title: 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.
abstract: 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 approximately 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 approximately 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 BL band for slow (min) and fast (ms) decaying components suggests a different mutual arrangement of P and BL 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 HL was photoreduced at 1.7K.
authors.affiliation: Institute of Soil Sciences and Photosynthesis, USSR Academy of Sciences, Pushchino.
authors.lastname: Shkuropatov AYa
authors.forename: A O
authors.initials: AO
authors.lastname: Ganago
authors.forename: V A
authors.initials: VA
authors.lastname: Shuvalov
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology; D001429:Bacteriochlorophylls / Q000378:metabolism; D004579:Electron Transport; D005292:Ferricyanides / Q000494:pharmacology; D008027:Light; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D011809:Quinones / Q000378:metabolism; D012241:Rhodopseudomonas / Q000378:metabolism*; D013053:Spectrophotometry
chemical_list: D001429:Bacteriochlorophylls; D005292:Ferricyanides; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D011809:Quinones; C007931:hexacyanoferrate III; D001205:Ascorbic Acid