pH-dependent aggregation of partially unfolded titin Ig constructs and protection by sHSPs. Titin fragments were denatured in 8 mol/l of urea and then diluted 1:50 in neutral (pH 7.2) or acidic (pH 6.7) Tris/HCl buffer (30 mmol/l). Aggregation was determined by measuring the absorbance at 320 nm for up to 30 min. (A) Lack of aggregation of the mostly disordered segments, N2-Bus, N2-B, and PEVK, at normal and acidic pH. (B) Varied aggregation propensity of Ig-rich constructs, I9-12 and N2-A, at normal and acidic pH. (C) Protection by αB-crystallin against aggregation of the N2-A construct in pH 6.7 buffer at different N2-A/αB-crystallin molar ratios. (D) Lack of an anti-aggregation effect of HSP27 on N2-A at pH 6.7. All data were normalized to the absorbance value of N2-A at pH 6.7 at the 30-min time point and represent means ± SD (n = 6).