Impact of macromolecular crowding on structure and properties of pepsin and trypsin.

The change of conformation of pepsin and trypsin in absence and presence of a high molecular crowding agent has been characterized using dynamic light scattering (DLS). Structural properties were investigated as a function of chemical denaturant concentrations, the guanidine hydrochloride (GdmCl). The results showed that Ficoll 400, macromolecular crowding, has a strong effect on the chemical denaturation process of these two proteins. The changes of measured hydrodynamic radius are attributed to the enhancement effect of the crowder agent due to the excluded volume effects. The data proved that the large size of a macromolecular crowder plays a crucial role on the conformation of a protein in its unfolded states. The values of interactions Parameter k of complex particles and a number of proteins n attached on the Ficoll 400 measured in different GdmCl concentrations. The effect of aging on the structure of complex are studied by small angle light scattering (SALS).