Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Synthetic pore formers

From a molecular theory of ion-conducting transmembrane channels [33], it was concluded that sequences with the structure A -formyl-(L-Ala-L-Ala-Gly) would form such channels. A number of such substances have been prepared by using solid-phase techniques for the synthesis of peptides. They are A -formyl-(L-Ala-L-Ala-Gly)40Me, A -formyl-L-Ala-Gly-(L-Ala-L-Ala-Gly)40Me, H (t-Ala-L-Ala-Gly)sO , H (L-Ala-L-Ala-Gly)sOMe, A -formyl-(L-Ala-L-Ala-Gly)0 and A -formyl-(L-Ala-L-Ala-Gly)sOMe. All these compounds exhibited channel behaviour when incorporated in lipid bilayers with slight selectivity [34]. Several different sizes of conductance quanta were measured with the different peptides. [Pg.10]

The possibility of designing ion-selective channel formers, particularly when tissue selectivity based upon differing membrane lipid composition can be established, is an exciting challenge for future drug design. [Pg.10]

The previous sections on single-channel conductance in Upid bilayers show that pores of molecular dimensions and possessing selectivity can be demonstrated, but can single-channel conductance be demonstrated in biological membranes, or rather, are ions translocated across biological membranes in ways similar to those in lipid bilayers treated with channel-forming substances  [Pg.10]

Doubtless, it will not be long before similar demonstrations of unit conductance can be made for other biological systems. There is already some evidence to show that, when subthreshold currents are passed through neural membranes, the potential adjustment proceeds by a series of quantal steps which probably corresponds to the opening of discrete channels [39]. [Pg.11]

The alternative approach to demonstrations of channel formation in biological membranes is to extract channels from biological materials and then to incorporate these into lipid bilayers where their biological properties can be demonstrated. Little progress has been made so far, probably because biological channels are not easily solubilised and purified, particularly when they are only present in the membrane in small amounts. Furthermore, even when isolated, the native conformation may be irrevocably lost. [Pg.11]


Figure 5 Current-voltage response of synthetic pore-former. Figure 5 Current-voltage response of synthetic pore-former.
Fig. . Pore size distribution for synthetic carbons prepared from styrene-divinylbenzene copolymers with various cross-iinKage and pore -former content (a) 10/60X (b) 30/130X (c) 30/160X (d) 40/180X. Fig. . Pore size distribution for synthetic carbons prepared from styrene-divinylbenzene copolymers with various cross-iinKage and pore -former content (a) 10/60X (b) 30/130X (c) 30/160X (d) 40/180X.
On the basis of the separation mechanism, restricted-access media can be classified into physical or chemical diffusion barrier types. The limited accessibility of the former type is due to the pore structure of the support that represents physical diffusion barriers for macromolecular compounds. The restricted access of the latter type is due to covalently or adsorptively bonded synthetic or natural polymers that cover the support surface, preventing macromolecules from being adsorbed on or denatured by the column packing material. [Pg.606]

In LC the main application has been the characterization of polymers using synthetically prepared stationary phases of varying pore sizes. The technique was formerly known by as many as eleven different names, including gel filtration and gel permeation chromatography.6 Some confusion may result from the use of these names, which are no longer recommended. [Pg.31]

Because of their advanced level of development, high sensitivity, and broad applicability, fluorescence spectroscopy with labeled LUVs and planar bilayer conductance experiments are the two techniques of choice to study synthetic transport systems. The broad applicability of the former also includes ion carriers, but it is extremely difficult to differentiate a carrier from a channel or pore mechanism by LUV experiments. However, the breadth and depth accessible with fluorogenic vesicles in a reliable user-friendly manner are unmatched by any other technique. Planar bilayer conductance experiments are restricted to ion channels and pores and are commonly accepted as substantial evidence for their existence. Exflemely informative, these fragile single-molecule experiments can be very difficult to execute and interpret. Another example for alternative techniques to analyze synthetic transport systems in LUVs is ion-selective electrodes. Conductance experiments in supported lipid bilayer membranes may be mentioned as well. Although these methods are less frequently used, they may be added to the repertoire of the supramolecular chemist. [Pg.483]


See other pages where Synthetic pore formers is mentioned: [Pg.10]    [Pg.10]    [Pg.489]    [Pg.489]    [Pg.489]    [Pg.336]    [Pg.293]    [Pg.83]    [Pg.99]    [Pg.62]    [Pg.54]    [Pg.479]    [Pg.361]    [Pg.647]    [Pg.311]    [Pg.315]    [Pg.320]    [Pg.444]    [Pg.11]    [Pg.249]    [Pg.19]    [Pg.332]    [Pg.271]   


SEARCH



Former

Pore former

© 2024 chempedia.info