01735nas a2200253 4500008004100000022001400041245009500055210006900150260009500219300001200314490000800326520082500334653002001159653002301179653001601202653002001218100002101238700001701259700002001276700001901296700002701315700001701342856012201359 2005 eng d a1090-780700aIncreasing the sensitivity of 2D high-resolution NMR methods applied to quadrupolar nuclei0 aIncreasing the sensitivity of 2D highresolution NMR methods appl a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcFEB a268-2780 v1723 a

Gan and Kwak recently proposed a soft-pulse added mixing (SPAM) idea in the classical two-pulse multiple-quantum magic-angle spinning scheme. In the SPAM method, a soft pi/2 pulse is added after the second hard-pulse (conversion pulse) and all coherence orders in between them are constructively used to obtain the signal. We, here, further extend this idea to distributed samples where the signal mainly results from echo pathways and that from anti-echo pathways dies Out after a few t(1) increments. We show that, with a combination of SPAM and collection of fewer anti-echoes, an enhancement of the signal to noise ratio by a factor of ca. 3 may be obtained over the z-filtered version. This may prove to be useful even for samples with long T'(2) relaxation times. (C) 2004 Elsevier Inc. All rights reserved.

10ahigh-resolution10aquadrupolar nuclei10asensitivity10aSolid-state NMR1 aAmoureux, J., P.1 aDelevoye, L.1 aSteuernagel, S.1 aGan, Zhengting1 aGanapathy, Subramanian1 aMontagne, L. uhttps://library.ncl.res.in/content/increasing-sensitivity-2d-high-resolution-nmr-methods-applied-quadrupolar-nuclei-002690nas a2200313 4500008004100000022001400041245011600055210006900171260009500240300001200335490000800347520155000355653003601905653002801941653001101969653003001980653002002010653001802030653000802048100001902056700001702075700001702092700003502109700002702144700003002171700001902201700002602220856013002246 2006 eng d a0021-951700aEffect of spacer groups on the performance of MCM-41-supported platinum cluster-derived hydrogenation catalysts0 aEffect of spacer groups on the performance of MCM41supported pla a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcSEP a332-3390 v2423 a

MCM-41 was functionalized with (EtO)(3)SiCH2Cl, (MeO)(3)SiCH2CH2CH2Cl, and (CH3)Cl2SiCH2Cl. The functionalized materials were characterized by solid-state NMR (CPMAS, Si-29 and C-13) and XPS. The NMR data indicate that three new silicon environments were created by(EtO)(3)SiCH2Cl and (MeO)(3)SiCH2CH2CH2Cl, whereas with (CH3)Cl2SiCH2Cl, two new silicon environments were obtained. XPS results from Si 2p core level and the valence band from the material functionalized by (MeO)(3)Si(CH2)(3)Cl was found to be the same as that of the corresponding fresh catalyst (1a), in contrast to that of the materials functionalized by the other two silane reagents. After further functionalization with triethylamine, these materials were used as inorganic anion exchangers to support the cluster anion [Pt-12(CO)(24)](2-). Solid-state NMR (29Si, C-13, N-15) was used to establish the presence of the quaternary ammonium group in the cluster-supported species. Analogous materials were also created using fumed silica as the support, and all of the cluster-supported materials were tested as catalysts for the hydrogenation of methyl pyruvate, acetophenone, nitrobenzene, benzonitrile, ethylacetoacetate, 4-nitrotoluene, cyclohexanone, allyl alcohol, and styrene. The best activity was obtained for the catalyst that had MCM-41 as the support and chloropropyl as the spacer group. TEM showed that the supports and the spacer groups had observable effects on the platinum crystallite size of the catalysts. (c) 2006 Elsevier Inc. All rights reserved.

10afunctionalized inorganic oxides10ahydrogenation catalysts10aMCM-4110aplatinum carbonyl cluster10aSolid-state NMR10aspacer groups10aXPS1 aMaity, Niladri1 aBasu, Susmit1 aMapa, Maitri1 aRajamohanan, Pattuparambil, R.1 aGanapathy, Subramanian1 aGopinath, Chinnakonda, S.1 aBhaduri, Sumit1 aLahiri, Goutam, Kumar uhttps://library.ncl.res.in/content/effect-spacer-groups-performance-mcm-41-supported-platinum-cluster-derived-hydrogenation-102021nas a2200277 4500008004100000022001400041245012300055210006900178260009800247300001200345490000700357520099700364653002901361653002901390653002701419653001001446653002301456653002001479653001001499653000901509100002701518700001701545700002201562700002901584856013001613 2008 eng d a0749-158100aHeteronuclear dipolar decoupling effects on multiple-quantum and satellite-transition magic-angle spinning NMR spectra0 aHeteronuclear dipolar decoupling effects on multiplequantum and  aTHE ATRIUM, SOUTHERN GATE, CHICHESTER PO19 8SQ, W SUSSEX, ENGLANDbJOHN WILEY & SONS LTDcOCT a948-9540 v463 a

