, J.D. Masuda, K. Pollard, T.L. Roemmele, P. Tran and Y. Zhang, New Journal of Chemistry, 2008, 32, 214-231. 4. H.F. Lau, P.C.Y. Ang, V.W.L. Ng, S.L. Kuan, L.Y. Goh, A.S. Borisov, P. Hazendonk, T.L. Roemmele, R.T. Boeré, and R.D. Webster, Inorganic Chemistry, 2008, 47, 632-644.

T3 Cyclodextrin-included nitroxides

Gabriela Ionita*, Victor Chechik**

* Laboratory of Quantum Chemistry and Molecular Structure, Institute of Physical Chemistry “Ilie Murgulescu”, Splaiul Independentei 202, Bucharest, 060021, Romania, E-mail: [email protected] ** Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK, E-mail: [email protected]

EPR spectroscopy is an efficient method of monitoring host-guest interactions in supramolecular systems. EPR has been used to monitor and characterise complexes of cyclodextrins, calixarenes, cucurbiturils and other guests. The sensitivity of EPR to the complex formation relies on the changes in local polarity and the rate of molecular tumbling. In some systems, cw-EPR fails to report on the complex formation; in these cases pulsed methods (e.g., ESEEM) can provide information on complexation.

At room temperature, cw-EPR is often insensitive to the formation of supramolecular complexes between small nitroxides and cyclodextrins. This is largely due to the fast tumbling rate of the whole supramolecular complex on the EPR time scale, which makes it difficult to distinguish between the free and encapsulated nitroxides. At reduced temperatures, however, the tumbling of nitroxide in the bulk solution slows down dramatically as the viscosity of solution increases. At the same time, the tumbling rate of encapsulated nitroxide is reduced much more slowly. Thus, at temperatures near the glass transition temperature of the solvent, the bulk solution is a nearly solid matrix with entrapped cyclodextrin molecules. Inside the cyclodextrin cavities, nitroxides can move relatively freely (Figure 1).

Figure 1. X-band EPR spectra of TEMPO in aqueous glycerol at different β-CD concentrations at 210 K.

The behaviour of supramolecular complexes in vitrified solvents will be compared with that in cross-linked gels.

T4 The dienolic compound PG3, a novel cheletropic trap for nitric oxide EPR detection

Robert Lauricella,* Mathilde Triquigneaux,* Laurence Charles,* Christiane André-Barrès,** and Béatrice Tuccio* * Universités Aix-Marseille I,II & III – CNRS, UMR 6264 : Laboratoire Chimie Provence, Equipe SACS, 13397 Marseille cedex 20, France. ** Université P. Sabatier – CNRS, UMR5068 : Synthèse et Physico-Chimie de Molécules d’Intérêt Biologique, 31062 Toulouse cedex, France.

Nitric oxide is a small gaseous radical involved in a wide range of biological processes, such as neurotransmission, immune defense or blood flow regulation. The lack of a signal for free NO in solution and its short physiological lifetime preclude its direct electron paramagnetic resonance (EPR) observation. Therefore, compounds have been elaborated for NO trapping and subsequent EPR detection of the adduct. In this field, Korth et al.1 have developed o-quinodimethane derivatives as NO cheletropic traps generated by photodecarbonylation of the corresponding 2-indanones. These compounds react with NO to yield cyclic nitroxide adducts. While this team chose to further develop fluorescent NO cheletropic traps, several groups have used EPR to examine the reactivity of NO and NO2 radicals toward conjugated dienes. But all the compounds tested either gave rise to complex mixtures of iminoxyle and aminoxyle radicals after reaction with NO or showed poor thermal stability. Our work is in keeping with the search of new traps for NO EPR detection. We will show that PG3 1 can react 3 with O2 to yield the endoperoxide 2 according to a radical pathway (as observed by 2 spin trapping-EPR studies) ,as well as with NO and NO2 radicals, yielding EPR observable nitroxide 3 and alkoxynitroxide 4-5, respectively.

OH . OH O O O O OH O . O + O2 + NO

2 1 3 O O . O + NO2 O. OH . OH O O O O N N O 4 and/or 5

O O

1. a) H.-G. Korth, K. Ingold, R. Sustmann, H. De Groot, H. Sies, Angew. Chem. Int. Ed. Engl., 1992, 31, 891; b) H.-G. Korth, R. Sustmann, P. Lommes, T. Paul, A. Ernst, H. De Groot, L. Hughes, K. Ingold, J. Am. Chem. Soc., 1994, 116, 2767; c) T. Paul, M. Hassan, H.-G. Korth, R. Sustmann, D. Avila, J. Org. Chem., 1996, 61, 6835. 2. a) F. Najjar, C. André-Barrès, R. Lauricella, L. Gorrichon, B. Tuccio, Tetrahedron Let., 2005, 46, 2117; b) M. Triquigneaux, L. Charles, C. André-Barrès, B. Tuccio, Org. Biomol. Chem., 2010, DOI: 10.1039/B921694D.

T5 DEER measurements of a Cytochrome P450 and Ferredoxin complex to determine the docked structure

A.M. Bowen*, J.E. Lovett*, N. Hoskins*, S. Chamil*, S.G. Bell*, F. Mercuri*, D. Caprotti*, Y. Polyhach**, G. Jeschke**, J. Harmer*, L.L. Wong* and C.R. Timmel*

* Centre for Advanced Electron Spin Resonance, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR. ** ETH Zürich, Laboratorium f. Physikalische Chemie, Wolfgang-Pauli-Str. 10, 8093 Zürich

Cytochrome P450 is an important enzyme for catalytic hydroxylation using molecular oxygen.1 One important step for bacterial P450’s is the electron transfer from ferredoxin to P450, which causes the reduction of O2 to a peroxo-anion. Although crystallographic data are available for the individual proteins, structures of the docked conformations in which electron transfer occurs are not. This work thus aims to provide the first experimental data on P450 recognition.

Ferredoxin contains a reduced Fe2S2 centre in which the two irons are antiferromagnetically coupled to give S=1/2 ground state.2 In order to provide the correct g-matrix orientation for the iron-sulphur cluster density functional calculations have been performed. The heme group in P450 was reduced and capped with CO to give EPR silent low-spin Fe(II). The P450 protein sequence is then selectively mutated to contain additional cysteines and spin labelled at these positions using MTSL. DEER measurements were made between the • Fe2S2 centre and the NO at 5 different pump positions in order to give orientationally selective spectra (see figure).

The data were analyzed by least squares fitting to a grid of simulated DEER spectra to give the separation distance and relative spin-spin orientation.3 From the fitted data, and using positions of the NO• calculated from a rotamer library,4 the relative positions of the two spin labels were calculated. This information has been used to form possible docked structures of the two proteins that will be further refined using molecular dynamics simulations to provide the final model structure of the docked system.

1. S.G. Bell, N. Hoskins et al., Biochem. Biophys. Res. Commun., 2006, 342, 191-196. 2. J-M. Mouesca, L. Noodleman et al., Inorg. Chem.,1995, 34, 4347-4359. 3. J.E. Lovett, A.M. Bowen et al., Phys. Chem. Chem. Phys.,2009, 11, 6840-6848. 4. Y. Polyhach, A. Godt et al., J. Magn. Reson., 2007, 185, 118-129

T6 Molecular structure refinement by direct atomic coordinate fitting to ESR spectra

Matthew Krzystyniak1, Gareth Charnock1, Dmitri Svistunenko2, Ilya Kuprov1

1Oxford e-Research Centre, University of Oxford, UK. 2Department of Biological Sciences, University of Essex, UK.

We report an attempt to streamline ESR structure determination by introducing a direct structure fitting (DSF) procedure, wherein the atomic coordinates are iterated directly against the experimental data (using DFT and spin dynamics simulations to get theoretical ESR spectra directly from atomic coordinates). DSF can be formalized as a minimization condition for the error functional  Ω=Sexp − Sr() +λ Er() , where Sexp and S are experimental and theoretical magnetic resonance spectra, E is molecular energy and λ is a weighting factor regulating the relative importance of molecular energy versus the quality of the spectral fit. S and E depend implicitly on  the nuclear coordinates r and this dependence is used for structure determination. We report several example fits: • Cyanomethyl radical exhibiting isotropic ESR spectrum in solution. Theoretical CH2CN spectrum converges to the experimental one within 37 iterations and yields a structure that is within 0.02 Å RMSD from the DFT energy minimum. • Trifluoromethyl radical exhibiting a powder-averaged ESR spectrum in a noble gas matrix. A good fit is obtained in 28 iterations. The result is a correct (pyramidal) radical structure within 0.22 Å RMSD from the DFT energy minimum. • Tyrosyl radical embedded into a protein matrix in frozen solution. The fitting was performed with respect to the dihedral angle between the phenoxyl ring plane and the side chain. The dihedral angle converged to within 10 degrees of the value extracted from the protein crystal structure in 43 iterations. Our experience so far is that the direct atomic coordinate fitting to the ESR spectra, while computationally intensive, is perfectly feasible and tends to produce reasonably accurate structures.

T7 Coexistence of quantum and classic behaviour in EMR spectra of magnetic nanoparticles and molecular nanomagnets

Lisa Castelli*, M. Fittipaldi*, L. Sorace*, C. Innocenti*, C. Sangregorio*, D. Gatteschi*, P. Ceci**, E. Chiancone**, A. K. Powell *** *La.M.M:, Department of Chemistry and INSTM RU, Università di Firenze, Via della Lastruccia 3-13, 50019, Sesto Fiorentino (FI) (Italy), e-mail: [email protected] **C.N.R. Institute of Molecular Biology and Pathology, University of Rome “Sapienza” ***Institut für Anorganische Chemie der Universität Karlsruhe, Karlsruhe, Germany.

Electron Magnetic Resonance (EMR) is a powerful tool to investigate the magnetic properties of molecular nanomagnets (MNMs) and it provides useful information in the analysis of magnetic nanoparticles (MNPs). These two systems have been usually treated using two different approaches. Indeed, MNMs have been described by quantum mechanics, while MNPs have been generally treated in a classical way. However, it is probable that in the near future the two approaches will merge, since the developments in synthetic techniques are beginning to provide objects of the same size for the two classes of systems. In this context EMR can offer a fundamental contribution to the development of a unified view [1]. For this purpose we have studied two systems belonging to these classes by X- and W-band EMR spectroscopy. An iron(III) cluster made up of 19 metal ions, Fe19, with a brucite-like structure, behaving as a single molecule magnet at very low temperatures [2] has been chosen as representative MNM. For MNPs, we chose magnetite / maghemite nanoparticles mineralized in the Dps protein from the bacterium Listeria innocua [3]. This ferritin-like protein has been chosen because its inner diameter of 4.3 nm leads to the formation of very small MNPs approaching the typical molecular size. Powder spectra analysis pointed out similarities between the two systems. In particular, a forbidden transition can be observed in MNPs spectra, indicating a quantum behaviour in this system. On the other side, Fe19 spectra show a temperature behaviour apparently similar to that of MNPs: a broad band can be observed, which becomes wider and more anisotropic by lowering the temperature. Moreover, a single-crystal W-band study of Fe19 was performed. Although the fine structure is not well resolved in all the spectra, at particular temperatures and orientations, the presence of single transitions within a high spin multiplet can be distinguished. Therefore, this system seems to lie at the borderline between single molecule magnets and MNPs, showing similar properties to both of them. Further investigation on similar compounds will hopefully lead to a more complete comprehension of this dimensional region and help to implement a common method of analysis of the corresponding EMR spectra.

[1] Fittipaldi et al., Phys. Chem. Chem. Phys., 2009, 11, 6555 – 6568 [2] Goodwin et al., J. Chem. Soc., Dalton Trans., 2000, 1835–1840 [3] Ceci et al., Chem. Eur. J. 2010, 16, 709 – 717

T8 CW and pulsed EPR characterization of soluble metal phthalocyanines lacking C–H bonds

Hans Moonsa, Lukasz Lapokb, Sergiu M. Gorunb, Sabine Van Doorslaera a SIBAC Laboratory - Department of Physics, University of Antwerp, Belgium b Department of Chemistry & Environmental Science, New Jersey Institute of Technology, Newark NJ 07102 USA

Perfluoro-isopropyl-substituted perfluorophthalocyanines bearing different metals in 1 2 1 3 the central cavity F64PcM (M = Cu(II), Co(II), VO(II), or Zn(II) ) were extensively studied with different EPR techniques. The bulky substituents induce a non-planar, biconcave architecture relative to that of the planar, unsubstituted perhalogenated metallophthalocyanines. While most phthalocyanines are known to form stacks, leading to observable exchange interactions between the metal sites, X-band CW-EPR spectra of the pure F64PcM powders indicate the existence of isolated metal centers. The electron withdrawing effect of the perfluoroalkyl groups significantly enhances solubility in organic solvents like alcohols through the axial ligation of solvent molecules. This ligation is confirmed by X-band 1H HYSCORE experiments. Detailed X-band CW-EPR, X-band Davies and Mims ENDOR and W-band ESE-detected EPR studies of F64PcM in ethanol allowed the determination of the principal g values and the hyperfine couplings of the metal, 14N and 19F nuclei. Comparison of the g and metal hyperfine values of F64PcM and other PcM complexes in different matrices reveals a dominant effect of the matrix on these EPR parameters, while variations in the ring substituents have only a secondary effect. Surprisingly, for M = Cu(II), natural abundance 13C HYSCORE signals could be 13 observed for a frozen ethanol solution of F64PcCu. DFT computations identified the C nuclei contributing to the HYSCORE spectra as pyrrole carbons. The cobalt(II) complex catalyzes the oxidative formation of carbon-phosphorus double bonds2 and the mechanistic details are investigated with different EPR techniques. For F64PcZn, transient EPR is used to determine the principal g-values and the zero-field splitting.

3D Structure of F64PcM. Blue: nitrogen, yellow: fluor, green: metal, other: carbon.

(1) Gorun, S. M, et al, unpublished results (2) Bench, B. A.et al., Angew. Chem.-Int. Edit. 2002, 41, 750 (3) Bench, B. A. et al., Angew. Chem.-Int. Edit. 2002, 41, 748

T9 Electron spin coherence times of metallofullerenes

Richard M. Brown,1 Yasuhiro Ito,1 Jamie Warner,1 Arzhang Ardavan,2 Hisanori Shinohara,3 G. Andrew. D. Briggs,1 and John J. L. Morton1, 2 1Department of Materials, Oxford University, Oxford OX1 3PH, UK 2CAESR, Clarendon Laboratory, Department of Physics, Oxford University, Oxford OX1 3PU, UK 3Department of Chemistry and Institute for Advanced Research, Nagoya University, Nagoya 464-8602, Japan

The electron spin associated with atomic nitrogen encapsulated in fullerenes (N@C60) has been shown to possess coherence times up to several hundred microseconds [1]. In contrast, metal ions encased in a similar way, termed metallofullerenes, have not shown particularly long coherence times (< 1.5 µs), attributed to the much greater spin density on the fullerene cage [2,3]. However, N@C60 has low production yields and is difficult to purify compared to metallofullerenes. Thus, metallofullerenes could offer substantial benefits, for instance in producing larger spin architectures, if long coherence times were observed [4].

We report T1 and T2 of the metallofullerenes Y, Sc and La@C82 over 5-130 K in various solvents. Analysis of the T1 temperature dependence indicates spin relaxation arising from metal-cage vibrational modes and spin-orbit coupling, which are a function of metal ion mass and charge transfer. The coherence times (T2) of metallofullerenes show interesting variation with temperature and dependence on the solvent matrix (see figure 1). Ultimately, we find T2 to be limited by the nuclear spin environment through spectral diffusion (nuclear spin flip-flops) either directly or via methyl group rotation.

Optimising the environment using a deuterated o-terphenyl solvent, we show T2 times greater than 200 µs for Y, Sc and La@C82 at 5–10 K, over two orders of magnitude longer than reported in literature. The identification of the relevant decoherence mechanisms will help inform the choice of structure for larger fullerene arrays. The remarkably long coherence times now make metallofullerenes of increasing interest for areas in spintronics, quantum computing and as a potential spin label.

6 a) b) 10 d-toluene T1e CD d-o-terphenyl T1e 3 5 10 d-toluene T2e d-o-terphenyl T2e 4 10

3 10 Time (µs) 2 10

1 10

0 10 0 20 40 60 80 100 120 Temperature (K)

FIG. 1: Y@C82 relaxation and coherence times as a function of temperature in a) deuterated toluene and b) deuterated o-terphenyl

For more information see http://arxiv.org/abs/1002.1282

[1] Morton et al., Phys. Rev. B, 2007, 76, 085418 [2] Knorr et al., Appl. Phys. A, 1998, 66, 257264 [3] Okabe et al., Chem. Phys. Lett., 1995, 235, 564-569 [4] Benjamin et al., J Phys. Cond. Mat, 18, S867 (2006)

T10 Surface stabilized inorganic radicals and radical ions

Elio Giamello Dipartimento di Chimica IFM & NIS, University of Torino, Italy

Inorganic radicals have attracted the attention of the scientific community since the early days of radiation chemistry, because high energy irradiation often leads to the formation of radicals. In solid materials, the latter are often trapped in the bulk which makes their experimental investigation relatively easy. The book by Atkins and Symons published in 1967, represents the first thorough analysis of inorganic radicals available in the literature.1 Attention to inorganic radicals further increased with the development of the matrix isolation technique, for trapping, in basically inert matrices and often at low temperatures, a large number of inorganic radicals. A later book by Weltner, “Magnetic Atoms and Molecules” discusses this fascinating domain.2 Although the field of surface-stabilized radicals is certainly more limited, in terms of the number of species isolated and characterised, it is however far richer from the chemical point of view. As a matter of fact, radicals can be stabilized by the surface via specific interactions on one hand and possess a different reactivity towards incoming adsorbates on the other hand. The importance of surface radicals owes much to that of surface phenomena which are involved in numerous fields such as heterogeneous catalysis, photochemistry, electrochemistry and corrosion phenomena, microelectronics, optoelectronics and, in general terms, nano-sciences and technology. While there are many methods to characterize an adsorbate, there are fewer which can give information at the molecular level on the adsorbate-surface system, in terms of interaction and structure. EPR techniques have turned to be most powerful to achieve this goal, providing of course that the adsorbate-surface system be paramagnetic. The present contribution, based on a recent review paper3, intends to describe and classify, using some selected example, the variety of inorganic radicals which are formed at oxide surfaces, emphasizing the importance of the structure-reactivity relationship and adsorbate-surface interaction.

1. Atkins, P. W.; Symons, M. R. C. The Structure of Inorganic Radical; Elsevier: Amsterdam, 1967. 2. Weltner, W.J. Magnetic Atoms and Molecules; Dover Publications Inc.: New York, 1989 3. Chiesa, M; Giamello, E.; Che, M. Chem. Rev. 2010.

T11

- On the formation of O2 radicals by adsorption of O2 on thin MgO films

A. Gonchar1, T. Risse1, H.-J. Freund1, C. di Valentin2, L. Giordano2, G. Pacchioni2

1Fritz-Haber-Institut der MPG, Dep. of Chemical Physics, Faradayweg 4-6, 14195 Berlin 2Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via R. Cozzi, 53 – 20125, Milano, Italy

Understanding the atomistic details of chemical properties on solid surfaces plays an essential role in a variety of technological applications such as coatings or lubrication. Another technologically important field is heterogeneous catalysis. Here we want to address a specific topic associated with the reactivity of oxide supported metal catalyst showing a strong metal support interaction. For those systems the metal particles which are deposited on the oxide support are covered by an ultrathin oxide skin of typically a few layers thickness. It is believed that this thin oxide film to understand the reactivity of the system. To this end, it was theoretically predicted that ultrathin films in the range of a few monolayer in thickness may change the electronic properties of adsorbed species. In particular, charge transfer from the substrate onto adsorbates with appropriate electron affinity.1,2

In this contribution we will focus on the first direct experimental evidences for the formation - of O2 radicals created after adsorption of oxygen molecules from the gas phase onto thin MgO(001)-films. Using EPR spectroscopy it is possible to determine the magnetic parameters of the radicals as well as their orientation with respect to the surface. This allows testing the predictions made by theory concerning the adsorption sites directly. Interesting differences are observed for films exhibiting different amounts of structural defects such as steps, corners, and dislocation lines. The impact of these sites on the properties of adsorbed oxygen molecules will be discussed.

