Cupric atomic weight

The early researches of Berzelius,4 Erdmann and Marchand,5 Dumas,6 and Millon and Commaille,7 involved either syntheses or analyses of cupric oxide, the values found for the atomic weight of copper being 63-30, 63-46, 63-5, and 63-13. Dumas also made syntheses of cuprous sulphide, but gave no details concerning his experiments. His result did not differ much from the modem value, and was adopted for many years. 

The remainder of Richards s work on copper by chemical methods concerned the composition of cupric oxide and cupric sulphate, and was undertaken principally with the object of investigating the nature and magnitude of the errors of earlier workers. Cupric oxide prepared from the nitrate by ignition was found to contain occluded gases, mainly nitrogen. The impossibility of avoiding partial decomposition in the preparation of cupric sulphate free from water by dehydration of the pentahydrate was also demonstrated. At 260° C. the salt retains more than 0-1 per cent, of water, and at 400° C. 0-042 per cent. These errors vitiated the results of most of the early workers on the atomic weight of copper, and explain the low values found by Hampe. 

When 1.3305 gm. of copper were heated in oxygen, 1.6675 gm. of cupric oxide were formed. Calculate the atomic weight of copper. (The equation is Cu + O = CuO.)... 

Type II Cu(II), or low-blue copper, is less colored at common research concentrations. These systems have received less attention than Type I copper. However, even low-blue cupric copper can possess high molar absorbtivities when compared with simple coordination complexes of Cu(II). The Cu(II) sites in such proteins also yield Azz values normally greater than 140 G, i.e., more like that of low molecular weight square planar Cu(II) complexes (2, 8). The only available crystal structure of a copper protein is that of a low blue protein bovine erythrocyte superoxide dismtuase (9). The two copper atoms in this protein are each coordinated to four histidine nitrogens in an approximate square planar array. 

The protein cytochrome c oxidase, with a monomeric molecular weight of about 100,000, contains two a-type hemes and two copper atoms. A low-spin ferric heme signal and a so-called intrinsic copper signal near g = 2.0 are observed in the frozen solution EPR spectrum of the fully oxidized oxidase. The latter signal shows EPR features which one could assign either to a thiyl radical (R-S ) or to a cupric ion center with an unusually low g value Since no hf structure from copper is resolved at X- or Q-band frequencies, the controversy could not be solved unambiguously from EPR data alone. 

Ceruloplasmin. This is the most well-known and yet the least understood copper protein. It is an a2-globulin and there is conclusive evidence that this 132000 molecular weight glycoprotein has just one polypeptide chain [9]. It has 7% carbohydrate. It contains six atoms of copper per molecule. Copper in ceruloplasmin exists in both cupric and cuprous forms. Partial removal of copper from ceruloplasmin results in the loss of its characteristic blue color and loss of enzymatic activity. Ceruloplasmin has enzymatic oxidase activity toward several substrates at pH 5.4-S.9. The best substrate is p-phenylenediamine or its dimethyl derivative. Ceruloplasmin can oxidize ferrous ion to ferric ion. The ceruloplasmin level in the newborn is less than 10 mg/100 mL serum. It rises to adult levels (30.4 5 mg/lOO mL) by 2-4 months of age and continues to rise to a peak at 2-3 years and this declines to adult levels by 12 years of age. The level of ceruloplasmin is affected by various pathological states. Usually, a pronounced deficiency of this protein in serum is characteristic of both Wilson s and Menkes s diseases although normal levels have also been reported in the case of Wilson s disease. 

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