B-A AND B-B ABSORBENCY PERTURBATIONS INDUCED BY COHERENT NUCLEAR MOTIONS IN REACTION CENTERS FROM RHODOBACTER-SPHAEROIDES UPON 30-FS EXCITATION OF THE PRIMARY DONOR

Subpicosecond oscillations in the B (accessory bacteriochlorophylls) b and were found in native and B-B-modified reaction centers from Rhodob acter sphaeroides R26 and of the mutant YM210W at 293 K using 30 fs ex citation pulses at 865 nm, The (30 +/- 3) and (12 +/- 2) cm(-1) modes were found to be enhanced with respect to the broad structure around 1 50 cm(-1) in all reaction centers (RC), The maximal amplitude of both modes is observed in native and B-B-modified RCs, while their minimal amplitude is registered in the YM210W mutant, in which the rate of ET is significantly decreased. In the presence of Q(A)(2-) new modes at 5 0 and 95 cm(-1) are observed, concomitant with a decrease of the 30 cm (-1) mode. These results are discussed in terms of the influence of pr otein motions, induced by the excitation of P, on the Q(Y) transition of B-A at 800 nm and their relation to the primary electron transfer.