Modulation of hydration characteristics of carbohydrates in aqueous medium of γ-amino butyric acid via volumetric, rheological and time-domain longitudinal NMR relaxation studies

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, V 2 ° and Jones-Dole viscosity B -coefficients of monosaccharides and their derivatives, polyols and disaccharides were determined in molality, m B 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, Δ tr V 2 ° and change in viscosity B -coefficient, Δ B 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 (∂  V 2 ° /∂  T ) P , second-order derivatives (∂ 2 V 2 ° /∂  T 2 ) 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 ( 1 H) NMR relaxation rates ( R 1 ) were also obtained for carbohydrates in different γ-ABA solutions made in 9:1 ( w / w ) (H 2 O + D 2 O) 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.