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A Comparison of the Manganese Center Responsible for Photosynthetic Water Oxidation in O 2 ‐Evolving Core Particles and Photosystem II Enriched Membranes: EPR of the S 2 State
Author(s) -
Sivaraia M.,
Charles Dismukes G.
Publication year - 1988
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198800019
Subject(s) - chemistry , photosystem ii , electron paramagnetic resonance , photosynthetic reaction centre , manganese , oxygen evolving complex , membrane , spinach , photochemistry , oxidation state , redox , crystallography , photosynthesis , analytical chemistry (journal) , electron transfer , inorganic chemistry , nuclear magnetic resonance , catalysis , biochemistry , physics , organic chemistry , chromatography
We have characterized the electron donors to Photosystem II (PS II) in an O 2 ‐evolving reaction center core preparation from spinach (Ghanotakis, D.F.; Yocum, C.F. FEBS Lett. , 1986, 197 : 244–248) using EPR spectroscopy of the manganese center involved in water oxidation and of the tyrosine donor responsible for signal II. Both the 16‐line and the 19‐line form of the S 2 multiline EPR signal can be observed in the core particles under conditions similar to those which produce these signals in PS II membranes. Consequently, the structure of the coupled cluster of three or four Mn ions remains intact in the core particles. The Kok parameters which characterize the number of reaction centers capable of advancing by 0, 1, or 2 equivalents in response to a short laser pulse are found to be the same in PS II membranes and in the core particles. Also, there is no evidence for partially inactivated centers which reach the S 2 or S 3 states, but which do not advance to O 2 release. Thus the new class of highly resolved O 2 ‐evolving particles appears to be well suited for biophysical studies directed at the mechanism of water oxidation.