Light-induced structural changes in photosynthetic reaction centres studied by ESEEM of spin-correlated D+QA- radical pairs.
Zn-substituted Rhodobacter sphaeroides R26 reaction centres (RCs) frozen in the dark and under illumination exhibit quite different recombination kinetics of the D+QA- radical pairs [Kleinfeld et al., Biochemistry, 23 (1984) 5780]. We have applied electron spin echo envelope modulation (ESEEM) of the spin-correlated D+QA- radical pairs to assess a possible light-induced change in the distance between the D and QA cofactors. The recombination kinetics and the field-swept spin-polarized EPR signal for the two preparations have been monitored by time-resolved EPR spectroscopy. For the samples frozen under illumination, a slight increase in the distance, 0.4+/-0.2 A, has been detected.
Borovykh
I V
IV
Department of Biophysics, Huygens Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, Netherlands.
Dzuba
S A
SA
Proskuryakov
I I
II
Gast
P
P
Hoff
A J
AJ
D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D008027:Light; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D012242:Rhodobacter sphaeroides / Q000737:chemistry*
D045322:Photosynthetic Reaction Center Complex Proteins