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Yue Y, Dzięgielewska A, Zhang M, Hull S, Krok F, Whiteley RM, Toms H, Malys M, Huang X, Krynski M, Miao P, Yan H, Abrahams I. Local Structure in α-BIMEVOXes (ME = Ge, Sn). CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2023; 35:189-206. [PMID: 36644215 PMCID: PMC9835824 DOI: 10.1021/acs.chemmater.2c03001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 12/11/2022] [Indexed: 06/17/2023]
Abstract
The BIMEVOXes are among the best oxide ion conductors at low and intermediate temperatures. Their high conductivity is associated with local defect structure. In this work, the local structures of two BIMEVOX compositions, Bi2V0.9Ge0.1O5.45 and Bi2V0.95Sn0.05O5.475, are examined using total neutron and X-ray scattering methods, with both compositions exhibiting the ordered α-phase at 25 °C and the disordered γ-phase at 700 °C. While the diffraction data for the α-phase do not allow for the polar (C2) and nonpolar (C2/m) structures to be readily distinguished, measurements of dielectric permittivity suggest the α-phase is weakly ferroelectric in character, consistent with calculations of spontaneous polarization based on a combination of density functional calculations and machine learning methodology. Reverse Monte Carlo (RMC) analysis of total scattering data reveals Ge preferentially adopts tetrahedral geometry at both temperatures, while Sn is found to predominantly adopt octahedral coordination in the α-phase and tetrahedral coordination in the γ-phase. In all cases, V polyhedra are found to consist of tetrahedral, pentacoordinate, and octahedral geometries, as also predicted by the crystallographic analysis and confirmed by 51V solid state NMR spectroscopy. Although similar long-range structures are observed at room temperature, the oxide ion vacancy distributions were found to be quite different between the two studied compositions, with a nonrandom deficiency in vacancy pairs in the second-nearest shell along the ⟨100⟩ tetragonal direction for BIGEVOX10, compared with a long-distance (>8.0 Å) ordering of equatorial vacancies for BISNVOX05. This is attributed to the differences in the preferred coordination geometries of the substituent cations in the two systems. Impedance spectroscopy measurements reveal both compositions show high conductivity in the order of 10-1 S cm-1 at 600 °C.
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Affiliation(s)
- Yajun Yue
- Department
of Chemistry, Queen Mary University of London, Mile End Road, LondonE1 4NS, United
Kingdom
- Institute
of High Energy Physics, Chinese Academy
of Sciences, Beijing100049, China
| | | | - Man Zhang
- School
of Engineering and Materials Science, Queen
Mary University of London, Mile End Road, LondonE1 4NS, United Kingdom
| | - Stephen Hull
- Science
and Technology Facilities Council, ISIS
Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OxonOX11 OQX, United
Kingdom
| | - Franciszek Krok
- Faculty
of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662Warsaw, Poland
| | - Richard M. Whiteley
- Science
and Technology Facilities Council, ISIS
Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OxonOX11 OQX, United
Kingdom
| | - Harold Toms
- Department
of Chemistry, Queen Mary University of London, Mile End Road, LondonE1 4NS, United
Kingdom
| | - Marcin Malys
- Faculty
of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662Warsaw, Poland
| | - Xuankai Huang
- Department
of Chemistry, Queen Mary University of London, Mile End Road, LondonE1 4NS, United
Kingdom
| | - Marcin Krynski
- Faculty
of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662Warsaw, Poland
| | - Ping Miao
- Institute
of High Energy Physics, Chinese Academy
of Sciences, Beijing100049, China
| | - Haixue Yan
- School
of Engineering and Materials Science, Queen
Mary University of London, Mile End Road, LondonE1 4NS, United Kingdom
| | - Isaac Abrahams
- Department
of Chemistry, Queen Mary University of London, Mile End Road, LondonE1 4NS, United
Kingdom
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Montioli R, Paiardini A, Giardina G, Zanzoni S, Cutruzzola F, Cellini B, Borri Voltattorni C. R180T variant of δ-ornithine aminotransferase associated with gyrate atrophy: biochemical, computational, X-ray and NMR studies provide insight into its catalytic features. FEBS J 2019; 286:2787-2798. [PMID: 30957963 DOI: 10.1111/febs.14843] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 02/21/2019] [Accepted: 04/05/2019] [Indexed: 02/01/2023]