1 Hellman, A.; Klacar, S.; Grönbeck, H. J. Am. Chem. Soc. 2009, 131, 16636. 2 H. Häkinnen (private communications)

T12

Quantum information storage using electron and nuclear spins in silicon

John J. L. Morton,1, 2 Richard M. Brown,3 Stephanie Simmons,3 Hua Wu,3 Brendon W. Lovett,3 Richard E. George,3 Arzhang Ardavan,3 Thomas Schenkel,3 Joel W. Ager,3 Eugene E. Haller,4 Shinichi Tojo,5 Kohei M. Itoh,5 Shyam Shankar,6 Alexei M. Tyryshkin,6 and S. A. Lyon6 1Department of Materials, Oxford University, Oxford OX1 3PH, UK 2CAESR, Clarendon Laboratory, Department of Physics, Oxford University, Oxford OX1 3PU, UK 3Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley CA 94720, USA 4Materials Science Department, University of California, Berkeley, USA 5School of Fundamental Science and Technology, Keio University, Yokohama 223-8522 Japan 6Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA Electron spins associated with donors in silicon have great potential for applications in quantum technologies due to their extremely long coherence times (tens-hundreds of millisec- onds), ability to be manipulated on a short timescale (tens of nanoseconds), and interaction with other degrees of freedom (such as nuclear spins for memory, or charge for readout). We begin by exploring the use of the coupled donor nuclear spin as a robust coherent memory element for the state of the electron spin. We demonstrate the coherent transfer of a superposition state in an electron spin ‘processing’ bit to a nuclear spin ‘memory’, using a combination of microwave and radiofrequency pulses applied to 31P donors in an isotopically pure 28Si crystal. The electron spin state can be stored in the nuclear spin on a timescale that is long compared with the electron decoherence time and then coherently transferred back to the electron spin, thus demonstrating the 31P nuclear spin as a solid-state quantum memory. We have achieved store-recover fidelities of 90%, which we attribute to systematic imperfections in radiofrequency pulses which can be improved through the use of composite pulses. The coherence lifetime of the quantum memory element is studied as a function of donor concentration and temperature, and is found to exceed two seconds at 5.5K. We discuss the extension of these experiments to other donors in silicon. The large number of spins used in these experiments is capable of storing a much larger amount of information if one uses distributed collective modes, as in holography. We demon- strate the storage and retrieval of weak 10 GHz coherent excitations in distributed memories based on donors in silicon. Each excitation is phase encoded by a magnetic field gradient and we have stored up to 100 weak microwave excitations in a spin ensemble and recalled them sequentially. We also demonstrate the storage and retrieval of such multiple excitations into a coupled nuclear spin, for more robust storage.

T13 Pulsed EPR spectroscopy and DFT calculations for “difficult” nuclei

John H. Enemark

University of Arizona, Department of Chemistry and Biochemistry, 1306 E. University Blvd., Tucson, AZ 85721 USA

Application of multi-frequency electron spin echo envelope modulation (ESEEM) techniques provides access to the hyperfine (hfi) and nuclear quadrupole (nqi) parameters of such “difficult” high-spin nuclei as 17O (I = 5/2), 33S (I = 3/2), and 35,37Cl (I = 3/2) in the first and second coordination sphere of the Mo(V) center of sulfite oxidizing enzymes. The structural interpretation of the experimental magnetic resonance parameters is facilitated by extensive density functional theory (DFT) calculations.

Observation of 33S ESEEM in samples reduced with 33S-enriched sulfite provides evidence for a blocked form with bound product (sulfate). For some mutations of sulfite oxidase (SO) this blocked form is a catalytic dead end. However, for most variants of SO and sulfite dehydrogenase (SDH), addition of excess chloride converts the blocked form to the well-known low pH (lpH) form with chloride located in the second coordination sphere (Fig. 1).

ESEEM studies of axial 17O-oxo ligands have been extended to wild-type and mutated SO from several organisms. Additionally, the first reliable hfi and nqi data for an equatorial 17O in SO have been obtained. The dependence of the structural and spectroscopic parameters of these 17O ligands on pH is being explored by DFT calculations.

Fig. 1. Mo centers of the blocked (left) and lpH (right) forms of SO; the “difficult” nuclei investigated by pulsed EPR are in red.

T14 EPR-HYSCORE Study of Quinone Binding in Respiratory Nitrate Reductase: Molecular Basis for the Adaptation to Aerobiosis

Stéphane Grimaldi,1 Rodrigo Arias-Cartin, 2 Sevdalina Lyubenova,3 Pascal Lanciano1, Pierre Ceccaldi, 1 Burkhard Endeward, 3 Thomas Prisner,3 Axel Magalon,2 and Bruno Guigliarelli, 1

1Bioénergétique et Ingénierie des Protéines and 2Laboratoire de Chimie Bactérienne, CNRS & Aix-Marseille Université, 31 chemin J. Aiguier, 13009 Marseille, France 3Institut für Physikalische und Theoretische Chemie, J. W. Goethe Universität, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany

Nitrate reductase A (NarGHI) is a complex respiratory enzyme that is induced in Escherichia coli upon growing the bacterium in anaerobiosis and in the presence of nitrate. This membrane-bound enzyme is associated with Formate dehydrogenase to constitute a redox loop enabling the energetic coupling between transmembrane electron and proton transfers. By shuttling electrons between the two complexes, quinones are key elements of this bioenergetic chain, and it was shown that NarGHI is one of the few respiratory complexes able to function with either menaquinone or ubiquinone, the quinones which are associated to anaerobic or anaerobic growing conditions, respectively. NarGHI is a trimeric complex containing no less than eight metal cofactors (2 b-type hemes, 5 Fe-S clusters and the Mo catalytic cofactor). On the basis of spectroscopic, mutagenesis and cristallographic studies, its structural organisation is well known (1, 2), but due to the absence of quinone in the crystal structure, the number and location of the quinone binding sites were largely debated. By combining EPR spectroscopy and mutagenesis, we have recently shown that a mena-semiquinone (MSQ) radical species can be stabilized in the close vicinity of the heme bD in the NarI membrane subunit. Surprisingly, this radical exhibits the highest stabilization constant so far reported in respiratory enzymes (3, 4). To understand the molecular basis of this unusual stabilization, a multifrequency HYSCORE study was directly undertaken on NarGHI enriched membrane vesicles (5). 14N and 15N hyperfine coupling analysis reveals that MSQ is specifically H-bound to only one nitrogen atom, 14 and the N quadrupolar tensor determination enable to assign this atom to the Nδ atom of the axial histidine heme bD ligand. Moreover, the EPR study of a E. coli mutant deprived of menaquinones showed that ubi-semiquinone (USQ) radicals can be stabilized also in membrane preparations. We demonstrate that 14N HYSCORE enables to distinguish the USQ radicals bound to various membrane bound enzymes, and to identify clearly the USQ species bound to NarGHI. The binding mode of the USQ was determined and provides the first spectroscopic evidence to adress at the molecular level the question of the adaptation of an anaerobic enzyme to oxygenic conditions.

1) Bertero, M. G.; Rothery, R. A.; Palak, M.; Hou, C.; Lim, D.; Blasco, F. et al. Nat Struct Biol 2003, 10, 681. 2) Blasco, F.; Guigliarelli, B.; Magalon, A.; Asso, M.; Giordano, G.; Rothery, R. A. Cell Mol Life Sci 2001, 58, 179. 3) Grimaldi, S.; Lanciano, P.; Bertrand, P.; Blasco, F.; Guigliarelli, B. Biochemistry 2005, 44, 1300-1308. 4) Lanciano, P.; Magalon, A.; Bertrand, P.; Guigliarelli, B.; Grimaldi, S. Biochemistry 2007, 46, 5323-5329. 5) Grimaldi, S.; Arias Cartin, R.; Lanciano, P.; Lyubenova, S.; Endeward, B.; et al., J Biol Chem 2010, 285, 179..

T15 Tuesday 10:10

Understanding the Catalytic Mechanism of Methane Production by Methyl-coenzyme M Reductase with Labeled Substrates and Substrate Analogues

Jeffrey Harmer, Alice Bowen Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR,UK Rudolf K. Thauer, Meike Goenrich Max Planck Institute for Terrestrial Microbiology, Department of Biochemistry, Karl-von-Frisch-Straße, 35043 Marburg, Germany. Bernhard Jaun, Sieglinde Ebner, Markus Reiher Laboratory of Organic/Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland Evert Duin, Na Yang, Mi Wang Department of Chemistry and Biochemistry, Auburn UniVersity, Alabama 36849

Methyl-coenzyme M reductase (MCR) catalyzes the key step of methanogenesis in archaea, namely the reduction of methyl-coenzyme M (CH3-S-CoM) with coenzyme B (HS-CoB) to methane and the heterodisulfide CoM-S-S-CoB: 0’ -1 CH3-S-CoM + HS-CoB  CH4 + CoM-S-S-CoB ΔG = -30 kJ mol (1) Methanogenic archaea are found in strictly anoxic habitats, e.g. wetlands, or the rumen and guts of animals, and they gain the energy necessary for ATP synthesis by producing methane from substrates such as H2/CO2, acetate, formate or methanol. This process is responsible for the largest part of the annual emission (estimated 5·108 tons/y) of this very effective greenhouse gas into the atmosphere. The catalytic mechanism of the I reduction (Eq. 1) at the nickel center (Ni F430) is widely disputed. In this presentation, we will present our latest CW and pulse EPR, pulse ENDOR, and ESEEM measurements at X-, Q- and W-band on a number of labeled substrates (2H/13C/33S/61Ni/1F) and MCR preparations with the aim of identifying and characterizing paramagnetic intermediates and potential analogues of intermediates in the catalytic cycle. These new data will be discussed in terms of our current knowledge of the catalytic cycle.

[1] R. K. Thauer, Microbiology 1998, 144, 2377 [2] S. Ebner, B. Jaun, M. Goenrich, R.K. Thauer, J. Harmer, J. Am. Chem. Soc., in press.

T16 Analysis of magnetic interactions in EPR and ENDOR: an approach to electronic and structural properties of redox centres in enzymes

Reinhard Kappl

Institut für Biophysik, Klinikum, Universität des Saarlandes, 66421 Homburg, FRG

Redox active enzymes are containing one or more redox centers, such as iron-sulphur clusters, necessary to facilitate electron transfer in essential biological processes. Often, these centers are found at distances causing magnetic interactions in their paramagnetic states, which sometimes can be even resolved by conventional EPR. In particular, each paramagnetic center is also interacting with its immediate protein environment, which allows detecting multiple resonances from nearby protons or nitrogens by high resolution techniques (ENDOR, ESEEM).

Because most of the experimental data are derived from disordered systems (powders, frozen solutions of the protein), a detailed analysis of the spectral patterns of proton interactions is quite demanding and complex. We have therefore developed a fast simulation routine for orientation selective ENDOR spectroscopy to deal with the multitude of experimental lines. It takes into account that the centers are generally extended molecular units with asymmetric spin populations and, in addition, superimposed spectra of different centers can be analyzed simultaneously along all available field positions on the EPR spectrum. Since the parameter space is rather large (including g-orientations, spin distributions, isotropic hyperfine interactions and spatial coordinates), the implementation of an automatic calculation routine has proven to be helpful. It analyses the variation of clearly resolved outer resonances by scanning the parameter space for possible solutions assignable to selected protons of a model structure or an available x-ray structure.

Some applications of the methods to an adrenodoxin-like FeS-protein and to the iron clusters of proteins of the Mo-containing hydroxylase family are presented. In this manner the orientations of the g-tensors, the spin populations in the different centers and the sites of the reducible iron in the FeS-clusters could be determined. This kind of information may contribute to a detailed understanding of the electronic and redox properties of such centers. The advantages and limitations of the approach will be discussed.

T17 PELDOR on DNA: Orientations, Dynamics, Bending, Non-Covalent Labelling and Protein Binding

O. Schiemann*, G. W. Reginsson*,§, S.A. Shelke§, D. Margraf#, A. Marko#, T.F. Prisner#, S.T. Sigurdsson§, H. El Mkami&, P. Cruickshank&, R. Hunter&, G.M.Smith&

* University of St Andrews, BMS, Centre of Magnetic Resonance, North Haugh, KY16 9ST St Andrews, UK. § University of Iceland, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland. # University of Frankfurt, Institute of Physical and Theoretical Chemistry, Max-von- Laue Str. 7, 60438 Frankfurt, Germany. & University of St Andrews, School of Physics and Astronomy, Centre of Magnetic Resonance, North Haugh, KY16 9ST St Andrews, UK.

Pulsed Electron Electron Double Resonance (PELDOR) has been established as a very precise and reliable method to measure distances between spin centres. Recently, we have shown that PELDOR enables also determining angles between spin labels as long as they are rigid enough1. We will show that the combination of such labels with PELDOR provides also access to DNA breathing dynamics. To overcome the challenging label synthesis, the next generation of this label makes use of non-covalent binding via hydrogen bridges and stacking interactions. We can show that the specificity and strength of binding is large enough to yield high-quality PELDOR data with modulation. This non-covalent labelling concept proves also successful for the study of protein binding. For example, the DNA bending of the Lac operator DNA upon binding of the Lac repressor protein is clearly resolved in the PELDOR data. In a further class of DNA binding proteins, the helicases, we can resolve its switching between different conformational states induced by binding of ATP, ADP, and DNA. This clearly shows, that PELDOR does not only provide mere distances but access to orientations, dynamics and changes between conformational states of large protein complexes difficult to access otherwise.

1 Olav Schiemann, Pavol Cekan, Dominik Margraf, Thomas F. Prisner, Snorri Th. Sigurdsson “Relative Orientation of Rigid Nitroxides by PELDOR: Beyond Distance Measurements in Nucleic Acids” Angewandte Chemie 2009, 121, 3342-3345.

T18 Extreme Sensitivity and Distance Measurement: PELDOR on Deuterated Proteins

Richard Ward*, Andrew Bowman*, H. El-Mkami**, T. Owen-Hughes*, David G. Norman*

*College of Life Sciences, University of Dundee, Dundee DD1 5EH. **School of Physics & Astronomy, University of St Andrews, St Andrews KY16 9SS

It has been recognised for some time that relaxation to protons in the environment surrounding a spin-label has large effects of Tm and as such on the persistence of any generated spin echo. In PELDOR experiments it is now standard practice to use deuterated solvents and cryo-protectants, since this results in an increased Tm. This has either provided an increase in the sensitivity of the experiment or enabled researchers to investigate longer times, and thus longer distances. Also by going to longer times a true background decay becomes possible, thus the data will yield a more accurate distribution of distances. Even with the use of deuterated solvents it is often impossible to collect data on labelled biomolecules, beyond a modest 5-10µs. This is suitable in many cases but as distance measurements approach 80Å this can prove inadequate.

Studies on simple, shape persistent organic molecules have realised data collections of up to 30µs. It has been postulated that deuteration of biomolecules could increase Tm, however deuteration of this kind has never been published. We report here the increases in Tm that have been obtained using total (and even partial) protein deuteration. We have demonstrated that the gains in Tm and consequent sensitivity are extremely significant. The advantages demonstrated in this work include: extended time measurement in PELDOR for the accurate quantification of very long spin-spin distances, better baseline subtraction, much greater signal to noise ratios with an attendant significant increase in sensitivity.

The gains obtained by protein deuteration essentially extend the distance limit on PELDOR to something in excess of 110Å and the sensitivity is increased to make sub-micromolar concentration PELDOR a practical possibility.

Methods for the introduction of deuterium into bacterially expressed proteins are demonstrated at minimal cost, making this technique applicable to most bacterially expressed proteins.

T19 An EPR study of dehaloperoxidase from Amphitrite ornate – an oxygen storing globin with a peroxidase function

Dimitri A. Svistunenko*, Matthew Thompson**, Stefan Franzen**

*Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK **Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA

The low temperature EPR spectroscopy with employment of a new freeze- quenching machine for rapid freezing of reaction mixtures have been used to study the haem enzyme dehaloperoxidase (DHP) from the marine worm Amphitrite ornate. DHP is an oxygen transporting haemoglobin which is also the first globin identified to possess a biologically relevant peroxidase activity. As a haemoglobin, DHP cycles between the oxy and deoxy states as it reversibly binds oxygen for storage. As a peroxidase, DHP has been shown to rapidly oxidize trihalophenols to dihaloquinones in the presence of hydrogen peroxide.

The samples for the EPR measurements were freeze-quenched variable time after activation of the ferric (resting) enzyme by hydrogen peroxide. Kinetic dependences of two high spin ferric haem forms and of the free radicals associated with the globin part of the enzyme have been measured at three different pH values. Typical of many haem proteins and enzymes, DHP exhibits a rapid loss of the high spin ferric haem EPR signal (g=6) on addition of H2O2. Untypical of globins, the loss can be made almost complete and the yield of the radical formed can reach almost 100% (Compound ES). A strong pH dependence of the lineshape of the free radical EPR spectrum allowed deconvolution of the spectrum into two independent EPR signals. These two signals have been simulated as hydrogen bonded tyrosyl radical EPR spectra. The simulation parameters allowed tentative assignment of the two radicals to two different tyrosine residues on DHP. Thus the principal radical of a high yield was assigned to Tyr34. The other radical best detected at pH5 was suggested to be located on Tyr38. A mechanism of the peroxidase action of DHP and of the switching to the ‘sleeping’ oxygen storing state will be proposed.

In contrast to the long standing view and in line with the recent findings, we support the hypothesis that the main substrate binding site in DHP is not inside the distal pocket but rather on the surface of the enzyme. We further specify that this site might be the very area of Tyr34. The van der Waals sphere of this residue is in direct contact with the haem, yet the phenol ring of Tyr34 is fully solvent exposed.

A finding of this work with important practical implications is that the free radicals in the reaction mixture of DHP and H2O2, when frozen by traditional (slow) method and in a freeze-quench apparatus, exhibit notably different EPR spectra. An explanation of this effect will be given.

T20 BRUKER PRIZE LECTURE

The fidelity of spin trapping with DMPO in biological systems Ronald P. Mason

Laboratory of Pharmacology, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Drive, Research Triangle Park, NC 27709, USA

Unlike direct ESR, the spin trap methodology depends on the absolute fidelity of the spin trap reaction. Two alternative reactions of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) leading to radical adduct artifacts have been discovered and investigated: “inverted spin trapping” and the Forrester-Hepburn nucleophilic mechanisms. These two alternate pathways to radical adducts are a combination of one-electron oxidation and nucleophilic addition in either order. In biological systems, the most serious artifact is due to the Forrester-Hepburn mechanism, which is initiated by the addition of a nucleophile to DMPO. It has recently been demonstrated that (bi)sulfite (hydrated sulfur dioxide) reacts with DMPO via a nonradical, nucleophilic reaction and further proposed • − that DMPO/ SO3 formation in biological systems is an artifact and not the result of spin • − trapping of sulfur trioxide anion radical ( SO3 ). Here, the one-electron oxidation of (bi)sulfite catalyzed by horseradish peroxidase/H2O2 has been reinvestigated by ESR spin trapping with DMPO and oxygen uptake studies to obtain further evidence for the radical reaction mechanism. In the case of ESR experiments, the signal of the • − DMPO/ SO3 radical adduct was detected, and the initial rate of its formation was • − calculated. Support for the radical pathway via SO3 was obtained from the stoichiometry between the amount of consumed molecular oxygen and the amount of • − (bi)sulfite oxidized to DMPO/ SO3 . When DMPO was incubated with (bi)sulfite, oxygen consumption was completely inhibited owing to the efficiency of DMPO trapping. In the absence of DMPO, the initial rate of oxygen and H2O2 consumption was • − determined to be half of the initial rate of DMPO/ SO3 radical adduct formation as determined by ESR, demonstrating that DMPO forms the radical adduct by trapping the • − SO3 exclusively under our experimental conditions.

T21 EPR of Photosystem II

A. W. Rutherford

iBiTEC-S, DSV CEA Saclay, URA 2096 CNRS, 91191 Gif-sur-Yvette, France

Prior to the publication of a refined crystal structure of PhotosystemII (PSII), the water/quinone photo-oxidoreductase, the basic structure of the principle protein subunits, some key amino acids and the cofactors involved in charge separation, water oxidation and quinone reduction had already been established. This was the result of a combination of many lines of research (spectroscopy, biochemistry, molecular biology, modelling etc). A key approach was the use of EPR to compare the paramagnetic forms of the cofactors in PSII with those in the much better characterised purple bacterial reaction centre. Close structural and functional similarities were established. Thus when the crystal structure of purple bacterial reaction centre was determined (the first crystallographic structure from any membrane protein), it constituted a direct structural model for PSII. There followed a period in which the basic structural features, the physical nature of the cofactors, their geometries and positions were all directly determined using sophisticated (mainly EPR-derived) methods. The basic similarities and the significant differences between the two types of photochemical reaction centre were painstakingly established. For a couple of decades then EPR dominated PSII research. This golden age was crowned and ended at the same time when the first refined crystal structure of PSII was determined. This simultaneously validated the hard fought for model and superceded it. Despite the relatively poor resolution of the crystal structures, even the first refined crystallographic model verified the main aspects of the structure and resolved the few lingering ambiguities. This and later models went on provide structural information on the other 2600 or more amino acid side chains, not to mention the vast majority of the dozens of the pigment molecules that are not redox active and the many lipid molecules all of which are invisible to EPR. Today, despite being in an the era of enzymological study within a 3D model, the mechanism of the enzyme remains unknown, with even some of the most basic aspects of its enzymology yet to be determined. Indeed even when it comes to the photochemical part, which has been compared to the bacterial reaction for decades, PSII still has the potential to surprise us. EPR is still up there on the front line of PSII research, no longer as dominant as it was, but still coming up with the goods every now and again. Here we shall look at some of these “goods”, both old and new.

