Keggin Structure, Quō Vādis?

Working under the supervisor of William Lawrence Bragg at the University of Manchester and being under the direct personal and scientific influence by Linus Pauling, Dr. James Fargher Keggin some 85 years ago published a highly unique discovery—the structure of phosphotungstic acid (Nature 1933, 131, 908–909). This structure sparked the reports of other related polyanions from Keggin's contemporaries, marking the true beginnings of structural polyoxometalate chemistry. In this perspective article, we unveil some aspects and applications of Keggin's structure and discuss how it has shaped the course of our understanding of polyoxometalate chemistry and nanomolecular metal oxides/hydroxides in general

Enzymes as a platform for drug development

Polyoxometalates are negatively charged polyanions containing early transition metal ions in their high oxidation state surrounded by bridged oxygen. Firstly, these metal-based clusters were used as promising agents in electron-dense imaging, separations, catalysis, and analysis. In recent years, numerous studies in vitro and in vivo found that these nanocomplexes possess a variety of biological effects including antidiabetic, anticancer, and antibiotic actions. Despite these observed properties, the mechanism of their biological activities has not been completely elucidated so far. On the other hand, the results of enzymatic studies revealed their inhibiting influence on physiologically important extracellular enzymes such as phosphatases, esterases, and ecto-nucleotidases, which are considered target enzymes for the approved biological actions. Accordingly, the overview of the in vitro influence of selected polyoxo-vanadates, -tungstates, and – palladates on cholinesterase, ATPase, and phosphatase activities will be given in this presentation. Cholinesterases, enzymes located on the postsynaptic plasma membrane, have a key role in nerve impulse transmission and were confirmed as the targets of drugs for neurological diseases, which are regularly used in clinical practice. Moreover, ATPases and phosphatases were found to be included in the proliferation and migration of tumor cells, thus the inhibition of these enzymes was found as the mechanism of some anticancer drug actionSimpozijum „Stremljenja i novine u medicini“ Medicinskog fakulteta u Beogradu, Beograd, 04-08. decembra, 2023

Poly[µ2-L-alanine-µ3-nitrato-sodium(I)]

The title compound, [Na(NO3)(C3H7NO2)](n), was obtained unintentionally as the product of an attempted reaction of sodium molybdate in aqueous solution and the amino acid L-alanine ( ala), in order to obtain a gamma-type octamolybdate, Na-4[Mo8O26(ala)(2)].18H(2)O, coordinated by L-alanine. The coordination geometry around the Na atom can be considered as trigonal-bipyramidal, with three bidentate nitrate anions coordinating through their O atoms and two L-alanine molecules each coordinating through one carboxylate O atom

Beneficial impact of lithium bis(oxalato)borate as electrolyte additive for high‐voltage nickel‐rich lithium‐battery cathodes

High-voltage nickel-rich layered cathodes possess the requisite, such as excellent discharge capacity and high energy density, to realize lithium batteries with higher energy density. However, such materials suffer from structural and interfacial instability at high voltages (>4.3 V). To reinforce the stability of these cathode materials at elevated voltages, lithium borate salts are investigated as electrolyte additives to generate a superior cathode-electrolyte interphase. Specifically, the use of lithium bis(oxalato)borate (LiBOB) leads to an enhanced cycling stability with a capacity retention of 81.7%. Importantly, almost no voltage hysteresis is detected after 200 cycles at 1C. This outstanding electrochemical performance is attributed to an enhanced structural and interfacial stability, which is attained by suppressing the generation of micro-cracks and the superficial structural degradation upon cycling. The improved stability stems from the formation of a fortified borate-containing interphase which protects the highly reactive cathode from parasitic reactions with the electrolyte. Finally, the decomposition process of LiBOB and the possible adsorption routes to the cathode surface are deduced and elucidated

Regioselective protein oxidative cleavage enabled by enzyme-like recognition of an inorganic metal oxo cluster ligand

