Heterogenization of Complexes and Enzymes

W. Keim, B. Dreissen-Holscher, Supported catalysts. Deposition of active component. Heterogenization of complexes and enzymes, in G. Ertl, H. Knoezinger, J. Weitkamp (Eds.), Preparation of Solid Catalysts, Wiley-VCH, Weinheim, 1999, p. 355. 

Heterogenization of Complexes and Enzymes W. Keim and B. Drieben-Holscher... 

Keim W.Driessen-Holscher B (1999) Supported catalysts. Deposition of active component Heterogenization of complexes and enzymes. In Ertl G, Knoezinger H, Weitkamp J (eds) Preparation of solid catalysts. WUey-VCH,Weinheim,p 355... 

The heterogenization of complexes is directed towards immobilizing the catalytic centers which ensure the high activity and selectivity of the heterogenized complexes. In the case of immobilized enzymes the situation is quite different (sec Section B4.15). Enzymes act in aqueous media under mild conditions very specifically. They arc not always ideal catalysts for practical... 

This review will focus on the homogeneous catalysis of H-H bond cleavage and formation by discrete transition metal complexes and enzymes. These topics have been the subject of a number of excellent reviews [3-21]. This review will not discuss in detail the electrochemical reduction or H2 oxidation [22-24], or the heterogeneous activation of H2 by extended systems [25-29]. 

Most immunoassay kits and many commercial immunoassay analyzers are based on heterogenous EIA or FIA. These include an immunoassay system that uses FIA linked to radial partition chromatography of the antibody—antigen complex (39) a system that uses antibody-coated tubes for enzyme immunoassay of a variety of hormones and dmgs (40) and a system that uses either a sandwich or competitive FIA format to measure a variety of analytes (41). 

Immobilized enzymes and immobilized cells can be used in principle as heterogeneous catalysts not only for the enhancement of hydrolytic reactions but also in specific synthetic reactions. Many of the enzymes involved in the synthesis of complex biological compounds -in vivo and in vitro require cofactors which have to be provided in suitable form when immobilized enzymes or cells are used. 

We may then view the relationship between homogeneous, heterogeneous, and enzyme catalysis as depicted in Fig. 29. The two dominant features of heterogeneous metal catalysis, the importance of low coordination number sites to break chemical bonds and the structural properties of overlayers that control the path of more complex surface reactions, are the bridges between these fields. Future studies will verify how well these views are justified. 

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