The degree of domain registration in a liquid-ordered/liquid-disordered phase-separating lipid mixture consisting of 1-stearoyl-2-oleoyl-sn-3-phosphocholine, egg sphingomyelin, and cholesterol (molar mixing ratio of 1:1:1) was studied using three different planar lipid bilayer architectures distinguished by their bilayer-substrate distance d using epifluorescence microscopy. The bilayer systems, which were built layer by layer using Langmuir-Blodgett/Schaefer film depositions, included a solid-supported bilayer (d approximately 15 A) and two polymer-supported bilayers with d approximately 30 A and d approximately 58 A, respectively. Complete domain registration between Langmuir-Blodgett and Schaefer monolayer domains was observed for d approximately 58 A but not in the cases when d approximately 15 A and d approximately 30 A. Building the bilayer layer by layer guaranteed that any preexisting domains were not in registration initially; our data show that the domain registration observed was not caused by lipid flip-flop or by lateral rearrangement of preexisting large-scale domains. Instead, additional studies on bilayer systems with asymmetric lipid composition indicate that preexisting domains in the Langmuir-Blodgett monolayer induce the formation of completely registered domains in the opposite Schaefer monolayer. This study provides insight into possible biophysical mechanisms of transbilayer domain coupling. Our findings support the concept that the formation of transbilayer signaling platforms based on registered raft domains may occur without the active involvement of membrane-spanning proteins.

We report a simple method to confine transmembrane cell receptors in stripe micropatterns of a lipid/lipopolymer monolayer, which are formed as result of the transfer onto a solid substrate. The stripes are aligned perpendicular to the meniscus, whose periodicity can systematically be tuned by the transfer velocity. This strongly suggests the dominant role of the cooperative interaction between the film and substrate. Selective fluorescence labeling of lipids and lipopolymers confirms that the observed patterns coincide with the demixing of two species. Covalent coupling of polymer headgroups enables us to use the stripe patterns as a support for a lipid bilayer membrane. Spreading of lipid vesicles with platelet integrin alphaIIbbeta3 on a self-assembled membrane micropattern demonstrates that cell adhesion receptors are selectively incorporated into the lipopolymer-rich region. The method established here provides us with a tunable template for the confinement of receptor proteins to geometrically control the cell adhesion.

The micelle formation of five poly(2‐oxazoline) diblock, triblock and gradient copolymers in water was investigated using fluorescence correlation spectroscopy. The polymers were synthesized by consecutive or simultaneous living cationic polymerization of 2‐methyl‐2‐oxazoline for the hydrophilic and 2‐nonyl‐2‐oxazoline for the hydrophobic polymer segments. Fractions of the polymers were fluorescence‐labeled at the polymer termini with TRITC for the FCS measurements. The hydrodynamic radii of solubilized polymer unimers and of the aggregates (micelles) were determined in a concentration range of 10−8–10−3 M and were found to depend in a characteristic way on the polymer architecture.

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Amphiphilic poly(2‐alkyl‐2‐oxazoline) diblock copolymers of 2‐methyl‐2‐oxazoline (MOx) building the hydrophilic block and either 2‐nonyl‐2‐oxazoline (NOx) for the hydrophobic or 2‐(1H,1H′,2H,2H′‐perfluorohexyl)‐2‐oxazoline (FOx) for the fluorophilic block were synthesized by sequential living cationic polymerization. The polymer amphiphiles form core/shell micelles in aqueous solution as evidenced using small‐angle neutron scattering (SANS). Whereas the diblock copolymer micelles with a hydrophobic NOxn block are spherical, the micelles with the fluorophilic FOxn are slightly elongated, as observed by SANS and TEM. In water, the micelles with fluorophilic and lipophilic cores do not mix, but coexist.