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De Clercq K, Persoons E, Napso T, Luyten C, Parac-Vogt TN, Sferruzzi-Perri AN, Kerckhofs G, Vriens J. High-resolution contrast-enhanced microCT reveals the true three-dimensional morphology of the murine placenta. Proc Natl Acad Sci U S A 2019; 116:13927-13936. [PMID: 31249139 PMCID: PMC6683600 DOI: 10.1073/pnas.1902688116] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Genetic engineering of the mouse genome identified many genes that are essential for embryogenesis. Remarkably, the prevalence of concomitant placental defects in embryonic lethal mutants is highly underestimated and indicates the importance of detailed placental analysis when phenotyping new individual gene knockouts. Here we introduce high-resolution contrast-enhanced microfocus computed tomography (CE-CT) as a nondestructive, high-throughput technique to evaluate the 3D placental morphology. Using a contrast agent, zirconium-substituted Keggin polyoxometalate (Zr-POM), the soft tissue of the placenta (i.e., different layers and cell types and its vasculature) was imaged with a resolution of 3.5 µm voxel size. This approach allowed us to visualize and study early and late stages of placental development. Moreover, CE-CT provides a method to precisely quantify placental parameters (i.e., volumes, volume fraction, ratio of different placental layers, and volumes of specific cell populations) that are crucial for statistical comparison studies. The CE-CT assessment of the 3D morphology of the placentas was validated (i) by comparison with standard histological studies; (ii) by evaluating placentas from 2 different mouse strains, 129S6 and C57BL/6J mice; and (iii) by confirming the placental phenotype of mice lacking phosphoinositol 3-kinase (PI3K)-p110α. Finally, the Zr-POM-based CE-CT allowed for inspection of the vasculature structure in the entire placenta, as well as detecting placental defects in pathologies characterized by embryonic resorption and placental fusion. Taken together, Zr-POM-based CE-CT offers a quantitative 3D methodology to investigate placental development or pathologies.
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Harris M, Laskaratou D, Elst LV, Mizuno H, Parac-Vogt TN. Amphiphilic Nanoaggregates with Bimodal MRI and Optical Properties Exhibiting Magnetic Field Dependent Switching from Positive to Negative Contrast Enhancement. ACS APPLIED MATERIALS & INTERFACES 2019; 11:5752-5761. [PMID: 30640430 DOI: 10.1021/acsami.8b18456] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Mixed micelles based on amphiphilic gadolinium(III)-DOTA and europium(III)-DTPA complexes were synthesized and evaluated for their paramagnetic and optical properties as potential bimodal contrast agents. Amphiphilic folate molecule for targeting the folate receptor protein, which is commonly expressed on the surface of many human cancer cells, was used in the self-assembly process in order to create nanoaggregates with targeting properties. Both targeted and nontargeted nanoaggregates formed monodisperse micelles having distribution maxima of 10 nm. The micelles show characteristic europium(III) emission with quantum yields of 2% and 1.1% for the nontargeted and targeted micelles, respectively. Fluorescence microscopy using excitation at 405 nm and emission at 575-675 nm was employed to visualize the nanoaggregates in cultured HeLa cells. The uptake of folate-targeted and nontargeted micelles is already visible after 5 h of incubation and was characterized with the europium(III) emission, which is clearly observable in the cytoplasm of the cells. The very fast longitudinal relaxivity r1 of ca. 26 s-1 mM-1 per gadolinium(III) ion was observed for both micelles at 60 MHz and 310 K. Upon increasing the magnetic field to 300 MHz, the nanoaggregates exhibited a large switching to transversal relaxivity with r2 value of ca. 52 s-1 mM-1 at 310 K. Theoretical fitting of the 1H NMRD profiles indicate that the efficient T1 and T2 relaxations are sustained by the favorable magnetic and electron-configuration properties of the gadolinium(III) ion, rotational correlation time, and coordinated water molecule. These nanoaggregates could have versatile application as a positive contrast agent at the currently used magnetic imaging field strengths and a negative contrast agent in higher field applications, while at the same time offering the possibility for the loading of hydrophobic therapeutics or targeting molecules.
