1.5. Raman Spectroscopy
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Open Research Online The Open University’s repository of research publications and other research outputs Characteristic Raman Bands of Amino Acids and Halophiles as Biomarkers in Planetary Exploration Thesis How to cite: Rolfe, Samantha (2017). Characteristic Raman Bands of Amino Acids and Halophiles as Biomarkers in Planetary Exploration. PhD thesis The Open University. For guidance on citations see FAQs. c 2016 The Author https://creativecommons.org/licenses/by-nc-nd/4.0/ Version: Version of Record Link(s) to article on publisher’s website: http://dx.doi.org/doi:10.21954/ou.ro.0000c66a Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online’s data policy on reuse of materials please consult the policies page. oro.open.ac.uk Characteristic Raman Bands of Amino Acids and Halophiles as Biomarkers in Planetary Exploration Samantha Melanie Rolfe MPhys (Hons), University of Leicester, 2010 September 2016 The Open University School of Physical Sciences A THESIS SUBMITTED TO THE OPEN UNIVERSITY IN THE SUBJECT OF PLANETARY SCIENCES FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Acknowledgements To my parents, Mark and Melanie, and my brother, Alex, who have always supported and encouraged me to follow my dreams and overcome all and any obstacles to achieve them. To my grandparents, Anthony and Margery Wilson, Aubrey and Val Rolfe and Marjorie and Russell Whitmore, this work is dedicated to you. To Chris, my rock, without you I absolutely would not have been able to get through this process. I would have had no clean clothes or fresh vegetables in my diet. You know how much you mean to me, you are my best friend and your support means more to me than you can know. To Manish, Karen, Iain and Tim, my supervisors, thank you for your guidance and instruction, especially on a multi-disciplinary project, where you taught me analytical techniques and skills, and entirely new to me, microbiology. I could not have done this without you. Regardless of your walk of life - to those who may not realise their mental health is suffering, every now and then take a moment to look up the symptoms of depression and if you fit any of them, I encourage you to get help. Do not suffer alone. Thank you to my examiners, Susana Jorge-Villar and Monica Grady, who made my viva examination an enjoyable experience after a nerve-wracking build-up. Unending thanks goes to Mabs Gilmour for help with many hours of GCMS analysis that did not make it into this thesis, but from whom I learned a lot, plus instruction on chemical preparation of samples, and, most importantly, general but necessary support – I could not have got through this without you. i Thank you to Simona Nicoara for help with GCMS analysis, Marc Davies for help with basalt powder preparation, Michelle Higgins for basalt thin section preparation and chips of basalt, Stephen Summers for extensive tutoring on microbiology work and confocal microscopy, Sasha Verchovsky for custom glass work, Diane Johnson for conducting FIB-SEM imaging, Heather Davis for preparing and conducting TEM images, and Igor Kraev for information about the TEM sample preparation process, Gordon Imlach for FEG-SEM imaging (unfortunately, this work did not go to plan), and Karen Guyler and Beverley Bishop for their support and help. To my colleagues and support base: Jon Mason, Euan Monaghan, Dan Dawson, Adam Stevens, Feargus Abernethy, Felicity Williams, Kathryn McDermott, Michael Goodyear, Jess Barnes, Rebecca Wolsey, Elliot Curtis-Harper, Pete Landsberg, Ben Dryer, Phillipa Smith and the other CEI residents, JD Bodenan, Mohit Melwani Daswani, Natalie Starkey, Louisa Preston, Tom Barrett, Roy Adkin, Zoë Ellery, Alex Barrett, Helen Davidge, Beth Steer, Ian Franchi, Sally Jordan, Terry McGenity, Lewis Dartnell – thank you for your friendship and help and collaboration and I wish the you all the best for the future. To everyone in the Science Department at Beaumont School, but especially Karen, Caroline and Rathi, you are all so fabulous and dedicated, I have nothing but the greatest respect for you all and I miss working with you every day. To my neglected friends, you know who you are, those I have known many years and those who I have recently got to know. You have stood by me and put up with diminished communications but were always there for me when I did get in contact, after many weeks or months of radio silence. I love you and I am so grateful for you being in my life. ii N.B. As mentioned in Section 1.2.3, the term biomarker, biosignature and bioindicator are interchangeable. However, since beginning this PhD project, biomarker and biosignature now have more well-defined uses. At the time of publication, the term ‘biosignature’ refers to evidence for life, extant