NMR Spectroscopy Research Papers - Academia.edu (original) (raw)

Structural information on soil organic matter (SOM) at the molecular level can be obtained on diverse structural units that are amenable to degradation techniques. Chemolytic techniques in combination with colorimetric analyses or GC MS are used to determine amino acids (proteins), sugars (polysaccharides), lipids, or aromatic oxidation products from lignin or charred organic matter. Microbial markers (amino sugars, muramic acid) are analyzed after hydrolysis and gas chromatographic separation. Macromolecular structures can also be subjected to thermochemolytic degradation or pyrolysis and subsequent analysis of the fragments by GC MS. Alternative techniques for the examination of organic matter in heterogeneous macromolecular mixtures are non-destructive spectroscopic methods, such as nuclear magnetic resonance (NMR) spectroscopy. Although this technique can give good results concerning the gross chemical composition, speci®c compounds are hardly identi®ed. The combination of spectroscopic techniques with thermolytic and chemolytic methods will add substantially to the understanding of the nature of refractory soil organic matter. Physical fractionation prior to analysis provides a means to dierentiate between distinct SOM pools that can be further characterized by the methods described above. Studies on SOM structural characteristics have focused mainly on the A horizons of soils under agriculture and litter biodegradation in forest soils and need to be extended to a wider variety of soil types and the subsoil. #

- by
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- Earth Sciences, Organic Geochemistry, Spectroscopy, Nuclear Magnetic Resonance

Plant litter and the microbial biomass are the major parent materials for soil organic matter (SOM) formation. Plant litter is composed of complex mixtures of organic components, mainly polysaccharides and lignin, but also aliphatic biopolymers and tannins. The composition and relative abundance of these components vary widely among plant species and tissue type. Whereas some components, such as lignin, are exclusively found in plant residues, speci®c products are formed by microorganisms, e.g. amino sugars. A wide variety of chemical methods is available for characterizing the chemical composition of these materials, especially the chemolytic methods, which determine individual degradation products and solid-state 13 C NMR spectroscopy, that gives an overview of the total organic chemical composition of the litter material. With the development of these techniques, an increasing number of studies are being carried out to investigate the changes during decay and the formation of humic substances. An overview is given on the amount of litter input, the proportion of various plant parts and their distribution (below-ground/above-ground), as well as the relative proportion of the different plant tissues. Major emphasis is on the organic chemical composition of the parent material for SOM formation and thus this paper provides information that will help to identify the changes occurring during biodegradation of plant litter in soils. q

2,4-Dinitrophenol was employed with benzyloxy-bis-(diisopropylamino)phosphine to synthesise the cyclic phosphate derivatives of a series of alkane diols (HO-(CH 2 ) n -OH, n ¼ 2-6) in good isolated yields. Tetrazole and DNP were compared by 31 P NMR spectroscopy for their ability to catalyse the cyclisation at the P(III) stage. Investigation of the phosphate triester stability under various oxidation and chromatographic conditions resulted in the optimisation of the isolation procedures of the chemically unstable cyclic compounds. Conditions for debenzylation were developed to yield the corresponding cyclic phosphodiesters quantitatively. The methodology was further applied to the preparation and isolation of the cyclic phosphate derivative of a carbohydrate.

- by marie migaud
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- Organic Chemistry, NMR Spectroscopy
- by Hee Jae shin
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- Phytochemistry, NMR Spectroscopy, Biological Sciences, CHEMICAL SCIENCES

Objective: Biodegradable polycaprolactone/starch composites can be used for bone tissue engineering applications. The effect of the ratio of components on composite properties is of tremendous importance. Methods: Polycaprolactone/starch composite of 80/20 and 70/30 ratios were fabricated by dissolving them in chloroform followed by evaporation of the solvent. Results: The composites were characterized by fourier transform infrared spectroscopy. Their bioactivity was evaluated by studying the apatite formation ability after immersing the specimens in simulated body fluid. The results of compressive test on samples showed that the composite's modulus and strength approximated that of human trabecular bone. Mass loss in distilled water and starch degradation rate in PBS was evaluated, which showed that the starch ratio was effective in composite degradation. MTT analysis and alkaline phosphatase levels showed that this composite had no toxicity and could increase G-299 cell line osteoblastic activities. Conclusion: The increase in cellular osteoblastic activities and the ability for apatite formation on the composite surface, in addition to the polycaprolactone/starch samples' mechanical properties shows their capability to be used as substitutes for bone. Because this composite degradation rate is controlled by changing the starch ratio, it has the potential for use in bone tissue engineering applications. Samples that have a 70/30 ratio are considered optimal due to their enhanced cellular response and better mechanical properties.

