Molecular Dynamics Study of Effects of Temperature and Concentration on Hydrogen-Bond Abilities of Ethylene Glycol and Glycerol: Implications for Cryopreservation

Abstract

The state of intracellular water is important in all phases of cryopreservation. Intracellular water can be transported out of the cell, transferred into its solid phase, or blocked by cryoprotectants and proteins in the cytoplasm. The purpose of the present study is to determine the amount of hydrogen-bonded water in aqueous ethylene glycol and glycerol solutions. The effects of temperature and concentration on the density and the hydrogen bonding characteristics of the solution are evaluated quantitatively in this study. To achieve these aims, a series of molecular dynamics simulations of ethylene glycol/water and glycerol/water mixtures of molalities ranging from 1 to 5 m are conducted at 1 atm and at 273, 285, and 298 K, respectively. The simulation results show that temperature and concentration have variable effects on solution density. The proportion of the hydrogen-bonded water by solute molecules increases with rising molality. The ability of the solute molecules to hydrogen bond with water molecules weakens as the solution becomes more concentrated. Moreover, it turns out that the solution concentration can influence the hydrogen bonding characteristics more greatly than the temperature. The glycerol molecule should be a stronger "water blocker" than the ethylene glycol molecule corresponding to the same conditions. These findings provide insight into the cryoprotective mechanisms of ethylene glycol and glycerol in aqueous solutions, which will confer benefits on the cryopreservation.

Molecular Dynamics Investigation of the Effects of Concentration on Hydrogen Bonding in Aqueous Solutions of Methanol, Ethylene Glycol and Glycerol

“…The results presented in Figure 5 show the similar findings with our previously study 22 that N bw /N s decreases with increasing the concentration. The results for GLY shows sharper change than the other two curves due to the fact that the GLY molecule is a trihydric alcohol, which results in more hydrogen bonded water molecules in the solution.…”

“…MET/EG/GLY and water are mixed in varying combinations ranging from 1-90 mol %. The simulated densities of dilute solutions of EG and GLY were shown in our previous investigations, 22 which presented the simulated density of mixture in well agreement with the experiment. Here the simulated densities of MET solutions are tabulated in Table 1 Information.…”

“…The comparison proves that the hydroxyl group of EG molecule has greater ability to Hbond water molecules than GLY. As stated in our previous paper, 22 the difference between the practical and ideal relationships is due to the intra-and intermolecular interactions of the solute molecules in the MET, EG and GLY aqueous solutions.…”

“…Afterthat, H-bonding characteristics of cryoprotective media (glycerol/sodium chloride/water mixtures) were investigated in depth. 21 Weng and his colleagues 22 quantitatively investigated the relationship between hydrogen bonded water and the concentration of EG and GLY aqueous solutions, and we 23 also used Perkin-Elmer Diamond Differential Scanning Calorimetry (DSC) to verify the simulation findings.…”

“…The W-W H-bonds provide the potential for the formation of intracellular ice crystallization, while the W-S H-bonds can suppress the ice crystallization. In our previous study, 22 we defined one water molecule with one or more W-S H-bonds as "bound water" and evaluated the ability of the alcohol molecules to form H-bonds with water molecules by two criteria: the number of "bound water" by one solute molecule N bw /N s and the mass fraction of "bound water" out of the total water W bw /W w . Here, a further investigation on MET, EG and GLY solutions in a broader range of concentration is made as shown in Figure 5.…”