Membrane sealing copolymer surfactant poloxamer 188 inserts into lipid monolayers at reduced surface pressures
Experiments were conducted in a Langmuir trough with Wilhelmy plate coupled to a fluorescence microscope. Monolayers of either dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidyl-glycerol (DPPG), mimicking the outer cell membrane leaflet, were spread and compressed to 30 mN/m surface pressure, then step-wise relaxed after P188 was injected into the subphase. In pretreatment experiments the monolayer was spread at 0 mN/m and P188 added immediately. then comparessed. At 30°C P188 inserts into both DPPC and DPPG monolayers at surface pressures below 23 mN/m and leaves it once the surface is re-compressed above this value. Similar insertion results for both lipid headgroups suggest the absence of any electrostatic influence. The insertion at surface pressures below that of natural cell membranes (ca. 30 mN/m) indicates that P188 might interact with structurally compromised membranes only, but not with intact cell membranes.
Maskarinec, SA; Hannig, J; Lee, KYC; Lee, RC
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