期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2001
卷号：98
期号：12
页码：6623-6628
DOI：10.1073/pnas.101127598
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Electron paramagnetic resonance (EPR) spectroscopy at 94 GHz is used to study the dark-stable tyrosine radical Y[IMG]f1.gif" ALT="Formula" BORDER="0"> in single crystals of photosystem II core complexes (cc) isolated from the thermophilic cyanobacterium Synechococcus elongatus. These complexes contain at least 17 subunits, including the water-oxidizing complex (WOC), and 32 chlorophyll a molecules/PS II; they are active in light-induced electron transfer and water oxidation. The crystals belong to the orthorhombic space group P212121, with four PS II dimers per unit cell. High-frequency EPR is used for enhancing the sensitivity of experiments performed on small single crystals as well as for increasing the spectral resolution of the g tensor components and of the different crystal sites. Magnitude and orientation of the g tensor of Y[IMG]f1.gif" ALT="Formula" BORDER="0"> and related information on several proton hyperfine tensors are deduced from analysis of angular-dependent EPR spectra. The precise orientation of tyrosine Y[IMG]f1.gif" ALT="Formula" BORDER="0"> in PS II is obtained as a first step in the EPR characterization of paramagnetic species in these single crystals.
