Neutron protein crystallography: beyond the folding structure of biological macromolecules

Neutron diffraction provides an experimental method of directly locating H atoms in proteins, a technique complementary to ultra-high-resolution X-ray diffraction. Three different types of neutron diffractometers for biological macromolecules have been constructed in Japan, France and the USA, and they have been used to determine the crystal structures of proteins up to resolution limits of 1.5–2.5 Å. Results relating to H-atom positions and hydration patterns in proteins have been obtained from these studies. Examples include the geometrical details of hydrogen bonds, the role of H atoms in enzymatic activity, CH3configuration, H/D exchange in proteins and oligonucleotides, and the dynamical behavior of hydration structures, all of which have been extracted from these structural results and reviewed. Other techniques, such as the growth of large single crystals and a database of hydrogen and hydration in proteins, are described.

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New crystal-chemical data for marécottite

Mineralogical Magazine ◽

10.1180/minmag.2015.079.3.10 ◽

2015 ◽

Vol 79 (3) ◽

pp. 649-660 ◽

Cited By ~ 3

Author(s):

J. Plášil ◽

R. Škoda

Keyword(s):

Charge Balance ◽

X Ray Diffraction ◽

X Ray ◽

Crystal Chemical Data ◽

Different Types ◽

Dominant Member ◽

Network Of Hydrogen Bonds ◽

The Mean ◽

Bond Valence Analysis

AbstractMarécottite, ideally Mg3[(UO2)4O3(OH)(SO4)2]2(H2O)28, a triclinic, Mg-dominant member of the zippeite group, was described originally from a small uranium deposit at La Creusaz in Wallis (Switzerland). It has recently been found at Jáchymov (Czech Republic), where it forms exceptional crystals, up to 0.3 mm across. According to an electron microprobe study of these crystals, marécottite from Jáchymov is chemically similar to the material from the La Creusaz deposit. However, the Jáchymov crystals exhibit more cation substitution (Zn2+ and Mn2+ for Mg2+). The chemical composition of marécottite from Jáchymov corresponds to the empirical formula [(Na0.05K0.07)Σ0.12(Mg1.83Zn0.41Mn0.41Cu0.15Ni0.08)Σ2.88Al0.07]Σ3.07(UO2)8[(SO4)3.77(SiO4)0.21]Σ3.98O6(OH)1.84·28H2O (the mean of four representative spots; calculated on the basis of eight U atoms and 28 H2O per formula unit and 1.84 OH for charge balance). According to single-crystal X-ray diffraction, marécottite from Jáchymov is triclinic, P1, a = 10.8084(2), b = 11.2519(3), c = 13.8465(3) Å, α = 66.222(2), β = 72.424(2), γ = 70.014(2)o, V = 1421.57(6) Å3 and Z = 1. The crystal structure was refined from a highly redundant dataset (30,491 collected reflections) to R1 = 0.0367 for all 7042 unique reflections. The refined structure confirms the previously determined structure for the crystal from the La Creusaz deposit. An extensive network of hydrogen bonds is an important feature that keeps the whole structure together, but the positions of H atoms had not been determined previously. The H-bond scheme proposed based on a detailed bond-valence analysis and the role of different types of molecular H2O in the structure is discussed.

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Microstructural Mechanisms of Fatigue Failure in PA66 Fibers

Materials Science Forum ◽

10.4028/www.scientific.net/msf.560.133 ◽

2007 ◽

Vol 560 ◽

pp. 133-138

Author(s):

J. Martin Herrera-Ramírez ◽

Anthony Bunsell ◽

Philippe Colomban

Keyword(s):

High Performance ◽

Fatigue Loading ◽

Structural Heterogeneity ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

X Ray ◽

Micro Raman Spectroscopy ◽

Nano Structures ◽

Different Types

The behavior of two different types of ultra-high-performance polyamide (PA) 66 fibers under fatigue loading up to failure, and the correlation between the fibers (nano)structures and their structural heterogeneity with fatigue lifetimes, have been studied using scanning electron microscopy, differential scanning calorimetry, wide angle x-ray diffraction and micro-Raman spectroscopy. The role of the microstructure of the fibers in determining fatigue life is presented and the possibility of improving their resistance to fatigue or eliminating the fatigue process will be discussed.

