Temporal and spectral characterization of the photosynthetic reaction center from Heliobacterium modesticaldum

Adrien Chauvet, Josephine Sarrou, Su Lin, Steven P. Romberger, John H. Golbeck, Sergei Savikhin, Kevin Redding

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

A time-resolved spectroscopic study of the isolated photosynthetic reaction center (RC) from Heliobacterium modesticaldum reveals that thermal equilibration of light excitation among the antenna pigments followed by trapping of excitation and the formation of the charge-separated state P 800 +A0 - occurs within ~25 ps. This time scale is similar to that reported for plant and cyanobacterial photosystem I (PS I) complexes. Subsequent electron transfer from the primary electron acceptor A0 occurs with a lifetime of ~600 ps, suggesting that the RC of H. modesticaldum is functionally similar to that of Heliobacillus mobilis and Heliobacterium chlorum. The (A0 - - A0) and (P800 + - P800) absorption difference spectra imply that an 81-OH-Chl a F molecule serves as the primary electron acceptor and occupies the position analogous to ec3 (A0) in PS I, while a monomeric BChl g pigment occupies the position analogous to ec2 (accessory Chl). The presence of an intense photobleaching band at 790 nm in the (A0 - - A0) spectrum suggests that the excitonic coupling between the monomeric accessory BChl g and the 8 1-OH-Chl a F in the heliobacterial RC is significantly stronger than the excitonic coupling between the equivalent pigments in PS I.

Original languageEnglish (US)
Pages (from-to)1-9
Number of pages9
JournalPhotosynthesis research
Volume116
Issue number1
DOIs
StatePublished - Sep 1 2013

Keywords

  • Accessory pigment
  • Bacteriochlorophyll g
  • Electrochromic shift
  • Heliobacterium modesticaldum
  • Reaction center

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

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