Wide-line NMR Studies Research Articles

Wide-line NMR and DSC studies on intrinsically disordered p53 transactivation domain and its helically pre-structured segment.

Wide-line 1H NMR intensity and differential scanning calorimetry measurements were carried out on the intrinsically disordered 73-residue full transactivation domain (TAD) of the p53 tumor suppressor protein and two peptides: one a wild type p53 TAD peptide with a helix pre-structuring property, and a mutant peptide with a disabled helix-forming propensity. Measurements were carried out in order to characterize their water and ion binding characteristics. By quantifying the number of hydrate water molecules, we provide a microscopic description for the interactions of water with a wild-type p53 TAD and two p53 TAD peptides. The results provide direct evidence that intrinsically disordered proteins (IDPs) and a less structured peptide not only have a higher hydration capacity than globular proteins, but are also able to bind a larger amount of charged solute ions. [BMB Reports 2016; 49(9): 497-501]

Elucidation of Structure and Dynamics in Solid Octafluoronaphthalene from Combined NMR, Diffraction, And Molecular Dynamics Studies

X-ray diffraction (XRD), molecular dynamics simulations (MD), and (19)F NMR have been used to investigate structure and dynamics in solid octafluoronaphthalene, C(10)F(8). Two distinct processes are observed via measurements of (19)F relaxation times as a function of temperature; a faster process from T(1) relaxation with a correlation time of the order of ns at ambient temperature (fitting to Arrhenius-type parameters E(a) = 20.6 +/- 0.4 kJ mol(-1) and tau(0) = 8 +/- 1 x 10(-14) s) and a much slower process from T(1rho) relaxation with a correlation time of the order of mus (fitting to E(a) = 55.1 +/- 1.3 kJ mol(-1) and tau(0) = 4 +/- 2 x 10(-16) s). Atomistic molecular dynamics reveals the faster process to involve a small angle jump of 40 degrees of the molecules, which is in perfect agreement with the X-ray diffraction study of the material at ambient temperature. The MD study reveals the existence of more extreme rotations of the molecules, which are proposed to enable the full rotation of the octafluoronaphthalene molecules. This explains both the T(1rho) results and previous wide-line (19)F NMR studies. The experimental measurements (NMR and XRD) and the MD computations are found to be strongly complementary and mutally essential. The reasons why a process on the time scale of microseconds, and associated with such a large activation barrier, can be accessed via classical molecular dynamics simulations are also discussed.

Exploring the limits of 73Ge solid-state NMR spectroscopy at ultrahigh magnetic field

The ultrahigh field natural abundance (73)Ge solid-state wide-line NMR study of germanium dichloride complexed with 1,4-dioxane and tetraphenylgermane yields the largest (73)Ge quadrupolar coupling constant determined by NMR spectroscopy to date and the first direct observation of (73)Ge chemical shift anisotropy.

Wide-Line 1H NMR and DSC study of phase states of mesomorphic states of 4′-n-alkoxy-4-biphenylcarbonitrile mesogens (n = 3 and 7)

4′-(Propyloxy)-4-cyanobiphenyl (3OCB) and 4′-(heptyloxy)-4-cyanobiphenyl (7OCB) have been studied in the temperature range 20–80°C by wide-line 1H NMR and DSC. The 1H NMR line shapes, half-widths, and second moments, as well as the relaxation characteristics of separate lines, are discussed. The DSC data are compared with the specific features of mesogenic transformations of these homologues and 1H NMR data. At certain temperatures depending on the composition of alkyl moieties, a dynamically disordered fraction of molecules appear in solid crystals. These molecules are involved in the thermotropic transitions of 3OCB to isotropic liquid and of 7OCB to nematic liquid crystal. The temperature ranges, stabilities, and other characteristics of the transitions of 3OCB to isotropic liquid and of 7OCB to nematic liquid crystal were determined.

