Introducing a Fast Method to Determine the Solubility and Metastable Zone Width for Proteins: Case Study Lysozyme

The phase diagrams of tetragonal hen egg white lysozyme containing besides. thermodynamic (solubility) also kinetic (nucleation) data were determined for pH values of 4.4, 5.0, and 6.0, 3 to 7 wt % Sodium chloride concentrations and lysozyme concentrations from 5 to 70 mg/mL by the use of a turbidity technique. This new technique offers a rapid, precise and reliable determination of nucleation and solubility points. These points can be Obtained simultaneously within 6 h. The errors of measurements are legs than +/- 0.9 degrees C for the solubility temperature and less than +/- 1.0 degrees C for the nucleation temperature. The solubility data obtained could be extended and described by a good correlation with literature data The solubility of lysozyme was found to decrease with increasing salt concentration while the nucleation points were observed more early with respect to salt addition, as a consequence the metastable zone is more narrow. The solubility of lysozyme is slightly reduced at higher values of the pH, and the nucleation point is observed later in time. The result is an increase, of the metastable zone width.