Molecular dynamics simulations of the interactions of DMSO, mono- and polyhydroxylated cryosolvents with a hydrated phospholipid bilayer.

Molecular dynamics (MD) simulations have been used to investigate the interactions of a variety of hydroxylated cryosolvents (glycerol, propylene glycol and ethylene glycol), methanol and dimethyl sulfoxide (DMSO) in aqueous solution with a 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) bilayer in its fluid phase at 323K. Each cryosolvent induced lateral expansion of the membrane leading to thinning of the bilayer and resulting in disordering of the lipid hydrocarbon chains. Propylene glycol and DMSO were observed to exhibit a greater disordering effect on the structure of the membrane than the other three alcohols. Closer examination exposed a number of effects on the lipid bilayer as a function of the molecular size and hydrogen bonding capacity of the cryosolvents. Analyses of hydrogen bonds revealed that increased concentrations of the polyhydroxylated cryosolvents induced the formation of a cross-linked cryosolvent layer across the surface of the membrane bilayer. This effect was most pronounced for glycerol at sufficiently high concentrations, which displayed a comparatively enhanced capacity to induce cross-linking of lipid headgroups resulting in the formation of extensive hydrogen bonding bridges and the promotion of a dense cryosolvent layer across the phospholipid bilayer.