Document Detail

Temperature dependence of biphasic forward electron transfer from the phylloquinone(s) A1 in photosystem I: only the slower phase is activated.
MedLine Citation:
PMID:  12686416     Owner:  NLM     Status:  MEDLINE    
The temperature dependence of the biphasic electron transfer (ET) from the secondary acceptor A1 (phylloquinone) to iron-sulfur cluster F(X) was investigated by flash absorption spectroscopy in photosystem I (PS I) isolated from Synechocystis sp. PCC 6803. While the slower phase (tau=340 ns at 295 K) slowed upon cooling according to an activation energy of 110 meV, the time constant of the faster phase (tau=11 ns at 295 K) was virtually independent of temperature. Following a suggestion in the literature that the two phases arise from bidirectional ET involving two symmetrically arranged phylloquinones, Q(K)-A and Q(K)-B, it is concluded that energetic parameters (most likely the driving forces) rather than the electronic couplings are different for ET from Q(K)-A to F(X) and from Q(K)-B to F(X). Two alternative schemes of ET in PS I are presented and discussed.
Rufat Agalarov; Klaus Brettel
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1604     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  2003 Apr 
Date Detail:
Created Date:  2003-04-10     Completed Date:  2003-06-12     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  7-12     Citation Subset:  IM    
Service de Bioénergétique, CEA, and URA 2096 CNRS, CEA Saclay, Gif-sur-Yvette, France.
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MeSH Terms
Cyanobacteria / metabolism
Electron Transport*
Photosynthetic Reaction Center Complex Proteins / metabolism*
Vitamin K 1 / metabolism*
Reg. No./Substance:
0/Photosynthetic Reaction Center Complex Proteins; 84-80-0/Vitamin K 1

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