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Molybdenum (Mo) is an important trace element that is toxic at high concentrations. To resolve the mechanisms underlying Mo toxicity, Rhodobacter capsulatus mutants tolerant to high Mo concentrations were isolated by random transposon Tn5 mutagenesis. The insertion sites of six independent isolates mapped within the same gene predicted to code for a permease of unknown function located in the cytoplasmic membrane. During growth under Mo-replete conditions, the wild-type strain accumulated considerably more Mo than the permease mutant. For mutants defective for the permease, the high-affinity molybdate importer ModABC, or both transporters, in vivo Mo-dependent nitrogenase (Mo-nitrogenase) activities at different Mo concentrations suggested that ModABC and the permease import molybdate in nanomolar and micromolar ranges, respectively. Like the permease mutants, a mutant defective for ATP sulfurylase tolerated high Mo concentrations, suggesting that ATP sulfurylase is the main target of Mo inhibition in R. capsulatus. Sulfate-dependent growth of a double mutant defective for the permease and the high-affinity sulfate importer CysTWA was reduced compared to those of the single mutants, implying that the permease plays an important role in sulfate uptake. In addition, permease mutants tolerated higher tungstate and vanadate concentrations than the wild type, suggesting that the permease acts as a general oxyanion importer. We propose to call this permease PerO (for oxyanion permease). It is the first reported bacterial molybdate transporter outside the ABC transporter family. doi: 10.1128/JB.00742-10

The hyperthermophilic archaeon Pyrococcusfuriosus expresses five aldehyde oxidoreductase (AOR) enzymes, all containing a tungsto-bispterin cofactor. The growth of this organism is fully dependent on the presence of tungsten in the growth medium. Previous studies have suggested that molybdenum is not incorporated in the active site of these enzymes. Application of the radioisotope [sup.99]Mo in metal isotope native radioautography in gel electrophoresis (MIRAGE) technology to P. furiosus shows that molybdenum can in fact be incorporated in all five AOR enzymes. Mo(V) signals characteristic for molybdopterin were observed in formaldehyde oxidoreductase (FOR) in electron paramagnetic resonance (EPR)-monitored redox titrations. Our finding that the aldehyde oxidation activity of FOR and WOR5 (W-containing oxidoreductase 5) correlates only with the residual tungsten content suggests that the Mo-containing AORs are most likely inactive. An observed W/Mo antagonism is indicative of tungstate-dependent negative feedback of the expression of the tungstate/molybdate ABC transporter. An intracellular selection mechanism for tungstate and molybdate processing has to be present, since tungsten was found to be preferentially incorporated into the AORs even under conditions with comparable intracellular concentrations of tungstate and molybdate. Under the employed growth conditions of starch as the main carbon source in a rich medium, no tungsten- and/or molybdenum-associated proteins are detected in P. furiosus other than the high-affinity transporter, the proteins of the metallopterin insertion machinery, and the five W-AORs. doi: 10.1128/JB.00270-10

Molybdenum (Mo) is a trace element essential for living organisms, however no molybdate transporter has been identified in eukaryotes. Here, we report the identification of a molybdate transporter, MOT1, from Arabidopsis thaliana. MOT1 is expressed in both roots and shoots, and the MOT1 protein is localized, in part, to plasma membranes and to vesicles. MOT1 is required for efficient uptake and translocation of molybdate and for normal growth under conditions of limited molybdate supply. Kinetics studies in yeast revealed that the [K.sub.m] value of MOT1 for molybdate is [approximately equal to] 20 nM. Furthermore, Mo uptake by MOT1 in yeast was not affected by coexistent sulfate, and MOT1 did not complement a sulfate transporter-deficient yeast mutant strain. These data confirmed that MOT1 is specific for molybdate and that the high affinity of MOT1 allows plants to obtain scarce Mo from soil. molybdenum | nutrition

A recombinant-expression cassette is constructed for the gene MOCS1 which via alternative splicing, facilitates the expression of the proteins MOCS1A and MOCS1B, both of which are necessary for the formation of a first intermediate, cyclic pyranopterin monophosphate within the biosynthetic pathway leading to active molybdenum cofactor (MoCo). A recombinant adeno-associated virus vector is used to express the artificial MOCS1 minigene to cure the lethal MOCS1-deficient phenotype.

