RAMAN STUDIES OF PORPHYRINS/PROTEIN MAQUETTES/PROTEINS

该研究的目标是表征四吡啶在各种环境下的结构、电子和振动特性，包括溶液、蛋白质和蛋白质模型（小合成蛋白质）。主要的研究工具是共振拉曼光谱，虽然紫外-可见，红外和电子顺磁共振光谱；电化学技术;振动分析方法也起着重要的作用。长期目标是将四吡咯的物理性质与其在天然和合成蛋白质中的功能特征（配体结合和传输、电子和能量转移、催化）联系起来。第一个目标是：(1)阐明邻苯啉（具有饱和甲基位置的卟啉）和氢corphinoids（具有饱和甲基和-吡咯位置的卟啉）的振动（和其他）性质；(2)绘制四吡咯金属/轴向配体核心运动的势能面。第一项研究的目标是将对邻苯二甲酸乙酯/氢corphinoids的结构/电子/振动特性的理解水平提高到与目前可用于卟啉的水平相当的水平，并建立表征蛋白质中前一类辅因子的基准。第二个目标是纠正力场中广泛用于结构细化和分子动力学模拟的缺陷。第二个目标是检查两种金属蛋白，羟胺氧化还原酶（HAO）和甲基com还原酶（MCR）活性位点的振动（和其他）光谱特性，这两种金属蛋白对生物圈的组成产生重大影响，从而影响人群的一般健康。HAO是全球氮循环的关键酶，它含有一种铁鞘蛋白（P460），它催化氨转化为亚硝酸盐的最后一步。MCR是一种甲烷生成的关键酶，它含有一种氢corphinoid镍（F430），可以催化碳源转化为甲烷的最后一步。目的是阐明P460和F430活性位点介导其新化学反应的独特特征。第三个目标是表征各种蛋白质模型中异四吡咯辅因子的振动特性。该模型含有含不同金属离子的四吡啶和具有多种氨基酸序列的外周取代基和肽。单层组装的模型也将被调查。目的是阐明合成蛋白质中辅因子的结构，并探索它们的氧化还原和电子特性如何受到蛋白质基质的影响。

The goals of the research are to characterize the structural, electronic, and vibrational properties of tetrapyrroles in various environments including solutions, proteins, and protein maquettes (small synthetic proteins). The principal investigative tool is resonance Raman spectroscopy, although UV-Vis, infrared, and electron paramagnetic resonance spectroscopies; electrochemical techniques; and vibrational analysis methods also play important roles. The long-term objective is to relate the physical properties of the tetrapyrroles to their functional characteristics (ligand binding and transport, electron and energy transfer, catalysis) in both natural and synthetic proteins. The first objective is (1) to elucidate the vibrational (and other) properties of phlorins (porphyrins with saturated methine positions) and hydrocorphinoids (porphyrins with saturated methine and beta-pyrrole positions) and (2) to map out the potential energy surface of the metal/axial-ligand core motions of tetrapyrroles. The goal of the first study is to raise the level of understanding of the structural/elctronic/vibrational properties of phlorins/hydrocorphinoids to one comparable to that currently available for porphyrins and establish benchmarks for characterizing the former types of cofactors in proteins. The goal of the second is to rectify deficiencies in force fields that are widely used for structure refinement and molecular dynamics simulations. The second objective is to examine the vibrational (and other) spectroscopic properties of the active sites of two metalloproteins, hydroxylamine oxidoreductase (HAO) and methyl-CoM reductase (MCR), that significantly impact the composition of the biosphere and hence, the general health of the population. HAO, a key enzyme in the global nitrogen cycle, contains an iron phlorin (P460) that catalysis the final step in the conversion of ammonia to nitrite. MCR, a key enzyme in methanogenesis, contains a nickel hydrocorphinoid (F430) that catalysis the final step in the conversion of carbon sources to methane. The goal is to elucidate the unique features of the P460 and F430 active sites that mediate their novel chemistry. The third objective is to characterize the vibrational properties of the metatallotetrapyrrole cofactors in a variety of protein maquettes. The maquettes contain tetrapyrroles with different metal ions and peripheral substituents and peptides with a variety of amino acid sequences. Monolayer assemblies of the maquettes will also be investigated. The goal is to elucidate the structure of the cofactors in the synthetic proteins and explore how their redox and electronic properties are influenced by the protein matrix.