THERMAL CHARACTERIZATION OF A POLYETHYLENEGLYCOL (PEG)-DERIVATIVE INDUCED VESICLE FUSION AS REVEALED BY HIGH-SENSITIVITY DIFFERENTIAL SCANNING CALORIMETRY

Fusion phenomenon of a sonicated large vesicle induced by a derivative of polyethyleneglycol (PEG) was thermodynamically investigated by high sensitivity heating and cooling differential scanning calorimetry (DSC). These studies indicated that the PEG-derivative penetrates into the hydrophobic region of phosphatidylcholine bilayer membrane and leads to a loosely packed structure of the membrane in the liquid crystal state in preference to the gel state. The vesicle incorporating the PEG-derivative induced a fusion with the pure large vesicle, giving rise to an increase in the vesicle size and a decrease in the phase transition enthalpy of the gel-liquid crystal. Based on the calorimetric data, the fusion process was discussed from the viewpoint of the energetics of the PEG-derivative - lipid and the lipid - lipid interactions operating in the lipid membrane of fused vesicles. © 1990.