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Beekman KM, Veldhuis-Vlug AG, van der Veen A, den Heijer M, Maas M, Kerckhofs G, Parac-Vogt TN, Bisschop PH, Bravenboer N. The effect of PPARγ inhibition on bone marrow adipose tissue and bone in C3H/HeJ mice. Am J Physiol Endocrinol Metab 2019; 316:E96-E105. [PMID: 30457914 DOI: 10.1152/ajpendo.00265.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Bone marrow adipose tissue (BMAT) increases after menopause, and increased BMAT is associated with osteoporosis and prevalent vertebral fractures. Peroxisome proliferator-activated receptor-γ (PPARγ) activation promotes adipogenesis and inhibits osteoblastogenesis; therefore, PPARγ is a potential contributor to the postmenopausal increase in BMAT and decrease in bone mass. The aim of this study is to determine if PPARγ inhibition can prevent ovariectomy-induced BMAT increase and bone loss in C3H/HeJ mice. Fourteen-week-old female C3H/HeJ mice ( n = 40) were allocated to four intervention groups: sham surgery (Sham) or ovariectomy (OVX; isoflurane anesthesia) with either vehicle (Veh) or PPARγ antagonist administration (GW9662; 1 mg·kg-1·day-1, daily intraperitoneal injections) for 3 wk. We measured BMAT volume, adipocyte size, adipocyte number. and bone structural parameters in the proximal metaphysis of the tibia using polyoxometalate-based contrast enhanced-nanocomputed topogaphy. Bone turnover was measured in the contralateral tibia using histomorphometry. The effects of surgery and treatment were analyzed by two-way ANOVA. OVX increased the BMAT volume fraction (Sham + Veh: 2.9 ± 2.7% vs. OVX + Veh: 8.1 ± 5.0%: P < 0.001), average adipocyte diameter (Sham + Veh: 19.3 ± 2.6 μm vs. OVX + Veh: 23.1 ± 3.4 μm: P = 0.001), and adipocyte number (Sham + Veh: 584 ± 337cells/μm3 vs. OVX + Veh: 824 ± 113cells/μm3: P = 0.03), while OVX decreased bone volume fraction (Sham + Veh: 15.5 ± 2.8% vs. OVX + Veh: 7.7 ± 1.9%; P < 0.001). GW9662 had no effect on BMAT, bone structural parameters, or bone turnover. In conclusion, ovariectomy increased BMAT and decreased bone volume in C3H/HeJ mice. The PPARγ antagonist GW9662 had no effect on BMAT or bone volume in C3H/HeJ mice, suggesting that BMAT accumulation is regulated independently of PPARγ in C3H/HeJ mice.
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Anyushin AV, Sap A, Quanten T, Proost P, Parac-Vogt TN. Selective Hydrolysis of Ovalbumin Promoted by Hf(IV)-Substituted Wells-Dawson-Type Polyoxometalate. Front Chem 2018; 6:614. [PMID: 30619823 PMCID: PMC6305993 DOI: 10.3389/fchem.2018.00614] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 11/28/2018] [Indexed: 12/14/2022] Open
Abstract
The reactivity and selectivity of Wells-Dawson type polyoxometalate (POM), K16[Hf(α2-P2W17O61)2]·19H2O (Hf1-WD2), have been examined with respect to the hydrolysis of ovalbumin (OVA), a storage protein consisting of 385 amino acids. The exact cleavage sites have been determined by Edman degradation experiments, which indicated that Hf1-WD2 POM selectively cleaved OVA at eight peptide bonds: Phe13-Asp14, Arg85-Asp86, Asn95-Asp96, Ala139-Asp140, Ser148-Trp149, Ala361-Asp362, Asp362-His363, and Pro364-Phe365. A combination of spectroscopic methods including 31P NMR, Circular Dichroism (CD), and Tryptophan (Trp) fluorescence spectroscopy were employed to gain better understanding of the observed selective cleavage and the underlying hydrolytic mechanism. 31P NMR spectra have shown that signals corresponding to Hf1-WD2 gradually broaden upon addition of OVA and completely disappear when the POM-protein molar ratio becomes 1:1, indicating formation of a large POM/protein complex. CD demonstrated that interactions of Hf1-WD2 with OVA in the solution do not result in protein unfolding or denaturation even upon adding an excess of POM. Trp fluorescence spectroscopy measurements revealed that the interaction of Hf1-WD2 with OVA (Kq = 1.1 × 105 M−1) is both quantitatively and qualitatively slightly weaker than the interaction of isostructural Zr-containing Wells-Dawson POM (Zr1-WD2) with human serum albumin (HAS) (Kq = 5.1 × 105 M−1).
