An Integrated Quasi-Elastic Light-Scattering, Pulse-Gradient-Spin−Echo Study on the Transport Properties of α,α-Trehalose, Sucrose, and Maltose Deuterium Oxide Solutions

NMR study on the interaction of trehalose with lactose and its effect on the hydrogen bond interaction in lactose

Trehalose, a well-known stress-protector of biomolecules, has been investigated for its effect on the mobility, hydration and hydrogen bond interaction of lactose using diffusion-ordered NMR spectroscopy and NMR of hydroxy protons. In ternary mixtures of trehalose, lactose and water, the two sugars have the same rate of diffusion. The chemical shifts, temperature coefficients, vicinal coupling constants and ROE of the hydroxy protons in trehalose, lactose and sucrose were measured for the disaccharides alone in water/acetone-d₆ solutions as well as in mixtures. The data indicated that addition of trehalose did not change significantly the strength of the hydrogen bond interaction between GlcOH3 and GalO5' in lactose. Small upfield shifts were however measured for all hydroxy protons when the sugar concentration was increased. The chemical shift of the GlcOH3 signal in lactose showed less change, attributed to the spatial proximity to GalO5'. Chemical exchange between hydroxy protons of lactose and trehalose was observed in the ROESY NMR spectra. Similar effects were observed with sucrose indicating no specific effect of trehalose at the concentrations investigated (73 to 763 mg/mL) and suggesting that it is the concentration of hydroxy groups more than the type of sugars which is guiding intermolecular interactions.

Comparing simulated and experimental translation and rotation constants: range of validity for viscosity scaling

Proper simulation of dynamic properties, including molecular diffusion, is an important goal of empirical force fields. However, the widely used TIP3P water model does not reproduce the experimental viscosity of water. Consequently, scaling of simulated diffusion constants of solutes in aqueous solutions is required to effectively compare them with experiment. It is proposed that scaling by the ratio of viscosities of model and real water is appropriate in the regime where the concentration dependence of simulated and experimental solution viscosities is parallel. With this ansatz, viscosity scaling can be carried out for glucose and trehalose up to 20 wt % for simulations carried out with the CHARMM additive carbohydrate force field C35 and TIP3P water; above this value, the concentration dependence of simulated viscosities lags that of experiment, and scaling is not advised. Scaled translational diffusion constants for glucose and the disaccharides trehalose, maltose, and melibiose at low concentration agree nearly quantitatively with experiment, as do NMR (13)C T(1)'s for glucose, trehalose, and maltose; these results support the use of C35 for simulations of sugar transport properties at low concentration. At high concentrations the scaled diffusion constants for glucose and trehalose underestimate and overestimate experiment, respectively. Hydrodynamic bead model calculations indicate a hydration level of approximately 1 water/hydroxyl for glucose. Patterns for the disaccharides are more complicated, though trehalose binds 0.5 to 1 more water than does maltose depending on the analysis.

Molecular dynamics simulations of trehalose as a ‘dynamic reducer’ for solvent water molecules in the hydration shell

Systematic computational work for a series of 13 disaccharides was performed to provide an atomic-level insight of unique biochemical role of the alpha,alpha-(1-->1)-linked glucopyranoside dimer over the other glycosidically linked sugars. Superior osmotic and cryoprotective abilities of trehalose were explained on the basis of conformational and hydration characteristics of the trehalose molecule. Analyses of the hydration number and radial distribution function of solvent water molecules showed that there was very little hydration adjacent to the glycosidic oxygen of trehalose and that the dynamic conformation of trehalose was less flexible than any of the other sugars due to this anisotropic hydration. The remarkable conformational rigidity that allowed trehalose to act as a sugar template was required for stable interactions with hydrogen-bonded water molecules. Trehalose made an average of 2.8 long-lived hydrogen bonds per each MD step, which was much larger than the average of 2.1 for the other sugars. The stable hydrogen-bond network is derived from the formation of long-lived water bridges at the expense of decreasing the dynamics of the water molecules. Evidence for this dynamic reduction of water by trehalose was also established based on each of the lowest translational diffusion coefficients and the lowest intermolecular coulombic energy of the water molecules around trehalose. Overall results indicate that trehalose functions as a 'dynamic reducer' for solvent water molecules based on its anisotropic hydration and conformational rigidity, suggesting that macroscopic solvent properties could be modulated by changes in the type of glycosidic linkages in sugar molecules.