PHOTOPHYSICS OF VISUAL CHROMOPHORES AND RHODOPSIN

本研究项目的长期目标是分配 视紫红质中发色团结合位点的结构， 光适应性细菌视紫红质，并定义分子 这两个主要光化学事件的电子细节 蛋白质系统 将实现三个目标， 实现了以下目标：（1）采用双光子光谱技术 以确定低- 各种可见发色团中的“禁断”π-π * 态 类似物在溶液中和蛋白质的结合位点。 这 信息，当与单光子光谱数据相结合时。 将提供洞察的性质和规模的 蛋白质引起的静电和色散扰动 结合位点。 (2)能源储存在主要事件中， 将测量人工视紫红质和细菌视紫红质类似物 使用脉冲激光光量热法。 通过改变 甲基沿着多烯链，并决定能量 与光异构化相关的储存， 可以绘制出结合位点的几何形状。 (3)所有- 价电子（INDO-PSDCI）分子轨道理论 帮助解释光谱数据，计算地面和 激发态势能面，激发态反应路径， 对于各种模型的结合， 网站. 半经典分子动力学理论将用于 计算初级粒子的轨道和量子产额 光化学事件 蛋白质的影响将包括在内 在上述使用经典力场程序的计算中 以确定氨基酸残基的平衡几何形状 在结合位点附近的α螺旋上。 各种 然后可以通过比较结合位点的模型来测试结合位点的模型。 计算结果与实验数据吻合较好 本节目的部分内容以及文献。 上述 三项研究将为分子基础提供新的见解， 脊椎动物视觉信号转导 此外，关于 应用双光子光谱法测定激发态 游离碱和金属卟啉的态能级有序性 所选血红素蛋白的结合位点的性质将是 启动。

The long-term objectives of this research project are to assign the structure of the chromophore binding sites in rhodopsin and light-adapted bacteriorhodopsin and to define the molecular electron details of the primary photochemical events in these two protein systems. Three objectives will be carried out in order to accomplish these goals: (1) Two-photon spectroscopy will be used to identify the location and photophysical properties of the low- lying "forbidden" pi-pi* states in various visual chromophore analogs in solution and in the binding sites of the proteins. This information, when combined with the one-photon spectroscopic data. will provide insights into the nature and magnitude of the electrostatic and dispersive perturbations induced by the protein binding sites. (2) Energy storage in the primary events in artificial rhodopsin and bacteriorhodopsin analogs will be measured using pulsed laser photocalorimetry. By changing the position of methyl groups along the polyene chain and determining the energy storage associated with the photoisomerization it should be possible to map out the geometry of the binding sites. (3) All- valence electron (INDO-PSDCI) molecular orbital theory will be used to help interpret the spectral data and calculate the ground and excited state potential surfaces, and excited stat reaction paths, for double bond isomerization for various models of the binding sites. Semiclassical molecular dynamics theory will be used to calculate the trajectories and the quantum yields of the primary photochemical events. The effect of the protein will be included in the above calculations using classical force field procedures to determine the equilibrium geometry of the amino acid residues on the alpha helices in the vicinity of the binding site. Various models for the binding site can then be tested by comparing the calculated results with the data obtained in the experimental portions of this program as well as from the literature. The above three studies will provide new insights into the molecular basis of vertebrate visual transduction. In addition, studies on the application of two-photon spectroscopy to determine the excited state level ordering in free base and metalloporphyrins and the nature of the binding sites of selected heme proteins will be initiated.