Transport through membranes

Rosenwald, A. G., Machamer, C. E., and Pagano, R. E. (1992). Effects of a sphingolipid synthesis inhibitor on membrane transport through the secretory pathway. Biochemistry 31, 3581-3590. 

Dunker, A. K., and Marvin, D. A., A model for membrane transport through a-helical protein pores, J. Theor. Biol. 72, 9-16 (1978). 

Boman, A. L., Zhang, C. J., Zhu, X. J., and Kahn, R. A. (2000). A family of ADP-ribosylation factor effectors that can alter membrane transport through the trans-GolgL Mol. Biol. Cell 11, 1241-1255. 

ABSTRACT. Synthetic receptor molecules derived from calix[4]arenes have been used in different technological applications. The use of various functionalized calix[4]arenes in selective membrane transport through supported liquid membranes, selective cation detection with chemically modified field effect transistors, as preorganized donor-7c-acceptor systems in non linear optics and in the development of monolayers with receptor headgroups is discussed. 

Marrink, S.-J., Berendsen, H.J.C. Simulation of water transport through a lipid membrane. J. Phys. Chem. 98 (1994) 4155-4168. 

Although microporous membranes are a topic of research interest, all current commercial gas separations are based on the fourth type of mechanism shown in Figure 36, namely diffusion through dense polymer films. Gas transport through dense polymer membranes is governed by equation 8 where is the flux of component /,andare the partial pressure of the component i on either side of the membrane, /is the membrane thickness, and is a constant called the membrane permeability, which is a measure of the membrane s ability to permeate gas. The ability of a membrane to separate two gases, i and is the ratio of their permeabilities,a, called the membrane selectivity (eq. 9). 

Ultrafiltration separations range from ca 1 to 100 nm. Above ca 50 nm, the process is often known as microfiltration. Transport through ultrafiltration and microfiltration membranes is described by pore-flow models. Below ca 2 nm, interactions between the membrane material and the solute and solvent become significant. That process, called reverse osmosis or hyperfiltration, is best described by solution—diffusion mechanisms. 

Through these processes dissolved substances and/or finely dispersed particles can be separated from liquids. All five technologies rely on membrane transport, the passage of solutes or solvents through thin, porous polymeric membranes. 

L. J. Brice, W. H. Pirkle, Enantioselective transport through liquid membranes in Chiral separations, applications and technology, S. Ahuja (Ed.), American Chemical Society, Washington... 

The carrier should not dissolve in the feed liquid or receptor phase in order to avoid leakage from the liquid membrane. In order to achieve sufficient selectivity, minimization of nonselective transport through the bulk of the membrane liquid is required. Liquid membranes can be divided into three basic types [6] emulsion supported and bulk liquid membranes, respectively (Fig. 5-2). 

With regard to the enantioselective transport through the membrane, one advantage of liquid membrane separation is the fact that the diffusion coefficient of a solute in a liquid is orders of magnitude higher as compared to the diffusion coefficient in a solid. The flux through the membrane depends linearly on the diffusion coefficient and concentration of the solute, and inversely on the thickness of the membrane [7]. 

Addition of a chiral carrier can improve the enantioselective transport through the membrane by preferentially forming a complex with one enantiomer. Typically, chiral selectors such as cyclodextrins (e.g. (4)) and crown ethers (e.g. (5) [21]) are applied. Due to the apolar character of the inner surface and the hydrophilic external surface of cyclodextrins, these molecules are able to transport apolar compounds through an aqueous phase to an organic phase, whereas the opposite mechanism is valid for crown ethers. 

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