Polyoxometalate-stabilized, water dispersible Fe2Pt magnetic nanoparticles

Seemann, K.; Bauer, and Andreas; Kindervater, J.; Meyer, M. L.; Besson, Claire; Luysberg, M.; Durkin, Patrick; Pyckhout‐Hintzen, Wim; Budiša, Nediljko; Georgii, R.; Schneider, Claus M.; Kögerler, Paul

doi:10.1039/c3nr33374d

Cited by 20 publications

(10 citation statements)

References 44 publications

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“…Polyoxometalates (POMs) are generally described as clusters of early transition metal ions in their highest oxidation state and oxo ligands. Thei ncorporation of metal ions into POM frameworks results in aw ide range of molecular structures and physical/chemical properties, [12] resulting in interesting applicationsi nv ariousr esearch domains including medicine, [13] magnetism, [14] material science, [15] and catalysis. [16] Severalk ey properties of Zr IV such as its oxophilicity,r edoxi nactivity,h igh Lewis acidity,f ast ligand exchange kinetics, and ability to form complexes with high coordinationn umbers, make Zr IV -POMs well suited to coordinate and toa ctivate the peptides ubstrate towards peptide bond hydrolysis.…”

Section: Introductionmentioning

confidence: 99%

Chemical Mimics of Aspartate‐Directed Proteases: Predictive and Strictly Specific Hydrolysis of a Globular Protein at Asp−X Sequence Promoted by Polyoxometalate Complexes Rationalized by a Combined Experimental and Theoretical Approach

Mihaylov

Proost

et al. 2019

Chemistry A European J

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Creating efficient and residue-directed artificial proteases is ac hallenging task due to the extreme inertness of the peptideb ond, combined with the difficulty of achieving specific interactions between the catalysts and the protein side chains. Herein we report strictly site-selective hydrolysis of am ulti-subunit globular protein, hemoglobin (Hb) from bovine blood, by ar ange of Zr IV -substituted polyoxometalates (Zr-POMs) in mildly acidic and physiological pH solutions. Among5 70 peptideb onds in Hb, selective cleavage was observed at only eleven sites, each occurring at AspÀXp eptideb onds located in the positive patcheso n the protein surface. The molecular origins of the observed AspÀXs electivity were rationalized by means of molecular docking, DFT-based binding, and mechanistic studies on model peptides. The proposed mechanism of hydrolysis involves coordination of the amide oxygen to Zr IV followed by ad irect nucleophilic attack of the side chain carboxylate group on the C-terminal amide carbon atom with formation of ac yclic anhydride, which is furtherh ydrolyzed to give the reactionp roducts. The activation energy for the cleavage of the structurally relatedG luÀXs equence compared to AspÀX was calculated to be higherb y1 .4 kcal mol À1 ,w hich corresponds to ad ifference of about one order of magnitude in the rates of hydrolysis. The highera ctivatione nergy is attributed to the higher strain presenti nt he six-membered ring of glutaric anhydride (GluÀX), as compared to the five-membered ring of the succinic anhydride (AspÀX) intermediate. Similarly,t he cleavage at XÀAsp and XÀGlu bonds are predicted to be kinetically less likely as the corresponding activation energies were 6kcal mol À1 higher , explaining the experimentally observeds electivity.T he synergy between the negativelyc harged polyoxometalate cluster, which binds at positive patches on protein surfaces, ands elective activation of AspÀXp eptideb onds located in these regions by Zr IV ions, resultsi nanovel class of artificial proteases with aspartate-directed reactivity,w hich is very rare among naturally occurring proteases.[a] Dr.

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Section: Introductionmentioning

confidence: 99%

Chemical Mimics of Aspartate‐Directed Proteases: Predictive and Strictly Specific Hydrolysis of a Globular Protein at Asp−X Sequence Promoted by Polyoxometalate Complexes Rationalized by a Combined Experimental and Theoretical Approach

Mihaylov

Proost

et al. 2019

Chemistry A European J

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“…The size of the FePt core-shell and the functionalized particle are very small in comparison to many other nanoparticles [20] and also smaller than the previously published non-annealed particles which are 4.7 nm in diameter [3]. The particles are of similar size as proteins like the green fluorescent protein that has a diameter of 3 nm and a length of 4 nm [21].…”

Section: Characterization and Functionalization Of Fept Core-shell Namentioning

confidence: 81%

“…The bimetallic FePt core-shell precursor nanoparticles were synthesized in a one-pot reaction from iron-(III)-acetylacetonat and platinum-(II)-acetylacetonat in the presence of modified Keggin-poly silico tungstate as described before [3] followed by high-temperature annealing in a reducing gas atmosphere at 700 °C for 3 hours. To prevent agglomeration during annealing, the nanoparticles were incorporated into a sodium-chloride matrix prior to the high temperature treatment, which was dissolved and washed out again using high-purity deionized water afterwards.…”

Section: Nanoparticlesmentioning

confidence: 99%

“…One suitable compound that can be employed for coating nanoparticles are polyoxometalates, which are inorganic cluster molecules synthesized in aqueous solution. Polyoxometalates offer a high degree of thermodynamic stability [3] and have been shown to cover the surface of gold nanoparticles in water via electrostatic interaction [4,5]. They also coat magnetic FePt nanoparticles during synthesis in non-polar organic solutions when modified to match the required solubility.…”