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Harris M, Kolanowski JL, O'Neill ES, Henoumont C, Laurent S, Parac-Vogt TN, New EJ. Drawing on biology to inspire molecular design: a redox-responsive MRI probe based on Gd(iii)-nicotinamide. Chem Commun (Camb) 2018; 54:12986-12989. [PMID: 30387480 DOI: 10.1039/c8cc07092j] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A novel, reversible redox-active MRI probe, GdNR1, has been developed for the study of redox changes associated with diseased states. This system exhibits switching in relaxivity upon reduction and oxidation of the appended nicotinimidium. Relaxivity studies and cyclic voltammetry confirmed the impressive reversibility of this system, at a biologically-relevant reduction potential. A 2.5-fold increase in relaxivity was observed upon reduction of the complex, which corresponds to a change in the number of inner-sphere water molecules, as confirmed by luminescence lifetimes of the Eu(iii) analogue and NMRD studies. This is the first example of a redox-responsive MRI probe utilising the biologically-inspired nicotinimidium redox switch. In the future this strategy could enable the non-invasive identification of hypoxic tissue and related cardiovascular disease.
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Van Rompuy LS, Parac-Vogt TN. Interactions between polyoxometalates and biological systems: from drug design to artificial enzymes. Curr Opin Biotechnol 2018; 58:92-99. [PMID: 30529815 DOI: 10.1016/j.copbio.2018.11.013] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 11/20/2018] [Indexed: 12/11/2022]
Abstract
Polyoxometalates have long been studied in a variety of biological applications. Interactions between the highly charged POM molecules and biological molecules frequently occur through hydrogen-bonding and electrostatic interactions. Tellurium-centred Anderson-Evans POMs show exceptional promise as crystallization agents, while acidic and metal-substituted POMs may provide interesting alternatives to enzymes in proteomics applications. While POMs also show interesting results in a number of medicinal applications, for example as anti-amyloid agents for the treatment of Alzheimer's disease and as anti-tumoral agents, their use is often impeded by their toxicity. Many recent studies have therefore focussed on POM-functionalization to reduce toxicity and increase activity by addition of biological targeting molecules.
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Vandebroek L, Mampaey Y, Antonyuk S, Van Meervelt L, Parac-Vogt TN. Noncovalent Complexes Formed between Metal-Substituted Polyoxometalates and Hen Egg White Lysozyme. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201801113] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Vandebroek L, Van Meervelt L, Parac-Vogt TN. 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. ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 2018; 74:1348-1354. [DOI: 10.1107/s2053229618010690] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 07/24/2018] [Indexed: 11/11/2022]
Abstract
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.
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Quanten T, De Mayaer T, Shestakova P, Parac-Vogt TN. Selectivity and Reactivity of Zr IV and Ce IV Substituted Keggin Type Polyoxometalates Toward Cytochrome c in Surfactant Solutions. Front Chem 2018; 6:372. [PMID: 30211153 PMCID: PMC6121075 DOI: 10.3389/fchem.2018.00372] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 08/02/2018] [Indexed: 12/15/2022] Open
Abstract
In this paper we investigate the effect of three different types of surfactants, on the hydrolysis of Cytochrome c (Cyt c), a predominantly α helical protein containing a heme group, promoted by [Ce(α PW11O39)2]10- (CeK) and [Zr(α PW11O39)2]10- (ZrK) polyoxometalates. In the presence of SDS, Zw3 12, or CHAPS surfactants, which are commonly used for solubilizing hydrophobic proteins, the specificity of CeK or ZrK toward hydrolysis of Cyt c does not change. However, the hydrolysis rate of Cyt c by CeK was increased in the presence of SDS, but decreased in the presence of CHAPS, and was nearly inhibited in the presence of Zw3 12. The Circular dichroism and Tryptophan fluorescence spectroscopy have shown that the structural changes in Cyt c caused by surfactants are similar to those caused by POMs, hence the same specificity in the absence or presence of surfactants was observed. The results also indicate that for Cyt c hydrolysis to occur, large unfolding of the protein is needed in order to accommodate the POMs. While SDS readily unfolds Cyt c, the protein remains largely folded in the presence of CHAPS and Zw3 12. Addition of POMs to Cyt c solutions in CHAPS results in unfolding of the structure allowing the interaction with POMs to occur and results in protein hydrolysis. Zw3 12, however, locks Cyt c in a conformation that resists unfolding upon addition of POM, and therefore results in nearly complete inhibition of protein hydrolysis.
