A comparative study of the thermal denaturation parameters of lysozyme in the dissolved and crystalline states

Differential scanning calorimetry was used for investigating the conformational changes of lysozyme resulting from the combined actions of temperature and of denaturants at various concentrations. The transition temperatures, for the protein in the dissolved and in the crystalline states (tetragonal crystals, crosslinked by glutaraldehyde), were thus investigated in a variety of environmental conditions. The effect of a wide range of alcohols demonstrates that lysozyme, whether in solution or crystalline, displays structural features which are on the whole strikingly similar. By contrast, in the case of urea this similarity becomes apparent only for concentrations higher than 4 M. Molecular interpretation of the data, as discussed in the text, is entirely consistent with information from X-ray studies.