PHOTOPHYSICS OF VISUAL CHROMOPHORES AND RHODOPSIN

视觉发色团和视紫红质的光物理学

• 批准号: 3285771
• 负责人: ROBERT Richards BIRGE
• 金额: $ 20.86万
• 依托单位: SYRACUSE UNIVERSITY AT SYRACUSE
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-08-01 至 1993-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3285771
• 关键词: Schiff bases; bacteriorhodopsins; biological signal transduction; calorimetry; chemical binding; conformation; electronic spectra; mathematical model; molecular dynamics; molecular orbital; phantom model; photochemistry; photoelectron spectrometry; protein structure; quantum chemistry; rhodopsin; stereoisomer; visual perception

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.

该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 光适应细菌视紫红质并定义分子 这两个事件中主要光化学事件的电子细节 蛋白质系统。 将实现三个目标 实现这些目标：（1）将使用双光子光谱 确定低光的位置和光物理特性 各种视觉发色团中处于“禁止”的 pi-pi* 状态 溶液中和蛋白质结合位点中的类似物。 这 信息，与单光子光谱数据相结合。 将提供有关该事件的性质和规模的见解 蛋白质引起的静电和色散扰动 结合位点。 (2) 初级事件中的能量存储 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。 通过改变位置 沿着多烯链的甲基并确定能量 与光致异构化相关的储存应该是 可以绘制出结合位点的几何形状。 (3) 全部- 将使用价电子（INDO-PSDCI）分子轨道理论 帮助解释光谱数据并计算地面和 激发态势面和激发态反应路径， 用于各种结合模型的双键异构化 网站。 半经典分子动力学理论将被用来 计算初级的轨迹和量子产率 光化学事件。 蛋白质的影响将被包括在内 在使用经典力场程序的上述计算中 确定氨基酸残基的平衡几何结构 在结合位点附近的 α 螺旋上。 各种各样的 然后可以通过比较来测试结合位点的模型 结合实验数据计算得出的结果 该程序的部分内容以及文献中的内容。 以上 三项研究将为分子基础提供新的见解 脊椎动物的视觉传导。 此外，研究还涉及 应用双光子光谱法测定激发态 游离碱和金属卟啉的州级排序以及 所选血红素蛋白的结合位点的性质将是 发起。