Antioxidant reactivity toward nitroxide probes anchored into human serum albumin. A new model for studying antioxidant repairing capacity of protein radicals

Abstract

A new strategy to evaluate accessibility of antioxidants to radical proteins has been developed using nitroxide prefluorescent probes anchored into human serum albumin (HSA). Binding association constants for the nitroxide probes C 343T and QT with HSA were 5 × 10 4 and 9 × 10 4 M −1, respectively. Rate constants for the nitroxide reduction by antioxidants in HSA were determined finding k HSA/ k buffer ratio of 0.8, 1.9, and 0.075 for ascorbic acid, Trolox, and caffeic acid, respectively, for the nitroxide C 343T reduction.