We here report on the influence of heteronuclear dipolar decoupling on the Al-27 3QMAS, 5QMAS, and the double-quantum filter-satellite-transition magic-angle spinning (DQF-STMAS) spectra of a strongly dipolar-coupled system, gibbsite. The requirements for heteronuclear dipolar decoupling increase with the order of coherence evolving in the indirect dimension of a two-dimensional (2D) experiment. The isotropic line width of the high-resolution 2D spectra, in samples like gibbsite, is composed of four parts: the distribution of isotropic shifts (delta(ISO), delta(QIS)), the homogeneous broadening related to the proton-proton flip-flop terms, the Al-27-Al-27 homonulcear dipolar couplings, and the H-1-Al-27 heteronuclear dipolar couplings. It is shown that, even in the case of gibbsite, where a strong proton-proton bath exists, the main resolution limiting factor in these experiments resides in the H-1-Al-27 dipolar interaction. Copyright (C) 2008 John Wiley & Sons, Ltd.

10aheteronuclear broadening10aheteronuclear decoupling10ahomogeneous broadening10aMQMAS10aquadrupolar nuclei10aSolid-state NMR10aSTMAS10aTPPM1 aGanapathy, Subramanian1 aDelevoye, L.1 aArnoureux, J., P.1 aMadhu, Perunthiruthy, K. uhttps://library.ncl.res.in/content/heteronuclear-dipolar-decoupling-effects-multiple-quantum-and-satellite-transition-magic-002291nas a2200361 4500008004100000022001400041245011000055210006900165260007300234300001000307490000800317520103700325653002401362653004201386653002401428653002001452100003101472700001901503700002401522700002501546700002201571700001501593700002201608700001701630700001801647700001901665700002201684700001901706700002501725700002901750700001901779856013101798 2013 eng d a0301-010400aBasic structural motif and major biophysical properties of Amyloid-beta are encoded in the fragment 18-350 aBasic structural motif and major biophysical properties of Amylo aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAUG a80-870 v4223 a

Aggregation and misfolding of the amyloid beta (A beta) peptide is thought to initiate Alzheimer's disease (AD). Here we study the role played by its central segment (A beta(18-35)) in determining these properties. A beta(18-35) has a solubility of 18 mu M. The soluble fraction consists mainly of small oligomers, which have mixed beta-sheet and random coil structures. The monomer is mostly a random coil with some residual compactness. Aggregated A beta(18-35) forms fibrils of width 3.0 +/- 0.7 nm, which is consistent with a hairpin shape. Each of these properties has a close similarity to A beta(40). Remarkably, solid state NMR indicates that the fibrils also retain the secondary structure and tertiary contacts of A beta(40). This is the shortest fragment of A beta reported so far which preserves its fibrillar architecture, including the hairpin turn, as well as its solution phase conformational properties. Residues 18-35 should therefore be a key target of AD therapeutics. (C) 2013 Published by Elsevier B. V.

10aAlzheimer's disease10aFluorescence correlation spectroscopy10aProtein aggregation10aSolid-state NMR1 aChandrakesan, Muralidharan1 aSarkar, Bidyut1 aMithu, Venus, Singh1 aAbhyankar, Rajiv, M.1 aBhowmik, Debanjan1 aNag, Suman1 aSahoo, Bankanidhi1 aShah, Riddhi1 aGurav, Sushma1 aBanerjee, Raja1 aDandekar, Sucheta1 aJose, Jaya, C.1 aSengupta, Neelanjana1 aMadhu, Perunthiruthy, K.1 aMaiti, Sudipta uhttps://library.ncl.res.in/content/basic-structural-motif-and-major-biophysical-properties-amyloid-beta-are-encoded-fragment-001655nas a2200277 4500008004100000022001400041245015600055210006900211260000900280300001400289490000600303520071700309653001901026653000901045653001101054653002401065653001801089653001901107653002001126100002301146700002001169700002301189700001501212700002401227856012601251 2020 eng d a2574-096200aPhotocatalytic hydrogen generation and CO2 conversion using g-C3N4 decorated dendritic fibrous nanosilica: role of interfaces between silica and g-C3N40 aPhotocatalytic hydrogen generation and CO2 conversion using gC3N cSEP  a8150-81580 v33 a

We have synthesized g-C3N4 decorated over dendritic fibrous nanosilica (DFNS). The generation of C-N-Si interfaces by coating each fiber of DFNS with g-C3N4 not only provided high surface area but also affected the optical and electronic properties of the composite. The catalyst synthesis reproducibility issue of g-C3N4 was resolved using a vacuum-sealed quartz tube. The extended light absorption in the visible region, enhanced lifetime of photogenerated charge carriers due to the formation of interfaces between silica and g-C3N4 (confirmed by solid-state NMR), and increased surface area result in the improved photocatalytic activity of DFNS/g-C(3)N(4)for hydrogen generation and CO2 conversion.

