Crystallography News British Crystallographic Association

Total Page:16

File Type:pdf, Size:1020Kb

Crystallography News British Crystallographic Association Crystallography News British Crystallographic Association Issue No. 125 June 2013 ISSN 1467-2790 Coming soon: ECM28 AGM of the BCA p6 Bragg Centenary Events p9 Bursary Recipientsʼ Reports p15 Worldwide Protein Data Bank p16 News from the Groups p20 EXPERIENCE TRUE BRILLIANCE Confidence means a revolutionary high-brilliance X-ray system that meets the needs of the most challenging crystallography projects. Agilent’s new GV1000 X-ray diffractometer represents a major leap forward in the generation of X-rays for demanding structural biology applications. The GV1000 combines novel approaches in all core source components, with innovative gradient vacuum technology affording an extremely compact, quiet and high-brilliance X-ray source. See macromolecular structures in a whole new light with the brilliant new Agilent GV1000 X-ray diffractometer. Learn more at www.agilent.com/lifesciences/GV1000. Discover the powerful new features in Agilent’s CrysAlisPro software. Register for our 2013 Software and Applications Webinar Series at www.agilent.com/chem/xray_eSeminars © Agilent Technologies, Inc. 2013 PDF-4/Organics 2013 What’s in your sample? Verify your results with PDF-4/Organics A comprehensive materials database featuring 471,257 organic and organometallic compounds. Designed for rapid materials identifi cation Polymorph screening Quality control Drug & Excipients identifi cation Formulation analysis Quantitative analysis Polymorph identifi cation Crystallite size COMPREHENSIVE ❖ STANDARDIZED ❖ QUALITY REVIEW www.icdd.com | marketing @icdd.com 610.325.9814 | toll-free 866.378.9331 (U.S. & Canada) ICDD, the ICDD logo and PDF are registered in the U.S. Patent and Trademark Offi ce. Powder Diff raction File is a trademark of JCPDS—International Centre for Diff raction Data. Going small smaller beam, smaller footprint, smaller maintenance costs means big results Introducing the new DECTRIS PILATUS 200K • Rigaku’s Compact HomeLab features the Rigaku Compact HomeLab™ PILATUS 200K - a true photon counting detector with the lowest noise and highest dynamic range • Micro focus sealed tube generator and confocal double-bounce optic off ers great performance with minimal maintenance • The PILATUS 200K detector is air cooled to reduce maintenance • A system that fi ts your research needs and budget while providing unprecedented performance, especially for weakly diff racting samples Rigaku Corporation and its Global Subsidiaries website: www.Rigaku.com | email: [email protected] Crystallography News June 2013 Contents From the President. 2 BCA Council 2013. 3 From the Editor. 4 BCA Administrative Office, Helen Leese Puzzle Corner. 5 First Floor Hornbeam House 2012 Annual General Meeting of the BCA. 6 Hornbeam Business Park Harrogate HG2 8QT Tel: +44 (0)1423 855 990 Centenary Events. 9 Fax: +44 (0)1423 855 999 e-mail: [email protected] Announcing the 2013 Ludo Frevel Crystallography Scholarship Recipients. 12 CRYSTALLOGRAPHY NEWS is published quarterly (March, June, September and PANalytical Award to Thomas Bennett. 13 December) by the British Crystallographic Association, and printed by Bowmans, Leeds. Text should preferably be sent electronically as MSword documents Bursary Recipients’ Reports. 14 (any version - .doc, .rtf or .txt files) or else on a PC disk. Diagrams and figures are most welcome, but please send them Worldwide Protein Data Bank. 16 separately from text as .jpg, .gif, .tif, or .bmp files. Items may include technical articles, news about people (eg awards, Argon: a Noble Gas and Two Noble honours, retirements etc), reports on past meetings of interest to crystallographers, Crystallographers. 18 notices of future meetings, historical reminiscences, letters to the editor, book, hardware or software reviews. News from the Groups. 20 Please ensure that items for inclusion in the September 2013 issue are sent to the Editor to arrive before 25 July 2013. Books. 21 Carl Schwalbe 15 St Augustine Drive Droitwich Obituaries. 23 Worcs WR9 8QR Tel: 01905 775257 e-mail: [email protected] Meetings of Interest. 