233 research outputs found
Formal Reduction Potential of 3,5-Difluorotyrosine in a Structured Protein: Insight into Multistep Radical Transfer
The reversible YâOâą/YâOH redox properties of the α[subscript 3]Y model protein allow access to the electrochemical and thermodynamic properties of 3,5-difluorotyrosine. The unnatural amino acid has been incorporated at position 32, the dedicated radical site in α[subscript 3]Y, by in vivo nonsense codon suppression. Incorporation of 3,5-difluorotyrosine gives rise to very minor structural changes in the protein scaffold at pH values below the apparent pK (8.0 ± 0.1) of the unnatural residue. Square-wave voltammetry on α[subscript 3](3,5)F[subscript 2]Y provides an E°âČ(YâOâą/YâOH) of 1026 ± 4 mV versus the normal hydrogen electrode (pH 5.70 ± 0.02) and shows that the fluoro substitutions lower the E°âČ by â30 ± 3 mV. These results illustrate the utility of combining the optimized α[subscript 3]Y tyrosine radical system with in vivo nonsense codon suppression to obtain the formal reduction potential of an unnatural aromatic residue residing within a well-structured protein. It is further observed that the protein E°âČ values differ significantly from peak potentials derived from irreversible voltammograms of the corresponding aqueous species. This is notable because solution potentials have been the main thermodynamic data available for amino acid radicals. The findings in this paper are discussed relative to recent mechanistic studies of the multistep radical-transfer process in Escherichia coli ribonucleotide reductase site-specifically labeled with unnatural tyrosine residues.National Institutes of Health (U.S.) (Grant GM29595
Volcano Activity Relationships for Proton-Coupled Electron Transfer Reactions in Electrocatalysis
Electrocatalytic Hydrogen Evolution in Acidic Water with Molecular Cobalt Tetraazamacrocycles
Molecular Catalysis of Electrochemical Reactions. Cyclic Voltammetry of Systems Approaching Reversibility
Photocatalytic Hydrogen Production Based on a Serial MetalâSalen Complexes and the Reaction Mechanism
Fundamental Input of Analytical Electrochemistry in the Determination of Intermediates and Reaction Mechanisms in Electrosynthetic Processes
Electrografting of Carbon Surfaces with Aliphatic Chains and its Effect on the Rectification of Ferrocene as Redox Probe in Solution
Linkage between Fluorescence and Electrochemical Properties of Imidazolium Compounds in Acetonitrile Solution
Proton Relays in Molecular Catalysis of Electrochemical Reactions: Origin and Limitations of the Boosting Effect
The Role of Nonbonded Sulfur-Oxygen Interaction in the Dissociative Electron Transfer to Nitro-Substituted Arenesulfenyl Chlorides
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