A procedure was developed that allows precise determination of molybdenum isotope abundances in natural samples. Purification of molybdenum was first achieved by solvent extraction using di(2-ethylhexyl) phosphate. Further separation of molybdenum from isobar nuclides was obtained by ion chromatography using AG1-X8 strongly basic anion exchanger. Finally, molybdenum isotopic composition was mea...

In Methanobacterium wolfei two formylmethanofuran dehydrogenases are present, one of which is a molybdenum- and the other a tungsten enzyme. We report here that also the 'molybdenum' enzyme contained tungsten when the archaeon was grown on molybdenum-deprived medium supplemented with tungstate (1 microM). Unexpectedly the tungsten-substituted molybdenum enzyme was catalytically active and displ...

A series of molybdenum(VI) complexes containing bidentate ligands: toluene-3,4-dithiol (1), 2-mercaptophenol (2), 2-aminothiophenol (3), ethane-1,2-dithiol (4), dithiooxamide (5) and 2-thiopheno-carboxamide (6) are reported. The hexacoordinated molybdenum tris-chelates compounds: tris-(toluene-3, 4-dithiolate)molybdenum(VI) (7), tris-(2-mercaptophenolate)molybdenum(VI) (8), tris-(2-aminothiophe...

Klebsiella pneumoniae accumulates molybdenum during nitrogenase derepression. The molybdenum is primarily in nitrogenase component I in the form of iron-molybdenum cofactor (FeMo-co). Mutations in any of three genes (nifB, nifN, and nifE) involved in the biosynthesis of FeMo-co resulted in very low molybdenum accumulation and in a molybdenum-free nitrogenase component I. A mutant lacking both s...

A combination of SEM, AES and angle-resolved XPS (ARXPS) has been applied to analyse the distribution of chemical compounds in the surface region of electrochemically etched molybdenum tips and to determine the contamination layer thickness. Carbon monoxide, graphite, molybdenum carbide and molybdenum oxide were found to be the main surface contaminants on molybdenum tips. Auger line profiling ...

I . The oral administration of sodium molybdate caused a rapid rise of molybdenum in the milk of cows and goats fed on a low-molybdenum diet, but did not affect the xanthine oxidase activities of the milk of either species. 2. In the milks of cows not dosed with sodium molybdate, the regression of the xanthine oxidase activity ( y ) on the molybdenum content (x) was found to be (r = +0.9386; P ...

The reduction mechanism of molybdenum-methyl thymol blue (MTB)-chlorate system has been investigated in water on a mercury electrode. As this system is very sensitive for ultratrace determination of molybdenum, the actual mechanism involved was studied. Electrochemical techniques, including dc tast polarography and cyclic voltammetry were employed. It is shown that, the cathodic wave of mol...

There are many molybdenum-containing enzymes distributed throughout the biosphere. The availability of molybdenum to biological systems is due to the high water solubility of oxidized forms of the metal. Molybdenum enzymes can be grouped on the basis of the structure of the metal centre. Three principal families of enzyme exist, with active sites consisting of (ppt)MoOS(OH) (the molybdenum hydr...