Photosystem II single crystals studied by EPR spectroscopy at 94 GHz: The tyrosine radical Yd

W. Hofbauer, A. Zouni, R. Bittl, J. Kern, P. Orth, F. Lendzian, P. Fromme, H. T. Witt, W. Lubitz

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Abstract

Electron paramagnetic resonance (EPR) spectroscopy at 94 GHz is used to study the dark-stable tyrosine radical YD 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 YD and related information on several proton hyperfine tensors are deduced from analysis of angular-dependent EPR spectra. The precise orientation of tyrosine YD in PS II is obtained as a first step in the EPR characterization of paramagnetic species in these single crystals.

Original languageEnglish
Pages (from-to)6623-6628
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume98
Issue number12
DOIs
Publication statusPublished - Jun 5 2001

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