Cadmium-substituted proteins chemical

It is essential to note the importance of knowing whether chemical exchange is present within a given metal nuclide system, before one draws any firm conclusions about the relative importance of the various relaxation mechanisms or of the presence of internal motions. Although the present analysis and its conclusions are applicable to Con A, it is not clear whether they can be applied to any other cadmium-substituted protein, unless it is known that chemical exchange processes are operational and that the exchange rates are comparable to the relaxation rates. At this point, we can put aside the question of chemical dynamics and turn our attention to the significance of the observed chemical shifts. 

Cadmium-113 nuclear magnetic resonance studies of the cadmium substituted bovine superoxide dismutase were carried out Only a very small chemical-shift difference between the 2 Cd(Il) protein (Cd(II) is bound to the zinc site and the copper site is unoccupied) and the 2 Cd(ll)—2 Cu(I) enzyme (analogous to the reduced form of the native protein) was found. This was interpreted in that the imidazolate bridge is protonated at the Cu site after reduction. 

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