Lock-and-key interactions

The explosion of supramolecule architectures makes the elaboration of new receptors an obvious target of future investigation. Buckets are endpoints of a continuum of supramolecules based on rings and other cylindrical structures [413], These related macromolecules demonstrate bucket-type, lock-and-key interactions that are similar to those of CDs and calixarenes. The unique physical and chemical properties of the different supramolecule reporter sites enable the selectivity and sensitivity of analyte recognition to be exquisitely tuned. Depending on the analyte and the application, it is likely that new supramolecule architectures will be the cornerstones of many new chemosensor platforms. 

Another technique which has been used to prepare 3-D polyhedra is Raymond s symmetry-interaction method.19 This strategy derives from the realization that many natural supramo-lecular assemblies are formed in a symmetry-driven process which relies on incommensurate lock-and-key interactions. By closely examining a desired polyhedral structure, one may establish the relevant symmetry interactions and their associated geometric relationships, and then design metal-ligand systems capable of fulfilling them. 

It is becoming obvious that because of the previously unsuspected problems of multi-structure complexes, cooperativlty, conformational changes, and allotopy, the problem of drug-receptor complexes is very much more Involved than the classical concept of a "lock—and-key" interaction. 

Affinity Chromatography. This technique involves the use of a bioselective stationary phase placed in contact with the material to be purified, the ligate. Because of its rather selective interaction, sometimes called a lock-and-key mechanism, this method is more selective than other lc systems based on differential solubiHty. Affinity chromatography is sometimes called bioselective adsorption. 

Early in the last century, Emil Fischer compared the highly specific fit between enzymes and their substrates to that of a lock and its key. While the lock and key model accounted for the exquisite specificity of enzyme-substrate interactions, the imphed rigidity of the... 

The binding of a substrate to its active center was first postulated by E. Fisher in 1894 using the lock and key mechanism which states that the enzyme interacts with its substrate like a lock and a key, respectively, i.e. the substrate has a matching shape to fit into the active site. This theory assumed that the structure of the catalyst was completely rigid and could not explain why the macromolecule was able to catalyze reactions involving large substrates and not those with small ones, or why they could convert non natural compounds with different structural properties to the substrate. 

Figure 4.34 shows the form of the interacting metal and ligand NHOs and the final own NBO for H4W(NH3), n = 1. (Corresponding plots for n = 2 and 3 are very similar.) The complementary lock-and-key overlap of the donor and acceptor hybrids is apparent in Fig. 4.34(a). The localized ammine— metal (nL nM ) interaction depicted in Fig. 4.34(a) is representative of sigma donation in a large number of metal-ligand complexes. 

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