Hastings G, Kleinherenbrink F A, Lin S, Blankenship R E
Department of Chemistry and Biochemistry, Arizona State University, Tempe 85287-1604.
Biochemistry. 1994 Mar 22;33(11):3185-92. doi: 10.1021/bi00177a007.
Picosecond fluorescence and femtosecond transient absorption spectroscopy have been used to investigate the primary energy transfer and trapping processes in a photosystem II deletion mutant from the cyanobacterium Synechocystis sp. PCC 6803, which contains active photosystem I reaction centers with approximately 100 chlorophylls per P700. In all experiments, low levels of excitation were used which avoid annihilation processes. Following 590-nm excitation, at room temperature, spectral equilibration is observed in both fluorescence and absorption measurements and is characterized by a time constant of 4-6 ps. The shape of the spectra associated with the equilibration process indicates that long wavelength pigments (pigments with absorption maxima at longer wavelength than that of the primary electron donor, P700) are present and functional at physiological temperatures in this preparation. The overall decay of excitations in the antenna is characterized by a time constant of 24-28 ps, in both fluorescence and absorption measurements. The 24-28-ps process results in the appearance of absorption changes associated with only P700+ formation. Absorption changes associated with the reduction of the primary electron acceptor were not resolved under the experimental conditions used here.
皮秒荧光和飞秒瞬态吸收光谱已被用于研究来自集胞藻属PCC 6803蓝细菌的光系统II缺失突变体中的初级能量转移和捕获过程，该突变体含有活性光系统I反应中心，每个P700约有100个叶绿素。在所有实验中，使用低水平的激发以避免湮灭过程。在590 nm激发后，在室温下，在荧光和吸收测量中均观察到光谱平衡，其时间常数为4 - 6 ps。与平衡过程相关的光谱形状表明，在此制剂中，长波长色素（吸收最大值波长比初级电子供体P700更长的色素）在生理温度下存在且起作用。在荧光和吸收测量中，天线中激发的整体衰减的时间常数均为24 - 28 ps。24 - 28 ps的过程导致仅与P700 +形成相关的吸收变化出现。在此处使用的实验条件下，未分辨出与初级电子受体还原相关的吸收变化。