or extinct; whereas ‘biomarker’ is more readily used in medicine as indicators of disease and by geologists and geochemists when analysing molecular fossils in crude oils and petroleum. Due to historical definitions biomarker is used throughout this thesis, however, it is recommended that biosignature is used in future astrobiology-related writing. iii iv Abstract Evaporitic environments that could provide habitats for life exist on present day Mars, in addition to Recurring Slope Lineae (RSL), which have been observed suggesting a briny liquid in the subsurface with a seasonal occurrence at the surface. Life detection is the focus for future missions, including use of the Raman Laser Spectrometer (RLS) instrument on board the ESA ExoMars rover for this purpose. Martian simulation chambers were used to expose a subset of the α-amino acids (AA) and halophilic (‘salt-loving’) microbes to the surface and near surface environment. Post-exposure, the detectability of biological molecules with Raman spectroscopy (where the Raman spectrum is the biomarker) was examined, with the intention to inform future missions. Results from this work suggest that a statistical method (independent of band intensity) should be used to rigorously define a set of characteristic Raman bands to unambiguously identify AA, a technique applicable to all biomolecules. Following exposure, both AA and halite entombed archaeal halophiles survived a combination of simulated martian conditions, e.g. freeze-thaw cycling resulted in a maximum of 20 % biomarker signal loss for AA. Halophilic microbes survived UV exposure up to 3.5 sols, though with a complete biomarker signal loss. However, cell counts and hence, survival in near surface, freeze-thaw conditions (indicative of RSL conditions) remained similar to the control sample. Furthermore, the Raman biomarker signal remained intact and detectable, regardless of a reduced intensity. Importantly, for AA doped onto crushed basalt the Raman band biomarkers were lost, which has major implications for the ExoMars rover which will crush rock samples before examination with the RLS instrument. Future missions should be designed to examine samples with the Raman spectroscopy instrument prior to any crushing to avoid destroying the biomarker signal that could be used to imply the presence of life. v vi Publications As a result of this work the following manuscript was accepted for publication, upon which Chapter 3 is based: Rolfe, S. M.; Patel, M. R.; Gilmour, I.; Olsson, K. and Ringrose, T. J. (2016) Defining Multiple Characteristic Raman Bands of α-Amino Acids as Biomarkers for Planetary Missions Using a Statistical Method. Origins of Life and Evolution of Biospheres, 46, 323-346. The following are conference presentations given as a result of work conducted throughout this study: Rolfe, S. M.; Patel, M. R.; Gilmour, I.; Olsson, K. and Ringrose, T. J. (2013). Detecting biomarkers on Mars using Raman spectroscopy. In: Molecules and Life in Extremes: UK Astrobiology Conference 2013 - (ASB5), 17-19 April 2013, Edinburgh, UK. Rolfe, S. M.; Patel, M.; Gilmour, I.; Olsson, K.; Ringrose, T. J. and Cockell, C. (2012). Raman spectroscopy of biologically relevant amino acids under martian conditions. In: Astrobiology Science Conference 2012 Exploring Life: Past, Present, Near and Far, 16-20 April 2012, Atlanta, GA, USA. Rolfe, S. M.; Patel, M. R.; Olsson, K.; Cockell, C. S. and Ringrose, T. J. (2011). Raman spectroscopy of amino acids and other biomarkers on Mars. In: 11th European Workshop on Astrobiology (Annual workshop of EANA), 11 - 14 July 2011, Cologne, Germany (poster). Rolfe, S. M.; Patel, M. R.; Ringrose, T. J. and Leese, M. R. (2011). Planetary simulation and hypervelocity impact at the Open University. In: Exploring Mars Habitability, 13-15 June 2011, Lisbon, Portugal (poster). vii Contents Acknowledgements ................................................................................................................. i Abstract .................................................................................................................................. v Publications .......................................................................................................................... vii Contents .............................................................................................................................. viii List of Figures ...................................................................................................................... xii List of Tables ...................................................................................................................... xxi List of Abbreviations .......................................................................................................