RAMAN STUDIES OF PORPHYRINS/PROTEIN MAQUETTES/PROTEINS

这项研究的目标是表征四聚吡咯在各种环境中的结构、电子和振动性质，包括溶液、蛋白质和蛋白质模型(小的合成蛋白质)。主要的研究工具是共振拉曼光谱，尽管紫外可见光谱、红外光谱和电子顺磁共振光谱、电化学技术和振动分析方法也发挥了重要作用。长期的目标是将天然和合成蛋白质中四吡咯的物理性质与它们的功能特性(配体结合和运输、电子和能量转移、催化)联系起来。第一个目标是(1)阐明二氢卟啉(饱和亚甲基位置的卟啉)和氢化珊瑚(饱和亚甲基和β-吡咯位置的卟啉)的振动(和其他)性质，以及(2)绘制四吡咯的金属/轴向配体核心运动的势能面。第一项研究的目标是将对连翘素/氢珊瑚素类化合物的结构/电子/振动性质的了解提高到与目前可用于卟啉的性质相当的水平，并建立表征蛋白质中以前类型的辅因子的基准。第二个目标是纠正被广泛用于结构优化和分子动力学模拟的力场中的缺陷。第二个目标是研究两种金属蛋白--羟胺氧化还原酶(HAO)和甲基COM还原酶(MCR)--活性部位的振动(和其他)光谱特性，这两种金属蛋白对生物圈的组成有重大影响，因此对人口的一般健康也有很大影响。HAO是全球氮循环中的一种关键酶，它含有一种铁邻苯二酚(P460)，可以催化氨转化为亚硝酸盐的最后一步。MCR是产甲烷的关键酶，含有一种氢化镍类化合物(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活性位点的独特功能，这些活性位点介导了它们新的化学作用。第三个目标是表征各种蛋白质模型中的偏四吡咯辅助因子的振动性质。模板中含有具有不同金属离子的四吡咯和具有不同氨基酸序列的外围取代基和多肽。还将对模型的单层组装进行调查。其目的是阐明合成蛋白质中辅因子的结构，并探索蛋白质基质对其氧化还原和电子性质的影响。

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.