Tan Li-Ming, Yu Jie, Kawakami Tomoaki, Kobayashi Masayuki, Wang Peng, Wang-Otomo Zheng-Yu, Zhang Jian-Ping
Department of Chemistry , Renmin University of China , Beijing 1000872 , PR China.
Faculty of Science , Ibaraki University , Mito 310-8512 , Japan.
J Phys Chem Lett. 2018 Jun 21;9(12):3278-3284. doi: 10.1021/acs.jpclett.8b01197. Epub 2018 Jun 5.
The uphill excitation energy transfer (EET) from the core antenna (LH1) to the reaction center (RC) of purple photosynthetic bacteria was investigated at room temperature by comparing the native LH1-RC from Thermochromatium ( Tch.) tepidum with the hybrid LH1-RC from a mutant strain of Rhodobacter ( Rba.) sphaeroides. The latter protein with chimeric Tch-LH1 and Rba-RC exhibits a substantially larger RC-to-LH1 energy difference (Δ E = 630 cm) of 3-fold thermal energy (3 k T). The spectroscopic and kinetics results are discussed on the basis of the newly reported high-resolution structures of Tch. tepidum LH1-RC, which allow us to propose the existence of a passage formed by LH1 BChls that facilitates the LH1 → RC EET. The semilogarithmic plot of the EET rate against Δ E was found to be linear over a broad range of Δ E, which consolidates the mechanism of thermal activation as promoted by the spectral overlap between the LH1 fluorescence and the special pair absorption of RC.
通过比较嗜热栖热菌（Tch.）的天然光捕获复合体1-反应中心（LH1-RC）与球形红细菌（Rba.）突变株的杂交LH1-RC，在室温下研究了紫色光合细菌中从核心天线（LH1）到反应中心（RC）的上坡激发能量转移（EET）。后者具有嵌合的嗜热栖热菌LH1和球形红细菌RC，其反应中心到光捕获复合体1的能量差（ΔE = 630 cm）显著更大，为热能的3倍（3kT）。基于新报道的嗜热栖热菌LH1-RC的高分辨率结构对光谱和动力学结果进行了讨论，这使我们能够提出由光捕获复合体1细菌叶绿素（BChls）形成的通道的存在，该通道促进了光捕获复合体1→反应中心的能量转移。发现能量转移速率对ΔE的半对数图在很宽的ΔE范围内呈线性，这巩固了由光捕获复合体1荧光与反应中心特殊对吸收之间的光谱重叠所促进的热激活机制。
