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Photoreduction of the quinone pool in the bacterial photosynthetic membrane: identification of infrared marker bands for quinol formation
Author(s) -
Mezzetti Alberto,
Leibl Winfried,
Breton Jacques,
Nabedryk Eliane
Publication year - 2003
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(03)00118-2
Subject(s) - rhodobacter sphaeroides , quinone , chemistry , photosynthetic reaction centre , photochemistry , redox , rhodobacter , molecule , rhodospirillaceae , membrane , photosynthesis , infrared , crystallography , infrared spectroscopy , stereochemistry , electron transfer , organic chemistry , biochemistry , physics , mutant , optics , gene
The photoreduction of the quinone (Q) pool in the photosynthetic membrane of the purple bacterium Rhodobacter sphaeroides was investigated by steady‐state and time‐resolved Fourier transform infrared difference spectroscopy. The results are consistent with the existence of a homogeneous Q pool inside the chromatophore membrane, with a size of around 20 Q molecules per reaction center. IR marker bands for the quinone/quinol (Q/QH 2 ) redox couple were recognized. QH 2 bands are identified at 1491, 1470, 1433 and 1388–1375 cm −1 . The 1491 cm −1 band, which is sensitive to 1 H/ 2 H exchange, is assigned to a C–C ring mode coupled to a C–OH mode. A feature at ∼1743/1720 cm −1 is tentatively related to a perturbation of the carbonyl modes of phospholipid head groups induced by QH 2 formation. Complex conformational changes of the protein in the amide I and II spectral ranges are also apparent during reduction and reoxidation of the Q pool.