10aCO2 conversion10aDFNS10ag-C3N410aHydrogen generation10ananocatalysts10aphotocatalysts10aSolid-state NMR1 aRawool, Sushma, A.1 aSamanta, Anupam1 aAjithkumar, T., G.1 aKar, Yusuf1 aPolshettiwar, Vivek uhttps://library.ncl.res.in/content/photocatalytic-hydrogen-generation-and-co2-conversion-using-g-c3n4-decorated-dendritic02819nas a2200241 4500008004100000022001400041245009100055210006900146260000900215300001400224490000700238520200900245653002302254653003102277653002302308653001702331653002002348100002702368700002202395700002002417700002302437856011702460 2024 eng d a1543-838400aIn situ monitoring of competitive coformer exchange reaction by 1H MAS solid-state NMR0 aIn situ monitoring of competitive coformer exchange reaction by  cFEB  a1479-14890 v213 a

In a competitive coformer exchange reaction, a recent topic of interest in pharmaceutical research, the coformer in a pharmaceutical cocrystal is exchanged with another coformer that is expected to form a cocrystal that is more stable. There will be a competition between coformers to form the most stable product through the formation of hydrogen bonds. This will cause destabilization of the pharmaceutical products during processing or storage. Therefore, it is important to develop a mechanistic understanding of this transformation by monitoring each and every step of the reaction, employing a technique such as H-1 nuclear magnetic resonance (NMR). In this study, an in situ monitoring of a coformer exchange reaction is carried out by H-1 magic angle spinning (MAS) solid-state NMR (SSNMR) at a spinning frequency of 60 kHz. The changes in caffeine maleic acid cocrystals on addition of glutaric acid and caffeine glutaric cocrystals on addition of maleic acid were monitored. In all of the reactions, it has been observed that caffeine glutaric acid Form I is formed. When glutaric acid was added to 2:1 caffeine maleic acid, the formation of metastable 1:1 caffeine glutaric acid Form I was observed at the start of the experiment, indicating that the centrifugal pressure is enough for the formation. The difference in the end product of the reactions with a similar reaction pathway of 1:1 and 2:1 reactant stoichiometry indicates that a complete replacement of maleic acid has occurred only in the 1:1 stoichiometry of the reactants. The polymorphic transition of caffeine glutaric acid Form II to Form I at higher temperatures was a crucial reason that triggered the exchange of glutaric acid with maleic acid in the reaction of caffeine glutaric acid and maleic acid. Our results are novel since the new reaction pathways in competitive coformer exchange reactions enabled understanding the remarkable role of stoichiometry, polymorphism, temperature, and centrifugal pressure.

10acaffeine cocrystal10acoformer exchange reaction10ain situ monitoring10apolymorphism10aSolid-state NMR1 aHareendran, Chaithanya1 aAlsirawan, Bashir1 aParadkar, Anant1 aAjithkumar, T., G. uhttps://library.ncl.res.in/content/situ-monitoring-competitive-coformer-exchange-reaction-1h-mas-solid-state-nmr01833nas a2200217 4500008004100000022001400041245012700055210006900182260000900251300001400260490000700274520106100281653000901342653002001351653002701371653001601398653002001414100002701434700002301461856013101484 2025 eng d a1543-838400aProbing the effect of fluorine on hydrogen bonding interactions in a pharmaceutical hydrate using Advanced Solid-State NMR0 aProbing the effect of fluorine on hydrogen bonding interactions  cMAR  a1869-18800 v223 a

Structural studies of pharmaceutical hydrates are essential to understanding stability-related issues, especially during the heating process of formulation. A thorough understanding of the hydration and dehydration behavior of active pharmaceutical ingredient (API) hydrate is also important since phase transitions can occur during the formulation process. This is because dehydration could result in a considerable rearrangement in the structure if water-API hydrogen bonding is present. We perform advanced solid-state NMR experiments on regorafenib monohydrate to investigate the role of fluorine in hydrogen bonding interaction, and the results are compared to its anhydrous form and its structural analogue, namely, sorafenib. Our results show that significant structural changes could not be observed on dehydration. Based on our study, it can be concluded that the introduction of fluorine restricts the intramolecular hydrogen bonding and the asymmetry in the structure of regorafenib monohydrate is absent, in comparison to sorafenib.

