Non-heme Fe(IV)-oxo Intermediates: Structure and Reactivity

该奖项由宾夕法尼亚州立大学分子与细胞生物科学系生物分子系统集群和化学系无机、生物无机和有机金属化学项目共同资助，支持宾夕法尼亚州立大学卡斯滕·克雷布斯教授和约瑟夫·博林格教授对参与脯氨酸-4-羟基化酶（P4H）活性的铁(IV)-氧中间体的研究。许多有机分子的生物合成需要选择性氧化反应。特别重要的是脂肪族碳氢键的氧化。这个反应特别具有挑战性，因为C-H键的惰性需要极强的氧化剂。此外，大多数有机分子含有多个C-H键，可以被强氧化剂靶向，因此可能导致反应混合物。在自然界中，这些反应是在金属酶活性位点进行的。这些酶能够与分子氧反应，产生高活性的中间体。这些中间体有足够的活性来激活惰性的碳氢键。由氧配体配位的+IV氧化态含铁的配合物，也称为Fe(IV)-氧或铁基物质，可以说是已知的最强大、最通用和最环保的氧化剂。对这些中间体的结构和反应性的详细了解可以通过动力学和光谱方法的结合来获得。动力学方法允许中间体被捕获，并提供有关其形成和衰变速度的信息。含有大量活性物质的样品可以通过各种光谱方法进行分析，从而提供对其化学性质的详细了解。最近，Bollinger/Krebs小组报道了几种不含血红素辅助因子的铁基中间体（又称非血红素铁基复合物），并对其进行了详细的表征。所研究的酶催化其底物的脂肪族C-H键的羟基化。这项工作现在将扩展到研究其他几种催化不同氧化结果的非血红素铁酶，包括卤化。预计这些研究将为这些酶用于氧化有机底物的机制提供前所未有的见解。就更广泛的影响而言，这项工作的一个关键特征是它是高度跨学科的，符合近年来科学的总体趋势。促进在多个密切相关的研究领域的专业知识的发展是有效培养下一代科学家的必要条件。本课题是在无机化学、生物化学、分子生物学、物理化学等学科交叉的基础上开展的。特别强调酶动力学、配位化学和光谱学的概念。因此，它将促进这些领域的独特培训。这些合作项目将组织一次夏季专题讨论会，讨论他们的研究主题——反应中间体的表征。作为本次研讨会的一部分，将为参加研讨会的学生和研究人员举办研讨会。在此研讨会期间，参加者将接受本研究领域的实验方法和相关数据解释方面的培训。期望学生和研究人员能够更容易地将这些方法应用到他们自己的研究中。

This award, co-funded by the Biomolecular Systems Cluster in the Division of Molecular and Cellular Biosciences and the Inorganic, Bioinorganic and Organometallic Chemistry program in the Division of Chemistry supports research by Professors Carsten Krebs and Joseph Bollinger at the Pennsylvania State University to study Fe(IV)-oxo intermediates involved in the activity of prolyl-4-hydroxylase (P4H).The biosyntheses of many organic molecules require selective oxidation reactions. Of particular importance is the oxidation of aliphatic C-H bonds. This reaction is particularly challenging, because the inertness of the C-H bond requires extremely strong oxidants. Furthermore, most organic molecules contain multiple C-H bonds that could be targeted by the strong oxidant, thus potentially leading to reaction mixtures. In nature, these reactions are carried out at metalloenzyme active sites. The enzymes are capable of reacting with molecular oxygen to create highly reactive intermediates. These intermediates are sufficiently reactive to activate the inert C-H bond. Complexes containing iron in the +IV oxidation state coordinated by an oxo ligand, also known as the Fe(IV)-oxo or ferryl species, are arguably the most powerful, versatile, and environmentally friendly oxidants known. Detailed insight into the structure and reactivity of such intermediates can be obtained by a combination of kinetic and spectroscopic methods. The kinetic methods allow the intermediate to be trapped and provide information about how fast it forms and decays. Samples containing large amounts of the reactive species can then be analyzed by various spectroscopic methods, which provide detailed insight into their chemical nature. Several ferryl intermediates that do not contain the heme cofactor (a.k.a. non-heme ferryl complexes) have recently been reported and characterized in detail by the Bollinger/Krebs group. The enzymes under investigation catalyze the hydroxylation of aliphatic C-H bonds of their substrates. This work will now be extended to study several other non-heme-iron enzymes that catalyze distinct oxidation outcomes, including halogenation. It is expected that these studies will provide unprecedented insight into the mechanisms that these enzymes employ to oxidize organic substrates. In terms of the broader impact, a key feature of this work is that it is highly interdisciplinary, in line with the general trend in science in recent years. Facilitating the development of expertise in multiple, distantly related research areas is imperative for effectively training the next generation of scientists. This project is carried out at the interfaces of inorganic chemistry, biochemistry, molecular biology, and physical chemistry. In particular, it emphasizes concepts of enzyme kinetics, coordination chemistry, and spectroscopy. Thus, it will facilitate unique training in these areas. The co-PIs will organize a summer symposium on the subject of their research, characterization of reaction intermediates. As part of this symposium, there will be a workshop for students and researchers attending the symposium. During this workshop, participants will be trained in the experimental methods of this research area and the associated interpretation of data. The expectation is that students and researchers will be able to adapt these methods more easily to their own research.