Effect of Gadolinium(III) Ions on the Phase Behaviour of Dimyristoylphosphatidyl Serine Multilamellar Liposomes

The effects of low concentrations of Gd³⁺ on dimyristoylphosphatidyl serine (DMPS) multilamellar liposomes were studied by differential scanning calorimetry (DSC). At low ionic strength merely a shifting upscale and a broadening of the main transition peak were observed. At high ionic strength, Gd³⁺ provoked the formation of a few clearly-discernible high-temperature components. Increase of the Gd level affected the relative intensities of these components, whereas the corresponding midpoints and half-widths remained unchanged. At the same time, in the presence of about 20 mol% dimyristoylphosphatidyl choline in the mixture with DMPS, similar secondary peaks appeared, but their positions were markedly shifted, to extents dependent on the Gd concentration. Interpretation of the data in terms of two-dimensional crystal structures is suggested. This revised version was published online in July 2006 with corrections to the Cover Date.