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Abstract
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.
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Vandebroek L, De Zitter E, Ly HGT, Conić D, Mihaylov T, Sap A, Proost P, Pierloot K, Van Meervelt L, Parac-Vogt TN. Protein-Assisted Formation and Stabilization of Catalytically Active Polyoxometalate Species. Chemistry 2018; 24:10099-10108. [PMID: 29797738 DOI: 10.1002/chem.201802052] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 05/17/2018] [Indexed: 01/24/2023]
Abstract
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.
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Paul TJ, Parac-Vogt TN, Quiñonero D, Prabhakar R. Investigating Polyoxometalate–Protein Interactions at Chemically Distinct Binding Sites. J Phys Chem B 2018; 122:7219-7232. [DOI: 10.1021/acs.jpcb.8b02931] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Ly HGT, Fu G, Kondinski A, Bueken B, De Vos D, Parac-Vogt TN. Superactivity of MOF-808 toward Peptide Bond Hydrolysis. J Am Chem Soc 2018; 140:6325-6335. [PMID: 29684281 DOI: 10.1021/jacs.8b01902] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
MOF-808, a Zr(IV)-based metal-organic framework, has been proven to be a very effective heterogeneous catalyst for the hydrolysis of the peptide bond in a wide range of peptides and in hen egg white lysozyme protein. The kinetic experiments with a series of Gly-X dipeptides with varying nature of amino acid side chain have shown that MOF-808 exhibits selectivity depending on the size and chemical nature of the X side chain. Dipeptides with smaller or hydrophilic residues were hydrolyzed faster than those with bulky and hydrophobic residues that lack electron rich functionalities which could engage in favorable intermolecular interactions with the btc linkers. Detailed kinetic studies performed by 1H NMR spectroscopy revealed that the rate of glycylglycine (Gly-Gly) hydrolysis at pD 7.4 and 60 °C was 2.69 × 10-4 s-1 ( t1/2 = 0.72 h), which is more than 4 orders of magnitude faster compared to the uncatalyzed reaction. Importantly, MOF-808 can be recycled several times without significantly compromising the catalytic activity. A detailed quantum-chemical study combined with experimental data allowed to unravel the role of the {Zr6O8} core of MOF-808 in accelerating Gly-Gly hydrolysis. A mechanism for the hydrolysis of Gly-Gly by MOF-808 is proposed in which Gly-Gly binds to two Zr(IV) centers of the {Zr6O8} core via the oxygen atom of the amide group and the N-terminus. The activity of MOF-808 was also demonstrated toward the hydrolysis of hen egg white lysozyme, a protein consisting of 129 amino acids. Selective fragmentation of the protein was observed with 55% yield after 25 h under physiological pH.
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Biju S, Gallo J, Bañobre-López M, Manshian BB, Soenen SJ, Himmelreich U, Vander Elst L, Parac-Vogt TN. A Magnetic Chameleon: Biocompatible Lanthanide Fluoride Nanoparticles with Magnetic Field Dependent Tunable Contrast Properties as a Versatile Contrast Agent for Low to Ultrahigh Field MRI and Optical Imaging in Biological Window. Chemistry 2018; 24:7388-7397. [PMID: 29575427 DOI: 10.1002/chem.201800283] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Indexed: 12/11/2022]
Abstract
A novel type of multimodal, magnetic resonance imaging/optical imaging (MRI/OI) contrast agent was developed, based on core-shell lanthanide fluoride nanoparticles composed of a β-NaHoF4 core plus a β-NaGdF4:Yb3+ , Tm3+ shell with an average size of ∼24 nm. The biocompatibility of the particles was ensured by a surface modification with poly acrylic acid (PAA) and further functionalization with an affinity ligand, folic acid (FA). When excited using 980 nm near infrared (NIR) radiation, the contrast agent (CA) shows intense emission at 802 nm with lifetime of 791±3 μs, due to the transition 3 H4 →3 H6 of Tm3+ . Proton nuclear magnetic relaxation dispersion (1 H-NMRD) studies and magnetic resonance (MR) phantom imaging showed that the newly synthesized nanoparticles, decorated with poly(acrylic acid) and folic acid on the surface (NP-PAA-FA), can act mainly as a T1 -weighted contrast agent below 1.5 T, a T1 /T2 dual-weighted contrast agent at 3 T, and as highly efficient T2 -weighted contrast agent at ultrahigh fields. In addition, NP-PAA-FA showed very low cytotoxicity and no detectable cellular damage up to a dose of 500 μg mL-1 .
