Figure 2. Effects of UV-A-exposure (at 50 J/cm²) on chaperone activity of WT αB-crystallin and its three deamidated mutant proteins. The chaperone activities of WT αB-crystallin and the three deamidated species were determined using insulin or citrate synthase as the substrates. A: Shows the aggregation of insulin as a target protein in the presence of dithiothreitol at room temperature. The aggregation was monitored at 360 nm (due to light scattering) as a function of time at 25 °C. The aggregation of insulin (100 μg in 10 mM phosphate buffer, pH 7.4, containing 100 mM NaCl) was initiated by 20 mM DTT at varying chaperone-to-target protein ratios. B: Aggregation of citrate synthase at 43 °C in presence of varying concentrations of αB-crystallin. During the thermal aggregation assay, 100 μg of citrate synthase (in 50 mM phosphate buffer, pH 7.8, containing 150 mM NaCl and 2 mM EDTA) was incubated at 43 °C with various concentrations of αB-crystallin to obtain the desired chaperone-to-target protein molar ratios.