LAUSR

Abstract Drug-amino acid interactions have been investigated in aqueous media from the experimentally measured data of densities, ρ, ultrasonic speeds, u and viscosities, η of glycine, l-alanine, l-valine and l-isoleucine in water and in aqueous-isoniazid (1% and 2% isoniazid in water, w/w) solvents at temperatures (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and at atmospheric pressure. The ρ and u data have been used to calculate the apparent molar volume, Vφ, limiting apparent molar volume, Vϕ°, apparent molar compressibility, Ks,ϕ, limiting apparent molar compressibility, Ks,ϕ°, transfer volume, Vϕ,tr°, and transfer compressibility, Ks,ϕ,tr° and hydration number, nH. The viscosity data have been used to determine Falkenhagen Coefficient, A, Jones-Dole coefficient, B, free energy of activation of viscous flow per mole of solvent, Δμ1°# and per mole of solute, Δμ2°#. These parameters have been discussed in terms of solute-solute and solute-solvent interactions prevailing in these solutions. A detailed insight into the structure making/breaking ability of the amino acids in these solutions has been retrieved through the close perusal of all these parameters. In addition, the values of Vϕ°, Ks, ϕ°, B and Δμ2°# have been split into groups' contributions of the amino acids. Entropies, ΔS°# and enthalpies, ΔH°#of activation of viscous flow for amino acids in aqueous isoniazid solutions have been used to interpret interactions between the ions of amino acids and isoniazid.