- by Mehran Solati-Hashjin
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- Engineering, Materials Engineering, Chemical Engineering, Thermodynamics

Single crystals of deuterated triglycine sulfate (DTGS), DTGS doped with deuterated phosphoric acid (DTGS (0.8) P (0.2)) [DTGSP], and L-alanine (DTGS (0.8) P (0.2) —LA (2 gm)) [DTGSP-LA] are grown from deuterated water solution containing glycine, D 2 SO 4 , D3PO4, and L-alanine. Vibrational spectroscopic analysis has been under taken to examine the configuration of glycinium ion formation and the changes in the nature of hydrogen bonding due to the partial substitution of SO 4 2-by PO 4 3-. Fourier Transform Infrared (FT-IR) and FT-Raman analysis indicates the presence of both zwitter and glyciniumions in the doped DTGS crystals, which is due to the low incorporation of dopants into the crystal lattice, which supports Hoshino's theory of spontaneous polarization reversal. Nuclear magnetic resonance studies (1 H, 13 C, 31 P) revealed the possible bond formation during the formation of the compound.

- by Dr.Kuzhivelil Joseph Arun and +2
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- NMR Spectroscopy, Raman spectroscopy applications
- by Sean F Johnston
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- Condensed Matter Physics, Spectroscopy, NMR Spectroscopy, Ionic Liquid

Mushroom polysaccharides are potent substances that exhibit antitumor and immunomodulatory properties. Studies comparing the chemical composition and antitumor-related activities of polysaccharides released by fungal strains under different growth conditions are not available. Thus, the present study compared polysaccharides extracts produced by Pleurotus pulmonarius from mycelium grown in liquid culture (ME) or fruiting bodies (FBE). Polysaccharides of both ME and FBE had a relatively high molecular mass. NMR spectroscopy indicated that ME glucan is an α-glucan whereas FBE glucan is a mixture of both αand β-glucans. Glucose and galactose where the most prominent monosaccharide in both glucans. Treatment of several colon cancer cell lines expressing varying amounts of galectin-3 with the two fungal glucans inhibited their viability and significantly reduced their ability to adhere to the key component of the extracellular matrix, fibronectin, and to a human umbilical vein endothelial cell monolayer, in a time-and dose-dependent manner mainly in those cell lines expressing high amounts of galectin-3. We conclude that ME and FBE glucans may exert a direct antiproliferative effect on cancer cells expressing high galectin-3 concentrations and concomitantly downregulate tumor cell adherence, the latter being directly related to cancer progression and metastasis.

- by Yoram Tekoah
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- Cell Adhesion, NMR Spectroscopy, Polysaccharides, Applied microbiology

Two new ether lipids, 1-O-alkyl/alkenyl-2-O-acyl-glycero-3-phosphocholine and its lyso form, 1-O-alkyl/ alkenyl-glycero-3-phosphocholine, were identified in the cell membrane of Mycoplasma fermentans using chemical analyses, GLC-MS, MALDI-TOF MS, and 1D and 2D NMR spectroscopy. The lipids are heterogeneous with respect to both acyl and alkyl/alkenyl residues. The acyl residues at position 2 of glycerol are hexadecanoyl and octadecanoyl in a molar ratio of 3.6 : 1 with a trace amount of octadecenoyl. The alkyl/ alkenyl residues at position 1 of glycerol are hexadecyl (78%), octadecyl (7%), octadecenyl (14%), and hexadecenyl (traces). In the octadecenyl residue, the double bond has a cis configuration and is located at either position 1 H (plasmalogen-type lipid) or 9 H in a ratio < 1 : 1. This is the first report of the presence of alkyl and vinyl (alk-1 H -enyl) ether lipids in the cell membrane of aerobically grown mycoplasmas. Lipids of this type have been found in some Gram-positive bacteria, thus supporting the hypothesized close taxonomical relationship of these bacteria to mycoplasmas. The ether lipids of M. fermentans are structurally similar to platelet activating factor; it was demonstrated that the 2-O-acetylated lyso form lipid can mimic platelet-activating factor activity in isolated perfused and ventilated rat lungs.

