Article ID Journal Published Year Pages File Type
2052370 FEBS Letters 2006 5 Pages PDF
Abstract

The multiline signal of the S2 state in Photosystem II was measured both in frozen-solution and single-crystal preparations from the cyanobacterium Thermosynechococcus elongatus. The frozen-solution EPR spectrum shows a gaussian-like line shape without any resolution of Mn hyperfine couplings. This line shape can be understood on the basis of the single-crystal spectra, where a strong orientation dependence of partially resolved hyperfine structures appears. Simulation of the frozen-solution spectrum on the basis of Mn hyperfine couplings taken from published pulse-ENDOR data yields a fully rhombic g-matrix for the multiline signal with principal components 1.997, 1.970, and 1.965. The resulting isotropic g-value giso = 1.977 is surprisingly small compared to other manganese complexes containing manganese ions in the formal oxidation states three and four.

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