Effect of sulfoxides on the thermal denaturation of hen lysozyme: A calorimetric and Raman study

A multidisciplinary study of the thermal denaturation of lysozyme in the presence of three sulfoxides with different length in hydrocarbon chain (DMSO, DESO, and DPSO) was carried out by means of DSC. Raman spectroscopy, and SDS-PAGE techniques. In particular, the T(d) and Delta H values obtained from the calorimetric measurements showed that lysozyme is partially unfolded by sulfoxides but most of the conformation holds native state. The sulfoxide denaturing ability increases in the order DPSO > DESO > DMSO. Moreover, only DMSO and DESO have a real effect in preventing the heat-induced inactivation of the protein and their Maximum heat-protective ability is reached when the DMSO and DESO amount is >= 25% w/w.