The pump-probe spectral data matrices of reaction centers from Rhodobacter sphaeroides R26.1 and 2.4.1 in the 650-1265 nm region, that have been obtained by excitation of P at 868 nm with similar to 0.1 ps pulses, were analyzed by singular-value decomposition followed by global fitting by the use of a three-component sequential model. The species-associated difference spectra showed the P*BH -> P+B H -> P+BH sequential electron transfer and the rates of electron transfer were determined to be (1.9 ps) (1) and (2.7 ps) (1) for the first and the second steps, respectively. The P*BH reversible arrow P+B H reversible electron transfer was also identified. (C) 2010 Elsevier B.V. All rights reserved.