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Cecilia Tommos

Tommos, Cecilia
Cecilia Tommos
Professor of Biochemistry and Biophysics
NMR / N313B
Graduate Education
Ph.D. Stockholm University, 1997
Postdoctoral Fellow, University of Pennsylvania, 2000
Joined Texas A&M in 2019

Using Protein Engineering, Protein Film Voltammetry & Spectroscopic Tools to Study High-Potential (Proton Coupled) Electron Transfer Processes

Nature uses a range of organic and metal-based redox-active molecules to carry out electron transfer (ET) and proton-coupled electron transfer (PCET) reactions. ET/PCET represents a key component of the broader research area of biochemistry and these types of reactions underpin many fundamental processes including photosynthesis and cellular respiration.

Redox proteins have been under intense scrutiny for some time. However, there is one type of redox cofactors that has proven difficult to characterize systematically and in detail. Thus, some proteins use one or several of their own amino acids as bona fide one-electron redox cofactors. The one-electron oxidized (radial) state of tyrosine, tryptophan, cysteine and glycine can be part of a catalytic mechanism or a multistep ET/PCET chain spanning tens of ångströms. Amino-acid radicals are highly oxidizing and reactive species. These properties make them uniquely suited to participate in difficult redox chemistry, but they also make amino-acid radicals hard to control and study experimentally. We have overcome this problem by creating a family of well-structured model proteins specifically designed to study tyrosine, tryptophan, and cysteine radicals. The so called α3X proteins are based on a three-helix bundle (α3) with a single aromatic residue at interior position 32 (X32). By combining the α3X system with nuclear magnetic resonance (NMR) spectroscopy, high-potential protein film voltammetry, site-specific incorporation of unnatural amino acids and transient absorption (TA) spectroscopy, we have gained a detailed picture of the redox properties of Y32, W32 and a range of Y32 analogs. This unique data set provides a guide to delineate redox reactions that occur in the more complex natural systems.

We now aim to expand the α3X protein family to study multistep ET/PCET involving chains of natural and unnatural Y and W residues. This work is done in collaboration with research groups at Caltech (TA spectroscopy) and Yale University (quantum chemical studies).