Fourier-transform infrared spectroscopic investigation of the thermal denaturation of hen egg-white lysozyme dissolved in aqueous buffer and glycerol

The thermal denaturation of lysozyme dissolved in aqueous phosphate buffer (pH 5.1) and glycerol was studied by Fourier-transform infrared (FTIR) spec troscopy. In both solvents, a single temperature-induced conformational tra nsition was observed but at the distinctly different temperatures of 73 deg reesC in aqueous buffer and 94 +/- 2 degreesC in glycerol. No changes in th e secondary structure were observed in glycerol up to 90 degreesC. Thus, FT IR data were consistent with the formation of a highly ordered molten globu le state at temperatures below 90 degreesC followed by lysozyme unfolding a t higher temperatures in glycerol.