T22 Distance measurements in a WALP23 polypeptide labeled with a nitroxide radical and a lanthanide complex: relaxation enhancement, DEER and cw power saturation

M. Yulikov*, P. Lueders*, T. Kohn*, H. Jaeger**, M. Hemminga**, G. Jeschke*

*Laboratory of Physical Chemistry, ETH Zurich, Wolfgang Pauli Str. 10, 8093 Zurich, Switzerland **Laboratory of Biophysics, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, Netherlands

We use doubly labeled WALP23 transmembrane polypeptide alpha-helix incorporated into a lipid bilayer to compare different approaches for measuring the distance between a nitroxide spin label and a chelate complex of a lanthanide ion. The peptide chain of WALP23 is labelled with a DOTA complex of a La3+, Gd3+ or Dy3+ ion at its N-terminus and with a nitroxide spin-probe at one of the positions 7, 11, 15 or 19. We analyze the enhancement of the longitudinal and transverse relaxation induced by dysprosium and gadolinium, the cw power saturation curves and the Double Electron-Electron Resonance (DEER) between nitroxide and gadolinium. We discuss the efficiency and limitations of these approaches in obtaining the distance information.

3+ The T1 relaxation data measured for Dy labelled samples provide the distances which increase consistently with the change of the position of the nitroxide spin-label. This tendency is also observed in the DEER experiment with detection on gadolinium centre and pump pulse on the nitroxide. Nevertheless at the current level of experiment and analysis there is a discrepancy of the order of 20-30% in the distance measured by the two methods. Still the obtained distances are in line with the expectations for the given positions of nitroxide and lanthanide labels on WALP23.

3+ The T2 relaxation enhancement induced by Dy is also sensitive to the label positions, but the relative change of the relaxivity is less compared to the T1 relaxation enhancement. For the relaxation enhancement induced by Gd3+ a significant effect is also observed. Surprisingly, in this case the relaxation enhancement does not follow the -6 r law, and for the T2 relaxation it is even distance independent. A possible cause of this phenomenon can be the presence of the oxygen dissolved in the lipid bilayer and its interaction with both the gadolinium centre and nitroxide radical.

The analysis of cw power saturation curves also has shown promising results and seems to be applicable to detect distances in the range below approx 3 nm. The advantage of this approach is the possibility to do measurements with a cw EPR spectrometer and at physiologically relevant temperatures. The main disadvantages are the shorter distance limit and the need of an external calibration of the method.

T23 Probing Flexibility in Porphyrin-Based Molecular Wires using DEER

J. E. Lovett*, M. Hoffmann*, A. Cnossen*, A. T. J. Shutter*, H. J. Hogben*, J. E. Warren**, S. I. Pascu***, C. W. M. Kay****, C. R. Timmel*, H. L. Anderson*

*Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, UK **Synchrotron Radiation Source, Daresbury Laboratory, Warrington, UK ***Department of Chemistry, University of Bath, UK ****Institute of Structural and Molecular Biology and London Centre for Nanotechnology, University College London, UK

This presentation will show how DEER was used to probe a series of nitroxide spin- labelled butadiyne-linked zinc porphyrin oligomers to investigate their conformational flexibility.1 These π-conjugated oligomers are also known as molecular wires because of their ability to mediate electron transfer.

The oligomers were found to adopt linear conformations with a distribution of distances following the worm-like chain model, consistent with molecular dynamics simulations. The worm-like chain model was fitted to the DEER time traces by adapting the methods available in DeerAnalysis20062 and a method to approximate the standard deviation of the distance results was developed using χ2 statistics.

Despite measuring in frozen solutions, we found that changing the solvent and therefore the glass transition temperature led to small but measurable changes to the conformational flexibility of the molecules. DEER experiments were also used to show that the oligomers were able to self-assemble to form ladder-like structures in the presence of suitable templates and additionally, despite the apparent inflexibility of the oligomers, they were readily bent around multidentate ligands.

The study demonstrated the scope of DEER for providing structural information in synthetic nanostructures.

1. Lovett et al., JACS, 2009, 131, 13852-13859 2. Jeschke et al., AMR, 2006, 30, 473-498

T24 Time-Resolved High-Field EPR Spectroscopy on Natural Photosynthesis: Primary Electron Transfer Reactions in Photosystem I

Oleg G. Poluektov Chemical Sciences and Engineering Division Argonne National Laboratory Argonne, IL 60439

Natural photosynthesis remains a paradigm for defining the fundamental mechanisms of efficient photochemical energy conversion in molecular-based systems. This process occurs by photoinitiated electron transfer reactions between cofactors embedded in integral membrane reaction center (RC) proteins. Although structures for several photosynthetic RC proteins have been determined and the key features of photosynthetic electron transfer (ET) are broadly understood, important details of how the synergy between the cofactors and the surrounding protein optimizes electron transfer reactions have yet to be resolved. We anticipate that the fundamental understanding of structure-function relationships in biological electron transfer can be extended to provide a benchmark for controlling electron transfer in biomimetic systems. To tackle these problems in both natural and artificial photosynthetic systems, we have developed advanced, time-resolved High-Frequency (HF) EPR techniques that allow us to directly inspect the details of ET reactions. Here I will present our results on the application of these techniques for the study of ET reactions in Photosystem I (PS I).

In the first example I will demonstrate how time-resolved HF EPR of spin- correlated radical pairs in PS I provides direct evidence that ET proceeds along both branches A and B. In the second example the mechanism that determines efficient charge separation and stabilization in the natural photosynthetic RCs will be discussed. In order to clarify this mechanism, detailed data on spin-dynamics in spin-correlated + - radical pairs P700 A1 in PSI have been collected and analyzed. The results reported here will lead to a better understanding of the nature of the primary ET processes in the different types of photosynthetic RC proteins.

This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences, under contract DE-AC02-06CH11357.

T25 Prediction of motional EPR spectra from Molecular Dynamics (MD) simulations

Vasily S. Oganesyan

School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom E-mail: [email protected]

EPR with nitroxide spin labels and probes is a valuable spectroscopic tool for studying structure and dynamics of various molecular systems such as proteins and protein-protein complexes, polymers and liquid crystals, DNA, cell membranes and nanostructures. Analysis of EPR spectra, however, requires full computer simulation. The existing approaches based on stochastic models inevitably require fitting of experimental EPR spectra using adjustable parameters which deprive these methods from predictive powers. For instance, it is not possible to decide a priori which sites of spin label attachment in a protein molecule would be optimal for a particular EPR experiment in terms of orientation and mobility. For example, a flexible spin label in CW EPR experiment would be sensitive to conformational changes, while a rigid one would be most appropriate for a reliable distance measurements by pulsed EPR. Molecular Dynamics (MD) atomistic simulations of complex self-organising molecular systems are emerging as an important tool to improve our understanding of the structural and dynamical properties of these systems. Thus it is desirable to predict EPR spectra directly from MD calculations of real structures. Previously we have reported an effective method for calculation of EPR spectra from a single truncated dynamical trajectory of spin label [1]. It has been shown that an accurate simulation can be achieved from a single MD trajectory until the point when the autocorrelation function of re-orientational motion of spin label has completely relaxed. Our approach has opened the prospect of the simulation of EPR spectra entirely from MD trajectories of real molecular structures with introduced spin probes. Such technique does not only simplify the interpretation and analysis of EPR spectra but also opens the possibility, for example, of “computer engineering” of spin-labelled proteins with the desired properties prior to EPR experiment. Here we present recent examples of successful simulation of multi-frequency EPR spectra directly and completely from MD which show excellent agreement with experiment. They include spin probe introduced within different phases as well as along the phase transition curve of nematic liquid crystal (4-n-pentyl-4’-cyanobiphenyl) [2] and several spin labelled proteins [3]. MD simulations have been carried out at the fully atomistic level. The advantages of using a combined MD-EPR approach for providing a new level of detail in molecular motions and order will be demonstrated. Latest developments in this methodology will be discussed and future perspectives highlighted.

[1] V.S. Oganesyan , J. Magn. Reson., 2007, 188, 196.; [2] V.S. Oganesyan, E. Kuprusevicius, H. Gopee, A. N. Cammidge and M. R. Wilson, Phys. Rev. Lett., 2009, 102, 013005.; [3] E. Kuprusevicius, G.White, A.J. Thomson and V.S. Oganesyan, Faraday Discussions, 2010, accepted

T26 Neuroglobin: a continuing challenge for EPR spectroscopy

M. A. Ezhevskaya1, E. Vinck1, S. Dewilde2, L. Moens2, Y. Polyhach3, E. Bordignon3, I. Garcia-Rubio3, G. Jeschke3 and S. Van Doorslaer1

1 Department of Physics, University of Antwerp, Belgium. 2 Department of Biomedical Sciences, University of Antwerp, Belgium. 3 Laboratory of Physical Chemistry, ETH Zurich, Switzerland.

The human neuroglobin (NGB) was discovered already 10 years ago but its function remains unknown. An important specific feature of NGB is the presence of two cysteine residues on CD loop and D helix (Cys46 and Cys55) able to form a disulfide bridge. It was hypothesized that those cysteines can play a significant role in the affinity of NGB for O2. Molecular dynamics simulation predicted that the CD loop, due to its high mobility, has an influence on structural rearrangement for the ligand binding. Recently it was shown that NGB binds to the Gαβγ protein via the CD corner. Some studies proposed NGB as a part of a signaling chain for the protection against oxidative stress in cells. Although, a crucial role of NGB in neuronal survival was suggested, it could not be convincingly proven. To get closer to unraveling the physiological function of this protein, multiple EPR experiments were carried out in this work. Three cysteine residues have been mutated and labeled each separately on the CD7, D5 and G19 positions. We compared the performance of different EPR methods for distance determination between low-spin Fe3+ and a nitroxyl radical in NGB. For that aim the electron spin echo (ESE), inversion recovery (IR) and double electron-electron resonance (DEER) experiments were performed. The experimentally found distances are confronted with theoretical predictions based on the XRD structure using the rotamer library approach (RLA). The DEER method was found to be superior to the other methods. Moreover, the mobility of the spin label attached to the desired protein sites has been studied by the use of room temperature CW X-band experiments. The obtained correlation times were compared to the theoretical analysis made by RLA. Combined high-field 94 GHz CW EPR and X-band HYSCORE experiments of the spin label were helpful to study the local protein polarity and proticity for studied positions. In addition, CW EPR experiments combined with DMPO spin trapping revealed that NGB is highly resistant to the oxidation by H2O2 via the scavenging effect of the disulfide bridge. Our results bring some corrections to the NGB structural organization in solution in contrast to the XRD crystal structure. The EPR experiments directly indicate a high mobility of the CD loop in solution and propose a critical role of the disulfide bridge in the protection from reactive oxygen species (ROS) attack.

T27 High Performance, High Power, High Bandwidth, Pulsed EPR at 94 GHz

Graham Smith, Paul Cruickshank, Hassane El Mkami, David Bolton, Rob Hunter, Duncan Robertson

School of Physics and Astronomy, University of St Andrews, Fife, Scotland

We describe a high performance 94 GHz pulse ESR instrument operating at kW power levels that offers easy sample handling, low deadtime, sub-ns timing resolution and π/2 pulses as short as 5 ns. Such performance is facilitated by the use of non- resonant sample holders operating in induction-mode, which also permit measurements with extremely large instantaneous bandwidths. We demonstrate large increases in concentration sensitivity relative to commercial X-band and W-band instruments for broad spectra and show experimental set-ups that permit optical excitation and measurements on aqueous samples. We will indicate current developments that are designed to permit larger dynamic range measurements, ENDOR and the use of composite and adiabatic pulses. Examples will be given illustrating improved deadtime performance, orientation selective DEER, and Dynamic Nuclear Polarisation measurements.

T28 Photosensitized formation of free radicals and singlet oxygen by a PD-bacteriochlorophyll derivative

T. Oles*, W. Piedzia*, G. Szewczyk*, T. Sarna*, I. Ashur**, R. Goldschmidt**, I. Inkas**, Y. Salomon*** and A. Scherz**

*Jagiellonian University, Department of Biophysics, Gronostajowa 7, 30-387 Krakow, Poland; The Weizmann Institute of Science, **Department of Plant Sciences, and ***Department of Biological Regulation, Rehovot, Israel

Photodynamic therapy (PDT) is a novel modality for treatment of tumors and some other diseases with light, photosensitizing dyes and molecular oxygen. PDT is based on photosensitized generation of free radicals and/or singlet oxygen, which exert toxic effects on cells of the pathological tissue and its blood supply system leading to selective cell death and removal of the pathological lesion. Singlet oxygen is considered to be the key cytotoxic species involved in PDT; however, its efficient formation requires relatively high concentration of ground state molecular oxygen, which in tumor tissue with a compromised blood supply system is an unlikely condition. An alternative mechanism of PDT-induced cytotoxicity involves formation of free radicals via electron or hydrogen transfer between the photosensitizer in the excited triplet state and the substrate and/or solvent molecules. In this study, we analyzed the ability of a hydrophilic Pd-bacteriopheophorbide derivative (WST11) to photogenerate superoxide anion, hydroxyl radicals and singlet oxygen in selected model systems using EPR- oximetry, ERP-spin trapping, nanosecond laser flash photolysis and time-resolved near- infrared phosphorescence. Although in organic solvents, such as acetonitrile and DMSO, WST11 photogenerated singlet oxygen with high quantum yield, in aqueous media almost no singlet oxygen was formed even in the presence of human or bovine serum albumin (HSA or BSA), which by forming noncovalent complexes with the photosensitizer prevented its aggregation. Aerobic photoexcitation of WST11 in aqueous samples induced rapid degradation of the photosensitizer, which was accompanied by a slow consumption of oxygen and formation of hydroxyl radicals. In the presence of BSA, the rate of oxygen photoconsumption significantly increased and the photosensitizer became substantially less susceptible to photodegradation. NADH enhanced oxygen photoconsumption mediated by WST11 and slowed down its photodegradation. In DMSO, irradiation of WST11 induced rapid oxygen consumption, which was independent of NADH. On the other hand a substantial acceleration of the oxygen photoconsumption by NADH was observed in mixture of 25% H2O/75% DMSO. In such binary solvents, aerobic photoexcitation of WST11 led to the formation of superoxide anion. In conclusion, we have demonstrated that in aqueous media the type I photochemistry of WST11 dominates with the formation of superoxide anion and hydroxyl radicals. Our study also suggests that the WST11/HAS complex may act as a light-activated oxido-reductase that catalyzes electron transfer from the protein matrix to molecular oxygen in the solution, opening the way for new design paradigms of novel sensitizers for the treatment of tumors.

T29 SDSL and EPR spectroscopy applied for structural and functional studies on human guanylate binding protein I

Tobias Vöpel**, Daniel Klose*, Heinz-Jürgen Steinhoff*, Christian Herrmann** and Johann P. Klare*†

* University of Osnabrück, Dept. of Barbarastr. 7, 40976 Osnabrück, Germany **University of Bochum, Phys. Chem. I, Universitätstr. 150, 44780 Bochum, Germany † [email protected]

Guanylate binding proteins (GBP’s, G proteins) comprise a protein family of molecular switches found throughout all three domains of life, being responsible for a wide range of diverse functions. They bind and hydrolyze GTP in the highly conserved G domain common to all GTPases. The human GBP1 (hGBP1) is synthesized to high levels after treatments of cells with interferons. This proteins exhibits an antiviral activity against the vesicular stomatis virus (VSV), has been found to present at elevated levels in the cerebrospinal fluid of patients with bacterial meningitis, and furthermore inhibits cell spreading and migration of endothelial cells [1]. hGBP1 comprises three domains, a large G domain, a small intermediate region and an elongated -helical domain. It has been shown to exhibit different oligomeric states during the hydrolysis reaction, involving monomeric, homodimeric and homotetrameric forms [2,3].

We apply site-directed spin labeling (SDSL), in combination with cw and pulse EPR spectroscopy, namely Double Electron-Electron Resonance (DEER), to investigate the oligomerization state and putative conformational changes taking place upon GTP binding and hydrolysis. The experimental distance distribu- tions are further analyzed utilizing molecular dynamics simulations and a rotamer library approach [4]. Our analysis reveals significant conformational changes taking places upon dimerization of hGBP1 in the GTP bound form, including a complete reorientation of the N- terminal -helix towards the Fig. 1. Model of the dimerization-induced conformational other protomer (Figure 1). changes in the presence of GppNHp as deduced from the EPR analysis.

References [1] Vöpel et al. (2009), FEBS Letters 583, 1923-1927. [2] Prakash et al. (2000), Nature 403, 567-571. [3] Ghosh et al. (2006), Nature 440, 101-104. [4] Jeschke and Polyhach (2007), Phys.Chem.Chem.Phys. 9, 1895-1910.

T30 A novel tool to selectively resolve distances in complex macromolecular structures

J.H. van Wonderen#, D.N. Kostrz*, M.Bawn#, C. Dennison* & F. MacMillan#

#School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK *Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle, UK

At UEA we are applying biophysical spectroscopic techniques to understanding structure function relationships in bio-macromolecular complexes as well as characterising protein protein interactions. Among the techniques we apply is the combination of site directed spin labelling (SDSL) with pulsed EPR especially Pulsed Electron Electron Double Resonance (PELDOR) techniques. Until now the PELDOR technique has been mainly applied to spin-labelled proteins to measure intramolecular distances, however such experiments can also be used to study distances between proteins in weakly and strongly binding protein complexes where other conventional methods (NMR & diffraction techniques) struggle (eg in cognate and non cognate colicin complexes). Further, intrinsic paramagnetic probes eg from metal- containing proteins can also be used making the general applicability of the PELDOR technique quite clear. Here we present some examples of our recent work: studying weakly and strongly interacting protein protein complexes; using intrinsic paramagnetic metal probes and novel approaches to combine PELDOR with techniques to deconvolute complex EPR spectra by using relaxation techniques (REFINE)1 to select distances from a mixture of several distances2.

1. T. Maly, F. MacMillan, K. Zwicker, N. Kashani-Poor, U. Brandt and T. Prisner, Biochemistry, 2004, 43, 3969-3978 2. J.H. van Wonderen, D.N. Kostrz, C. Dennison & F. MacMillan, submitted 2010.

T31 Nano graphites studied by Electron Paramanetic Resonance: an insight on the nature of the signals

Antonio Barbon, Marina Brustolon

University of Padova, Via Loredan 1, 35131 Padova (Italy)

The X-band continuous wave Electron Paramagnetic Resonance (cw EPR) spectrum of bulk graphite is a single band, dysonian in character, connected to the presence of mobile electrons [1].

In graphitic nano-materials the spectrum changes, and new bands appear. Graphitic materials are normally made of layered graphenic sheets but, despite their similarity, the corresponding EPR bands show a large variety of intensities, linewidths and g factors, as reported in many papers. Significant differences can be found in the EPR spectra for materials produced with different methods or heat treated differently. Still a theory that accounts for the EPR bands of graphite with particles below 100 μm is lacking.

We have studied graphites in pieces of few Ångstrom produced by ball milling graphite powder for different times. Cracking of the graphite in small pieces creates a variety of species that can generate EPR signals. In particular we focus our attention to the states produced by cutting graphenic planes along zig-zag edges; the presence of these edges is associated to the presence of a sharp peak in the density-of-states diagram near the Fermi level.

We made a careful analysis of the spectra obtained between 4 and 300 K to distinguish different contributions. The analysis allowed us to make attributions of the observed spectra to the possible states, either localized or delocalized, generated in the so-produced material.

Bibliography

[1] G. Wagoner, Phys. Rev. 118 (1955) 647.

