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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
19
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pubmed:dateCreated |
1991-6-20
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pubmed:abstractText |
A new intermediate in the water-oxidizing reaction has been observed in spinach photosystem II (PSII) membranes that are depleted of Ca2+ from the site which is conformationally coupled to the manganese cluster comprising the water-oxidizing complex (WOC). It gives rise to a recently identified EPR signal (symmetric line shape with width 163 +/- 5 G, g = 2.004 +/- 0.005), which forms in samples inhibited either by depletion of Ca2+ [Boussac, A., Zimmerman, J.-L., & 28, 8984-8989; Sivaraja, M., Tso, J., & Dismukes, G.C. (1989) Biochemistry 28 9459-9464] or by substitution of Cl- by F- (Baumgarten, Philo, and Dismukes, submitted for publication). Further characterization of this EPR signal has revealed the following: (1) it forms independently of the local structure of the PSII acceptors; (2) it arises from photooxidation of a PSII species that donates an electron to Tyr-Z+ or to the Mn cluster in competition with an exogenous donor (DPC); (3) the Curie temperature dependence of the intensity suggests an isolated doublet ground state, attributable to a spin S = 1/2 radical; (4) the electron spin orientation relaxes 1000-fold more rapidly than typical for a free radical, exhibiting a strong temperature dependence of P1/2 (half-saturation power approximately T3.4) and a broad inhomogeneous line width; (5) it yields an undetectable change in the magnetic susceptibility upon formation by a laser flash; (6) it disappears in parallel with release of Mn during reduction with NH2OH, indicating that it forms only in the presence of the modified Mn cluster. (ABSTRACT TRUNCATED AT 250 WORDS)
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pubmed:grant | |
pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Calcium,
http://linkedlifedata.com/resource/pubmed/chemical/Photosynthetic Reaction Center...,
http://linkedlifedata.com/resource/pubmed/chemical/Photosystem II Protein Complex,
http://linkedlifedata.com/resource/pubmed/chemical/Plant Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/Water
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pubmed:status |
MEDLINE
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pubmed:month |
May
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pubmed:issn |
0006-2960
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:day |
14
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pubmed:volume |
30
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
4740-7
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pubmed:dateRevised |
2007-11-14
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pubmed:meshHeading |
pubmed-meshheading:1851436-Calcium,
pubmed-meshheading:1851436-Electron Spin Resonance Spectroscopy,
pubmed-meshheading:1851436-Magnetics,
pubmed-meshheading:1851436-Oxidation-Reduction,
pubmed-meshheading:1851436-Photochemistry,
pubmed-meshheading:1851436-Photosynthetic Reaction Center Complex Proteins,
pubmed-meshheading:1851436-Photosystem II Protein Complex,
pubmed-meshheading:1851436-Plant Proteins,
pubmed-meshheading:1851436-Temperature,
pubmed-meshheading:1851436-Water
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pubmed:year |
1991
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pubmed:articleTitle |
Ca2+ depletion from the photosynthetic water-oxidizing complex reveals photooxidation of a protein residue.
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pubmed:affiliation |
Department of Chemistry, Hoyt Laboratory, Princeton University, New Jersey 08544.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.
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