The effect of hydration stress solutes on the phase behavior of hydrated dipalmitoylphosphatidylcholine

We have investigated the interaction of solutes found to accumulate in biological systems during chilling, dehydration, and salt stress with fully hydrated multilamellar and unilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC). We have focused on a series of mono-, di-, and tri-substituted amines (glycine, 4-hydroxyproline, proline, and betaine) and contrasted the action of these solutes to trehalose, a protective disaccharide. Differential scanning calorimetry studies show that when DPPC is scanned in the presence of increasing concentrations of these solutes (up to 3 M), there is a moderate increase in the pre-transition temperature (1-6°C) with a smaller increase (1-2°C) in the main transition temperature of hydrated multilamellar vesicles of DPPC. Other calorimetric parameters (ΔH, ΔT _{1 2}, Cp_max) determined for the pre-transition and main transition were similar independent of the solute. In each case, the main phase transition was broadened with increasing solute while the transition enthalpy was not significantly affected.