IRBP antioxidant activity assessed by the ferryl myoglobin/ABTS assay. (A) The assay monitors the ability to inhibit oxidation of 2,2'-azinobis [3-ethylbenzothiazoline-6-sulfonate] (ABTS; colorless) to the cationic radical ABTS•+ (green) by metmyoglobin. (B) Kinetics of ABTS•+ formation in the presence of buffer, ovalbumin, Trolox, bIRBP and NEM-modified bIRBP. Representative reaction wells at the conclusion of the incubation are shown from top to bottom for each condition respectively. (C) Dependence of ABTS•+ concentration on the concentration of ovalbumin, Trolox, and bIRBP. 750 nm absorbance measurements were taken at 5 min. Error bars, ± SE (N=3). Curves represent fits to first order exponential decay.