Reaction of A1-menaquinone in type I reaction center of heliobacterium modesticaldum at cryogenic temperature

Toru Kondo, Masahiro Matsuoka, Chihiro Azai, Hiroyuki Mino, Hirozo Oh-Oka, Shigeru Itoh

研究成果: Chapter


Temperature dependence of electron transfer reaction via A1-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 μs at 5 K and 25 μs 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 100 μs 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.

ホスト出版物のタイトルAdvanced Topics in Science and Technology in China
出版社Springer Science and Business Media Deutschland GmbH
出版ステータスPublished - 2013


名前Advanced Topics in Science and Technology in China

ASJC Scopus subject areas

  • 化学工学(全般)
  • 工学(全般)
  • 一般


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