We conduct research of relevance to health, energy and the environment.
Enzymatic Redox Chemistry: Enzymes catalyze oxidative processes vital to life using redox-active transition metal ions. These species are found in minerals, in advanced materials and many industrial processes. In biological systems, they mediate redox reactions over a range of timescales and distances.
Redox reactions can be highly selective in protein environments. Isolated radicals are formed at conserved tyrosine side chains among families of proteins which function as enzymes. Tyrosyl radicals also catalyze reactions that destroy proteins and disrupt normal physiologic functions.
We are examing biosynthetic utilization of molecular oxygen as well as its production from water. Remarkably, tyrosyl radicals mediate both processes. Ultimately, we aim to understand how metalloproteins mediate selective catalytic amino acid radical formation by "long-range"/outer-sphere proton-coupled electron transfer. One subject is cyclooxygenase-2 (below right), which structurally resembles myeloperoxidase (below left), a mammalian hemoprotein of the immune response.
Heavy Atom Isotope Effects: The interactions of transition metals with gases are characterized by electron transfer reactions and heavy atom isotope effects. We have shown how oxygen-18 isotope effects can be measured at natural abundance with competitive techniques and isotope ratio mass spectrometry. The results shed light on chemical structures and reaction mechanisms.
Approaches to simultaneously measure and predict heavy atom isotope effects on a range of chemical and biological redox processes are under investigation. The methods developed can illuminate water oxidation transition states in natural and artificial photosynthetic reactions. In this effort, we are targeting metal-oxide species to produce solar hydrogen as an alternative to fossil fuels.