Radiation chemists look at damage in redox proteins induced by X-rays.

The three-dimensional structure of proteins, especially as determined by X-ray crystallography, is critical to the understanding of their function. However, the X-ray exposure may lead to damage that must be recognized and understood to interpret the crystallographic results. This is especially relevant for proteins with transition metal ions that can be oxidized or reduced.

Intramolecular Electron Transfer in the Bacterial Two-Domain Multicopper Oxidase mgLAC.

The kinetics of the intramolecular electron transfer process in mgLAC, a bacterial two-domain multicopper oxidase (MCO), were investigated by pulse radiolysis. The reaction is initiated by CO2(-) radicals produced in anaerobic, aqueous solutions of the enzyme by microsecond pulses of radiation. A sequence of pulses of CO2(-) radicals enables examination of the reductive half-cycle of the MCO catalysis.

Long-Range Electron Transfer in Engineered Azurins Exhibits Marcus Inverted Region Behavior.

The Marcus theory of electron transfer (ET) predicts that while the ET rate constants increase with rising driving force until it equals a reaction's reorganization energy, at higher driving force the ET rate decreases, having reached the Marcus inverted region. While experimental evidence of the inverted region has been reported for organic and inorganic ET reactions as well as for proteins conjugated with ancillary redox moieties, evidence of the inverted region in a "protein-only" system has remained elusive. We herein provide such evidence in a series of nonderivatized proteins.

Multicopper oxidases: intramolecular electron transfer and O2 reduction.

The multicopper oxidases are an intriguing, widespread family of enzymes that catalyze the reduction of O2 to water by a variety of single-electron and multiple-electron reducing agents. The structure and properties of the copper binding sites responsible for the latter chemical transformations have been studied for over 40 years and a detailed picture is emerging. This review focuses particularly on the kinetics of internal electron transfer between the type 1 (blue) copper site and the trinuclear center, as well as on the nature of the intermediates formed in the oxygen reduction process.