Thermal and Solution Stability of Lysozyme in the Presence of Sucrose, Glucose, and Trehalose

The effect of the sugars sucrose, glucose, and trehalose on the structural and colloidal stability of lysozyme has been investigated using differential scanning calorimetry and quasi-elastic light scattering, respectively. While sugars are known to increase the temperature at which thermal denaturation of protein occurs, it is not clear if, under the same solution conditions, greater colloidal stability is achieved. The measurements were carried out on lysozyme in three different buffer solutions, 0.05 M sodium acetate (pH 4.6), 0.05 M sodium acetate with 5% (w/v) NaCl, and 10 mM sodium phosphate (pH 7.0). The results show that enhancement of structural stability in the presence of sugars is pH, salt concentration, and sugar dependent. Enhancement of colloidal stability in the presence of sugars, while also pH and salt concentration dependent, as expected, only correlates with increases in the structural stability when the solution behavior is not dominated by highly stabilizing electrostatic repulsive interactions.