26 The British Crystallographic Association is a Registered Charity (#284718) As required by the DATA PROTECTION ACT, the BCA is notifying members that we store your contact information on a computer database to simplify our administration. These details are not divulged to any others This month’s cover: without your permission. You may inspect your entry during the Annual Meeting, or otherwise by application to the BCA Exhibition at the Science Administrative Office. We will be happy to amend entries at any time. Museum, London (photos by Jennie Hills); scenes Printed by Bowmans from the Big Bang Fair Westland Square, Westland Road, Leeds, LS11 5SS Tel: 0113 272 0088 Web: www.bowmans77.co.uk Crystallography News June 2013 1 From the President IN my last column I used the shape every 30 seconds or so for wave upon wave of phrase ‘no relation’ when school pupils quickly took its toll on my stamina, so ‘hats writing about Melvyn Bragg off’ to those who were working on the stand for a whole day and his Radio 4 ‘In Our Time’ – let alone for four! Robin Clegg, the Head of Public programme on William and Engagement at STFC wrote after he visited on the Friday, Lawrence Bragg. I had had it on “The Crystallography stand was excellent and hugely good authority that although popular. I understand that the BB management thought it they came from the same part one of the best.” And Laura Holland from the Diamond of the country, Melvyn and the Public Engagement team e-mailed me afterwards, “The crystallographic Braggs were event was fantastic, and I can’t tell you how impressed I indeed unrelated. Inevitably no was by the enthusiasm and talent of the volunteers. You’ve sooner had Crystallography News been published than got a really good group of communicators, which the the same good authority (i.e. Mike Glazer) came back to association should be very proud of.” I would like to single me with a pair of family trees showing that William Henry out Ross for particular thanks for his excellent coordination Bragg’s great, great, grandparents Henry (1724-1795) and hard work in making the event happen, and to thank and Sarah (née Lightfoot, 1724-1779) were also Melvyn STFC (and, in the background, RCUK) for their substantial Bragg’s ancestors. In the spirit of Leveson I apologise funding, to Diamond for their many contributions and of for my inaccurate journalism! I understand that this real, course to all the BCA volunteers; keep – and wear – those albeit somewhat distant, link between these Braggs has yellow T-shirts with pride! prompted Melvyn to collaborate on at least one other Bragg-related programme to be broadcast in due course. Preparations for the 28th European Crystallographic Meeting in Warwick are gathering pace and the scientific The crystallography centenary story is indeed gathering programme is looking really good. By the time that you read momentum. As I got into my car to drive home this evening, this I hope that you will have already registered for the the PM programme on Radio 4 (to think that I never used to meeting and have submitted abstracts for consideration as listen to this station…) had a news article by BBC reporter talks and/or posters. The meeting organisers, led by Sandy Louise Jackson on the Bragg Centenary from Leeds Blake, are adding content to the ECM28 web site University, with interviews with Kersten Hall, Chris (ecm28.ecanews.org/) almost daily. Please do check it Hammond and Tom Edwards. Chris Hammond suggested regularly for up to date information about the meeting. I look that “modesty” probably prevented the Braggs from being forward to meeting a strong cohort of BCA members at this better known or being given their rightful place in history. It year’s European Crystallographic Meeting on our home soil. was excellent to hear that the message, “X-ray crystallography We will also be holding our Annual General Meeting at changed science” is reaching such a wide audience. If you ECM28 in Warwick. As part of this we will be electing are planning any Bragg Centenary related events this year or members to BCA Council. Further details are given in this events for the International Year of Crystallography in 2014 issue of Crystallography News and if you are interested in then please do let us know so that we can advertise them. standing for one of the available positions then please either We are collating information on all events on our web site contact me or one of the other BCA Officers. (crystallography.org.uk/bragg-centenary/). You can also use the Bragg Centenary Logo for your outreach events and I hope that you enjoy reading this issue of Crystallography can obtain free copies of the STFC-produced ‘broadsheet’ News. on crystallography from www.stfc.ac.uk/1889#PSG for giving out at your events. Four thousand of these were David Keen distributed at our stand at the Big Bang Fair so they are clearly popular. The highlight of the past few months was undoubtedly our contribution to the Big Bang Science and Technology Fair at the ExCeL Centre in London. Ross Harrington writes more on this later in this issue of Crystallography News, but last March around 40 BCA members were yellow T-shirted demonstrators to around 75,000 visitors at the BCA-STFC- DLS stand “The Structure of Stuff is Sweet”. It was a fantastic event and our stand attracted huge crowds of people of all ages. They were intrigued and enthralled by marshmallow unit cells, marble crystals, real time lysozyme crystal growth and even a lego diffractometer.
