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M.S. thesis Yanchen Hu.pdf (2.12 MB)

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Investigation of Electron Transfer and Solvation Dynamics in (6-4) Photolyase

Hu, Yanchen
http://rave.ohiolink.edu/etdc/view?acc_num=osu1437754218

Abstract Details

2015, Master of Science, Ohio State University, Chemistry.
Electron transfer is involved in many enzymes which play crucial roles of a variety of biological functions. Mechanism of biological ET, especially construction of related theoretical models, has been investigated for around 40 years. A consensus has been reached that high efficiency ET in biomolecules is generally barrierless owing to their optimized structures and energetics through natural evolution. Among all biological ET processes, photoinduced ET (PET) has been intensely studied in photosynthetic systems and flavoproteins. These PET processes have been recognized to occur in non-equilibrium with dynamic solvation relaxation of excited-state cofactors and thus cannot be modelled by Marcus theory. Efforts on incorporation of solvation dynamics into ET rate theories have been made to account for experiment results, while experimental and computational studies, in turn, have been carried out to test the applicability of various theoretical models. So far, reaction-diffusion model, which was proposed for the first time by Sumi and Marcus, has been successfully used in photosynthetic systems to study dependence of non-ergodic PET on reaction free energy and reorganization energy. However, appropriateness of this model to account for temperature effect on ET rate, especially ET profile in cryogenic range, is still controversial. Solvation dynamics in a broad temperature range from room temperature to 77.5K were studied by measuring steady-state and time-resolved fluorescence of the reduced cofactor FADH- of (6-4) photolyase WT and H364A mutant. Steady-state emission spectra confirms that two major peaks arise from vibronic bands rather than from isomers due to the third peak which stands out at lower temperatures. Solvation correlation function extracted from time-resolved emission spectra reveals a relaxation process through protein active-site collective motion, which, in H364A, occurs in hundreds of picoseconds at high temperatures and slows down to nanosecond timescale at 210.5K and below. Electron transfer dynamics were fit with stretched exponential decay model. ET from FADH-* to adenine and to (6-4) photoproduct both show dichotomy of activation barrier throughout the whole temperature scale, whose mechanism, however, is still unknown. For the latter intermolecular ET, the transition in the stretching coefficient ß before and after 230K shows different mechanisms to the heterogeneity in H364A dynamics.
Dongping Zhong, Dr. (Advisor)
Sherwin Singer, Dr. (Committee Member)
63 p.
Biochemistry; Biophysics; Physical Chemistry
photolyase; solvation correlation function; electron transfer; temperature dependence

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Citations

  • Hu, Y. (2015). Investigation of Electron Transfer and Solvation Dynamics in (6-4) Photolyase [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437754218

    APA Style (7th edition)

  • Hu, Yanchen. Investigation of Electron Transfer and Solvation Dynamics in (6-4) Photolyase. 2015. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1437754218.

    MLA Style (8th edition)

  • Hu, Yanchen. "Investigation of Electron Transfer and Solvation Dynamics in (6-4) Photolyase." Master's thesis, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437754218

    Chicago Manual of Style (17th edition)

osu1437754218
489
© 2015, some rights reserved.Creative Commons License Investigation of Electron Transfer and Solvation Dynamics in (6-4) Photolyase by Yanchen Hu is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by The Ohio State University and OhioLINK.