BLGA protein solutions at high ionic strength: Vanishing attractive interactions and "frustrated" aggregation

Aggregation in disperse systems is generally induced or promoted by screening of the electrostatic interactions via the addition of salts. By combining static and dynamic light scattering results from solutions of a simple milk protein, beta-lactoglobulin A (BLGA), we show that clustering in protein solutions can sometimes be conversely hampered by electrolytes. This peculiar behaviour is fully correlated with a marked non-monotonic trend of the interparticle interactions as a function of the solution ionic strength. Data obtained in conditions where the protein charge has similar absolute value but opposite sign suggest that interactions depend on the specific surface charge distribution.