Structural Characterization of MCM-41 over a Wide Range of Length Scales

Langmuir ◽  
1999 ◽  
Vol 15 (8) ◽  
pp. 2809-2816 ◽  
Author(s):  
C. G. Sonwane ◽  
S. K. Bhatia
Keyword(s):  
Structural Characterization ◽  
Length Scales ◽  
Wide Range ◽  
Mcm 41

scholarly journals Solid-State NMR Techniques for the Structural Characterization of Cyclic Aggregates Based on Borane–Phosphane Frustrated Lewis Pairs

Molecules ◽  
2020 ◽  
Vol 25 (6) ◽  
pp. 1400 ◽  
Author(s):  
Robert Knitsch ◽  
Melanie Brinkkötter ◽  
Thomas Wiegand ◽  
Gerald Kehr ◽  
Gerhard Erker ◽  
...  
Keyword(s):  
Solid State ◽  
Structural Characterization ◽  
Solid State Nmr ◽  
Magic Angle ◽  
Frustrated Lewis Pairs ◽  
Wide Range ◽  
Nmr Techniques ◽  
Nmr Methods ◽  
Lewis Pairs

Modern solid-state NMR techniques offer a wide range of opportunities for the structural characterization of frustrated Lewis pairs (FLPs), their aggregates, and the products of cooperative addition reactions at their two Lewis centers. This information is extremely valuable for materials that elude structural characterization by X-ray diffraction because of their nanocrystalline or amorphous character, (pseudo-)polymorphism, or other types of disordering phenomena inherent in the solid state. Aside from simple chemical shift measurements using single-pulse or cross-polarization/magic-angle spinning NMR detection techniques, the availability of advanced multidimensional and double-resonance NMR methods greatly deepened the informational content of these experiments. In particular, methods quantifying the magnetic dipole–dipole interaction strengths and indirect spin–spin interactions prove useful for the measurement of intermolecular association, connectivity, assessment of FLP–ligand distributions, and the stereochemistry of adducts. The present review illustrates several important solid-state NMR methods with some insightful applications to open questions in FLP chemistry, with a particular focus on supramolecular associates.

scholarly journals Kinetic and Structural Characterization of the First B3 Metallo-β-Lactamase with an Active Site Glutamic Acid

2021 ◽  
Author(s):  
Liam A. Wilson ◽  
Esmée G. Knaven ◽  
Marc T. Morris ◽  
Marcelo Monteiro Pedroso ◽  
Christopher J. Schofield ◽  
...  
Keyword(s):  
Glutamic Acid ◽  
Structural Characterization ◽  
Active Site ◽  
Structural Diversity ◽  
Kinetic Properties ◽  
Design Studies ◽  
Degrading Bacterium ◽  
Active Site Motif ◽  
Wide Range

The structural diversity in metallo-β-lactamases (MBLs), especially in the vicinity of the active site, has been a major hurdle in the development of clinically effective inhibitors. Representatives from three variants of the B3 MBL subclass, containing either the canonical HHH/DHH active site motif (present in the majority of MBLs in this subclass) or the QHH/DHH (B3-Q) or HRH/DQK (B3-RQK) variations were reported previously. Here, we describe the structure and kinetic properties of the first example (SIE-1) of a fourth variant containing the EHH/DHH active site motif (B3-E). SIE-1 was identified in the hexachlorocyclohexane-degrading bacterium Sphingobium indicum , and kinetic analyses demonstrate that although it is active against a wide range of antibiotics its efficiency is lower than that of other B3 MBLs, but with improved efficiency towards cephalosporins relative to other β-lactam substrates. The overall fold of SIE-1 is characteristic of the MBLs; the notable variation is observed in the Zn1 site due to the replacement of the canonical His116 by a glutamate. The unusual preference of SIE-1 for cephalosporins and its occurrence in a widespread environmental organism suggests scope for increased MBL-mediated β-lactam resistance. It is thus relevant to include SIE-1 into MBL inhibitor design studies to widen the therapeutic scope of much needed anti-resistance drugs.

Investigation of the Structural Characterization of Mesoporous Molecular Sieves MCM-41 from Sepiolite

2007 ◽  
Vol 90 (3) ◽  
pp. 957-961 ◽  
Author(s):  
Shengming Jin ◽  
Guanzhou Qiu ◽  
Fei Xiao ◽  
Yan Chang ◽  
Cuifeng Wan ◽  
...  
Keyword(s):  
Structural Characterization ◽  
Molecular Sieves ◽  
Mesoporous Molecular Sieves ◽  
Mcm 41

scholarly journals Structural characterization of ice XIX as the second polymorph related to ice VI

