Arginine: a Concentration Dependent Mechanism

Bovine β-lactoglobulin (β-lg), consisting of pronounced β-sheet content, have been chosen as a model protein which on prolonged thermal treatment forms large molecular aggregates similar to Alzheimer’s type amyloid fibrils. The effects of L-arginine (free base) in thermal aggregation process of β-lg were monitored at varying concentrations. Concentration dependent opposite behaviour has been reported here for the first time where 0.2-0.3 M concentration was optimized as an apparent critical concentration above which arginine acts as a suppressor and at below it behaves as a promoter of aggregation of β-lg. Solubility study and SDS-PAGE pattern followed by densitometric analysis shows this fact. Solution behaviour of arginine and its self assemblyformation were evidenced with the help of circular dichroism (CD) studies. The delocalized pi-pi (п→п) type of interaction is proposed to foster the energy stabilization during the attainment of planarity of the molecules accompanied with the self-clustering of arginine molecules.