Zinc-containing

Naturally occurring zinc contains five stable isotopes. Sixteen other unstable isotopes are recognized. 

The Palmerton, Pennsylvania, plant had 43 retorts with an output of ca 8 t/d per retort. Recovery was ca 94% when the plant was shut down in 1980. The zinc contained ca 0.3% lead, 0.10% cadmium, and 0.01% iron plus minor impurities. Lead and aluminum are added to produce galvanizer s zinc. 

The removal of silver from lead is accomplished by die addition of zinc to the molten lead, and slowly cooling to a temperature just above the melting point of lead (600 K). A crust of zinc containing the silver can be separated from the liquid, and the zinc can be removed from tlris product by distillation. The residual zinc in the lead can be removed eitlrer by distillation of the zinc, or by pumping chlorine tluough the metal to form a zinc-lead chloride slag. 

Carboxypeptidases are zinc-containing enzymes that catalyze the hydrolysis of polypeptides at the C-terminal peptide bond. The bovine enzyme form A is a monomeric protein comprising 307 amino acid residues. The structure was determined in the laboratory of William Lipscomb, Harvard University, in 1970 and later refined to 1.5 A resolution. Biochemical and x-ray studies have shown that the zinc atom is essential for catalysis by binding to the carbonyl oxygen of the substrate. This binding weakens the C =0 bond by... 

Several different groups of zinc-containing motifs have been observed... 

Two zinc-containing motifs in the glucocorticoid receptor form one DNA-binding domain... 

In contrast to the zinc-containing DNA-binding domains described so far, the GAL4 family contains a cluster of two zinc atoms liganded to six cysteine residues, and two of these cysteines (residues 11 and 28) are bound to... 

The world of zinc-containing DNA-binding proteins is by no means exhausted by these three subfamilies. Several other subfamilies are already known with different three-dimensional structures and different sequence patterns of cysteine and histidine residues that form the zinc ligands. Further subfamilies may well be discovered as the genomes of different species are sequenced whether or not any fundamentally new principles for DNA-protein recognition will be discovered amongst these new subfamilies remains to be seen. 

Several different groups of zinc-containing motifs have been observed The classic zinc fingers bind to DNA in tandem along the major groove... 

Brasses Brasses are basically alloys of copper and zinc, containing between about 10 and 45 l o Zn, but many other additions are made and the resulting alloys are the most complicated of all the copper-base series. The singlephase (a) brasses, containing up to about 37 7o Zn in the binary alloys, may have additions of 1% Sn (Admiralty brass), 2 7o A1 (aluminium-brass), or... 

The excellent resistance of zinc to corrosion under natural conditions is largely responsible for the many and varied applications of the metal. In fact nearly half the world consumption of zinc is in the form of coatings for the prevention of corrosion of steel fabrications exposed to the atmosphere and to water. For its varied applications zinc is obtainable in a number of grades. Ordinary commercial (G.O.B.) zinc contains up to about I -5% total of lead, cadmium and iron. Electrolytic zinc has a minimum zinc content of 99-95% and contains small amounts of the same impurities. Special high-purity zinc has a minimum of 99-99% zinc. Even purer zincs are commercially available. 

The purity of the zinc used in the galvanising bath is not critical. Grades which contain just over 1% lead are usually used indeed, lead is essential to avoid operational problems. Lead is soluble in molten zinc up to about 1%, but slab zinc containing a higher percentage of lead is helpful as the excess lead separates and prevents dross from sticking to the bottom of the bath and thus aids its removal. Aluminium is often deliberately added in very small quantities (about 0.005%) to brighten the appearance of the work... 

Schmid, E. V., Painting of Zinc Surfaces and Zinc-Containing Anticorrosive Primers, Monograph No. 3, OCCA, Wembley, UK (1986)... 

As you can judge from Table A, transition metal cations are frequently found in enzymes. The Zn2+ ion alone is known to be a component of at least 70 different enzymes. One of these, referred to as "alcohol dehydrogenase," is concentrated in the liver, where it acts to break down alcohols. Another zinc-containing enzyme is involved in the normal functioning of oil glands in the skin, which accounts for the use of Zn2+ compounds in the treatment of acne. 

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