T32 EPR investigation of cationic radicals for organic electronics applications

S. Van Doorslaer*, Y. Ling*, H. Moons*, E. Goovaerts*, F. Blockhuys**, C. Van Alsenoy**

*University of Antwerp, Department of Physics, Universiteitsplein 1, B-2610 Antwerp ** University of Antwerp, Department of Chemistry, Universiteitsplein 1, B-2610 Antwerp

Poly(p-phenylene vinylene)-like (PPV-like) oligomers are found to be promising materials for the use as gas sensors, such as electronic noses. “Sensing” is done via the detection of changes in resistance of the active oligomer layer upon contact with the molecules of interest. However, in order to perform these conductimetric measurements, the PPV-like oligomers need to be oxidized, creating positive cations (polarons). Similarly, PPV-like polymers have found applications in plastic electronics, such as organic solar cells and polaron creation in the polymer component plays a key role as positive charge carrier.

O O SO3Na O O

O O O O

In this work, we present a combination of an X- and W-band CW- and pulsed EPR study and a DFT analysis of a series of oxidized oligomers, such as the material obtained after oxidation of the sodium salt of E,E-2-(3-sulfopropoxy)-5-methoxy-1,4- bis[2-(2,4,6-trimethoxyphenyl)ethenyl]benzene (SPOMTNa, scheme). In order to test the effect of different oxidation methods, the EPR spectra of the polaron obtained via electrochemical oxidation and by chemical I2 doping are compared and are found to differ. The characteristics of the oligomer polarons will be compared in detail to our 1 earlier study on the I2-induced polaron in the MDMO-PPV polymer . A surprising decrease of the maximal observed proton hyperfine coupling is detected upon ageing of the electrochemically treated oligomer samples. DFT models will be presented that can explain the observed experimental changes.

References 1. A Aguirre, P Gast, S. Orlinskii, I Akimoto, EJJ Groenen, H El Mkami, E Goovaerts & S Van Doorslaer; (2008) Phys. Chem. Chem. Phys. 10, 7129-7138.

T33 Electron dynamics in lithium ammonia solutions probed by X- and W-band pulse EPR

Kiminori Maeda*, Mathew T.J. Lodge*, Jeffrey Harmer*, Martin O. Jones*, Peter P. Edwards*

* Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford, OX1 3QR, UK

Lithium-ammonia (Li-NH3) solutions have many remarkable physical properties, e.g. high electric conductivity, a metal to nonmetal transition (MNMT)[1], and are therefore of great interest and thus actively studied by EPR and NMR[2-5]. One of the shortcomings of previous EPR studies is that the translational mobility of the electron (modulation of the magnetic interactions) is faster than the conventional EPR frequency of 9 GHz or lower. Therefore, the EPR spectrum has no structure and the differences between the T1 and T2 times, which can be related to the electron dynamics, were only observed in very limited conditions.

A clear difference between the T1 and T 2 times has been reported by Edwards and Freed et al.[6] for the system of lithium methylamine (Li-MeNH2) solutions using X- band pulse EPR. These results have demonstrated the potential of relaxation time measurements for the analysis of the electron dynamics. However, in Li-NH3 solutions, the motion of the itinerant electrons is so fast that the correlation time approaches to the fast limit ωτ C <<1 at X-band EPR. Therefore, high-field pulse EPR data is essential to analyze the spin relaxation mechanism of itinerant solvated electrons. In the presentation, we present precise T1 and T2 measurements collected at X(9.6 GHz)- and W(93 GHz)-band frequencies over a range of temperatures (223-293 K) on Li-NH3 solutions, and discuss the fundamental electron transfer dynamics.

References: [1] P.P.Edwards, C.N.R.Rao, N.Kumar, A.S. Alexandrov Chem.Phys.Chem. 7, 2015 (2006). [2] P.P. Edwards J. Phys. Chem. 84,1215(1980). [3] V. Pollak J. Chem. Phys. 34,864(1961). [4] R.L. Harris and J.J. Lagowski J.Phys.Chem. 85,856(1981) [5] C.A. Hutchison and D.E. O’Reilly, J. Chem. Phys., 34,1279(1961) [6] C.J. Page, G.L. Millhauser, P.P. Edwards, J.H. Freed, M.J. Sienko J.Phys.Chem. 88, 3785 (1984).

T34 Analytical derivatives of spin dynamics simulations

Ilya Kuprov1, Christopher T. Rodgers2 1Oxford e-Research Centre, University of Oxford, UK. 2Department of Cardiovascular Medicine, University of Oxford, UK.

We report analytical equations for the derivatives of spin dynamics simulations with respect to pulse sequence and spin system parameters (couplings, shieldings, tensor orientations, pulse widths, phase shifts etc). The resulting derivatives may be used in fitting, optimization, performance evaluation and stability analysis of spin dynamics simulations and experiments. Importantly, the derivatives in question often cannot be obtained numerically: modern large-scale simulation algorithms have multiple dynamic cut-offs and tolerances (in orthogonalization, matrix inversion, singular value decomposition and other essential mathematical procedures) meaning that a small perturbation in a parameter may trigger a step change in the simulation result, e.g. inclusion or rejection of a particular vector in the basis. In other words, many algorithms are not numerically differentiable with respect to their parameters. They may also display high levels of numerical noise due to the finite precision of machine arithmetic. Even when they are reasonably accurate, numerical derivatives have a high computational cost in such large- scale simulations: typically between two and four separate simulations per parameter. The equations reported are significantly faster, much more accurate, and, importantly, much more reliable than finite difference approximations. Three methods are offered for the calculation of the derivatives in question • Time co-propagation in Hilbert or Liouville space – the derivative simulation is propagated alongside the main simulation. • Derivative superoperator in Liouville space – a superoperator is generated, which transforms the density matrix into the derivative with respect to the parameter chosen. • Eigensystem differentiation for time-independent Hamiltonians in Hilbert and Liouville space – eigenvalue and eigenvector derivatives are used in a diagonalized representation. The algorithms above have been implemented into the development version of the Spinach library (production version to be released on 1 Oct 2010). Matlab source code is available from the authors upon request.

References I. Kuprov, C.T. Rodgers, J. Chem. Phys. 131 (2009) 234108.

T35 Optimization of Dynamic Nuclear Polarization Experiments in Aqueous Solution at 15 MHz/9.7 GHz for a Shuttle DNP Spectrometer

Maria-Teresa Türke, a Igor Tkach a , Peter Höfer b and Marina Bennati*a

a Max Planck Institute for Biophysical Chemistry, Am Faßberg 11, 37077 Göttingen, Germany. b Bruker Biospin, EPR Division, Rheinstetten, Germany.

Dynamic nuclear polarization is emerging as a potential tool to increase the sensitivity of NMR aiming at the detection of macromolecules in liquid solution. One possibility for such an experimental design is to perform the polarization step between electrons and nuclei at low magnetic fields and then transfer the sample to a higher field for NMR detection. In this case, an independent optimization of the polarizer and detection set ups is required.

We describe the optimization of a polarizer set up at 15 MHz 1H NMR/9.7 GHz EPR frequencies based on commercial hardware.1 The sample consists of the nitroxide radical TEMPONE-D,15N in water, for which the dimensions were systematically decreased to fit the homogeneous B1 region of a dielectric ENDOR resonator. With an available B1 microwave field up to 13 G we observe a maximum DNP enhancement of - 170 at room temperature by irradiating on either one of the EPR lines. The DNP enhancement was saturated at all polarizer concentrations. Pulsed ELDOR experiments revealed that the saturation level of the two hyperfine lines is such that the DNP enhancements are well consistent with the coupling factors derived from NMRD data.2 The application potential of the results is discussed on the base of new experimental results achieved with a 0.35 T/14 T shuttle DNP spectrometer.3,4

[1] M.-T. Türke, I. Tkach, M. Reese, P. Höfer, M. Bennati, Phys. Chem. Chem. Phys., Themed Issue, submitted [2] M. Bennati, C. Luchinat, G. Parigi, M.-T. Türke, Phys. Chem. Chem. Phys., Themed Issue, submitted [3] M. Reese, M.-T. Türke, I. Tkach, G. Parigi, C. Luchinat, T. Marquardsen, A. Tavernier, P. Höfer, F. Engelke, C. Griesinger and M. Bennati, J. Am. Chem. Soc., 2009, 131, 15086-15087. [4] A. Krahn, P. Lottmann, T. Marquardsen, A. Tavernier, M.-T. Türke, M. Reese, A. Leonov, M. Bennati, P. Höfer, F. Engelke, C. Griesinger, Phys. Chem. Chem. Phys., Themed Issue, submitted

T36 Pulse-based electron magnetic resonance spin technology and a chemists’ materials challenge: A few steps towards molecular spin quantum computers and quantum information processing

Takeji Takui

Departments of Chemistry and Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan E-Mail Address: [email protected]

The past decade has witnessed that quantum computers(QCs) and quantum information processing(QIP) have been rapidly emerging in pure and applied sciences. Chemical applications of quantum computing to quantum chemistry are the focus of current topics in the fields [1,2]. Photon-qubit based QIP was practically utilised in Swiss Federal Election in October, 2007. Scalable implementation of qubits is the most intractable issue to be solved for any physical systems pursuing realistic practical QCs/QIP. Building-up of scalable matter qubits is now a materials challenge for scientists from the experimental side. Among matter qubits, molecular electron spin-qubits are the latest arrival, but can afford the promise in implementing scalable QCs/QIP [3-6], as relevant to an electron version of Lloyd model [7,8]. In this presentation, we illustrate how to design and implement electron spin-qubits and nuclear spin-qubits in organic-based molecular frames. They are all synthetic qubits, as well defined in terms of matter spin-qubits in ensemble. The synthetic spin-qubit systems allow us to generate quantum entanglements between the electron spin and proton nuclear spins. For molecular electron spin-qubits, we have synthesised weakly exchange-coupled open-shell entities. We have shown that both pulse-based Electron-Nuclear-DOuble/Multiple Resonance (ENDOR/Multiple) and Electron-Electron DOuble Resonance (ELDOR) techniques serve as the most useful spin-state manipulation technology in implementing QCs/QIP. During our QCs/QIP experiments, we have frequently utilised a Time-Proportional-Phase-Increment (TPPI) method [3,4], as a key technique to characterize the entanglements. Pulse-based electron magnetic resonance spin technology for QCs/QIP experiments gives a promise of further development in electron magnetic resonance spectroscopy [3,4], exemplifying a straightforward detection of the electron spinor via the electron-nuclear spin entanglement. Also, we illustrate our recent applications of pulsed X-/Q-band ESR to supramolecular chemistry and high-spin chemistry, emphasising the characterisation of molecular high-spin clusters in solution by 2D transient nutation or high-power Q-band ELDOR spectroscopy.

References: [1] (a) D. S. Abrams, S. Lloyd, Phys. Rev. Lett. 83, 5162-5165 (1999). [2] (a) A. Aspuru-Guzik et al, Science 309, 1704-1707 (2005). (b) H. Wang et al, Phys. Chem. Chem. Phys. 10, 5388-5393 (2008). (c) I. Kassal, A. Aspuru-Gazik, J. Chem. Phys. 131, 224102-6 (2009). (d) B. P. Lanyon et al, Nature Chem. 2, 106-111 (2010). [3] (a) M. Mehring et al, Phys. Rev. Lett. 90, 153001-4 (2003). (b) M. Mehring et al, Phys. Rev. Lett. 93, 206603/1-4 (2004). (c) M. Mehring et al, Phys. Rev. Lett. 73, 052303/1-12 (2006). [4] (a) R. Rahimi et al, Int. J. Quant. Info. 3, 197-204 (2005). (b) K. Sato et al, J. Mater. Chem. 19, 3739-3754 (2009). (c) K. Sato et al, in Molecular Realizations of Quantum Computing 2007, Vol. 2 (Eds: M. Nakahara et al), World Scientific 2009, pp. 58-162. [5] J. J. L. Morton et al, Nature Physics 2, 40-43(2006). [6] D. Suter, T. S. Mahesh, J. Chem. Phys. 128, 052206-1-14 (2008). [7] S. Lloyd, Sci. Am. 273, 140-145 (1995). [8] Y. Kawano et al, Phys. Rev. A 72, 012301-13 (2005).

T37 EPR Studies of Linked Antiferromagnetic Rings: Towards Quantum Information Processing

Floriana Tuna, Grigore Timco, Laura Carthy, John Machin, David Collison, Eric J. L. McInnes, Richard E. P. Winpenny

School of Chemistry, The University of Manchester, Oxford Road, M13 9PL, UK.

It has been recently proposed that a pair of weakly coupled S = ½ clusters could be used in quantum information processing (QIP) acting as a two-Qubit gate.1 One promising candidate is the family of compounds [R2NH2][Cr7NiF8(Me3CCOO)16- x(RCOO)x] which possess a S = ½ ground state, and a energy gap to the first excited state (S = 3/2) of ca. 13 K.2 These antiferromagnetically (AF) coupled rings possess a number of key properties for the qubit encoding and manipulation, such as: suitable level structure, long decoherence times, robustness with respect to functionalization and deposition on surfaces.

Recently we have found that weak magnetic coupling between two, there or four such rings can be achieved with a high degree of precision by supramolecular chemistry and we accurately estimated this coupling by EPR spectroscopy.3 Here we present two families of weakly coupled Cr7Ni rings that act as prototype molecular qubits. Employing variable temperature multi-frequency (9-95 GHz) EPR spectroscopy, we have been able to resolve the electronic spin structure of these compounds and to quantify not only the isotropic magnetic exchange between rings, but also the magnetic anisotropy parameters of various spin states.

1. F. Meier, J. Levy, D. Loss, Phys. Rev. Lett. 2003, 90, 047901; F. Troiani, M. Affronte, P. Santini, S. Carretta, G. Amoretti, Phys. Rev. Lett. 2005, 94, 190501. 2. M. Affronte, I. Casson, M. Evangelisti, A. Candini, S. Carretta, C. A. Muryn, S. J. Teat, G. A. Timco, W. Wernsdorfer, R. E. P. Winpenny, Angew. Chem. Int. Ed. 2005, 44, 6496. 3. G. A. Timco, S. Carreta, F. Troiani, F. Tuna, E. J. L. McInnes, M. Affronte, R. E. P. Winpenny, et al., Nature Nanotechnology 2009, 4, 173; G. A. Timco et al., Angew. Chem. Int. Ed. 2008, 47, 9681.

T38 Molecular Magnets as Qubits: Extending the Phase Coherence Time

C. J. Wedge*, O. Rival*, J. J. L. Morton*, G. A. Timco**, R. George*, A. Ardavan*, S. J. Blundell*, E. J. L. McInnes** and R. E. P. Winpenny**

*CÆSR, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU **Department of Chemistry, University of Manchester, Manchester, M13 9PL

A computer utilising the coherent superposition of states of quantum bits (qubits) can perform certain calculations such as factorising a number1 or searching a database2 more efficiently than any classical computer. Many varied candidates have been proposed to physically realise the qubit, the electron spin of molecular nanomagnets being one promising avenue of research. The original proposal for the use of molecular magnets in quantum computation focused on homometallic systems such as Fe8 and Mn12Ac which provide a high spin ground state and a number of nondegenerate transitions.3 Here we examine a series of heterometallic Cr7M wheel compounds in which the total spin S may be varied through the choice of the metal M.4 These compounds may be thought of as derived from the diamagnetic Cr8 wheel [Cr8F8(O2CCMe3)16] by substitution of one of the antiferromagnetically coupled Cr3+ ions (s = 3/2) with a divalent metal ion; for 2+ 2+ example, substituting Ni (s = 1) or Mn (s = 5/2) gives Cr7Ni (S = 1/2) or Cr7Mn (S = 1), respectively. In each case, separation of the anionic Cr7M wheel from the neutral Cr8 is achieved by crystallization with an appropriate cation, typically a secondary amine. The great strength of such molecular systems is the flexibility of synthetic chemistry, allowing numerous modifications to tune the properties of the qubits, couple multiple qubits5 or allow binding to metal surfaces.6

For the application of these compounds in quantum information processing, it is critical that the phase coherence time Tm of the qubit is long compared to the timescale of spin manipulations. Previous pulsed EPR studies have shown that for the fully deuterated Cr7Ni wheel Tm is sufficient to allow several hundred spin manipulations and that decoherence pathways in Cr7Ni and Cr7Mn are identical and dominated by dipolar couplings to 1H or 2D nuclei.7 Here electron-spin-echo decay measurements will be presented for several differently substituted Cr7Ni wheels, revealing the impact of varying the identity and deuteration level of the carboxylate ligands and secondary amine on Tm. Such information is essential in building understanding of decoherence pathways in these systems and determining synthetic targets for the next generation of molecular nanomagnet qubits.

1 P. Shor; Proc. 35th Ann. Symp. Foundations of Computer Science (IEEE Computer Society Press) 124, (1994) 2 L. K. Grover; Phys. Rev. Lett., 79, 4709, (1997) 3 M. N. Leuenberger and D. Loss; Nature, 410, 789, (2001) 4 F. K. Larsen, E. J. L. McInnes, et al.; Angew. Chem. Int. Ed., 42(1), 101, (2003) 5 G. A. Timco, S. Carretta, et al.; Nature Nanotechnology, 4, 173 (2009) 6 V. Corradini, F. Moro, et al.; Phys. Rev. B, 79, 144419 (2009) 7 A. Ardavan, O. Rival, et al.; Phys. Rev. Lett., 98, 057201, (2007)

T39 Thursday, 11:00

DNA radical-intermediates in UVA-irradiated DNA-riboflavin/melanin systems?

Rachel M. Haywood,1 Arsen Volkov,1 Christopher W. M. Kay2

1RAFT Institute, Mount Vernon Hospital, Northwood, Middlesex, HA6 2RN, UK.

2Institute of Structural & Molecular Biology and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, UK

Development of melanoma is linked to UV light; however, the contribution of UVA is unclear. UVA causes melanoma in the melanin-pigmented Xiphophorus, but not in the albino non-pigmented mouse transgene, suggesting a possible role for melanin in UVA causation of melanoma. We have used continuous-wave ESR, with and without the spin-trap DMPO, to study the UVA-irradiation of pigmented and non-pigmented melanoma cells (see poster abstract Volkov and Haywood). Stable and spin-trapped carbon- and oxygen radicals have been identified in pigmented cells comparable with radicals detected in DNA associated with melanin. A melanin leakage hypothesis is proposed to explain melanin-photocatalysed DNA damage when melanin associates with cellular DNA. Here we probed reaction mechanisms in UVA-irradiated DNA associated with the photosensitisers melanin and riboflavin. Irradiation of DNA-riboflavin gives a broad singlet (broader than flavin alone). Upon oxygen removal, more than one absorption maximum is apparent (see Figure) and in the absence of DNA no radicals are detected. The g value measured at the peak of the low-field component is 2.0114, and is comparable with a shoulder to melanin in UVA-irradiated DNA-melanin (arrow), and the low-field component of the guanine radical-cation spectrum. UVA irradiation of DNA-riboflavin generates singlet oxygen and superoxide, and damage at guanosine with formation of Fpg sites and DNA single-strand breaks whilst melanin sensitises superoxide and 8-oxo-dG. In addition to the broad singlet, we detect carbon-centred radicals in UVA-irradiated riboflavin and DMPO which are detected in UVA-irradiated melanin. In the absence of O2 we detect spectra characteristic of DNA-sugar radicals in UVA-irradiated DNA-melanin (*). These data are discussed with respect to mechanisms of DNA damage via predominantly singlet oxygen in DNA-riboflavin and superoxide in DNA-melanin. We tentatively conclude that spectra of radicals detected in the absence of DMPO, include DNA radical-intermediates of photosensitised UVA-photodamage to DNA. g = 2.0114

Salmon sperm DNA + riboflavin minus O2

* SK23 DNA + melanin minus O2 (500 s)

Melanin radical

SK23 DNA + melanin UVA minus O2 (750 s)

T40 Investigating a cell signalling protein using PELDOR

R.Ward, A. Plechanovova, R. Hay and D. Norman

College of Life Sciences, University of Dundee, Dundee, DD1 5EH

The cell uses a small ubiquitin-like modifier protein, called SUMO, to regulate many diverse processes including transcription, protein localisation, cell cycle progression, and protein degradation. Proteins can be covalently modified, usually on the terminal amine group of lysine residues, by a single SUMO molecule via a mechanism involving adenosine triphosphate (ATP) and three enzymes called E1, E2 and E3. Initially SUMO is activated by ATP and the E1 enzyme and is then subsequently transferred to the E2 enzyme. At this point the E2 enzyme can directly transfer the SUMO molecule onto another protein. The E3 enzymes catalyse this process and introduce substrate selectivity. SUMO can also be covalently attached to another SUMO protein and thus form polySUMO chains. Recently it has been shown that these polySUMO chains are recognised by an E3 ubiquitin ligase enzyme called Rnf4. Rnf4 catalyses the transfer of ubiquitin onto other proteins. Polyubiquitin chains result in the modified protein being localised at the proteasome, which is where proteins are degraded. Thus it has been demonstrated that polySUMO chains are another signalling mechanism for protein degradation. This novel-signalling molecule has been implicated in a particular cancer therapy and thus is of great interest. Despite this, however, there is no structural data on the polymeric form of SUMO or the complex it forms with Rnf4.

