Copper equilibrium binding studies

There are a few documented examples of studies of ligand effects on hydrolysis reactions. Angelici et al." investigated the effect of a number of multidentate ligands on the copper(II) ion-catalysed hydrolysis of coordinated amino acid esters. The equilibrium constant for binding of the ester and the rate constant for the hydrolysis of the resulting complex both decrease in the presence of ligands. Similar conclusions have been reached by Hay and Morris, who studied the effect of ethylenediamine... 

Equilibrium studies involving double-stranded trihelicates have demonstrated the co-operative nature of metal ion binding. A spectrophotometric titration investigation of the stepwise binding of copper(I) to a (substituted) tris-bipyridyl ligand system of the present type in dichloromethane-acetonitrile (1 1) indicated the formation of a single, well-defined product. From analysis of the data, the self-... 

The apparent binding constant of copper to the apoprotein were investigated with equilibrium dialysis Four different constants are found. They are pH-dependent. At low pH, two protons compete with copper in the native binding sites. This is not seen at pH 7.0 and above. At alkaline pH-values (pH 10.0) the binding constants are nearly similar. Simultaneous addition of equimolar copper and zinc at pH 5.0 to the apo enzyme results in the formation of an electrophoretically distinct metal-deficient protein species and in the incorporation of copper and zinc in a one-to-one ratio at various concentrations of added metal ions At low ratios of added equimolar metals, not all of the metal ions expected are bound. This may account for the low yields often obtained in reconstitution studies. 

Uricase has been obtained in purified form from acetone-dried pork liver mitochondria (510,512 also see 485,773). The enzyme contains tightly bound copper, and is inhibited by cyanide and other metal-binding reagents. Study of the variation of K, and Vmaz with pH suggests that the following equilibrium is involved (equation 120), the pK of the shift, I-II, being 7.2 and that for II-III being 10.3. Form II appears to be enzymically active. 

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