Electron paramagnetic resonance copper complexes

A reaction mechanism for the above reactions was proposed which consists of initial formation of the copper precursor complexes of Fig. 3 (without coordinated phenolate), coordination of phenolate, electron transfer from phenolate to Cu2+ and subsequent reduction to Cu1+ with formation of a phenoxy radical, and reoxidation of Cu1+ to Cu2+ with oxygen. Various copper(II) catalysts having different stereochemistries (octahedral or tetrahedral coordination) due to coordination of amines like pyridine (Py) or acetate (OAc) groups in different ligand sites were observed by NMR and electron paramagnetic resonance techniques. 

Windle, J. J., A. L. Wiersema, J. R. Clark, and R. E. Feeney Investigation of the iron and copper complexes of avian conalbumins and human transferrins by electron paramagnetic resonance. Biochemistry 2, 1341 (1963). 

The ESR spectrum of a Cu complex with hydrolyzed ascidiacyclamide suggested that a ligandimetal ratio of 1 1, a single monomeric copper(ll) complex, is formed in solution while computer simulation of electron paramagnetic resonance (EPR) spectra indicated a 1 2 ratio <1996IC1095>. 

Goodman, B. A. (1980). Exchange of comments on the simulation of electron paramagnetic resonance spectra of copper-fulvic acid complex. Anal. Chem. 52, 1770-1771. 

Goodman, B. A. and Cheshire, M. V. (1973). Electron paramagnetic resonance evidence that copper is complexed in humic acid by the nitrogen of porphyrin groups. Nature (London) 244, 158-159. 

We have mentioned earlier the dissimilarities between the spectral properties of chromophoric metal ions at the active sites of metalloen-zymes and the properties of simple bidentate model complexes of the same metals. Cobalt phosphatase has served well to illustrate such a dissimilarity and, in Figure 9, the data for phosphatase, representative of a cobalt enzyme, are shown again along with those for plastocyanin, a copper enzyme, and ferredoxin, an iron enzyme. Each enzyme spectrum is unusual compared with the simple model complexes shown at the bottom of the figure. More detailed spectral data as well as comparison of other physical properties of metalloenzymes—e.g., electron paramagnetic resonance spectra—with those of model complexes have been summarized previously (10). 

Fig. 14. Electron paramagnetic resonance spectra of low molecular mass copper complexes in the presence and in the absence of bovine serum albumin (BSA). All four copper concentrations are identical. Cu-EDTA served as standard. Cu flonazolac) displays no EPR-signal due the antiferromagnetic coupling of the two copper-centers. After addition of BSA, a signal of the biuret-type is obtained, indicating that the original complex was disrupted. A similar signal is seen after addition of CuSO, to BSA...

J.J.WiNDLE, A. K. Wiersema, J.R.Clark and R.E.Feeney, Investigation of the Iron and Copper Complex of Avian Conalbumin and Human Transferrin by Electron Paramagnetic Resonance, Biochemistry, N.Y. 2, 1341—1345 (1963). 

Zweier J, Aisen P, Peisach J, Mims WB. 1979. Pulsed electron paramagnetic resonance studies of the copper complexes of transferrin. JBiol Chem 254 3512-3515. 

Like the studies with optical rotatory dispersion, studies with electron spin (paramagnetic) resonance not only have revealed important differences among the metal-free transferrins and their metal complexes but also have given insight into the nature of the binding sites and the structure of the complexes. Aasa et al. (1) reported on the iron and copper complexes of human serum transferrin and chicken ovotransferrin while Windie et al. 137) reported on human serum transferrin, human lacto-transferrin, chicken ovotransferrin, quail ovotransferrin, and turkey ovotransferrin. 

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