Synzyme

Many transition metal complexes have been considered as synzymes for superoxide anion dismutation and activity as SOD mimics. The stability and toxicity of any metal complex intended for pharmaceutical application is of paramount concern, and the complex must also be determined to be truly catalytic for superoxide ion dismutation. Because the catalytic activity of SOD1, for instance, is essentially diffusion-controlled with rates of 2 x 1 () M 1 s 1, fast analytic techniques must be used to directly measure the decay of superoxide anion in testing complexes as SOD mimics. One needs to distinguish between the uncatalyzed stoichiometric decay of the superoxide anion (second-order kinetic behavior) and true catalytic SOD dismutation (first-order behavior with [O ] [synzyme] and many turnovers of SOD mimic catalytic behavior). Indirect detection methods such as those in which a steady-state concentration of superoxide anion is generated from a xanthine/xanthine oxidase system will not measure catalytic synzyme behavior but instead will evaluate the potential SOD mimic as a stoichiometric superoxide scavenger. Two methodologies, stopped-flow kinetic analysis and pulse radiolysis, are fast methods that will measure SOD mimic catalytic behavior. These methods are briefly described in reference 11 and in Section 3.7.2 of Chapter 3. 

The oxidation of methyl phenyl sulfide using fresh PWAA gave methyl phenyl sulfone in 97% yield. In the repeated use of recovered catalyst, the yields of sulfone in runs 2 to 5 ranged from 82 to 88%. The activities of recovered catalysts were somewhat reduced. The deactivation may be caused by catalyst pulverization or degradation of the PW12O403- species. While the reusability and stability of the catalyst should be improved, this concept would be useful for the creation of sophisticated solid catalysts. After Ikegami s reports, Neumann and coworkers [140] applied this strategy to the development of alkylated polyethyleneimine/POM synzymes. 

Samal S, Geckeler K (2001) DNA-cleavage by Fullerene-Based Synzymes. Macromolecular... 

From the practical viewpoint, enzyme-like synthetic catalysts, or syn-zymes, need not be specific for a given reactant structure. In nature enzymes distinguish among closely related molecules and transform only the substrate for which it is specific. Mixtures of molecules may not be involved in the industrial reaction to be catalyzed. Reaction specificity is, of course, a requirement. A synthetic hydrolase should not catalyze other reactions such as decarboxylation. Enzymes bring about rate enhancements of 10 -lO. A synzyme could be of great practical importance with far less efficiency than the natural enzyme if it is cheap and stable. In other words, a near miss in an attempt to mimic enzymes could be a fabulous success. 

Attempts to make enzyme-like catalysts, synzymes, from nonbiological systems is described by G. P. Royer. The final two chapters by Y. Yamazaki and T. Kawai, and Z. Paal deal with catalytic hydrocarbon conversions using acids and metals, respectively, as catalysts. 

Riley, D.P., Henke, S.L, Lennon, P.J., Aston, K. Computer-aided design (CAD) of synzymes use of molecular mechanics (MM) for the rational design of superoxide dismutase mimics. Inorg. Chem. 1999, 38(8), 1908-1917. 

Biological catalysts in the form of enzymes, cells, organelles, or synzymes that are tethered to a fixed bed, polymer, or other insoluble carrier or entrapped by a semi-impermeable membrane . Immobilization often confers added stability, permits reuse of the biocatalyst, and allows the development of flow reactors. The mode of immobilization may produce distinct populations of biocatalyst, each exhibiting different activities within the same sample. The study of immobilized enzymes can also provide insights into the chemical basis of enzyme latency, a well-known phenomenon characterized by the limited availability of active enzyme as a consequence of immobilization and/or encapsulization. 

Enzyme-like Synthetic Catalysts (Synzymes) G. P. Royer... 

SYNZYMES SYNTHETIC POLYMERS WITH ENZYMELIKE CATALYTIC ACTIVITIES... 

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