Oxidative modifications of proteins are key to many applications in biotechnology. Metal-catalyzed oxidation reactions efficiently oxidize proteins but with low selectivity, and are highly dependent on the protein surface residues to direct the reaction. Herein, we demonstrate that discrete inorganic ligands such as polyoxometalates enable an efficient and selective protein oxidative cleavage. In the presence of ascorbate (1 mM), the Cu-substituted polyoxometalate K8[Cu2+(H2O)(α2-P2W17O61)], (CuIIWD, 0.05 mM) selectively cleave hen egg white lysozyme under physiological conditions (pH =7.5, 37 °C) producing only four bands in the gel electropherogram (12.7, 11, 10, and 5 kDa). Liquid chromatography/mass spectrometry analysis reveals a regioselective cleavage in the vicinity of crystallographic CuIIWD/lysozyme interaction sites. Mechanistically, polyoxometalate is critical to position the Cu at the protein surface and limit the generation of oxidative species to the proximity of binding sites. Ultimately, this study outlines the potential of discrete, designable metal oxo clusters as catalysts for the selective modification of proteins through radical mechanisms under non-denaturing conditions

Monolacunary Wells-Dawson Polyoxometalate as a Novel Contrast Agent for Computed Tomography: A Comprehensive Study on In Vivo Toxicity and Biodistribution

Polyoxotungstate nanoclusters have recently emerged as promising contrast agents for computed tomography (CT). In order to evaluate their clinical potential, in this study, we evaluated the in vitro CT imaging properties, potential toxic effects in vivo, and tissue distribution of monolacunary Wells–Dawson polyoxometalate, α2-K10P2W17O61.20H2O (mono-WD POM). Mono-WD POM showed superior X-ray attenuation compared to other tungsten-containing nanoclusters (its parent WD-POM and Keggin POM) and the standard iodine-based contrast agent (iohexol). The calculated X-ray attenuation linear slope for mono-WD POM was significantly higher compared to parent WD-POM, Keggin POM, and iohexol (5.97 ± 0.14 vs. 4.84 ± 0.05, 4.55 ± 0.16, and 4.30 ± 0.09, respectively). Acute oral (maximum-administered dose (MAD) = 960 mg/kg) and intravenous administration (1/10, 1/5, and 1/3 MAD) of mono-WD POM did not induce unexpected changes in rats’ general habits or mortality. Results of blood gas analysis, CO-oximetry status, and the levels of electrolytes, glucose, lactate, creatinine, and BUN demonstrated a dose-dependent tendency 14 days after intravenous administration of mono-WD POM. The most significant differences compared to the control were observed for 1/3 MAD, being approximately seventy times higher than the typically used dose (0.015 mmol W/kg) of tungsten-based contrast agents. The highest tungsten deposition was found in the kidney (1/3 MAD—0.67 ± 0.12; 1/5 MAD—0.59 ± 0.07; 1/10 MAD—0.54 ± 0.05), which corresponded to detected morphological irregularities, electrolyte imbalance, and increased BUN levels

Recent Advances in Lanthanide Based Nano-Architectures as Probes for Ultra High-Field Magnetic Resonance Imaging

Paramagnetic Lanthanide ions incorporated into nano- architectures are emerging as a versatile platform for Magnetic Resonance Imaging (MRI) contrast agents due to their strong contrast enhancement effects combined with the platform capability to include multiple imaging modalities. This short review examines the application of lanthanide based nanoarchitectures (nanoparticles and nano- assemblies) in the development of multifunctional probes for single and multimodal imaging involving high field MRI as one imaging modality.status: publishe

Programmable Interlocking Disks: Bottom-Up Modular Assembly of Chemically Relevant Polyhedral and Reticular Structural Models

© 2019 American Chemical Society and Division of Chemical Education, Inc. Single-type, 8-fold-grooved, commercially accessible interlocking disks (ILDs) have been used for modeling of complex polyhedral and reticular topologies with relevance to inorganic and hybrid materials. The assembly of complex topologies relies on the preparation of secondary building units (SBUs), which exhibit different connectivity than that of the primary ILDs. All ILD-based models are light, scalable, programmable, and suitable for discovery-based learning and classroom demonstrations of stereochemistry and complex chemical concepts.status: publishe