Recognition principles

S-2.2.2 Neutral Carrier Electrodes hi addition to charged liquid ion exchangers, liquid-membrane electrodes often rely on the use of complex-forming neutral carriers. Much effort has been devoted to the isolation or synthesis of compounds containing cavities of molecular dimensions. Such use of chemical recognition principles has made an enormous impact upon widespread acceptance of ISEs. The resulting neutral carriers can be natural macrocyclic molecules or synthetic crown... 

Tou. J. T., and Gonzalez, R. C, Pattern Recognition Principles. Addison-Wesley, Reading, MA, 1974. 

Fig. 10.2 (A) Cross-section SEM micrograph of the hybrid membrane containing the receptor 1, (B) membrane transport concentration profiles and (C) molecular recognition principles of acidic I and zwitterionic II L-phenylalanine in the heteropoly-siloxane material membrane (1-hydrogen bonding, 2-charge interaction, 3-Van der Waals forces) [29].

Another approach to the construction of optically active chochins of known chirality — the so-called chiral recognition principle — involves the coupling of the optically active [2.2]paracyclophane derivative (R)-46 16) with the racemic mixture of the [3]chochm derivative 47. From the two diastereomeric [5]chochins which could be expected thereof, the one with (J )(S)(S)-chirality (see Fig. 2) because of eclipsed steric interactions is thermodynamically less stable than the (R)(R)(R)-isomer with Z)2-symmetry. The latter (44) was indeed the only product isolated from... 

Application of molecular recognition principles allows the design of small molecules able to interact with biological systems for use, e.g. as anticancer drugs. 

Development of Polymer Membrane Anion-Selective Electrodes Based on Molecular Recognition Principles... 

In order to develop selective electrodes, it is necessary to introduce specific interactions between the ionophore and the anion of interest. This can be achieved by designing an ion carrier whose structure is complementary to the anion. This type of design can be based on molecular recognition principles, such as the ones that involve complementarity of shape and charge distribution between the ion and the ionophore. 

In this paper, we report the development of ISEs that have been designed by using molecular recognition principles. Specific examples include the development of polymer membrane anion-selective electrodes based on hydrophobic vitamin B12 derivatives and a cobalt porphyrin. The selectivity patterns observed with these electrodes can be related to differences in the structure of the various ionophores, and to properties of the polymer film. 

In summary, it has been demonstrated that ISEs can be designed by employing molecular recognition principles. In particular, the feasibility of using hydrophobic vitamin B12 derivatives and electropolymerized porphyrin films in the development of polymer membrane anion-selective electrodes has been demonstrated. The studies indicated that the changes in the selectivity of these ISEs can be explained by the difference in structure of the ionophores. In addition, it was shown that by electropolymerization of a cobalt porphyrin, anion-selective electrodes can be prepared that have extended lifetimes compared with PVC-based ISEs, which use a similar compound as the ionophore. 

Chemical sensors utilize the immunological recognition principle by coupling with optical, electrochemical, or other transducer (signal transfer) described e.g. by Eggins (1996) and Rogers et al. (1998). A tendency to miniaturized formats ( chips ) as part of the nanotechnology can be observed. 

Elgavish, S. and Shaanan, B. (1997). Lectin-carbohydrate interactions different folds, common recognition principles. Trends Biochem. Sci. 22, 462-467. 

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