Permeation inhibition

D.H. Coleman, B.N. Popov, R.E. White, Hydrogen permeation inhibition by thin Layer Zn-Ni alloy electrodeposition, J. Appl. Electrochem. 28 (1998) 889—894. 

Relatively unambiguous monotonic SARs also occur where activity depends on the ionization of a particular functional group. A classic example (Fig. 5) is that of the antibacterial sulfonamides where activity is exerted by competitive inhibition of the incorporation of j -amin ohenzoic acid into foHc acid (27). The beU-shaped relationship is consistent with the sulfonamide acting as the anion but permeating into the cell as the neutral species. 

Corrosion-inhibiting primers based on this technology have been in continuous service since they were first utilized with nitrile epoxies in the late 1960s. These inhibitors function by passivating the aluminum. In this process, water permeating the adhesive bondline carries a certain amount of inhibitor to the oxide surface. 

The blood-brain barrier (BBB) forms a physiological barrier between the central nervous system and the blood circulation. It consists of glial cells and a special species of endothelial cells, which form tight junctions between each other thereby inhibiting paracellular transport. In addition, the endothelial cells of the BBB express a variety of ABC-transporters to protect the brain tissue against toxic metabolites and xenobiotics. The BBB is permeable to water, glucose, sodium chloride and non-ionised lipid-soluble molecules but large molecules such as peptides as well as many polar substances do not readily permeate the battier. 

Myers R. L., Pandey V.N. Anti-TAR polyamide nucleotide analog conjugated with a membrane-permeating peptide inhibits human immunodeficiency virus type 1 production./. Virol. 2002 76 3881-3891. 

In many bioconversions, product inhibition is critical and this forces the transformations to relatively low concentrations, so if a membrane that selectively permeates the desired product could work in a dirty environment, this would be very useful. 

FIGURE 50-5 A model for the transduction of odors in OSNs. The individual steps are detailed in the text. Note that several feedback loops modulate the odor response, including inhibition of the CNG channel by Ca2+ ions (purple balls) that permeate the channel, and a Ca2+/calmodulin (CaM) -mediated desensitization of the channel that underlies rapid odor adaptation. Several other mechanisms, including phosphodiesterase-mediated hydrolysis of the second messenger, cAMP, and phosphorylation of the OR by various kinases, have also been described. 

Chemical Resistant Materials Materials that are specifically designed to inhibit or resist the passage of chemicals into and through the materials by the processes of penetration and permeation. 

Catalysis at multilayered electrode coatings is then addressed. Besides the rate of the catalytic reaction within the film and the diffusion of the substrate and products between the bulk of the bathing solution and the film-solution interface, the current response depends on two additional factors permeation of the substrate through the film, and transport of electrons through the film. Analysis of the first of these factors also involves a discussion of the inhibition of the electrode electron transfer that the presence of a film on the electrode surface may cause, whether the electrode is covered by a monolayer or by a thicker film. This discussion also addresses the important case where inhibition is due to deposition onto the electrode surface of one of the reaction products. 

This means that even substances administered to the periphery of the body display an effect on the CNS which can no longer be observed later on. Clonidine induces sleep in these animals, as described by ZAIMIS (49), FUGNER and HOEFKE (50) and by DELBARRE and SCHMITT (51). Noradrenaline, as well as a-methylnoradrenaline, which cannot permeate the blood-brain barrier in older animals, cause sleep. This effect could be inhibited with phentolamine in the case of noradrenaline and also in the case of clonidine (FUGNER (52)). Therefore it may be assumed, that here again central adrenergic alpha-receptors are involved. 

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