Abstract
Among the over 50 gyrate atrophy-causing mutations of ornithine δ-aminotransferase (OAT), the R180T involves an active site residue located at the dimer interface, which in the crystal structure of OAT complexed with 5-fluoromethylornithine engages a salt bridge with the α-carboxylate of the substrate analogue. Starting from the previous finding that no transaminase activity was detected in CHO-K1 cells expressing the R180T variant, here we try to shed light at the protein level on the structural and/or functional defects of the R180T variant. To this aim, the variant has been cloned, expressed, purified and characterized by a combination of biochemical and structural studies. Although the R180T variant shares a similar overall conformation with the wild-type, its crystal structure solved at 1.8 Ǻ reveals slight structural alterations at the active site and at the dimeric interface. These changes are consistent with the spectroscopic and kinetic results, indicating that the variant, as compared with the wild-type OAT, shows (a) an increased Km value for l-ornithine (l-Orn), (b) an altered pyridoxal 5'-phosphate binding mode and affinity and (c) an increased thermostability. In addition, the R180T mutant exhibits a remarkable loss of catalytic activity and is endowed with the ability to catalyse not only the δ-transamination but also, albeit to a lesser extent, the α-transamination of l-Orn. Overall, these data indicate that the slight structural changes caused by the R180T mutation, preventing a proper collocation of l-Orn at the active site of OAT, are responsible for the notable reduction of the catalytic efficiency. ENZYMES: Ornithine aminotransferase EC 2.6.1.13. DATABASES: 6HX7.pdb.
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Affiliation(s)
- Riccardo Montioli
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Italy
| | - Alessandro Paiardini
- Department of Biochemical Sciences "A. Rossi Fanelli", Sapienza University of Rome, Italy
| | - Giorgio Giardina
- Department of Biochemical Sciences "A. Rossi Fanelli", Sapienza University of Rome, Italy
| | - Serena Zanzoni
- Centro Piattaforme Tecnologiche, University of Verona, Italy
| | - Francesca Cutruzzola
- Department of Biochemical Sciences "A. Rossi Fanelli", Sapienza University of Rome, Italy
| | - Barbara Cellini
- Department of Experimental Medicine, University of Perugia, Italy
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Bresciani G, Bortoluzzi M, Zacchini S, Gabbani A, Pineider F, Marchetti F, Pampaloni G. Synthesis and Structural Characterization of Non‐Homoleptic Carbamato Complexes of V
V
and W
VI
and Their Facile Implantation onto Silica Surfaces. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201701260] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Giulio Bresciani
- University of Pisa Dipartimento di Chimica e Chimica Industriale Via G. Moruzzi 13 56124 Pisa Italy
- Consorzio Interuniversitario per le Reattività Chimiche e la Catalisi (CIRCC) Via Celso Ulpiani 27 70126 Bari Italy
| | - Marco Bortoluzzi
- Consorzio Interuniversitario per le Reattività Chimiche e la Catalisi (CIRCC) Via Celso Ulpiani 27 70126 Bari Italy
- Ca' Foscari University of Venezia Dipartimento di Scienze Molecolari e Nanosistemi Via Torino 155 30170 Mestre (VE) Italy
| | - Stefano Zacchini
- Consorzio Interuniversitario per le Reattività Chimiche e la Catalisi (CIRCC) Via Celso Ulpiani 27 70126 Bari Italy
- University of Bologna Dipartimento di Chimica Industriale “Toso Montanari” Viale Risorgimento 4 40136 Bologna Italy
| | - Alessio Gabbani
- University of Pisa Dipartimento di Chimica e Chimica Industriale Via G. Moruzzi 13 56124 Pisa Italy
| | - Francesco Pineider
- University of Pisa Dipartimento di Chimica e Chimica Industriale Via G. Moruzzi 13 56124 Pisa Italy
- Consorzio Interuniversitario per le Reattività Chimiche e la Catalisi (CIRCC) Via Celso Ulpiani 27 70126 Bari Italy
| | - Fabio Marchetti
- University of Pisa Dipartimento di Chimica e Chimica Industriale Via G. Moruzzi 13 56124 Pisa Italy
- Consorzio Interuniversitario per le Reattività Chimiche e la Catalisi (CIRCC) Via Celso Ulpiani 27 70126 Bari Italy
| | - Guido Pampaloni
- University of Pisa Dipartimento di Chimica e Chimica Industriale Via G. Moruzzi 13 56124 Pisa Italy
- Consorzio Interuniversitario per le Reattività Chimiche e la Catalisi (CIRCC) Via Celso Ulpiani 27 70126 Bari Italy
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