NDLI: Ca<sup>2+</sup> determines the entropy changes associated with the formation of transition states during water oxidation by Photosystem II

Content Provider	Royal Society of Chemistry (RSC)
Author	Ishida, Naoko Boussac, Alain Sugiura, Miwa Rappaport, Fabrice
Copyright Year	2011
Abstract	The role of Ca2+ in the Photosystem IIwater oxidation mechanism has been investigated in the higher redox states of the enzyme. The involvement of Ca2+ in structuring the environment of the tyrosine YZ in the S3 state has been investigated by studying the effect of a Ca/Sr exchange by pulse-EPR spectroscopy. It is shown that Ca and Yz are involved in a common hydrogen bond network in S3. The comparison of the temperature dependence of the rate of the water oxidation reaction shows that the slowdown of the S3YZ˙ → S0 transition in Sr-PSII mainly arises from a decrease of the entropic part of the ΔG# of the reaction. This suggests that Ca/Sr exchange perturbs the distribution of the conformational microstates and thereby hinders the overall water splitting process.
Starting Page	2520
Ending Page	2524
Page Count	5
File Format	HTM / HTML PDF
ISSN	17545692
Volume Number	4
Issue Number	7
Journal	Energy & Environmental Science
DOI	10.1039/c1ee01408k
Language	English
Publisher	Royal Society of Chemistry
Access Restriction	Open
Subject Keyword	Redox Enzyme Tyrosine Spectroscopy Hydrogen bond Correlation and dependence Water splitting
Content Type	Text
Resource Type	Article
Subject	Environmental Chemistry Pollution Renewable Energy, Sustainability and the Environment Nuclear Energy and Engineering

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Ca²⁺ determines the entropy changes associated with the formation of transition states during water oxidation by Photosystem II