Lin S, Kleinherenbrink F A, Chiou H C, Blankenship R E
Department of Chemistry and Biochemistry, Arizona State University, Tempe 85287-1604.
Biophys J. 1994 Dec;67(6):2479-89. doi: 10.1016/S0006-3495(94)80736-2.
Transient absorption difference spectra in the Qy absorption band from membranes of Heliobacillus mobilis were recorded at 140 and 20 K upon 200 fs laser pulse excitation at 590 nm. Excitation transfer from short wavelength absorbing forms of bacteriochlorophyll g to long wavelength bacteriochlorophyll g occurred within 1-2 ps at both long wavelength bacteriochlorophyll g occurred within 1-2 ps at both temperatures. In addition, a slower energy transfer process with a time constant of 15 ps was observed at 20 K within the pool of long wavelength-absorbing bacteriochlorophyll g. Energy transfer from long wavelength antenna pigments to the primary electron donor P798 was observed, yielding the primary charge-separated state P798+A0-. The time constant for this process was 30 ps at 140 K and about 70 ps at 20 K. A decay component with smaller amplitude and a lifetime of up to hundreds of picoseconds was observed that was centered around 814 nm at 20 K. Kinetic simulations using simple lattice models reproduce the observed decay kinetics at 295 and 140 K, but not at 20 K. The kinetics of energy redistribution within the spectrally heterogeneous antenna system at low temperature argue against a simple "funnel" model for the organization of the antenna of Heliobacillus mobilis and favor a more random spatial distribution of spectral forms. However, the relatively high rate of energy transfer from long wavelength antenna bacteriochlorophyll g to the primary electron donor P798 at low temperature is difficult to explain with either of these models.
在590nm处用200fs激光脉冲激发后，于140K和20K下记录了运动性嗜盐杆菌膜在Qy吸收带的瞬态吸收差光谱。在两个温度下，细菌叶绿素g的短波长吸收形式向长波长细菌叶绿素g的激发转移在1 - 2皮秒内发生。此外，在20K下，在长波长吸收细菌叶绿素g的池内观察到一个时间常数为15皮秒的较慢能量转移过程。观察到从长波长天线色素到初级电子供体P798的能量转移，产生初级电荷分离态P798 + A0 -。该过程的时间常数在140K时为30皮秒，在20K时约为70皮秒。在20K下观察到一个幅度较小、寿命长达数百皮秒的衰减成分，其中心波长约为814nm。使用简单晶格模型的动力学模拟重现了在295K和140K下观察到的衰减动力学，但在20K下则不然。低温下光谱异质天线系统内能量重新分布的动力学与运动性嗜盐杆菌天线组织的简单“漏斗”模型相悖，更倾向于光谱形式的更随机空间分布。然而，用这两种模型中的任何一种都难以解释低温下从长波长天线细菌叶绿素g到初级电子供体P798的相对较高的能量转移速率。
