Premium
Asymmetric binding of the primary acceptor quinone in reaction centers of the photosynthetic bacterium Rhodobacter sphaeroides R26, probed with Q‐band (35 GHz) EPR spectroscopy
Author(s) -
van den Brink Johan S.,
Spoyalov Andrej P.,
Gast Peter,
van Liemt Willem B.S.,
Raap Jan,
Lugtenburg Johan,
Hoff Arnold J.
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)01047-1
Subject(s) - rhodobacter sphaeroides , photosynthetic reaction centre , quinone , electron paramagnetic resonance , semiquinone , chemistry , photochemistry , purple bacteria , electron acceptor , spectroscopy , acceptor , hyperfine structure , electron transfer , photosynthesis , stereochemistry , nuclear magnetic resonance , atomic physics , physics , biochemistry , quantum mechanics , condensed matter physics
The reaction center (RC)‐bound primary acceptor quinone Q A of the photosynthetic bacterium Rhodobacter sphaeroides R26 functions as a one‐electron gate. The radical anion Q •− A is proposed to have an asymmetric electron distribution, induced by the protein environment. We replace the native ubiquinone‐10 (UQ10) with specifically 13 C‐labelled UQ10, and use Q‐band (35 GHz) EPR spectroscopy to investigate this phenomenon in closer detail. The direct observation of the 13 C‐hyperfine splitting of the g z ‐component of UQ10 •− A in the RC and in frozen isopropanol shows that the electron spin distribution is symmetric in the isopropanol glass, and asymmetric in the RC. Our results allow qualitative assessment of the spin and charge distribution for Q •− A in the RC. The carbonyl oxygen of the semiquinone anion nearest to the S = 2 Fe 2+ ‐ion and Q B is shown to acquire the highest (negative) charge density.