The synthesis of the chloro-and parent cyclopentadienone-fused dihydropyrenes 10 and 7 are reported. Analysis of coupling constants, and chemical shift changes between these and the nonconjugated dihydro derivatives 11 and 8, and between the benzannulene 4 and the parent annulene 12, indicates without doubt that cyclopentadienone is behaving as an antiaromatic 4n-π system and that in its effect on the ring current of 12, cyclopentanedienone has about 80% of the effect of benzene. This is the first time that a suitable probe has been used to estimate the relative ability of a 4n-π system to bond localize the probe in comparison to the (4n + 2)-π system benzene.

- by Wei Fan
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- NMR Spectroscopy, Electron Affinity, CHEMICAL SCIENCES, Ionization Potential

Spumre(emm&&bor a b Medizinisckn Einriihtungm, Hcinrich-Heinc-Uniwsitiit, 4000 DIisscldwf 1 , G-ny Assmcx.-The structures of novel oligoglycosidic cardenolides, alepposide A (CssHs6023) 111 and alepposide B (C4&74020) [21, have been deduced mainly by nmr methods. Based on homonuclear ('H and I3C nmr, 'H COSY) and protondetected heteronuclear shift correlation experiments IJ-MQC both for '](c, H) and fot long-range cwplings], dep poside A 111 was shown to have the structure strophanthidin-3-0-~-glucopyranosyl-( 1-4)-0pdiginopyranosyl-( l~4)-O-~-oleandropyranosyl-( 1~4)-0-~digitoxopyranosyl-( 1*4)-O-Bdigitoxopyranoside. The structure of alepposide B 127 was established as strophanthidin-3-0-pglucopyranosyl-( 1~4)-0-~-oleandropyrosyl-( 1-4)-O-~digitoxopyranql-( 1*4>0-p-digi toxopyranoside .

The 1 H and 13 C NMR spectra of 9-acridinone and its ®ve derivatives dissolved in CDCl 3 , CD 3 CN and DMSO-d 6 were measured in order to reveal the in¯uence of the constitution of the compounds and features of the solvents on chemical shifts and 1 H± 1 H coupling constants. Experimental data were compared with theoretically predicted chemical shifts, on the GIAO/ DFT level of theory, for DFT (B3LYP)/6-31G pp optimized geometries of moleculesÐalso for four other 9-acridinones. This comparison helped to ascribe resonance signals in the spectra to relevant atoms and enabled revelation of relations between chemical shifts and physicochemical features of the compounds. It was found that experimentally or theoretically determined 1 H and 13 C chemical shifts of selected atoms correlate with theoretically predicted values of dipole moments of the molecules, as well as bond lengths, atomic partial charges and energies of HOMO. q

An analytical method for lignins has been developed that involves derivatization followed by reductive cleavage (DFRC), depolymerization, and quantitative 31 P NMR spectroscopy. This technique detects and quantifies the various ether linkages present in softwood residual kraft lignins (RKL) and milled wood lignins (MWL). In addition, the technique supplies new quantitative information about -aryl ethers linked to condensed and noncondensed aromatic moieties, including dibenzodioxocins. Within RKL, -aryl ether bonds connected to condensed phenolic moieties predominated over those connected to noncondensed phenolic moieties. In addition, the amount of DFRC monomers determined by gas chromatography was minute in the RKL but large in the MWL. This indicates that almost all noncondensed -aryl ether linkages were cleaved during kraft pulping. The method offers new avenues for the detailed investigation of the bonding patterns of native and technical lignins.

- by Dimitris Argyropoulos
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- Engineering, Nuclear Magnetic Resonance, NMR Spectroscopy, Phosphorus

The structure of six synthetic n-3 polyunsaturated fatty acids bearing three to six double bonds has been confirmed by high resolution NMR. Complete assignment of 13 C spectra of isomers of h-linolenic acid, EPA and DHA was established by the use of the new SAPHIR-HSQC method developed at the NMR center and compared with the results obtained from spin lattice relaxation time measurements. Sequential Attribution of Proton-carbon pairs from High Resolution (SAPHIR) HSQC, HSQC-TOCSY experiments allow both the precise measurement of olefinic coupling constants and the location of each double bond inside the chain. We have also drawn attention to the effect of an E-double bond in comparison with a Z-olefinic bond to the chemical shifts of neighboring carbon atoms. A set of shift parameters, obtained from our NMR data, allowed the visualization of electric and steric effects of E-olefinic bond in D 11 and 3 positions of the carbon chain of polyunsaturated fatty acids.