Section: Introductionmentioning

confidence: 99%

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Multi-photon excited luminescence of magnetic FePt core-shell nanoparticles

Seemann¹,

Kühn²

2014

Biomed. Opt. Express

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We present magnetic FePt nanoparticles with a hydrophilic, inert, and biocompatible silico-tungsten oxide shell. The particles can be functionalized, optically detected, and optically manipulated. To show the functionalization the fluorescent dye NOPS was bound to the FePt core-shell nanoparticles with propyl-triethoxy-silane linkers and fluorescence of the labeled particles were observed in ethanol (EtOH). In aqueous dispersion the NOPS fluorescence is quenched making them invisible using 1-photon excitation. However, we observe bright luminescence of labeled and even unlabeled magnetic core-shell nanoparticles with multi-photon excitation. Luminescence can be detected in the near ultraviolet and the full visible spectral range by near infrared multi-photon excitation. For optical manipulation, we were able to drag clusters of particles, and maybe also single particles, by a focused laser beam that acts as optical tweezers by inducing an electric dipole in the insulated metal nanoparticles. In a first application, we show that the luminescence of the core-shell nanoparticles is bright enough for in vivo multi-photon imaging in the mouse neocortex down to cortical layer 5.

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“…In general, POMs consist of MO n units, where n ( n = 4–7) indicates the coordination number of M. Apart from M and O, other elements, which are usually labeled as X, can be part of the POM framework. As a general rule, they are fourfold or sixfold coordinated and can be found in the center of the M x O y shell. , The chemically robust nature of POMs, together with their highly tunable physicochemical properties such as acidity, thermal stability, redox potential, solubility, size, shape, and charge, resulted in their application in material science, magnetism, and catalysis . In addition, several classes of POMs have been reported to have potent antitumor, antiviral, and antibacterial properties, resulting in a substantial interest in the potential medicinal application of POMs .…”

Section: Introductionmentioning

confidence: 99%

Phosphate Ester Bond Hydrolysis Promoted by Lanthanide-Substituted Keggin-type Polyoxometalates Studied by a Combined Experimental and Density Functional Theory Approach

Lương¹,

Mihaylov²,

Absillis³

et al. 2016

Inorg. Chem.

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Hydrolytic cleavage of 4-nitrophenyl phosphate (NPP), a commonly used DNA model substrate, was examined in the presence of series of lanthanide-substituted Keggin-type polyoxometalates (POMs) [MeNH][Ce(PWO)], [MeNH][Ce(PWO)] (abbreviated as (Ce(PW)), and K[EuPWO] by means of NMR and luminescence spectroscopies and density functional theory (DFT) calculations. Among the examined complexes, the Ce(IV)-substituted Keggin POM (Ce(PW)) showed the highest reactivity, and its aqueous speciation was fully determined under different conditions of pD, temperature, concentration, and ionic strength by means of P andP diffusion-ordered NMR spectroscopy. The cleavage of the phosphoester bond of NPP in the presence of (Ce(PW)) proceeded with an observed rate constant k = (5.31 ± 0.06) × 10 s at pD 6.4 and 50 °C. The pD dependence of NPP hydrolysis exhibits a bell-shaped profile, with the fastest rate observed at pD 6.4. The formation constant (K = 127 M) and catalytic rate constant (k = 19.41 × 10 s) for the NPP-Ce(IV)-Keggin POM complex were calculated, and binding between Ce(PW) and the phosphate group of NPP was also evidenced by the change of the chemical shift of the P nucleus in NPP upon addition of the POM complex. DFT calculations revealed that binding of NPP to the parent catalyst Ce(PW) is thermodynamically unlikely. On the contrary, formation of complexes with the monomeric 1:1 species, CePW, is considered to be more favorable, and the most stable complex, [CePW(HO)(NPP-κO)], was found to involve two NPP ligands coordinated to the Cecenter of CePW in the monodentate fashion. The formation of such species is considered to be responsible for the hydrolytic activity of Ce(PW) toward phosphomonoesters. On the basis of these findings a principle mechanism for the hydrolysis of NPP by the POM is proposed.

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Polyoxometalate-stabilized, water dispersible Fe2Pt magnetic nanoparticles

Cited by 20 publications

References 44 publications

Chemical Mimics of Aspartate‐Directed Proteases: Predictive and Strictly Specific Hydrolysis of a Globular Protein at Asp−X Sequence Promoted by Polyoxometalate Complexes Rationalized by a Combined Experimental and Theoretical Approach

Chemical Mimics of Aspartate‐Directed Proteases: Predictive and Strictly Specific Hydrolysis of a Globular Protein at Asp−X Sequence Promoted by Polyoxometalate Complexes Rationalized by a Combined Experimental and Theoretical Approach

Multi-photon excited luminescence of magnetic FePt core-shell nanoparticles

Phosphate Ester Bond Hydrolysis Promoted by Lanthanide-Substituted Keggin-type Polyoxometalates Studied by a Combined Experimental and Density Functional Theory Approach

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