| Abstract
| - We describe a technique of anchoring ultrathin (50−250 nm) layers of the extracellular matrixpolysaccharide hyaluronic acid (HA) on solid supported fluid lipid bilayers through a recombinant HA-binding protein (p32) which is coupled to lipid molecules by reversible histidine−chelator bonds. A noveltechnique, the dual wavelength reflection interference contrast microscopy (DW-RICM), was applied tomeasure the local absolute thickness of the soft polymer cushions by measuring the height of the colloidalbeads hovering over the surface. By analysis of the mean-square out-of-plane fluctuations of the beads,the surface elasticity and friction of the HA films can be measured as a function of the film thickness. Thetechnique is applied to study the influence of excess salt and the cross-linkers on the film thickness andviscoelastic parameters of membrane coupled HA layer. The mean-square displacement of the lateraldiffusion of the colloidal beads over the HA film obeys a non-Brownian power law (〈|x(t) − x(0)|2〉 ∝ tα) withα = 0.70 ± 0.05 attributed to the time-dependent friction of the viscoelastic HA film.
|
