Liquid-liquid separation of aqueous solutions: A molecular dynamics study

Abstract

In the liquid-liquid phase transition scenario, supercooled water separates into the high density liquid (HDL) and low density liquid (LDL) phases at temperatures lower than the second critical point. We investigate the effects of hydrophilic and hydrophobic solutes on the liquid-liquid phase transition using molecular dynamics simulations. It is found that a supercooled aqueous NaCl solution separates into solute-rich HDL and solute-poor LDL parts at low pressures. By contrast, a supercooled aqueous Ne solution separates into solute-rich LDL and solute-poor HDL parts at high pressures. Both the solutes increase the high temperature limit of the liquid-liquid separation. The degree of separation is quantified using the local density of solute particles to determine the liquid-liquid coexistence region in the pressure-temperature phase diagram. The effects of NaCl and Ne on the phase diagram of supercooled water are explained in terms of preferential solvation of ions in HDL and that of small hydrophobic particles in LDL, respectively.

Formation of synthetic RNA protein granules using engineered phage-coat-protein -RNA complexes

“…However, the slow rate (i.e. O(10 3 sec)) by which these events are occurring is inconsistent with expectations from an LLPS molecular dynamics (MD) simulation published recently (Yagasaki et al, 2019). Therefore, the slow non-correlated exchange rate, the association of bursts with exchange events of slncRNA-CP complexes (rather than just CPs), and the filament-like structure appearing in the in vitro images suggest that the synthetic RNP granules seem to exhibit gel or glass-like properties, rather than classic liquid or solid-like characteristics.…”

Direct observation of reversible liquid–liquid transition in a trehalose aqueous solution

“…When the LDS was compressed at the same temperature, the volume started to decrease rapidly at ∼0.14 GPa, and then, the LDS transformed to the original HDS. In the case of the polyamorphic transition of the aqueous solution, it is suggested that low-density and high-density states coexist in a pressure region between the beginning and end of the polyamorphic transition ( 14 , 37 , 38 ). Now, the HDS-to-LDS transition pressure, P HtoL , and the LDS-to-HDS transition pressure, P LtoH , are defined as the middle pressure between onset and offset transition pressures for each polyamorphic transition.…”

Experimental observation of nanophase segregation in aqueous salt solutions around the predicted liquid–liquid transition in water

“…14 The temperature of a liquid-liquid phase transition in aqueous NaCl solutions is predicted by molecular dynamics studies to be higher than that for pure water. 50,51 We do not observe any change in the OD stretching mode indicating a change to a more tetrahedral water structure which would be definitive evidence of a water liquidliquid transition.…”