Recommended publications
  • Biochemistry and the Genomic Revolution 1.1
    Dedication About the authors Preface Tools and Techniques Clinical Applications Molecular Evolution Supplements Supporting Biochemistry, Fifth Edition Acknowledgments I. The Molecular Design of Life 1. Prelude: Biochemistry and the Genomic Revolution 1.1. DNA Illustrates the Relation between Form and Function 1.2. Biochemical Unity Underlies Biological Diversity 1.3. Chemical Bonds in Biochemistry 1.4. Biochemistry and Human Biology Appendix: Depicting Molecular Structures 2. Biochemical Evolution 2.1. Key Organic Molecules Are Used by Living Systems 2.2. Evolution Requires Reproduction, Variation, and Selective Pressure 2.3. Energy Transformations Are Necessary to Sustain Living Systems 2.4. Cells Can Respond to Changes in Their Environments Summary Problems Selected Readings 3. Protein Structure and Function 3.1. Proteins Are Built from a Repertoire of 20 Amino Acids 3.2. Primary Structure: Amino Acids Are Linked by Peptide Bonds to Form Polypeptide Chains 3.3. Secondary Structure: Polypeptide Chains Can Fold Into Regular Structures Such as the Alpha Helix, the Beta Sheet, and Turns and Loops 3.4. Tertiary Structure: Water-Soluble Proteins Fold Into Compact Structures with Nonpolar Cores 3.5. Quaternary Structure: Polypeptide Chains Can Assemble Into Multisubunit Structures 3.6. The Amino Acid Sequence of a Protein Determines Its Three-Dimensional Structure Summary Appendix: Acid-Base Concepts Problems Selected Readings 4. Exploring Proteins 4.1. The Purification of Proteins Is an Essential First Step in Understanding Their Function 4.2. Amino Acid Sequences Can Be Determined by Automated Edman Degradation 4.3. Immunology Provides Important Techniques with Which to Investigate Proteins 4.4. Peptides Can Be Synthesized by Automated Solid-Phase Methods 4.5.
    [Show full text]
  • Sequencing As a Way of Work
    Edinburgh Research Explorer A new insight into Sanger’s development of sequencing Citation for published version: Garcia-Sancho, M 2010, 'A new insight into Sanger’s development of sequencing: From proteins to DNA, 1943-77', Journal of the History of Biology, vol. 43, no. 2, pp. 265-323. https://doi.org/10.1007/s10739-009- 9184-1 Digital Object Identifier (DOI): 10.1007/s10739-009-9184-1 Link: Link to publication record in Edinburgh Research Explorer Document Version: Peer reviewed version Published In: Journal of the History of Biology Publisher Rights Statement: © Garcia-Sancho, M. (2010). A new insight into Sanger’s development of sequencing: From proteins to DNA, 1943-77. Journal of the History of Biology, 43(2), 265-323. 10.1007/s10739-009-9184-1 General rights Copyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Download date: 28. Sep. 2021 THIS IS AN ADVANCED DRAFT OF A PUBLISHED PAPER. REFERENCES AND QUOTATIONS SHOULD ALWAYS BE MADE TO THE PUBLISHED VERION, WHICH CAN BE FOUND AT: García-Sancho M.
    [Show full text]
  • See the Scientific Petition
    May 20, 2016 Implement the Endangered Species Act Using the Best Available Science To: Secretary Sally Jewell and Secretary Penny Prtizker We, the under-signed scientists, recommend the U.S. government place species conservation policy on firmer scientific footing by following the procedure described below for using the best available science. A recent survey finds that substantial numbers of scientists at the U.S. Fish and Wildlife Service (FWS) and the National Oceanic and Atmospheric Administration believe that political influence at their agency is too high.i Further, recent species listing and delisting decisions appear misaligned with scientific understanding.ii,iii,iv,v,vi For example, in its nationwide delisting decision for gray wolves in 2013, the FWS internal review failed the best science test when reviewed by an independent peer-review panel.vii Just last year, a FWS decision not to list the wolverine ran counter to the opinions of agency and external scientists.viii We ask that the Departments of the Interior and Commerce make determinations under the Endangered Species Actix only after they make public the independent recommendations from the scientific community, based on the best available science. The best available science comes from independent scientists with relevant expertise who are able to evaluate and synthesize the available science, and adhere to standards of peer-review and full conflict-of-interest disclosure. We ask that agency scientific recommendations be developed with external review by independent scientific experts. There are several mechanisms by which this can happen; however, of greatest importance is that an independent, external, and transparent science-based process is applied consistently to both listing and delisting decisions.
