Characterization of the Glass Transition of Water Predicted by Molecular Dynamics Simulations Using Nonpolarizable Intermolecular Potentials

Abstract

Molecular dynamics simulations allow detailed study of the experimentally inaccessible liquid state of supercooled water below its homogeneous nucleation temperature and the characterization of the glass transition. Simple, nonpolarizable intermolecular potentials are commonly used in classical molecular dynamics simulations of water and aqueous systems due to their lower computational cost and their ability to reproduce a wide range of properties. Because the quality of these predictions varies between the potentials, the predicted glass transition of water is likely to be influenced by the choice of potential. We have thus conducted an extensive comparative investigation of various three-, four-, five-, and six-point water potentials in both the NPT and NVT ensembles. The T(g) predicted from NPT simulations is strongly correlated with the temperature of minimum density, whereas the maximum in the heat capacity plot corresponds to the minimum in the thermal expansion coefficient. In the NVT ensemble, these points are instead related to the maximum in the internal pressure and the minimum of its derivative, respectively. A detailed analysis of the hydrogen-bonding properties at the glass transition reveals that the extent of hydrogen-bonds lost upon the melting of the glassy state is related to the height of the heat capacity peak and varies between water potentials.

Current issues in plant cryopreservation and importance for ex situ conservation of threatened Australian native species

“…Sufficient dehydration and cooling during cryo-storage ensures that the temperature drops rapidly below the glass transition temperature (T g ), resulting in the formation of an amorphous 'glassy' state (Shamblin et al 1999;Walters 2015). The stability of this glassy state is related to the strength of the hydrogen-bonding network in water (Kreck and Mancera 2014). The advantages of the formation of this glassy state are that it (i) prevents cellular collapse; (ii) precludes chemical reactions requiring diffusion, ensuring stability during the storage period; and (iii) allows chaotropic solutes to be trapped by an amorphous glass which prevents them from becoming concentrated (Burke 1986;Moelbert et al 2004).…”

Molecular Mechanism of the Synergistic Effects of Vitrification Solutions on the Stability of Phospholipid Bilayers

“…Commonly used CPAs such as dimethyl sulfoxide (DMSO), polyols, and sugars reduce the damage to cells during cryopreservation by reducing colligatively the melting temperature of water and promoting the formation of its glassy state (vitrification), avoiding the deleterious formation of ice (6)(7)(8)(9)(10)(11)(12). Unfortunately, a number of these species are toxic, partly because they can damage cell membranes at sufficiently high concentration (8).…”