- by Jean-michel Vatèle
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- NMR Spectroscopy, Physical sciences, CHEMICAL SCIENCES, High Resolution

An NMR study of proton chemical shift patterns of known linear a-D D-glucopyranose di-and trisaccharide structures was carried out. Chemical shift patterns for (a1?2)-, (a1?3)-, (a1?4)-and (a1?6)-linked D D-glucose residues were analysed and compared to literature data. Using these data, a 1 H NMR structural-reporter-group concept was formulated to function as a tool in the structural analysis of a-D D-glucans.

- by G.J. Gerwig and +1
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- Organic Chemistry, Hydrogen, Magnetic Resonance Imaging, NMR Spectroscopy

s The goal of this study was to develop and validate a liquid chromatography (LC) method for the rapid determination of dipyrone (metamizole sodium) in solid and liquid formulations. Samples were extracted with water and filtered prior to LC analysis. The analytical procedure involved reversed phase LC with a Zorbax SB C 18 column (5 m particle size, 4.6 mm × 250 mm i.d.), isoctratic methanol/water (80/20, v/v) mobile phase with UV detection at 254 nm. The flow rate was 1 mL min −1 , injection volume was 100 L and retention time of dipyrone was 3.3 min. The method was validated with respect to linearity, precision and accuracy. Calibration curves were linear in the range 0.5–100 g mL −1 for analyte and the recoveries at three levels (10, 15 and 25 g mL −1) ranged from 93 to 100%. All results for dipyrone were confirmed by liquid chromatography–mass spectrometry (LC–MS) and 1 H nuclear magnetic resonance (NMR) spectroscopy. Due to its simplicity and accuracy, the assay method is suitable for routine analysis of both solid and liquid formulations and seven retail samples were analyzed using the validated method.

- by Burak Veli Kabasakal
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- Analytical Chemistry, NMR Spectroscopy, Validation, Drug analysis

Equimolar amounts of trans-[ReOX 2 (OEt)(PPh 3) 2 ] (X= Cl, Br, I) precursors and potentially bidentate N,S-donor pyrimidine-2(1H)-thione (pymSH) react in refluxing acetone to give mononuclear octahedral paramagnetic trans-[Re III X 2 (pymS)(PPh 3) 2 ] (X= Cl, Br, I) species. Starting from a metal-ligand molar ratio of 1:3, in the presence of N(C 2 H 5) 3 as deprotonating agent in refluxing ethanol, the same reaction proceeds stepwise, affording octahedral [ReO(pymS) 3 ] or [ReO(pymS) 3 ] and pentagonalbipyramidal [Re(pymS) 3 PPh 3 ] complexes as a function of the reaction time. The compounds were characterized by elemental analysis, magnetic susceptibility, UV-Vis-NIR, IR and 1 H NMR spectroscopy and by cyclovoltammetric measurements. Reaction pathways and physico-chemical properties of the complexes are discussed.

- by Maria Cannio
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- Inorganic Chemistry, NMR Spectroscopy, Reaction Time, Magnetic Susceptibility

The regulation of the trp repressor system of Escherichia coli is frequently modeled by a single equilibrium, that between the aporepressor (TR) and the corepressor, L-tryptophan (Trp), at their intracellular concentrations. The actual mechanism, which is much more complex and more finely tuned, involves multiple equilibria: TR and Trp association, TR oligomerization, specific and nonspecific binding of various states of TR to DNA, and interactions between these various species and ions. TR in isolation exists primarily as a homodimer, but the state of oligomerization increases as the TR concentration goes up and/or the salt concentration goes down, leading to species with lower affinity for DNA. We have used multinuclear, multidimensional NMR spectroscopy to investigate structural changes that accompany the oligomerization of TR. For these investigations, the superrepressor mutant EK18 (TR with Glu 18 replaced by Lys) was chosen because it exhibits less severe oligomerization at higher protein concentration than other known variants; this made it possible to study the dimer to tetramer oligomerization step by NMR. The NMR results suggest that the interaction between TR dimers is structurally linked to folding of the DNA binding domain and that it likely involves direct contacts between the C-terminal residues of the C-helix of one dimer with the next dimer. This implies that oligomerization can compete with DNA binding and thus serves as a factor in the fine-tuning of gene expression.

