Solid Supported Membranes

In foe latter case, the two phases are separated by a hydt ophohk ot liydtophilic membrane (solid supported interface). The engynie is soluble in the-aqueous phase and substrate is added up to its maximum solubility in foe aqueous phase. Substrates and. products are distributed according to their hydrophilic or hydro-phobic properties. Use membrane axes has to be large enough to avoid mass transfer limitations. High membrane areas may he achieved fey Hat membrane stacks or fey hollow fiber modules. 

Solid-infusion processes Emulsion liquid membranes Solid-supported liquid membranes Fnam fractionation Bubble fractionation... 

Other methods of preparing bilayer membranes, which lead to more robust systems and longer lifetimes include filter-supported, solid-supported, and gel-supported membranes. Solid-supported membranes doped with ion-selective antibiotics were only used in conjunction with amperometric (porous Teflon membrane with nonactin for NH3) or conductivity (steel-supported membrane with valinomycin for measurement modes. Agar gel-supported bilayer membranes with incorporated valinomycin showed Nemstian responses for different alkali cations. ... 

Once the membrane was successfully produced, it was analysed for characterisation and scanning. The sol-gel technique was successfully used to obtain a crack-free unsupported membrane, which was expected to have pore size of 1-2 nm. The development of the crack-free membrane may not have the same strength without strong, solid support. The next stage of this work was to characterise the fabricated membrane. Hie objectives of this study were to develop a zirconia-coated 7-alumina membrane with inorganic porous support by the sol-gel method and to characterise the surface morphology of the membrane and ceramic support. 

Figure 16.22 shows SEM micrographs for the porous media of ceramic support at different magnifications. The non-uniformity resulted from the synthetic foam used as a base to absorb the ceramic solution before vaporising any water from the inorganic mixture. Uniform porous media as a solid support for the membrane was obtained. 

Cellulose was the first type of solid support introduced for SPPS [91 ] however, the scope of its use is limited by low loading capacity ( 0.1 mmol/g) and chemical stability. In spite of these drawbacks, microwave-assisted synthesis was successfully performed on cellulose membranes [92-94] and beads [95]. 

In the first step, lipid model membranes have been generated (Fig. 15) on the air/liquid interface, on a glass micropipette (see Section VIII.A.1), and on an aperture that separates two cells filled with subphase (see Section VIII.A.2). Further, amphiphilic lipid molecules have been self-assembled in an aqueous medium surrounding unilamellar vesicles (see Section VIII.A.3). Subsequently, the S-layer protein of B. coagulans E38/vl, B. stearother-mophilus PV72/p2, or B. sphaericus CCM 2177 have been injected into the aqueous subphase (Fig. 15). As on solid supports, crystal growth of S-layer lattices on planar or vesicular lipid films is initiated simultaneously at many randomly distributed nucleation... 

Composite aperture-spanning membranes resist electron beam under low-dose conditions A significant increase in the mechanical stability of solid—supported lipid membranes is observed... 

P. S. (2007) Separation of membrane-bound compounds by solid-supported bilayer electrophoresis./. Am. Chem. Soc., 129, 8072-8073. 

The high specificity required for the analysis of physiological fluids often necessitates the incorporation of permselective membranes between the sample and the sensor. A typical configuration is presented in Fig. 7, where the membrane system comprises three distinct layers. The outer membrane. A, which encounters the sample solution is indicated by the dashed lines. It most commonly serves to eliminate high molecular weight interferences, such as other enzymes and proteins. The substrate, S, and other small molecules are allowed to enter the enzyme layer, B, which typically consist of a gelatinous material or a porous solid support. The immobilized enzyme catalyzes the conversion of substrate, S, to product, P. The substrate, product or a cofactor may be the species detected electrochemically. In many cases the electrochemical sensor may be prone to interferences and a permselective membrane, C, is required. The response time and sensitivity of the enzyme electrode will depend on the rate of permeation through layers A, B and C the kinetics of enzymatic conversion as well as the charac-... 

Loidl-Stahlhofen, A., Eckert, A., Hartmann, T Schottner, M. Solid-supported lipid membranes as a tool for determination of membrane affinity high-throughput screening of a physicochemical parameter. J. Pharm. Sci. 2001, 90, 599-606. 

Loidl-Stahlhofen, A. Hartmann, T. Schottner, M. Rohring, C. Brodowsky, H. Schmitt, J. Keldenich, J., Multilamellar liposome and solid-supported lipid membranes (TRAN-SIL) Screening of lipid-water partitioning toward a high-throughput scale, Pharm. Res. 

