Vanadate ion

Goodno, C.C. (1979). Inhibition of myosin ATPase by vanadate ion. Proc. Natl. Acad. Sci. USA 76, 2620-2624. 

Draw the structures for the ortho, pyro, and meta vanadate ions and give equations showing how they can be interconverted. 

It has been suggested that an increase in the coordination number of vanadium from 4 to 5 already takes place in the second protonation step, i.e. when [H2V04] is formed (21). For reactions (1) and (2), however, the protonation constants and thermodynamic parameters are comparable with those reported for P04 and As04 , providing firm evidence that reaction (2) is not accompanied by incorporation of water in the vanadate ion (15, 17). Further, the estimated thermodynamic quantities for reaction (6), AH° = -39 kJ/mol and AS0 = —51 J/(mol K), obtained by extrapolation from the experimental values for reactions (1) and (2) and those for the three protonation steps of P04 and As04 , are not typical of a simple protonation reaction (17). For such a reaction the entropy change is normally a positive quantity often amounting to 100 50 J/(mol K) and the enthalpy... 

Vibrational spectra of some vanadate salts " and several mineral species containing condensed vanadate ions have been reported. 

This enzyme [EC 3.4.21.53], also known as endopepti-dase La, ATP-dependent serine proteinase, and ATP-dependent protease La, catalyzes the hydrolysis of peptide bonds in large proteins (for example, globin, casein, and denaturated serum albumin) in the presence of ATP (which is hydrolyzed to ADP and orthophosphate). Vanadate ion inhibits both reactions. A similar enzyme occurs in animal mitochondria. Protease La belongs to the peptidase family S16. 

HOST-GUEST INTERACTIONS VANADATE ION IONIC RADIUS... 

A triple complex is formed between V-(a-pyridyl)-2-thioquinaldamide (120), vanadate ions and H2O2 that becomes fluorescent in acidic solution (Aex = 340 nm, An = 490 nm). This reaction, originally developed for determination of V(V) in a FIA system, can be adapted for determination of H2O2 and organic peroxides. LOD for H2O2 is 0.05 p,M, with RSD 2.4% (ri = 3) at 1 p,M, with linearity in the 0.2 to 50 p,M range330. 

A systematic study to identify solid oxide catalysts for the oxidation of methane to methanol resulted in the development of a Ga203—M0O3 mixed metal oxide catalyst showing an increased methanol yield compared with the homogeneous gas-phase reaction.1080,1081 Fe-ZSM-5 after proper activation (pretreatment under vacuum at 800-900°C and activation with N20 at 250°C) shows high activity in the formation of methanol at 20°C.1082 Density functional theory studies were conducted for the reaction pathway of the methane to methanol conversion by first-row transition-metal monoxide cations (MO+).1083 These are key to the mechanistic aspects in methane hydroxylation, and CuO+ was found to be a likely excellent mediator for the reaction. A mixture of vanadate ions and pyrazine-2-carboxylic acid efficiently catalyzes the oxidation of methane with 02 and H202 to give methyl hydroperoxide and, as consecutive products, methanol and formaldehyde.1084 1085... 

Other metals such as vanadium have more complicated chemistry. The vanadate ion, VO4-. exists in extremely basic solution (Fig. 16.9). Under very dilute conditions as the pH is lowered, protonation occurs to give monomers ... 

These P-type ATPases are characterized by phosphoenzyme intermediates, by a conserved consensus sequence, and through inhibition by vanadate ion.537-539 The structures are poorly known. Some consist of single chains (perhaps dimerized) and some have more than one chain. However, the major subunit always appears to have about ten transmembrane helices with a large 430-residue cytoplasmic domain between the fourth and fifth helices. This domain contains the ATP binding site and the phosphoaspartyl group of the phosphoenzyme.534 This is Asp 369 for the Na+,K+- ATPase. 

Much of current interest in vanadium stems from the discovery that vanadate (HV042 at pH 7) is a powerful inhibitor of ATPases such as the sodium pump protein (Na+ + K+)ATPase (Chapter 8), of phosphatases,623 and of kinases.624 This can be readily understood from comparison of the structure of phosphate and vanadate ions. 

Vanadate ion and the ligand tricine form a complex in aqueous solution ... 

Vanadic ion, forms green salts and is a good reducing... 

Fig. 2 Three-dimensional representation of the active site of rat prostatic acid phosphatase complexed with transition-state analogue vanadate ion (1rpt). Based on Lindqvist et al. [4]...

Since disturbed acid phosphatase activity has been associated with pathological conditions, the research has focused on the development of diagnostic methods for detection of activity as a marker for the onset of the disease, and in some extent to the development of inhibitors rather than activators to treat those conditions in which the increase in enzyme activity has a direct effect on the evolution of the disease. In particular, only the development of bisphospho-nate derivatives as inhibitors for tartrate-resistant acid phosphatase found their way to the market for treatment of osteoporosis [41], Typical inhibition of phosphatase activity includes anionic species such as L-(+)-tartrate, phosphate, vanadate, molybdate, and fluoride and neutral molecules such as formaldehyde. Vanadate ion,, is a competitive unspecific inhibitor for acid phosphatases by forming transition state analogs. Other oxoanions such as molybdate and tungstate also show inhibitory effects on... 

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