Localization of transmembrane multiblock amphiphilic molecules in phase-separated vesicles.

A series of triblock amphiphilic molecules bearing hydrophilic PEG chains at both ends of the long aromatic hydrophobic moieties were obtained serendipitously. The molecules involve linearly connected diarylethyne and diarylbutadiyne units, which show characteristic emissions upon excitation by UV light. These emissions showed red-shifts upon an increase in the solvent polarity, where the shifts are larger for the molecules with longer aromatic moieties. The distribution of these molecules in phase-separated membranes consisting of DOPC/DPPC/cholesterol was studied by fluorescence microscopy. It was found that most compounds, except for that with the longest hydrophobic unit, were selectively distributed in the Ld phase consisting mainly of DOPC. Interestingly, some of them were suggested to encourage delocalization of cholesterol in both the Lo and Ld phases.