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Single Crystal Electron Spin Resonance Studies of the Photochemical Reaction Center from Rhodobacter sphaeroides Wild Type Strain 2.4.1
Author(s) -
Budil David E.,
Taremi Shahriar S.,
Gast Peter,
Norris James R.,
Frank Harry A.
Publication year - 1988
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198800013
Subject(s) - rhodobacter sphaeroides , chemistry , crystallography , electron paramagnetic resonance , resonance (particle physics) , photosynthetic reaction centre , crystal (programming language) , nuclear magnetic resonance , electron transfer , atomic physics , photochemistry , physics , biochemistry , photosynthesis , computer science , programming language
Abstract Single crystals were obtained from the photochemical reaction center protein of the photosynthetic bacterium Rhodobacter sphaeroides wild type strain 2.4.1. At low temperatures, the crystals display pronounced anisotropy in their triplet state electron spin resonance (ESR) spectra. An analysis of the angle dependence of the resonance field positions revealed two to four magnetically nonequivalent primary donor molecules per unit cell. This is consistent with the symmetry assignment of P 2 1 2 1 2 1deduced from previous X‐ray diffraction studies (Frank, H.A.; Taremi, S.S.; Knox, J.R. J. Mol. Biol. , 1987, 198 : 139–141). However, the ESR data could not be fit assuming that the unit cell axes coincide with the crystal morphological axes as was the case previously for Rb. sphaeroides R26 (Gast, P.; Norris, J.R. FEBS Lett. , 1984, 177 : 277–280). In order to explain the present data, it was necessary to assume a rhombic crystal cross‐section with the unit cell axes lying along the diagonals of the rhombus. The unit cell axes b and c were found to make angles of 60 ± 2° and 30 ± 2°, respectively, with one of the faces of the crystal. The orientation of the triplet state dipolar tensor axes relative to the unit cell axes differs slightly from that in Rb. sphaeroides R26 crystals, suggesting that the Rb. sphaeroides 2.4.1 reaction center is rotated by approximately 7° relative to the orientation found in Rb. sphaeroides R26.