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Membrane concentration dependence

Afonin, S., Durr, U. H. N., Wadhwani, P., et al. (2008) Solid state NMR structure analysis of the antimicrobial peptide gramicidin S in lipid membranes concentration-dependent realignment and self-assembly as a P-barrel, in Topics in Current Chemistry, 273, Bioactive Conformation (ed. T. Peteas) Springer, Berlin, pp. 139-154. [Pg.492]

The diffusivity of a component dissolved in a liquid or in a polymeric film depends strongly on its concentration. As the concentration of the dissolved species change from the feed to the permeate side of the membrane, concentration-dependent diffusion coefficient have to be introduced into Eq. (10). Different expressions have been proposed to relate diffusivity to concentration. One of the more commonly used relations is... [Pg.157]

Salt flux across a membrane is due to effects coupled to water transport, usually negligible, and diffusion across the membrane. Eq. (22-60) describes the basic diffusion equation for solute passage. It is independent of pressure, so as AP — AH 0, rejection 0. This important factor is due to the kinetic nature of the separation. Salt passage through the membrane is concentration dependent. Water passage is dependent on P — H. Therefore, when the membrane is operating near the osmotic pressure of the feed, the salt passage is not diluted by much permeate water. [Pg.2035]

FIG. 22-81 Permeant -concentration profile in a pervaporation membrane. 1— Upstream side (swollen). 2—Convex curvature due to concentration-dependent permeant diffiisivity. 3—Downstream concentration gradient. 4—Exit surface of membrane, depleted of permeant, thus unswollen. (Couttesy Elseoier )... [Pg.2054]

The retention efficiency of membranes is dependent on particle size and concentration, pore size and length, porosity, and flow rate. Large particles that are smaller than the pore size have sufficient inertial mass to be captured by inertial impaction. In liquids the same mechanisms are at work. Increased velocity, however, diminishes the effects of inertial impaction and diffusion. With interception being the primary retention mechanism, conditions are more favorable for fractionating particles in liquid suspension. [Pg.348]

Figure 4. Concentration-dependent ion channel blockade by (R)-JV-methylanatoxinol. The patterns identified as bursts and separated by long (>8 msec) closed intervals are indicated with a bar, the figure was designed to show approximately 2 bursts per trace. The dose-related decrease in mean channel open time resulted from the blockade of the open channel by the (R)-A -methylanatoxinol. The channel amplitude is related to membrane voltage (as was given in Figure 3) by the slope conductance such that 1 pA is equivalent to 30 mV. Continued on next page. Figure 4. Concentration-dependent ion channel blockade by (R)-JV-methylanatoxinol. The patterns identified as bursts and separated by long (>8 msec) closed intervals are indicated with a bar, the figure was designed to show approximately 2 bursts per trace. The dose-related decrease in mean channel open time resulted from the blockade of the open channel by the (R)-A -methylanatoxinol. The channel amplitude is related to membrane voltage (as was given in Figure 3) by the slope conductance such that 1 pA is equivalent to 30 mV. Continued on next page.
Figure 16(a) (O) shows the EMF responses of a 1,2-dichloroethane membrane containing anionic sites (KT/ C1PB). A Nernstian response was obtained. An SHG response to KCl was observed at activities of the latter above 10 M [Fig. 16(b), O]-These results can be interpreted in the same way as for ionophore-incorporated PVC liquid membranes, for which we have shown that the concentration of oriented cation complexes at the liquid-liquid interface can explain both the observed SHG signal and EMF response. The present SHG responses thus suggest primary ion concentration dependent charge separation at the interface of the 1,2-dichloroethane membranes incorporated with ionic sites. [Pg.467]

Fluorescence-based methods do not directly measure ionic current but, rather, measure either membrane-potential-dependent or ion-concentration-dependent changes of fluorescence signals (from fluorescent dyes loaded into the cytosol or cell membrane) as a result of ionic flux. Because fluorescence-based methods give robust and homogeneous cell population measurement, these assays are relatively easy to set up and achieve high throughput. [Pg.48]

Figure 5 shows the diffusion of a solute into such an impermeable membrane. The membrane initially contains no solute. At time zero, the concentration of the solute at z = 0 is suddenly increased to c, and maintained at this level. Equilibrium is assumed at the interface of the solution and the membrane. Therefore, the corresponding membrane concentration at z = 0 is Kc1. Since the membrane is impermeable, the concentration on the other side will not be affected by the change at z = 0 and will still be free of solute. This abrupt increase produces a time-dependent concentration profile as the solute penetrates into the membrane. If the solution is assumed to be dilute, Fick s second law Eq. (9) is applicable ... [Pg.55]

This expression can be modified to apply directly to any of various techniques used to measure the interaction parameter, including membrane and vapor osmometry, freezing point depression, light scattering, viscometry, and inverse gas chromatography [89], A polynomial curve fit is typically used for the concentration dependence of %, while the temperature dependence can usually be fit over a limited temperature range to the form [47]... [Pg.516]

Both active and passive transport occur simultaneously, and their quantitative roles differ at different concentration gradients. At low substrate concentrations, active transport plays a major role, whilst above the concentration of saturation passive diffusion is the major transport process. This very simple rule can be studied in an experimental system using cell culture-based models, and the concentration dependency of the transport of a compound as well as asymmetric transport over the membrane are two factors used to evaluate the presence and influence of transporters. Previous data have indicated that the permeability of actively absorbed compounds may be underestimated in the Caco-2 model due to a lack of (or low) expression of some uptake transporters. However, many data which show a lack of influence of transporters are usually derived from experiments... [Pg.114]

The recovery of neurotransmitters from synaptic clefts and their storage in cytoplasmic vesicles is accomplished by the tandem actions of the secondary transporters in plasma and vesicular membranes. Sodium-dependent symporters mediate neurotransmitter reuptake from synaptic clefts into neurons and glia, whereas proton-dependent antiporters concentrate neurotransmitters from neuronal cytoplasm into synaptic vesicles (Fig. 5-13). [Pg.84]


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See also in sourсe #XX -- [ Pg.885 ]

See also in sourсe #XX -- [ Pg.885 ]

See also in sourсe #XX -- [ Pg.885 ]




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