Rate of permeabilization of giant vesicles by amphiphilic polyacrylates compared to the adsorption of these polymers onto large vesicles and tethered lipid bilayers.
We examined by fluorescence microscopy the permeabilization of giant vesicles by hydrophobically modified polyacrylates (called amphipols). Amphipols trigger permeabilization to FITC-dextran of egg-PC/DPPA vesicles with no breakage of the lipid bilayers. The polyanionic amphipols were passing through bilayers as shown by permeabilization of multilamellar vesicles. Remarkably, the vesicles were not simultaneously permeable but became leaky one after the other. Altogether, our observations suggest a random formation of pores having diameters above a few nanometers. Decreasing pH and increasing ionic strength and polymer concentration were increasing the rate of permeabilization. The rate and efficiency of permeabilization was compared to the rate and density of adsorption of amphipols onto lipid membranes (as estimated by titration calorimetry onto large unilamellar vesicles and neutron reflectivity measurements on tethered bilayers). The polymer adsorption layer is built up in a few minutes. We conclude that the rate-limiting step for permeabilization is not the adsorption from the bulk solution but relates to slow intramembrane reorganizations.
Laboratoire de Physico-chimie des Polymères et des Milieux Dispersés, UPMC and CNRS UMR 7615, ESPCI, 10 rue Vauquelin, F-75005 Paris, France.
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D000179:Acrylates / Q000737:chemistry*; D000327:Adsorption; D008051:Lipid Bilayers / Q000737:chemistry*; D015394:Molecular Structure; D010316:Particle Size; D010539:Permeability; D011108:Polymers / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D022161:Transport Vesicles / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
D000179:Acrylates; D008051:Lipid Bilayers; D011108:Polymers; D014867:Water