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The conditions for formation of individual isopolytungstates in solutions of the Sr(NO3)2-Na2WO4-HNO3-H2O system acidified to Z = ν(H+)/ν(WO) = 1.29 were studied. The conditions of formation of strontium paratungstate B, strontium hydroheptatungstate, and hydrogen strontium paratungstate were determined. An X-ray diffraction study of single crystals of Sr4.5H[W12O40(OH)2] · 30H2O was carried out. Selected crystallographic data for H63O72Sr4.50W12 are: M r = 3815.99, monoclinic, space group P21/ c, a = 11.41270(10) Å, b = 23.7575(3) Å, c = 12.4392(2) Å, β = 110.476(2)°, V = 3159.64(7) Å3 at T = 293 K, Z = 2, ρ = 4.011 g/cm3, F000 = 3396, μ(Mo Kα) = 25.635 mm−1, −14 ≤ h ≤ 14, −30 ≤ k ≤ 30, −16 ≤ l ≤ 16, RF = 0.0430, wR2 = 0.1067 ( RF = 0.0506, wR2 = 0.1129), and S = 1.043. [ABSTRACT FROM AUTHOR]

The green crystals of Ni1.5H[Ni(OH)6W6O18]·12.5H2O and blue crystals of Na4[Ni(OH)6W6O18]·16H2O were isolated from the acidified (to Z = ν(H+)/ν(WO) = 1.00) solutions of Ni(NO3)2-Na2WO4-HNO3-H2O systems. The synthesized salts were identified by chemical analysis, XRPA, and IR spectroscopy. It was shown that the heteropolyanions belonged to the Anderson-Evans type of structure. An X-ray diffraction study of Na4[Ni(OH)6W6O18]·16H2O was carried out ( Mr = 1932.07, triclinic, space group P-1, a = 8.0089(11) Å, b = 10.5758(14) Å, c = 12.1987(16) Å; α = 69.268(13)°, β = 71.069(12)°, γ = 83.816(11)°; V = 914.0(2) Å3 at T = 293 K, Z = 1, ρcal = 3.510 g/cm3, F000 = 874, μ = 19.470 mm−1, −16 ≤ h ≤ 16, −21 ≤ k ≤ 21, −24 ≤ l ≤ 24; the final R factors are RF = 0.0277, wR2 = 0.0469 for the observed reflections ( RF = 0.0606, wR2 = 0.0523 for all independent reflections); S = 0.953; CSD-419883). The structure was solved by direct methods and refined in an anisotropic approximation. Hydrogen atoms were found in a difference synthesis and refined in an isotropic approximation with geometrical limitations. The nature of water in Na4[Ni(OH)6W6O18]·16H2O was characterized by DTA. XRPA was used to identify the thermolysis products of heteropoly compounds. [ABSTRACT FROM AUTHOR]

Inorganic systems based upon polyoxometalate (POM) clusters provide an experimental approach to develop artificial life. These artificial symmetric anionic macromolecules with oxidometalate polyhedra as building blocks were shown to be well suited as inorganic frameworks for complex self-assembling and organizing systems with emergent properties. Analogously to mineral cells based on iron sulfides, POMs are considered as inorganic cells in facilitating prelife chemical processes and displaying "life-like" characteristics. However, the relevance of POMs to life-sustaining processes (e.g., microbial respiration) has not yet been addressed, while iron sulfides are very well known as ubiquitous mineral precursors and energy sources for chemolithotrophic metabolism. Metallosphaera sedula is an extreme metallophilic and thermoacidophilic archaeon, which flourishes in hot acid and respires by metal oxidation. In the present study we provide our observations on M. sedula cultivated on tungsten polyoxometalate (W-POM). The decomposition of W-POM macromolecular clusters and the appearance of low molecular weight W species (e.g., WO) in the presence of M. sedula have been detected by electrospray ionization mass spectrometry (ESI-MS) analysis. Here, we document the presence of metalloorganic assemblages at the interface between M. sedula and W-POM resolved down to the nanometer scale using scanning and transmission electron microscopy (SEM and TEM) coupled to electron energy loss spectroscopy (EELS). High-resolution TEM (HR-TEM) and selected-area electron diffraction (SAED) patterns indicated the deposition of redox heterogeneous tungsten species on the S-layer of M. sedula along with the accumulation of intracellular tungsten-bearing nanoparticles, i.e., clusters of tungsten atoms. These results reveal the effectiveness of the analytical spectroscopy coupled to the wet chemistry approach as a tool in the analysis of metal-microbial interactions and microbial cultivation on supramolecular self-assemblages based on inorganic metal clusters. We discuss the possible mechanism of W-POM decomposition by M. sedula in light of unique electrochemical properties of POMs. The findings presented herein highlight unique metallophilicity in hostile environments, extending our knowledge of the relevance of POMs to life-sustaining processes, understanding of the transition of POMs as inorganic prebiotic model to life-sustainable material precursors and revealing biogenic signatures obtained after the decomposition of an artificial inorganic compound, which previously was not associated with any living matter.

Polyoxometalates (POMs) are transition metal complexes that exhibit a broad diversity of structures and properties rendering them promising for biological purposes. POMs are able to inhibit a series of biologically important enzymes, including phosphatases, and thus are able to affect many biochemical processes. In the present study, we analyzed and compared the inhibitory effects of nine different polyoxotungstates (POTs) on two P-type ATPases, Ca 2+ -ATPase from skeletal muscle and Na + /K + -ATPase from basal membrane of skin epithelia. For Ca 2+ -ATPase inhibition, an in vitro study was performed and the strongest inhibitors were determined to be the large heteropolytungstate K 9 (C 2 H 8 N) 5 [H 10 Se 2 W 29 O 103 ] (Se 2 W 29 ) and the Dawson-type POT K 6 [α-P 2 W 18 O 62 ] (P 2 W 18 ) exhibiting IC 50 values of 0.3 and 0.6 μM, respectively. Promising results were also shown for the Keggin-based POTs K 6 H 2 [CoW 11 TiO 40 ] (CoW 11 Ti, IC 50 = 4 μM) and Na 10 [α-SiW 9 O 34 ] (SiW 9 , IC 50 = 16 μM), K 14 [As 2 W 19 O 67 (H 2 O)] (As 2 W 19 , IC 50 = 28 μM) and the lacunary Dawson K 12 [α-H 2 P 2 W 12 O 48 ] (P 2 W 12 , IC 50 = 11 μM), whereas low inhibitory potencies were observed for the isopolytungstate Na 12 [H 4 W 22 O 74 ] (W 22 , IC 50 = 68 μM) and the Anderson-type Na 6 [TeW 6 O 24 ] (TeW 6 , IC 50 = 200 μM). Regarding the inhibition of Na + /K + -ATPase activity, for the first time an ex vivo study was conducted using the opercular epithelium of killifish in order to investigate the effects of POTs on the epithelial chloride secretion. Interestingly, 1 μM of the most potent Ca 2+ -ATPase inhibitor, Se 2 W 29 , showed only a minor inhibitory effect (14% inhibition) on Na + /K + -ATPase activity, whereas almost total inhibition (99% inhibition) was achieved using P 2 W 18 . The remaining POTs exhibited similar inhibition rates on both ATPases. These results reveal the high potential of some POTs to act as P-type ATPase inhibitors, with Se 2 W 29 showing high selectivity towards Ca 2+ -ATPase.