Determination of the Thermodynamics of B-lactoglobulin Aggregation Using Ultra Violet Light Scattering Spectroscopy

The problem of protein aggregation is widely studied across a number of disciplines, where understanding the behaviour of the protein monomer, and its behaviour with co-solutes is imperative in order to devise solutions to the problem. Here we present a method for measuring the kinetics of protein aggregation based on ultra violet light scattering spectroscopy (UVLSS) across a range of NaCl conditions. Through measurement of wavelength dependant scattering and using the model protein β-lactoglobulin, it is possible to isolate the thermodynamic contributions to thermal unfolding. We show that increasing NaCl concentration decreases the free energy of unfolding which is dominated by the decrease of the enthalpy contribution. This contribution is significantly larger than the decrease in change in entropy observed at higher salt concentrations between the folded and unfolded states.