Complexes with Inorganic Substrates

In such a large subject, this article can only focus on certain aspects, namely those that involve complexation with inorganic substrates. We only consider the synthetic macrocycles, with emphasis on transition metal complexation. Aza, oxa, and, to a lesser extent, thia and phospha macrocycles are also covered. The naturally occurring porphyrins, corrins, corphins, chlorins, and phthalocyanins, as well as the cyclodextrins, are not included. Because of the general complexity of macrocychc systems and the resulting complicated systematic names, commonly used abbreviations or simplified names will be employed. This review will encompass the synthesis, thermodynamics, stmcture, and applications of macrocychc ligands. 

Effectors accelerate (activators) or block (inhibitors) the catalytic process. They are bound to the enzyme rather loosely and may therefore easily dissociate. Many of them are metal ions, e.g. Mg++) Ca++, Zn++, K+) and Na+, which either form stoichiometric complexes with the substrate, stabilize an optimal protein conformation, or effect the association of subunits. These inorganic complements of enzyme reactions are frequently subsumed together with coenzymes as cofactors. 

Smits to the Pb complexation with the substrate (16). In fact, many complexes of sugars and sugar derivatives with inorganic salts and bases were isolated in solid and often in crystalline forms. There was considerable evidence, based on various physical measurements, that sugar-cation complexes exist in solution... 

Metal Complexes with Inorganic (Main Group) Substrates... 

Figure 13.8 TMS-EDTA can be used to modify an inorganic substrate to containing EDTA chelating groups for complexation with metal ions.

Because the preceding chromogenic assay rely on choline quantitation, the hydrolysis of substrates with headgroups other than choline cannot be followed. To circumvent this problem, another useful protocol was devised whereby the phosphorylated headgroup produced by the PLCBc hydrolysis is treated with APase, and the inorganic phosphate (Pi) that is thus generated is quantitated by the formation of a blue complex with ammonium molybdate/ascorbic acid 5 nmol of phosphate may be easily detected. This assay, which may also be performed in a 96-well format, has been utilized to determine the kinetic parameters for the hydrolysis of a number of substrates by PLCBc [37,38]. 

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