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tobias M. Gasser ◽  
Alexander V. Thoeny ◽  
A. Dominic Fortes ◽  
Thomas Loerting
Keyword(s):  
High Resolution ◽  
Structural Characterization ◽  
Structural Model ◽  
Neutron Powder Diffraction ◽  
Ex Situ ◽  
Nucleation Kinetics ◽  
Icy Moons ◽  
First Order ◽  
Wide Range

AbstractIce polymorphs usually appear as hydrogen disorder-order pairs. Ice VI has a wide range of thermodynamic stability and exists in the interior of Earth and icy moons. Our previous work suggested ice β-XV as a second polymorph deriving from disordered ice VI, in addition to ice XV. Here we report thermal and structural characterization of the previously inaccessible deuterated polymorph using ex situ calorimetry and high-resolution neutron powder diffraction. Ice β-XV, now called ice XIX, is shown to be partially antiferroelectrically ordered and crystallising in a √2×√2×1 supercell. Our powder data recorded at subambient pressure fit best to the structural model in space group $$P\bar 4$$ P 4 ¯ . Key to the synthesis of deuterated ice XIX is the use of a DCl-doped D2O/H2O mixture, where the small H2O fraction enhances ice XIX nucleation kinetics. In addition, we observe the transition from ice XIX to its sibling ice XV upon heating, which proceeds via a transition state (ice VI‡) containing a disordered H-sublattice. To the best of our knowledge this represents the first order-order transition known in ice physics.

scholarly journals In situ structural characterization of ageing kinetics in aluminum alloy 2024 across angstrom-to-micrometer length scales

2016 ◽  
Vol 111 ◽  
pp. 385-398 ◽  
Author(s):  
Fan Zhang ◽  
Lyle E. Levine ◽  
Andrew J. Allen ◽  
Carelyn E. Campbell ◽  
Adam A. Creuziger ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Structural Characterization ◽  
Length Scales ◽  
Aluminum Alloy 2024

scholarly journals Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience

2017 ◽  
Vol 13 ◽  
pp. 1145-1167 ◽  
Author(s):  
Serge Pérez ◽  
Daniele de Sanctis
Keyword(s):  
Synchrotron Radiation ◽  
Structural Characterization ◽  
Crystalline State ◽  
Structural Diversity ◽  
Interacting Proteins ◽  
X Ray ◽  
Wide Range ◽  
Kinetics Of

Synchrotron radiation is the most versatile way to explore biological materials in different states: monocrystalline, polycrystalline, solution, colloids and multiscale architectures. Steady improvements in instrumentation have made synchrotrons the most flexible intense X-ray source. The wide range of applications of synchrotron radiation is commensurate with the structural diversity and complexity of the molecules and macromolecules that form the collection of substrates investigated by glycoscience. The present review illustrates how synchrotron-based experiments have contributed to our understanding in the field of structural glycobiology. Structural characterization of protein–carbohydrate interactions of the families of most glycan-interacting proteins (including glycosyl transferases and hydrolases, lectins, antibodies and GAG-binding proteins) are presented. Examples concerned with glycolipids and colloids are also covered as well as some dealing with the structures and multiscale architectures of polysaccharides. Insights into the kinetics of catalytic events observed in the crystalline state are also presented as well as some aspects of structure determination of protein in solution.

scholarly journals Structural Characterization of Octahedral Sheet in Dioctahedral Smectites by Thermal Analysis

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 347
Author(s):  
Xiaoli Wang ◽  
Yan Li ◽  
Hejing Wang
Keyword(s):  
Thermal Analysis ◽  
Structural Characterization ◽  
Iron Content ◽  
Octahedral Sheet ◽  
Wide Range ◽  
Cis And Trans ◽  
Octahedral Cations ◽  
Derivative Thermogravimetry ◽  
Main Factor

The structures of octahedral sheets of dioctahedral phyllosilicates show cis-vacant (cv) and trans-vacant (tv) configurations due to the different distributions of the octahedral cations over cis- and trans-sites. On the basis of the different dehydroxylation temperatures, a thermal analysis is an effective method used to identify the cv and tv configurations of an octahedral sheet in dioctahedral smectites. The proportions of cv and tv configurations were determined by fitting the derivative thermogravimetry (DTG) curves. A wide range of cv and tv proportions were detected in the samples. The dehydroxylation temperatures of samples consisting of cv configuration are about 150 to 200 °C higher than those consisting of tv configurations. The samples were classified as tv varieties when octahedral Fe3+ > 0.46 mol/FU, and the pure tv dioctahedral smectites were found when Fe3+ > 1.8 mol/FU. A clear linear relationship was found between the content of octahedral Fe3+ and Al3+ and the proportion of cv and tv configurations. The substitution of Al3+ by Fe3+ in the octahedral sheets is the main factor for the formation of tv varieties. There was no relationship detected between the layer charge density, octahedral Mg2+ content, and the proportion of tv and cv. The present results indicate that the iron content has a significant effect on the structure of the octahedral sheet.

