Lipids polymer membrane

Hybrid lipid-polymer membranes are interesting to study in combination with the insertion of proteins. As an example, PDMS-Z>-PMOXA copolymers of different lengths were mixed with various lipids to study phase separation and insertion of the membrane protein Mlokl. By modulating the composition of polymer-lipid mixtures, the properties of the films changed the protein distribution between the polymer and lipid phases. Thus, the distribution of proteins can be controlled according to the composition of the hybrid polymer-lipid membrane. 

Kolusheva S, Wachtel E, Jelinek R (2003) Biomimetic lipid/polymer colorimetric membranes molecular and cooperative properties. J Lipid Res 44 65-71... 

E. Evans and D. Needham Attraction Between Lipid BUayer Membranes in Concentrated Solutions of Nonadsorbing Polymers Comparison of Mean-Field Theory with Measurements of Adhesion Energy. Macromolecules 21, 1822 (1988). 

Polymeric phospholipids based on dioctadecyldimethylammonium methacrylate were formed by photopolymerization to give polymer-encased vesicles which retained phase behavior. The polymerized vesicles were more stable than non-polymerized vesicles, and permeability experiments showed that vesicles polymerized above the phase transition temperature have lower permeability than the nonpolymerized ones [447-449]. Kono et al. [450,451] employed a polypeptide based on lysine, 2 aminoisobutyric acid and leucine as the sensitive polymer. In the latter reference the polypeptide adhered to the vesicular lipid bilayer membrane at high pH by assuming an amphiphilic helical conformation, while at low pH the structure was disturbed resulting in release of the encapsulated substances. 

CARS microscopy has emerged as a highly sensitive analytical tool for vibrational bioimaging, predominantly, of lipids in membrane model systems [69, 81-84], live unstained cells [85-95, 43], and both ex vivo and in vivo tissues [26, 96-103, 43]. Examples of CARS imaging applications in the physical and material sciences include the study of fracture dynamics in drying silica nanoparticle suspensions [104], patterned polymeric photoresist film [105], drug molecules in a polymer matrix [106], and liquid crystals [107, 108],... 

One long-term objective of this research is to utilize the finest attributes associated with the worlds of both biological and synthetic materials to create nanomechanical systems powered by biological motors. Important fields of application include miniaturized (nanofluidic) analytical systems,131 molecular sorting,132 controlled adaptation of materials on a molecular to mesoscopic scale,133 and engineering lipid and polymer membrane systems with cellular processes.134... 

Ion channels play an essential role in medical diagnostics and drug development. Such applications require the integration of ion channels together with a lipid bilayer into an artificial microstructured polymer membrane (Fig. 4). The polymer membrane is attached to a metal coated optical prism. The membrane contains micropores of approximately one micrometer in diameter. Lipid bilayers are stretched across the pores. The bilayers host the receptor molecules. After activation of an ion channel, thousands of ions stream into the cavity below the ion channel. The change of ion concentration can easily be detected by SPR measurements. 

Fig. 4 Ion channel biosensor. The ion channels and their surrounding lipid bilayer are accommodated in a microstructured polymer membrane. Gating of the ion channel by an analyte results in an influx of ions into the pore. The concentration change is detected by surface plasmons, which are excited by light in the underlying metal layer...

When cells in culture are treated with a polymer solution the sur ce of each cell is exposed to the solution. The cell is isolated from its surrounding by a cellular membrane, alternatively named cytoplasmic membrane. When cells in culture are used, all interactions between polymer and cytoplasmic membranes are uniform and can be easily measured. Beyond that point, the situation remains quite cmnplex. The interior cell is again divided by lipid containing membranes into many compartments that p-event a uniform distribution of macromolecules in the cytc lasmk space. Thus, there are cellular spaces, again separated from the qhoplasm by membranes, that can stay completely free of polymer and consequently, free of any inhibition that the polymer may exert. 

Figure 8.29. Ion transport mechanisms through lipid membranes in living cells. There are principally two kinds of transport protein (a) channel proteins, that is, a channelforming ionophore, and (b) carrier proteins, that is, a mobile ion carrier ionophore. The phenomena observed in living cells have much in common with those in artificial polymer membrane ion-selective electrodes. (From Widmer, 1993.)...

Keywords Lipid bilayer Liposome Lipo-polymer Planar lipid membrane Poly(lipid) Polymerizable lipid Stabilized membrane... 

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...

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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