title: Modulation of substrate-membrane interactions by linear poly(2-methyl-2-oxazoline) spacers revealed by X-ray reflectivity and ellipsometry.
abstract: Hydrated polymer interlayers between planar lipid membranes and solid substrates provide a water reservoir and thus maintain a finite membrane-substrate distance. Linear polymer spacers attached to lipid head groups (lipopolymer tethers) can be used as a defined model of oligo- and polysaccharides covalently anchored on cell surfaces (glycocalyx). They can offer a unique advantage over membranes physisorbed on polymer films (called polymer-cushioned membranes), owing to their ability to control both the length and density of polymer chains. In this study, a lipopolymer tether composed of a stable ether lipid moiety and a hydrophilic poly(2-methyl-2-oxazoline) spacer with a length of 60 monomer units is used to fabricate supported membranes by the successive deposition of proximal (lower) and distal (upper) leaflets. Using specular X-ray reflectivity and ellipsometry, we systematically investigate how the lateral density of polymer chains influences the membrane-substrate interactions. The combination of two types of reflectivity techniques under various conditions enables the calculation of quantitative force-distance relationships. Such artificial membrane systems can be considered as a half-model of cell-cell contacts mediated via the glycocalyx, which reveals the influence of polymer chain density on the interplay of interfacial forces at biological interfaces.
authors.affiliation: Biophysical Chemistry Laboratory II, Institute of Physical Chemistry and BIOQUANT, University of Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Seitz
authors.forename: Michael D
authors.initials: MD
authors.lastname: Reif
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Konovalov
authors.forename: Rainer
authors.initials: R
authors.lastname: Jordan
authors.forename: Motomu
authors.initials: M
authors.lastname: Tanaka
mesh_terms: D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry; D019276:Glycocalyx / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry; D011073:Polyamines; D012031:Refractometry; D014965:X-Rays
chemical_list: D008051:Lipid Bilayers; D011073:Polyamines; C117403:poly(2-methyl-2-oxazoline); D002686:Chitin