Membrane insertion of sliding anchored polymers

We have studied the insertion into lipid bilayers of Sliding Anchored Polymers (SAPs), a new class of macromolecules based on topological complexes between end-capped polyethylene glycol (PEG) polymers and mono-cholesteryl cyclodextrins (CD). By using Infra Red Reflection Absorption Spectroscopy (IRRAS) we demonstrate that these new sliding polymer complexes anchor well in phospholipid model membranes self-assembled from DPPC. The in-plane organization is characterized by Brewster Angle Microscopy (BAM) at the air-water interface and by Atomic Force Microscopy (AFM) for lipid monolayers and for lipid bilayers deposited on mica. Demixing between SAPs and the phospholipids is observed even at low surface pressures. Using neutron reflectivity, we show that for sufficiently high polymer densities the SAPs inserted into lipid monolayers and lipid bilayers form polymer brushes, consistent with theoretical predictions for polymers with a sliding anchor.