Polymer-Cushioned Bilayer Lipid Membranes

With only a few exceptions, metal-supported biomimetic membranes consist of a more or less complex architecture that includes a lipid bilayer. In order of increasing complexity, they can be classified into solid-supported bilayer lipid membranes (sBLMs), tethered bilayer lipid membranes (tBLMs), polymer-cushioned bilayer lipid membranes (pBLMs), S-layer stabilized bilayer lipid membranes (ssBLMs), and protein-tethered bilayer hpid membranes (ptBLMs). 

Keywords Tethered lipid bilayer membrane Polymer cushion Lipopolymer... 

Wagner ML, Tamm LK (2000) Tethered polymer-supported planar lipid bilayers for reconstitution of integral membrane proteins Silane-polyethyleneglycol-lipid as a cushion and covalent linker. Biophys J 79 1400-1414... 

Fig. 2 The construction of a polymer-cushioned lipid bilayer membrane. (A) Architecture constructed in a sequential way first, onto the functionalized substrate a polymer layer (cushion) is deposited by adsorption from solution and covalent binding, followed by the (partial) covalent attachment of a lipid monolayer containing some anchor lipids as reactive elements (B) able to couple the whole monolayer to the polymer cushion. (C) Alternatively, a lipopolymer monolayer, organized, e.g., at the water-air interface can be co-spread with regular low-mass amphiphiles and then transferred as a mixed monolayer onto a solid support, prefunctionalized with reactive groups, able to bind covalently to the polymer chains of the lipopolymer molecules, (B). (D) By a fusion step (or a Langmuir Schaefer transfer) the distal lipid monolayer completes the polymer-tethered membrane architecture...

Lipid bilayer membranes tethered to plasma-polymerized films as hydrophilic supports were another concept introduced recently [28], The plasma polymerization of maleic anhydride (MAH-PP), e.g., has led to the synthesis of thin polymeric coatings that appear to be suitable to act as a reservoir for an aqueous phase and a cushion for lipid bilayers [29], A crucial requirement for the use of such polymers as water containing supports for lipid bilayer membranes is their adhesion to the substrate. In a previous study [30] covalent binding of MAH-PP films to gold supports was achieved by a self assembled alkylthiol adhesion layer. The previous work has shown that maleic anhydride, when polymerized at a low duty cycle, can behave as a polyelectrolyte. The thin polymer layers were found to have a very low electrical resistance (ca. lOOQcm2) after immersion and subsequent hydrolysis/swelling in aqueous buffer. 

The schematics of the preparation protocol for plasma-polymer-tethered bilayers are given in Fig. 13 mixed vesicles containing a negative and a zwitterionic lipid were fused in a Ca2+ containing buffer solution onto decylamine derivatized MAH-PP films. The MAH-PP layer appears to form a sub-membrane architecture, which exhibits some of the properties required for biomimetic membrane supports by acting as a polyelectrolyte cushion for the fluid bilayer membrane. 

Another most interesting aspect concerns the mechanical coupling of the polymer cushion with the membranes and their incorporated proteins. This could lead to interfacial architectures that show interesting features of structure formation by the coupling of the specific entropy driven properties of polymers in general with the self-organization capability of lipid bilayer structures. Experiments along these lines are under way. 

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