In most bacteria, nitrogen metabolism is tightly regulated and P11 proteins play a pivotal role in the regulatory processes. Rhodobacter capsulatus possesses two genes (glnB and glnK) encoding P11-like proteins. The glnB gene forms part of a glnB-glnA operon and the glnK gene is located immediately upstream of amtB, encoding a (methyl-) ammonium transporter. Expression of glnK is activated by NtrC under nitrogen-limiting conditions. The synthesis and activity of the molybdenum and iron nitrogenases of R. capsulatus are regulated by ammonium on at least three levels, including the transcriptional activation of nifA1, nifA2 and anfA by NtrC, the regulation of NifA and AnfA activity by two different NtrC-independent mechanisms, and the post-translational control of the activity of both nitrogenases by reversible ADP-ribosylation of NifH and AnfH as well as by ADP-ribosylation independent switch-off. Mutational analysis revealed that both P11-like proteins are involved in the ammonium regulation of the two nitrogenase systems. A mutation in glnB results in the constitutive expression of nifA and anfA. In addition, the post-translational ammonium inhibition of NifA activity is completely abolished in a glnB-glnK double mutant. However, AnfA activity was still suppressed by ammonium in the glnB-glnK double mutant. Furthermore, the [P.sub.II]-like proteins are involved in ammonium control of nitrogenase activity via ADP-ribosylation and the switch-off response. Remarkably, in the glnB-glnK double mutant, all three levels of the ammonium regulation of the molybdenum (but not of the alternative) nitrogenase are completely circumvented, resulting in the synthesis of active molybdenum nitrogenase even in the presence of high concentrations of ammonium.

Research has been conducted on the inorganic oxyfluoride chains. The hydrogen bonding occurring between these chains and the role of the racemic (inversion) twin formation have been investigated and the details are reported.

Research has been conducted on the transition metal half-sandwich complexes with 1,1-dichalcogenolate ligands. The preparation of these complexes via the reactions of Cp*MCl (sub)4, where Cp*= eta (super)5 -C (sub)5 Me (sub)5 and M= Mo, W, with the potassium salt or the analogous seleno compound is described.

Research has been conducted on the RMo (sub)8 O (sub)14 compounds (R= La, Ce, Pr, Nd, Sm) compounds which contain bicapped-octahedral Mo (sub)8 clusters. The magnetic and electronic properties of these compounds have been investigated and the density functional calculation results indicate that these compounds are of the molecular character.

Research has been conducted on the homologous tungsten(VI) derivatives. The reactivity, epoxidation mechanism and applicability of these compounds have been investigated and compared to those of the molybdenum(VI) compounds and the details are presented.

Research has been conducted on the bis(hydrosulfido) complexes. The reactions of these complexes with [nu (super)5 -C (sub)5 H (sub)5 TiCl (sub)3 and [TiCl (sub)4 (thf) (sub)2] in the presence of thriethylamine have formed sulfido-bridged titanium-rhodium complexes.

Research has been conducted on the (Bu (super)n (sub)4 N) (sub)2 H (sub)2{Mo (sub)2[Mo(CO) (sub)4 (PhPO (sub)2) (sub)2](sub)2}. The study of this compound has been carried out and the results indicate that hydrogen atoms are not present in in this formula.

Research has been conducted on the reactions of M (sub)4 (SPh) (sub)10] (super)2- (M=Fe or Co) with PhS (super)-. The kinetic studies of this reaction carried out via the use of the stopped-flow spectrophotometry are discussed.

Research has been conducted on the (eta (super)3 -allyl)molybdenum complexes. Results indicate that oxidative demetalation of these complexes carried out via the use of pyridinium dichromate leads to the carbonyl group introduction at the allylic terminus of the pi-system.

Research has been conducted on Mo (sub)7 O (sub)16 (O (sub)3 PCH (sub)2 PO (sub)3) (sub)3] (super)8- compounds with diphosphono-polyoxometalate anions and diprotonated ethylenediamine and piperazine countercations. The hydrothermal synthesis of these compounds has been carried out and the results indicate that the compounds are diamagnetic.

Research has been conducted on the cyclopentene. The results of the oxidative carbomethoxylation of this compound carried out under air and carbon monoxide via the use of catalytic amount of Pd(OAc) (sub)2 and molybdovanadophosphate are presented.

Research has been conducted on the diaonic molybdenacarborane. The preparation of this compound has been carried out and the results indicate that it is readily oxidized by cage-carbon to cage-boron transfer of NMe (sub)3 group.

Research has been conducted on the high-nuclearity molybdenum-iron-sulfur clusters. The synthesis and properties of these clusters have been reexamined and substantial differences have been discovered.

Research has been conducted on molybdenum oxides. The synthesis of these oxides as crystalline powders has been carried out via the solid-state reaction in a sealed molybdenum crucible and the results indicate that their crystal structure is based on the trans-edge-shared molybdenum octahedra's infinite chains.

Research has been conducted on the carbonates and trichlorobenzoate. The metal-catalyzed allylic substitution reaction of these compounds has been investigated and the metal complexes which contain iridium, palladium, tungsten, rhodium and molybdenum have been compared as catalysts.

Research has been conducted on the uncharged bridged double cubane clusters. The synthesis and characterization of these clusters have been carried out and the details are described.

Research has been conducted on the hydrothermal reaction of MoO (sub)3 with BaH (sub)3 IO (sub)6 resulting in the formation of Ba[(MoO (sub)2) (sub)6 (IO (sub)4) (sub)2 O (sub)4].H (sub)2 O. Results indicate that under similar conditions Ba (sub)3[(MoO (sub)2) (sub)2 (IO (sub)6) (sub)2].2H (sub)2 O can be produced from the reaction of Ba(OH) (sub)2 .8H (sub)2 O with MoO (sub)3.

