Orthorhombic lysozyme solubility.

The orthorhombic, or high-temperature, form of chicken egg-white lysozyme typically appears at temperatures >/=298 K. Solubility diagrams have been determined for this form of lysozyme from pH 4.0 to 5.4 in 0.2 pH increments using the micro-column technique. Data were collected in the 297-317 K temperature range which resulted in phase diagrams similar in overall shape to those obtained for the lower temperature tetragonal form. Specifically, the solubility increased with increasing temperature and decreased with increasing precipitant concentration. However, the solubility of the orthorhombic form is considerably less sensitive to temperature than the tetragonal form, resulting in a more flattened slope. On the other hand, pH effects on the high-temperature form were opposite to those on the low-temperature form. When holding the precipitant concentration constant, the solubility decreased with increasing pH for the orthorhombic form. Previous tetragonal data were incorporated with these orthorhombic data to produce intercept values. These values varied with both pH and precipitant concentration, but the general tendency of the slope was to decrease with increasing pH.