Phase equilibria for salt-induced lysozyme precipitation: Effect of salt concentration and pH

The salt-induced precipitation of lysozyme from aqueous solutions was studied at 25 °C and various pH values by cloud-point investigations, precipitation experiments (analysing the compositions of the coexisting phases) and microscopic investigations of the precipitates. Sodium sulphate as well as ammonium sulphate were used to induce the precipitation. The experimental results are discussed and used to develop a scheme of the phase equilibrium in water-rich aqueous solutions of lysozyme and either Na2SO4 or (NH4)2SO4.