Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530 Gothenburg, Sweden.
J Am Chem Soc. 2012 Oct 10;134(40):16484-7. doi: 10.1021/ja3065478. Epub 2012 Oct 1.
Photosynthetic reaction centers convert sunlight into a transmembrane electrochemical potential difference, providing chemical energy to almost all life on earth. Light energy is efficiently transferred through chromophore cofactors to the sites, where charge separation occurs. We applied two-dimensional electronic spectroscopy to assess the role of coherences in the photoresponse of the bacterial reaction center of Rhodobacter sphaeroides. By controlling the polarization of the laser beams, we were able to assign unambiguously the oscillatory dynamics to electronic (intermolecular) coherences. The data show that these coherences are sustained for more than 1 ps, indicating that the protein coherently retains some excitation energy on this time scale. Our finding provides a mechanism for effective delocalization of the excitations on the picosecond time scale by electronic coherence, setting the stage for efficient charge separation.
光合作用反应中心将阳光转化为跨膜电化学势差，为地球上几乎所有的生命提供化学能量。光能通过发色团辅助因子有效地传递到发生电荷分离的位点。我们应用二维电子光谱来评估相干在球形红杆菌细菌反应中心光响应中的作用。通过控制激光束的偏振，我们能够将振荡动力学明确地分配给电子（分子间）相干。数据表明，这些相干性持续超过 1 皮秒，表明在这个时间尺度上，蛋白质相干地保留了一些激发能。我们的发现为电子相干在皮秒时间尺度上有效离域激发提供了一种机制，为有效的电荷分离奠定了基础。
