Binding vanadium oxides

Because of the intensity of Mzp peaks, which is much lower than that of the nearby Ois peak, the vanadium oxidation state could be reliably ascertained only for ZV(a) and ZV(i) specimens with a V loading > 1% (2.5 atom nm 2). The binding energy value of the Vzpjyg component, obtained by curve fitting of the region Ois-V2p,... 

GSH has been proposed to be part of the thiol cycling in mammalian cells that may transduce oxidative stress redox signaling into the induction of many genes involved in proliferation, differentiation, and apoptosis [15], Studies with pure chemical systems have confirmed the reduction of V(V) maltol compounds by GSH or ascorbic acid [16], Putative glutathione transferase enzymes that bind vanadium have been isolated from an ascidian that accumulates vanadium in specialized cells to over 350 mM [17],... 

Figure 13 shows the activity, the binding energy of the V line, and the FWHM as a function of the composition. The following statements can be made i) at a high vanadium oxide content the activity is relatively low and the surface composition is close to... 

Insulin binding to the extracellular side of cell membranes initiates the insulin cascade , a series of phosphorylation/dephosphorylation steps. A postulated mechanism for vanadium is substitution of vanadate for phosphate in the transition state structure of protein tyrosine phosphatases (PTP).267,268 In normal physiological conditions, the attainable oxidation states of vanadium are V111, Viv and Vv. Relevant species in solution are vanadate, (a mixture of HV042-/ H2VOO and vanadyl V02+. Vanadyl is not a strong inhibitor of PTPs, suggesting other potential mechanisms for insulin mimesis for this cation. 

Alkyl hydroperoxides, including ethyl hydroperoxide, cuminyl hydroperoxide, and tert-butyl hydroperoxide, are not used by V-BrPO to catalyze bromination reactions [29], These alkyl hydroperoxides have the thermodynamic driving force to oxidize bromide however, they are kinetically slow. Several examples of vanadium(V) alkyl peroxide complexes have been well characterized [63], including [V(v)0(OOR)(oxo-2-oxidophenyl) salicylidenaminato] (R = i-Bu, CMe2Ph), which has been used in the selective oxidation of olefins to epoxides. The synthesis of these compounds seems to require elevated temperatures, and their oxidation under catalytic conditions has not been reported. We have found that alkyl hydroperoxides do not coordinate to vanadate in aqueous solution at neutral pH, conditions under which dihydrogen peroxide readily coordinates to vanadate and vanadium( V) complexes (de la Rosa and Butler, unpublished observations). Thus, the lack of bromoperoxidase reactivity with the alkyl hydroperoxides may arise from slow binding of the alkyl hydroperoxides to V-BrPO. 

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