Protein decorated membranes by specific molecular interactions

Abstract

Here we characterize new metal-functionalized amphiphilic diblock copolymers, developed for both surface and soln. mol. recognition applications. Polybutadiene-block-poly(ethylene oxide) copolymers functionalized with nitrilotriacetic acid and tris(nitrilotriacetic acid) were complexed with nickel(II) to obtain coordination sites for oligohistidine residues of model proteins. Mixts. of functionalized polymers with the resp. non-functionalized block copolymers self-assemble in aq. soln. into vesicular structures with a controlled d. of the metal end-groups on their surface. In soln., binding of His6-tagged green fluorescent protein (EGFP) and red fluorescent protein (RFP) to the vesicle surface was quantified by fluorescence correlation spectroscopy. Small-angle X-ray scattering indicates an increase of the membrane thickness by 2-3 nm upon protein binding. Block copolymer monolayers at the air-water interface and on solid support served as a model system to characterize the protein-decorated membranes by Brewster angle microscopy and AFM. High resoln. AFM of solid-supported, hydrated monolayers indicates that the proteins form densely packed and partially ordered arrays with the cylindrically shaped EGFP mols. lying flat on the surface of the films