Abstract: | The enthalpy of denaturation of lysozyme was determined by measuring the heat, capacity of an aqueous solution of this protein in the vicinity of the transition temperature, 46 °C at pH 1. Within experimental error the calorimetric, heat (56 ± 8 kcal/mole) was found to agree with the van't Hoff transition enthalpy (63 ± 6 kcal/mole) determined from optical rotation measurements as a function of temperature. This indicates that denaturation of this protein can be interpreted in terms of a two-state model. Successive measurements of the same sample showed, from several lines of evidence, that the transition was about 80% reversible for the particular environmental conditions and thermal history involved in the study. |