Membrane tethered bilayer lipid membranes

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... 

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],... 

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). 

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). 

Krysinski, P., Zebrowska, A., Palys, B., and Lotowski, Z. (2002) Spectroscopic and electrochemical studies of bilayer lipid membranes tethered to the surface of gold. Journal of the Electrochemical Society, 149, I ls" 1194. 

P. Krysinski, A. Zebrowska, A. Michota, J. Bukowska, L. Becucci, M. Moncelli, Tethered mono-and bilayer lipid membranes on Au and Hg. Langmuir 17, 3852 (2001)... 

Seitz M ef al 1998 Formation of tethered supported bilayers via membrane-inserting reactive lipids Thin Solid Films 327-9 767-71... 

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). 

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). 

Recently, Brzozowska et al. used NR and ex situ electrochemical techniques to characterize an innovative type of monolayer system intended to serve as a support for a bUayer lipid membrane on a gold electrode surface [51]. Zr ions were used to noncovalendy couple a phosphate-terminated self-assembled monolayer (SAM) formed on a gold surface to the carboxylate groups of negatively charged phos-phatidylserrne (PS). This tethered surface was then used for the formation of a PS hpid bilayer structure formed by vesicle fusion and spreading. NR studies revealed the presence of an aqueous environment associated with the tether layer which arises from nonstoichiometric water associated with the zirconium phosphate moieties [52]. 

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. 

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

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. 

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. 

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. 

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