Growth and structure of aggregates of heat-denatured β-Lactoglobulin

Summary The aggregation of the globular protein β-lactoglobulin after heat-denaturation was studied in aqueous solution at pH 7 using static and dynamic light scattering. The structure of the aggregates is self-similar with fractal dimension 2.0. Size exclusion chromatography and dynamic light scattering measurements show that the aggregates have a broad size distribution. Initially clusters of about 85 proteins and 15 nm radius are formed which are the elementary units of the larger fractal aggregates. At low ionic strength the formation of the larger aggregates is impeded by electrostatic interactions.
The structure of the aggregates is independent of the concentration and the temperature. The rate of aggregation has an Arrhenius temperature dependence with an activation energy of about 350 kJ/mol weakly dependent on the concentration. The apparent reaction order of the aggregation is 1.5. In the mixture both variants A and B have the same aggregation rate. The gel time increases with decreasing concentration and diverges at about 0.7g L⁻¹. At lower concentration the aggregate growth stagnates when all protein has aggregated.