Antico, E. Masana, A. Hidalgo, M. Salvado, V. Valiente, M. New sulfur-containing reagents as carriers for the separation of palladium by solid supported liquid membranes. Hydrometallurgy 1994, 35, 343-352. 

For the preparation of the triazine membranes, the entire solid support (cellulose or polypropylene membrane) was treated with a 5 m solution of the corresponding amine in l-methyl-2-pyrrolidinone (NMP) and a 1 m solution of cesium phenolate in dimethyl sulfoxide (2 p L of each at one spot) and subsequently heated in a domestic microwave oven for 3 min. After washing the support successively with... 

A similar approach has been described by the same authors for the synthesis of related cyclic peptidomimetics [44]. A set often nucleophiles was employed for the substitution of the chlorine atom of the cyclic triazinyl-peptide bound to the cellulose membrane. By virtue of the aforementioned rate enhancement effects for nucleophilic substitution of the solid-supported monochlorotriazines, these reactions could be rapidly carried out by microwave heating. All products were obtained in high purity, enabling systematic modification of the molecular properties of the cyclic peptidomimetics. 

Here, we discuss a solid-state 19F-NMR approach that has been developed for structural studies of MAPs in lipid bilayers, and how this can be translated to measurements in native biomembranes. We review the essentials of the methodology and discuss key objectives in the practice of 19F-labelling of peptides. Furthermore, the preparation of macroscopically oriented biomembranes on solid supports is discussed in the context of other membrane models. Two native biomembrane systems are presented as examples human erythrocyte ghosts as representatives of eukaryotic cell membranes, and protoplasts from Micrococcus luteus as membranes... 

For the orientation-based structure analysis of MAPs, uniformly oriented lipid bilayers are typically prepared on solid supports as illustrated in Fig. 2 [23, 47, 55]. These mechanically oriented membranes are advantageous for static ssNMR experiments, as they provide a robust way to orient a sample with any desired lipid composition, peptide concentration, and at any desired temperature. The lipids... 

Fig. 5 Membrane models for NMR structure analysis, (a) An isotropic detergent micelle (left) is compared to the dimensions of lipid bilayers (right), (b) Macroscopically oriented membrane samples can be prepared on solid support, as nanodiscs, or as magnetically oriented bicelles. (c) Nomenclature and variability of liposomes small (SUV, 20-40 nm), intermediate (IUV, 40-60 nm), large (LUV, 100-400 nm), and giant unilamellar vesicles (GUV, 1 pm) multi-lamellar (MLV), oligo-lamellar (OLV) and highly heterogeneous multi-oligo-lamellar vesicles (MOLV)...

Compared to the sizes of living cells,1 IUV and LUV resemble the dimensions of enveloped viruses (ranging from 80 to 400 nm) [94], while GUVs resemble typical bacteria and erythrocytes (1-7 pm). Eukaryotic cells tend to be even larger (10-30 pm in animals, 10-100 pm in plants). These dimensions imply that, except for viruses or specific sub-cellular membranes, flat bilayers are the only relevant membrane models. Hence, macroscopically oriented bilayers on solid supports (see... 

Several manufacturers introduced products amenable for this solid-supported LLE and for supported liquid extraction (SLE). The most common support material is high-purity diatomaceous earth. Table 1.8 lists some commercial products and their suppliers. The most widely investigated membrane-based format is the supported liquid membrane (SLM) on a polymeric (usually polypropylene) porous hollow fiber. The tubular polypropylene fiber (short length, 5 to 10 cm) is dipped into an organic solvent such as nitrophenyl octylether or 1-octanol so that the liquid diffuses into the pores on the fiber wall. This liquid serves as the extraction solvent when the coated fiber is dipped... 

Immobilization of the bilayer membranes as thin solid films is required when the bilayer membranes are used as novel functional materials. Casting method is a simple way to immobilize the bilayer membrane on a solid support from an aqueous solution by drying. Polymer film is easily prepared when the cast film of polymerizable bilayer membrane is polymerized. A free standing polymer film prepared by photo polymerization of the cast film of diacetylene amphiphiles was reported by O Brien and co-workers [34]. Composition with macromolecular materials is another way of polymer film preparation. Bilayer membranes are immobilized as polymer composites by the following physical methods ... 

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