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Copper dinuclear sites

As a part of their efforts to model dinuclear copper active sites, Reed and co-workers reported, using alkoxo-based dinucleating ligands, a few very interesting systems from the viewpoint of magnetostructural correlations (379) (TBP Cu-Cu 3.325A 2.1 278cm ), (380) (TBP ... [Pg.817]

Interaction of dioxygen species with Fe aq and with Fe " aq has been very briefly reviewed. In relation to 0x0-, peroxo-, and superoxo-complexes as models for intermediates in oxygenase activity, a brief report on a 2000 symposium on activation of oxygen summarizes the then-current situation in the search for a mechanism common to mono- and dinuclear iron sites, mono- and dinuclear copper sites, and copper-iron sites. The outline proposals comprise ... [Pg.488]

Copper (continued) cynates, 17 322, 323 diaminodithioether complexes, 17 185 diazene complexes, 27 232 difluoride, structure, 27 85, 86, 87, 88 dinuclear sites, 40 362-367 diphosphine complexes of, 14 235-239 electron-density distributions of complexes, 27 34, 41... [Pg.62]

Usually, these metalloproteins contain both type 2 and type 3 copper centers, together forming a triangular-shaped trinuclear active site, such as found in laccase (polyphenol oxidase) [38-41] and ascorbate oxidase (3) [42]. Recent evidence for a related arrangement has been reported for the enzyme particulate methane monooxygenase as well [43], but in this case the Cu Cu distance of the type 2 subunit (2.6 A) appears to be unusually short and the third Cu ion is located far from the dinuclear site. [Pg.29]

Many metalloproteins contain more than one metal center. Tyrosinase, for example, has a dinuclear Type 3 (T3) copper active site which, in its oxidized form, comprises two Cu(II) centers each held by three histidine groups with a p-r 2 r 2 peroxido bridging ligand (Fig. 22). [Pg.24]

The majority of cyanide-bridged dinuclear complexes described for the combination of metal ions belong to the biologically relevant class of Cu —Fe dimers. These compounds serve as models for the binuclear cyanide-inhibited site of cytochrome c oxidase, an enzyme that contains the heme-copper active site responsible for the O2 reduction chemistry (59). The lethal toxicity of cyanide was traced to its irreversible binding and inhibition of this active site in the enzyme (60). The biologically relevant aspects of these complexes were the subject of many reports (61,62). Our interest is in describing their crystal structure, which will be correlated to the magnetic properties in a later section. [Pg.170]

Tyrosinase (see Copper Proteins with Dinuclear Active Sites), a copper metalloenzyme with a very broad phylogenetic distribution, is responsible for the browning of fruits and mushrooms.Tyrosinase is a bifimctional phenol oxidase that is able to both hydroxylate monophenols like tyrosine (monooxygenase reaction, (equations)) and snbseqnently oxidize the diphenol product to the corresponding quinone (oxidase reaction, (equation 6)) at a single Type 3 binuclear copper active site. [Pg.5498]

Dioxygen activation is also accomplished at the dinuclear copper-active sites in tyrosinases and catechol oxidases. Tyrosinases (EC 1.14.18.1) are widely distributed throughout bacteria, fungi, plants, and animals, catalyzing the ortho-hydroxylation of phenols to catechols (phenolase activity. Equation (1)) and the oxidation of catechols to o-quinones (catecholase activity. Equation (2)). [Pg.369]

In this chapter, the dioxygen activation mechanism at the dinuclear copper-active sites of tyrosinase and catechol oxidase has been surveyed. In both enzymes, a (ji-rfirf -peToxo) dicopper(II) complex has been detected and characterized as a common reactive intermediate by several spectroscopic methods. In spite of longstanding efforts in the enzymological studies, mechanistic details of the enzymatic reactions (phenolase and catecholase activities) still remain ambiguous. On the other hand, recent developments in the model chemistry have provided a great deal of information about the structure and physicochemical properties as well as the reactivity of the peroxo intermediate and have advanced our understanding of the enzymatic reactions. [Pg.389]

Oxidative transformations carried out by the reaction of copper(I) and O2 in Nature are widespread in terms of the variety of substrates and in copper active-site structures. The archetype for dicopper-dioxygen activation has been the dioxygen carrier for arthropods and mollusks, hemocyanin (He), which has a dinuclear copper(I) active site where the copper centers are ca. [Pg.132]

X-ray analysis of both copper(I) (e.g. 9) and copper(II) complexes, independent synthesis, and ammonolysis to the free ligands 35 and 36, confirmed the hydroxylation pathway.42 02-binding and hydroxylation in complex 10 were shown to be sensitive to electronic effects of the para-substituent (X = OMe, Me, C02Me, N02>. Tyrosinase, which contains a dinuclear copper active site strongly resembling the hemocyanine active site, binds O2 reversibly and activates O2 for arene hydroxylation (stoichiometry Cu O2 = 2 These are key features observed in the dinuclear copper complexes shown in... [Pg.178]


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See also in sourсe #XX -- [ Pg.362 , Pg.363 , Pg.364 , Pg.365 , Pg.366 ]




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