E Active site

Zhang, Z.-Y., Dixon, J. E. Active site labeling of the yersinia protein tyrosine phosphatase The determination of the pKa of active site cysteine and the function of the conserved histidine 402. Biochem. 32 (1993) 9340-9345. 

The previously reported relationship (eq. (3.10)) manifests one more important characteristic of the catalyst level rate coefficients—for the same reaction, temperature, catalytic agent, and support but for different surface arrangement, i.e. active site concentration, these coefficients will be different and this is an advantage of the usage of kp and in general, of turnover frequency (active site level reaction description). 

In principle, more or less stable BRC structures can be obtained in heterogeneous biomimics, especially when adsorption and catalytic sites are combined, i.e. active sites perform both functions fixation and transformation of the substrate. To put it another way, the above enumerated restrictions typical of homogeneous catalysis are absent in heterogeneous mimic-substrate complexes, where acidic-basic sites are fixed in required points of the active site. 

The effective diffusivity Dn decreases rapidly as carbon number increases. The readsorption rate constant kr n depends on the intrinsic chemistry of the catalytic site and on experimental conditions but not on chain size. The rest of the equation contains only structural catalyst properties pellet size (L), porosity (e), active site density (0), and pore radius (Rp). High values of the Damkohler number lead to transport-enhanced a-olefin readsorption and chain initiation. The structural parameters in the Damkohler number account for two phenomena that control the extent of an intrapellet secondary reaction the intrapellet residence time of a-olefins and the number of readsorption sites (0) that they encounter as they diffuse through a catalyst particle. For example, high site densities can compensate for low catalyst surface areas, small pellets, and large pores by increasing the probability of readsorption even at short residence times. This is the case, for example, for unsupported Ru, Co, and Fe powders. 

Suzuki, H. Kneller, M. B. Rock, D. A. Jones, J. P. Trager, W. F. Rettie, A. E. Active-site characteristics of CYP2C19 and CYP2C9 probed with hydantoin and barbiturate inhibitors. Arch Biochem Biophys. 2004, 429 (1), 1-15. 

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