Substrate-receptor interactions

The other class of enkephalin derivatives comprises compounds in vhich the phenylalanine in position 4 has been substituted by ferrocenylalanine (Per, 23) or cymantrenylalanine (Cym, 24, see Scheme 5.15). As indicated before, the former was prepared by Schlogl as early as 1957 [1]. Later, improved syntheses for the racemic compound as well as for enantiomerically pure Per were published [56, 57, 67, 68]. Compared with Phe, the cylindrically shaped Per is much more bulky and lipophilic. The manganese tricarbonyl derivative Cym is also considered to be much more lipophilic than Phe [69]. Owing to these differences, results from binding assays for the modified peptide in comparison to those for the natural peptide could reveal important information about substrate-receptor interactions. 

It is thus a higher form of molecular "behaviour than selective com-plexation alone and involves two stages of information input. Enzyme reactions are examples of such processes, as well as, for instance, drug-receptor interactions. Two substrates could, in principle, display very similar thermodynamic and kinetic complexation behaviour (no selection) but still only one of them may be able to undergo a specific reaction (because of geometrical differences, for instance) and thus be recognized. 

Host-guest Complexes as Analogues of the Interacting Substrate-Receptor Unit in Biochemistry... 

In conclusion, then, when true steric effects have been eliminated by proper choice of the members of the data set the bulk parameter constitutes a measure of ii (dispersion) and di interactions involved in either transport across membranes or in the formation of a substrate — receptor complex. 

Photoswitchable antigen/antibody (substrate/ receptor) complexes 1. Reversible immunosensors 2. Patterning of surfaces with biomaterials using antigen/antibody-biomaterial conjugates (Design of biosensor arrays, biochips) 1. Immobilization of systems on electronic transducers (electrodes, piezoelectric crystals, FET) or the assembly of biomaterials on inert supports by non-covalent interactions (eg. glass, polymers)... 

The function of a receptor depends on its high specihcity for particular ligands. This often involves the stereochemical ht between a ligand and a receptor, the idea of a lock and key, similar to the interaction of enzymes with various substrates. It should be noted, however, that toxicant-receptor interactions are often around 100 times as strong as enzyme-substrate interactions. Furthermore, whereas an enzyme generally alters a substrate chemically (such as by hydrolysis), a toxicant does not usually change the chemical nature of a receptor other than binding to it. In... 

It seems likely that biochemists will continue to use a more pragmatic and less comprehensive approach. In biochemical processes, two important features are the structures of substrate and product. The overall steric structure of the substrate (and not just the possession of some structural feature such as a double bond) is important in terms of binding to an enzyme or receptor. Since many enzymatic reactions are readily reversible, overall product structure is important for the same reason. Furthermore, since many enzymes make more than one type of stereodifferentiation, the use of the stereo-differentiating terminology of Izumi and Tai would be somewhat cumbersome. The overall steric structure of molecules (as opposed to isolated structural features) is also important in the area of drug-receptor interactions. 

A library obtained in this way can then be examined with regard to its interaction with a receptor. It is challenging to find an easy way to identify substances which are capable of interacting with the receptor. If a binding interaction takes place, the identification of the responsible structure can be carried out as follows the receptor is labeled with a dye molecule so that an interaction can be detected optically by a change in color caused by the substrate-receptor complex. Finally, the structure of an active molecule can be deduced from the label to which it is correlated. 

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