scholarly journals Mineral Composition and Structural Characterization of the Clinoptilolite Powders Obtained from Zeolite-Rich Tuffs

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1030
Author(s):  
Ewelina Pabiś-Mazgaj ◽  
Tomasz Gawenda ◽  
Paweł Pichniarczyk ◽  
Agata Stempkowska
Keyword(s):  
Mineral Composition ◽  
Structural Characterization ◽  
Raw Materials ◽  
Wide Spectrum ◽  
Mineral Processing ◽  
Thin Plates ◽  
X Ray ◽  
Wide Range ◽  
The World

Clinoptilolite is a precious zeolite mineral that has the most comprehensive physicochemical properties among all the zeolite group minerals. Due to these unique properties, clinoptilolite has a wide range of applications in many different industries. In Poland, the clinoptilolite occurs only as an accompanying mineral in the sedimentary rocks nearby Rzeszów. In Europe, the abundant clinoptilolite-bearing deposits are located in Slovakia and Ukraine, where clinoptilolite mineralization occurs in the volcanic tuffs. Due to clinoptilolite’s rare performance, it is extremely crucial to manage its deposits in a complementary manner. In this paper, the mineralogical and structural characterization of the clinoptilolite powders obtained by mineral processing of the clinoptilolite-rich tuffs from Slovakia and Ukraine deposits were discussed. The scope of research covered determination of the mineral composition of the tuffs, structural analysis of the clinoptilolite crystals, as well as textural and physical properties of the powders obtained by mineral processing of the tuffs. In addition, this paper includes the comparative study of the most significant zeolite deposits in the world and investigated clinoptilolite-rich tuffs. A wide spectrum of methods was used: X-ray powder diffraction (XRD), thermal analysis (DSC, TG), X-ray fluorescence (XRF), optical microscopy, Scanning Electron Microscopy (SEM-EDS), the laser diffraction technique, and low-temperature nitrogen adsorption/desorption. The test results indicated that the major component of the tuffs is clinoptilolite, which crystallized in the form of very fine-crystalline thin plates. The clinoptilolite mineralization in the Ukrainian and Slovakian tuffs exhibited a strong resemblance to the clinoptilolite crystals in Yemeni and Turkish tuffs. With respect to the mineral composition, the investigated tuffs showed excellent conformity with the Miocene white tuffs from Romania. The Ukrainian and Slovakian tuffs do not reveal the presence of the clay minerals, which is quite common for naturally occurring zeolite-rich rocks in various deposits in the world. The textural features together with mineral composition of the investigated samples incline that they are potentially suitable raw materials for the sorbent of petroleum compounds. Moreover, the obtained results can be useful indicators with respect to the crushing and compaction susceptibility of the Ukrainian and Slovakian clinoptilolite-rich tuffs.

scholarly journals Comprehensive analytical and structural characteristics of methyl 3,3-dimethyl-2-(1-(pent-4-en-1-yl)-1H-indazole-3-carboxamido)butanoate (MDMB-4en-PINACA)

2021 ◽  
Author(s):  
Michal P. Dybowski ◽  
Piotr Holowinski ◽  
Rafal Typek ◽  
Andrzej L. Dawidowicz
Keyword(s):  
Mass Spectrometry ◽  
Structural Characterization ◽  
Density Functional ◽  
Gas Chromatography Mass Spectrometry ◽  
X Ray Diffraction ◽  
Absorption Bands ◽  
X Ray ◽  
Chromatography Mass Spectrometry ◽  
Wide Range

Abstract Purpose The purpose of the study was to evaluate a complete analytical and structural characterization of methyl 3,3-dimethyl-2-(1-(pent-4-en-1-yl)-1H-indazole-3-carboxamido)butanoate (MDMB-4en-PINACA), a novel synthetic cannabinoid being the analogue of 5F-ADB. Methods The compound was analyzed by gas chromatography–mass spectrometry (GC–MS), high-resolution liquid chromatography–mass spectrometry (LC–MS), X-ray diffraction and spectroscopic methods, such as nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopies. To derive MDMB-4en-PINACA molecular geometry and to assign infrared absorption bands, quantum calculations with the employment of density functional theory were also used. Results We present a wide range of chromatographic and spectroscopic data supported with theoretical calculations allowing to identify MDMB-4en-PINACA. Conclusions To our knowledge, this is the first report presenting a comprehensive analytical and structural characterization of MDMB-4en-PINACA obtained by 1D and 2D NMR, GC–MS, LC–MS(/MS), attenuated total reflection-FTIR spectroscopy, powder X-ray diffraction and quantum chemical calculations. The presented results not only broaden the knowledge about this psychoactive substance but also are useful for forensic and clinical purposes.

Sign in / Sign up

Export Citation Format

Share Document