Transport Properties Of Aqueous Solutions Research Articles

Transport phenomena and anomalous glass-forming behaviour in α, α-trehalose aqueous solutions

The transport properties of aqueous solutions of the three disaccharides sucrose, maltose and trehalose are investigated by viscosity and NMR measurements. The aim is to clarify the reasons that make trehalose the most effective in protecting organisms from dehydration and freezing. The study indicates that, in comparison with the other disaccharides, trehalose, at high dilution, shows the highest fragility which decreases with the sugar concentration. These results imply a greater ability to conform to biological surfaces and a higher effectiveness in packing and preserving bio-structures.

Hydration and transport properties of aqueous solutions of α-α-trehalose

We report measurements of the sound velocity diffusivity and viscosity of aqueous solutions of α-α-trehalose at temperatures between 20 and 85 °C for volume fractions from 0.041 to 0.705. The ultrasonic data show that the mixing process is not ideal and that the trehalose-water interaction strength, because of the saturation of H-bond sites, decreases with increasing concentration. Photon correlation spectroscopy reveals marked changes in the effective diffusion coefficient in the dilute region over a limited temperature range. These measurements, interpreted in conjunction with viscosity data on the basis of a model by Mooney and Padova, quantify the hydration properties of α-α-trehalose. The dependence on volume fraction and the sensitivity to temperature changes characterize the “fragility” of this disaccharide-water system.

Ion binding in polyelectrolyte solutions. An account for noncoulombic interactions

AbstractCanonical Monte Carlo method is used to study a refined model of polyelectrolyte solution. The discrete charges on a polyion are located periodically along the helix. The ion‐ion and ion‐polyion interactions are described by a solvent‐averaged potential which accounts for the desolvation of ions. The major parameters of the short‐range potential function are Gurney coefficients for the counterion‐counterion (Acc) and the charged group‐counterion interaction (Apc). From simulations, the self‐diffusion coefficient for counterions, D/Do, was calculated. This quantity is rather sensitive to the value of Apc and much less to the choice of the counterion‐counterion coefficient. The refined model is used to analyze a fraction of apparently free counterions, α (≈D/D0), as obtained from recent measurements of transport properties in aqueous solutions of lithium and cesium poly(styrenesulfonate). The values of Gurney parameters, which fit experimental results, are determined: for a good agreement with experimental data an additional repulsive interaction Apc≈3900 J/mol is required for lithium poly(styrenesulfonate) at 5°C. This value is smaller (≈1500 J/mol) for lithium salt at 35°C, and negative, ≈−130 J/mol, for cesium salt of poly(styrenesulfonic) acid.