By using the pulsed electron double resonance (PELDOR) methodology and site-directed spin labelling it has been possible to obtain distance distribution data on a dimeric SUMO molecule in the absence and presence of the recognition domain of Rnf4. These preliminary results are discussed in the context of a wider programme of work.

T41 Pulsed EPR studies of the excited triplet state in diethyl fullerene malonate

Vasileia Filidou,1 Steven D. Karlen,1,2, Marcus Schaffry, 1, Erik M. Gauger,1 Simon C. Benjamin,1,3 Harry L. Anderson,2 Arzhang Ardavan,4 G. Andrew D. Briggs,1 Kiminori Maeda,5 Kevin Henbest,5 Feliciano Giustino,1 Brendon W. Lovett,1 and John J. L. Morton1,4

1Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK 2Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK 3Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 4Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU, UK 5Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK

While nuclear spin qubits exhibit long coherence times, they suffer from a poor thermal polarization and weak interaction strength. Optically excited electron spins can help overcome these limitations through polarisation transfer and faster electron spin- mediated interactions. Using pulsed magnetic resonance techniques on a modified fullerenic structure we extract the spin Hamiltonian for the coupled system, and the anisotropic hyperfine tensor which describes the electron-nuclear spin interaction. Moreover the triplet relaxation studies enable us to obtain the initial triplet polarization and the relaxation rates. We also present quantum chemical calculations employing density functional theory to help explain our measurements and aid in the prediction of other systems with suitable properties. Finally we discuss how recent theoretical developments on the entanglement of two nuclear spins through optically active mediators (S=1) may be applied in the fullerene systems we are investigating and in this framework we identify these properties that allow high entangling power gates under optical radiofrequency and microwave pulses.

T42 Uncoupled Spins Spaced by an Insulating Tetraphoshine Unit: A Little D Measured by cw EPR

Kuppuswamy Arumugam,a Mohamed C. Shaw,a Joel T. Mague,a Eckhard Bill,b James P. Donahuea and Stephen Sproulesb

a Department of Chemistry, Tulane University, 6400 Freret Street, New Orleans, LA 70118, USA b Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany

Ligand redox noninnocence is a general possibility for metal complexes with ligands in which lone pair bearing heteroatoms, typically N, O, or S, and in a 1,2-cis disposition. Here, the 1,2,4,5-tetrakis(diphenylphosphino)benzene ligand has been employed as a bridge joining redox active ((MeO-p-C6H4)2C2S2)Pd end groups (Figure 1). Two concurrent one-electron ligand-centred oxidations lead to the generation of two dithiolene π radical monoanionic ligands. The resultant dication is EPR-active, and a “triplet” signal is evidenced in the X-band EPR spectrum. The near-degenerate singlet- triplet ground state stems from the rigid isolation of the two unpaired spins by the tetraphosphine ligand. The very weak coupling seen in the spectrum is simulated by the inclusion of an amazingly small zero-field splitting value of D = –0.0015 cm-1 with negligible rhombicity.

Figure 1

T43 Poster 1

EPR of the Cyanide Adducts of Protoglobin Mutants

Filip Desmet*, Lesley Tillemans**, Alessandra Pesce#, Marco Nardini%, Martino Bolgnesi%, Luc Moens**, Sylvia Dewilde**, Sabine Van Doorslaer*

University of Antwerp, *Departments of Physics and **Biomedical Sciences, Belgium %University of Milano, Department of Biomolecular Sciences and Biotechnology, Italy #University of Genova, Department of Physics, Genova, Italy

Vertebrate hemoglobin and myoglobin are two well known members of the globin- family. These heme-proteins are best known for their O2 transport function, this function is however a fairly recent adaptation. The more ancient functions of members of the globin family, which are found in all kingdoms of life, are related to oxygen sensing and enzymatic activity. Indeed, globin-coupled sensor proteins are found in many bacteria. It has been suggested that a group of single domain globins, the so- called protoglobins, which are found in more primitive organisms, are the evolutionary predecessor of these sensor-proteins, although this point is still being debated. We present here the results of our EPR investigation of the cyanide-bound form of MaPgb, the protoglobin of the bacterium Methanosarcina acetivorans. This protein has a number of unique features that make it stand out from all the other characterised members of the globin family. MaPgb is the only known globin to have a higher affinity for O2 than for CO. The X-ray structure of this protein has revealed a system of two tunnels leading to the ligand binding site at the heme, together with an N-terminal tail of 20 amino-acids that folds back to the heme-cofactor at the centre of the protein. A number of point-mutants of this protein were expressed to investigate the function of this tunnel system. The X-ray structure of the as purified form of the protein showed the presence of an unidentifiable ligand in the heme pocket of the mutants. To remove any doubt about the nature of the distal ligand it was decided to study the cyanide-bound form of the proteins. Cyanide is a very strong ligand of heme proteins in the Fe(III) form. The addition of cyanide to the protein solution is thus an effective way to remove any doubt about the ligation of the protein. The CW-EPR investigation of the cyano-met form of the MaPgb mutants showed low gmax-values (≤ 3) for all of the mutants. This is surprising within the globin family where the cyano-met forms have EPR signals which are typically of the large gmax type. This prompted us to perform pulsed EPR experiments. Various factors such as distortions of the heme plane, deprotonation of the proximal histidine and the orientation of the ligands may affect the anisotropy of the g-values and other parameters of the spin Hamiltonian. We combine our EPR data with the X-ray structures of the various cyanide ligated MaPgb mutants to find the origin of the low g- tensor anisotropy.

P1 Poster 2

Model systems to measure short distances between nitroxide radical and lanthanide complex with cw EPR

T. Kohn*, P. Lueders*, M. Yulikov*, G. Jeschke*

*Laboratory of Physical Chemistry, ETH Zurich, Wolfgang Pauli Str. 10, 8093 Zurich, Switzerland

The analysis of continuous wave (cw) power saturation curves can potentially provide information about the distance between a nitroxide spin label and a lanthanide center. As an example we present cw EPR power saturation data obtained for several samples containing both nitroxide radical species and lanthanide chelate complexes with different average distances between them. The analysis of the experimental data reveals a possibility to measure distances up to approx. 3 nm with this approach if Gd3+ is used as the lanthanide ion. In order to calibrate this method and to study its performance for very short distances, we aim to synthesize molecules with a nitroxide radical attached as close as possible to the lanthanide complex. We use 1,4,7,10-tetraazacyclododecane-1,4,7,10 tetraacetic acid (DOTA) as a chelator and attach amino-TEMPO to one of the carboxy groups via an amide bond. The synthesis is performed in two steps. In the first step the amino-TEMPO is attached to a DOTA derivative with three t-butyl protecting groups, and in the second step the carboxylate groups are deprotected. In a similar way we can also synthesize a DOTA derivative with a thiol-reactive group that can be later attached to a cysteine. Furthermore, it is possible to connect a dye molecule to a second carboxylate group of the DOTA derivative. This would allow for an optical excitation of the lanthanide during the EPR experiment.

P2 Poster 3

Graphical user interface for the construction and visualization of large spin systems

Gareth Charnock, Ilya Kuprov Oxford e-Research Centre, University of Oxford

The task of setting up a large spin system for solid state NMR or EPR simulation is a legendary test of one’s mathematical skill – the need to hand-code the chains of nested time-dependent tensor rotations in half a dozen ad hoc conventions, to work around Euler angle singularities and to visualize interactions that occur in direct products of spin spaces does clearly contribute to the gradual loss of the remaining hair within the community. While the function libraries, command-line and text-input spin dynamics simulation tools for large spin systems are available, the intuitive and convenient point- and-click user graphical interfaces are currently missing. Perhaps more importantly, no standards exist (whether by ISO, IUPAC or even a consensus) on the spin system description format – every program has its own ad hoc specification. The latest IUPAC recommendations only go as far as listing interaction tensor anisotropy conventions, not providing any guidance on placing the resulting numbers in a spin system context. It would be fair to say that setting up a spin system still amounts to hand-coding the associated tensor transformations, imposing a high entry barrier on new researchers in the field. In this communication, we attempt to rectify the situation. We introduce a compact and clean XML-based format for spin system description, which is the result of extensive consultations with the spin dynamics simulation community. The resulting files are human-readable, easy to edit and easy to parse using standard XML libraries. We also describe the prototype of the graphical user interface, which was designed to facilitate the setting up of complicated spin systems and will, in its final form, capable of saving the results as input files for all major spin dynamics simulation packages. In addition to the user interface, a software library will be released aimed at speeding the development of tools for working with spin system specification formats. Feedback on the current prototype program and feature requests from the community would be greatly appreciated. In its present form, the software can import the outputs of major quantum chemistry software (Gaussian, CASTEP etc), interactively create and edit all types of spin interactions and save spin system descriptions for major spin dynamics simulation software (SIMPSON, EasySpin etc).

P3 Poster 4 Anthrax Lethal Factor: Development of an EPR-based binding assay for ligand binding

Micha B. A. Kunze# , Daniel Klose#, Pradeep K. Gupta*, Amit Banerjee§, Steven H. Leppla* , Heinz-Jürgen Steinhoff # #Department of Physics, University of Osnabrück, Barbarastraße 7, 49076 Osnabrück * Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD20892 USA §Department of Pharmaceutical Sciences, College of Pharmacy, Detroit, MI 48201 USA [email protected]

Anthrax Lethal Factor (LF) [1] is a zinc metalloprotease produced by vegetative Bacillus anthracis as one part of the two component lethal toxin. LF is the major virulence factor for anthrax exposing it as the most feasible target to combat this deadly disease [2]. LF cleaves several MAP Kinase Kinases (MAPKK) to exert the lethal effect in several cell types. Our work is aimed at the development of an EPR- based assay to study the mechanisms of inhibition of MAPKK cleavage by possible inhibitors – identified by ligand library screening. Therefore, we applied site-directed spin labeling and continuous wave (cw) or pulse EPR techniques [3]. Two LF double cysteine mutants were modified with methanethiosulfonate spin labels at positions 327 & 727 (in one mutant) and 691 & 734 (in second mutant). Spin label – spin label (SL-SL) distances were obtained by Double Electron- Electron Resonance (DEER) [4] and cw EPR spectra at 10K. Substituting zinc by cobalt facilitates distance measurements between the metal binding site and the nitroxide tips of the spin label side chains by two approaches based on relaxation enhancement (Leigh theory [5]) and dipolar coupling. Using Leigh theory, SL-Co distances were determined from cw EPR spectra at 160 Kelvin. Spectra recorded at 10 Kelvin were fitted with DipFit [6] to determine the SL-Co distances from apparent dipolar broadening. Both approaches show specific observable interaction ranges suggesting a spatial resolution of Co ions, one of which is coordinated at the catalytic core of LF. Elucidation of the binding cleft conformation in the absence and presence of MAPKKs via DEER and cw EPR techniques will provide information about the mechanism of cleavage while corresponding experiments in the presence of inhibitors will reveal possible mechanism of LF inhibition. Such information might lead to the development of more potent inhibitors to be used as drug against anthrax.

References 1. Pannifer et al. (2001) Nature 414, 229-233 2. Nicholas et al. (1998) Science 280, 734-737 3. Bordignon and Steinhoff (2007) Biological Magnetic Resonance 27,129-164 4. Pannier et al. (2000) Macromolecules 33, 7812-7818 5. Leigh (1970) Journal of Chemical Physics 52, 2608-2612 6. Steinhoff et al. (1997) Biophysical Journal 73, 3287-3298 P4 Poster 5

EPR measurements on Arabidopsis thaliana Cryptochrome-1

Ringo Wenzel* Margaret Ahmad** and Robert Bittl*+

*Free University of Berlin, FB Physik, Berlin **University of Paris IV, FRE-CNRS-2846 +Correspondence to [email protected]

Cryptochromes are blue-light sensing photoreceptors found in plants, animals and humans, that share a high degree of structural and sequence homology with photolyases, and contain the same flavine cofactor.[1] Yet, cryptochromes usually do not show a DNA-repair function and their mechanism of action is basically unknown. The function is generally accepted to be a trigger to the circadian rhythm[2] while additional ideas (magnetic sensor in migratory birds, initiation of flowering in plants) are still under discussion. It could be shown, that blue light irradiation leads to an accumulation of the semi- reduced flavin radical state, while the fully oxidized flavin was found to be the dark stable ground state.[3] Nevertheless, the activation process, as well as a possible role of the fully reduced state, is still not known. For measuring the cryptochrome activation, electron paramagnetic resonance (EPR) provides a powerful tool. Since EPR-experiments are sensitive to radicals only, the semi-reduced flavin state can be probed exclusively. Additionally, it can be applied not only to purified protein, but also to whole cells, as shown in [4]. Here, we applied EPR measurements to Arabidopsis Cry1 in overexpressing Sf21 insect cells and purified protein to characterize the radical flavin state and obtain information on the kinetics of flavine photo-activation and dark state recovery, as well as the influence of green and blue-light irradiation on the radical state.

References [1] Malhotra, K., Kim, S. T., Batschauer, A, Dawut, L, Sancar, A. (1995) Biochemistry 34, 6892 [2] A. Sancar (2004) Journal of Biological Chemistry 279, 34079 [3] Banerjee, R., Schleicher, E., Meier, S., Viana, R. M., pokorny, R., Ahmad, M., Bittl, R., Batschauer, A. (2007) Journal of Biological Chemistry 282, 14916 [4] Bouly, J.-P., Schleicher, E., Dionisio-Sese, M., Vandenbussche, F., Van Der Straeten, D., Bakrim, N., Meier, S., Batschauer, A., Galland, P., Bittl, R., Ahmad, M. (2007) Journal of Biological Chemistry 282, 9383

P5 Poster 6 Function of a HAMP domain in bacterial signal transduction investigated by SDSL-EPR

Daniel Klose*, Meike Müller-Trimbusch#,‡, Johann P. Klare*, Heinz-Jürgen Steinhoff*

*University of Osnabrück, Department of Physics, Barbarastr. 7, 49076 Osnabrück, Germany #Groningen Biomolecular Sciences and Biotechnology Institute, Nijenborgh 4, 9747 AG, Groningen, the Netherlands ‡ née Döbber [email protected]

In microbial photo- and chemotaxis a two-component signaling cascade mediates a regulated response of the flagellar motor to environmental conditions. Upon activation, photo- and chemoreceptors transfer a signal across the plasma membrane to activate the histidine kinase CheA. Successive regulation of the CheY-phosphorylation level controls the flagellar motor. In Natronomonas pharaonis a sensory rhodopsin II – transducer complex (SRII/HtrII) mediates negative phototaxis.1 As the initial signal, a light-induced outward movement of receptor helix F leads to a conformational change of transducer helix TM2, which in turn propagates the signal to the adjacent HAMP domain.1,2 The HAMP domain, a widely abundant signaling module, is the pivotal link between the transmembrane and the cytoplasmic domains of the extended transducer. The molecular mechanism underlying its function of intra-molecular signal transmission and putative amplification remains an open question. A suggested mechanism of receptor signal transduction by the HAMP domain exhibits a transition between two distinct conformations (Gear Box Model) based on the NMR structure.3 In contrast, EPR data suggest a two-state equilibrium between a highly dynamic and a compact conformation (d/cHAMP) under physiological conditions.4 To address this discrepancy we applied cw- and pulse-EPR spectroscopy in conjunction with nitroxide spin labeling to obtain distance constraints within the HAMP domain homodimer. The resulting inter spin distance distributions are multimodal indicating the presence of various conformational states. Homology modeling of the distinct HAMP conformations and subsequent application of a rotamer library approach5 allows for a comparison of theoretical and experimental distance distributions. This leads to a further elucidation of the Gear Box Model. Revealing the mechanism of HAMP signaling is a key step to understanding its putative function of signal amplification and integration in signaling networks formed by clusters of interacting receptors.

References

1. Klare, J. P. et al. (2004) FEBS Lett. 564, 219-224 2. Wegener, A. A. et al. (2001) EMBO J. 20, 5312-5319 3. Hulko, M., et al. (2006) Cell 126, 929-940 4. Döbber, M. et al. (2008) J. Biol. Chem. 283, 28691-28701 5. Polyhach, Y. and Jeschke, G. (2007) Phys. Chem. Chem. Phys. 9, 1895-1910 P6 Poster 7

Melanin in natural, bleached & archaeological keratin fibres: EPR & Colourimetric study

Kazim Raza Naqvi a, Liam Regan a, Victor Chechik a, Jennifer Marsh b a Department of Chemistry, University of York, YO10 5DD, York, UK b Proctor & Gamble, Miami valley, Innovation centre, 11810 East Miami River Road, Cincinnati Ohio 45252, USA

Keratin fibres contain melanin pigments which imparts colour to the fibres. Melanin has a strong EPR signal with characteristic line width and shape depending upon the type of melanin (1). The objective of the current study is to investigate the colour changes and degradation of melanin in the archaeological fibres over a long period of time by EPR spectroscopy. This project is aimed at probing whether EPR signature of partially degraded melanin could provide information on the original colour of the fibre.

EPR and colourimetric data were obtained for natural human hair and archaeological sheep wool samples of a wide range of colour shades. For model setup, the chemical degradation of melanin was carried out for natural human hair fibres in an alkaline hydrogen peroxide system and analysed by EPR and colourimetric method.

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Natural Hair Bleached Hair 5G 5G

Degradation of melanin by alkaline hydrogen peroxide reduced the melanin signal intensity along with broadening the line width in EPR with increasing bleaching level. An increase in lightness was observed from the colourimetric data for the same samples. Natural human hair & wool fibres also presented similar trend of decreasing melanin signal intensity and broadening line width moving from darker colour shade to the lighter colour shade.

EPR data for natural and chemically degraded fibres exhibited similar trends, so, EPR cannot be employed to decipher the original colour of the partially degraded fibres.

Reference: 1. Baitimirov, D. R.; Starichenko, D. V.; Pravishkina, T. A.; Konev, S. F.; Shvachko, Y. N., Paramagnetism of melanoprotein fibres. Fibre Chemistry 2006, 38 (6), 506-512.

P7 Poster 8

PELDOR measurements using spin-labelled nucleobase ç that binds non-covalently to guanine opposite an abasic site in DNA

Gunnar.W.Reginsson*,**, Sandip. Shelke**, Biljana Petrovic-Stojanovska*, Christophe Rouillon*, Malcolm White*, Snorri Th. Sigurdsson**, Olav Schiemann*

* Biomolecular Sciences, University of St Andrews, North Haugh, St Andrews, UK ** University of Iceland, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland

Using PELDOR at X-band, we have determined both distances and orientations between two rigid spin-labelled cytosine analogues (ç) that bind non-covalently to guanine opposite an abasic site in DNA.

Numerous biological processes involve the interactions between proteins and nucleic acids. Determining the distance and orientation between DNA domains is therefore an imperative step towards the knowledge of the dynamics and function of such complexes.

We have recently reported the synthesis and application of the rigid spin-labelled nucleotide Ç that base-pairs to guanine and has been covalently incorporated to DNA oligomers (Barhate, Cekan et al. 2007; Schiemann, Cekan et al. 2009).

By using a facile, post synthetic method of spin-labelling nucleic acids with ç, we have determined the distance and relative orientation between two sites on synthetic abasic dsDNA using PELDOR at X-band frequencies. Furthermore, we have demonstrated the applicability of this novel spin label to follow the bending of a synthetic Lac operator.

Barhate, N., P. Cekan, et al. (2007). "A Nucleoside That Contains a Rigid Nitroxide Spin Label : A Fluorophore in Disguise." Angewandte Chemie International Edition 46: 2655-2658.

Schiemann, O., P. Cekan, et al. (2009). "Relative Orientation of Rigid Nitroxides by PELDOR: Beyond Distance Measurements in Nucleic Acids." Angewandte Chemie International Edition 48: 3292-3295.

P8 Poster 9

A combined spin trapping/EPR/mass spectrometry approach to study the formation of a cyclic peroxide by dienolic precursor autoxidation

Mathilde Triquigneaux,a Laurence Charles,a Christiane André-Barrès,b and Béatrice Tuccioa a Universités Aix-Marseille I,II & III – CNRS, UMR 6264 : Laboratoire Chimie Provence, Equipe SACS, 13397 Marseille cedex 20, France. b Université Paul Sabatier – CNRS, UMR5068 : Synthèse et Physico-Chimie de Molécules d’Intérêt Biologique, 31062 Toulouse cedex, France.

