The structure of water determined by microwave dielectric study on water mixtures with glucose, polysaccharides, and L-ascorbic acid

Abstract

Dielectric relaxation measurements over an extremely wide frequency region from 1 MHz to 20 GHz were performed on water mixtures with glucose, polysaccharides, and L-xylo ascorbic acid by the use of time domain refiectometry. For mixtures of polysaccharides bigger than maltotriose, two relaxation peaks were definitely observed. The high frequency relaxation is the water relaxation and the low frequency one is due to orientation of polysaccharide molecules. In the case of glucose, only one relaxation peak could be observed. It is shown that a hexagonal cluster in the lattice of ice can be replaced easily by the glucose molecule, where the lattice is distorted slightly, but stabilized by several hydrogen bonds between the glucose molecule and the lattice. Although the cluster can be replaced by the L-ascorbic acid molecule too, the lattice cannot be kept stable. Its water mixture shows two relaxation peaks clearly. It is suggested that water has a structure of the distorted lattice of ice. Fluctuation of the lattice breaks the hydrogen bonds and the lattice is decomposed. Orientation of the water molecules released gives rise to the relaxation concerned.

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.…”

“…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. However, a more recent study contradicts these findings.…”

Dielectric relaxation of aqueous solutions of maltotriose

“…On the other hand, β-modes for both solutions have similar dependences below T g . Simple carbohydrate solutions show a relatively large peak in the dielectric relaxation curve derived from the large dipole moment of the hydroxy group [6][7][8][9][10][11]. As the water content is higher, the dielectric strengths for α-mode and β-mode become larger, indicating that the water molecules are contributed to these relaxation modes.…”

“…However, the investigations for the molecular motions have not been so developed compared with other biopolymers, such as proteins, because of their less ordered structures, except fundamental saccharides, such as glucose, sucrose and so on [6][7][8][9][10][11]. Most of polysaccharides exist in biological systems, where the systems contain abundant water molecules as a solvent.…”