Premium
The triplet state of the primary donor of the green photosynthetic bacterium Chloroflexus aurantiacus
Author(s) -
den Blanken H.J.,
Vasmel H.,
Jongenelis A.P.J.M.,
Hoff A.J.,
Amesz J.
Publication year - 1983
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 - 10.1016/0014-5793(83)81004-7
Subject(s) - absorbance , photochemistry , dimer , singlet state , chemistry , photosynthetic reaction centre , triplet state , bacteriochlorophyll , electron paramagnetic resonance , electron donor , pigment , crystallography , nuclear magnetic resonance , physics , electron transfer , atomic physics , excited state , molecule , organic chemistry , chromatography , catalysis
The technique of absorbance‐detected electron spin resonance in zero magnetic field (ADMR) was applied to investigate the structure of the reaction center of the facultatively aerobic green bacterium Chloroflexus aurantiacus . The triplet‐minus‐singlet absorbance difference spectrum thus obtained at 1.2K shows a clear resemblance to those earlier reported for Rhodopseudomonas viridis and Rps. sphaeroides R‐26. The most prominent features are the bleaching of the Q y band of the primary electron donor at 887 nm and the appearance of a narrow band at 807 nm upon triplet formation. We conclude that the primary electron donor P‐865 of Chloroflexus aurantiacus is a BChl a dimer with Q y and Q x absorbance bands at 887 and 606 nm, respectively, at 1.2 K; apparently the triplet state is localized on an optical time scale on one of the constituent pigments of the dimer. The zero field splitting parameters | D | and, | E | of P‐865 are 197.7 (± 0.7) × 10 −4 cm −1 and 47.3 (± 0.7) × 10 −4 cm −1 , respectively. Decay rates of 12 660 (± 750) s −1 , 14 290 (± 800) s −1 and 1690 (± 50) s −1 were observed for the x, y and z triplet sublevels, respectively.