Photosystem I reaction center from Mastigocladus laminosus. Correlation between reduction state of the iron-sulfur centers and the triplet formation mechanisms

Rachel Nechushtai*, Nathan Nelson, Oded Gonen, Haim Levanon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

EPR study of reduced ground and photoexcited triplet state of Photosystem I reaction center in the thermophylic cyanobacterium Mastigocladus laminosus at 8 K is reported. In the reduced ground state preparation, the iron-sulfur EPR spectra are found to be similar to that of Photosystem I reaction center of higher plants. Two types of transient photoexcited triplets are observed and are correlated to the reduction state of the iron-sulfur centers. When electrons can be transferred freely through the acceptors chain, a polarized triplet spectrum is observed, typical of spin-orbit intersystem crossing mechanism with lifetime of approx. 2 ms and is attributed to chlorophyll a, either at the antenna or at A1 in the electron-transport chain. When the iron-sulfur centers are reduced the triplet spectrum is typical of a radical-pair intersystem crossing mechanism with triplet lifetime shorter than 1 ms, and is attributed to P-700. Both species have similar spectroscopic zero field splitting parameters identifying both as chlorophyll a.

Original languageEnglish
Pages (from-to)35-43
Number of pages9
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume807
Issue number1
DOIs
StatePublished - 3 Apr 1985
Externally publishedYes

Keywords

  • (Mastigocladus sp.)
  • ESR
  • Iron-sulfur center
  • Photosystem I
  • Reaction center
  • Triplet state

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