title: The Rise of Radicals in Bioinorganic Chemistry.
abstract: Prior to 1950, the consensus was that biological transformations occurred in two-electron steps, thereby avoiding the generation of free radicals. Dramatic advances in spectroscopy, biochemistry, and molecular biology have led to the realization that protein-based radicals participate in a vast array of vital biological mechanisms. Redox processes involving high-potential intermediates formed in reactions with O2are particularly susceptible to radical formation. Clusters of tyrosine (Tyr) and tryptophan (Trp) residues have been found in many O2-reactive enzymes, raising the possibility that they play an antioxidant protective role. In blue copper proteins with plastocyanin-like domains, Tyr/Trp clusters are uncommon in the low-potential single-domain electron-transfer proteins and in the two-domain copper nitrite reductases. The two-domain muticopper oxidases, however, exhibit clusters of Tyr and Trp residues near the trinuclear copper active site where O2is reduced. These clusters may play a protective role to ensure that reactive oxygen species are not liberated during O2reduction.
authors.affiliation: Beckman Institute, California Institute of Technology, 1200 E California Boulevard, Pasadena, CA 91125, USA.
authors.forename: Harry B
authors.initials: HB
authors.lastname: Gray
authors.affiliation: Beckman Institute, California Institute of Technology, 1200 E California Boulevard, Pasadena, CA 91125, USA.
authors.forename: Jay R
authors.initials: JR
authors.lastname: Winkler
keywords: Electron transfer; radicals; tryptophan; tyrosine