THERMALLY-INDUCED HYDROGEN-EXCHANGE PROCESSES IN SMALL PROTEINS AS SEEN BY FTIR SPECTROSCOPY

Fourier-transform infrared (FTIR) spectroscopy has been used to study the thermally induced exchange characteristics of those backbone amide protons which persist H-D exchange at ambient conditions in ribonucle ase A, in wild type ribonuclease T1 and some of its variants, and in t he histone-like protein HBsu, The H-D exchange processes were induced by increasing the thermal energy of the protein solutions in two ways: (i) by linearly increasing the temperature, and (ii) by a temperature jump, To trace the H-D exchange in the proteins, various infrared abs orption bands known to be sensitive to H-D exchange were used as speci fic monitors, Characteristic H-D exchange curves were obtained from wh ich the endpoints (T-H/D) of H-D exchange could be determined. The H-D exchange curves, the T-H/D-values and the phase transition temperatur es T-M were used to estimate the structural flexibility and stability of the given proteins, It is suggested that time-resolved FTIR spectro scopy can be used to determine global stability parameters of proteins . (C) 1996 Wiley-Liss, Inc.