    [Show full text]
  • DNA: the Timeline and Evidence of Discovery
    1/19/2017 DNA: The Timeline and Evidence of Discovery Interactive Click and Learn (Ann Brokaw Rocky River High School) Introduction For almost a century, many scientists paved the way to the ultimate discovery of DNA and its double helix structure. Without the work of these pioneering scientists, Watson and Crick may never have made their ground-breaking double helix model, published in 1953. The knowledge of how genetic material is stored and copied in this molecule gave rise to a new way of looking at and manipulating biological processes, called molecular biology. The breakthrough changed the face of biology and our lives forever. Watch The Double Helix short film (approximately 15 minutes) – hyperlinked here. 1 1/19/2017 1865 The Garden Pea 1865 The Garden Pea In 1865, Gregor Mendel established the foundation of genetics by unraveling the basic principles of heredity, though his work would not be recognized as “revolutionary” until after his death. By studying the common garden pea plant, Mendel demonstrated the inheritance of “discrete units” and introduced the idea that the inheritance of these units from generation to generation follows particular patterns. These patterns are now referred to as the “Laws of Mendelian Inheritance.” 2 1/19/2017 1869 The Isolation of “Nuclein” 1869 Isolated Nuclein Friedrich Miescher, a Swiss researcher, noticed an unknown precipitate in his work with white blood cells. Upon isolating the material, he noted that it resisted protein-digesting enzymes. Why is it important that the material was not digested by the enzymes? Further work led him to the discovery that the substance contained carbon, hydrogen, nitrogen and large amounts of phosphorus with no sulfur.
    [Show full text]
  • Physics Today - February 2003
    Physics Today - February 2003 Rosalind Franklin and the Double Helix Although she made essential contributions toward elucidating the structure of DNA, Rosalind Franklin is known to many only as seen through the distorting lens of James Watson's book, The Double Helix. by Lynne Osman Elkin - California State University, Hayward In 1962, James Watson, then at Harvard University, and Cambridge University's Francis Crick stood next to Maurice Wilkins from King's College, London, to receive the Nobel Prize in Physiology or Medicine for their "discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material." Watson and Crick could not have proposed their celebrated structure for DNA as early in 1953 as they did without access to experimental results obtained by King's College scientist Rosalind Franklin. Franklin had died of cancer in 1958 at age 37, and so was ineligible to share the honor. Her conspicuous absence from the awards ceremony--the dramatic culmination of the struggle to determine the structure of DNA--probably contributed to the neglect, for several decades, of Franklin's role in the DNA story. She most likely never knew how significantly her data influenced Watson and Crick's proposal. Franklin was born 25 July 1920 to Muriel Waley Franklin and merchant banker Ellis Franklin, both members of educated and socially conscious Jewish families. They were a close immediate family, prone to lively discussion and vigorous debates at which the politically liberal, logical, and determined Rosalind excelled: She would even argue with her assertive, conservative father. Early in life, Rosalind manifested the creativity and drive characteristic of the Franklin women, and some of the Waley women, who were expected to focus their education, talents, and skills on political, educational, and charitable forms of community service.
    [Show full text]
  • Los Premios Nobel De Química
    Los premios Nobel de Química MATERIAL RECOPILADO POR: DULCE MARÍA DE ANDRÉS CABRERIZO Los premios Nobel de Química El campo de la Química que más premios ha recibido es el de la Quí- mica Orgánica. Frederick Sanger es el único laurea- do que ganó el premio en dos oca- siones, en 1958 y 1980. Otros dos también ganaron premios Nobel en otros campos: Marie Curie (física en El Premio Nobel de Química es entregado anual- 1903, química en 1911) y Linus Carl mente por la Academia Sueca a científicos que so- bresalen por sus contribuciones en el campo de la Pauling (química en 1954, paz en Física. 1962). Seis mujeres han ganado el Es uno de los cinco premios Nobel establecidos en premio: Marie Curie, Irène Joliot- el testamento de Alfred Nobel, en 1895, y que son dados a todos aquellos individuos que realizan Curie (1935), Dorothy Crowfoot Ho- contribuciones notables en la Química, la Física, la dgkin (1964), Ada Yonath (2009) y Literatura, la Paz y la Fisiología o Medicina. Emmanuelle Charpentier y Jennifer Según el testamento de Nobel, este reconocimien- to es administrado directamente por la Fundación Doudna (2020) Nobel y concedido por un comité conformado por Ha habido ocho años en los que no cinco miembros que son elegidos por la Real Aca- demia Sueca de las Ciencias. se entregó el premio Nobel de Quí- El primer Premio Nobel de Química fue otorgado mica, en algunas ocasiones por de- en 1901 al holandés Jacobus Henricus van't Hoff. clararse desierto y en otras por la Cada destinatario recibe una medalla, un diploma y situación de guerra mundial y el exi- un premio económico que ha variado a lo largo de los años.