Wide-line 1H NMR study of mesomorphic states of 4′-(octyloxy)-4-biphenylcarbonitrile

A sample of 4′-(octyloxy)-4-cyanobiphenyl (8OCB) was studied in the temperature range −60–80°C by wide-line 1H NMR. The line shapes, half-widths, and second moments were determined. For the smectic phase of 8OCB, the relaxation times T1 and T2, the correlation time τc, and the degree of order were estimated. The 1H NMR spectral patterns and characteristics were found to be quite different for the crystalline, smectic, and nematic phases of 8OCB, which makes it possible to reliably identify the corresponding transitions and assess the molecular dynamics and molecular order of a structure. The temperature ranges, stability conditions, and other characteristics of the liquid crystalline phases that form on heating 8OCB were determined.

Wide-line 1H NMR study of 4′-(pentyloxy)-4-biphenylcarbonitrile in different phase states

A sample of 4′-(pentyloxy)-4-biphenylcarbonitrile was studied in the temperature range 20–70°C by wide-line 1H NMR. The line shapes, half-widths, and second moments were determined. At 20°C, the spectrum is a broad structureless line, which was split into three components at temperatures above 47°C. This pattern persisted up to 65°C, with the components becoming narrower. Above 68°C, the spectrum rapidly collapses to give a structureless narrow line with a width δH < 0.01 G. Analysis of the spectra and comparison with theoretical calculations made it possible to elucidate the transition of the sample from the crystalline to the nematic and isotropic phases, as well as to determine the temperature range of the stability of the liquid-crystalline phase and the role of rotational mobility of protons of different functional groups and sometimes of these groups as a whole in the mechanisms of phase transitions.

Characterization of the Interface in Polymer−Silica Composites Containing an Acrylic Silane Coupling Agent

Microscopic dynamics of the interfacial layer and macroscopic mechanical properties of [3-(acryloxy)propyl]trimethoxysilane (APMS) at a polymer−silica interface were studied using NMR and three-point bending tests. Wide-line deuterium NMR studies of deuterium-enriched [3-(acryloxy)propyl]trimethoxysilane-d (APMS-d), showed that when chemically bonded to silica, the acrylic group of APMS moved rapidly at the interface with air, more slowly when coated with a poly(methyl methacrylate) (PMMA) overlayer, and slowest when copolymerized with methyl methacrylate. A two-component line shape was found for the coated composite and these were assigned to relative immobile and mobile surface groups. From three-point bend tests, the PMMA/glass-fiber composite, made from glass laminates treated with APMS, had almost two times the flexural strength of a composite made from glass laminates not treated with APMS. Electron micrographs of the fracture surfaces revealed that the untreated fibers were smooth, while those from the APMS-treated glass were rougher, indicating the presence of polymer at the interface.

Wide-Line NMR Studies of the Influence of Solvent Polarity on the Conformation and Dynamics of Silica-Immobilized Alkylamine and Alkylamide Ligands

In the present study, selectively deuterated alkylamine ligands were prepared and subsequently used to modify the surface of porous silica. The resulting material was then reacted with either hexanoyl chloride or heptanoyl chloride to produce the corresponding alkylamide-modified surfaces. The wide-line 2H NMR spectra of the intermediate and final materials were measured in the dry state and in the presence of both protic and aprotic solvents. The shapes of the resulting resonances are complex and are made up of spectrally broad and narrow components with widths in the restricted motion range (i.e., about 40 kHz) and widths characteristic of more motionally dynamic species. The relative contribution of the broad component is dominant in the dry state and in aprotic solvent spectra and is significantly decreased or absent in the spectra collected in polar solvents. These results can be explained via changes in the degree of interfacial hydrogen bonding between the amine and amide groups in the attached lig...

Structure and packing of phosphatidylcholines in lamellar and hexagonal liquid-crystalline mixtures with a nonionic detergent: a wide-line deuterium and phosphorus-31 NMR study

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure and packing of phosphatidylcholines in lamellar and hexagonal liquid-crystalline mixtures with a nonionic detergent: a wide-line deuterium and phosphorus-31 NMR studyRobin L. Thurmond, Doerte Otten, Michael F. Brown, and Klaus BeyerCite this: J. Phys. Chem. 1994, 98, 3, 972–983Publication Date (Print):January 1, 1994Publication History Published online1 May 2002Published inissue 1 January 1994https://doi.org/10.1021/j100054a038RIGHTS & PERMISSIONSArticle Views172Altmetric-Citations39LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts

