The study of the state [P870 + B800 −] in bacterial reaction centers by selective picosecond and low-temperature spectroscopies

Abstract

The selective picosecond excitation of Rhodopseudomonas sphaeroides (R-26) reaction centers (RCs) at 870 nm induces the formation of the transient state within <1 ps followed by the conversion into the state P F (P ± Bph ±− during 7 ± 2 ps at both 293 K and 110 K. The transient state including the intense bleaching at 800 nm has been shown not to be due: (a) to photon excitation at 870 nm; (b) the excitation of P +; (c) photoselection effects. The transient state is interpreted as the state 1[P +B −] in agreement with earlier works. The primary formation of the state 1P +B −] and the big effective singlet-triplet splitting in this state correspond to the spectral splitting of the P band at 900 nm in R-26 RCs and at 1000 nm in Rhodopseudomonas viridis RCs found at 4.2 K and attributed to the optical transition to both 1P and 1[P +B −] states.