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Protein-induced, previously unidentified twin form of calcite

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.0608584104 ◽

2007 ◽

Vol 104 (18) ◽

pp. 7337-7341 ◽

Cited By ~ 30

Author(s):

B. Pokroy ◽

M. Kapon ◽

F. Marin ◽

N. Adir ◽

E. Zolotoyabko

Keyword(s):

Single Crystal ◽

Crucial Role ◽

Biological Macromolecules ◽

X Ray Diffraction ◽

Mollusc Shell ◽

X Ray ◽

Pinna Nobilis ◽

Twinning Plane ◽

Intracrystalline Protein

Using single-crystal x-ray diffraction, we found a formerly unknown twin form in calcite crystals grown from solution to which a mollusc shell-derived 17-kDa protein, Caspartin, was added. This intracrystalline protein was extracted from the calcitic prisms of the Pinna nobilis shells. The observed twin form is characterized by the twinning plane of the (108)-type, which is in addition to the known four twin laws of calcite identified during 150 years of investigations. The established twin forms in calcite have twinning planes of the (001)-, (012)-, (104)-, and (018)-types. Our discovery provides additional evidence on the crucial role of biological macromolecules in biomineralization.

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Role of the Structure and Electronic Properties of Fe2O3-MoO3 Catalyst on the Dehydration of Isopropyl Alcohol

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19931591 ◽

1993 ◽

Vol 58 (7) ◽

pp. 1591-1599 ◽

Cited By ~ 3

Author(s):

Abd El-Aziz A. Said

Keyword(s):

Active Sites ◽

Isopropyl Alcohol ◽

Oxide Catalyst ◽

Flow System ◽

Charge Carriers ◽

X Ray Diffraction ◽

X Ray ◽

Catalyst Composition ◽

Surface Active

Molybdenum oxide catalyst doped or mixed with (1 - 50) mole % Fe3+ ions were prepared. The structure of the original samples and the samples calcined at 400 °C were characterized using DTA, X-ray diffraction and IR spectra. Measurements of the electrical conductivity of calcined samples with and without isopropyl alcohol revealed that the conductance increases on increasing the content of Fe3+ ions up to 50 mole %. The activation energies of charge carriers were determined in presence and absence of the alcohol. The catalytic dehydration of isopropyl alcohol was carried out at 250 °C using a flow system. The results obtained showed that the doped or mixed catalysts are active and selective towards propene formation. However, the catalyst containing 40 mole % Fe3+ ions exhibited the highest activity and selectivity. Correlations were attempted to the catalyst composition with their electronic and catalytic properties. Probable mechanism for the dehydration process is proposed in terms of surface active sites.

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The role of silver in the crystal structure of pyrargyrite: single crystal X-ray diffraction study

Journal of Geosciences ◽

10.3190/jgeosci.067 ◽

2012 ◽

pp. 161-167 ◽

Cited By ~ 2

Author(s):

F. Laufek ◽

J. Sejkora ◽

M. Dušek

Keyword(s):

Crystal Structure ◽

Single Crystal ◽

Diffraction Study ◽

X Ray Diffraction ◽

X Ray

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Synthesis and Characterization of Clay Polymer Nanocomposites of P(4VP-co-AAm) and Their Application for the Removal of Atrazine

Polymers ◽

10.3390/polym11040721 ◽

2019 ◽

Vol 11 (4) ◽

pp. 721 ◽

Cited By ~ 3

Author(s):

Jorge A. Ramírez-Gómez ◽

Javier Illescas ◽

María del Carmen Díaz-Nava ◽

Claudia Muro-Urista ◽

Sonia Martínez-Gallegos ◽

...

Keyword(s):

