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

Project: Research project

Project Details


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.

Effective start/end date7/15/076/30/11


  • National Science Foundation: $595,000.00


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