The interaction of vanadia with sepiolite. Structural studies by 51V solid-state NMR and Raman spectroscopy

The interaction of vanadium with sepiolite, a layered magnesium silicate used to stabilize cracking catalysts against metal contaminants in crude oils, is investigated. To this end, field-dependent 51IV wideline, magic-angle-spinning (MAS), and nutation NMR studies, together with X-ray diffraction (XRD) and laser Raman spectroscopy (LRS) results, are reported on sepiolite samples impregnated with a solution of vanadyl napthenate in benzene. These results are discussed in connection with benchmark NMR data of crystallographically well-defined model compounds in the M9O-V 2O 5 system. When heated near 760°C in the presence of steam, sepiolite decomposes into enstatite (MgSiO 3) and silica. If the hydrothermal treatment is repeated in the presence of vanadium, a disordered microcrystalline phase of α-Mg 2V 2O 7 forms. Steam treatment at higher temperatures results in the formation of β-Mg 2V 2O 7. In addition, all samples examined contain an amorphous surface phase. Based on 51V nutation NMR spectroscopy, this amorphous constituent is inferred to have a structural environment similar to β-Mg 2V 2O 7. An MgV 2O 6-like, distorted octahedral environment is present only in samples with very high surface coverages and can be suppressed by choosing multiple-step over single-step impregnation.

Synthesis and wide-line NMR studies of α-deuterated polyacrylates and polyacrylonitrile

Synthesis and wide-line NMR studies of α-deuterated polyacrylates and polyacrylonitrile

Structural studies of covalent nonoxidic glasses: solid state cadmium-113 wide-line, magic angle-spinning, and spin-echo NMR spectroscopy of glasses in the system cadmium arsenide (CdAs2)-cadmium germanium arsenide (CdGeAs2)

{sup 113}Cd wide-line, magic-angle-spinning, and dipolar spin-echo NMR studies of glasses in the system CdGe{sub x}As{sub 2} (0 {le} x {le} 1) suggest a close relationship between the structural organizations of glassy CdAs{sub 2}, CdGeAs{sub 2}, and glasses with intermediate Ge contents. The Cd environments are found to be strikingly different from those present in crystalline CdAs{sub 2} and CdGeAs{sub 2} and most closely resemble those in Cd{sub 3}As{sub 2}. These results are consistent with partial segregation into cadmium-rich and cadmium-depleted domains and implicate the known metastable Cd{sub 3}As{sub 2}-As eutectic in the binary Cd-As phase diagram in governing glass formation in these systems.

Solid state 51V NMR structural studies of vanadium(V) oxide catalysts supported on TiO 2(anatase) and TiO 2(rutile). The influence of surface impurities on the vanadium(V) coordination

Solid state 51V wideline NMR studies show that under ambient conditions the vanadium (V) oxide surface phases on TiO 2(anatase) and TiO 2(rutile) supports predominantly possess distorted-octahedral coordination. However, the coordination environment of vanadia is markedly influenced by the presence of impurities in the support materials. Surface contaminants promote the formation of tetrahedral surface vanadia species, which preferentially form at low surface coverages. The presence of these surface impurities depends on the titania preparation method and overshadows the influence, if any, of the bulk TiO 2 lattice structure (anatase versus rutile). Thus, the strong influence of surface impurities on the V 2O 5/TiO 2 system is most likely responsible for the widely varying claims about differences in the catalytic properties of V 2O 5/TiO 2(anatase) versus V 2O 5/ TiO 2 (rutile) samples.

Neutron diffraction and 1H rigid lattice wide-line NMR studies of powder (K, Bi III, Bi V) pyrochlores

The structure of an A cation-deficient pyrochlore (K, Bi) ⋍1.5Bi 2O ∼6(H 2O) ∼1 has been investigated by powder neutron diffraction using a deuterated sample. Main results of previous X-ray work are confirmed: 25% of A sites are empty; only a small amount of oxygen is found in 8(b) positions, a greater proportion being located in 32(e) positions which are displaced toward the A vacancy. The latter oxygen atoms belongs to a heavy water molecule, the deuterium atoms of which are distributed near 96(g) positions. Proton wide-line nuclear magnetic resonance experiments were performed at 4 K using an undeuterated sample. The experimental NMR spectrum has been simulated using three distinct models, all of them giving an acceptable chemical composition. Only one of these models gives the number of water molecules located in 32(e) sites in agreement with the neutron diffraction results. This same model reveals two other protonated species: water molecules, with short H-H distance, and OH groups belonging to the octahedral network.

