DYNAMICS OF THE EXCITED-STATE OF THE PRIMARY ELECTRON-DONOR IN REACTION CENTERS OF RHODOPSEUDOMONAS-VIRIDIS AS REVEALED BY HOLE BURNING AT 1.7K - DIFFERENT CONFORMATIONAL STATES

The spectra of absorbance changes (DELTA-A) due to the formation of P+Q- (P, primary electron donor, Q, primary quinone acceptor) at 1.7K in Rhodopseudomonas viridis reaction centers (RCs) excited at 1014 nm has been shown to include, besides a progression of broad (170-190 cm-1) Gaussian vibronic bands separated by 150 cm-1, a 'narrow' structure near 1014 nm which can be simulated by a Lorentian zero-phonon hole (ZPH) and Lorentian one-mode (26.8 cm-1) phonon wings. The widths of ZPH of almost-equal-to 17 cm-1 for DELTA-A reflecting the formation of P+Q- decaying in the ms time domain and of 6.8 +/- 0.4 cm-1 for P+Q- decaying in the min time domain at 1.7K, seems to correspond to different conformations of RCs with a relaxation time of P* of almost-equal-to 0.6 ps (in agreement with measurements in this time domain) and 1.6 +/- 0.1 ps, respectively. The comparison of the spectra of DELTA-A in the region of the B(L) band for slow (min) and fast (ms) decaying components suggests a different mutual arrangement of P and B(L) for different conformations of RCs. It is assumed that the broad and narrow structures of the P band reflect the transitions to two configurations with different P-protein interactions. 'Narrow' structure of DELTA-A spectrum with essentially the same phonon wings and ZPH (width of 3.8 +/- 0.4 cm-1) was observed within the P band when H(L) was photoreduced at 1.7K.