389 research outputs found
supplementary-HLE_Schedule – Supplemental material for Health-related life events in patients with somatic symptom disorders: A case control study
No full textSupplemental material, supplementary-HLE_Schedule for Health-related life events in patients with somatic symptom disorders: A case control study by Balaswamy Reddy, Santosh Kumar Chaturvedi, Geetha Desai, Narayana Manjunatha and Srinivas Guruprasad in International Journal of Social Psychiatry</p
Polyphenols fingerprinting in olive oils through maximum-quantum NMR spectroscopy
No full textAn NMR protocol based on multiple-quantum spectroscopy is presented for an analytical screening of polyphenols in olive oils. Three Italian olive oils with different total polyphenols content were used as study case. A total of 24 compounds were identified as follows: 1 polyphenol in the 5Q–1Q, 15 more in the 4Q–1Q, and 8 components in the 3Q–1Q spectra, consisting of organic phenols, secoiridoids, lignans, and flavonols. In the three Italian olive oils investigated here, the polyphenols profile turned out to be significantly different, with specific characteristics going beyond simple considerations based on the total polyphenol content. The approach presented here can be easily extended for rapid qualitative and semi-quantitative screening of the polyphenol composition in many food products
Interplay of non-covalent interactions in ribbon-like guanosine self-assembly : a NMR crystallography study
No full textA NMR crystallography study shows how intermolecular NH...O, NH...N, OH...N, OH...O and CH–π interactions stabilize the ribbon-like supramolecular structures of three different guanosine derivatives; guanosine dihydrate (G), 3/, 5/–O– dipropanolyl deoxyguanosine (dGC(3)2) and 3/, 5/ –O– isopropylideneguanosine hemihydrate (Gace). Experimental solid-state 1H NMR spectra obtained at 20 T using fast Magic-Angle Spinning (MAS), here at 75 kHz, are presented for a dihydrate of G. For each guanosine derivative, the role of specific interactions is probed by means of NMR chemical shifts calculated using the Density Functional Theory (DFT) Gauge-Including Projector-Augmented Wave (GIPAW) approach for the full crystal and extracted isolated single molecules. Specifically, the isolated molecule to full crystal transformations result in net changes in the GIPAW calculated 1H NMR chemical shifts of up to 8 ppm for OH...O, up to 6.5 ppm for NH...N and up to 4.6 ppm for NH...O hydrogen bonds; notably, the presence of water molecules in G and Gace reinforces the molecular stacking through strong OH...O hydrogen bonds. The sugar conformations are markedly different in G, dG(C3)2 and Gace, and it is shown that the experimental 13C solid-state NMR chemical shift at the C8 position is a reliable indicator of a ‘syn’ (> 135 ppm) or ‘anti’ (< 135 ppm) conformer
Co-existence of distinct supramolecular assemblies in solution and in the solid state
No full textThe formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G-quartet based assemblies are formed in chloroform depending on the nature of the cation, anion and salt concentration, as characterized by circular dichroism and time course diffusion-ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G-quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon-like assemblies as revealed by fast magic-angle spinning (MAS) NMR spectroscopy. Distinct N-H∙∙∙N and N-H∙∙∙O intermolecular hydrogen bonding interactions drive quartet and ribbon-like self-assembly resulting in markedly different 2D 1H solid-state NMR spectra, thus facilitating a direct identification of mixed assemblies. A dissolution NMR experiment confirmed that the quartet and ribbon interconversion is reversible - further demonstrating the changes that occur in the self-assembly process of a lipophilic nucleoside upon a solid-state to solution-state transition and vice versa. A systematic study for complexation with different cations (K+, Sr2+) and anions (picrate, ethanoate and iodide) emphasises that the existence of a stable solution or solid-state structure may not reflect the stability of the same supramolecular entity in another phase
Determination of a complex crystal structure in the absence of single crystals : analysis of powder X-ray diffraction data, guided by solid-state NMR and periodic DFT calculations, reveals a new 2′-deoxyguanosine structural motif
