title: Structural organization in photosynthetic proteins as studied by high-field EPR of spin-correlated radical pair states.
abstract: We demonstrate the potential of high-field (HF) time-resolved electron paramagnetic resonance (EPR) spectroscopy to reveal unique information about electron transfer processes and the structure of photosynthetic systems. The lineshapes and electron spin polarization (ESP) of spin-correlated radical pair (SCRP) spectra recorded with HF-EPR are very sensitive to the magnetic parameters, interactions, and geometry of the radicals in the pair. This sensitivity facilitates an analysis of more sophisticated models and methods to reveal the important relationship between structural organization and light-induced electron transfer of the photosynthetic proteins. In this review, we report on a new time-resolved HF and multi-frequency EPR approach developed in the Freiburg laboratory in cooperation with the Argonne Photosynthesis group. The method is designed to probe the geometric structure of charge separated states in the photosynthetic membrane. First, we discuss the magneto-orientation of photosynthetic cyanobacteria as revealed by time-resolved HF-EPR of SCRPs. Then, we demonstrate how the three-dimensional structure of the SCRP P700(+)A1 from photosystem I of oxygenic photosynthesis and its arrangement in the membrane is obtained from application of multi-frequency including time-resolved HF-EPR techniques.
authors.affiliation: Department of Physical Chemistry, University of Freiburg, Albertstr. 21, D-79104 Freiburg, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Link
authors.forename: Oleg G
authors.initials: OG
authors.lastname: Poluektov
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Utschig
authors.forename: Jacques
authors.initials: J
authors.lastname: Lalevée
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Yago
authors.forename: Joerg-Ulrich
authors.initials: JU
authors.lastname: Weidner
authors.forename: Marion C
authors.initials: MC
authors.lastname: Thurnauer
authors.forename: Gerd
authors.initials: G
authors.lastname: Kothe
mesh_terms: D000458:Cyanobacteria / Q000201:enzymology / Q000648:ultrastructure; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D005609:Free Radicals / Q000737:chemistry; D008280:Magnetics; D008854:Microscopy, Electron; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D005609:Free Radicals; D045322:Photosynthetic Reaction Center Complex Proteins