title: Polymer-Induced Swelling of Solid-Supported Lipid Membranes.
abstract: In this paper, we study the interaction of charged polymers with solid-supported 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes by in-situ neutron reflectivity. We observe an enormous swelling of the oligolamellar lipid bilayer stacks after incubation in solutions of poly(allylamine hydrochloride) (PAH) in D₂O. The positively charged polyelectrolyte molecules interact with the lipid bilayers and induce a drastic increase in their d-spacing by a factor of ~4. Temperature, time, and pH influence the swollen interfacial lipid linings. From our study, we conclude that electrostatic interactions introduced by the adsorbed PAH are the main cause for the drastic swelling of the lipid coatings. The DMPC membrane stacks do not detach from their solid support at T > Tm. Steric interactions, also introduced by the PAH molecules, are held responsible for the stabilizing effect. We believe that this novel system offers great potential for fundamental studies of biomembrane properties, keeping the membrane's natural fluidity and freedom, decoupled from a solid support at physiological conditions.
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, Berlin 14109, Germany. marcus.trapp@helmholtz-berlin.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Kreuzer
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, Berlin 14109, Germany. marcus.trapp@helmholtz-berlin.de.
authors.forename: Marcus
authors.initials: M
authors.lastname: Trapp
authors.affiliation: Angewandte Physikalische Chemie, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 253, Heidelberg 69120, Germany. reiner.dahint@pci.uni-heidelberg.de.
authors.forename: Reiner
authors.initials: R
authors.lastname: Dahint
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, Berlin 14109, Germany. steitz@helmholtz-berlin.de.
authors.forename: Roland
authors.initials: R
authors.lastname: Steitz
keywords: lipid; membranes; neutron reflectivity; polymer