PubMed Health⌕ Search

Biomedical subjects

Dominique Massiot

Publications and source records attributed to Dominique Massiot.

At least 19 recordsLinked to original sources
PubMed2006

Three-dimensional through-bond homonuclear-heteronuclear correlation experiments for quadrupolar nuclei in solid-state NMR applied to (27)Al-O-(31)P-O-(27)Al networks.

We present here the first 3D homonuclear/heteronuclear correlation experiment applied to quadrupolar nuclei and making use of the sole scalar J-coupling. This experiment, based on the 2D-Homonuclear-Heteronuclear Single Quantum Correlation (H-HSQC) experiment, uses a relayed transfer from the (27)Al central transition to neighbouring (31)P spins and to the central transition of a second (27)Al. It confirms the correlation map characterizing the two (27)Al and the (31)P NMR signatures of (27)Al-O-(31)P-O-(27)Al chemically bonded molecular motifs.

Algorithms↗
PubMed2006

Two-dimensional one pulse MAS of half-integer quadrupolar nuclei.

We show that the two-dimensional one pulse (TOP) representation of magic-angle spinning nuclear magnetic resonance data of half-integer quadrupolar nuclei has significant advantages over the conventional one-dimensional spectrum. The TOP spectrum, which correlates NMR frequency to spinning sideband order, provides a rapid determination of the number of sites as well as the size of the their quadrupolar coupling. Additionally, synchronous acquisition spectra of the central and satellite transition resonances can be separated by different projections of the TOP spectrum, with higher resolution spectra often found in the satellite transitions projection. A previously perceived problem of centerband aliasing in TOP can be eliminated with an algorithm that uses larger subspectral widths and the sideband order dimension to distinguish centerbands from sidebands.

Journal Article↗
PubMed2006

Through-bond homonuclear correlation experiments in solid-state NMR applied to quadrupolar nuclei in Al-O-P-O-Al chains.

Through-bond homonuclear correlation experiments can be realised in solids between spins of type X, separated by four chemical bonds, in X-O-Y-O-X motifs, provided a J coupling between X and Y exists: central transitions of quadrupolar 27Al spins can be correlated via the J2 scalar coupling between 27Al (X) and 31P (Y) in materials featuring Al-O-P-O-Al motifs.

Journal Article↗
PubMed2006

Toward a better description of gallo-phosphate materials in solid-state NMR: 1D and 2D correlation studies.

We show that weak 2J(71Ga-O-31P), typically approximately 12 Hz in GaPO4, can be used to efficiently establish heteronuclear 31P-71Ga correlation using a MAS HMQC experiment in gallo-phosphate materials. The experiment demonstrated for cristobalite GaPO4 is then applied to Ga(PO3)3, where it allows the differentiation of the signature of three different Ga sites overlapping in the 1D spectrum.

Journal Article↗
PubMed2005

Triple-quantum correlation NMR experiments in solids using J-couplings.

We show that triple-quantum-single-quantum (TQ-SQ) correlation spectra of crystalline and disordered solids can be obtained under MAS using pulse sequences based on through-bond J-couplings. The feasibility of the experiments in coupled spin-1/2 systems is demonstrated for fully 13C-labelled L-alanine and Pb3P4O13 crystalline compounds, considered as model three-spin and four-spin systems, respectively. In the case of phosphate glasses, we show that the obtained TQ-SQ correlation spectra provide an improved description of the glass forming network connectivities and of the chain length distribution in the disordered network.

Alanine↗
PubMed2005

NMR heteronuclear correlation between quadrupolar nuclei in solids.

We show for the first time that it is possible to acquire high-resolution heteronuclear NMR correlation experiments in solid state between second-order-broadened half integer quadrupolar nuclei (i.e., 27Al and 17O) using the scalar J-coupling. The sensitivity of the experiment is dramatically improved at high fields (gain proportional to the fourth power of the principal field) with a combination of signal enhancement techniques. This turns a challenging experiment into a real tool. We apply this experiment to characterize a calcium aluminate glass in which we prove the presence of tricluster mu3 oxygen sites and describe the signature of their directly bonded aluminum sites. Applications involve a large range of possible pairs of quadrupolar nuclei in different materials, such as glasses, porous or mesoporous framework materials, zeolites, hybrid organic-inorganic, and bioinvolved materials.

Crystallization↗
PubMed2005

Through-space contributions to two-dimensional double-quantum J correlation NMR spectra of magic-angle-spinning solids.

