# Reactivity-Activation of O(2) or NO in Copper and Heme-Cu Coordination Complexes

> **NIH NIH R35** · JOHNS HOPKINS UNIVERSITY · 2021 · $124,827

## Abstract

Project Summary/Abstract:
This equipment supplement project proposal seeks funds to purchase a Cold-Spray Ionization
Mass Spectrometer to carry out CSI-MS experiments, a powerful approach to characterizing
typically unstable reactive intermediates. The scientific objectives include the design, synthesis &
investigation of synthetic models which will aid the elucidation of fundamental aspects of structure,
M-ligation, spectroscopy and reactivity relevant to copper and heme/M (M = Cu, Fe) processing
of molecular oxygen (O2(g)) and nitric oxide (NO(g)). Copper proteins of concern include lytic
polysaccharide monooxygenases, Cu-methane monooxygenases, the enzyme family which
includes peptidylglycine monooxygenase, and a binuclear copper protein, NspF. Biochemical
research has raised questions concerning the nature of their active sites and the mechanism(s)
of action involving O2(g) activation and C-H hydroxylation. LPMOs may be peroxygenases, new
pMMO studies suggest a mono-Cu active site, and it is now questioned as to whether DBM and
PHM activate O2 with a Cu vs a Cu2 center. There are clear needs to synthesize and characterize
the copper(II)-oxyl (CuII-O·) species; it has the oxidizing ability needed for the difficult biological
substrates. We also plan to elucidate fundamentals critical to the O-O reductive cleavage process
occurring in proteins which process O2. Also, we will generate and characterize the structures,
physical properties and reactivity of new high-valent binuclear Cu(II)-O-Cu(III) complexes.
Proposed research will also focus on the heme-copper active site of cytochrome c oxidases,
where O2-binds and is reductively cleaved to give two mole-equiv water. The study of synthetic
models aids an understanding of structure, O2-binding, proton or H-bonding facilitated O-O
cleavage, and the role of the active-site phenol. Investigations are proposed to further investigate
the mechanisms of O-O cleavage in heme-peroxo-copper constructs, where the porphyrinate, the
Fe axial ligand and the copper ligand are systematically varied. A variety of planned approaches
include study of new chelates for copper which possess three N-donors and an appended phenol.
NO(g) synthetic model chemistry sub-projects with copper and heme-M will also be carried out.
With Cu complexes, the focus will be on NO(g) reductive coupling, and study of mechanisms
pertaining to the NO(g) metal-binding, formation of the N–N bond giving putative hyponitrite N2O22–
intermediates, and proton and/or H-bonding contributions to N–O cleavage and N2O formation.
Heme/Fe (or Cu) mediated NO(g) coupling is critical in NO-Reductases and synthetic models for
this process will be investigated. Metal-peroxynitrite (PN, from metal ion + O2(g) + NO(g)) reactivity,
especially toward CO2, will also be studied as relevant to biological activity.

## Key facts

- **NIH application ID:** 10389306
- **Project number:** 3R35GM139536-01S1
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** KENNETH D. KARLIN
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $124,827
- **Award type:** 3
- **Project period:** 2021-02-01 → 2026-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10389306

## Citation

> US National Institutes of Health, RePORTER application 10389306, Reactivity-Activation of O(2) or NO in Copper and Heme-Cu Coordination Complexes (3R35GM139536-01S1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10389306. Licensed CC0.

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