LAUSR

Abstract Carbohydrates such as saccharides and their derivatives are engaged in various biological processes such as in transportation and transmission of genetic material, enzymatic processes, and regulation of metabolism. γ-Amino butyric acid (γ-ABA) is a non-protein amino acid and acts as an inhibitory neurotransmitter in the mammalian cerebral cortex. Volumetric, rheological and spectroscopic investigations are helpful to elucidate the molecular interactions occurring between carbohydrates and γ-ABA in aqueous solution. Therefore, the standard state partial molar volumes, V2° and Jones-Dole viscosity B-coefficients of monosaccharides and their derivatives, polyols and disaccharides were determined in molality, mB range (0.05–0.50) mol·kg− 1 aqueous solutions of γ-ABA from the precise density and viscosity measurements at temperature range T = (288.15–318.15) K. These data were used to obtain the corresponding volumes of transfer, ΔtrV2° and change in viscosity B-coefficient, ΔB for carbohydrates from water to aqueous solutions of γ-ABA. The taste quality of studied solutes (carbohydrates) has been appraised in the presence of γ-ABA from apparent massic volumes. The volumetric and viscometric interaction coefficients were calculated from the McMillan-Mayer theory of solutions. The expansion coefficients (∂ V2°/∂ T)P, second-order derivatives (∂2V2°/∂ T2)P and dB/dT coefficients were also determined to study the influence of temperature. These quantities have been explained in terms of various interactions occurring in the ternary system on the basis of co-sphere overlap model suggested by Gurney (1953). Proton (1H) NMR relaxation rates (R1) were also obtained for carbohydrates in different γ-ABA solutions made in 9:1 (w/w) (H2O + D2O) solvent, at T = 300 K. The results have been compared with our previously reported (Banipal et al., 2015, 2016) studies carried out in L-glycine. The stereochemical effects of studied solutes on hydration controlled by their domineering conformations have also been discussed.