![]() ![]() A recurring hypothesis in experimental and computational studies is that cryoprotectants act by modifying water structure. The temperature behaviour of glycerol has thought to be due to the existence of an extended hydrogen-bond network. As it is known, as cryoprotectant glycerol acts by stabilizing macromolecules, cells and tissues under cooling to subzero temperatures, along with suppressing the formation of ice. Particular interest there is in studying the action of glycerol on the structure of water. In this regard, the dynamics of complex systems such as hydrogen-bonding liquids and their mixtures is nowadays one of the most active areas of research. ĭue to the key role of water in biological systems, a better comprehension of water structuring is desirable. In addition, a structural polymorphism of water (quasi-crystalline structures) has been suggested also in those salt solutions, where water structuring is expected, and in the solute-free zone (hundreds of μm in width and stable for days once formed) that water forms in proximity of various hydrophilic surfaces. Moreover, a Debye-like slow relaxation was observed in water, associated to structural and/or dynamical inhomogeneity on length scale of the order of 100 μm, as the chainlike structures with a polymer-like dynamics proposed by Huang and co-workers. Several experimental results have supported the existence of two distinguishable structures in liquid water. It has been suggested that liquid water consists of two kind of micro-domains of rapidly exchanging polymorphism in dynamical equilibrium : one form, namely the low-density water (LDW), with intermolecular hydrogen bonds like that of ordinary hexagonal ice, and the other one, namely the high-density water (HDW), with compact bonding similar to ice II. Even if the molecular movements in water require constant breaking and reorganization of individual hydrogen bonds on a picosecond time scale, at any instant, the degree of hydrogen bonding is very high showing a dynamic equilibrium among changing percentages of assemblages of different oligomers and polymer species (clusters), whose structure is dependent on temperature, pressure and composition. The extensive three-dimensional hydrogen bond network of H 2O molecules plays a fundamental role in the behaviour of water. The structure of hydration shells determines the biological functions of a protein and influences interaction with other protein or substrates. Water is not just a solvent but it actively engages and interacts with biomolecules at nanoscale level in complex and essential ways for establishment and maintenance of life. The role of water and its anomalous properties in the chemistry of life have intrigued generations of scientists and the behaviour of water constitutes an open task up to now. DL results have shown a correlation with LDW clusters size as determined by other researchers on the basis of neutron diffraction experiments and computational modelling, as reported in Literature. ![]() Spectral and temporal characteristics of DL decays give information on the two components of the mixture, by evidencing the contribution of water at glycerol concentrations close to the values used in cryopreservation. Supported by the results obtained with other aqueous solutions, this paper deals with the possibility of using the ultra-weak delayed luminescence (DL) to investigate water structuring in a mixture with glycerol, characterized only by hydrogen bonds between the various molecules. Many properties of water have been related to the interplay between two distinct and interconverting structural species, namely the low-density water (LDW) and the high-density water (HDW). The crucial role of water in the engine of life have encouraged many researchers in studying, both theoretically and experimentally, the possible “structure” of water. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |