Aqueous Oxidation of Methanol by V-Containing Biocatalysts

wachs近年来，负载型氧化钒催化剂上CH3OH选择性氧化成HCHO已成为氧化物催化剂上气相氧化反应的模型体系，因为近年来广泛的基础表征和理论研究使该催化体系的构效关系得到了相当好的理解。然而，在水介质中，负载型氧化钒催化剂的选择性氧化反应存在问题，因为桥接的V-O-Support键会被水解。为了避免这个问题，无机-有机钒配合物通常被用作水介质中的氧化催化剂。例如，人体酶钒过氧化物酶（VHPO）是一种胰岛素模拟物，可以降低血液中的葡萄糖水平，是一种优秀的水氧化生物催化剂。因此，利用CH3OH氧化作为氧化还原2电子化学探针分子，将水介质中无机负载型氧化钒催化剂和v -配合物/ v -酶的气固氧化催化领域连接起来，是目前一个很好的研究机会。知识价值。本研究的目标是：(1)建立有效的表征方法和方法，用于研究HOOH和CH3OH环境下水相氧化钒催化剂的时间分辨原位和操作光谱研究（拉曼，UV-vis, 51V NMR， EPR，快速扫描ATR-IR和quick-XANES/EXAFS）；(2)将原位和operando光谱表征方法扩展到水相卤化钒氧化酶及其在HOOH和CH3OH环境下的功能有机模拟物；(3)应用先进的方法研究均相卤化钒氧化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、机理和动力学；(4)开发一种有效的方法，通过将酶锚定在固体载体上来“异质化”卤化钒过氧化物酶；(5)研究富水电子环境（通过电流施加）对均质和固定化卤化钒过氧化物酶的催化活性的影响；(6)研究位点定向诱变（基因工程）对VHPO催化活性的影响。更广泛的影响。提出的研究项目将把以往的气固CH3OH氧化催化研究扩展到CH3OH的液相氧化，并架起酶的无机催化与水生物无机催化的桥梁。研究无机和生物无机催化剂的水相催化的时间分辨原位和操作光谱方法的发展将得到显著的推进，并将对许多水相催化应用产生广泛的影响。时间分辨原位或operando光谱方法在酶催化和甲醇氧化钒过氧化物酶中的应用基本上是不存在的，因此，对这些反应的基本原理（机制，动力学，反应中间体，结构重排等）仍然知之甚少。该研究计划的一个成果将是开发一种更快、更高效、选择性的氧化反应生物催化剂，并对酶生物催化活性所必需的特征氨基酸残基（配体）的机制和功能有全面的基本了解。钒过氧化物酶可能为目前氧化反应中使用的传统无机催化剂提供一种“绿色”替代品，新的基本见解可能有助于改进药物、治疗方法和糖尿病管理的发展。钒卤素过氧化物酶催化的多用途性质也可能导致生物催化在多种工业应用中的改进。

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.