Aqueous Oxidation of Methanol by V-Containing Biocatalysts

0933294 WachsCH 3OH在负载型钒氧化物催化剂上选择性氧化成HCHO近年来已成为氧化物催化剂上气相氧化反应的模型体系，因为由于最近广泛的基本表征和理论研究，该催化体系的结构-活性关系变得相当好理解。然而，在水性介质中使用负载型钒氧化物催化剂的选择性氧化反应是有问题的，因为桥接V-O-载体键的水解。为了避免这个问题，无机-有机钒络合物通常用作水性介质中的氧化催化剂。例如，人酶钒卤代过氧化物酶（VHPO），一种降低血液中葡萄糖水平的胰岛素模拟物，是一种出色的水性氧化生物催化剂。因此，目前有一个很好的研究机会，桥梁的气-固氧化催化领域的无机负载钒氧化物催化剂和V-配合物/V-酶在水介质中使用甲醇氧化作为氧化还原2电子化学探针分子。本研究的目的是（1）建立有效的表征方法和途径，用于研究在水相中存在的HOOH和CH 3OH环境中的钒氧化物催化剂，并在毫秒到分钟的时间尺度上进行时间分辨原位和操作光谱研究（拉曼、UV-vis、51 V NMR、EPR、快速扫描ATR-IR和quick-XANES/EXAFS），（2）将原位和操作光谱表征方法扩展到水性钒卤代过氧化物酶及其在HOOH和CH 3OH环境中的功能有机模拟物，（3）应用先进的方法学研究了均相钒卤代过氧化物酶作为甲醇水相氧化生物催化剂的VOx结构、氧化态、反应中间体、反应机理和动力学。（4）发展了一种有效的将钒卤代过氧化物酶锚定在固体载体上的方法，（5）检测富水电子环境（通过电流施加）对均相和固定化钒卤代过氧化物酶的催化活性的催化作用，和（6）检测定点诱变（基因工程）对VHPO催化活性的作用。该研究方案将把以往气-固催化氧化甲醇的研究拓展到甲醇的液相氧化，并将无机催化与酶的水相生物无机催化结合起来。时间分辨的原位和operando光谱方法的发展，调查无机和生物无机催化剂的水相催化将显着推进这项事业，将有广泛的影响，许多水相催化应用。应用时间分辨的原位或operando光谱方法的酶催化和甲醇氧化钒卤代过氧化物酶基本上是不存在的，因此，仍然不知道这些反应的基本原理（机制，动力学，反应中间体，结构重排等）。拟议的研究计划的结果将是开发一种更快，更有效，更有选择性的生物催化剂用于氧化反应，并彻底了解酶生物催化活性所需的特征氨基酸残基（配体）的机制和功能。钒卤代过氧化物酶可以提供一个“绿色”的替代传统的无机催化剂目前用于氧化反应和新的基本见解可能有助于开发改进的药物，治疗和糖尿病的管理。钒卤代过氧化物酶催化的多用途性质也可能导致多种工业应用中的生物催化改进。

0933294 WachsThe selective oxidation of CH3OH to HCHO over supported vanadium oxide catalysts has emerged as the model system for gas phase oxidation reactions over oxide catalysts in recent years because the structure-activity relationship for this catalytic system is becoming fairly well understood due to recent extensive fundamental characterization and theoretical studies. Selective oxidation reactions with supported vanadium oxide catalysts in aqueous media, however, are problematic because hydrolysis of the bridging V-O-Support bonds. In order to circumvent this issue, inorganic-organic vanadium complexes are typically employed as oxidation catalysts in aqueous media. For example, the human enzyme vanadium haloperoxidase (VHPO), an insulin mimic that lowers glucose levels in blood, is an excellent aqueous oxidation biocatalyst. Thus, there is currently an excellent research opportunity to bridge the oxidation catalysis fields of gas-solids over inorganic supported vanadium oxide catalysts and V-complexes/V-enzymes in aqueous media by using CH3OH oxidation as a redox 2 electron chemical probe molecule.Intellectual Merit. The objectives of this proposed research are to (1) establish effective characterization methods and approaches for the study vanadium oxide catalysts in the aqueous phase in the presence of HOOH and CH3OH environments with time-resolved in situ and operando spectroscopy studies in the millisecond to minutes time scale (Raman, UV-vis, 51V NMR, EPR, rapid scan ATR-IR and quick-XANES/EXAFS), (2) extend the in situ and operando spectroscopic characterization methodologies to aqueous vanadium haloperoxidase and its functional organic mimics in HOOH and CH3OH environments, (3) apply the advanced methodologies to study the VOx structures, oxidation states, reaction intermediates, mechanism, and kinetics of homogeneous vanadium haloperoxidase as a biocatalyst for the aqueous phase oxidation of methanol, (4) develop an effective method to "heterogenize" vanadium haloperoxidase by anchoring the enzyme onto a solid support, (5) examine the catalytic effect of a rich aqueous electron environment (to be imposed by an electric current) on catalytic activity of homogeneous as well as immobilized vanadium haloperoxidase, and (6) examine the effect of site directed mutagenesis (genetic engineering) on the VHPO catalytic activity.Broader Impact. The proposed research program would extend the previous gas-solid CH3OH oxidation catalysis studies to liquid phase oxidation of CH3OH and also bridge inorganic catalysis with aqueous bioinorganic catalysis of enzymes. The development of time-resolved in situ and operando spectroscopic methodologies for investigating aqueous phase catalysis of inorganic and bioinorganic catalysts will be significantly advanced by this undertaking and will have wide reaching implications for numerous aqueous phase catalytic applications. Application of time-resolved in situ or operando spectroscopic approaches to enzyme catalysis and methanol oxidation by vanadium haloperoxidases is essentially nonexistent and, therefore, much is still not known about the fundamentals of these reactions (mechanism, kinetics, reaction intermediates, structural rearrangements, etc.). An outcome of the proposed research program will be the development of a faster, more efficient, selective biocatalyst for oxidation reactions and a thorough fundamental understanding of the mechanism and functionality of characteristic amino acid residues (ligands) necessary for enzyme biocatalytic activity. Vanadium haloperoxidase may provide a "green" alternative to traditional inorganic catalysts currently used in oxidation reactions and the new fundamental insights may assist in the development of improved pharmaceuticals, therapeutics, and management of diabetes. The versatile nature of vanadium haloperoxidase catalysis may also lead to biocatalytic improvements in multiple industrial applications.