【作者】 郭俊华；

【导师】 郭立俊；

【作者基本信息】 河南大学 ， 光学， 2006， 硕士

【摘要】 光合作用是自然界中的有机生物吸收太阳光能并将其转化为稳定化学能的重要途径。光合作用起始于外周捕光天线系统对光能的吸收,之后能量通过高效、快速的传递过程最终陷获于反应中心,所有这些过程都仅仅发生在几百飞秒到几十皮秒时间范围内。对其中的超快能量传递途径及相关的机制的研究是近年来光合作用研究领域的一大热点。本论文主要利用飞秒泵浦探测光谱技术对高等植物外周捕光天线复合体LHCII、紫细菌外周捕光天线复合体LH2-RS601及其突变体LH2-GM309中的超快光动力学过程进行了研究,所得到的主要结果如下,1.在绿色植物中分离出的LHCII中,不同色素之间及同种色素的激子态之间存在着快速高效的能量传递过程,利用飞秒泵浦探测光谱技术观测到单体内Chl b到其邻近的Chl a之间的能量传递发生在200~300 fs时域,其作用机制符合Forster传递理论;而单体内Chl a的激子带间的能量弛豫过程发生在几百飞秒时间尺度;同时,还观察到不同单体内Chl a分子之间的能量平衡过程,该过程发生在几个皮秒的时间范围,而大于50 ps的过程则源于不同聚集体中Chl a分子之间的能量平衡过程或分子的构象变化。2.利用飞秒泵浦探测技术研究了紫细菌Rb.sphaeroides 601外周捕光天线LH2中的能量传递过程,通过改变不同的激发和探测波长,实验上观察到B800到B850之间存在的快速能量传递,能量传递时间在几百个飞秒的时间范围。然而,Forster理论预算的结果则长于实验得到的时间常数,在B800吸收带的蓝侧和红侧激发时都发现了其间的能量传递速率随着激发波长的蓝/红移而增加的现象,考虑到在B800吸收带中包含着B850激子带的吸收贡献,在B800两侧激发时由于B800吸收的贡献相对减小,而由B850上激子带直接激发对信号的贡献有所增加,这些动力学过程表现为B800和B850同时被激发并伴有B800到B850之间的能量传递等复杂过程。实验中所观察到的一个慢的吸收恢复过程,更多还原

【Abstract】 The photosynthesis is the most important and highest efficient photochemical process found in photosynthetic organisms in the nature. The process of photosynthesis origins in the capture of light energy, and energy is captured by the Reaction Center via ultrafast and high efficient transfer processes, all these processes which all take place in the tens picosecond or subpicosecond time region. The study on pathways and photophysical / photochemical mechanisms of ultrafast energy transfer has been attracted much attention from the experimental and theoretical scientists, and it is also an important subject of researchers from physics, chemistry and biology. In this thesis, we studied the photoinduced ultrafast dynamics taking place in peripheral light-harvesting complex LHCII from high plant, the peripheral light harvesting antenna LH2 from purple bacteria Rb. sphaeroides 601 (LH2-RS601) and it’s mutation LH2-GM309 by using ultrafast spectroscopic techniques. The results obtained in our experiments can be concluded as follows,1. In the LHCII isolated from green plant, there exists ultrafast energy transfer processes between the electronic states of different chlorophylls (Chl a and Chl b) involved and also among the excitonic states of Chl a. It was observed from our femtosecond pump-probe experiments that the process of energy relaxation from Chl b to its neighboring Chl a in the monounit of LHCII takes place in 200~300 fs time region, which can be interpreted with the conventional Forster excitation transfer mechanism, on the other hand, the excitation relaxation between the excitonic states of Chl a is of subpicosecond time scale. In addition, the energy equilibrium process of intermo -lecular in Chl a was also observed which happens in several picoseconds.更多还原