Ultrafast Studies of Electron Transfer in Photosystem II

正确理解光合系统中的初级能量转移和电子转移过程是完全理解自然太阳能转换的关键之一。 本研究计划将利用最先进的超快光谱技术研究光系统II的初级电子转移过程。 几种类型的实验将进行，试图阐明的时间尺度和机制的初级电荷分离PSII。 其中包括： 将使用各种反应中心制备物测量超快动力学，以确定制备方法是否会影响能量弛豫动力学或初级电荷分离速率。 将制备更大的PSII复合物，以研究活性中心中的电子转移速率，并停止关于D1-D2-Cyt b559复合物是否保留天然反应中心结构和动力学的任何推测。 瞬态吸收测量将与超短（50 fs）脉冲，探索可能参与的连贯蛋白质运动的初始动力学的PSII。 共振拉曼测量将试图探测生产的初始电荷分离状态直接，克服高度重叠的电子吸收功能的限制。将电子光谱中的微小差异与由共振增强引入的选择性以及带电和中性颜料的振动光谱中的差异相结合，应该可以以更少的模糊性检测电荷分离态。 严格理解生物光合系统中的初级电子转移反应是完全理解自然太阳能转换的关键之一。 称为光系统II（PSII）的蛋白质复合物负责绿色植物利用光能来从水中产生氧气的能力。 PSII蛋白质复合物与第二个复合物，光系统I（PSI）一起工作，从二氧化碳中形成碳水化合物。 在本研究计划中，最先进的激光技术将用于研究光系统II（PSII）的光引发电子转移反应。 本研究的总体目标是详细了解控制绿色植物光合作用效率和稳健性的因素。 ***

9418390 Sension A proper understanding of the primary energy transfer and electron transfer processes in photosynthetic systems is one of the keys to a complete understanding of natural solar energy conversion. In this research project state-of-the-art ultrafast spectroscopic techniques will be uqed to study the primary electron transfer processes in photosystem II. Several types of experiments will be performed to try to elucidate the time-scale and mechanism for primary charge separation in PSII. These include the following: The ultrafast kinetics will be measured using various reaction center preparations to determine whether the method of preparation can affect either the energy relaxation kinetics or the rate of primary charge separation. Larger PSII complexes will be prepared in order to study the electron transfer rate in active centers and set to rest any speculation as to whether or not the D1-D2-Cyt b559 complex retains the native reaction center structure and dynamics. Transient absorption measurements will be made with ultrashort (50 fs) pulses to explore the possible involvement of coherent protein motion in the initial dynamics of PSII. Resonance Raman measurements will be attempted to probe the production of the initial charge separated state directly, overcoming the limitation of highly overlapping electronic absorption features. Combining the slight differences in the electronic spectra with the selectivity introduced by resonance enhancement and the differences in the vibrational spectra of the charged and neutral pigments, it should be possible to detect the charge separated state with much less ambiguity. %%% A rigorous understanding of the primary electron transfer reactions in biological photosynthetic systems is one of the keys to a complete understanding of natural solar energy conversion. The protein complex referred to as photosystem II (PSII) is responsible for the ability of green plants to utilize light energy to fuel the pr oduction of oxygen from water. The PSII protein complex works in conjunction with a second complex, photosystem I (PSI), to form carbohydrates from carbon dioxide. In this research project, state-of-the-art laser technology will be used to study the light initiated electron transfer reactions of photosystem II (PSII). The overall goal of this investigation is to obtain a detailed understanding of the factors that control the efficiency and robustness of photosynthesis in green plants. ***