THERMODYNAMICS OF SOLUTION OF LYSOZYME CRYSTALS

The solubility of crystalline hen egg white lysozyme in 1.7 m (10%) NaCl has been studied in the pH range 2.6-5.0 and at temperatures of 21.7, 29.5, and 42.7 °. The pH dependence of solubility can be used to evaluate the difference between the number of protons bound by a lysozyme molecule in the crystal and in solution. Differences were observed which do not appear to be due to intermolecular protein-protein interactions. These differences may indicate structural differences between enzyme in the crystal and in solution. Temperature dependence of solubility data were used to evaluate enthalpies and entropies of solution for the crystal. It can be shown that there is a negative contribution to the entropy of solution when a crystal goes into solution. This suggests that crystalline phase solvent may be less ordered than bulk solvent in the solution phase. © 1969.