PHOTOPHYSICS OF VISUAL CHROMOPHORES AND RHODOPSIN

视觉发色团和视紫红质的光物理学

• 批准号: 3285778
• 负责人: ROBERT Richards BIRGE
• 金额: $ 16.64万
• 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/3285778
• 关键词: Schiff bases; bacteriorhodopsins; 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; visual phototransduction

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 变子团结合位点的结构和 浅型细菌紫红质并定义分子 这两个主要光化学事件的电子详细信息 蛋白质系统。 将实现三个目标 完成这些目标：（1）将使用两光谱光谱法 确定低 - 的位置和光物理特性 在各种视觉发色团中撒谎“禁止” pi-pi*状态 溶液中的类似物和蛋白质的结合位点。 这 信息与单光子光谱数据结合使用。 将提供有关自然和大小的见解 蛋白质诱导的静电和分散扰动 绑定位点。 （2）在主要事件中存储的能源 将测量人造视紫红质和细菌紫红质类似物 使用脉冲激光光钙化法。 通过更改位置 沿多元链的甲基并确定能量 与光异构化相关的存储应该是 可以绘制结合位点的几何形状。 （3） 价电子（Indo-PSDCI）分子轨道理论将被使用 帮助解释光谱数据并计算地面和 激发状态电位表面和激发的Stat反应路径， 用于双键异构化的各种结合模型 站点。 半经典分子动力学理论将用于 计算主要的轨迹和量子产率 光化学事件。 蛋白质的效果将包括在内 在上述使用经典力场程序的计算中 确定氨基酸残基的平衡几何形状 在结合位点附近的Alpha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 通过实验中获得的数据计算出的结果 该程序的部分以及文献。 以上 三项研究将为分子基础提供新的见解 脊椎动物视觉转导。 此外，研究 应用两光子光谱以确定激发 自由碱和金属磷脂中的状态级订购以及 选定血红素蛋白的结合位点的性质将是 发起。