Copper biological significance

Recently, a new natural product linking sulfur, oxygen and iron has been isolated from bacterial sources. These substances, the thiohydroxa-mic adds, are worthy of discussion in the present context even though their biological significance has yet to be defined. The copper and iron complexes of N-methyl thioformylhydroxamic acid were obtained from the culture broth of Pseudomonas fluorescens and named fluopsins C and... 

The existence of copper-nitrosyl complexes of biological significance has been briefly discussed here (Section VII). It is worth pointing out that nitrosyl complexes of other metal-containing proteins may form, and that these may be important in understanding the effects of NO on living cells. Nitrosyl complexes of many other metals are well documented (e.g., Werner and Karrer, 1918 Moeller, 1952) and include complexes of nickel, cobalt, and ruthenium. Some such complexes may be less obvious than the paramagnetic and often colorful... 

The biological significance of these reactions is considered further in Chapters 18 and 24. The 132-kDa dimeric N20 reductase from Pseudomonas stiltzeri contains four copper atoms per subunit.546 One of its copper centers resembles the CuA centers of cytochrome c oxidase. A second copper center consists of four copper ions, held by seven histidine side chains in a roughly tetrahedral array around one sulfide (S2 ) ion. Rasmussen et al. speculate that this copper-sulfide cluster may be an acceptor of the oxygen atoms of N20 in the formation of N2.546a There is also a cytochrome cdj type of nitrite reductase.1433... 

Precision The precision of the absorption value depends upon tfe precision of P, and E measurements This method for isotopic enrichment measurements by mass spectrometry has a precision of 2% as does the measurement of F by atomic absorption This precision is adequate for absorption and bioavailability studies with zinc and copper (Table I) since zinc and copper absorption are in the range of 30-70% Only fairly large changes in iron absorption can be discerned because non-heme iron absorption is typically less than 10% This may not be a serious problem in bioavailability studies since it is doubtful that very small changes in iron absorption from single foods are biologically significant ... 

A. Biological Significance of Iron, Zinc, Copper, Molybdenum, Cobalt, Chromium, Vanadium, and Nickel... 

Despite the biological significance of the triazole moiety and the success of intermolecular triazole formation, intramolecular alkyne-azide couphng remains surprisingly Hmited. On a macromolecular scale, intramolecular triazole formation can occur on specially synthesized DNA molecules [93] by cyclodimerization of solid-phase bound suitably functionalized peptides [94] or on copper surfaces to induce adhesion [95]. There are just a few traditional examples on macrocycloadditions [96-98]. 

It is also worth mentioning the biological significance of these studies and the inspiration of biology on their development. In fact, pMMO (particulate methane monooxygenase), a main enzyme in the metabolic pathway of methanotrophs, is a membrane multicopper enzyme that catalyzes the oxidation of alkanes to the corresponding alcohols [66-68], which is mimicked by the multinuclear copper systems. 

Copper is required for all forms of aerobic and most forms of anaerobic life. In humans, the biological function of copper is related to the enzymatic action of specific essential copper proteins (66). Lack of these copper enzymes is considered a primary factor in cerebral degeneration, depigmentation, and arterial changes. Because of the abundance of copper in most human diets, chemically significant copper deficiency is extremely rare (67). 

It is also clear that copper is of little significance in most of these organisms relative to its multitude of roles in multicellular eukaryotes, while in these eukaryotes the role of nickel and cobalt is further diminished. We may conjecture that biological systems did not use copper extensively before the advent of an oxidizing atmosphere based on dioxygen (Frausto da Silva and Williams, 1991). 

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