Concentration regimes and denaturation effects on the conformational changes of α-chymotrypsin by viscosity and dynamic light scattering measurements.

This work focused on the conformational changes of α-chymotrypsin from bovine pancreas for various concentrations as well as the effects of chemical denaturation and organic solvents using both of viscosity and dynamic light scattering techniques. A wide range of concentrations varying between 0.1 and 30 mg/ml is tested to determine the critical concentration c** that separates the extremely dilute regime to the dilute regime and the overlapping concentration c* that separates the dilute regime to the semi-dilute regime. The knowledge of α-chymotrypsin folding process is followed for a range of chemical denaturant concentrations varying from 1 to 6 M. We showed that the α-chymotrypsin folds through a cooperative two-state transition without detectable kinetic intermediates and the formation of 50% unfolded happens for 5.5 M of urea or guanidinium chloride (GdmCl) concentrations. The action modes of the acetonitrile on the conformational changes of α-chymotrypsin are also achieved for concentrations varying between 10 and 50%.