Binding of Cholera Toxin B-Subunit to a Ganglioside GM1Functionalized PEG-Tethered Lipid Membrane

We report neutron reflectometry (NR) studies of polyethylene glycol (PEG)tethered model lipid membranes at the solid-liquid interface and of cholera toxin's B-subunit (CTxB) binding to tethered membranes containing ganglioside GM1 receptors. First, tethered polymer brushes were formed by grafting silane-functionalized PEG lipopolymers to quartz from solution. Subsequent deposition of lipids by Langmuir-Blodgett/LangmuirSchaefer (LB/LS) resulted in a tethered bilayer structure separated from the solid support by a hydrated PEG layer. NR revealed that the tethers formed a highly hydrated polymer brush, uniformly separating the bilayer from the underlying solid substrate. Further, the lipid bilayer did not significantly perturb the brush's conformation relative to a free brush. Biological functionality of the tethered bilayers was verified by interacting CTxB, with ganglioside GM1 receptors incorporated into the bilayer. The surface coverage of CTxB bound to the lipid membrane,theta(CTB)= 0.58 +/- 0.08, was consistent with the coverage predicted for random sequential absorption, and toxin binding did not impact the membrane conformation.