Title:
Photosynthetic water oxidation and proton-coupled electron transfer

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dc.contributor.advisor Barry, Bridgette A.
dc.contributor.author Cooper, Ian Blake en_US
dc.contributor.committeeMember El-Sayed, Mostafa
dc.contributor.committeeMember Fahrni, Christoph
dc.contributor.committeeMember Kröger, Nils
dc.contributor.committeeMember McCarty, Nael
dc.contributor.department Chemistry and Biochemistry en_US
dc.date.accessioned 2009-01-22T15:58:41Z
dc.date.available 2009-01-22T15:58:41Z
dc.date.issued 2008-11-10 en_US
dc.description.abstract Photosystem II (PSII) is the membrane-bound oxidoreductase peptide complex responsible for the oxidation of water to molecular oxygen and reduction of plastoquinone to plastoquinol. Primary electron transfer is initiated upon absorption of a photon by the primary donor chl resulting in electron transfer and production of a P680+QA charge separated state. P680+ is reduced by YZ (Y161 of the D1 polypeptide subunit), one of two redox-active tyrosine residues found in PSII. This produces a neutral tyrosyl radical (YZ ) which is subsequently reduced by electrons derived from water at the oxygen-evolving complex (OEC). The OEC is composed of four manganese, one calcium ion, and one chloride ion. Four photons are required to convert water to O2, each photon advancing the OEC through successive oxidation states or S states. The exact chemical mechanism of water oxidation in PSII is not known. However, proton-coupled electron transfer (PCET) is thought to be one of the fundamental steps in driving the extraction of electrons and protons from water. Here, the mechanism of water oxidation is investigated with focus on PCET events using vibrational spectroscopy. Vibrational spectroscopy is sensitive to changes in protein structure, charge, and hydrogen bonding, and is ideal for the study of fast events coupled with light-induced electron transfer. The results presented here demonstrate the utility of time-resolved infrared spectroscopy in the detection of intermediates of photosynthetic water oxidation. We suggest that proton transfer may precede manganese oxidation during water oxidation based on time-resolved infrared and difference FT-IR spectroscopic results. The mechanism of PCET associated with YZ reduction is investigated. Using reaction-induced difference FT-IR spectroscopy, the identity of the chloride binding site is speculated through the use of bromide exchange at the OEC. Also, proton transfer reactions at the OEC are investigated using azide as a vibrational probe. The advances in the understanding of photosynthetic water oxidation gained in this work will aid in the elucidation of the chemical mechanism of this important reaction. Understanding the details of photosynthetic water oxidation will assist in the development of technology aimed at harnessing the energy of the sun for the benefit of humankind. en_US
dc.description.degree Ph.D. en_US
dc.identifier.uri http://hdl.handle.net/1853/26707
dc.publisher Georgia Institute of Technology en_US
dc.subject Water oxidation en_US
dc.subject Photosystem II en_US
dc.subject Photosynthesis en_US
dc.subject Tyrosine en_US
dc.subject Chloride en_US
dc.subject Vibrational spectroscopy en_US
dc.subject.lcsh Charge exchange
dc.subject.lcsh Oxidation-reduction reaction
dc.subject.lcsh Photosynthesis Molecular aspects
dc.subject.lcsh Proton transfer reactions
dc.title Photosynthetic water oxidation and proton-coupled electron transfer en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Barry, Bridgette A.
local.contributor.corporatename School of Chemistry and Biochemistry
local.contributor.corporatename College of Sciences
relation.isAdvisorOfPublication 3398b34c-4658-496b-84ec-43b16a2007e0
relation.isOrgUnitOfPublication f1725b93-3ab8-4c47-a4c3-3596c03d6f1e
relation.isOrgUnitOfPublication 85042be6-2d68-4e07-b384-e1f908fae48a
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