Photobiology of Rhodopsin & Bacteriorhodopsin

描述（由申请人提供）：本研究的长期目标 程序是了解蛋白质光化学的分子细节 细菌视紫红质和视觉中的介导和波长调节 视杆细胞和视锥细胞的色素。我们在目前的资助期内的重点是 研究蓝色，紫色和紫外线锥，因为相对而言， 这些颜料。将使用的主要光谱工具包括 单光子和双光子光谱学，傅里叶变换红外 光谱、拉曼光谱、CD光谱和脉冲激光 光量热法拟进行的主要生化研究包括 定点诱变和发色团类似物取代以及 随机诱变，然后进行波长和光化学筛选 特性.理论研究将在很大程度上依赖于MNDOPSDCI的使用 分子轨道理论来探测的天体物理性质的 蛋白质结合的发色团。本赠款期的一个重要和新的目标是 在MNDOPSDCI中加入圆二色谱的预测 程序，直接目标是使用实验CD光谱分析 视紫红质和视锥色素的蛋白质结合位点。我们还将使用 从头算和半经验分子轨道理论来研究基态 性质的发色团结合位点，同时使用分子力学， 描述蛋白质的其余部分。我们的目标是将联合收割机 实验和理论在一个协同程序，提高两者。此外 对于上述更加全球化的目标，我们将寻求回答以下问题 具体问题：（1）波长的主要机制是什么？ 调节锥细胞色素的作用(2)是什么造成了 细菌视紫红质与感觉光的吸收光谱的差异 视紫红质II？(3)氯离子结合的机制是什么 锥状色素中的位点影响 长波长锥状色素中的发色团(4)钙在哪里 细菌视紫红质中的结合位点，以及这些位点如何影响 结合发色团的物理性质？(5)哪些具体 蛋白质发色团相互作用负责选择6-S-顺式， 6-s-反式环构象的结合生色团，为什么视紫红质 选择6-s-cis，而细菌视紫红质和感觉视紫红质选择 6-s-反式构象？

DESCRIPTION (provided by applicant): The long-term objectives of this research program are to understand the molecular details of protein photochemical mediation and wavelength regulation in bacteriorhodopsin and the visual pigments of rods and cones. Our emphasis for the present grant period is to study the blue, violet and uv cones because relatively little is known about these pigments. The key spectroscopic tools that will be used include one-photon and two-photon spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, CD spectroscopy and pulsed laser photocalorimetry. The principal biochemical studies to be undertaken include site-directed mutagenesis and chromophore analog substitutions as well as random mutagenesis followed by screening for wavelength and photochemical properties. The theoretical studies will rely heavily on the use of MNDOPSDCI molecular orbital theory to probe the photophysical properties of the protein-bound chromophores. An important and new goal of this grant period is to add the prediction of circular dichroism spectra to the MNDOPSDCI procedures, with the immediate goal of using experimental CD spectra to analyze the protein binding sites of rhodopsin and the cone pigments. We will also use ab-initio and semiempirical molecularorbital theory to examine the ground state properties of the chromophore binding sites while using molecular mechanics to describe the remaining portions of the protein. Our goal is to combine experiment and theory in a synergistic program that enhances both. In addition to the more global goals outlined above, we will seek to answer the following specific questions: (1) What are the principal mechanisms of wavelength regulation in the cone pigments? (2) What is responsible for the significant difference in the absorption spectra of bacteriorhodopsin versus sensory rhodopsin II? (3) What are the mechanisms through which the chloride binding sites in the cone pigments influence the spectroscopic properties of the chromophores in the long wavelength cone pigments? (4) Where are the calcium binding sites in bacteriorhodopsin, and how do these sites influence the photophysical properties of the bound chromophore? (5) What specific proteinchromophore interactions are responsible for selecting 6-s-cis versus 6-s-trans ring conformations of the bound chromophore, and why does rhodopsin select the 6-s-cis while bacteriorhodopsin and sensory rhodopsin select the 6-s-trans conformation?