Does arginine aggregate formation in aqueous solutions follow a two-step mechanism?

The formation of aggregates was studied in arginine aqueous solutions using light scattering. The main driving force for aggregate formation is hydrogen bonding between the arginine (Arg) amino acids, which is partially verified using density functional theory calculations. The measurement of energy loss during this process, coupled with Cryo-EM morphology data, indicates that these aggregates are in the solid state. The aggregation occurs in two steps, with a liquid intermediate stage. The investigation of the effect of pH and solute concentration on aggregate formation for other amino acid aqueous solutions verifies that aggregate formation is amino-acid specific, while small-sized clusters formed by weak interactions lead to large-sized aggregation. The water structure around amino acid molecules sheds light on the prediction of their aggregate formation. Homochirality is observed in the aggregates; its existence sheds light on the origin of protein homochirality.