Pressure effects on protein secondary structure and hydrogen deuterium exchange in chymotrypsinogen: a Fourier transform infrared spectroscopic study.

Infrared spectra of chymotrypsinogen in 2H2O have been measured as a function of pressure up to 30 kbar. An irreversible denaturation is induced at 7.6 kbar where the contributions of the random coil and turn conformational substructures to the protein structure increase dramatically at the expense of the contributions of the alpha-helix and beta-sheet substructures. The pressure at which denaturation starts is higher when pressure is applied more slowly. The rate of H-2H exchange of the interior labile protons on the amide groups is dramatically increased by external pressure and is closely associated with the global conformational structure of the protein. This suggest that pressure denaturation involves the bulk of the molecule. The results are compared with those obtained from other experimental approaches and with temperature-induced denaturation.