Functional ethanol-induced fibrils: Influence of solvents and temperature on amyloid-like aggregation of beta-lactoglobulin

Solvent-induced fibrillar aggregates of beta-lactoglobulin occur only in a certain balance between hydrophobic forces and electrostatic interactions. We hypothesize, that different hydrophobic solvent molecules as well as rising temperatures influence this equilibrium and thus the optimum to produce amyloid aggregates. Dimethyl sulfoxide (DMSO), methanol and ethanol all resulted in polydisperse solutions with worm-like and spherical-aggregates, albeit to different degrees: the volume fraction required for aggregation was DMSO (50%) > methanol (40%) > ethanol (30%) which does not reflect their hydrophobicity. Further solvent addition decreased the fibrillar aggregation again. Increasing the temperature by 10–20 K decreased the solvent concentration needed to induce amyloid-like aggregates. A targeted production of solvent-based amyloid-like aggregates is therefore not only dependent on the hydrophobicity of the solvents, but also on their direct interaction with the protein (denaturation).