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The nature of the Fe(III) EPR signal from the acceptor‐side iron in photosystem II
Author(s) -
Aasa Roland,
Andréasson Lars-Erik,
Styring Stenbjörn,
Vänngård Tore
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)80120-6
Subject(s) - electron paramagnetic resonance , photosystem ii , chemistry , acceptor , photosynthetic reaction centre , photochemistry , crystallography , photosystem i , p680 , nuclear magnetic resonance , photosynthesis , electron transfer , physics , biochemistry , condensed matter physics
The EPR spectrum at both X‐ and S‐band (3.94 GHz) of the oxidized acceptor‐side iron in photosystem II from spinach shows two absorption‐type peaks at g = 8.0 and 5.6. The intensities of these peaks have been measured at X‐band in the temperature range 2–10 K. All results can be fully described assuming that the EPR spectrum arises from high‐spin Fe(III) with D = 1.0±0.3 cm −1 and E / D = 0.10 ±0.01. Quantifications show that the spectrum in our case represents 0.4–0.5 Fe(III) per reaction center. The EPR parameters are consistent with the iron having bicarbonate and/or tyrosine as ligands in addition to four imidazoles.