NMR Nomenclature. Nuclear Spin Properties and Conventions for Chemical Shifts

Harris, Robin K.; Becker, Edwin D.; Menezes, Sônia Maria Cabral de; Goodfellow, R. J.; Granger, Pierre

doi:10.1515/iupac.73.0845

Cited by 62 publications

(97 citation statements)

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“…This corresponds to a 'selective' (solid) pulse time of 2 ls. All measurements were undertaken with a p/2 tip angle along with a recycle delay between excitation pulses of 10 s. All 7 Li centre-of-gravity (apparent) shifts were reported against the IUPAC-recommended primary reference of LiCl (7 M in D 2 O, d 0.0 ppm) [57]. The 29 Si experiments were performed using a Bruker 7 mm HX probe which enabled a MAS frequency of 5 kHz to be implemented.…”

Section: Sem Analyses and Focused Ion Beammentioning

confidence: 99%

“…Flip angle calibration was performed on kaolinite from which a p/2 pulse time of 5.5 ls was measured. All measurements were undertaken with a p/2 tip angle along with a recycle delay between subsequent pulses of 240 s. All 29 Si isotropic chemical shifts were reported against the IUPAC-recommended primary reference of Me 4 Si (1 % in CDCl 3 ; d 0.0 ppm), via a solid kaolinite secondary reference from which the resonance exhibits a known shift of À92:0 ppm [57].…”

Section: Sem Analyses and Focused Ion Beammentioning

confidence: 99%

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Lithium-silicate sol–gel bioactive glass and the effect of lithium precursor on structure–property relationships

Maçon

Jacquemin

Page

et al. 2016

J Sol-Gel Sci Technol

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This work reports the synthesis of lithium-silicate glass, containing 10 mol% of Li 2 O by the sol-gel process, intended for the regeneration of cartilage. Lithium citrate and lithium nitrate were selected as lithium precursors. The effects of the lithium precursor on the sol-gel process, and the resulting glass structure, morphology, dissolution behaviour, chondrocyte viability and proliferation, were investigated. When lithium citrate was used, mesoporous glass containing lithium as a network modifier was obtained, whereas the use of lithium nitrate produced relatively dense glass-ceramic with the presence of lithium metasilicate, as shown by X-ray diffraction, 29 Si and 7 Li MAS NMR and nitrogen sorption data. Nitrate has a better affinity for lithium than citrate, leading to heterogeneous crystallisation from the mesopores, where lithium salts precipitated during drying. Citrate decomposed at a lower temperature, where the crystallisation of lithium-silicate crystal is not thermodynamically favourable. Upon decomposition of the citrate, a solid-state salt metathesis reaction between citrate and silanol occurred, followed by the diffusion of lithium within the structure of the glass. Both glass and glass-ceramic released silica and lithium ions in culture media, but release rate was lower for the glass-ceramic. Both samples did not affect chondrocyte viability and proliferation.Graphical Abstract

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Section: Sem Analyses and Focused Ion Beammentioning

confidence: 99%

Section: Sem Analyses and Focused Ion Beammentioning

confidence: 99%

Lithium-silicate sol–gel bioactive glass and the effect of lithium precursor on structure–property relationships

Maçon

Jacquemin

Page

et al. 2016

J Sol-Gel Sci Technol

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“…22 Solid-State 13 C NMR. Solid state 125.81 MHz 13 C MAS NMR spectroscopy measurements were carried out on a 500 MHz AVANCE III (Bruker) solid-state NMR spectrometer equipped with tripleresonance probes using 4 mm (OD) Zirconia rotors.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Celecoxib Encapsulation in β-Casein Micelles: Structure, Interactions, and Conformation

et al. 2015

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β-Casein is a 24 kDa natural protein that has an open conformation and almost no folded or secondary structure, and thus is classified as an intrinsically unstructured protein. At neutral pH, β-casein has an amphiphilic character. Therefore, in contrast to most unstructured proteins that remain monomeric in solution, β-casein self-assembles into well-defined core-shell micelles. We recently developed these micelles as potential carriers for oral administration of poorly water-soluble pharmaceuticals, using celecoxib as a model drug. Herein we present deep and precise insight into the physicochemical characteristics of the protein-drug formulation, both in bulk solution and in dry form, emphasizing drug conformation, packing properties and aggregation state. In addition, the formulation is extensively studied in terms of structure and morphology, protein/drug interactions and physical stability. Particularly, NMR measurements indicated strong drug-protein interactions and noncrystalline drug conformation, which is expected to improve drug solubility and bioavailability. Small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) were combined for nanostructural characterization, proving that drug-protein interactions lead to well-defined spheroidal micelles that become puffier and denser upon drug loading. Dynamice light scattering (DLS), turbidity measurements, and visual observations complemented the analysis for determining formulation structure, interactions, and stability. Additionally, it was shown that the loaded micelles retain their properties through freeze-drying and rehydration, providing long-term physical and chemical stability. Altogether, the formulation seems greatly promising for oral drug delivery.

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“…These are also important points needed to be taken into account for quantification. The chemical shift standard of 19 F NMR specified by the International Union of Pure and Applied Chemistry (IUPAC) [55] is fluorotrichloromethane (CFCl 3 ), which is a volatile solvent and not suitable for biomedical studies. An alternative to CFCl 3 is sodium trifluoroacetate (CF 3 CO 2 Na or NaTFA; Δδ vs CFCl 3 is À76.530 ppm), which has the advantages of ready availability, cheap cost, nontoxicity, enabling it used as external or internal chemical shift standard in biological investigations [56,57].…”

Section: F 1d Qnmrmentioning

confidence: 99%

Quantitative NMR Studies of Multiple Compound Mixtures

2017

Annual Reports on NMR Spectroscopy

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NMR Nomenclature. Nuclear Spin Properties and Conventions for Chemical Shifts

Cited by 62 publications

References 0 publications

Lithium-silicate sol–gel bioactive glass and the effect of lithium precursor on structure–property relationships

Lithium-silicate sol–gel bioactive glass and the effect of lithium precursor on structure–property relationships

Celecoxib Encapsulation in β-Casein Micelles: Structure, Interactions, and Conformation

Quantitative NMR Studies of Multiple Compound Mixtures

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