Mechanistic insights into arginine-mediated gluten solubility enhancement and aggregation inhibition across specific subunit and molecular scales

This study elucidates the mechanisms by which arginine (Arg⁺) inhibits gluten aggregation and enhances solubility, focusing on individual high-molecular-weight glutenin subunit (HMW-GS) using a set of HMW-GS deletion lines. Comparative analyses with Arg⁺, guanidine (Gdn⁺), and glycine (Gly) demonstrated increased solubility in HMW-GS deletion lines compared to wild type, particularly under Arg⁺ and Gdn⁺, following the order for HMW-GS deletion at: Bx7 > By8 > Ax1 > Dy12 > Dx2. Arg ⁺ enhanced solubility by quenching gluten structure, primarily restructuring hydrogen bonds, weakening hydrophobic interactions, destabilizing β-sheets, and facilitating β-turn and β-sheet transitions, alongside shifts from ggg to the least stable disulfide bond conformation (tgt). Molecular dynamics simulations revealed the heightened sensitivity of Dx2 to Arg⁺, driven by guanidino-mediated interactions and local crowding effects. These findings highlight the dominant role of the guanidino group in solubility enhancement, with carboxyl and alkyl groups playing supporting roles.