A two-step binding process of Eu-containing polyoxometalates to bovine serum albumin

Nanocomposites of ionic copolymer integrating Gd-containing polyoxometalate as a multiple platform for enhanced MRI and pH-response chemotherapy

Nanocomposites from the co-assemblies of block copolymers and a gadolinium-grafting inorganic cluster were constructed as a multifunctional platform for MRI enhancement, drug loading, and environment-response release at local positions.

Transition metal substituted sandwich-type polyoxometalates with a strong metal–C (imidazole) bond as anticancer agents

The metal–carbon bond plays a pivotal role in the structural stabilities and biological activities of metal-based anticancer drugs. The strong M–C_imi bond is first introduced into sandwich-type POMs [Na_0.7M_5.3(H₂O)₂(imi)₂(Himi)(SbW₉O₃₃)₂]⁶⁻, (M = Ni^II (1), Co^II (2), imi = imidazole).

Direct observation of the ZrIV interaction with the carboxamide bond in a noncovalent complex between Hen Egg White Lysozyme and a Zr-substituted Keggin polyoxometalate

The successful cocrystallization of the noncovalent complex formed between (Et2NH2)8[{α-PW11O39Zr-(μ-OH)(H2O)}2]·7H2O Keggin polyoxometalate (2) and Hen Egg White Lysozyme (HEWL) protein is reported. The resulting structural model revealed interaction between monomeric [Zr(PW11O39)]4−(1), which is a postulated catalytically active species, and the protein in two positions in the asymmetric unit. The first position (occupancy 36%) confirms the previously observed binding sites on the protein surface, whereas the second position (occupancy 14%) provides novel insights into the hydrolytic mechanisms of ZrIV-substituted polyoxometalates. The new interaction site occurs at the Asn65 residue, which is directly next to the Asp66–Gly67 peptide bond that was identified recently as a cleavage site in the polyoxometalate-catalysed hydrolysis of HEWL. Furthermore, in this newly discovered binding site, the monomeric polyoxometalate 1 is observed to bind directly to the side chain of the Asn65 residue. This binding of ZrIV as a Lewis-acid metal to the carbonyl O atom of the Asn65 side chain is very similar to the intermediate state proposed in density functional theory (DFT) studies in which ZrIV activates the peptide bond via interaction with its carbonyl O atom, and can be thus regarded as a model for interaction between ZrIV and a peptide bond.

Protein-Assisted Formation and Stabilization of Catalytically Active Polyoxometalate Species

The effect of the protein environment on the formation and stabilization of an elusive catalytically active polyoxometalate (POM) species, K₆ [Hf(α₂ -P₂ W₁₇ O₆₁ )] (1), is reported. In the co-crystal of hen egg-white lysozyme (HEWL) with 1, the catalytically active monomeric species is observed, originating from the dimeric 1:2 POM form, while it is intrinsically unstable under physiological pH conditions. The protein-assisted dissociation of the dimeric POM was rationalized by means of DFT calculations. The dissociation process is unfavorable in bulk water, but becomes favorable in the protein-POM complex due to the low dielectric response at the protein surface. The crystal structure shows that the monomeric form is stabilized by electrostatic and water-mediated hydrogen bonding interactions with the protein. It interacts at three distinct sites, close to the aspartate-containing hydrolysis sites, demonstrating high selectivity towards peptide bonds containing this residue.

Cell receptor screening for human papillomavirus invasion by using a polyoxometalate-peptide assembly as a probe

The present study constructed a competitive recognition system using cell receptor screening for human papillomavirus (HPV) invasion by using the hybrid-assembly of polyoxometalates (POMs) and cationic peptides as a platform. The fine tuning both of the surface charge of POMs and peptide sequence were precisely performed to develop a luminescence switch of POMs, leading to the establishment of a ternary system to identify which types of glycosaminoglycans (GAGs) are potential cell receptors for HPV infection. In addition, the method was successfully applied to construct a hybrid-assembly with the recombined HPV 16 L1 pentamers from Escherichia coli and perform GAGs screening, which validated the system's potential for practical applications. In particular, the intrinsic mechanism for each competitive partner in the system was explained well by using isothermal titration calorimetry (ITC) and time-resolved fluorescence spectra. The present method will be helpful to extend the protocol to other systems by using peptides and POMs with similar properties, and ultimately, we hope it will promote the development of anti-viral agents.

