Oxyhemocyanin copper complexes

Oxygenic photosynthetic organisms, [2Fe-2S] ferredoxins, 38 224-233 Oxygenyl ion, preparation of, 9 229 Oxyhalides, of berkelium, 28 49, 51-53 Oxyhalogeno cations, 9 276-279 Oxyhemerythrin, 40 373-374, 45 84 XAS, 36 325 Oxyhemocyanin, 40 363 m-peroxo dinuclear copper complexes as models for, 39 41-52 physicochemical properties, 39 47-48 Oxyhemocyanins, XAS, 36 326-327 Oxyhemoglobin, 21 135 Oxyiodonium cations, 9 277 Oxymanganese phthalocyanine, strucmre of, 7 31-35... 

A. ix-Peroxo Dinuclear Copper Complexes as Models for Oxyhemocyanin and... 

The oxidative addition model for reversible O2 binding by metal proteins is also reasonable for hemocyanin. Hemocyanin is a copper protein which binds one O2 molecule for every two copper atoms. The deoxy Cu(I) form has no appreciable absorption in the visible region. When oxygenated, the protein is blue and exhibits a rich visible spectrum, wiA bands at 700 (c 75), 570 (c 500), 440 (c 65), and 347 nm (c 8900) (53). The pattern of bands around 570 nm leaves little doubt that oxyhemocyanin contains Cu(II) (53). The enhanced LF band intensities further suggest a dimeric Cu(II) complex. For comparison. 

As mentioned above, there are several cases of protein dioxygen-copper adducts which have been characterized only by spectroscopy (i.e., tyrosinase) and/or protein x-ray crystallography. The latter cases include oxyhemocyanins, and lower resolution examples are reported for amine oxidase and cytochrome c oxidase. Far more detailed structures are now available for small molecule synthetic complexes, as described below. 

This extended series of ligands and their Cu(II) complexes have been prepared as spectroscopic models (observable in visible and near-IR regions) for determining the geometries and ligand coordination of copper proteins. From their results it was possible to propose the following structures for the copper coordination and geometry in (blue) type I copper proteins and for the copper site in oxyhemocyanin (251). 

Pate JE, Cruse RW, Karlin KD, Solomon EL 1987. Vibrational, electronic, and resonance Raman spectral studies of [Cu2pCYL-0-)02], a copper(II) peroxide model complex of oxyhemocyanin. J Am Chem Soc 109 2624-2630. 

Baldwin MJ, Root DE, Pate JE, Fujisawa K, Kitajima N, Solomon EL 1992. Spectroscopic studies of side-on peroxide-bridged binuclear copper(II) model complexes of relevance to oxyhemocyanin and oxytyrosinase. JAm Chem Soc 114 10421-10431. 

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