Blue light drives B-side electron transfer in bacterial photosynthetic reaction centers

Su Lin, E. Katilius, A. L M Haffa, A. K W Taguchi, Neal Woodbury

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


The core of the photosynthetic reaction center from the purple non-sulfur bacterium Rhodobacter sphaeroides is a quasi-symmetric heterodimer, providing two potential pathways for transmembrane electron transfer. Past measurements have demonstrated that only one of the two pathways (the A-side) is used to any significant extent upon excitation with red or near-infrared light. Here, it is shown that excitation with blue light into the Soret band of the reaction center gives rise to electron transfer along the alternate or B-side pathway, resulting in a charge-separated state involving the anion of the B-side bacteriopheophytin. This electron transfer is much faster than normal A-side transfer, apparently occurring within a few hundred femtoseconds. At low temperatures, the B-side charge-separated state is stable for at least 1 ns, but at room temperature, the B-side bacteriopheophytin anion is short-lived, decaying within ∼15 ps. One possible physiological role for B-side electron transfer is photoprotection, rapidly quenching higher excited states of the reaction center.

Original languageEnglish (US)
Pages (from-to)13767-13773
Number of pages7
Issue number46
StatePublished - Nov 20 2001

ASJC Scopus subject areas

  • Biochemistry


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