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Harris M, Henoumont C, Peeters W, Toyouchi S, Vander Elst L, Parac-Vogt TN. Amphiphilic complexes of Ho(iii), Dy(iii), Tb(iii) and Eu(iii) for optical and high field magnetic resonance imaging. Dalton Trans 2018; 47:10646-10653. [DOI: 10.1039/c8dt01227j] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Amphiphilic lanthanide(iii) complexes self-assemble into monodisperse micelles with favourable properties for optical and high field magnetic resonance imaging.
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Vandebroek L, Parac-Vogt TN, Van Meervelt L. Investigating the binding mechanism of polyoxometalates towards proteins. Acta Crystallogr A Found Adv 2017. [DOI: 10.1107/s2053273317088428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Luong TKN, Govaerts I, Robben J, Shestakova P, Parac-Vogt TN. Polyoxometalates as artificial nucleases: hydrolytic cleavage of DNA promoted by a highly negatively charged Zr IV-substituted Keggin polyanion. Chem Commun (Camb) 2017; 53:617-620. [PMID: 27982140 DOI: 10.1039/c6cc08555e] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A highly negatively charged binuclear ZrIV-substituted Keggin polyoxometalate [{α-PW11O39Zr(μ-OH)(H2O)}2]8- (ZrK 2 : 2) has been shown to promote the hydrolytic cleavage of phosphoester bonds in the supercoiled plasmid pUC19 DNA under physiological pH and temperature, giving relaxed and linear forms of pUC19 as hydrolysis products. The interaction between ZrK 2 : 2 and DNA was experimentally proven by circular dichroism (CD) spectroscopy and 31P diffusion ordered NMR spectroscopy.
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Ly HGT, Parac-Vogt TN. Spectroscopic Study of the Interaction between Horse Heart Myoglobin and Zirconium(IV)-Substituted Polyoxometalates as Artificial Proteases. Chemphyschem 2017; 18:2451-2458. [PMID: 28675658 DOI: 10.1002/cphc.201700680] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Indexed: 01/19/2023]
Abstract
A recent study [Angew. Chem. Int. Ed. 2015, 54, 7391-7394] has shown that horse heart myoglobin (HHM) is selectively hydrolyzed by a range of zirconium(IV)-substituted polyoxometalates (POMs) under mild conditions. In this study, the molecular interactions between the Zr-POM catalysts and HHM are investigated by using a range of complementary techniques, including circular dichroism (CD), UV/Vis spectroscopy, tryptophan fluorescence spectroscopy, and 1 H and 31 P NMR spectroscopy. A tryptophan fluorescence quenching study reveals that, among all examined Zr-POMs, the most reactive POM, 2:2 ZrIV -Keggin, exhibits the strongest interaction with HHM. 31 P NMR spectroscopy studies show that this POM dissociates in solution, resulting in the formation of a monomeric 1:1 ZrIV -Keggin structure, which is likely to be a catalytically active species. In the presence of ZrIV -POMs, HHM does not undergo complete denaturation, as evidenced by CD, UV/Vis, tryptophan fluorescence, and 1 H NMR spectroscopy. CD spectroscopy shows a gradual decrease in the α-helical content of HHM upon addition of ZrIV -POMs. The largest effect is observed in the presence of a large ZrIV -Wells-Dawson structure, whereas small ZrIV -Lindqvist POM has the least influence on the decrease in the α-helical content of HHM. In all cases, the Soret band at λ=409 nm is maintained in the presence of all examined Zr-POMs, which indicates that no conformational changes in the protein occur near the heme group.
