Static and dynamic scattering of beta-lactoglobulin aggregates formed after heat-induced denaturation at pH 2

The structure and internal dynamics of beta-lactoglobulin aggregates formed after heat-induced denaturation at pH 2 and different ionic strengths were investigated using light, neutron, and X-ray scattering. Polydisperse aggr egates are formed with a rigid rodlike local structure with mass per unit l ength close to that of a string of beta-lactoglobulin monomers but with a s omewhat larger diameter. The persistence length decreases with increasing i onic strength from more than 600 nm at 0.013 M to 38 nm at 0.1 M. At ionic strengths of 0.1 and 0.2 M, a self-similar structure with fractal dimension s of 1.8 and 2.0 is seen by using light scattering. The concentration depen dence of the static structure factor and the internal dynamics are close to those of flexible linear chains. In contrast, a rigid behavior is observed at lower ionic strength (0.03 and 0.013 Mi. The persistence length of aggr egates formed at 0.013 M is reduced after dilution in 0.1 and 0.2 M ionic s trength solvents but remains larger than that of aggregates formed and dilu ted in 0.1 and 0.2 M. The ionic strength of formation is thus a determining factor for the structure. At pH 2, there is no evidence for a two-step agg regation process as was observed at pH 7.