PHOTOPHYSICS OF VISUAL CHROMOPHORES AND RHODOPSIN

这项研究项目的长期目标是 视紫质和视紫红质中生色团结合部位的结构 光适应细菌视紫红质及其分子定义 这两个天体中初级光化学事件的电子细节 蛋白质系统。将实现三个目标，以便 实现这些目标：(1)将使用双光子光谱学 为了确定低气压的位置和光物理性质- 在各种视觉生色团中存在“被禁止”的pi-pi*态 在溶液和蛋白质的结合位置中的类似物。这 信息，当与单光子光谱数据结合时。 将让我们深入了解 蛋白质引起的静电和色散扰动 结合部位。(2)主要赛事的储能情况 将测量人造视紫红质和细菌视紫红质类似物 使用脉冲激光光热法。通过更改的位置 聚烯链上的甲基及其能量测定 与光致异构化相关的存储应该是 有可能绘制出结合位点的几何图形。(3)所有- 将使用价电子(INDO-PSDCI)分子轨道理论 以帮助解释光谱数据并计算地面和 激发态势能面和激发态反应路径， 适用于各种键合模式的双键异构化 网站。半经典分子动力学理论将被用来 计算初级粒子的运动轨迹和量子产额 光化学事件。蛋白质的影响将被包括在内 在上述使用经典力场程序的计算中 测定氨基酸残基的平衡几何构型 在结合部位附近的α螺旋上。五花八门 然后，可以通过比较 用实验获得的数据计算结果 本节目的部分内容以及文献中的部分内容。以上内容 三项研究将提供对分子基础的新见解 脊椎动物的视觉转导。此外，还研究了 双光子光谱技术在测定激发态能量中的应用 游离碱和金属卟啉的能级有序化 选定的血红素蛋白结合部位的性质将是 已启动。

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.