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Sap A, Vandebroek L, Goovaerts V, Martens E, Proost P, Parac-Vogt TN. Highly Selective and Tunable Protein Hydrolysis by a Polyoxometalate Complex in Surfactant Solutions: A Step toward the Development of Artificial Metalloproteases for Membrane Proteins. ACS OMEGA 2017; 2:2026-2033. [PMID: 30023653 PMCID: PMC6044816 DOI: 10.1021/acsomega.7b00168] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 04/28/2017] [Indexed: 05/17/2023]
Abstract
This study represents the first example of protein hydrolysis at pH = 7.4 and 60 °C by a metal-substituted polyoxometalate (POM) in the presence of a zwitterionic surfactant. Edman degradation results show that in the presence of 0.5% w/v 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) detergent, a Zr(IV)-substituted Wells-Dawson-type POM, K15H[Zr(α2-P2W17O61)2]·25H2O (Zr1-WD2), selectively hydrolyzes human serum albumin exclusively at peptide bonds involving Asp or Glu residues, which contain carboxyl groups in their side chains. The selectivity and extent of protein cleavage are tuned by the CHAPS surfactant by an unfolding mechanism that provides POM access to the hydrolyzed peptide bonds.
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Vanhaecht S, Quanten T, Parac-Vogt TN. A Simple Nucleophilic Substitution as a Versatile Postfunctionalization Method for the Coupling of Nucleophiles to an Anderson-Type Polyoxometalate. Inorg Chem 2017; 56:3095-3101. [DOI: 10.1021/acs.inorgchem.6b03131] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Van Rompuy LS, Parac-Vogt TN. Polyoxometalates as sialidase mimics: selective and non-destructive removal of sialic acid from a glycoprotein promoted by phosphotungstic acid. Chem Commun (Camb) 2017; 53:10600-10603. [DOI: 10.1039/c7cc05888h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The selective hydrolysis of the glycosidic bond between the terminal sialic acid and the penultimate sugar has been achieved in the alpha-2-HS-glycoprotein (Fetuin-A) in the presence of H3PW12O40, a Keggin type polyoxometalate.
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Harris M, De Keersmaecker H, Vander Elst L, Debroye E, Fujita Y, Mizuno H, Parac-Vogt TN. Following the stability of amphiphilic nanoaggregates by using intermolecular energy transfer. Chem Commun (Camb) 2016; 52:13385-13388. [PMID: 27786313 DOI: 10.1039/c6cc07714e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An intermolecular energy transfer system is developed for studying the stability of nanoaggregate(s) (NAs) in complex solution and cell culture by one- and two-photon fluorescence microscopy and optical imaging. The system allows facile addition of one or more tumor targeting molecules, one of which is exemplified here. NAs functionalized with an MRI and optical probe, with and without folic acid, remain stable in fetal bovine serum for at least 4 hours. HeLa cell cultures showed a clear difference between NAs non-targeted and targeted to folate receptors, with both NAs appearing to be taken up by the cells through different mechanisms. An MRI relaxivity, r1, of 9 mM-1 s-1 at 310 K and 1.4 T was measured associated with the increased rotational correlation time of the NAs. These NAs may have application in the targeted drug delivery of hydrophobic drugs such as doxorubicin (DOX).
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Solé-Daura A, Goovaerts V, Stroobants K, Absillis G, Jiménez-Lozano P, Poblet JM, Hirst JD, Parac-Vogt TN, Carbó JJ. Cover Picture: Probing Polyoxometalate-Protein Interactions Using Molecular Dynamics Simulations (Chem. Eur. J. 43/2016). Chemistry 2016. [DOI: 10.1002/chem.201603456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Solé-Daura A, Goovaerts V, Stroobants K, Absillis G, Jiménez-Lozano P, Poblet JM, Hirst JD, Parac-Vogt TN, Carbó JJ. Probing Polyoxometalate-Protein Interactions Using Molecular Dynamics Simulations. Chemistry 2016. [DOI: 10.1002/chem.201603740] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Sap A, Van Tichelen L, Mortier A, Proost P, Parac-Vogt TN. Tuning the Selectivity and Reactivity of Metal-Substituted Polyoxometalates as Artificial Proteases by Varying the Nature of the Embedded Lewis Acid Metal Ion. Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201601098] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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