    [Show full text]
  • PDF File, 2.06 MB
    Introduction Have you ever seen those little About the International Year of Crystallography pictures of a molecule of your The United Nations declares 2014 as the official International Year of prescribed medication? …or a drawing Crystallography. It commemorates not only the centennial of X-ray of DNA showing two strands winding Amoxicillin diffraction, which allowed the detailed study of crystalline material, but also the 400th anniversary of Kepler’s observation in 1611 of the What do around each other? symmetrical form of ice crystals, which began the wider study of the role Molecules are too small to be seen by of symmetry in matter. New Drug Design, normal microscopy. Learn more at http://iycr2014.org X-ray crystallography is one of the DNA Studies few techniques that can visualize them About IUCr The International Union of Crystallography is a not-for- and was used to determine the first Schematic picture profit, scientific organization that aims to: and molecular structures ever known. of DNA • promote international cooperation in crystallography • contribute to all aspects of crystallography X-rays X-rays & X-ray Crystallography • promote international publication of crystallographic research have in common? How They Work • facilitate standardization of methods, units, nomenclatures and symbols • form a focus for the relations of crystallography to other sciences • X-ray beams are shot through • We calculate how the diffracted a crystal composed of the X-rays would look, if they The IUCr fulfils these objectives by publishing
    [Show full text]
  • Meet the Scientist Linus Pauling (1901-1994)
    Meet the Scientist Linus Pauling (1901-1994) Do you know that different cells have certain unique proteins that have unique jobs? Muscles have proteins that contract, enabling the muscle cell to contract. Pancreas cells make the protein insulin, which regulates blood sugar levels. There are unique cells in the part of the brain called the hypothalamus that make small unique proteins that trigger the release of pituitary hormones. There are proteins in nerve cells that work to create new axon terminals and synapses that store your memories? How many other examples can you think of cells with specific proteins? A British journal included only Linus Pauling and Einstein from the 20th Century in their list of the greatest scientists in the history of the world. As you will see, Linus made major discoveries about chemical bonding and the structure of proteins―pretty heady stuff for a high-school dropout. He didn’t drop out because school was too hard. For him, it was too easy. Some scientists are born with a silver spoon in their mouth. But not Linus Pauling. From age 4 to 9, Linus lived in a small Oregon town, which was like an outpost in the Old West. The town had one street, lined by stores with false fronts on many of the buildings, as you see on cowboy movie sets today. Real cowboys lounged in front of the general store, and real Indians camped on the edge of town. His father, Herman, was a self-taught pharmacist and "medicine man." He ran a drug store in town.
