Vanadium and titanium bimetallic AlPO-5 molecular sieves have been synthesized and characterized by means of Electron Spin Echo detected EPR and Hyperfine Sublevel Correlation (HYSCORE) spectroscopy. Direct evidence for framework substitution of redox-active Ti ions and VO(2+) units at Al sites is provided through the detection of large (31)P hyperfine couplings.
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http://dx.doi.org/10.1039/c2cc33997h | DOI Listing |
Lytic Polysaccharide Monooxygenases (LPMOs) catalyze the oxidative depolymerization of polysaccharides at a monocopper active site, that is coordinated by the so-called histidine brace. In the past, this motif has sparked considerable interest, mostly due to its ability to generate and stabilize highly oxidizing intermediates during catalysis. We used a variety of advanced EPR techniques, including Electron Nuclear Double Resonance (ENDOR), Electron Spin Echo Envelope Modulation (ESEEM) and Hyperfine Sublevel Correlation (HYSCORE) spectroscopy in combination with isotopic labelling (N, H) to characterize the active site of the bacterial LPMO AA10A over a wide pH range (pH 4.
View Article and Find Full Text PDFInorg Chem
December 2024
Aix Marseille Univ, CNRS, BIP UMR7281, IMM, IM2B, Marseille 13009, France.
Mono-pyranopterin-containing sulfite-oxidizing enzymes (SOEs), including eukaryotic sulfite oxidases and homologous prokaryotic sulfite dehydrogenases (SDHs), are molybdenum enzymes that exist in almost all forms of life, where they catalyze the direct oxidation of sulfite into sulfate, playing a key role in protecting cells and organisms against sulfite-induced damage. To decipher their catalytic mechanism, we have previously provided structural and spectroscopic evidence for direct coordination of HPO to the Mo atom at the active site of the SDH from the hyperthermophilic bacterium (SDH), mimicking the proposed sulfate-bound intermediate proposed to be formed during catalysis. In this work, by solving the X-ray crystallographic structure of the unbound enzyme, we resolve the changes in the hydrogen bonding network in the molybdenum environment that enable the stabilization of the previously characterized phosphate adduct.
View Article and Find Full Text PDFDalton Trans
July 2024
Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, SP, Brazil.
In this work, a polyhedral silsesquioxane (POSS) was used as an engineered drug delivery system for two oxindolimine-copper(II) anticancer complexes, [Cu(isaepy)] and [Cu(isapn)]. The interest in hybrid POSS comes from the necessity of developing materials that can act as adjuvants to improve the cytotoxicity of non-soluble metallodrugs. Functionalization of POSS with a triazole ligand (POSS-atzac) permitted the anchorage of such copper complexes, producing hybrid materials with efficient cytotoxic effects.
View Article and Find Full Text PDFJ Am Chem Soc
May 2024
Department of Chemistry, The University of Manchester Oxford Road, Manchester M13 9PL, U.K.
We investigate actinide covalency effects in two [AnCp] (An = Th, U) complexes recently studied with pulsed electron paramagnetic resonance spectroscopy, using the Hyperion package to obtain relativistic hyperfine coupling constants from relativistic multiconfigurational wave functions. H and C HYSCORE simulations using the computed parameters show excellent agreement with the experimental data, highlighting the accuracy of modern relativistic ab initio methods. The extent of covalency indicated from the calculations on [ThCp] is in agreement with the original report based on traditional spectral fitting methods, while the covalency in [UCp] is found to be previously overestimated.
View Article and Find Full Text PDFJ Phys Chem C Nanomater Interfaces
April 2021
Dipartimento di Chimica, Università di Torino and NIS Centre, Via Pietro Giuria 7, 10125 Torino, Italy.
X-/Q-band electron paramagnetic resonance (EPR) and hyperfine sublevel correlation (HYSCORE) spectroscopies have been employed, in conjunction with density functional theory (DFT) modeling, to determine the location of Crions in SAPO-5 zeotype materials. The interaction of the unpaired electron of the paramagnetic Cr species with Al could be resolved, allowing for the first detailed structural analysis of Cr paramagnetic ions in SAPO materials. The interpretation of the experimental results is corroborated by DFT modeling, which affords a microscopic description of the system investigated.
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