Early Bacteriopheophytin Reduction in Charge Separation in Reaction Centers of Rhodobacter sphaeroides

Jingyi Zhu, Ivo H. M. van Stokkum, Laura Paparelli, Michael R. Jones, Marie Louise Groot

Research output: Contribution to journalArticle (Academic Journal)peer-review

30 Citations (Scopus)

Abstract

A question at the forefront of biophysical sciences is, to what extent do quantum effects and protein conformational changes play a role in processes such as biological sensing and energy conversion? At the heart of photosynthetic energy transduction lie processes involving ultrafast energy and electron transfers among a small number of tetrapyrrole pigments embedded in the interior of a protein. In the purple bacterial reaction center (RC), a highly efficient ultrafast charge separation takes place between a pair of bacteriochlorophylls: an accessory bacteriochlorophyll (B) and bacteriopheophytin (H). In this work, we applied ultrafast spectroscopy in the visible and near-infrared spectral region to Rhodobacter sphaeroides RCs to accurately track the timing of the electron on B-A and H-A via the appearance of the B-A and H-A anion bands. We observed an unexpectedly early rise of the H-A(-) band that challenges the accepted simple picture of stepwise electron transfer with 3 ps and 1 ps time constants. The implications for the mechanism of initial charge separation in bacterial RCs are discussed in terms of a possible adiabatic electron transfer step between B-A and H-A, and the effect of protein conformation on the electron transfer rate.

Original languageEnglish
Pages (from-to)2493-2502
Number of pages10
JournalBiophysical Journal
Volume104
Issue number11
DOIs
Publication statusPublished - 4 Jun 2013

Keywords

  • BACTERIAL REACTION CENTERS
  • PHOTOSYNTHETIC REACTION CENTERS
  • PRIMARY ELECTRON-TRANSFER
  • EXCITATION WAVELENGTH DEPENDENCE
  • INDUCED STRUCTURAL-CHANGES
  • ENERGY-TRANSFER
  • PHOTOSYSTEM-II
  • REORGANIZATION PARAMETERS
  • ULTRAFAST SPECTROSCOPY
  • VIBRATIONAL COHERENCE

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