Membrane, artificial potential

A burst of ATP synthesis accompanied the transmembrane movement of protons driven by the 10,000-fold H" concentration gradient (10 M versus 10 M). In similar experiments using "inside-out" preparations of submitochondrial vesicles, an artificially generated membrane electric potential also resulted in ATP synthesis. 

The popular applications of the adsorption potential measurements are those dealing with the surface potential changes at the water/air and water/hydrocarbon interface when a monolayer film is formed by an adsorbed substance. " " " Phospholipid monolayers, for instance, formed at such interfaces have been extensively used to study the surface properties of the monolayers. These are expected to represent, to some extent, the surface properties of bilayers and biological as well as various artificial membranes. An interest in a number of applications of ordered thin organic films (e.g., Langmuir and Blodgett layers) dominated research on the insoluble monolayer during the past decade. 

Reichel, A., Begley, D. J. Potential of immobilized artificial membranes for predicting drug penetration across the blood-brain barrier. Pharm. Res. 1998, 35,1270-1274. 

The oscillation of membrane current or membrane potential is well-known to occur in biomembranes of neurons and heart cells, and a great number of experimental and theoretical studies on oscillations in biomembranes as well as artificial membranes [1,2] have been carried out from the viewpoint of their biological importance. The oscillation in the membrane system is also related to the sensing and signal transmission of taste and olfaction. Artificial oscillation systems with high sensitivity and selectivity have been pursued in order to develop new sensors [3-8]. 

In both Navanax neurons (65) and an artificial phospholipid bilayer membrane (66). salicylic acid (1-30 mM) increased K" " permeability but decreased Cl- permeability resulting in a net Increase in membrane conductance. To account for the selective effect of salicylic acid (and other benzoic acids) on the two permeabilities, it was proposed that the anions of the organic acids adsorb to membranes to produce either a negative surface potential (66) or an increase in the anionic field strength of the membrane (47, 48). 

Zhu, C. Jiang, L. Chen, T.-M. Hwang, K.-K., A comparative study of artificial membrane permeability assay for high-throughput profiling of drug absorption potential, Eur. J. Med. Chem. 37, 399 107 (2002). 

Carotenoids are highly lipophilic an active area of research concerns how carotenoids interact with and affect membrane systems (see Chapters 2 and 10). Also, the lipid solubility of these compounds has important implications for carotenoid intestinal absorption (see Chapter 17) models such as the Caco-2 cell model are being used to conduct detailed studies of carotenoid absorption/ competition for absorption (Chapter 18). The lipid solubility of these carotenoids also leads to the aggregation of carotenoids (see Chapter 3). Carotenoids aggregate both in natural and artificial systems, with implications for carotenoid excited states (see Chapter 8). This has implications for a new indication for carotenoids, namely, serving as potential materials for harnessing solar energy. 

Detection of Li+ in artificial serum with a voltammetric Li-selective electrode in a flowthrough system was demonstrated [64], Lithium salts such as lithium carbonate have been extensively used for treatment of manic depressive and hyperthyroidism disorders. The therapeutic range of Li concentration is generally accepted to be 0.5-1.5mM in blood serum. The authors used normal pulse voltammetry in which a stripping potential was applied between pulses in order to renew the membrane surface and expel all of the extracted ions from the membrane, similar to galvanostatically controlled potentiometric sensors described above. Unfortunately, the insufficient selectivity... 

In a second approach, Sugano et al. [138] tried to consider paracellular transport in addition to transcellular permeation. The prediction of the paracellular transport potential was based on size and charge parameters together with artificial membrane permeability in relation to known human absorption values. Other groups have focused on the paracellular route by modification of the assay [26],... 

The suitability and general applicability of an artificial membrane and PAMPA in vitro permeation methods were evaluated for their ability to predict drug absorption potential in comparison to Caco-2 cell literature data [57], A linear correlation (R2 = 0.957) was obtained between artificial membrane Papp and human absorption data, indicating the good predictive ability of the proposed method for HP compounds with greater differentiation of drugs with /a below 50% [57],... 

Although artificial lipid membranes are almost impermeable to ions, biological membranes contain ion channels that selectively allow individual ion types to pass through (see p. 222). Whether an ion can cross this type of membrane, and if so in which direction, depends on the electrochemical gradient—i.e., on the concentrations of the ion on each side of the membrane (the concentration gradient) and on the difference in the electrical potential between the interior and exterior, the membrane potential. 

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