- by Werner van Zyl
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- NMR Spectroscopy, Crystal structure, Metal Complexes, Single Crystal

The synthesis of AB 2 -type miktoarm star polymers using a combination of reversible addition-fragmentation chain transfer (RAFT), ring opening polymerization (ROP) and ''Click'' chemistry was demonstrated in this work. An azide functional RAFT agent was used to polymerize butyl acrylate, polyethylene glycol acrylate and N-isopropylacrylamide monomers. Propargylamine was reacted with glycerine carbonate to obtain a dihydroxy functional alkyne compound which was used for the ring opening polymerization of 3-caprolactone (3-CL) and lactide. The resulting alkyne functional polycaprolactone (PCL) and polylactide (PLA) polymers were reacted with azide functional polymers in the presence of copper bromide (CuBr) catalyst to obtain miktoarm star polymers. The polymers were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The star polymers had low polydispersity (w1.3) with well-defined structures. These polymers have a number of potential applications including crosslinking agents for polyurethane (PU) coatings for biodegradable and fouling release applications.

- by kunal singh
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- Engineering, Nuclear Magnetic Resonance, FTIR spectroscopy, NMR Spectroscopy

† E.P. and R.A. contributed equally to this work.

The aim of this work was to study the effect of the degree of substitution (DS) and the purity of sodium carboxymethyl cellulose (CMCNa) prepared from Tunisian vine stem on the absorption and retention of water. Vine stem was first delignified using souda-anthraquione, then bleached and finally chemically modified, in order to synthesize different CMCNa derivatives. The carboxymethylation reaction was carried out in presence of NaOH (40 %) and monochloroacetic acid (ClCH 2 COOH), in n-butanol as a reaction solvent. The obtained CMCNa derivatives were characterized using different tools such as the DS, Fourier transforms IR techniques, CP-MAS 13 C-NMR, the exchange capacity as well as the determination of modification reaction yield. The performance of the prepared derivatives in term of absorption capacities and retention capacities was established. The performance of CMCNa derivatives was compared with that achieved by commercial counterparts and it was concluded that the prepared ones exerted higher efficiency.

- by Angel Cortés
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- Engineering, Environmental Engineering, Materials Engineering, Bioinformatics

The preparation of the new w-epoxide and 1,2-dihydroxy tri¯uorovinyl monomers useful as comonomers in the copolymerization of commercially available alkenes is presented. The addition of 1-iodo-1,2-dichloro-1,2,2-tri¯uoroethane to allyl acetate led quantitatively to the expected chlorotri¯uorinated-2-iodo-1-acetate which underwent a thermal rearrangement yielding R F,Cl CH 2 CH(OAc)CH 2 I even in the presence of a radical initiator that started to decompose at mild temperature. Whatever the amount of rearranged product, both these iodoacetates formed epoxides in alkali media giving two new compounds in high yields. Dechlorination yielded the tri¯uorovinyl epoxide (in 40% yield) and side products from the ring opening of the oxirane group. The mixture of halogenated epoxides was quantitatively hydrolysed into the halogenated -1,2-diol which was dechlorinated into F 2 CCFCH 2 CH(OH)CH 2 OH in 58% yield. All these products and intermediates were characterized by 1 HY 19 F and 13 C NMR spectroscopy. # 1999 Elsevier Science S.A. All rights reserved.

- by petya petrova
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- Engineering, Inorganic Chemistry, Organic Chemistry, Nuclear Magnetic Resonance

A previously unknown leucite-related structure has been determined for synthetic CszCdSisO~2. NMR spectroscopy shows that there are five distinct tetrahedral sites (T-sites) occupied by Si and one T-site occupied by Cd in the framework structure, while analysis of the synchrotron X-ray powder diffraction pattern establishes that this material is orthorhombic, Pbca [RI = 13.1%, R wp = 16.1%, Rex p = 13.1%; eight formula units per unit cell; unit-cell parameters a= 13.6714(1), b= 13.8240 (1), c= 13.8939 (1) ,~, V = 2625.83 (6) ,~3]. Tetrahedral cation ordering rates for Si and Cd are sufficiently high for both hydrothermally and dry-synthesized samples to be fully ordered. The symmetry relations between leucites with P2/c and Pbca structures are discussed and it is shown that such materials are related by a displacive phase transition, in which the

