A Heteronuclear NMR Study of Aqueous Lithium Salt Solutions of l-Alanine: Revealing Solute Hydrophobic Association through the NMR B ' Coefficient.

In the present study, a set of heteronuclear NMR approaches has been adopted to investigate the solution behavior of a small hydrophobic solute l-alanine in the presence of lithium (Li) salts. The presence of salts plays a major role in determining the structure and solvation of biomolecules. It therefore evokes interest to understand the effect of Li salts on amino acids (alanine), the building block of biomolecules. The ionic solute dynamics in the present case has been probed using 1 H, 7 Li, and 13 C nuclei available in the aqueous Li salt solution of l-alanine. Nuclear longitudinal spin relaxation of alanine protons was examined at a variable concentration range of three lithium salts, i.e., LiCl, Li 2 SO 4 and LiClO 4 , to introduce the NMR B ' coefficient for each salt defining ionic solute/solvent interaction in the solution. Analysis of the active relaxation mechanism of 7 Li spin-lattice relaxation further revealed the presence of alanine in the solvation shell of Li ion depending on the anionic counterpart.