Active sites inhomogeneity

The main application of double resonance is the resolution of hyperfine and particularly superhyperfine interactions that are not extractable from regular EPR spectra because they are lost in the inhomogeneous line. The biological relevance is in otherwise unavailable detailed information on the electronic structure and the coordination of active sites and their interaction with reactants, such as enzyme substrates. To be well prepared, check off the items in the following list. 

A real surface of a solid metal is inhomogeneous, and nucleation for the growing clusters is favored at certain active sites. To simplify the mathematics we consider an electrode with unit surface area. If there are Mo active sites, the number M(t) of growing nuclei is given by first-order kinetics ... 

Other aspects of the inhomogeneous distribution of "active sites" are discussed by Wollast and Chou (25), who suggest that their earlier estimates of residual layer thickness are minima, because restricting the residual layer to the vicinity of active sites would mean that more of the reaction takes place over a smaller area, increasing the thickness of the residual layer there. "If a residual layer exists, then it would probably cover less than 10 of the total surface and accordingly the value for the calculated thickness would be increased proportionally" (p. 

A major advance in the elimination of catalytic site inhomogeneity in new preparations came with the development of an affinity chromatographic method (65) for purifying the enzyme. This method made use of the known high affinity of xanthine oxidase for alloxanthine when the enzyme is in a fully reduced state. By attaching alloxanthine to a polymeric matrix, a selective absorption of active enzyme was achieved. 

Fig. 5 (Color online) The eneigy-level configuration for a N-V color center in diamond. The blue lines denote the inhomogeneous line centers of levels and c for all active sites in the sample. For...

The electrodeposited gold was distributed randomly as small spherical particles, with an average diameter of 60 nm, and these nanoparticles were dispersed both at the grain boundaries and on the facets, as observed in SEM studies (Fig. 17.7 a b). The active sites for gold nucleation were inhomogeneously distributed on the surface of diamond. 

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