    [Show full text]
  • Contributions of Civilizations to International Prizes
    CONTRIBUTIONS OF CIVILIZATIONS TO INTERNATIONAL PRIZES Split of Nobel prizes and Fields medals by civilization : PHYSICS .......................................................................................................................................................................... 1 CHEMISTRY .................................................................................................................................................................... 2 PHYSIOLOGY / MEDECINE .............................................................................................................................................. 3 LITERATURE ................................................................................................................................................................... 4 ECONOMY ...................................................................................................................................................................... 5 MATHEMATICS (Fields) .................................................................................................................................................. 5 PHYSICS Occidental / Judeo-christian (198) Alekseï Abrikossov / Zhores Alferov / Hannes Alfvén / Eric Allin Cornell / Luis Walter Alvarez / Carl David Anderson / Philip Warren Anderson / EdWard Victor Appleton / ArthUr Ashkin / John Bardeen / Barry C. Barish / Nikolay Basov / Henri BecqUerel / Johannes Georg Bednorz / Hans Bethe / Gerd Binnig / Patrick Blackett / Felix Bloch / Nicolaas Bloembergen
    [Show full text]
  • From the President New Program to Boost Membership
    July August 2011 · Volume 20, Number 4 New Program to From the President Boost Membership igma Xi’s new Member-Get-A-Member Dear Colleagues and Companions in Zealous Research program gives all active Sigma Xi It is indeed an honor for me to have been elected president of our Smembers a chance to earn a free year international honor society for scientists and engineers. Sigma Xi of membership by was created 125 years ago with high ideals, a worthy mission and recommending five an inspiring vision that remain critical to science and engineering in the 21st Century. new members during As incoming president, I will seek to further the mission of Sigma Xi. a one-year period. Public confidence in the fundamental truths derived from application of science is Active Sigma Xi members should perhaps more critical now than at any time in the history of our honor society. From recommend their qualified friends, students, openness in research to accuracy in conducting and reporting research to integrity in colleagues and fellow scientists and engineers the peer review process and authorship, we have an obligation to our members and the to the honor of Sigma Xi membership. Any public to focus on these issues. active Sigma Xi member who recommends I applaud my friend and colleague, our immediate past-president, Joe Whitaker. Dr. five new members who are then approved Whitaker deserves our gratitude for providing outstanding leadership and initiating for membership between now and June 30, a new hope for the evolution of our esteemed honor society. My intention will be to 2012 will receive one free year of Sigma Xi build upon the spark Joe ignited during his tenure, and implement an enabling strategy membership.
    [Show full text]
  • Manmohan Tells Scientists to Think Big and out of the Box India Will Soon Have Navaratna Universities, Says Sibal a Spectrum Reporter
    Special Edition January 3-7, 2011 The campus newspaper of SRM University Private Circulation only January 4, 2011 Volume IV Number II Manmohan tells scientists to think big and out of the box India will soon have Navaratna universities, says Sibal A Spectrum Reporter Maintaining the ideas of science and scientific research must always be linked to the betterment of the people of India, the Prime Minister of India, Dr. Manmohan Singh, called on the community to think ahead of the times. “The time has come for Indian Science Congress Indian science to once at SRM University. again think big; think The Prime Minister out of the box; and think argued that scientists ahead of the times. The should develop a code of time has come for India conduct on the application to produce the Ramans of their discovery. and Ramanujans of the 21st Century,” Dr. Singh “The question is whether said while delivering the scientists should step The Prime Minister releasing the Plenary Proceedings of the 98th ISC Inaugural Address of the 98th beyond their discipline and at least guide the modern nor liberal. It “This year, as we usher can never hope to extend social discourse on the use is true that products of in the New Year, we also the height of the pyramid of scientific knowledge. science have been put to usher in the ‘Decade of of excellence,” the Prime 2012-13 to be ‘Year Should they develop a code illiberal uses. I sincerely Innovation’. There is no Minister added. of conduct that defines believe we must guard better way to do that than Dr.
    [Show full text]
  • Francis Crick and the Structure of Helical Biomolecules
    1 A-DNA and B-DNA: Comparing their Historical X-Ray Fibre Diffraction Images. Amand A. Lucas Facultés Universitaires Notre-Dame de la Paix, 61 rue de Bruxelles, B5000 Namur, Belgium e-mail : [email protected] Abstract. A-DNA and B-DNA are two quite distinct molecular conformations which double stranded DNA drawn into a fibre can assume, depending on the water content of the fibre. The corresponding historic X-ray fibre diffraction diagrams, measured respectively by Wilkins and Gosling and by Franklin and Gosling in the early 1950’s, played an equally crucial role in the discovery of the double helical structure of the molecule by Watson and Crick in 1953. The purpose of the present paper is to provide a didactic and comparative explanation of the structural content of the two diagrams treated on the same footing. This will be accomplished by two methods. The first, intended for science students and professionals, relies on a basic introduction to helical diffraction theory. The second, accessible to a much wider readership, will make use of the optical transform method by which both A and B X-ray images can be simulated optically. The simulations are conducted with a simple laser pointer and a dozen optical diffraction gratings, all held on a single diffraction slide. The gratings have been specially designed to pinpoint just which of the structural element of the molecule is responsible for each of the revealing features of the fibre diffraction images. Keywords audience :general public, continuing education Domain : chemical education research, history, public understanding Pedagogy : hands-on learning, manipulative Topic : biophysical chemistry, conformational analysis, X-ray crystallography 1 2 A-DNA and B-DNA: Comparing their Historical X-Ray Fibre Diffraction Images.
    [Show full text]