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Photosystem I-Based Applications for the Photo-Catalyzed Production of Hydrogen and Electricity

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Photosystem I-Based Applications for the Photo-Catalyzed Production of Hydrogen and Electricity University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 12-2014 Photosystem I-Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity Rosemary Khuu Le University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Biochemical and Biomolecular Engineering Commons Recommended Citation Le, Rosemary Khuu, "Photosystem I-Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity. " PhD diss., University of Tennessee, 2014. https://trace.tennessee.edu/utk_graddiss/3146 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Rosemary Khuu Le entitled "Photosystem I- Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Chemical Engineering. Paul D. Frymier, Major Professor We have read this dissertation and recommend its acceptance: Eric T. Boder, Barry D. Bruce, Hugh M. O'Neill Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Photosystem I-Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Rosemary Khuu Le December 2014 Copyright © 2014 by Rosemary Khuu Le All rights reserved. ii DEDICATION This dissertation is dedicated to: my parents and brothers for their love, support, and fostering an environment for passion for science and discovery, my teachers and mentors who inspired and encouraged me to pursue science, and to the smart and strong women in my life – “Who run the world? Girls!” iii ACKNOWLEDGEMENTS I am deeply grateful for the support and encouragement from many people during my time at Tennessee. First, I would like to thank my advisor, Dr. Paul Frymier for his time, enthusiasm, constructive criticism, patience, trusting me to work independently, and philosophical conversations. I would also like to thank my committee members, Dr. Eric Boder, Dr. Barry Bruce, and Dr. Hugh O’Neill for their time, guidance, insightful ideas, and involvement in collaborative projects. I appreciate the assistance provided by Ifeyinwa Iwuchukwu, Prakitchai Chotewotmuntri, Richard Simmerman, and Khoa Nguyen in getting me acquainted with photosystem I. I also thank Maryam Raeeszadeh-Sarmazdeh for her guidance with sortase. I am also indebted to all of the undergrads (Carrie Lloyd, Donglee Shin, Stephanie Bailey, Anissa Goetz) who gave me their time and provided me with an extra set of hands with molecular cloning and protein purification. To Jane Breder, thank you for coordinating everything STAIR-related. To my labmates, Sustainabilabuddies, Supergroup family, and classmates, thank you for your friendship, commiseration, and teaching me new things. To my ‘Loe Down crew and Schmoopie, thank you for keeping me grounded, reminding me to be mindful, and for the love and support. I am forever grateful to my parents for instilling a strong work ethic in me and believing in me, which helped me stay persistent throughout my time at Tennessee, especially when research did not go as planned, and giving me all of the opportunities to be creative and learn. Finally, I gratefully acknowledge the financial support provided by the National Science Foundation’s IGERT STAIR program (DGE-0801470) and support from the University of Tennessee Sustainable Energy Education and Research Center (SEERC) that made this work possible. iv ABSTRACT The aim of this dissertation was to optimize systems integrating the photosystem I (PSI) redox protein, which is involved in photosynthesis, with noble metals for electron transfer to show its versatility: 1) in solution coupled with platinum to mediate hydrogen evolution and 2) on a planar gold surface for electricity production. Response surface methodology was utilized to study variables that affect hydrogen (H2) yield from platinized-PSI. Light intensity, temperature, and platinum concentration were varied during the platinum-photo-reduction process. Analysis of the effects of the variables on H2 yield allowed for determination of a condition for optimized hydrogen production: 240 μE/m2/s [micro-Einsteins per square meter per second] light intensity, 638 μM [micro-molar] platinum, and 31°C [degrees Celsius] temperature. A model was developed from an experimental solution space and predicted an optimum H2 yield of ~8.17 µmol H2/mg chl a/h [micro-mole hydrogen per milligram chlorophyll a per hour]. The model was validated by an 8.02 µmol H2/mg chl a/h value determined experimentally and platinum concentration had the greatest influence on H2 yield. Small-angle neutron scattering was used to investigate the solution structure of trimeric PSI from Thermosynechococcus elongatus in n-dodecyl-beta-D-maltoside (DDM) detergent to determine the orientation of the detergent molecules around PSI. The resulting PSI-DDM reconstruction structure showed the detergent oriented around the hydrophobic and interstitial periphery of the trimer in a non-uniform manner and did not agglomerate on the stromal or lumenal surfaces. Therefore, linkages to these faces are unlikely to be hindered by the presence of detergent. v Photo-activity has been observed from techniques attaching PSI to conductive surfaces. These techniques allow for dense deposition of the protein, but fail to control the orientation of PSI on the surface. The highly selective sortase-mediated ligation (SML) reaction was used to covalently attach PSI on tri-glycine functionalized gold surfaces. The exposed C-termini of PSI subunits from Synechocystis sp. PCC 6803 were targeted to study SML to control the orientation of PSI on gold for enhanced electron transfer, which yielded a 50% increase in current production from less than 100 nA/cm2 [nanoampere per square centimeter] to approximately 150 nA/cm2 compared to other monolayers. vi TABLE OF CONTENTS 1. INTRODUCTION .................................................................................................................. 1 1.1 Global Energy Crisis ............................................................................................................. 2 1.2 Photosynthesis and Photosystem I ........................................................................................ 4 1.2.1 The crystal structure of PSI from Thermosynechococcus elongatus as a surrogate for PSI from Synechocystis PCC 6803 ......................................................................................... 8 1.3 Scope of Work .................................................................................................................... 10 1.4 Applications utilizing photosynthetic reaction centers ....................................................... 12 1.4.1 Hydrogen production ................................................................................................... 13 1.4.1.1 Hydrogen Production via Traditional Metal Catalysts ...................................... 15 1.4.1.2 Hydrogenase-mediated Hydrogen Production ................................................... 17 1.4.2 Electricity production................................................................................................... 21 1.5 Neutron scattering ............................................................................................................... 26 1.5.1 Understanding the detergent structure for reconstituted PSI in solution ..................... 31 1.6 Sortase ................................................................................................................................. 32 2. OPTIMIZATION OF PHOTOSYNTHETIC HYDROGEN YIELD FROM PLATINIZED PHOTOSYSTEM I COMPLEXES USING RESPONSE SURFACE METHODOLOGY ......... 35 2.1 Introduction ......................................................................................................................... 36 2.2 Materials and Methods ........................................................................................................ 38 2.2.1 Growth of Thermosynechococcus elongatus ............................................................... 38 2.2.2 Isolation of trimeric PSI ............................................................................................... 38 2.2.3 PSI-mediated hydrogen evolution and measurement .................................................. 42 2.2.4 Screening experiments ................................................................................................. 43 2.2.5 Experimental design and data analysis ........................................................................ 44 2.3 Results and Discussion ....................................................................................................... 45 2.3.1 Screen Experiments ....................................................................................................
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