- by Simon Redfern
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- Analytical Chemistry, NMR Spectroscopy, Mineral Chemistry, Synchrotron Radiation
- by Gerd Gemmecker and +1
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- Mathematics, Biomolecular NMR, NMR Spectroscopy, Magnetic Resonance Spectroscopy

The synthesis and characterization of some new terphenyl ligands, modified by meta alkyl substitution on the central ring are described. The new ligands were designed for potential applications in the stabilization of novel low valent main group species or transition metal heteronuclear multiply bonded compounds. Compounds 1-I-C6H1-2,6-Ph2-3,5-Pr2i (1), 1-I-C6H1-2,6-Mes2-3,5-Pr2i (3) (Mes=2,4,6-trimethylphenyl), 1-I-C6H1-2,6-Trip2-3,5-Pr2i (5) (Trip=2,4,6-triisopropylphenyl) and 1-I-C6H1-2,6-Dipp2-3,5-Pr2i (6) (Dipp=2,6-diisopropylphenyl) were obtained

Enzymatic transgalactosylation of lactose by means of Streptococcus thermophilus, subspecies DN-001065, led to a mixture of D-galactose ( 4%), D-glucose ( 15%), lactose ( 51%), minor disaccharides (6%), trisaccharides ( 20%) and tetrasaccharides (3%). The major trisaccharide ( 16%) was identified by NMR spectroscopy and chemical synthesis as being the known b-D-galactopyranosyl-(1 3)-b-D-galactopyranosyl-(1 4)-D-glucose (3%-b-Dgalactopyranosyl-lactose). It was purified from a mixture of peracetylated oligosaccharides by column chromatography followed by deacetylation. For the first time, 3%-b-D-galactopyranosyl-lactose has been obtained on the 1 g scale, by resorting to simple techniques and equipment. NMR spectra have been unambiguously assigned.

- by Jean-pierre Praly
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- Organic Chemistry, NMR Spectroscopy, Magnetic Resonance Spectroscopy, Glucose

A new symmetrical bidentate Schiff base ligand (L) was applied for
the synthesis of some new cadmium coordination compounds with general formula of [Cd(L)X2] in which X is halide and pseudo-halide. The ligand and all cadmium complexes were characterized by some techniques such as elemental analysis, FT-IR, 1H, 13C NMR, UV-Visible and molar conductance.
Electrochemical behavior of ligand and Cd(II) complexes were investigated by cyclic voltammetry method. Morphology and shape of [Cd(L)Cl2] particles were depicted by SEM. Antimicrobial properties such as antibacterial and antifungal activities of the complexes as compared with ligand were checked against three Gram-negative bacteria; Escherichia coli (ATCC 25922), Pseudomunase aeroginosa (ATCC 9027) and Salmonella Spp. and two Grampositive bacteria; Staphylococcus aureus (ATCC 6538) and Corynebacterium renale and three fungal strains including Aspergillus Niger, Penicillium chrysogenum and Candida albicans. The results revealed appropriate antibacterial and antifungal activities for all compounds, and it was also found that the coordination of ligand to Cd (II) lead to an increase in the antimicrobial activities in most of cases.

Diffusion-ordered NMR spectroscopy (DOSY) experiments have been carried out on dilute aqueous solutions of uncharged saccharide systems and, in particular, on six well characterized pullulan fractions of different molecular weights. The values of diffusion coefficients and hydrodynamic radii determined for the pullulan fractions are in good agreement with the results obtained with other methodologies such as light scattering. Fitting the diffusion coefficients data as a function of the molecular weight allows for the determination of a calibration curve that can be applied to a wide range of mono-, oligo-, and polysaccharides. Therefore, DOSY is proposed as a versatile tool for achieving a simple estimation of the molecular weight of uncharged polysaccharides. Mixtures of homopolymers of different molecular weight can be nicely separated. An advantage of the method is that the same sample used for the NMR characterization can be used for the molecular weight determination without any further manipulation. Other water soluble polymers, such as poly(ethylene oxide) and poly(vinylpyrrolidone), can be roughly characterized using the same calibration curve.

