Measuring Lysozyme Solubility as a Function of pH, Portillo, Carmen
College of Science and Mathematics
Poor protein solubility is a major problem in the development of protein pharmaceuticals. Solubility determines how concentrated drugs are in the system. When medication is injected into the system, higher concentrations are needed for effective results. Therefore, strategies for improving protein solubility are of great interest to the pharmaceutical industry. In this study, the solubility of lysozyme was measured as a function of pH. Although these proteins are not necessarily pharmaceutically relevant, the information obtained from them could hopefully be applied to pharmaceutically relevant proteins. It was previously thought that solubility would be minimal at the isoelectric point and then would continually increase with increasing net charge on both sides of the isoelectric point. Up to this point, results have remained consistent within a minimum selected range of pH values. When the range is extended, deviations in the expected pattern of increased solubility with respect to pH are observed. In the pH range of 4.0 to 5.5, predicted solubility values at 1.1 M consistently increased with pH. These values are trusted since they were predicted from calibration curves that contained a R2 values very close to 1, and were verified experimentally. We infer that with lower pH values, the solubility of lysozyme protein will continue to decrease; and thus will be verified with future experimentation.