The Anti-Proliferation Activity and Mechanism of Action of K12[V18O42(H₂O)]∙6H₂O on Breast Cancer Cell Lines

Polyoxometalates (POMs) are inorganic clusters that possess potential anti-bacterial, anti-viral, and anti-tumor activities. Herein, the in vitro anti-proliferation activities of K₁₂[V₁₈O₄₂(H₂O)]∙6H₂O (V₁₈) have been investigated on the MCF-7 and MDA-MB-231 cell lines. The results indicated that V₁₈ could inhibit the proliferation of MCF-7 (IC₅₀, 11.95 μM at 48 h) in a dose-dependent manner compared to the positive control, 5-fluorouracil (5-Fu, p < 0.05). The anti-proliferation activity of V₁₈ might be mediated by arrest of the MCF-7 cells in the G₂/M phase and induction of apoptosis and necrosis. Moreover, V₁₈ can effectively quench the fluorescence of ctDNA. The binding mode between them may be groove or outside stacking binding. V₁₈ can also effectively quench the intrinsic fluorescence of bovine serum albumin (BSA) and human serum albumin (HSA) via static quenching, and changed the conformation of BSA and HSA.

PCR Incorporation of Polyoxometalate Modified Deoxynucleotide Triphosphates and Their Application in Molecular Electrochemical Sensing of Yersinia pestis

Redox-labeled nucleotides are of increasing interest for the fabrication of next generation molecular tools and should meet requirements of being thermally stable, sensitive, and compatible with polymerase-mediated incorporation while also being electrochemically discriminable. The synthesis and characterization of Keggin and Dawson polyoxometalate-deoxynucleotide (POM-dNTP) bioconjugates linked through 7-deaza-modified purines is described. The modified POM-dNTPs were used for polymerase-based amplification of a DNA sequence specific for Yersinia pestis and the amplified DNA detected using an electrochemical DNA sensor. This highlights the potential of polyoxometalates as thermally stable, sensitive and polymerase-compatible redox labels for exploitation in bioanalytical applications.

Discovery and isolation of the trans-isomers of two 1 : 2-type lanthanide-containing monolacunary Dawson-type tungstophosphates: [LnIII(α2-P2W17O61)2]17− (Ln = La, Ce)

Two novel trans-isomers of 1 : 2-type lanthanide-containing monolacunary Dawson-type tungstophosphates [Ln(α₂-P₂W₁₇O₆₁)₂]¹⁷⁻ (Ln = La^III (1), Ce^III (2)) were successfully isolated and characterized.

A survey of the different roles of polyoxometalates in their interaction with amino acids, peptides and proteins

This perspective provides a comprehensive description of the different roles of POMs in their interaction with relevant biological molecules.

Co-assembly of polyoxometalates and peptides towards biological applications

The synergistic self-assembly of biomolecules with polyoxometalates (POMs) has recently been considered as an effective approach to construct nano-biomaterials with diverse structures and morphologies towards applications in drug delivery, controlled release, tissue engineering scaffolds, and biomineralization, due to the unique features of the clusters in addition to many well-known inorganic nanoparticles. This review presents an overview of recent work focusing on the noncovalent co-assembly of peptides and POMs as well as their biological applications. In the co-assemblies triggered by the interaction between the components significant advantages are observed that POMs or peptides alone do not possess; examples include chiral recognition of hybrid metal oxides, the quick hydrolysis of peptides, and enhanced inhibition of Aβ aggregation. Finally, we outline a brief perspective on possible unresolved issues and future opportunities in this field.

Supermolecular assembly of polyoxoanion and metal–organic cationic units towards a model for core–shell nanostructures

Two novel core–shell-like molecular composites [NiL₃]₄[HV^IV₁₂V^V₆O₄₂(PO₄)] and [NiL₂]₄[HV^IV₁₂V^V₆O₄₂(PO₄)] were designed and synthesized, which exhibited electrocatalytic activity for the reduction of H₂O₂ and oxidation of NO₂⁻.