- by Luisa Mannina
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- Engineering, NMR Spectroscopy, Polysaccharides, Magnetic Resonance Spectroscopy

termined with approximately the same precision as in , i.e., 0.1 mol L 2 1 and 3 3 10 2 4 mol L 21 , respectively. However, the Br 1 , Ca 21 , and M g 21 ions are present in typical seawater samples at concentration levels that are below the limit of detection of the current setup. This is the reason that in the scales of the x-axis of the Br 2 , Ca 21 , and Mg 21 graphs are much smaller than the y-axis scales.

- by manpreet kaur
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- Mechanical Engineering, Analytical Chemistry, NMR Spectroscopy, Methyl Acrylate

Three kinds of carbazole derived dyes, Caz-MN, Caz-Fu, and Caz-Vm-MN of pushepull molecules were synthesized and their nonlinear optical properties measured. The second harmonic generation (SHG) coefficients, d 33 , of Caz-Fu/PVK[poly(9-vinylcarbazole)] (0.1:0.9) and Caz-Vm-MN/PVK (0.1:0.9) were 2.06 Â 10 À9 esu and 7.3 Â 10 À9 esu, respectively. The electro-optic coefficients (r 33 ) of these PVK blends with dyes were also observed to be 1.23 pm/V, 4.03 pm/V at a wavelength of 632.8 nm. The synthesized novel carbazole based dyes Caz-MN, Caz-Fu, and Caz-Vm-MN were characterized by means of 1 H NMR spectroscopy, IR spectroscopy, thermogravimetric analysis, electro-optic coefficients (r 33 ), and their NLO properties were evaluated by Maker fringe method.

- by Soo Min Lee
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- Chemical Engineering, Nonlinear Optics, NMR Spectroscopy, Second Harmonic Generation

Biological systems are exceedingly complex. The unraveling of the genome in plants and humans revealed fewer than the anticipated number of genes. Therefore, other processes such as the regulation of gene expression, the action of gene products, and the metabolic networks resulting from catalytic proteins must make fundamental contributions to the remarkable diversity inherent in living systems. Metabolomics is a relatively new approach aimed at improved understanding of these metabolic networks and the subsequent biochemical composition of plants and other biological organisms. Analytical tools within metabolomics including mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy can profile the impact of time, stress, nutritional status, and environmental perturbation on hundreds of metabolites simultaneously resulting in massive, complex data sets. This information, in combination with transcriptomics and proteomics, has the potential to generate a more complete picture of the composition of food and feed products, to optimize crop trait development, and to enhance diet and health. Selected presentations from an American Chemical Society symposium held in March 2005 have been assembled to highlight the emerging application of metabolomics in agriculture.

- by David R Gang
- •
- Engineering, Nutrition, Genomics, Metabolism

Mesoporous aluminosilicate molecular sieves with the MCM-41 structure (Si/Al ¼ 20) have been synthesized using tetraethoxysilane (TEOS) and sodium aluminate (NaAlO 2 ) as Si and Al sources and hexadecyltrimethylammonium bromide (HTMABr) and varying several parameters during the preparation process. All the samples were characterized by X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) and solid state MAS NMR spectroscopy. A significant improvement in the structure by using a novel method for template removal has been evaluated.

- by Oscar A Anunziata
- •
- Chemical Engineering, NMR Spectroscopy, Molecular Sieve, X ray diffraction

A process was developed to ascertain the bioactive components of black raspberry (Rubus occidentalis L.) fruit extracts by relating chemical constituents determined by high-field nuclear magnetic resonance (NMR) spectroscopy to biological responses using partial least-squares regression analysis. To validate our approach, we outlined relationships between phenolic signals in NMR spectra and chemical data for total monomeric anthocyanin (TMA) content and antioxidant capacity by the ferric-reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Anthocyanins, cyanidin 3-O-rutinoside (Cy 3-rut), cyanidin 3-O-(2(G))-xylosylrutinoside (Cy 3-xylrut), and cyanidin 3-O-glucoside (Cy 3-glc), were significant contributors to the variability in assay results, with the two most important NMR bins corresponding to the methyl peaks in Cy 3-rut (6 000 ) and/or Cy 3-xylrut (6 IV ). Many statistically important bins were common among assay models, but differences in structure-activity relationships resulted in changes in bin ranking. The specificity of these results supported the application of the process to investigate relationships among health-beneficial natural products and potential biological activity.

