New insight into the alcohol induced conformational change and aggregation of the alkaline unfolded state of bovine β-lactoglobulinElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ra12057a

Accumulation of ordered protein aggregates (or amyloids) is responsible for several neurodegenerative diseases. β-Lactoglobulin (β-lg) an important globular milk protein, self-assembles to form amyloid-like fibrils on heating at low pH. But here we report for first time the self-assembly of β-lg from its alkaline unfolded state. The present work describes the folding and self-assembly of β-lg from a reversible unfolded state at pH 10.5 in the presence of methanol, 2-propanol, t -butanol and 2,2,2-trifluoroethanol (TFE). The extent of secondary and tertiary structure formation is in the order methanol < 2-propanol < t -butanol < TFE. Exposure of the hydrophobic core of the protein molecules in an apolar environment of TFE seems to promote intermolecular cluster formation. Methanol and TFE induce aggregation through the α-helical structure whereas isopropanol and t -butanol favour the formation of the β-structure leading to aggregation at higher concentrations. In vitro aggregation generates various nanometer structures such as nanofibrils, nanovesicles and nanotubes depending on the nature and concentration of the alcohols. Here we report for first time the self-assembly of β-lg from its alkaline unfolded state.