Membrane protein-tethered bilayer lipid membranes

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... 

Figure 1. a) Direct patterning of inert materials using UV-NIL. Nanoarrays of b) protein and c) tethered bilayer lipid raft membrane on the imprinted inert barrier using a stepwise molecular self-assanbly. 

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). 

Baumgartner and coworkers [145,146] study lipid-protein interactions in lipid bilayers. The lipids are modeled as chains of hard spheres with heads tethered to two virtual surfaces, representing the two sides of the bilayer. Within this model, Baumgartner [145] has investigated the influence of membrane curvature on the conformations of a long embedded chain (a protein ). He predicts that the protein spontaneously localizes on the inner side of the membrane, due to the larger fluctuations of lipid density there. Sintes and Baumgartner [146] have calculated the lipid-mediated interactions between cylindrical inclusions ( proteins ). Apart from the... 

Supported bilayers represent biomimetic layers which can be supported on a range of materials and adapted for the study of biointeractions (protein-protein, lipid-lipid) including molecular recognition, ion-channel transport and intramembrane interactions. This interface type can be separated into the so-called SLBs (supported lipid bilayers), HBMs (hybrid bilayer membranes) and t-BLMs (tethered bilayer membranes). 

This method is a combination of the other two methods. In our opinion, it is the most gentle method to reconstitute membrane proteins into supported bilayers and to prepare supported bilayers with fragile coexisting liquid phases of lipids. A LB monolayer is prepared on a hydrophilic substrate as described above. To prepare tethered-polymer supported bilayers, a suitable lipopolymer may be included at a concentration of a few... 

In this study, we report a very effective and widely applicable method for fabricating of nanostructures of an inert material for the biomolecular nanoarrays. The stable nanostructures of the PEG and PVA hydrogels were directly fabricated on gold substrates by UV-NIL (Fig. la). The site-selective nanoarray of various biomolecules such as protein and tethered lipid bilayer raft membrane (tLBRM) was constructed from a nanoimprinted inert materials by stepwise molecular self-assembly (Fig. lb and Ic). 

FIGURE 5-11 Diagram of how various ciasses of proteins associate with the iipid biiayer. Integral (transmembrane) proteins span the bIlayer. LIpId-anchored proteins are tethered to one leaflet by a long covalently attached hydrocarbon chain. Peripheral proteins associate with the membrane primarily by specific noncovalent Interactions with Integral proteins or membrane lipids. 

Many questions pertaining to membrane processes in general and ligand/membrane receptor interactions in particular can be addressed by a novel model membrane system, i.e., polymer-supported or polymer-tethered lipid bilayers [12,14], The basic structural unit for this sensor platform is the tethered lipid bilayer membrane [16] displayed in Fig. 2D. The essential architectural elements of this supramolecular assembly include the solid support, e.g., an optical or electrical transducer (device), the polymeric tether system which provides the partial covalent and, hence, very stable attachment of the whole membrane to the substrate surface, and the fluid lipid bilayer, functionalized if needed by embedded proteins. 

Among the various membrane properties that might need to be optimized for a particular application of the tethered membrane architecture and/or of any incorporated proteins we discuss only two key performance parameters, i.e., (1) the ability of the tethering system to swell by the up-take of a sufficient amount of water into the interstitial space between the lipid bilayer and the solid support, and (2) the high lateral mobility of the individual lipid molecules in the two opposing leaflets of the bilayer membrane. 

One substantial difference between polyalanine and melittin is their effect on the membrane. Shen et al. found that the presence of the transmembrane polyalanine helix barely altered the structure and dynamics of the DMPC bilayer. Only the NMR order parameters were slightly lower, indicating that the protein did not Induce the formation of a more ordered layer of lipids. Moreover, a detailed analysis of the solvation of the helix showed that no well-defined annulus of lipids remained tethered to the protein. A similar conclusion was reached in... 

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