Partial molar adiabatic compressibilities and viscosities of some amino acids in aqueous glycerol solutions at 298.15 K

Abstract

Apparent molar adiabatic compressibilities, s,₂,, and viscosities, η, of glycine, DL-⍺-alanine, L-valine, L-leucine and L-phenylalanine have been determined in water and in mixed aqueous solutions of glycerol (0.5, 1.0, 2.0, 3.5, and 5.0 mB molality of glycerol in water / mol kg⁻¹) at 298.15 K. These data have been used to calculate partial molar adiabatic compressibilities at infinite dilution, and viscosity B-coefficients, and their corresponding transfer functions. The positive partial molar adiabatic compressibilities of transfer at infinite dilution, tr , have been observed for the studied amino acids (except at lower concentration up to ≈ 0.6 mB in some cases), and their magnitude increases with increase in concentration of glycerol. B-coefficient of transfer, ΔtrB, values are positive for these amino acids, which after passing through maxima ≈3.5 mB decrease at higher concentration of glycerol. The activation energy for viscous flow in aqueous and mixed aqueous glycerol solutions has been calculated from B-coefficient and partial molar volume data. Hydration numbers, interaction coefficients and side chain contributions have also been calculated. These results have been discussed in terms of solute-cosolute interactions, and an attempt has also been made to correlate these parameters with the stability of protein in aqueous glycerol solutions.