Wide line NMR study of some mono- and bis-cyclopentadienyltitanium halides

Wide line NMR study of some mono- and bis-cyclopentadienyltitanium halides

Observation of a plastic crystalline phase in solidMBBA

Wideline and high resolution NMR studies have been carried out in MBBA in its isotropic, nematic and solid phases. Isotropic and nematic spectra correspond to what has been reported earlier. In the solid phase, contrary to expectations, very intense narrow signals similar to signals of the isotropic phase have been observed for the first time at temperatures close to the solid \leftrightarrow nematic phase transition temperature. This indicates rapid reorientational or translational motion in the system. X-ray results, owever, confirm the existence of translational order. The results are interpreted as indicative of the existence of a plastic crystalline phase in MBBA.

NMR and X-ray Investigations of a Plastic Crystalline Phase in MBBA

Wideline and high resolution NMR studies have been carried out on MBBA in its isotropic, nematic and solid phases. Isotropic and nematic phase spectra correspond to what has been reported earlier. In the solid phase, contrary to expectations, very intense narrow signals similar to signals of the isotropic phase have been observed for the first time at temperatures close to the solid \leftrightarrow nematic phase transition temperature. This indicates rapid reorientational or translational motion in the system. The X-ray results however confirm the existence of translational order. The results are interpreted as indicative of the existence of a plastic crystalline phase in MBBA.

Etude par RMN des mecanismes de diffusion du fluor dans Pb 3ZrF 10

19F wide-line and pulsed NMR study of fluorite-type Pb 3ZrF 10 point to the presence of two kinds of fluorine atoms of different mobility. At low temperature only one is mobile with a weakly activated short-range motion (0.14 eV). Above 220 K all fluorine atoms become mobile; the exchange between both types of atoms leads to 1-D conduction with a higher activation energy (0,38 eV). At 380 K a transition in the thermal variation of T 1 (linked to a weak crystallographic transition) is associated with the onset of nearly isotropic diffusion of the fluorine ions.

Etude par résonance magnétique des phénomènes diffusifs dans les phases du système NaFBiF 3

19F and 23Na wide-line NMR studies are reported on NaBiF 4 and the solid solution Na 1− x Bi x F 1+2 x for x = 0.62 and x = 0.68 in the −100° to +200°C temperature range. No sodium mobility could be detected in NaBiF 4, but the mobility is significant in the solid solution. The fluorine motions are weakly activated (0.28 eV) in NaBiF 4 and result only from short-range motion (correlated motions or reorientations). In the solid solution the concentration of mobile fluoride ions increases with temperature. Compared to the values given by complex impedance measurements, the activation energies in this thermal range (0.18 eV for x = 0.62 and 0.20 eV for x = 0.68) may be correlated with phenomena preceding the long range conductivity which appears at higher temperature.

Etude par RMN de la structure dynamique de l'alanate Na 3AlH 6

A low temperature wide-line NMR study has allowed a determination of the AI-H bond lengths in cryolite-type Na 3AlH 6. It was found from the thermal behavior of the proton lines that the |AIH 6| 3− octahedra reorient around a C 4 axis. Starting below 170 K, this rotation can be hindered by lattice defects. Above room temperature it becomes isotropic, and a quick protonic exchange appears. The thermal narrowing of the linewidth and the T 1 and T 1 ρ relaxation times lead to activation energies of about 0.38 eV for axial rotation and 0.51 eV for protonic exchange. The minimum in T 1 is in good agreement with the exchange model. Absorption phenomena, as well as partial decomposition of Na 3AlH 6 during the heat treatments, explain the presence of small amounts of mobil hydrogen.