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LIGHT‐INDUCED FOURIER TRANSFORM INFRARED SPECTROSCOPIC INVESTIGATIONS OF THE INTERMEDIARY ELECTRON ACCEPTOR REDUTION IN BACTERIAL PHOTOSYNTHESIS
Author(s) -
Nabedryk E.,
Mäntele W.,
Tavitian B. A.,
Breton J.
Publication year - 1986
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1986.tb05630.x
Subject(s) - chemistry , absorbance , fourier transform infrared spectroscopy , photochemistry , infrared , amide , acceptor , sodium dithionite , rhodobacter sphaeroides , infrared spectroscopy , photosynthesis , organic chemistry , chromatography , biochemistry , physics , quantum mechanics , optics , condensed matter physics
— Molecular changes associated with the light‐induced reduction of the intermediary electron acceptor I (bacteriopheophytin, BPh) in bacterial photosynthesis were studied by means of Fourier transform infrared (FTIR) difference spectroscopy. Chromatophore membranes and reconstituted reaction centers (RCs) of Rhodopseudomonas viridis were prereduced with sodium dithionite and illuminated in order to trap photochemically the state I − . Fourier transform infrared spectra of these samples were recorded before, during and after illumination, with an accuracy better than 10 −3 absorbance units. Difference spectra of I − in chromatophores and in RCs closely correspond to each other. In the carbonyl stretching frequency region between 1640 and 1750 cm −1 , bands are tentatively attributed to a shift (from 1713 to 1683 cm −1 ) of a keto carbonyl group, a change of an acetyl carbonyl grou at 1656 cm −1 and a decrease in absorbance strength of ester carbonyl groups (at 1746 and 1732 cm − P) after reduction of I. These groups likely belong to the BPh molecule, although at least one of the ester carbonyls could be assigned to an amino acid side chain. The absence of strong bands in the amide I and amide II region excludes large protein conformational changes associated with I reduction.