Sean Elliott investigates the connection between biological electron transfer chemistry and function of redox active proteins and enzymes, by using direct electrochemistry and spectroscopy. He joined the Department of Chemistry in 2002, following an EMBO Post-doctoral Fellowship at the University of Oxford. A recipient of the Gitner and Templeton Awards within the College of Arts and Sciences, he was promoted to Associate Professor of Chemistry in 2008.

The Elliott Group investigates the interplay between biological systems and redox-active species (e.g., metal ions, organic radicals, disulfide bonds, reactive oxygen species). Our emphasis is on the kinetic and thermodynamic basis for catalytic redox chemistry, as well as the molecular impact of metal ions and reactive oxygen species upon cells.

Bioelectrochemistry of Complex Metalloenzymes – The Elliott Group uses electrochemical tools, amongst others, to characterize the catalytic chemistry of redox active enzymes that are involved in multiple electron transfer steps. In particular, we use the technique of protein film voltammetry [PFV] to observe the reduction potentials of redox-cofactors that are a part of the essential machinery of an enzyme. Our laboratory interrogates a wide range of proteins and enzymes using this technique, and questions we are interested in vary from project to project.

Mechanisms of peroxidase catalysis have been investigated recently by our group using PFV. The bacterial cytochrome c peroxidases contain two heme groups, one of which is a five-coordinate active site of low reduction potential, and the other is a six-coordinate heme that is of higher potential, which serves a role in intermolecular electron transfer. We have certainly interrogated the enzyme from Nitrosomonas europaea, and determined that electroactive films of “NeCcP” give an electrochemical response indicating catalysis mediated by a n=1 ET step that is a part of the catalytic cycle.

Bacterial (multiheme) cytochromes are investigated in the Elliott Group using PFV. These include complex enzymes, such as the siroheme–dependent sulfite reductase, as well as simple cyt c-551 analogs and the less-simple cyt c-554, a tetraheme cytochrome.

The Redox Chemistry of Flavo- and Disulfide-enzymes – Other projects in the lab use electrochemistry as a way to probe the redox chemistry of enzymes involved in oxidative stress response, such as thioredoxin, glutaredoxin and thioredoxin reductases. This proven challenging due to the latent poor electrochemistry of disulfides, and the potential instability of flavo-proteins. However, we have been able to investigate a wide range of proteins such as thioredoxins and thioredoxin reductases. Thioredoxins are ubiquitous proteins that are small (~12 kDa), utilizing a surface-exposed disulfide bond as their means of storing and transferring electrons. Reduced thioredoxin is generated by a Trx reductase.

Techniques & Resources:

Protein film voltammetry (PFV) – a direct electrochemical suite of methods, is used to study protein-bound redox cofactors, allowing for the interrogation of previously inaccessible catalytic information

Bioinorganic Spectroscopies – the group makes use of optical absorption, fluorescence, and electron paramagnetic resonance spectroscopies routinely in the CIC, to further characterize the electronic structure and protein dynamics of redox enzymes.

Proteomic techniques are used to assess the impact of redox-active species (such as transition metals and reactive oxygen species) within living systems to investigate metal-ion import, packaging, and co-factor synthesis.