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 language | English |
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Pages (from-to) | 35-43 |
Number of pages | 9 |
Journal | Biochimica et Biophysica Acta - Bioenergetics |
Volume | 807 |
Issue number | 1 |
DOIs | |
State | Published - 3 Apr 1985 |
Externally published | Yes |
Keywords
- (Mastigocladus sp.)
- ESR
- Iron-sulfur center
- Photosystem I
- Reaction center
- Triplet state