Comparative two-dimensional Fourier transform infrared correlation spectroscopic study on the spontaneous, pressure-, and temperature-enhanced H/D exchange in α-lactalbumin

Two-dimensional Fourier transform infrared FT-IR was applied for the examination of the H/D exchange process in D2O solutions of bovine alpha-lactalbumin. The slow spontaneous H/D exchange at 25 degrees C was compared with pressure-enhanced and temperature-enhanced H/D exchange. The HID-exchange process, which takes 48 h at 25 degrees C and under atmospheric pressure, is completed within 3 h when pressure is gradually elevated up to 180 MPa, or when temperature is increased up to 42.5 degrees C, Although the slow room-temperature HID exchange and the fast pressure or temperature-enhanced H/D exchange feature a high degree of similarity between the corresponding second-derivative spectra, the two-dimensional (2D) FT-IR correlation maps revealed that upon the heat treatment the order in which the H/D exchange takes place in the structural domains of alpha-lactalbumin is altered. It has been observed that these differences can be explained in light of the known properties of alpha-lactalbumin and the crystallographic data.