G-factors are natural molecules showing antimalarial properties. They can be synthesised by a spontaneous, fast and irreversible addition of triplet oxygen on dienol 3 precursors. PG could thus behave as a radicaloid interacting with O2 in apparent contradiction with the Pauli principle. In the present work, the formation of a radical intermediate derived from PG3 was demonstrated by spin trapping/EPR techniques using the nitrones TN and POBN. The so-formed carbon-centred nitroxides were further identified after complementary experiments performed with 13C-labelled analogues of the substrate. While EPR allowed to specifically and accurately detect radical intermediates, tandem mass spectrometry (ESI-MS/MS) performed in both positive and negative modes, led to the structural characterisation of hydroxylamine derivatives. Therefore, the EPR/MS method appears as an efficient tool to elucidate the mechanism of a spontaneous dienol autoxidation.

M. Triquigneaux, L. Charles, C. André-Barrès and B. Tuccio, Org. Biomol. Chem., 2010, DOI: 10.1039

P9 Poster 10

First Structural Characterisation of a Magnesium Ketyl via EPR, ENDOR and Special TRIPLE Resonance Spectroscopy

C. Jones,* L. E. McDyre,# D. M. Murphy, # A. Stasch* #School of Chemistry, Main Building, Cardiff University, Cardiff, CF10 3AT, UK. *School of Chemistry, Monash University, Melbourne, PO Box 23, Victoria, 3800, Australia.

A thermally stable, crystalline magnesium ketyl complex has been prepared via Mg(I) one-electron reduction of benzophenone. It has been characterised for the first time via cw-EPR, ENDOR and Special TRIPLE Resonance spectroscopies.1 An important application of ketyl radicals is their use as selective reducing agents in organic and organometallic syntheses. These ‘chemical redox agents’ offer many advantages over electrochemical reduction methods, including: no requirement for separation of the electrode product and electrolyte; homogeneous chemical redox reactions generally proceed much more rapidly than electrochemical processes; and low-polarity, relatively non-coordinating solvents such as toluene may be employed, leading to increased chemical stability (compared to that observed in electrolytic solutions with polar solvents).2 Few characterization studies on this type of radical have been carried out, primarily due to the difficulties in isolating them. However we recently developed a stable dimeric Mg(I) compound3 capable of reducing ketones to generate the stable magnesium ketyl radical anion, and herein we report the novel structural information gained by extraction of its spin Hamiltonian parameters using solution ENDOR and Special TRIPLE resonance.

NMe2

Ar N N Ph Mg O N Ph Ar i Ar = C6H3Pr 2-2,6

1. C. Jones, L. McDyre, D. M. Murphy, A. Stasch, Chem. Commun., 2010, 46, 1511. 2. N. G. Connelly, W. E. Geiger, Chem. Rev., 1996, 96, 877. 3. S. P. Green, C. Jones and A. Stasch, Science, 2007, 318, 1754.

P10 Poster 11

Spin Counting and Spin Trapping

C. Albers*, P. Carl*, D. Barr**, R. Weber**, and P. Höfer*

*EPR Division Bruker BioSpin GmbH, 76287 Rheinstetten, Germany **EPR Division Bruker BioSpin Corporation, 44 Manning Road, Billerica, MA 01821- 3931

We have been working for the last few years on a procedure for reference-free spin counting. The basic idea is that it should be possible to calibrate all relevant elements of an EPR spectrometer (cavity, bridge, lock-in amplifier) to convert the final measured signal voltage into the number of spins in the sample. By EPR imaging we have determined the cavity spatial sensitivity profile. We have established the bridge transfer function. Finally, we store all measurement parameters including Q in the data parameter file to enable a reference-free spin number calculation. Today the number of spins can be determined by any user with just a few mouse clicks. A comparison of spectrophotometric analysis and EPR spin counting with a TEMPOL sample (which has a well established molar extinction coefficient at 429 nm) shows an excellent agreement of the two methods.

A challenging application of spin counting is the direct quantitation of spin trapping adducts. For this purpose we have developed a spin trap data base that provides the input data for SolFit, a new spin trap fitting software. The fitting routine disentangles the various spin adducts and calculates the double integral for each individual component. Combined with the spin counting software the double integral is converted into the number of spins (or concentration) for each species. Precise quantitation of spin trapping data is now offered by the combination of the spin counting and SolFit modules.

P11 Poster 12

The Macrocyclic Stabilisation of Unusual Metal Oxidation States: 3+ An EPR, ENDOR and DFT study on [Pt([9]aneS3)2]

Emma Stephen, † Ruth Edge,* Emma Carter,** Alexander J. Blake, David Collison,* E. Stephen Davies, Damien Murphy,** Jonathan McMaster,† Martin Schröder†

University of Nottingham, University Park, Nottingham, NG7 2RD *University of Manchester, EPSRC National EPR Service, Manchester, M13 9PL **University of Cardiff, Park Place, Cardiff, CF10 3AT

† [email protected], [email protected], [email protected]

3+ The [Pt([9]aneS3)2] complex incorporating the first reported 6 co-ordinate Pt(III) centre with macrocyclic thioether donors, has recently been isolated in the solid state and its electronic structure fully elucidated using Electron Paramagnetic Resonance (EPR) and Density Functional Theoretical (DFT) studies.1 (Fig. 1). Variable temperature multi-frequency EPR and double resonance techniques have enabled the identification of 1H hyperfine interactions involving H atoms associated with the macrocyclic backbone.

3+ Our preparation and characterisation of [Pt([9]aneS3)2] represents the first comprehensive study of a Pt(III) centre in a distorted octahedral S6 geometry. EPR 3+ 2 spectroscopic and DFT calculations show that [Pt([9]aneS3)2] possesses a Pt 5dz ground state (30.4%) with significant axial S-character (59.6%) in the SOMO. These results demonstrate the versatility of thioether macrocycles as ligands to stabilise metal centres in highly unusual oxidation states.

2+ 3+ Figure 1. The oxidation of [Pt([9]aneS3)2] to [Pt([9]aneS3)2] ; isosurface plot of the α-spin SOMO 3+ 3+ of [Pt([9]aneS3)2] and the X-band EPR spectrum of [Pt([9]aneS3)2]

1. Emma Stephen, E. Stephen Davies, Alexander J. Blake, Jonathan McMaster and Martin Schröder, Chem. Commun., 2008, 5707-5709.

P12 Poster 13

Double Electron-Electron Resonance measured between gadolinium ion and nitroxide radical

P. Lueders*, M. Yulikov*, A.Godt, ** G. Jeschke*

*Laboratory of Physical Chemistry, ETH Zurich, Wolfgang Pauli Str. 10, 8093 Zurich, Switzerland **Faculty of Chemistry, University of Bielefeld, Universitaetsstr. 25, 33615 Bielefeld, Germany

The four pulse Double Electron-Electron Resonace (DEER) measurements were performed on a chelate complex of Gd with a spin labelled ligand. The ligand molecule is based on a terpyridine fragment with an attached phenlene-ethynylene spacer and a 1- oxyl-2,2,5,5-tetramethylpyrroline-3-yl as a nitroxide label [1]. At X-band the EPR spectrum of Gd is broad which leads to very low inversion efficiency for the pump pulse applied to Gd and observation on the nitroxide. Nevertheless the measurement scheme with the detection on Gd centres and pumping on the nitroxide radicals turns out to be efficient. Short relaxation times of Gd allow for much faster repetition rates in the DEER experiment and at the same time the measurements can be performed at lower temperature, thus providing a higher sensitivity due to the gain in the equilibrium magnetisation of the sample. A much higher transition moment for the Gd centre, allows for a pulse scheme with 10 ns pump pulse and 12 ns (or even shorter) detection pulses at X-band. The differences in the transition moments and the relaxation times provide a possibility to control the two types of paramagnetic species almost independently.

The DEER experiments were performed at 10 K with shot repetition time of 330 µs, which was limited by the duty cycle of the TWT amplifier rather than by the T1 of Gadolinium ion. The Gadolinium-nitroxide distance of 2.57 nm was obtained, which is in a good agreement with the expected structure of the complex.

References 1. E. Narr, A. Godt, G. Jeschke Ang. Chem. Int. Ed. 41 (2002) 3907

P13 Poster 14

EPR detection of unexpected iminoxy radicals reacting reversible dyes and nitric oxide

A. Alberti*, P. Astolfi**, M. Campredon***, L. Greci**, M. Guerra*, D. Macciantelli*, E. Plescia*

* ISOF-CNR, Via P. Gobetti 101, 40129 Bologna, Italy, ** Dipartimento ISAC, Università Politecnica delle Marche, 60131 Ancona, Italy, *** UMR-CNRS 6263, Aix-Marseille Université, 13397 Marseille, France.

The photochromic activity of spiro-compounds stems from the light-induced reversible opening of the pyranic ring. While this process is essentially heterolytic it also has a minor homolytic component, the presence of which has been proved by double-trapping biradical with nitric oxide[1], •NO for a number of spiro[indoline-benzopyrans] and spiro[indoline-naphthoxazines]. Cyclic oxynitroxides (aN ∼ 3.0 mT, g ∼ 2.0045) were thus detected by means of EPR spectroscopy [2].

While extending these studies for mechanistic purposes to other spirocompounds, we found that reacting nitric oxide with spiro[indoline-naphthopyrans] did not afford the three-line EPR spectra typical of oxynitroxides but six-line spectra characterized by a fairly large hydrogen coupling constant (aN ∼ 3.0 mT, aH ≥ 2.0 mT, g ∼ 2.0043). The spectral parameters measured for some radicals suggest that these species are open- chain iminoxyls [3].

DFT calculations predict for the hypothesized radicals hfs constants in fairly good agreement with experiments.

[1] P. Maruthamuthu, J. C. Scaiano, J. Phys. Chem. 1978, 2 : 1588-1591. [2] M. Campredon, A. Samat, R. Guglielmetti, A. Alberti, Gazzetta Chim. It., 1993, 123: 261-264. [3] A. Alberti, P. Astolfi, M. Campredon, L. Greci, M. Guerra, D. Macciantelli, E. Plescia. Magn. Reson. Chem., 2010, 48: 25-37.

P14 Poster 15

Orientation effects in copper phthalocyanine films studied by EPR Spectroscopy

Solveig Felton,1 Marc Warner,2 Soumaya Mauthoor,1 Julie Gardener,1,* Daniel Klose3, Salahud Din,1 Gavin Morley,2 Wei Wu,2 Andrew J. Fisher,2 Gabriel Aeppli,2 Christopher W. M. Kay3 and Sandrine Heutz1

1Department of Materials and London Centre for Nanotechnology, Imperial College London, London, SW7 2AZ, UK 2Department of Physics and Astronomy and London Centre for Nanotechnology, University College London, London, WC1H 0AH, UK 3Institute of Structural & Molecular Biology and London Centre for Nanotechnology, University College London, London, WC1E 6BT, UK *current address: Physics Department, Harvard University, Cambridge, MA 02138 USA

Organic semiconductors have already found commercial applications in for example displays with organic light-emitting diodes (OLEDs) and great advances are also being made in other areas, such as organic field-effect transistors and organic solar cells [1]. The organic semiconductor group of materials based on metallo-phthalocyanines (MPcs) is interesting for applications such as large area solar cells due to their optoelectronic properties coupled with the possibility of easily and cheaply fabricating thin films of MPcs [1, 2].

Many of the properties of organic semiconductors, such as magnetism, light absorption and charge transport, show orientational anisotropy [2, 3]. To maximise the efficiency of a device based on these materials it is therefore important to study the molecular orientation in films and to assess the influence of different growth conditions and substrate treatments. X-ray diffraction is a well established and powerful technique for studying texture (and hence molecular orientation) in crystalline materials, but it cannot provide any information about amorphous or nanocrystalline films. In this paper we present a continuous-wave X-band EPR study using the anisotropy of the EPR spectrum of CuPc [4] to determine the orientation effects in different types of CuPc films. From these measurements we gain insight into the molecular arrangement of films of CuPc mixed with the isomorphous H2Pc and with C60 in films similar to real solar cells.

Acknowledgement We thank the EPSRC for financial support through the Basic Technology Programme.

References [1] S. Heutz, P. Sullivan, B.M. Sanderson, S.M. Schultes, T.S. Jones, Solar Energy Materials & Solar Cells, 83, 229-245 (2004) [2] C.D. Dimitrakopoulos, and P.R.L. Malenfant, Advanced Materials, 14, 99-117, (2009) [3] S. Heutz, C. Mitra, W. Wu, A.J. Fisher, A. Kerridge, M. Stoneham, T.H. Harder, J. Gardener, H.-H. Tseng, T.S. Jones, C. Renner and G. Aeppli, Advanced Materials, 19, 3618-3622 (2007) [4] C. Finazzo, C. Calle, S. Stoll, S. Van Doorslaer and A. Schweiger, Physical Chemistry Chemical Physics, 8, 1942-1953 (2006)

P15 Poster 16

Electron spin coherence times of metallofullerenes

Richard M. Brown*, Yasuhiro Ito*, Jamie Warner*, Arzhang Ardavan**, Hisanori Shinohara***, G. Andrew. D. Briggs* and John J. L. Morton*, **

*Department of Materials, Oxford University, Oxford OX1 3PH, UK **CAESR, Clarendon Laboratory, Department of Physics, Oxford University, Oxford OX1 3PU, UK ***Department of Chemistry and Institute for Advanced Research, Nagoya University, Nagoya 464-8602, Japan

The electron spin associated with atomic nitrogen encapsulated in fullerenes (N@C60) has been shown to possess coherence times up to several hundred microseconds [1]. In contrast, metal ions encased in a similar way, termed metallofullerenes, have not shown particularly long coherence times (<1.5 µs), attributed to the much greater spin density on the fullerene cage [2,3]. However, N@C60 has low production yields and is difficult to purify compared to metallofullerenes. Thus, metallofullerenes could offer substantial benefits, for instance in producing larger spin architectures, if long coherence times were observed [4].

We report T1 and T2 of the metallofullerenes Y, Sc and La@C82 over 5-130 K in various solvents. Analysis of the T1 temperature dependence indicates spin relaxation arising from metal-cage vibrational modes and spin-orbit coupling, which are a function of metal ion mass and charge transfer. The coherence times (T2) of metallofullerenes show interesting variation with temperature and dependence on the solvent matrix. Ultimately, we find T2 to be limited by the nuclear spin environment through spectral diffusion (nuclear spin flip-flops) either directly or via methyl group rotation.

Optimising the environment using a deuterated o-terphenyl solvent, we show T2 times greater than 200 µs for Y, Sc and La@C82 at 5-10 K, over two orders of magnitude longer than reported in literature. The identification of the relevant decoherence mechanisms will help inform the choice of structure for larger fullerene arrays. The remarkably long coherence times now make metallofullerenes of increasing interest for areas in spintronics, quantum computing and as a potential spin label.

For more information see http://arxiv.org/abs/1002.1282

[1] Morton et al., Phys. Rev. B, 2007, 76, 085418 [2] Knorr et al., Appl. Phys. A, 1998, 66, 257–264 [3] Okabe et al., Chem. Phys. Lett., 1995, 235, 564-569 [4] Benjamin et al., J Phys. Cond. Mat, 18, S867 (2006)

P16 Poster 17

On the state of ZFS in DFT and ab initio methods

Simon Bennie

University of Manchester, Oxford Road, Manchester, UK, M13 9PL

The current ability of density functional theory (DFT) to predict zero-field splitting (ZFS) has been investigated through comparisons of the axiality (D) and rhombicity (E/D) parameters with experimental data. We have studied the influence of the exchange- correlation functional, basis set and the presence of relativistic corrections, and found that reasonable predictions of the magnitude of D are obtained with GGA functionals. However GGAs give poor predictions of E/D. Conversely hybrid functionals can predict reasonable values for E/D but produce poor estimates of D. We have also looked at ab initio MRCI approaches and have investigated the influence of starting orbitals and other technical factors.

P17 Poster 18

Water Soluble, Nitroxide-Coated Gold Nanoparticles as MRI Contrast Agents

Muhammad Warsi & Victor Chechik

Chemistry Department, University of York, Heslington, YORK, U.K. YO10 5DD

MRI is a powerful diagnostic technique used in modern biomedical research. The use of contrast agents further enhanced its success by changing the signal intensities of surrounding protons [1]. The use of nitroxides as contrast agents is somewhat hampered by their limited stability in the presence of reducing agents [2]. On the other hand, high reactivity of nitroxides can be exploited to measure the redox status of tissues. Here, we report on the preparation of nitroxide-coated Au nanoparticles as model redox-active contrast agents. Attachment of many nitroxide groups to the nanoparticle surface leads to increased sensitivity and relaxivity [3]. The nitroxide-coated nanoparticles were prepared by a ligand exchange reaction as shown in scheme below. The presence of –COOH groups rendered them water soluble. The nanoparticles were characterised by EPR and relaxivity (R1) measurements.

N O NH

O O S O N OH Au PPh3 Au S Au S O O S O NH O 10 G N O

Figure 1: Synthesis and X-band EPR spectrum of nitroxide-coated Au nanoparticles.

References: 1. P. Caravan, Chem. Soc. Rev., 2006, 35, 512-523. 2. Z. Zhelev, R. Baklova, I. Aoki, K. Matsumoto, V. Gadjeva and K. Anzai, Chem. Commun, 2009, 53-55. 3. M.F. Warsi, R. W. Adams, S. B. Duckette & V. Chechik, Chem. Commun, 2010, 46, 451-453.

P18 Poster 19

Synthetic, structural and electronic investigations of the alkynyl ’ n+ cyclopentadienyl molybdenum complexes [Mo(C≡CR)(CO)(L2)Cp ] (n = 0 or 1; R = Ph or C6H4-4-Me, L2 = Ph2PCH2CH2PPh2 or 2PMe3, Cp’ = Cp or Cp*).

Hannah N. Lancashire*, Ross Lewin*, Neil J. Brown**, Ruth Edge***, David Collison***, Paul J. Low**and Mark Whiteley*,

*School of Chemistry, University of Manchester, Manchester, M13 9PL, UK **Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK ***EPSRC National Service for EPR Spectroscopy, School of Chemistry, University of Manchester, Manchester, M13 9PL, UK

DFT calculations carried out on cis-[Mo(C≡C-Ph)(dppe)(CO)Cp] and trans-[Mo(C≡C- 2 Ph)(PMe3)2(CO)Cp] reveal that the HOMO’s feature metal dxy and dz character respectively. The molecular geometry of the complexes (cis vs. trans) significantly affects the electronic structure and properties of these systems. EPR investigations have been carried out on a series of 17-electron radical cations [Mo(X’)(CO)(dppe)Cp’]+ and + [Mo(X’)(CO)(PMe3)2Cp’] (X’ = halide or C≡CR, Cp’ = Cp or Cp*) to probe the spin delocalisation distribution between the metal and supporting ligands in these cis and trans complexes.

cis-[Mo(C≡C-Ph)(dppe)(CO)Cp] trans-[Mo(C≡C-Ph)(PMe3)2(CO)Cp]

3250 3300 3350 3400 3450 3500 3250 3300 3350 3400 3450 3500 X-band solution EPR spectrum of X-band solution EPR spectrum of + + [Mo(C≡C-C6H4-4-Me)(dppe)(CO)Cp] [Mo(C≡C-Ph)(PMe3)2(CO)Cp]

P19 Poster 20

Melanin-dependent UVA-induced radical damage in melanoma cells: correlation with DNA damage and influence of cell growth/nutritional state

A. Volkov1, M.A. Birch-Machin2 and R. M. Haywood1 1 RAFT Institute, Leopold Muller Building, Mount Vernon Hospital, Northwood, Middlesex, HA6 2RN 2 Dermatological Sciences, Institute of Cellular Medicine, The Medical School, Newcastle University NE2 4HH

Skin cancer is the most common UK cancer, and melanoma, the more aggressive and most common cancer in young people has more than 14000 cases diagnosed annually. Development of melanoma is linked to UV light exposure; however, the contributions of UVA are less clear. UVA causes melanoma in the melanin pigmented Xiphophorus, but not in the albino non-pigmented mouse transgene suggesting a possible role for melanin pigment. In this study we used continuous wave ESR, with and without the spin trap DMPO, to study the effects of UVA-irradiation on free-radical reactions in pigmented and non-pigmented melanoma cells. Without DMPO we detected a shoulder to the ESR spectrum of the intrinsic melanin radical, which was dependent on the presence of cell melanin since no detectable amounts were present in non-pigmented cells. The shape of the shoulder was found to be dependent on the presence of fresh medium suggesting dependence on cell growth and /or nutritional state. Carbon-centred, hydroxyl and hydrogen radical-adducts were detected in the pigmented cells irradiated with UVA in the presence of spin-trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Similar radicals were detected in non-pigmented cells but in lower amounts. As observed with the stable radicals, the types of radicals detected depended on media supplementation. Analyses of the ESR spectra of irradiated melanoma cells in the presence of DMPO were most comparable to UVA irradiated DNA /melanin at pH7.4. We have also shown a reduction of the amount of carbon-centred spin adducts in UVA- irradiated DNA/melanin solution in the absence of oxygen. The presented data provides additional evidence for UVA- damage to DNA and suggests that melanin is pivotal in this damage acting as a catalyst in DNA photo-oxidation. Our data also shows novel effects of cell growth and/or nutritional state on UVA- damage susceptibility, which is important for better understanding of the mechanisms of melanoma development.

