Effects of oxyethylated glycerol cryoprotectants on phase transitions of DPPC model membranes

Abstract

Aim. To determine the effect of the oxyethylated glycerol cryoprotectants (OEG n) with polymerization degrees n = 5, 25, 30 on the phase states and phase transitions of dipalmitoylphosphatidylcholine (DPPC)-based model membranes. Methods. Differential scanning calorimetry. Results. Model lipid membranes on water/OEG n and water/glycerol subphases with varying cryoprotectant concentrations from 0 to ~ 100% w/w were studied. A significant raise in the pre-transition and main phase transition temperatures with increasing OEG n concentration was noted whereas the membrane melting peak persist to 100% w/w OEG n. n A sharp increase in the melting enthalpy was observed for OEG n = 5. Conclusions. The solvating ability n = 5 the subphase in DPPC membranes decreases in the order water > glycerol > OEG n = 5 OEG n = 25 OEG n =30, which correlates with the relative number of groups effectively contributing to the solvation process.