Reaction of Ai-menaquinone in Type I Reaction Center of Heliobacterium Modesticaldum at Cryogenic Temperature
Temperature dependence of electron transfer reaction via Ai-menaquinone in type I homodimeric reaction center of Heliobacterium modesticaldum (hRC) was observed by time-resolved electron paramagnetic resonance (EPR) spectroscopy. Flash excitation induced an electron spin polarization (ESP) signal due to P800+Fx- radical pair at 14 K, exhibiting an E/A (E, emission; A, absorption) spectral pattern. After the hRC core complex was pre-illuminated at 210 K for 1 hour and subsequently cooled to 5 K during illumination, another ESP signal due to P800+A1-, exhibiting an A/E pattern, was flash-induced at 14 K. The decay time was estimated to be 90 us at 5 K and 25 us at 20 K, respectively. The recombination of P800+A1- in hRC is significantly faster at all the temperatures, compared to that of P700+A1- in PS I, which occurs in around 100μs with little temperature dependence. The recombination time of P800+Fx- was a 4-11 ms at 5 K in contrast to the longer time than 100 ms in PSI. These results indicate that A1- menaquinone is involved in the rapid electron transfer between P700 and Fx in hRC, as phylloquinone in PSI, probably with unique energy gap or geometry.
Heliobacteria Type IRC EPR Quinone Homodimer RC Electron spin polarization
Toru Kondo Masahiro Matsuoka Chihiro Azai Hiroyuki Mino Hirozo Oh-oka Shigeru Itoh
Division of Material Science Physics, Graduate School of Science, Nagoya University, Japan Department of Biological Sciences, Graduate School of Science, Osaka University, Japan
国际会议
15th International Conference on Photosynthesis(第15届国际光合作用大会)
北京
英文
21-24
2010-08-22（万方平台首次上网日期，不代表论文的发表时间）