Tethered bilayer membrane

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). 

Lateral Mobility of Lipids in a Tethered Bilayer Membrane. 102... 

The tethered bilayer offer improvements in both stability and in terms of its approximation of the true cell membrane through incorporation of tethering links... 

Shenoy S, Moldovan R, Fitzpatrick J, Vanderah DJ, Desemo M, Losche M (2010) In-plane homogeneity and lipid dynamics in tethered bilayer lipid membranes (tBLMs). Soft Matter 6 1263-1274... 

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. 

Lipid rafts on cell membranes are cholesterol- and sphingolipid-rich domains that function as platforms for signal transduction and other cellular processes [6], Tethered lipid bilayers have been proposed as a promising model membrane to describe the structure and function of cell membratKs [7]. Based on these facts, we endeavor to array the lipid rafts as a form of tethered bilayer lipid membrare into the nanopattemed substrates to generate a raft membrane-based biosensing platform (Fig. Ic). 

Valincius et al. used NR and ex situ electrochemical impedance spectroscopy to study the effect of amyloid (J-pephde insertion on supported hpid bilayers [60]. It has been speculated that the interaction between these oligomeric proteins and bilayer membranes plays an important role in the aggregation and protein misfold-ing that leads to various neurodegenerahve diseases including Alzehimer s and Parkinson s diseases [61]. Using a variety of solvent and phospholipid contrasts, including the use of perdeuterated phosphohpids, NR demonstrated that amyloid P-peptides inserted into hpid bilayers tethered to a gold-modified silicon substrate. 

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). 

The 3,6-disilylated-3-vinyl-l,2-dithiins 38, obtained by the self-dimerisation of silylated allenes, undergo a Lewis aeid-promoted rearrangement to the bicyclic endodisulfide <05TL4711>. Tethered bilayer lipid membranes have been obtained using 4-hydroxy-l,2-dithianes as the anchor for coupling reactions with the lipid <05AJC738>. 

Second, several types of asymmetric supported bilayer structures, in which the composition of the two monolayers is different, have been created as alternatives to symmetric PSLBs. One example is the HBM [45,46], The inner monolayer in an HBM is an alkyl SAM, typically an alkanethiol on gold, upon which an outer lipid monolayer is deposited by either LBS or vesicle fusion methods. A more sophisticated type of asymmetric supported bilayer is the tethered bilayer lipid membrane (tBLM) in which the SAM is replaced with an inner lipid monolayer. Some or all of the molecules in the inner monolayer are covalently tethered to the underlying support, usually through a hydrophilic linker that creates a water-swollen spacer layer between the tBLM and the substrate surface [47-51],... 

For some of these polymer-tethered lipid bilayers a few key performance indicators are discussed. In particular, we describe structural parameters obtained from surface plasmon resonance spectroscopy and compare those to important functional features, i.e., the electrical capacitance and resistance of the membrane. Furthermore, the ability of the polymer tethers to swell in water and evidence for the resulting lateral mobility of the lipid molecules in the membrane as an indicator for the fluid nature of the tethered bilayers are presented. 

Keywords Tethered lipid bilayer membrane Polymer cushion Lipopolymer... 

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. 

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...

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. 

The proper function of a membrane is intimately linked to the liquid-crystalline character of its lipid bilayer matrix. Among other factors, this depends crucially on the existence of sufficient water reservoirs on both sides of the bilayer membrane. (The lipid bilayer is a thermotropic and lyotropic smectic liquid-crystal.) While this is naturally given on the distal side of the tethered membrane architecture by the aqueous phase of the flow cell, the coupling of the membrane to the substrate on the proximal layer imposes serious restrictions on the amount and free accessibility, e.g., for ions of the aqueous phase between the bilayer and the solid substrate. In this context, the tethering system not only couples and thus stabilizes mechanically the whole architecture to the support foremost it has to decouple the lipid bilayer from the strong interactions of the headgroups with the polar support. This way ... 

Fig. 12 Neutron reflectometry (NR) data of the polyelectrolyte multilayer (4 PSS/4 PAH) - coated solid support without lipid bilayer (A), and with a DMPC/DMPG (10 1) mixed membrane on top (C). The curves are shifted relative to each other for clarity. Solid lines represent model calculations of the data with scattering length densities, b/V, corresponding to the blank multilayer support (A), and to the tethered bilayer plus a nonspecific top layer (C), as given in the inset. The dotted line (B) represents a simulation of a lipid bilayer without an additional nonspecific layer on top...

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. 

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