A routinely used assumption when interpreting two-dimensional NMR spectra obtained with a commonly used double-quantum (DQ) magic-angle-spining (MAS) pulse sequence referred to as the refocused incredible natural abundance double-quantum transfer experiment (INADEQUATE) [A. Lesage, M. Bardet, and L. Emsley, J. Am. Chem. Soc. 121, 10987 (1999)] has been that correlation peaks are only observed for pairs of nuclei with a through-bond connectivity. The validity of this assumption is addressed here by theory, experiment, and computer simulations. If the isotropic chemical shifts of the two nuclei are different and the MAS frequency is far from rotational resonance, the theoretical description demonstrates that DQ correlation peaks are indeed indicative of a J coupling. However, if the isotropic chemical shifts are the same, it is shown that DQ peaks can appear for pairs of nuclei even in the absence of a through-bond J coupling. These peaks appear in the specific case of a pair of nuclei with a nonzero through-space dipole-dipole coupling and chemical shift anisotropy tensors having different principal magnitudes or orientations, provided that the MAS frequency is comparable to or smaller than the chemical shift anisotropies. Experimental 31P spectra recorded on a sample of TiP2O7 and computer simulations show that the magnitude of these anomalous peaks increases with increasing B0 magnetic field and that they decrease with increasing MAS frequency. This behavior is explained theoretically.

Journal Article↗
PubMed2005

Reactivity of titanium oxo ethoxo cluster [Ti16O16(OEt)32]. Versatile precursor of nanobuilding block-based hybrid materials.

Oxo alcoxo metallic clusters can be employed as inorganic nanobuilding blocks to obtain well-defined organic-inorganic hybrid materials. A better understanding of the surface reactivity of the clusters should allow optimization of the elaboration of hybrid materials through a better control of the hybrid interface. The oxo alcoxo cluster Ti(16)O(16)(OEt)32 presents a shell of labile ethoxy groups that can be selectively transalcoholyzed with preservation of the titanium oxo core, leading to new oxo alcoxo clusters Ti(16)O(16)(OEt)32-x(OR)x (R: alkyl, phenyl, styrenic, etc. groups). The reactivity of the Ti(16)O(16)(OEt)32 cluster toward aliphatic and aromatic alcohols is investigated to determine both the kinetics and the number of substituted titanium atoms, which are strongly dependent on the nature of the alcohol. Characterization of the organic modification of the cluster is performed in situ by liquid (13)C NMR measurements, using the molecular structures of two new clusters, Ti(16)O(16)(OEt)28(OnPr)4 and Ti(16)O(16)(OEt)(24)(OnPr)(8) (OnPr = propoxy groups), as references. The structures of these clusters have been established using single-crystal X-ray diffraction. Moreover, a complete spectroscopic assignment of each ethoxy group is proposed after combining crystallographic data, (13)C NMR T(1) relaxation measurements, and (1)H-(1)H, (1)H-(13)C 2D NMR experiments. Finally, the cluster is functionalized with polymerizable ligands via transalcoholysis and transesterification reactions using hydroxystyrene and acetoxystyrene.

Journal Article↗
PubMed2005

Tracing the reactive melting of glass-forming silicate batches by in situ 23Na NMR.

The kinetics of the reaction of batches of powdered quartz and sodium carbonate was studied by in situ (23)Na nuclear magnetic resonance (NMR) spectroscopy using a laser-heated probe. We show for the first time that the technique allows one to study solid-state reactions at high temperatures with good time resolution and without the risk of quenching artifacts. The reaction is controlled by solid-state Na(+) diffusion across the grain interface. Independent of the batch composition, the first reaction product is crystalline sodium metasilicate, Na(2)SiO(3), even if the temperature is high enough for much of the composition space between silica and metasilicate to be above the equilibrium liquidus. Fast Na(+) diffusion allows the reaction front to cross the grain interface and form the solid product before liquid intermediate equilibrium products can be formed. This purely solid-state reaction slows down as the thickness of the interface increases; the reaction is more deceleratory than published models suggest. If excess quartz is present, it reacts in a second step involving a liquid film wetting the excess grains. Once this reaction has started, it pulls the reaction into the thermodynamic regime, which leads to an increase even in the rate of the first step leading to intermediate solid metasilicate.

Journal Article↗
PubMed2005

17O NMR in room temperature phase of La2Mo2O9 fast oxide ionic conductor.

