Chang M C, Callahan P M, Parkes-Loach P S, Cotton T M, Loach P A
Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500.
Biochemistry. 1990 Jan 16;29(2):421-9. doi: 10.1021/bi00454a017.
The spectroscopic properties of the light-harvesting complex of Rhodospirillum rubrum, B873, and a detergent-isolated subunit form, B820, are presented. Absorption and circular dichroism spectra suggest excitonically interacting bacteriochlorophyll alpha (BChl alpha) molecules give B820 its unique spectroscopic properties. Resonance Raman results indicate that BCHl alpha is 5-coordinate in both B820 and B873 but that the interactions with the BChl C2 acetyl in B820 and B873 are different. The reactivity of BChl alpha in B820 in light and oxygen, or NaBH4, suggests that it is exposed to detergent and the aqueous environment. Excited-state lifetimes of the completely dissociated 777-nm-absorbing form [1.98 ns in 4.5% octyl glucoside (OG)], the intermediate subunit B820 (0.72 ns in 0.8% OG), and the in vivo like reassociated B873 (0.39 ns in 0.3% OG) were measured by single-photon counting. The fluorescence decays were exponential when emission was detected at wavelengths longer than 864 nm. An in vivo like B873 complex, as judged by its spectroscopic properties, can be formed from B820 without the presence of a reaction center.
本文介绍了红螺菌（Rhodospirillum rubrum）捕光复合物B873及其去污剂分离亚基形式B820的光谱性质。吸收光谱和圆二色光谱表明，具有激子相互作用的细菌叶绿素α（BChlα）分子赋予了B820独特的光谱性质。共振拉曼结果表明，BChlα在B820和B873中均为五配位，但与B820和B873中BChl C2乙酰基的相互作用不同。B820中BChlα在光、氧或硼氢化钠作用下的反应活性表明，它暴露于去污剂和水环境中。通过单光子计数测量了完全解离的777nm吸收形式（在4.5%辛基葡糖苷（OG）中为1.98ns）、中间亚基B820（在0.8%OG中为0.72ns）和体内样重新结合的B873（在0.3%OG中为0.39ns）的激发态寿命。当在波长大于864nm处检测发射时，荧光衰减呈指数形式。根据其光谱性质判断，在没有反应中心的情况下，B820可以形成体内样B873复合物。
