Vibrational and Optical Probes of Electric Fields in Proteins

描述（由申请人提供）：基本假设是， 血红素蛋白影响血红素的蛋白稳定性和反应性。三个具体目标是 提出了第一个是研究蛋白质表面的性质，重点是水 交互.同位素标记肽的红外光谱将回答邻近氨基酸在影响酰胺-水氢键中的作用的问题。蛋白质将在玻璃中进行检测，单分子检测用于分离蛋白质的未折叠形式。第二个目标是预测血红素环境对光学和红外光谱的影响。辣根过氧化物酶和细胞色素c的红外和可见光谱的特征将被确定，然后根据连续静电，分子动力学和量子力学计算解释。目的是了解蛋白质如何调节特定群体的特征。第三个目标是定量表征蛋白质的动力学和动力学对内部反应的作用。辣根过氧化物酶中结合底物和激发态卟啉之间的电子转移反应将作为溶剂粘度和温度的函数进行研究。溶剂依赖和独立的运动将被分离，结果将与分子力学相关联。此外，我们问的作用，动力学允许氧气通过辣根过氧化物酶的多肽链扩散。使用磷光猝灭法，将研究氧的可及性。过氧化物酶有一个通道，血红素可到达溶剂。x射线 结构表明，添加底物阻断了该通道，而蛋白质构象几乎没有变化。由此可见，如果氧主要通过通道进入血红素，则氧猝灭反应将被底物抑制。

DESCRIPTION (provided by applicant): The underlying hypothesis is that internal electric fields in heme proteins influence the protein stability and reactivity of the heme. Three specific aims are proposed. The first is to examine the nature of surface of proteins with an emphasis on water interactions. Infrared spectroscopy of isotopically labeled peptides will answer questions of the role of neighboring amino acids in influencing amide-water H-bonds. Proteins will be examined in glasses, and single molecule detection used to isolate unfolded forms of the protein. The second goal is to predict the effect of heme environment upon optical and IR spectra. Features in the infrared and visible spectra of horseradish peroxidase and cytochrome c will be determined and then interpreted in light of continuum electrostatics, molecular dynamics and quantum mechanic calculations. The intention is to understand how the protein modulates the characteristics of particular groups. The third aim is the quantitative characterization of the dynamics of proteins and the role of dynamics on internal reactions. An electron transfer reaction between bound substrate and excited state porphyrin in horseradish peroxidase will be examined as a function of solvent viscosity and temperature. Solvent dependent and independent motions will be separated, and the results will be correlated with molecular mechanics. Additionally, we ask about the role of dynamics in allowing the diffusion of oxygen through the polypeptide chain of horseradish peroxidase. Using a phosphorescence quenching method, the oxygen accessibility will be studied. Peroxidase has a channel to the heme reachable to the solvent. The x-ray structure shows that adding substrate blocks this channel, with little change in protein conformation. It follows that if oxygen accessibility to the heme occurs mainly through the channel, then the oxygen quenching reaction will be inhibited by the substrate.