P20 Poster 21

Development of Optical Spin-Resonance Methods with Advanced Light Sources

N.R.J. Poolton*, B.M. Towlson**, B. Hamilton**, E.J.L. McInnes***, D.A. Evans* * Institute of Maths & Physics, Aberystwyth University, Penglais, Aberystwyth, Ceredigion SY23 3BZ. ** Photon Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL. *** School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL.

The optical and electronic properties of semiconductors and insulators are strongly dependent on the presence of defects contained within them, and their study has profound influence on the development of new optoelectronic materials. Electron spin resonance (ESR) measurements are particularly valuable in determining the electronic and structural properties of the defects, but coupling of photon excitation/detection capabilities within the ESR experiment provides extremely valuable additional information. Two traditional generic methods have been deployed in this respect: (i) Monitoring of the ESR defect signals during illumination with tuneable light sources provides addi- tional optical parameters of the defects concerned, such as trap depth and the location of excited states (essentially a marriage of optical absorption experiments and ESR); (ii) Where the luminescence of a material is spin dependent (e.g. in donor-acceptor pair recom- bination), ESR signals can be carried by this luminescence (Optical Detection of Magnetic Resonance, ODMR), providing direct and unequivocal attribution of particular defects with specific luminescence emission processes. ODMR has proved particularly successful in understanding the link between defects and luminescence in semiconductors of moderate band-gap energies (Eg<~3eV) where suitable laboratory light excitation sources are widely available. In contrast, virtually no comparable work has been undertaken on wider-gap materials such as Boron Nitride and Aluminium Nitride (Eg~6eV), yet these classes of materials are potentially of great future importance in developing UV optoelectronic devices. The main obstacle to such studies is in the provision of suitable high-energy lab-based light excitation sources. However, appropriate excitation sources, such as synchrotron light sources and more complex laser systems (both optical and free electron) are available, but making use of them requires that the specialised detection equipment be transported to the excitation source, rather than vice versa. Using standard ESR magnet systems, this is logistically im- practical. In the case of synchrotron radiation, the possibility of combining both ODMR and the associated Optical Detection of X-ray Absorption (ODXAS) is particularly attractive, since this combined measurement method would enable a direct link between the optical emission properties of a sample, and the structure of both the lattice and the defects con- tained within it. Here we present a newly developed system, ODESSA (Optical Detection and Excitation of Spin Systems at Advanced-light-sources), for just such a combination of measurements – ESR, ODMR, and ODXAS – based around a compact high-field magnet and portable enough to be deployed at advanced light sources internationally.

P21 Poster 22

Role of the flexible chaperon protein NarJ in the biogenesis of nitrate reductase: structural analysis by EPR and site-directed spin labeling

Magali Lorenzi a, Guillaume Gerbaud a, Léa Sylvi b, Marine Mure b, Axel Magalon b, Hervé Vezin c, Valérie Belle a and Bruno Guigliarelli a

a Bioénergétique et Ingénierie des Protéines and b Laboratoire de Chimie Bactérienne, CNRS & Aix-Marseille Université, 31 chemin J. Aiguier, 13009 Marseille, France c Laboratoire de Chimie Organique et Macromoléculaire, Université de Lille I, Villeneuve d’Ascq, France.

Nitrate reductase A from Escherichia coli is a respiratory enzyme induced upon growing in anerobiosis and in the presence of nitrate. This membrane-bound complex is composed of three subunits containing eight metal cofactor: NarG, the catalytic subunit with the Mo-cofactor and a FeS cluster; NarH, the electron transfer subunit binding four Fe-S centers; NarI, the membrane-bound subunit carrying two b-type hemes. The biogenesis of this Mo-enzyme is a complex process in which the role of the chaperon protein NarJ appears to be essential [1]. NarJ is a protein of 236 aminoacids showing a high flexibility which precludes structural analysis through NMR and crystallography. To overcome this limitation, we have investigated the biogenesis process by using EPR and site-directed spin labeling study of the partner proteins [2].

Thanks to the peculiar EPR signal given by the S=3/2 spin state of the FeS center of NarG [3], we showed that it is possible to monitor both the insertion of this Fe-S cluster and of the Mo-cofactor, and we demonstrated that NarJ triggers the sequential insertion of the two centers within the catalytic subunit [4]. Moreover, NarJ controls the association of the NarGH complex to the membrane-bound NarI subunit leading to a correct heme insertion [4]. This control is thought to result from a tight association of NarJ with a N-terminal peptide of NarG. Four aminoacids positions of NarJ were investigated to graft spin labels, and the interaction sites of NarJ with a model peptide mimicking the N-terminal region of NarG were analyzed by EPR in physiological conditions. In addition, double-labeled mutant were prepared to study the conformational changes of NarJ upon binding to the model peptide by analysing the spin-spin interactions. Our results confirm the flexibility of NarJ and reveal that important structural transitions undergone by the chaperone protein are involved in the biogenesis process.

[1] A. Vergnes, J. Pommier, R. Toci, F. Blasco, G. Giordano, A. Magalon, J. Biol. Chem. 2006, 281, 2170. [2] V. Belle, S. Rouger, S. Costanzo, E. Liquière, J. Strancar, B. Guigliarelli, A. Fournel, S. Longhi, Proteins 2008, 73, 973-988. [3] Lanciano P, Savoyant A, Grimaldi S, Magalon A, Guigliarelli B, Bertrand P. J Phys Chem B. 2007, 111, 13632-7. [4] Lanciano P, Vergnes A, Grimaldi S, Guigliarelli B, Magalon A. J Biol Chem. 2007, 282, 17468-74.

P22 Poster 23

A new electrode system for variable temperature in situ high field EPR-spectroelectrochemistry in capillary tubes

Ruth Edge,* Paul Murray,** David Collison,* Bryan Flynn,*** Katie Jamieson,** Eric McInnes,* Alan Murray,*** Daniel Sells,* Tom Stevenson,*** Abi Wilson,** Joanna Wolowska,* Lesley Yellowlees**

*School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK ** School of Chemistry, University of Edinburgh, Joseph Black Building, King`s Buildings, West Mains Road, Edinburgh, EH9 3JJ, UK ***University of Edinburgh, School of Engineering, Mayfield Road, Edinburgh, EH9 3JL, UK

Combining electrochemistry (oxidation/reduction) with EPR spectroscopy is useful for the study of compounds where chemical production is not possible or when the compounds are unstable, e.g. short-lived free radicals. Until recently a flat cell has been employed with a working electrode of Pt gauze, a counter electrode of Pt wire and a AgCl/Ag reference electrode (at the top of the cell) isolated from the working electrode by a sintered frit.

Developing a system to combine high field EPR spectroscopy and electrochemistry was challenging because of the small dimensions of the resonant cavities. The electrode system has been miniaturized to fit into either Q-band or W-band tubes, which have inside diameters of 1.0 and 0.7 mm, respectively. This has been achieved using PTFE coated platinum wires for both the working and counter electrodes and a PTFE silver wire as the pseudoreference electrode. The wires are all cut to different lengths and the PTFE removed at the bottom of each wire to allow contact with the solution, but so that no bare wires can touch.

The system has been tested at X-band, Q-band and W- band both at room and low temperatures using one- electron reduced nitrated 2,2’-bipyridine ligands and platinum complexes generated in situ from the neutral parent species. These spectra are comparable with those previously recorded in the flat cell at X-band.

We thank EPSRC for their support of the National Service for cw EPR Spectroscopy.

P23 Poster 24

EPR Oximetry study of the thermal polymerisation of acrylates and methacrylates

* * ** ** * Thomas Newby , Ben Booth, Peter Price , Colin Loyns , Victor Chechik,

*Department of Chemistry, University of York, Heslington, YO10 5DD **Nufarm UK Limited, Wyke Lane, Wyke, Bradford, BD129EJ

The self polymerisation of acrylates and methacrylates has been studied by EPR oximetry experiments. Our aim was to understand the role of oxygen in the thermal polymerisation, and to establish whether it acted as polymerisation inhibitor or took part in auto-oxidation of the monomers.

For the oximetry experiment, the samples of the monomer and TEMPO (100 ppm) were sealed in a glass capillary and heated in the EPR cavity. EPR spectra revealed progressive sharpening of the TEMPO peaks due to oxygen consumption.1 Relative oxygen and TEMPO concentrations were calculated using convolution-based fitting approach developed by A. Smirnov2 (Figure 1).

6 7000

TEMPO Signal 6000 5

intensity 5000

4

5 G 4000

3

3000

2

2000

1 O2

1000 ReactionProgress and TEMPO Concentrations and TEMPO 2 O

0 0

0 2 4 6 8 10 12 14 16 18 Time / hours

Figure 1. EPR spectra of TEMPO/methyl methacrylate mixture at 120°C and time evolution of oxygen and TEMPO concentration.

The results showed that oxygen was consumed much faster than TEMPO. The rate of TEMPO consumption was nearly independent of the oxygen concentration. These results were explained in terms of autoxidation of the alkyl chain in the monomer. O O O O O O H O2 2 C O O O Our interpretation was confirmed by much slower oxygen consumption by tert-butyl acrylate which lacks labile hydrogens.

References. 1 M Conte, Y Ma, C Loyns, P Price, D Rippon and V Chechik, Org. Biomol. Chem., 2009, 7, 2685 2 T I Smirnova and A I Smirnov, in: ESR spectroscopy in Membrane Biophysics, M A Hemminga and L J Berliner, Eds. Springer, Amsterdam,2007

P24 Poster 25

Exploring Iron-Sulphur Clusters by Multi-Frequency/Multi- Resonance EPR/ENDOR Spectroscopy

Müge Aksoyoglu, Erik Schleicher, Christian Kerpal and Stefan Weber

Albert-Ludwigs-Universität Freiburg, Institut für Physikalische Chemie Albertstraße 21, 79104 Freiburg / Germany

Iron-sulphur clusters are involved in a wide range of important biochemical reactions. Owing to their remarkable structural plasticity and versatile chemical/electronic features, these clusters participate in electron transfer, substrate binding and activation, iron/sulphur storage, regulation of gene expression, and enzyme activity [1]. During the last decades the understanding of the electronic properties of iron-sulphur clusters has progressed considerably by the complementary use of mainly electron paramagnetic resonance (EPR), Mössbauer spectroscopy and X-ray crystallography, but remains far from being fully understood.

In this contribution, we present a multi-frequency EPR study of two different [Fe-S] proteins: (i) The [Fe-S] cofactor from the IspH enzyme, which catalyses the syntheses of isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) as last step of the non-mevalonate pathway [2], is investigated using various EPR and ENDOR methods. (ii) Recent pulse-EPR results obtained from NADH:quinone oxidoreductase (complex 1 of the respiratory chain) [3] will be presented and compared with published data.

The work presented has been performed in collaboration with: A. Bacher and M. Fischer (Hamburg University); T. Gräwert and M. Groll (TU München); T. Spazal, U. Glessner, T. Friedrich and O. Einsle (Freiburg University).

References:

[1] Johnson, D. C., Dean, D. R., Smith, A. D. and Johnson, M. K. Structure, function, and formation of biological iron-sulfur clusters. Annu. Rev. Biochem. 2005, 74, 247–81. [2] Eisenreich, W., Bacher, A., Arigoni, D. and Rohdich, F. Biosynthesis of isoprenoids via the non-mevalonate pathway.Cell Mol Life Sci. 2004, 61, 1401–26. [3] Ohnishi, T. and Nakamaru-Ogiso. E. Were there any "misassignments" among iron- sulfur clusters N4, N5 and N6b in NADH-quinone oxidoreductase (complex I)? Biochim Biophys Acta. 2008, 1777, 703–10.

P25 Poster 26

Multifrequency EPR spectroscopy on tyrosyl radicals in Photosystem II from the extreme halophyte Salicornia veneta

M. Di Valentin*, E. Salvadori*, R. Barbato**, A. Trotta**, J. Niklas***, A. Savitsky***, W. Lubitz***, D. Carbonera*

* Università degli Studi di Padova, Dipartimento di Scienze Chimiche, Padova, Italy **Università del Piemonte Orientale, Dipartimento di Scienze dell’Ambiente e della Vita, Alessandria, Italy ***Max-Planck-Institut für Bioanorganische Chemie, Mülheim an der Ruhr, Germany

The X- and W-band EPR investigation is devoted to the understanding of the primary sequence of photosynthetic reactions in the extreme halophyte Salicornia ve- neta. Halophytes are a heterogeneous group of plants, with genera widespread in many phylogenetically unrelated families, differing in salt tolerance and concentration of salt required for optimal growth. Halophytes live in particular environments, such as salt marshes and coastal saline pans, characterized by a total salt concentration up to 1 M.

Salicornia veneta is depleted of some proteins of the oxygen-evolving complex of Photosystem II (PSII). In fact, thylakoids of Salicornia veneta do not contain the PsbQ protein and are also partly depleted of the PsbP unit when compared to spinach. All other thylakoid subunits are present in amounts similar to those found in spinach thylakoids. Studies in vitro have shown that these subunits have a role in modulating the function of Ca2+ and Cl- cofactors but their function in vivo remains to be elucidated.

There are few reported data, on the photosynthetic membranes of Salicornia ve- neta, which point to the presence of a PSII characterized by a modified donor side. To • investigate this point, we have performed a multifrequency EPR study of the YD and • YZ tyrosyl radicals in the PSII preparations of Salicornia veneta. This allowed to have an high spectral resolution, separate the contribution of different species and determine · · the g-values and the hyperfine couplings of both YD and YZ with precision. Simula- tions of the X- and W-band spectra have been performed in order to get the full set of parameters, compare them to those corresponding to the spinach PSII and draw some conclusions about a possible modified environment of these radicals in Salicornia ve- neta.

P26 Poster 27

Probing the Neurotensin Receptor 1 Structure and Ligand Dynamics via Electron Paramagnetic Resonance

Marcella Orwick, Patricia Dijkman, Helen Attrill, Timothy Hadingham, Anthony Watts

University of Oxford, Department of Biochemistry, South Parks Road, Oxford OX1 3QU.

G-protein coupled receptors (7 TM GPCRs) represent the largest class of membrane proteins encoded for in the human genome. GPCR proteins are associated with many diseases such as Alzheimer’s and Parkinson disease, and therefore represent major drug targets in the pharmaceutical industry (Kitabgi, 2006). Neurotensin Receptor 1 (NTS1) is one of few 7 TM GPCR proteins that can be expressed in E coli. and purified in a functional, ligand-binding form for structural studies. To date, cw EPR methods are being employed to gather dynamic information about NTS1 and its interactions with its natural agonist, neurotensin (NT), a 13-amino acid peptide. NTS1 has also been spin-labelled to date in a functional form. The bacteriorhodopsin mutant D38C/F156C mutant, a GPCR homologue, was also spin-labelled, and successful DEER measurements were completed. This serves as a model-case for the spin-labelling and measurement of dipolar interactions with membrane-embedded proteins, and was done in preparation for future DEER measurements with NTS1. Ultimately, these studies will provide significant insights into the structure and dynamics of NTS1 with its agonist NT and with membrane lipids, as well as advance our knowledge of how GPCRs are activated for signalling through conformational changes for various functional intermediates to which these ESR methods are very well suited, and may therefore help in drug design.

P. Kitabgi, Peptides, 2006, 27(10), 2461-8. T. Rink et al., Biophysical Journal, 1997, 73, 983-993. P.J. Harding et al., Biochemical Society Transactions, 2007, 35(4), 760-763. D. Oesterhelt, W. Stoeckenius, Methods in Enzymology, 1974, 31, 667-678. G. Jeschke et al., Journal of Magnetic Resonance, 2002, 155, 72-82.

P27 Poster 28

Study of the chaperone-usher pathway in E. coli using SDSL-EPR

Katharina F. Pirker,* William Allen,** Micha B. A. Kunze,* Gabriel Waksman,*,** and Christopher W. M. Kay*

*Institute of Structural & Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK **Institute of Structural & Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, UK

Bacterial infection by uropathogenic Escherichia coli (UPEC) is the primary cause for urinary tract infections in Europe and North America and affects many individuals; especially women. There is an increase in resistance to antibiotics by these bacteria and studies of the onset of bacterial infection are gaining importance. The active parts of the bacterium are the fibers (also called pili) which are assembled by the chaperone-usher (CU) pathway. The surface fiber type 1 pili are important attachment devices that target UPEC to the bladder epithelium and are encoded by the fim gene cluster (fimA-I). Type 1 pili are thus major virulence factors in the onset of cystitis.

The current paper employs site-directed nitroxide spin-labelling (SDSL) in combination with continuous-wave (cw) and pulsed electron paramagnetic resonance (EPR) spectroscopy to investigate the chaperone- usher (CU) pathway of type 1 pili of UPEC. D D The polymerisation mechanism at the outer H membrane usher is assumed to involve the N- C and C-terminal domains of the FimD2 usher dimer.1 Initial experiments focused on the systematic spin labelling of either both N- or N-term N-term both C-terminal domains of FimD2 bound to G the FimC:FimH chaperone:adhesin complex, C and spin labelling of the chaperone FimC

** * which recruits the next subunit FimG, to the Scheme of FimD2 CHC G FimD2CH complex (e.g. see Figure). (red stars indicate the labelling sites) Preliminary results will be presented including successful spin labelling of the proteins (using MTSSL) and distances obtained after the binding of the FimC:FimG chaperone- subunit complex to the N- or C-terminal domain of the usher protein.

1Remaut H. et al. (2008) Cell 133, 640-652.

Acknowledgements. This project is funded by the Austrian Science Fund (Schrödinger Fellowship for K.F.P.) and a Wellcome Trust Programme grant 082227 to G.W.

P28 Poster 29

Experimental observations of the interplay between microwave and optical photons in fullerenes Rizvi Rahman1, John J.L. Morton1,2, Arzhang Ardavan2, Archana Tiwari1 Geraldine Dantelle1, Kyriakos Porfyrakis1, Klaus-Peter Dinse3, G. Andrew. D. Briggs1 1 Department of Materials, Oxford University, Oxford OX13PH, UK. 2 CAESR, Department of Chemistry, Oxford University and Clarendon Laboratory, Department of Physics, Oxford University, Oxford, OX13PU, UK. 3 Physikalische Chemie III, Eduard-Zintl-Institut, Technische Universit¨at Darmstadt, Petersenstr. 20, 64287 Darmstadt, Germany. Under experimentally accessible conditions, microwave photons can be used for manipulating spin qubits in carbon based materials. In addition, optical photons emitted from such molecules can be detected with extremely high sensitivity. Therefore, looking at how microwave transitions influence the optical ones and vice-versa can give important insight on sensitive qubit readout in fullerenes. In this poster, the experimental results on the fullerene C70 will be presented, where the triplet state has been detected at 5 K both by light induced electron spin resonance (LESR) and optically detected magnetic resonance (ODMR). Another example of the interplay of microwave and optical photons is the phenomenon of photoisomer switching in the rare-earth doped metallofullerene ErSc2N@C80. The switching effect has been observed by monitoring the time evolution of the ESR signal under laser illumination at temperatures from 5 to 10 K. Our current understanding of the switching dynamics will be discussed.