10aDQSQ10aHydrogenbonding10apharmaceutical hydrate10aregorafenib10aSolid-state NMR1 aHareendran, Chaithanya1 aAjithkumar, T., G. uhttps://library.ncl.res.in/content/probing-effect-fluorine-hydrogen-bonding-interactions-pharmaceutical-hydrate-using-advanced02711nas a2200301 4500008004100000022001400041245013500055210006900190260000900259300001100268490000800279520168000287653001801967653003001985653002802015653002402043653001602067653002002083100002802103700001902131700001902150700002102169700002302190700002602213700001602239700002502255856012902280 2026 eng d a2468-823100aEffect of sulfonation density on acid strength in ion exchange resins: Insights from solid-state NMR and density functional theory0 aEffect of sulfonation density on acid strength in ion exchange r cMAR  a1157940 v5933 a

Ion-exchange (IE) resins are widely used as solid acid catalysts; however, their surface acidity remains poorly characterized because their limited thermal stability precludes conventional NH3-based acidity measurements. Moreover, acid-site accessibility in IE resins is strongly governed by solvent- or reactant-induced swelling. Here, we investigate the surface acidity of commercial Amberlyst and Indion IE resins using & sup3;& sup1;P MAS NMR (Magic Angle Spinning Nuclear Magnetic Resonance), employing TMPO as a molecular probe dispersed on the resin with moderately swelling dichloromethane, thereby capturing the swollen-state acidity relevant for predicting catalytic activity. The deconvolution of the P-31 MAS NMR spectra reveals three distinct acid-strength zones arising from inhomogeneous sulfonation of the polymer matrix. The overall acidity, quantified by the area-weighted average P-31 chemical shift (delta), increases monotonically with sulfonation density. Notably, only resins containing acid sites stronger than similar to 80 ppm exhibited measurable catalytic activity in alpha-pinene isomerization, establishing a direct correlation between acidity and activity. Density functional theory (DFT) calculations on representative resin models, supported by electron-density analyses, attribute the enhancement of acid strength at higher sulfonation densities to cooperative hydrogen-bonding networks among neighboring sulfonic acid groups. Together, these findings establish P-31 MAS NMR-derived surface acidity as a catalytically relevant descriptor for the rational selection of IE resins in liquid phase acid-catalyzed chemistries.

10aAcid strength10aDensity functional theory10aheterogeneous catalysis10aIon-exchange resins10aSolid acids10aSolid-state NMR1 aTumulu, Goutam, Narayan1 aDatar, Sarvesh1 aShelke, Ankita1 aSwain, Gitanjali1 aAjithkumar, T., G.1 aThirumalaiswamy, Raja1 aMohan, Ojus1 aMahajani, Sanjay, M. uhttps://library.ncl.res.in/content/effect-sulfonation-density-acid-strength-ion-exchange-resins-insights-solid-state-nmr-and01929nas a2200337 4500008004100000022001400041245007900055210006900134260000800203300000700211490000700218520093900225653002801164653001201192653001601204653001301220653002001233100001901253700002301272700001901295700001701314700001801331700001701349700001601366700001701382700002101399700001901420700002301439700001601462856011301478 2026 eng d a0250-470700aFly-ash-based geopolymers: leachability and solid-state NMR investigations0 aFlyashbased geopolymers leachability and solidstate NMR investig cMAR a540 v493 a

This study aims to explore how leaching impacts the microstructure of a selected fly ash-derived geopolymer and evaluate its potential for near-surface disposal of radioactive waste. The uniqueness of this geopolymer formulation is its ability to form an aluminosilicate network that remains resistant to structural changes upon contact with water. The leach index of base elements such as Ca, Al, Na and Si was between 11 and 13, suggesting that the formulation is superior to Portland cement or conventional hydraulic cement. Solid-state NMR reveals that the water-interacted specimen has no contamination of the zeolite phase and all the Na is incorporated into the aluminosilicate geopolymer gel network, which also confirms that the glassy network of the geopolymer is responsible for imparting low leachability of base elements from its structure, and there is no labile sodium available for exchange as in zeolites.

10aaluminosilicate network10aFly ash10aGeopolymers10aleaching10aSolid-state NMR1 aNadol, Athulya1 aAjithkumar, T., G.1 aSingla, Rashmi1 aAlex, T., C.1 aKumar, Sanjay1 aBhatt, Himal1 aDeo, M., N.1 aSen, Debasis1 aAmbashta, R., D.1 aBajpai, R., K.1 aShivakumar, Y., C.1 aManohar, S. uhttps://library.ncl.res.in/content/fly-ash-based-geopolymers-leachability-and-solid-state-nmr-investigations