| 초록 |
Liquid-liquid phase-separation data were obtained for aqueous saline solutions of lysozyme. Thermooptical analysis (TOA) provides a simple, rapid, and reliable experimental method to determine cloud-point curves of aqueous protein solution systems. The cloud-point temperature(CPT) was measured as a function of salt type and salt concentration at pH 4.0, 7.0 and 10.0. Salts used included those from mono and divalent cations and anions. For the monovalent cations studied, as salt concentration increases, the CPT increases. For divalent cations, as salt concentration rises, a maximum in the CPT is observed and attributed to ion binding to the protein surface and subsequent water structuring. For anions at fixed salt concentration, the CPT decreases with rising anion kosmotropic character. Comparison of CPTs for pH 4.0, 7.0 and 10.0 revealed two trends. At low ionic strength for a given salt, differences in CPT can be explained in terms of repulsive electrostatic interactions between protein molecules, while at higher ionic strength, differences can be attributed to hydration forces. |
