Energy transfer pathways in the minor antenna complex CP29 of photosystem II: A femtosecond study of carotenoid to chlorophyll transfer on mutant and WT complexes

Roberta Croce, Marc G. Müller, Stefano Caffarri, Roberto Bassi, Alfred R. Holzwarth*

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The energy transfer processes between carotenoids and Chls have been studied by femtosecond transient absorption in the CP29-WT complex, which contains only two carotenoids per polypeptide located in the L1 and L2 sites, and in the CP29-E166V mutant in which only the L1 site is occupied. The comparison of these two samples allowed us to discriminate between the energy transfer pathways from the two carotenoid binding sites and thus to obtain detailed information on the Chl organization in CP29 and to assign the acceptor chlorophylls. For both samples, the main transfer occurs from the S2 state of the carotenoid. In the case of the L1 site the energy acceptor is the Chl a 680 nm (A2), whereas the Chl a 675 nm (A4-A5) and the Chl b 652 nm (B6) are the acceptors from the xanthophyll in the L2 site. These transfers occur with lifetimes of 80-130 fs. Two additional transfers are observed with 700-fs and 8- to 20-ps lifetimes. Both these transfers originate from the carotenoid S1 states. The faster lifetime is due to energy transfer from a vibrationally unrelaxed S1 state, whereas the 8- to 20-ps component is due to a transfer from the S1,0 state of violaxanthin and/or neoxanthin located in site L2. A comparison between the carotenoid to Chl energy transfer pathways in CP29 and LHCII is presented and differences in the structural organization in the two complexes are discussed.

Original languageEnglish
Pages (from-to)2517-2532
Number of pages16
JournalBiophysical Journal
Volume84
Issue number4
DOIs
Publication statusPublished - 1 Apr 2003

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