Planar membranes

W. Vonau, U. Enseleit, F. Gerlach, and S. Herrmann, Conceptions, materials, processing of miniaturized electrochemical sensors with planar membranes. Electrochim. Acta 49, 3745—3750 (2004). 

Lyotropic lamellar (La) liquid crystals (LC), in a form of vesicle or planar membrane, are important for membrane research to elucidate both functional and structural aspects of membrane proteins. Membrane proteins so far investigated are receptors, substrate carriers, energy-transducting proteins, channels, and ion-motivated ATPases [1-11], The L liquid crystals have also been proved useful in the two-dimensional crystallization of membrane proteins[12, 13], in the fabrication of protein micro-arrays[14], and biomolecular devices[15]. Usefulness of an inverted cubic LC in the three-dimensional crystallization of membrane proteins has also been recognized[16]. 

At some point, these kinetic results for insulin on a biological membrane should be compared to kinetic results for insulin on an artificial lipid membrane, when such results become available. This comparison should be especially interesting in view of the suggestion by Sui et a/.(124) that nonspecific equilibrium binding of insulin to planar membranes is a function not only of membrane charge but also of some sort of nonelectrostatic mechanism, based on their TIRF experiments with a chamber adapted to a standard spectro-fluorimeter chamber. 

H. M. McConnell, T. H. Watts, R. M. Weis, and A. A. Brian, Supported planar membranes in studies of cell-cell recognition in the immune system, Biochim. Biophys. Acta 864, 95-106 (1986). 

C. L. Poglitsch and N. L. Thompson, Interaction of antibodies with Fc receptors in substrate-supported planar membranes measured by total internal reflection fluorescence microscopy, Biochemistry 29, 248-254 (1990). 

C. L. Poglitsch and N. L. Thompson, Substrate-supported planar membranes containing murine antibody Fc receptors A total internal reflection fluorescence microscopy study, in Biosensor Technology, Fundamentals and Applications (R. P. Buck, W. E. Hatfield, M. Umafiia, and E. F. Bowden, eds.), pp. 375-382, Marcel Dekker, New York (1990). 

It is important to attain as high an area as possible for a membrane reactor. Configurations with multilayer planar membranes, coiled membranes, or as multiple tubes also can be used for similar processes with potentially very high surface areas, as sketched in Figure 12-6. 

A system underpinned by commercially made screen-printed electrochemical cells was described by Palmisano et al. [19]. The cells were converted into biosensors for lactate in milk and yoghurt by addition of an electrochemically polymerised barrier to interference and a layer composed of lactate oxidase, glutaraldehyde and BSA. These steps appeared to have been carried out by hand. As there was no outer diffusion-limiting membrane, the linear range of the sensors was quite small (0-0.7 mM). They were incorporated into a FIA with a microdialysis unit based on a planar membrane and a buffer reservoir (earlier work used a microdialysis fibre with a platinum electrode [29]. The concentration of lactate was determined in various milks (0.27-1.64 mM), and in raw milk (c. 0.5-0.9 mM) left to degrade on the laboratory bench. The recovery of the microdialysis unit, 2.6%, implied that the sensor had an ability to return measurable currents for very low concentrations of lactate. A further implication is that the electro-polymerised layer was very effective at preventing interference. 

Frisch has developed explicit expressions for the time lag in diffusion of a gas across a planar membrane when the diffusion coefficient is concentration dependent (29). Using his generalized method of solution,... 

Brian and H. M. McConnell, Allogeneic stimulation of cyto-toxic T-cells by supported planar membranes, Proc. Natl. Acad. Sci. 81, 6159—6163 (1984). 

N. L. Thompson, K. H. Pearce, and H. V. Hsieh, Total internal reflection fluorescence microscopy Application to substrate-supported planar membranes, Eur. Biophys. J. 22, 367-378 (1993). 

Z. P. Huang and N. L. Thompson, Imaging fluorescence correlation spectroscopy Nonuniform IgE distributions on planar membranes, Biophys. J. 70, 2001-2007 (1996). 

C. Lagerholm, T. E. Starr, Z. N. Volovyk, and N. L. Thompson, Rebinding of IgE Fabs at haptenated planar membranes Measurement by total internal reflection with fluorescence photobleaching recovery, Biochemistry 39, 2042-2051 (2000). 

Gutsmann, T., Haberer, N., Carroll, S.F., Seydel, U., Wiese, A. Interaction between lipopolysaccharide (LPS), LPS-binding protein (LBP), and planar membranes, Biol Chem 382 (2001a) 425 134. 

This distribution is formally identical with the normal (Boltzmann) distribution of small independent, planar membranes of area S in the potential (1/2)B(u — n0)2... 

The problem also sheds some light on the Leahy data [30]. First, there is the problem of using a non-planar membrane in a clamp-RDC, as discussed above. Second, he was using an inner compartment concentration of 0.1 mM, and assuming steady state kinetics, which work in this laboratory has clearly shown do not apply under their conditions. 

Thicker, self-supporting, dense metal membranes are known. These are tubular and are usually commercially successful palladium-silver hydrogen separation membranes were of this type.21 Currently, Power and Energy, Inc. also fabricates this type of membrane, although planar membranes are more common due to easier fabrication and a greater variety of fabrication methods. 

Figure 8.12. (a) Planar membrane module (photo courtesy of Hy9 Corporation) and (b) tubular... 

Yamamoto T, Tahara K, Setaka M, Yano M, Kwan T. Permeability properties of a multilayer planar membrane. J Biochem (Tokyo) 1980 Dec 88(6) 1819-1827. 

Finally, we note that a growing body of evidence shows that the stability of a planar membrane can be enhanced by spreading it across a small aperture [97], For example, a DiPhyPC bilayer suspended across a 150nm radius orifice in a glass pipet remains intact when removed from buffer [150], This suggests that it may be possible to form arrays in which fluid, stable bilayer patches are surrounded by a patterned substrate that anchors the membrane. Air stability can also be achieved by coating a PSLB with a hydrophilic polymer film (e.g., a biospecifically adsorbed protein layer [23,149]). Both of these approaches maintain some degree of lateral lipid mobility in the membrane. 

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