Schröter Marco, Alcocer Marcelo J P, Cogdell Richard J, Kühn Oliver, Zigmantas Donatas
Institute of Physics , University of Rostock , Albert-Einstein-Straße 23-24 , 18059 Rostock , Germany.
Chemical Physics , Lund University , Box 124, 22100 Lund , Sweden.
J Phys Chem Lett. 2018 Mar 15;9(6):1340-1345. doi: 10.1021/acs.jpclett.8b00438. Epub 2018 Mar 6.
Bacterial photosynthesis features robust and adaptable energy-harvesting processes in which light-harvesting proteins play a crucial role. The peripheral light-harvesting complex of the purple bacterium Allochromatium vinosum is particularly distinct, featuring a double peak structure in its B800 absorption band. Two hypotheses-not necessarily mutually exclusive-concerning the origin of this splitting have been proposed; either two distinct B800 bacteriochlorophyll site energies are involved, or an excitonic dimerization of bacteriochlorophylls within the B800 ring takes place. Through the use of two-dimensional electronic spectroscopy, we present unambiguous evidence that excitonic interaction shapes the split band. We further identify and characterize all of the energy transfer pathways within this complex by using a global kinetic fitting procedure. Our approach demonstrates how the combination of two-dimensional spectral resolution and self-consistent fitting allows for extraction of information on light-harvesting processes, which would otherwise be inaccessible due to signal congestion.
细菌光合作用具有强大且适应性强的能量收集过程，其中光收集蛋白起着至关重要的作用。紫色细菌嗜酒色菌的外周光收集复合体尤为独特，其B800吸收带具有双峰结构。关于这种分裂的起源，已经提出了两种假说——不一定相互排斥；要么涉及两种不同的B800细菌叶绿素位点能量，要么在B800环内发生细菌叶绿素的激子二聚化。通过使用二维电子光谱，我们提供了明确的证据表明激子相互作用形成了分裂带。我们还通过使用全局动力学拟合程序识别并表征了该复合体内的所有能量转移途径。我们的方法展示了二维光谱分辨率和自洽拟合的结合如何能够提取关于光收集过程的信息，否则由于信号拥挤这些信息将无法获取。