No full textDerivatives of guanine exhibit diverse supramolecular chemistry, with a variety of distinct hydrogen-bonding motifs reported in the solid state, including ribbons and quartets, which resemble the G-quadruplex found in nucleic acids with sequences rich in guanine. Reflecting this diversity, the solid-state structural properties of 3′,5′-bis-O-decanoyl-2′-deoxyguanosine, reported in this paper, reveal a hydrogen-bonded guanine ribbon motif that has not been observed previously for 2′-deoxyguanosine derivatives. In this case, structure determination was carried out directly from powder XRD data, representing one of the most challenging organic molecular structures (a 90-atom molecule) that has been solved to date by this technique. While specific challenges were encountered in the structure determination process, a successful outcome was achieved by augmenting the powder XRD analysis with information derived from solid-state NMR data and with dispersion-corrected periodic DFT calculations for structure optimization. The synergy of experimental and computational methodologies demonstrated in the present work is likely to be an essential feature of strategies to further expand the application of powder XRD as a technique for structure determination of organic molecular materials of even greater complexity in the future
Etude des procédés de valorisation de la biomasse par catalyse et matériaux fonctionnels
No full textLa conversion de la biomasse en produits chimiques et en matériaux fonctionnels est aujourd'hui un sujet d'intéressant croissant. Cette thèse se concentre sur deux voies clés de valorisation de la biomasse : la conversion par catalyse hétérogène de la biomasse en produits chimiques et la conversion directe de matières premières lignocellulosiques en matériaux fonctionnels. La première partie de la thèse étudie le comportement chimique et la stabilité de la Faujasite (FAU) de type Y durant les transformations impliquées dans la valorisation de la biomasse : échange ionique post-synthèse, calcination et traitement hydrothermal. La deuxième partie de la thèse porte sur les matériaux fonctionnels à base de lignocellulose pour la dépollution. Nous avons notamment mesuré les propriétés d'adsorption du bore de la cellulose microcristalline, de la lignine et de la résine polymère et les cinétiques d'adsorption du bore dans ces matériaux, ce qui est important pour développer des alternatives peu coûteuses pour la capture du bore. Enfin, une stratégie de double réticulation combinant réticulation covalente et ionique a été introduite pour développer des hydrogels de cellulose stables. Ces hydrogels présentent d'excellentes propriétés de stabilité, de réactivité au pH et d'échange d'ions. De façon générale, ces travaux de thèses s'appuient sur des techniques de caractérisation multi-échelles, dont notamment la spectroscopie RMN du solide à très hauts champs magnétiques (jusqu'à 28,8 T) qui nous a permis de mieux comprendre les structures à l'échelle atomiques des matériaux impliqués dans la valorisation de la biomasse et des matériaux fonctionnels bio-dérivés. Ces informations sont précieuses pour concevoir des processus catalytiques plus efficaces et des matériaux plus performants.The conversion of biomass into chemicals and functional materials is a topic of expanding scope and importance. This thesis focuses on two key biomass valorisation pathways: the heterogeneous catalytic conversion of biomass into chemicals and the direct conversion of lignocellulosic feedstock into functional materials. The first part of the thesis investigates the chemical behaviour and stability of Faujasite (FAU)-type zeolites under post-synthesis ion-exchange, calcination, and hydrothermal treatments relevant to biomass catalysis. The second part of the thesis focuses on lignocellulose-based functional materials for environmental remediation. The boron adsorption properties of microcrystalline cellulose, lignin, and polymeric resin and their boron adsorption kinetics, significant for developing inexpensive alternatives for boron capture, are examined. In addition, a dual cross-linking strategy combining covalent and ionic cross linking was introduced to develop stable cellulose hydrogels. These hydrogels exhibit excellent stability, pH responsiveness, and ion-exchange properties. In so doing, this thesis demonstrates multiscale characterization techniques, including solid-state NMR spectroscopy at high magnetic fields (up to 28.8 T) for understanding the structural aspects of materials involved in biomass vaporization and bio-derived functional materials
High-field NMR crystallography for resolving bulk heterojunction mrophology in orgnaic solar cells processed from different solvents
No full textInternational audienc
NMR panorama of hybrid perovskites: crystals and thin films to device stacks
No full textNational audienc
Probing local structures and dynamics in emerging materials for optoelectronics and photovoltaics
No full textNational audienc
Reactive surfaces and interfaces in hybrid perovskites probed by solid-state NMR spectroscopy
No full textNational audienc
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