A room temperature (17)O NMR study of La(2)Mo(2)O(9), a fast oxide ionic conductor exhibiting a phase transition at 580 degrees C between a low-temperature alpha-phase and a high-temperature beta-phase, is presented. Four partly overlapping quasi-continuous distributions of oxygen sites are evidenced from 1D magic angle spinning (MAS) and 2D triple quantum MAS NMR experiments. They can be correlated with the three oxygen sites O1, O2 and O3 of the high-temperature crystal structure. The low-temperature phase is characterized by two distributed sites of type O1, which proves that the symmetry is lower than in the cubic high-temperature phase. Two-dimensional experiments show that there is no dynamic exchange process, on the NMR time-scale, between the different oxygen sites at room temperature, which agrees well with conductivity results.

Journal Article↗
PubMed2005

Solid-state NMR study of ureidopyrimidinone model compounds.

High-resolution (1)H and (15)N{(1)H} solid-state NMR experiments were conducted on two ureidopyrimidinone model compounds: dimeric 2-butylureido-6-methyl-4-pyrimidinone (1) and its bifunctional analogue N,N-1,6-hexanediyl(2-ureido-6-methyl-4-pyrimidinone) (4). High magic angle spinning rates and (1)H decoupling schemes were used to increase the proton spectral resolution. Upon heating 1 to 440 K, an increase in mobility was observed for non-hydrogen-bonded protons; the dimer remained in keto tautomeric form, which is capable of much stronger intermolecular hydrogen bonding than the enol tautomer. From these findings, it was concluded that this ureidopyrimidinone moiety should allow the design of strongly bonded molecular assemblies whose thermal stability compares favourably with that of conventional engineering polymers.

Journal Article↗
PubMed2005

Novel biomaterials for bisphosphonate delivery.

One type of gem-bisphosphonate (Zoledronate) has been chemically associated onto calcium phosphate (CaP) compounds of various compositions. For that purpose, CaP powders of controlled granulometry have been suspended in aqueous Zoledronate solutions of variable concentrations. Using mainly (31)P NMR spectroscopy, two different association modes have been observed, according to the nature of the CaP support and/or the initial concentration of the Zoledronate solution. beta-tricalcium phosphate (beta-TCP) and mixtures of hydroxyapatite and beta-TCP (BCPs) appear to promote Zoledronate-containing crystals formation. On the other hand, at concentrations <0.05 mol l(-1) CDAs (calcium deficients apatites) seem to undergo chemisorption of the drug through a surface adsorption process, due to PO(3) for PO(4) exchange, that is well described by Freundlich equations. At concentrations >0.05 mol l(-1), crystalline needles of a Zoledronate complex form onto the CDAs surface. The ability of such materials to release Zoledronate, resulting in the inhibition of osteoclastic activity, was shown using a specific in vitro bone resorption model.

Animals↗
PubMed2003

Synthesis and solid-state NMR studies of p-vinylbenzylphosphonic acid.

P-Vinylbenzylphosphonic acid (2) was synthesized and crystallized in two phases A and B. The latter phase was easily converted into the former. Both phases were investigated by IR and solid-state (31)P and (1)H NMR spectroscopy, and X-ray crystallography. The use of recently developed NMR methods has enabled us to increase the usually poor resolution of solid-state (1)H spectra. This gave additional insights on the proton environments. In particular, two dimensional 2D (1)H-(31)P heteronuclear correlation (HETCOR) experiments, incorporating a Lee-Golburg homonuclear decoupling scheme, allowed description of the mixture of phase A and B.

Journal Article↗
PubMed2003

Multi-scale NMR characterisation of mesostructured materials using 1H-->13C through-bond polarisation transfer, fast MAS, and 1H spin diffusion.

A NMR method for the characterisation of materials at different length scales, robust and simple to implement, is presented. It combines selection of 1H-13C pairs by a through-bond polarisation transfer (INEPT here) and exploration of larger distances by the introduction of 1H spin diffusion. This characterisation method is well adapted to the highest MAS rates and takes benefits of it. The effect of 1H dephasing on the efficiency of the 1H-->13C through-bond polarisation transfer is determined. This allows consecutively the quantification of signals. Mesostructured spherical silica-based particles containing CTA+ cations were studied by this multi-scale characterisation method. Contrasted spin diffusion curves were found and qualitatively explained by differences in terms of mobility and spatial distributions.

Carbon Isotopes↗