Inside-out configuration

An alternative design for cylindrical cells is the so-called inside-out configuration, in which the anode, in the form of zinc sheet vanes, is centrally placed and surrounded by the cathode mix. The principal advantage of this design is its high leakage resistance which results from the fact that the cell case is no longer fabricated from zinc. 

This is a true single-channel patch clamp mode allowing the measurement of singlechannel currents with the added benefit of making it possible to change the medium to which the intracellular surface of the membrane is exposed. Thus, the inside-out configuration is particularly valuable when studying the influence of intracellular molecules on ion channel function, like calcium or ATP. 

In the inside-out configuration, the internal membrane surface is exposed to the recording chamber bath. In this way it is possible to interact directly with it, by modifying the composition of the solution of the bath. Using this configuration it is possible to study the properties of channels that are normally modulated by intracellular substances, as in the case of calcium-dependent potassium channels (see for example ref. [28]). 

Fig. 7. Inside-out patch. When the cell-attached configuration has been obtained (A), the pipette is pulled-up, and a patch of membrane is excised from the cell (B), forming the inside-out patch-clalmp configuration. In this configuration, single-channel currents are observed. When the excised membrane reseals, forming a small vesicle in the tip of the pipette, the channel current is distorted (C). In this case, the vesicle can be disrupted crossing the air-water interface (D), and the inside-out configuration is obtained.

Singer and colleagues studied the effect of non-esterified arachidonate on potassium channels by dissolving the fatty acid in the bathing medium and perfusing it on the inside of the smooth muscle membrane (in the inside-out configuration) or on its outside (in the outside-out configuration). In either case, they found that application of micromolar concentrations of the fatty acid would cause the activation of a potassium-selective channel (Fig. 3.6). This effect was not mediated by the formation of... 

Inside-out, Outside-in Filtration in Hollow-Fiber Membranes Hollow-fiber membrane modules can be operated in two different flow modes— inside-out and outside-in —based on the direction of filtration flow. In the inside-out configuration, pressurized feed water flows through the bore of a hollow fiber, and permeate is collected on the outside of the membrane fibres. In the outside-in configuration, the pressurized feed stream flows from the outside of a hollow fiber, and permeate is collected inside the bore of the hollow fiber. 

Quench. Attempts have been made to model this nonisotherma1 process (32—35), but the complexity of the actual system makes quench design an art. Arrangements include straight-through, and outside-in and inside-out radial patterns (36). The optimum configuration depends on spinneret size, hole pattern, filament size, quench-chamber dimensions, take-up rate, and desired physical properties. Process continuity and final fiber properties are governed by the temperature profile and extension rate. 

Membrane systems consist of membrane elements or modules. For potable water treatment, NF and RO membrane modules are commonly fabricated in a spiral configuration. An important consideration of spiral elements is the design of the feed spacer, which promotes turbulence to reduce fouling. MF and UF membranes often use a hollow fiber geometry. This geometry does not require extensive pretreatment because the fibers can be periodically backwashed. Flow in these hollow fiber systems can be either from the inner lumen of the membrane fiber to the outside (inside-out flow) or from the outside to the inside of the fibers (outside-in flow). Tubular NF membranes are now just entering the marketplace. 

Figure 1 Schematic diagrams illustrating the patch-clamp technique. (A) Overall setup for isolating single ionic channels in an intact patch of cell membrane. P = patch pipet R = reference microelectrode I = intracellular microelectrode Vp = applied patch potential Em = membrane potential Vm = Em — Vp = potential across the patch A = patch-clamp amplifier. (From Ref. 90.) (B) Five different recording configurations, and procedures used to establish them, (i) Cell attached or intact patch (ii) open cell attached patch (iii) whole cell recording (iv) excised outside-out patch (v) excised inside-out patch. Key i = inside of the cell o = outside of the cell. (Adapted from Ref. 283.)...

Most results on calcium transport have been obtained using cytoplasmic membrane vesicles, which may be prepared in inside-out or right-side-out configurations. Inside-out vesicles may be obtained by the disruption of E. coli cells in a French press. These then accumulate Ca2+ in an energy-dependent fashion, provided ATP or an oxidizable substrate is available. Addition of phosphate enhances the uptake of calcium as calcium phosphate is precipitated inside the tell, thus accounting for the lack of exchangeability of the calcium.186... 

For nucleophilic substitution at tetrahedral carbon, the relationships between stereochemistry and mechanism are well understood. Direct displacement on a carbon turns the molecule inside out (inversion of configuration) if the site of reaction is an asymmetric carbon, a molecule in the D series will be converted to one in the L series (or vice versa). Substitution by the dissociation mechanism at an asymmetric carbon... 

Operation Pressurized configurations can be operated in either cross-flow or dead-end modes while submerged configuration are essentially only operated in dead-end mode. Submerged systems operate with outside-in flow, while pressurized can be either outside-in or inside out flow. 

Back-side attack literally turns the tetrahedron of the carbon atom inside out, like an umbrella caught by the wind (Figure 6-7). In the product, the nucleophile assumes a stereochemical position opposite the position the leaving group originally occupied. We call this result an inversion of configuration at the carbon atom. 

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