P29 Poster 30

Theoretical EPR Studies of the Structure and Bonding of Organouranium(V) Complexes

Hayley Wood

School of Chemistry, The University of Manchester, Oxford Road, Manchester, UK, M13 9PL

G-tensor calculations have been performed using the B3LYP exchange-correlation functional and the all-electron uranium TZVPP basis set on the optimised geometries of 8 + the doublet state uranium(V) complexes, [U(η -C8H8)(NEt2)2(THF)] 1, 5 8 5 [U(η -C5H5)2(NEt2)2] 2 and [U(η -C8H8)(η -C5H5)(NEt2)2] 3. The SVP basis set was adopted for all other atoms. The relativistic approximations ZORA, IORA and IORAmm were implemented and results have shown very poor agreement with experimental data. The resolution of the identity representation of ZORA (ZORA-RI) was also tested on 1 and in this case has shown no improvement in the calculation of g- tensors. One advantage of using ZORA-RI over the other methods is that the calculations are faster due to the use of analytical rather than numerical integration, thus making it less computationally expensive. Due to the extremely poor results obtained for the doublet state complexes, Hartree-Fock and density functional calculations have been performed on the quartet state of 1. This has shown some promise as the calculated energies were lower than the doublet state energies suggesting that the quartet state is the actual ground state. Therefore, g-tensor calculations on the quartet state may compare well with experiment. All g-tensor calculations were performed using the ORCA program. Geometry optimisations were performed using the Gaussian 03 program at the SVWN5 or B3LYP levels of theory along with either the small-core pseudopotential SVP or large-core pseudopotential CRENBL basis sets.

P30 Poster 31

Analysis of the “half-field” signal of S=1 type species present in frozen solutions of [VO(acac)2] and [Cu(acac)2]

Daniel Sells*, David Collison*, Eric J L McInnes*, Ruth Edge*, Joanna Wolowska*

*The University of Manchester, School of Chemistry, Oxford Road, Manchester, M13 9PL

-diketonate complexes of the d-transition metals form “classical” coordination compounds. Oxovanadium(IV) (3d1) and copper(II) (3d 9) bis-acetylacetonates (pentane- 2,4-dionates) are prototypical examples of S = ½ systems for study by EPR spectroscopy. There have been many such studies of the two molecules reporteda mostly at X-band and including multiple resonance and pulse techniques. We describe here a study of the “half-field” vanadyl bis-acetylacetonate signal observed with frozen solutions of the above compounds, and investigate the structure of the S=1 type component by spectrum simulation. Frozen Solution of Cu(acac)2

L-band S-band

X-band K-band a For examples: I. Bernal, P. H. Reiger, Solvent Effects on the Optical and Electron Spin Resonance Spectra of Vanadyl Acetylacetonate. Inorg. Chem. (1963), 2(2), 256-260. T. E. Eagles, R. E. D. McClung, ESR line widths of vanadyl -diketonate complexes in liquid solutions. Can. J. Phys. (1975), 53(15), 1492-8.

P31 Poster 32

Understanding the structure of a novel Copper containing MOF and changes induced on it upon ultrasonication

Chandrima Pal*, M. I. H. Mohideen**, H. EL. Mkami ***, R. E. Morris**, O. Schiemann*

*School of Biology, Biomolecular Sciences Building **EaStChem School of Chemistry, ***School of Physics and Astronomy University of St Andrews, North Haugh, St Andrews, UK

Metal organic frameworks (MOFs) or coordination polymersi are attractive materials for application in gas storageii, separation by selective adsorption and catalysis because of their extremely high porosities. High structural diversity of these compounds, which can be obtained by combination of different organic solvents and transition metal ion complexes at various conditions, adds up to their potentiality. Moreover, the presence of residual paramagnetic transition metal ions in the MOF frameworks after synthesis can provide a way to develop novel porous materials with important magnetic properties like ferromagnetism, antiferromagnetism and ferrimagnetismiii. Synthesis of a novel metal-organic framework STAM-1 (St Andrews- MOF) was carried out by reacting 1, 3, 5-benzenetricarboxylic acid with copper nitrate. This is a dark blue coloured porous crystalline solid with a one dimensional channel which upon dehydration shows a moderate capacity to adsorb N2 or CO2 gas molecules. STAM-1 was further treated with ultrasonic waves to induce structural changes in the compound. Ultrasonication changed it to a light blue coloured solid and after dehydration showed no adsorption capacity for N2 or CO2. This confirms a new structural framework and is named as STAM-2. Various pulsed EPR experiments like Field sweep, 2- and 3 Pulse ESEEM and HYSCORE are performed to understand the structure of STAM-1 and the changes induced in it after ultrasonication.

i Yaghi, O. M.; Davids, C. E.; Li, G. M.; Li, H. L.; J. Am. Chem. Soc. 1991, 119, 2861 ii Mc Kinlay, A. C.; Xiao, B.; Wragg, D. S.; Wheatley, P. S.; Megson, L. I.; Morris, R. E.; J. Am. Chem. Soc. 2008, 130, 10440 iii Poeppl, A.; Kunz, S.; Himsl, D.; Hartmann, M.; J. Phys. Chem. C. 2008, 112, 2678

P32 Poster 33

Ligand Steric Hindrance in Controlling Chiral VO(5,5’)- Epoxide Interactions

Emma Carter,# Ian A. Fallis,# Damien M. Murphy,# David J. Willock,# Evi Vinck,* Sabine van Doorslaer.*

#School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK. *University of Antwerp, Department of Physics, SIBAC laboratory, Universiteitsplein 1, B-2610 Wilrijk, Belgium.

Weak diastereomeric interactions between chiral substrates in solution is fundamentally important in enantioselective separations and chemical transformations. These interactions are often so weak, they are difficult to observe and quantify by many analytical techniques, whilst the accuracy of computational work is sometimes limited by the small energies involved (comparable to solvation). In this Poster (using EPR, ENDOR and HYSCORE), we will provide evidence for enantiomer discrimination between a series of chiral paramagnetic metal complexes and chiral epoxides. We have previously reported that the complex [VO(1)] (Scheme 1) preferentially forms homochiral pairs with propylene oxide (2) i.e. the R,R’- enantiomer of the ligand will bind in favour with the R- enantiomer of the epoxide. In contrast, heterochiral combinations are preferred in frozen solution using the sterically less- hindered complex [VO(3)]. This result indicates that the bulky tert-butyl groups are involved in chiral recognition, since the preferential nature of the adducts formed are different for [VO(1)] and [VO(3)]. The level of diastereoselectivity in the system is further observed to be both temperature and concentration dependent, suggesting that a dynamic equilibrium is established. These findings reveal the potential importance of weak outer sphere interactions in stereoselectivities of enantioselective homogeneous catalysis, and may be used directly to explain the differences in enantioselectivities observed in catalytic reactions.

[VO(1)] [VO(3)]

Hexo Hendo NNO NNO V V OO OO

2H O H2 (2) Hr

1) D.M Murphy et al., PCCP (2009) 11, p6757 2) E.Carter et al., Chem. Phys. Lett (2010) 486, p74

P33 Poster 34

An EPR & ENDOR study of an asymmetric Cu-bis(oxazoline) complex used for asymmetric aziridination.

M. E. Owen, D. M. Murphy, G. J. Hutchings. School of Chemistry, Main Building, Cardiff University, Park Place, Cardiff CF10 3AT, UK

The asymmetric aziridination of styrene using Cu(OTf)2 as a homogeneous catalyst complexed with the chiral bis-oxazoline ligand (see below) has been studied by cw and pulsed EPR & ENDOR, using [N-(p-nitrophenylsulfonyl)imino]phenyliodinane (PhI=NTs) as the nitrene donor. The complex formed between enantiomers of this ligand and the Cu(OTf)2 pre-cursor were identified by their characteristic UV and EPR spectra. ENDOR also revealed the strongly coupled 14N interactions from the coordinated ligand [Cu(BOX)(OTf)2] in the precatalyst, in addition to the mainly dipolar interactions to the phenyl groups of the chiral ligand.

[Cu(1)] Ph Ph PhI=NTs N Ts O O

N N

Ph Ph

The catalytic reaction is usually carried out using an excess of the ligand compared to Cu(OTf)2, in addition to the remaining substrates. Under these conditions, it appears that only some of the copper pre-cursor actually complexes with the ligand, and as a result a mixed EPR signal (composed of Cu(OTf)2, and [Cu(BOX)(OTf)2]) is observed in some cases. The resulting Davies ENDOR spectra, are further complicated by the presence of intense signals at low frequencies (1-8 MHz) which may be due to outer- sphere weak interactions with 14N nuclei from excess ligand in solution (non- coordinated ligand). The presence of this excess ligand may adversely affect the orientation of the structure directing Ph (or tert-butyl) groups in the complexed [Cu(BOX)(OTf)2] catalyst. Since the orientation of these groups is paramount to the enantioselectivity of the reaction, we have sought to prepare and isolate the catalyst [Cu(BOX)(OTf)2] in the absence of excess ligand, in order to determine the orientation of the Ph (or tert-butyl) groups prior to the addition of the reaction substrates (PhI=NTs and styrene).

P34 Poster 35

W-band PELDOR with a dual-mode microwave resonator. Igor Tkach, Giuseppe Sicoli and Marina Bennati Max Planck Institute for Biophysical Chemistry, Am Faßberg 11, 37077 Göttingen, Germany

The main goal of high-field PELDOR experiments is, beside distance measurements, the information about the relative orientation of the spin labels within a radical pair. This is a crucial information to study conformational changes of labelled macromolecules which is encoded in complex patterns of orientation-selective PELDOR traces. However, the execution of such experiments, particularly in the case where the labels are not collinear, is aggravated by a narrow bandwidth of commercial single mode resonators. We present a dual-mode resonator operating at W-band microwave frequencies and supporting two microwave modes with the same field polarization at the sample position. The frequencies of both modes as well as their separation can be tuned in a broad range by means of special tuning mechanisms. The resonator was specifically designed to perform PELDOR experiments with a variable separation of pump and detection frequencies up to 350 MHz. The proposed resonator is a simple device which can be effectively used in high-field PELDOR spectroscopy. To test the new resonator ESE/PELDOR experiments were performed on model biradical systems with non-collinear orientations of g-tensors. The resonator design as well as some characteristic features of the observed PELDOR modulations are discussed.

P35 Title index A combined spin trapping/EPR/mass spectrometry approach to study the formation of a cyclic peroxide by dienolic precursor autoxidation, P9 A new electrode system for variable temperature in situ high field, EPR- spectroelectrochemistry in capillary tubes, P23 A novel tool to selectively resolve distances in complex macromolecular structures, T31 An EPR & ENDOR study of an asymmetric Cu-bis(oxazoline) complex used for asymmetric aziridination, P34 An EPR study of dehaloperoxidase from Amphitrite ornate – an oxygen storing globin with a peroxidase function, T20 Analysis of magnetic interactions in EPR and ENDOR: an approach to electronic and structural properties of redox centres in enzymes, T17 Analysis of the “half-field” signal of S=1 type species present in frozen solutions of [VO(acac)2] and [Cu(acac)2], P31 Analytical derivatives of spin dynamics simulations, T35 Anthrax Lethal Factor: Development of an EPR-based binding assay for ligand binding, P4 Coexistence of quantum and classic behaviour in EMR spectra of magnetic nanoparticles and molecular nanomagnets, T8 CW and pulsed EPR characterization of soluble metal phthalocyanines lacking C–H bonds, T9 Cyclodextrin-included nitroxides, T4 DEER measurements of a Cytochrome P450 and Ferredoxin complex, to determine the docked structure, T6 Development of Optical Spin-Resonance Methods with Advanced Light Sources, P21 Distance measurements in a WALP23 polypeptide labeled with a nitroxide radical and a lanthanide complex: relaxation enhancement, DEER and cw power saturation, T23 DNA radical-intermediates in UVA-irradiated DNA-riboflavin/melanin systems?, T40 Double Electron-Electron Resonance measured between gadolinium ion and nitroxide radical, P13 Electron dynamics in lithium ammonia solutions probed by X- and W-band pulse EPR, T34 Electron spin coherence times of metallofullerenes, P16 Electron spin coherence times of metallofullerenes, T10 EPR as a Probe of Spin Density Distribution in Organometallic Radicals with Extended Carbon Chain Ligands, T2 EPR detection of unexpected iminoxy radicals reacting reversible dyes and nitric oxide, P14

R1 EPR investigation of cationic radicals for organic electronics applications, T33 EPR measurements on Arabidopsis thaliana Cryptochrome-1, P5 EPR of Photosystem II, T22 EPR of the Cyanide Adducts of Protoglobin Mutants, P1 EPR Oximetry study of the thermal polymerisation of acrylates and methacrylates, P24 EPR Spectroelectrochemistry applied to Main Group Compounds, T3 EPR Studies of Linked Antiferromagnetic Rings: Towards Quantum Information Processing, T38 EPR-HYSCORE Study of Quinone Binding in Respiratory Nitrate Reductase: Molecular Basis for the Adaptation to Aerobiosis, T15 Experimental observations of the interplay between microwave and optical photons in fullerenes, P29 Exploring Iron-Sulphur Clusters by Multi-Frequency/Multi-Resonance EPR/ENDOR Spectroscopy, P25 Extreme Sensitivity and Distance Measurement: PELDOR on Deuterated Proteins, T19 First Structural Characterisation of a Magnesium Ketyl via EPR, ENDOR and Special TRIPLE Resonance Spectroscopy, P10 Function of a HAMP domain in bacterial signal transduction investigated by SDSL- EPR, P6 Graphical user interface for the construction and visualization of large spin systems, P3 High Performance, High Power, High Bandwidth, Pulsed EPR at 94 GHz, T28 Investigating a cell signalling protein using PELDOR, T41 Ligand Steric Hindrance in Controlling Chiral VO(5,5’)- Epoxide Interactions, P33 Melanin in natural, bleached & archaeological keratin fibres: EPR & Colourimetric study, P7 Melanin-dependent UVA-induced radical damage in melanoma cells: correlation with DNA damage and influence of cell growth/nutritional state, P20 Model systems to measure short distances between nitroxide radical and lanthanide complex with cw EPR, P2 Molecular Magnets as Qubits: Extending the Phase Coherence Time, T39 Molecular structure refinement by direct atomic coordinate fitting to ESR spectra, T7 Multifrequency EPR spectroscopy on tyrosyl radicals in Photosystem II from the extreme halophyte Salicornia veneta, P26 Nano graphites studied by Electron Paramanetic Resonance: an insight on the nature of the signals, T32 Neuroglobin: a continuing challenge for EPR spectroscopy, T27 On the formation of O2- radicals by adsorption of O2 on thin MgO films, T12

R2 On the state of ZFS in DFT and ab initio methods, P17 Optimization of Dynamic Nuclear Polarization Experiments in Aqueous Solution at 15 MHz/9.7 GHz for a Shuttle DNP Spectrometer, T36 Orientation effects in copper phthalocyanine films studied by EPR Spectroscopy, P15 PELDOR measurements using spin-labelled nucleobase c that binds non-covalently to guanine opposite an abasic site in DNA, P8 PELDOR on DNA: Orientations, Dynamics, Bending, Non-Covalent Labelling and Protein Binding, T18 Photosensitized formation of free radicals and singlet oxygen by a PD- bacteriochlorophyll derivative, T29 Prediction of motional EPR spectra from Molecular Dynamics (MD) simulations, T26 Probing Flexibility in Porphyrin-Based Molecular Wires using DEER, T24 Probing the Neurotensin Receptor 1 Structure and Ligand Dynamics via Electron Paramagnetic Resonance, P27 Pulse-based electron magnetic resonance spin technology and a chemists’ materials challenge: A few steps towards molecular spin quantum computers and quantum information processing, T37 Pulsed EPR spectroscopy and DFT calculations for “difficult” nuclei, T14 Pulsed EPR studies of the excited triplet state in diethyl fullerene malonate, T42 Quantum information storage using electron and nuclear spins in silicon, T13 Role of the flexible chaperon protein NarJ in the biogenesis of nitrate reductase: structural analysis by EPR and site-directed spin labeling, P22 SDSL and EPR spectroscopy applied for structural and functional studies on human guanylate binding protein I, T30 Spin Counting and Spin Trapping, P11 Stereoselective interactions in asymmetric metal complexes probed by EPR spectroscopy, T1 Study of the chaperone-usher pathway in E. coli using SDSL-EPR, P28 Surface stabilized inorganic radicals and radical ions, T11 Synthetic, structural and electronic investigations of the alkynyl cyclopentadienyl molybdenum complexes [Mo(C?CR)(CO)(L2)Cp’]n+ (n = 0 or 1; R = Ph or C6H4-4- Me, L2 = Ph2PCH2CH2PPh2 or 2PMe3, Cp’ = Cp or Cp*), P19 The dienolic compound PG3, a novel cheletropic trap for nitric oxide EPR detection, T5 The fidelity of spin trapping with DMPO in biological systems, T21 The Macrocyclic Stabilisation of Unusual Metal Oxidation States: An EPR, ENDOR and DFT study on [Pt([9]aneS3)2]3+, P12 Theoretical EPR Studies of the Structure and Bonding of Organouranium(V) Complexes, P30

R3 Time-Resolved High-Field EPR Spectroscopy on Natural Photosynthesis: Primary Electron Transfer Reactions in Photosystem I, T25 Uncoupled Spins Spaced by an Insulating Tetraphoshine Unit: A Little D Measured by cw EPR, T43 Understanding the Catalytic Mechanism of Methane Production by Methyl-coenzyme M Reductase with Labeled Substrates and Substrate Analogues, T16 Understanding the structure of a novel Copper containing MOF and changes induced on it upon ultrasonication, P32 Water Soluble, Nitroxide-Coated Gold Nanoparticles as MRI Contrast Agents, P18 W-band PELDOR with a dual-mode microwave resonator, P35

R4 Author Index

Ms Müge Aksoyoglu P25 Dr Antonio Barbon T32 Mr Simon Bennie P17 Prof Rene T. Boere T3 Miss Alice M. Bowen T6, T16 Mr Richard M. Brown P16, T10, T13 Prof Mylene Campredon P14 Dr Emma Carter P33, P12 Ms Lisa Castelli T8 Mr Gareth T. P. Charnock T7, P3 Dr Victor Chechik P7, P18, P24, T4 Prof David Collison T38, P12, P19, P23, P31, T2 Mr Filip Desmet P1 Dr Marilena Di Valentin T12, P26 Dr Ruth Edge P12, P19, P23, P31, T2 Prof John H. Enemark T14 Ms Maria A. Ezhevskaya T27 Dr Solveig Felton P15 Ms Vasileia Filidou T42 Dr Maria Fittipaldi T8 Dr Guillaume Gerbaud P22 Prof Elio Giamello T11 Prof Bruno Guigliarelli T15, P22 Dr Jeffrey R. Harmer T16, T34, T6 Dr Rachel M. Haywood T40, P20 Dr Peter Hoefer P11, T36 Dr Reinhard Kappl T17 Dr Chris W.M. Kay P15, P28, T24, T40 Dr Johann P. Klare P6, T30 Mr Daniel Klose P4, P6, P15, T30 Mr Thomas Kohn P2, T23 Dr Matthew Krzystyniak T7 Mr Micha B.A. Kunze P4, P28 Dr Ilya Kuprov P3, T7, T35 Miss Hannah N. Lancashire P19, T2 Dr Robert P. Lauricella T5 Dr Janet E. Lovett T6, T24 Mrs Petra Lueders P2, P13, T23 Dr Fraser MacMillan T31 Dr Kiminori Maeda T34, T42

R5 Dr Ronald Mason T21 Miss Lucia E. McDyre P10 Prof Eric McInnes P21, P23, P31, T38, T39 Mr Hans Moons T9, T33 Dr John J.L. Morton P16, P29, T10, T13, T39, T42 Dr Damien M. Murphy P10, P12, P33, P34, T1 Mr Kazim R. Naqvi P7 Mr Thomas E. Newby P24 Dr David G. Norman T19, T41 Dr Vasily Oganesyan T26 M Marcella C. Orwick P27 Miss Elena M. Owen P34 Dr Chandrima Pal P32 Dr Katharina F. Pirker P28 Dr Oleg G. Poluektov T25 Mr Rizvi Rahman P29 Mr Gunnar W. Reginsson P8, T18 Mr Thomas Risse T12 Prof Alfred W. Rutherford T22 Prof Tadeusz J. Sarna T29 Dr Olav Schiemann P8, P32, T18 Mr Daniel Sells P23, P31 Dr Graham M. Smith T18, T28 Dr Stephen Sproules T43 Miss Emma L. Stephen P12 Dr Dimitri A. Svistunenko T7, T20 Prof Takeji Takui T37 Dr Igor Tkach T36, P35 Dr Brian M. Towlson P21 Ms Mathilde M. Triquigneaux P9, T5 Dr Beatrice N. Tuccio P9, T5 Dr Floriana Tuna T38 Ms Maria‐Teresa Türke T36 Prof Sabine Van Doorslaer P1, P33, T9, T27, T33 Dr Arsen Volkov P20, T40 Dr Richard J. Ward T19, T41 Mr Muhammad F. Warsi P18 Mr Christopher J. Wedge T39 Mr Ringo Wenzel P5 Dr Mark W. Whiteley P19, T2 Miss Hayley Wood P30 Dr Maxim Yulikov P2, P13, T23

R6