Polymer Nanocomposites ◽

Nanocomposite Materials ◽

Synthesis And Characterization ◽

Cross Linking ◽

X Ray Diffraction ◽

Numerous Species ◽

X Ray ◽

Different Types ◽

Synthesized Materials

Atrazine (ATZ) is an herbicide which is applied to the soil, and its mechanism of action involves the inhibition of photosynthesis. One of its main functions is to control the appearance of weeds in crops, primarily in corn, sorghum, sugar cane, and wheat; however, it is very toxic for numerous species, including humans. Therefore, this work deals with the adsorption of ATZ from aqueous solutions using nanocomposite materials, synthesized with two different types of organo-modified clays. Those were obtained by the free radical polymerization of 4-vinylpyridine (4VP) and acrylamide (AAm) in different stoichiometric ratios, using tetrabutylphosphonium persulfate (TBPPS) as a radical initiator and N,N′-methylenebisacrylamide (BIS) as cross-linking agent. The structural, morphological, and textural characteristics of clays, copolymers, and nanocomposites were determined through different analytical and instrumental techniques, i.e., X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Adsorption kinetics experiments of ATZ were determined with the modified and synthesized materials, and the effect of the ratio between 4VP and AAm moieties on the removal capacities of the obtained nanocomposites was evaluated. Finally, from these sets of experiments, it was demonstrated that the synthesized nanocomposites with higher molar fractions of 4VP obtained the highest removal percentages of ATZ.

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Modeling of magneto-conductivity of bismuth selenide: a topological insulator

SN Applied Sciences ◽

10.1007/s42452-021-04397-8 ◽

2021 ◽

Vol 3 (4) ◽

Author(s):

Yogesh Kumar ◽

Rabia Sultana ◽

Prince Sharma ◽

V. P. S. Awana

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Single Crystal ◽

Single Crystals ◽

X Ray Diffraction ◽

Field Range ◽

X Ray ◽

Bulk Carriers ◽

Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

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Microwave-Assisted Fabrication of Mesoporous Silica-Calcium Phosphate Composites for Dental Application

Polymers ◽

10.3390/polym13010053 ◽

2020 ◽

Vol 13 (1) ◽

pp. 53

Author(s):

Adrian Szewczyk ◽

Adrianna Skwira ◽

Marta Ginter ◽

Donata Tajer ◽

Magdalena Prokopowicz

Keyword(s):

Calcium Phosphate ◽

Mesoporous Silica ◽

Octacalcium Phosphate ◽

Precipitation Method ◽

X Ray Diffraction ◽

Coating Solution ◽

X Ray ◽

Microwave Assisted ◽

Calcium Orthophosphates ◽

Different Types

Herein, the microwave-assisted wet precipitation method was used to obtain materials consisting of mesoporous silica (SBA-15) and calcium orthophosphates (CaP). Composites were prepared through immersion of mesoporous silica in different calcification coating solutions and then exposed to microwave radiation. The composites were characterized in terms of molecular structure, crystallinity, morphology, chemical composition, and mineralization potential by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDX). The application of microwave irradiation resulted in the formation of different types of calcium orthophosphates such as calcium deficient hydroxyapatite (CDHA), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP) on the SBA-15 surface, depending on the type of coating solution. The composites for which the progressive formation of hydroxyapatite during incubation in simulated body fluid was observed were further used in the production of final pharmaceutical forms: membranes, granules, and pellets. All of the obtained pharmaceutical forms preserved mineralization properties.

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Crystallization and X-ray diffraction data analysis of human deoxyhaemoglobin A0 fully stripped of any anions

Acta Crystallographica Section D Biological Crystallography ◽

10.1107/s0907444999009750 ◽

1999 ◽

Vol 55 (11) ◽

pp. 1914-1916 ◽

Cited By ~ 11

Author(s):

F. A. V. Seixas ◽

W. F. de Azevedo ◽

M. F. Colombo

Keyword(s):

Diffraction Data ◽

Oxygen Affinity ◽

X Ray Diffraction ◽

Structural Explanation ◽

Human Haemoglobin ◽

X Ray ◽

High Resolution Structure ◽

Allosteric Properties

In this work, initial crystallographic studies of human haemoglobin (Hb) crystallized in isoionic and oxygen-free PEG solution are presented. Under these conditions, functional measurements of the O2-linked binding of water molecules and release of protons have evidenced that Hb assumes an unforeseen new allosteric conformation. The determination of the high-resolution structure of the crystal of human deoxy-Hb fully stripped of anions may provide a structural explanation for the role of anions in the allosteric properties of Hb and, particularly, for the influence of chloride on the Bohr effect, the mechanism by which Hb oxygen affinity is regulated by pH. X-ray diffraction data were collected to 1.87 Å resolution using a synchrotron-radiation source. Crystals belong to the space group P21212 and preliminary analysis revealed the presence of one tetramer in the asymmetric unit. The structure is currently being refined using maximum-likelihood protocols.

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