title: Attenuated total reflection Fourier transform infrared spectroscopy of redox transitions in photosynthetic reaction centers: comparison of perfusion- and light-induced difference spectra.
abstract: Chemically induced Fourier transform infrared difference spectra associated with redox transitions of several primary electron donors and acceptors in photosynthetic reaction centers (RCs) have been compared with the light-induced FTIR difference spectra involving the same cofactors. The RCs are deposited on an attenuated total reflection (ATR) prism and form a film that is enclosed in a flow cell. Redox transitions in the film of RCs can be repetitively induced either by perfusion of buffers poised at different redox potentials or by illumination. The perfusion-induced ATR-FTIR difference spectra for the oxidation of the primary electron donor P in the RCs of the purple bacteria Rb. sphaeroides and Rp. viridis and P700 in the photosystem 1 of Synechocystis 6803, as well as the Q(A)/Q(A) transition of the quinone acceptor (Q(A)) in Rb. sphaeroides RCs are reported for the first time. They are compared with the light-induced ATR-FTIR difference spectra P+Q(A)/PQ(A) for the RCs of Rb. sphaeroides and P700+/P700 for photosystem 1. It is shown that the perfusion-induced and light-induced ATR-FTIR difference spectra recorded on the same RC film display identical signal to noise ratios when they are measured under comparable conditions. The ATR-FTIR difference spectra are very similar to the equivalent FTIR difference spectra previously recorded upon photochemical or electrochemical excitation of these RCs in the more conventional transmission mode. The ATR-FTIR technique requires a smaller amount of sample compared with transmission FTIR and allows precise control of the aqueous environment of the RC films.
authors.affiliation: SBE/DBCM, CEA-Saclay, Gif-sur-Yvette, France.
authors.forename: Masayo
authors.initials: M
authors.lastname: Iwaki
authors.forename: Sandra
authors.initials: S
authors.lastname: Andrianambinintsoa
authors.forename: Peter
authors.initials: P
authors.lastname: Rich
authors.forename: Jacques
authors.initials: J
authors.lastname: Breton
mesh_terms: D008027:Light; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010477:Perfusion; D045322:Photosynthetic Reaction Center Complex Proteins; D012242:Rhodobacter sphaeroides / Q000378:metabolism; D013053:Spectrophotometry / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D010100:Oxygen