Research has been conducted on the iron sulfur clusters. The results of the Mossbauer investigation of the high-spin ferrous complexes with the extracted zero-field splittings, electric field gradient tensors, A-tensors and isomer shifts are presented.

Research has been conducted on the molubdenum complexes, important for the carbon, sulfur and nitrogen metabolism. The use of electrochemistry and photoelectron spectroscopy in investigating these complexes is described.

Research has been conducted on the molybdenum to molybdenum quadruple bonds. The deviations of the bonds' lengths from the main body of results has been investigated and the details are presented.

Research has been conducted on the racemic branched carbonates. The results of the catalytic asymmetric alkylation reactions of these carbonates with sodium dimethyl malonate carried out in such solvents as toluene, tetrahydrofuran and tetrahydropyran are discussed.

Research has been conducted on the fullerene-like nanoparticles. The nanoparticles have been intercalated via the alkali metal vapor exposure by the two-zone transport method and the details are reported.

Research has been conducted on the metal-metal multiply bonded complexes. The third-order nonlinear optical responses of complexes' solutions have been measured via the picosecond degenerate four-wave mixing and the details are reported.

Research has been conducted on the niobium, tantalum, molybdenum and tungsten isopolyanions. The structure and bonding of these isopolyanions have been investigated via the use of density functional methods and the details are presented.

Research has been conducted heterometal clusters with cubane-type core. The preparation of these cluster containing [VFe (sub)3 S (sub)4] (super)2+ and [MoFe (sub)3 S (sub)4] (super)3+,2+ is described.

Research has been conducted on molecular nitrogen. The reaction of a nucleophilic molybdenum(VI) nitride with the electrophilic osmium(VI) nitride has been studied and the results indicate that the coupling reaction produces a heterobimetallic mu-nitrido complex.

Research has been conducted on the heteroatomic closo-[1-M(CO) (sub)3 (nu (super)4 -E (sub)9)] (super)4- (E= Sn, Pb; M= Mo, W) anions. The crystal structures of these anions and solution characterization of the [1-M(CO) (sub)3 (nu (super)4 -Sn (sub)9)] (super)4- (M= Cr, Mo, W) anions have been investigated and the results of the NMR spectroscopy analysis of the anions are presented.

Research has been conducted on the complexes containing functionalized cycloheptatrienyl ligands. The syntheses of the molybdenum complexes which contain linked cycloheptatrienyl-phenolate ligands capable to bind to the metal center are reported.

Research has been conducted on the Cs (sub)2 (UO (sub)2) (sub)2 (MoO (sub)4) (sub)3 polymorphs. The synthesis of these polymorphs has been carried out via the hydrothermal and high-temperature routes and the results of the single-crystal X-ray diffraction analysis are reported.

Research has been conducted on the molybdenum(IV) fragment [Mo(S (sub)2 CNR (sub)2) (sub)6] (super)+ where R= Et and Me. Results indicate that this cation is unstable as a monomer and dimerizes to form metal-metal-bonded dimers [Mo (sub)2 (S (sub)2 CNR (sub)2) (sub)6](OTf) (sub)2.

Research has been conducted on the mercury-containing purple corner-shared [Mo (sub)6 HgS (sub)8 (H (sub)2 O) (sub)18] (super)8+ double cube derivative of green [Mo (sub)3 S (sub)4 (H (sub)2 O) (sub)9] (super)4+. The preparation of this derivative under the air-free conditions via the reaction with Hg (super)0 and with Hg (super)I (sub)2 is described.

Research has been conducted on the metallacarnoranes. The preparation of the metal complexes demonstrating the aminocarborane ligand versatility has been carried out and investigated and the results are described.

Research has been conducted on the transition metal tris(dithiolene) complexes. The synthesis and structural characterization of (Bu (super)n (sub)4 N)[Mo(1,2-benzenedithiolate) (sub)3] have been explored and the results are discussed.

Research has been conducted on the substitution inert trans-[Os(en) (sub)2 O (sub)2] (super)2+ which is reluctant to undergo oxidation or reduction reaction with regular reagents. The primary photolysis product identification of [Mo(CN) (sub)8] (super) 4- via the lower energy photons has been performed and the use of [Mo(CN) (sub)8] (super) 4- as a crystallizing agent for [Os(en) (sub)2 O (sub)2] (super)2+ is discussed.

Research has been conducted on the compounds with the metal-metal bonded Mo (sub)2 (super)4+ and Rh (sub)2 (super)4+ units. The description of these compounds with the units the midpoints of which occupy the vertexes of an octahedron is reported and the results of their study indicate that these units are linked together by the trimesic acid tricarboxylate anions.

Research has been conducted on the allylic sulfides which contain high electron density double bonds. The chemoselective sulfur oxidation of these sulfides has been developed via the use of the composite metal oxide catalyst LiNbMoO (sub)6 without electron-rich double bond epoxidation and the results are presented.