Photoselection effects in laser flash-induced spin-polarised EPR spectra of the radical pair state [P(+)Q(A)(-)] in Rhodobacter sphaeroides reaction centers

The spin-polarised EPR signal of the radical pair state [P+ Q(A)(-) ] in Zn -substituted Rhodobacter sphaeroides R26 reaction centers demonstrates a st rong dependence on the wavelength and polarisation of the excitation light. This dependence is attributed to photoselection by the plane-polarised las er light utilised in the experiments. The model of spin-correlated radical pairs describes the experimental results well if the effect of photoselecti on is taken into account. (C) 1999 Elsevier Science B.V. All rights reserve d.