# Synthetic Nonheme Iron O2 Activation and S-Oxygenation

> **NIH NIH R01** · JOHNS HOPKINS UNIVERSITY · 2021 · $358,071

## Abstract

Project Summary
This proposal focuses on the fundamental structural, functional, and mechanistic requirements for the activation
of O2 by nonheme iron complexes and related enzymes. Dioxygen is processed by nonheme iron centers in
biology as part of a range of critical functions, including the mono- and di-oxygenation of organic substrates, as
well as the formation of C-S and C-halide bonds. The oxygenation of organic substrates is mediated by nonheme
iron oxygenases, and an important subclass of these enzymes oxygenate sulfur sites bound to the iron center.
This subclass includes the thiol dioxygenases (TDOs), such as mammalian cysteine dioxygenase (CDO), and
the persulfide dioxygenases (PDOs), such as mammalian ethylmalonic encephalopathy protein (ETHE1). The
mechanisms of action of the TDOs and PDOs are poorly understood, although several common iron/oxygen
intermediates have been proposed. The sulfoxide synthases EgtB and OvoA are related mononuclear, nonheme
Fe enzymes that utilize O2 to carry out both S-oxygenation and C-S bond formation, as does isopenicillin N
synthase (IPNS), which employs Fe and O2 in the biosynthetic pathway of penicillin. The C-S bond formation in
IPNS occurs via selective carbon radical addition to a sulfur bound to Fe, a process similar to what occurs in
nonheme Fe α-KG halogenases. A number of fundamental mechanistic questions remain unanswered regarding
these enzymes. This proposal describes the synthesis and study of synthetic nonheme iron compounds
designed to model certain aspects of structure and function related to the TDO/PDOs, sulfoxide synthases, IPNS,
and the α-KG halogenases. Proposed efforts also include select studies on the enzyme CDO, which parallel and
complement the model compounds. A focus of the proposal is to characterize reactive, Fe/O2-derived species
that are analogs of key intermediates thought to be important in nonheme iron-mediated O2 activation.
Characterization of these species in structurally well-defined synthetic complexes will provide precedent and
support for the analogous, proposed intermediates in the enzymatic systems. The feasibility of proposed, key
bond-making/bond-breaking steps will be established. Methods designed to trap and/or characterize Fe/O2
species will be used, including low temperatures and a suite of advanced spectroscopies (low-temperature UV-
vis, electron paramagnetic resonance, resonance Raman, Mössbauer, X-ray absorption). Computational studies
will be employed to help interpret and predict structural and spectroscopic properties as well as reaction
pathways. The selective reactivity of carbon radicals with iron-heteroatom bonds will also be assessed, taking
advantage of a unique set of new, structurally characterized ferric hydroxide complexes. These studies should
lead to significant advances in our fundamental knowledge regarding how nonheme Fe enzymes activate O2
and selectively oxidize substrates. This knowledge should also provide guidance for the desi...

## Key facts

- **NIH application ID:** 10218201
- **Project number:** 5R01GM119374-06
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** David P Goldberg
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $358,071
- **Award type:** 5
- **Project period:** 2016-08-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10218201

## Citation

> US National Institutes of Health, RePORTER application 10218201, Synthetic Nonheme Iron O2 Activation and S-Oxygenation (5R01GM119374-06). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10218201. Licensed CC0.

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