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Active site intensity

Uncovering of the three dimentional structure of catalytic groups at the active site of an enzyme allows to theorize the catalytic mechanism, and the theory accelerates the designing of model systems. Examples of such enzymes are zinc ion containing carboxypeptidase A 1-5) and carbonic anhydrase6-11. There are many other zinc enzymes with a variety of catalytic functions. For example, alcohol dehydrogenase is also a zinc enzyme and the subject of intensive model studies. However, the topics of this review will be confined to the model studies of the former hydrolytic metallo-enzymes. [Pg.145]

The elucidation of the X-ray structure of chymotrypsin (Ref. 1) and in a later stage of subtilisin (Ref. 2) revealed an active site with three crucial groups (Fig. 7.1)-the active serine, a neighboring histidine, and a buried aspartic acid. These three residues are frequently called the catalytic triad, and are designated here as Aspc Hisc Serc (where c indicates a catalytic residue). The identification of the location of the active-site groups and intense biochemical studies led to several mechanistic proposals for the action of serine proteases (see, for example, Refs. 1 and 2). However, it appears that without some way of translating the structural information to reaction-potential surfaces it is hard to discriminate between different alternative mechanisms. Thus it is instructive to use the procedure introduced in previous chapters and to examine the feasibility of different... [Pg.171]

Hydrodenitrogenation (HDN) is an important process in petroleum refining. It removes nitrogen from oil distillates, so that less NOx pollutes the air when oil is burned and poisoning of the subsequent refining catalysts is reduced when the oil is processed further. Although HDN has been studied intensively and different reaction mechanisms, catalytic active sites, and functions of the catalytic components have been proposed, there are stiU many questions to be answered in order to better mderstand the reaction and the catalyst (1-4). [Pg.87]

Imura, K., Okamoto, H., Hossain, M. K. and Kitaj ima, M. (2006) Visualization of localized intense optical fields in single gold-nanoparticle assemblies and ultrasensitive Raman active sites. Nano Lett., 6, 2173-2176. [Pg.54]

The reactions of carbon dichalcogenides other than C02 with Ni° have also been studied quite intensively.2460,2461 Inter alia, Ni polymeric complexes with metallic properties have been prepared using CS2 as the starting material.2462 Some further impetus was given by the observation that CS2 can mimic the binding of CO to the CODH enzyme active site, although CS2 itself does not undergo oxidation/reduction and does not appear to bind to center C (the site of CO oxidation and C02 reduction).2463... [Pg.500]

Infrared studies show that when water is adsorbed on the surface, the background intensity in the hydroxyl region increases new bands may appear but hydrogen-bonding effects make such conclusions uncertain. If such a catalyst is then exposed to hydrogen (or deuterium), no bands due to adsorbed hydrogen (or deuterium) are observed. Thus, adsorption of water apparently occurs on the active sites and blocks out type I chemisorption. [Pg.11]

The potential at which the Pt-H stretch appeared, and the correlation between its subsequent increase in intensity and the rise in the cathodic hydrogen evolution current, is extremely strong evidence that this form of Had9 is the intermediate in the H2-evolution reaction as studied by Schuldiner (1959). This resolved the paradox between the kinetic results and the electrochemical measurements since Bowden. Clearly, the on-top hydrogen is only present at extremely low coverage, presumably on active sites. The strongly and weakly bound hydrogen play no part in the reaction. [Pg.253]


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