AB INITIO CALCULATIONS OF THE RAMAN VIBRATIONAL MODES OF CYSTEINE AND ITS DERIV

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 人类γ-D(HGD)晶状体蛋白的突变与白内障的形成有关。我们已经证明，HGD的突变形式R14C很容易聚集形成可还原的分子间二硫键。在突变体中引入Cys14来代替Arg，可能是造成这种戏剧性蛋白质聚集的原因。在蛋白质的拉曼光谱中明确地确定了Cys-SH键的振动，我们实验确定了Cys 14在R14C突变体的拉曼光谱中的SH贡献。现在，我们想用从头算和密度泛函方法来模拟半胱氨酸14的拉曼光谱，以了解SH基团的化学环境，这不仅决定了它的拉曼频率和强度，还可能影响它的反应活性。为了实现这一目标，我们希望使用SGI机器Popel中提供的Gauss和GamesS等软件产品。在一个相关的项目中，我们已经确定了牛γ-B晶体蛋白中所有七个半胱氨酸残基的拉曼SH带。已知其中一些半胱氨酸残基与谷胱甘肽反应，形成二硫键，并产生通常在晶状体中发现的谷胱甘肽蛋白质衍生物。在这里，我们想再次使用从头算和密度泛函方法计算蛋白质-硫醇-SH键的拉曼振动频率和强度。为了方便这些理论方法的使用，我们已经有了这些蛋白质的高分辨率X射线晶体结构。我们建议使用QM/MM方法，即我们将选择-SH基团周围的一小块区域用于高级理论方法的应用，而对于蛋白质的其余部分，我们将使用使用Amber力场的MM方法。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Mutants of human gamma-D (HGD) crystallin are implicated in cataract formation. We have shown that R14C, a mutant form of HGD readily aggregates forming reducible intermolecular disulfide bonds. Cys14 introduced in the mutant in place of Arg, is the likely cause of such dramatic protein aggregation. The Cys-SH bond vibration is unequivocally determined in the Raman spectrum of proteins, and we have experimentally determined the SH contribution of Cys 14 in the Raman spectrum of the R14C mutant. Now, we would like to use ab-initio and DFT methods in order to model the Raman spectrum of Cys 14 to understand the chemical environment of the SH group, which not only determines its Raman frequency and intensity but may also influence its reactivity. Towards this goal, we would like to use software products such as Gaussian and Gamess available in the SGI machine POPEL. In a related project, we have identified the Raman SH bands of all the seven Cys residues individually in bovine gamma-B crystallin. Some of these Cys residues are known to react with glutathione, forming disulfide bonds and giving rise to the glutathiolated protein derivatives found normally in the lens. Here again, we would like to use ab-initio and DFT methods to calculate the Raman vibrational frequencies and intensities of protein-thiol -SH bonds. To facilitate the use of these theoretical methods, we already have available high-resolution x-ray crystal structures of these proteins. We propose using QM/MM methods whereby we would select a small region around the -SH group for the application of high-level theoretical methods and for the rest of the protein we would use MM methods using the AMBER forcefield.