[Research on conformational changes of trypsin in different concentrations of GuHCl by fluorescence spectra]

The existing of intermediate in the process of protein unfolding is necessary for studying the kinetic folding and unfolding pathway of protein. With trypsin as a model protein, the conformational changes of trypsin in the presence of different GuHCl concentrations were investigated by using fluorescence spectra (FR), and compared with the activity recovery of denatured trypsin. It was found that the maximum wavelength of FR of trypsin increases with the concentration of GuHCl increasing, and the maximum wavelength of FR of trypsin reaches the maximum when the concentration of GuHCl is 2 mol x L(-1), and then, the maximum wavelength of FR of trypsin decreases with the concentration of GuHCl increasing. There exists a intermediate state in the presence of low concentration of GuHCl. The conformation of the intermediate is different from the native and unfolding states. The maximum wavelength of FR of the intermediate is the maximum, and fluorescence intensity is the highest, while the bioactivity recovery is the lowest. The reasons for these were studied with the knowledge of the molecular structure.