FIGURE 3.

SEC measurements of the hinge cleavage of the native IgG1 and seven variants upon H₂O₂ incubation. a, SEC profiles of the variants after 4 days of H₂O₂ treatment. b, time-dependent response to the radical attack. The extent of the hinge cleavage was monitored at 220 nm and estimated by the percentage of the cleavage products to the intact molecule as a whole. The experimental conditions were as follows: IgG1 (1 mg/ml) in phosphate-buffered saline buffer, pH 7.4. The reaction was initiated by the addition of H₂O₂ to a final concentration of 20 mm, and the samples were incubated at 25 °C for 4 days. The reaction was stopped by catalase. Control is the native molecule incubated without H₂O₂.