The P-type ATPase inhibiting potential of polyoxotungstates.

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, Ca2+-ATPase from skeletal muscle and Na+/K+-ATPase from basal membrane of skin epithelia. For Ca2+-ATPase inhibition, an in vitro study was performed and the strongest inhibitors were determined to be the large heteropolytungstate K9(C2H8N)5[H10Se2W29O103] (Se2W29) and the Dawson-type POT K6[α-P2W18O62] (P2W18) exhibiting IC50 values of 0.3 and 0.6 μM, respectively. Promising results were also shown for the Keggin-based POTs K6H2[CoW11TiO40] (CoW11Ti, IC50 = 4 μM) and Na10[α-SiW9O34] (SiW9, IC50 = 16 μM), K14[As2W19O67(H2O)] (As2W19, IC50 = 28 μM) and the lacunary Dawson K12[α-H2P2W12O48] (P2W12, IC50 = 11 μM), whereas low inhibitory potencies were observed for the isopolytungstate Na12[H4W22O74] (W22, IC50 = 68 μM) and the Anderson-type Na6[TeW6O24] (TeW6, IC50 = 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 Ca2+-ATPase inhibitor, Se2W29, showed only a minor inhibitory effect (14% inhibition) on Na+/K+-ATPase activity, whereas almost total inhibition (99% inhibition) was achieved using P2W18. 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 Se2W29 showing high selectivity towards Ca2+-ATPase.info:eu-repo/semantics/submittedVersio

Synthesis, characterization, and POM-protein interactions of a Fe-substituted Krebs-type Sandwich-tungstoantimonate

The novel iron-substituted Krebs-type polyoxotungstate (C12N4H11)4Na2H5[(Fe(H2O)3)2((FeO2)0.5(WO2)0.5)2(β-SbW9O33)2] (Fe-1) has been synthesized using ortho-phenylenediamine (opda) as a precursor for the in situ formation of the counter cation 2,3-diaminophenazinium (C12N4H11)+ (2,3-DAP). Fe-1 has been thoroughly characterized in the solid state by single-crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), IR spectroscopy, and elemental analysis as well as in solution by UV–Vis spectroscopy. The crystal structure of Fe-1 reveals π–π-interactions between the aromatic systems of the unconventional 2,3-DAP counter cation. POM-protein interaction studies using SDS-PAGE revealed a non-proteolytic behavior of Fe-1 towards Human Serum Albumin (HSA) as a model protein.© The Author(s) 201

Synthesis of the first Zn6-hexagon sandwich-tungstoantimonate via rearrangement of a non-lacunary Krebs-type polyoxotungstate

A novel synthetic pathway to obtain the first Zn6 hexagon tungstoantimonate [(Zn(H2O))6(B-α-SbW9O33)2]6− ([Zn6-α-SbW9] (1)) via rearrangement of a non-lacunary Krebs-POM precursor (C12N4H11)4K4[(Mn(H2O)3)2((Mn0.5W0.5)O2)2(B-β-SbW9O33)2] ([Mn-β-SbW9]) has been developed. Addition of ortho-phenylenediamine (opda) in order to optimize the synthesis of [Mn-β-SbW9] led to the crystallization of a novel Krebs-type Zn-POM (C12N4H11)4Na5[((Zn0.8W0.2)(H2O)3)2((Zn0.2W0.8)O2)2(B-β-SbW9O33)2] ([(Zn/W)2-β-SbW9] (2)) comprising four disordered Zn-centers after replacement of MnCl2 with ZnCl2. The compounds were characterized in the solid state by single-crystal and powder X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and elemental analysis and in solution by UV-vis spectroscopy and ESI-mass spectrometry. The Krebs-POM archetype and the Zn6 hexagon tungstoantimonate have been investigated towards their interactions with Human Serum Albumin (HSA) as a model protein using SDS-PAGE and trypthophan fluorescence quenching