Lipid vesicles, tethered supported

The artificial lipid bilayer is often prepared via the vesicle-fusion method [8]. In the vesicle fusion process, immersing a solid substrate in a vesicle dispersion solution induces adsorption and rupture of the vesicles on the substrate, which yields a planar and continuous lipid bilayer structure (Figure 13.1) [9]. The Langmuir-Blodgett transfer process is also a useful method [10]. These artificial lipid bilayers can support various biomolecules [11-16]. However, we have to take care because some transmembrane proteins incorporated in these artificial lipid bilayers interact directly with the substrate surface due to a lack of sufficient space between the bilayer and the substrate. This alters the native properties of the proteins and prohibits free diffusion in the lipid bilayer [17[. To avoid this undesirable situation, polymer-supported bilayers [7, 18, 19] or tethered bilayers [20, 21] are used. 

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]. 

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],... 

Fig. 6 (a) Schematics of a polymer-tethered lipid bilayer on a solid support the architecture is composed of a proximal mixed monolayer of lipopolymers and regular low-mass lipids, covered by a monolayer of normal lipids obtained by vesicle fusion. The lipopolymers are covalently attached to the benzophenone-derivative coated substrate by a proton-abstraction reaction as depicted in (b)... 

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. 

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