FIGURE 7.
sCT fibrillation times are pH-dependent, and ThT signals scale with heparin concentration. A, fibrillation lag times for heparin-induced fibrillation of sCT-OH, sCT-NH2, and sCTH17A-OH. All samples contain 0.5 mg/ml sCT, 150 μg/ml heparin, 40 μm ThT, and 20 mm citrate-phosphate buffer. t½ values are a median of empirical sigmoidal fits to individual ThT fibrillation traces. B, heparin addition to preformed sCT fibrils with increase in ThT signal. The intercept is at ∼1.4 heparin disaccharide units (calculated using a molecular mass of 665.4 g/mol for a heparin disaccharide unit sodium salt) per sCT monomer. C, ThT mean end point intensity at pH 5.5 with varying heparin concentrations indicates an intercept at a ratio of 1.5 disaccharides per sCT monomer. a.u., arbitrary units. Error bars represent S.D.