Variation of lysozyme solubility as a function of temperature in the presence of organic and inorganic salts

The regularity of salts in affecting lysozyme solubility (and other proteins having a basic pI) at pH 4.5 according to the lyotropic series has been completed by solubility curve measurements. The measurement of lysozyme/NaSCN solubility shows very small difference with lysozyme/KSCN solubility, confirming the slight influence of the nature of the cation. The solubility of lysozyme nitrate inserts between the values of lysozyme chloride and thiocyanate. Some organic salts have been tested as new crystallizing agents and the solubility curve of lysozyme in the presence of sodium para-toluenesulfonate has been determined. The solubility and the crystal form of lysozyme is affected differently by temperature changes (18 and 40°C), depending on the nature of the crystallizing agent.