title: Determination of Excited-State Energies and Dynamics in the B Band of the Bacterial Reaction Center with 2D Electronic Spectroscopy.
abstract: Photosynthetic organisms convert photoenergy to chemical energy with near-unity quantum efficiency. This occurs through charge transfer in the reaction center, which consists of two branches of pigments. In bacteria, both branches are energy-transfer pathways, but only one is also an electron transfer pathway. One barrier to a full understanding of the asymmetry is that the two branches contain excited states close in energy that produce overlapping spectroscopic peaks. We apply polarization-dependent, 2D electronic spectroscopy to the B band of the oxidized bacterial reaction center. The spectra reveal two previously unresolved peaks, corresponding to excited states localized on each of the two branches. Furthermore, a previously unknown interaction between these two states is observed on a time scale of ∼100 fs. This may indicate an alternative pathway to electron transfer for the oxidized reaction center and thus may be a mechanism to prevent energy from becoming trapped in local minima.
authors: §Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, California, United States.
authors: Gabriela S
authors: GS
authors: Schlau-Cohen
authors: §Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, California, United States.
authors: Eleonora
authors: E
authors: De Re
authors: ∥University of Glasgow, Glasgow, United Kingdom.
authors: Richard J
authors: RJ
authors: Cogdell
authors: §Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, California, United States.
authors: Graham R
authors: GR
authors: Fleming
keywords: bacterial reaction center; energy transfer; two-dimensional spectroscopy