Molecular Dynamics of Carbohydrate Aqueous Solutions. Dielectric Relaxation as a Function of Glucose and Fructose Concentration

Abstract

At some solute concentrations c between 1 and 5.4 mol/L, the complex (electric) permittivity of aqueous solutions of D-glucose and D-fructose has been determined as a function of frequency υ between 300 kHz and 40 GHz. The permittivity spectrum of the 5.4 mol/L D-fructose solution has been measured at six temperatures between 10 and 35 °C, and the other spectra have been taken at 25 °C. All dielectric spectra revealed one dispersion/dielectric loss region, which indicated a rather homogeneous relaxation of the solute and solvent dipole moments. Analytically, the measured spectra were represented by the Cole-Cole relaxation spectral function, which corresponds with a continuous, symmetrically bell shaped relaxation time distribution. The parameters of the spectral function are discussed to show that the monosaccharides exhibit unusual hydration properties. Particularly, when treated in terms of a wait-and-switch model of dipole reorientation, the principal dielectric relaxation time is indicative of the extraordinary hydration behavior of the saccharides. It is suggested that this behavior reflects the compatibility of the ring molecule's -OH group topology with the water structure.

Impedance spectroscopy of solutions at physiological glucose concentrations

“…Thus, we can claim that variations in glucose concentration even at low values such as physiological ones should directly affect the dielectric properties of a solution, independently from other mechanisms that may be induced by glucose variations. On the other hand, it is confirmed that the impedance variations due to variations in glucose are certainly more evident at low frequencies, and this may partially explain why they were not observed in the studies [22,23] where frequencies over 1 MHz were considered.…”

“…In [2] it was claimed that these effects are entirely responsible for the impedance variation of blood and underlying tissues, since glucose variations do not directly affect the dielectric properties of the investigated medium in the MHz band, as also stressed in other studies from the same research group [20,21]. In fact, some references were provided to other studies where the effect of variations in glucose concentration was studied in water [22,23]. In [23] it was shown that at glucose concentrations lower than 1 g/cc the dielectric properties of the glucose-water solution are not different from those of pure water.…”

Lipid composition and molecular interactions change with depth in the avian stratum corneum to regulate cutaneous water loss

“…As a result, the hydrogen bonds between water molecules in the primary solvation shell and water molecules outside the shell are disrupted, thus weakening hydrogen bonding structure of the water just beyond the solvation shell (Gallina et al, 2006;Paolantoni et al, 2007). However, despite the weakening of hydrogen bonds in water outside the solvation shell, the strong hydrogen bonding between glucose moieties of cerebrosides and water molecules in the first solvation shell increases the viscosity of the water and potentially slows the rate of water permeation through the SC (Fuchs and Kaatze, 2001;Comesaña et al, 2003).…”

Molecular Dynamics and Conformational Kinetics of Mono‐ and Disaccharides in Aqueous Solution

“…[29,32] At n 3 GHz the wavelength of the electromagnetic field within the sample was sufficiently large to allow for quasi-static approaches. Therefore, in this frequency range, input impedance measurements have been performed using specimen cells of the cut-off variety.…”

“…The temperature of the specimen cells was controlled to be within 0.05 K and it was measured with an error of less than 0.02 K. [29,32] Auxiliary Measurements: The density 1 of the carbohydrate solutions has been measured with a pycnometers (20 mL, 25 mL, D1/ 1 = 0.002) that had been calibrated against distilled and degassed water. The shear viscosity h s of the samples has been determined to within 2 % using a falling ball viscosimeter and a set of Ubbelohde capillary viscosimeters.…”