Multiple recognition

Schlegel, R.A., Krahling, S., Callahan, M.K., and Williamson, P., 1999, CD14 is a component of multiple recognition system used by macrophages to phagocytose apoptotic... 

It is apparent that multiple recognition mechanisms are active in taste and odor recognition. There is now emerging evidence of multiple receptors and transduction mechanisms. The complex olfactory component of a flavor requires a mechanism with multiple receptors and several transduction pathways to be sufficiently sensitive ai discriminating to distinguish among closely relat materials. 

We now can prepare, in principle, enzyme models by use of the concept of host design, where artificial enzymes are so designed as multiple recognition hosts schematically shown in Fig. 20. Although unsubstituted cyclodextrins are well known to catalyze some organic reactions such as ester hydrolysis, their catalytic activities are relatively small. Recent progress in cyclodextrin chemistry has shown that it is possible to enhance the catalytic... 

Fig. 20. Artificial enzyme design based on the concept of multiple recognition.

Another beautiful example of multiple recognition by the use of multi-functionalized cyclodextrin is symmetrical triamino-O-permethyl-a-cyclo-dextrin (16), which is designed for the specific recognition for the phosphate group (Fig. 23) (55). As is expected, 16 shows a higher affinity toward benzyl phosphate (Kass = 3.2 x 104) than does the corresponding monoammonium derivative (Kaas = 3.3 x 101). 

Introduction of a single catalytic group in cyclodextrin generally affords enzyme models as shown in many examples listed in Table XVI. Thus, reasonable acceleration and substrate specificity were observed in these models. However, monosubstituted cyclodextrins seem to have limitations and introduction of two or more functional groups is usually necessary for multiple recognition and for a sophisticated enzyme model. 

Development of ditopic receptors 58 for both an anion and a cation is a logical extension [19b]. It should be stressed that the recognition by cyclodextrins, calixarenes, hemicarcerands, and many other systems does not involve specific recognition sites, whereas tetrahedral recognition by 53 and 54, the adenine 56 selective binding, and multiple recognition like the one shown in formula 59 [20] require the presence of specific sites in receptor capable of directional interactions. 

Multiple recognition and catalysis in ATP hydrolysis with increased ATP/ADP selectivity has been achieved with a multifunctional anion receptor containing a macrocyclic polyamine as anion binding site, an acridine group as stacking site and a catalytic site for hydrolysis (structure 82) [4.27]. Phosphoryl transfer is accelerated by other types of hydrogen-bonding receptors [5.24a]. 

Fig. 7.20 Conceptual depiction of the multiple stepwise and orthogonal self-assembly strategies employed by Week and co-workers. Clockwise from left universal polymer backbone (UPB) functionalized with multiple recognition motifs (left) UPB functionalized with single recognition unit (top) cross-...

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