Unlocking molecular dynamics: incorporation of volumetric insights into L-glutamic acid and quaternary ammonium...

This study investigates how L-glutamic acid (Glu) behaves in water and in aqueous solutions of tetrapropyl bromide (TPAB) and tetrabutyl bromide (TBAB) across temperatures from 293.15 to 313.15 K. Using volumetric methods, researchers measured solution densities and derived parameters like apparent and partial molar volumes, molar expansibility, Hepler's constant, and transfer volume to analyze ion-on and ion-solvent interactions. The rise in partial molar volume ( $V_{\varphi }$ ) with increasing molality of Glu indicates stronger solute-solvent interactions as the concentration of amino acids in the solution grows, The positive and increasing values of $V_{\varphi }^0$ with temperature and TPAB $/$ TBAB concentration suggest enhanced ion-solvent and hydrophilic interactions, indicative of stronger electrostrictive effects. The interaction analysis revealed that the ion-ion, ion-hydrophilic, and hydrophilic-hydrophilic forces between the zwitterionic centers ${(-\text{COO}}^{-}$ and ${-\text{NH}}_3^{+})$ and the polar groups of Glu ( $-\text{COOH}$ and ${-\text{NH}}_2$ ), as well as the ions in aqueous TPAB $\text{and}$ TBAB, are significantly stronger and dominate over the hydrophobic interactions involving the nonpolar organic segments of the amino acid and TPAB $/$ TBAB. These findings have wide-ranging applications, from improving pharmaceutical formulations and drug delivery systems to advancing biochemical research on amino acids in complex environments. They also offer valuable insights into solute-solvent interactions, promoting greener, energy-efficient industrial processes and supporting global sustainability efforts. Moreover, by linking these molecular insights to practical applications in crystallization, polymer design, and environmental chemistry, the current study bridges fundamental science with real-world relevance marking a clear advancement over prior literature.