The Research about Synthesis and Characterization of SiO2 have been worked. We have synthesized Silica from "petung"bamboo leaf ash as SiO2 source. This step used sol gel methode. SiO2 were characterized by Fourier Transform Infra Red (FTIR) to investigated the stucture andX-Ray Diffaction to know about structure and crystallinity. FTIR spectra show peak at 617,22 cm-1 area that spesific for Si-H bond, peak at 786,96 cm-1 and 1095,57 cm-1 area specific for Si-O-Si bonds. Difractogram of SiO2 show that there are peak at 2θ 21,99; 31,67 and 38,88 were specific for SiO2 that calcinated at 800 o C, while for SiO2 that calcinated at 400 o C there were no peak at 2θ 31,67 dan 38,88. That peaks not shown may be because low crystallinity of SiO2 that calcinated at 400 o C. Calcination temperature greatly affects the crystallinity of SiO2.

- by hieu Duong
- •
- Chemistry, Supramolecular Chemistry, Mass Spectrometry, NMR Spectroscopy
- by Beat Vögeli
- •
- Biomolecular NMR, Hydrogen, NMR Spectroscopy, Magnetic Resonance Spectroscopy

The effect of different catalysts (NaY, Cr-VPI-5, acidic kaolinite clay, clayfen, and p-toluenesulfonic acid) on the reaction between cyclohexanone and methanol-d4 was investigated using GC-MS and in situ NMR spectroscopy at room temperature. An in situ IR spectroscopy analysis of pyridine adsorbed on the clay and NaY samples showed that they are both weakly acidic. Depending on the catalyst employed, acetalization, α-carbon deuteration, or both of these reactions occurred. With the clays only acetalization proceeded to yield 1,1-dimethoxycyclohexane with 90% conversion at room temperature. When zeolite Y was used, only deuteration of the cyclohexanone α-carbon was observed, while with the homogeneous p-toluenesulfonic acid catalyst, both deuteration of the α-carbons and the acetalization reaction proceeded.

- by Fernando Antonio Peraza Luna
- •
- Chemical Engineering, Catalysis, NMR Spectroscopy, Room Temperature

The aim of this work was to study the composition of the samples of human aqueous humour including the protein content. Using 1 H NMR spectroscopy many compounds (proteins, glucose, lactate, citrate and other metabolites) can be... more

Hydroxy fatty acids (FAs), which were isolated from glycolipids that can be prepared fermentatively from fats and oils, have been synthetically modified to contain azide and alkyne functional groups. These particular functional groups were chosen because they can participate in a copper-catalyzed reaction that combines them to form a 1,4-triazole, known as a “click” reaction, which has been widely used in a variety of fields but remains underutilized in FA chemistry. Depending on the starting hydroxy FA, these groups can be close to the carboxy unit (using 3-hydroxydecanoate) and hence the polar glycerol group, or distant from it (using 17-hydroxyoctadecanoate). These structural alternatives will impart different properties to the triacylglycerols that are subsequently prepared from the modified FA. Finally, the click reaction was used to conjugate triacylglycerols to each other and to other molecules such as a glycolipid or a protected amine.

- by Daniel Solaiman and +1
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- NMR Spectroscopy
- by Narayana Narasimhan
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- Genetics, Microbiology, Mass Spectrometry, Taxonomy

We describe the identification of novel rapamycin derivatives present as low-level impurities in active pharmaceutical ingredients using an integrated, multidisciplinary approach. Rapamycin, a fermentation-derived natural product is itself used clinically and provides the starting material for several rapamycin analog drugs, typically used in oncology. LC-MS proved a sensitive means to analyze impurity profiles in batches of rapamycin. MS fragmentation was used to gain structural insight into these impurities, usually fermentation by-products, structurally very similar to rapamycin. In cases where MS fragmentation was unable to provide unambiguous structural identification, the impurities were isolated and purified using orthogonal HPLC methods. Using the higher mass sensitivity of small-volume NMR microprobes, submilligram amounts of isolated impurities were sufficient for further characterization by multidimensional NMR spectroscopy. Full assignment of the 1 H and 13 C NMR signals revealed the structure of these impurities at an atomic level. This systematic workflow enabled the identification of several novel rapamycin congeners from active pharmaceutical ingredient without the need for large-scale isolation of impurities. For illustration, two novel rapamycin derivatives are described in this study: 12-ethyl-rapamycin and 33-ethyl-rapamycin, which exemplify previously unreported modifications on the carbon skeleton of the rapamycin macrocycle. The methodologies described here can be of wide use for identification of closely related structures found; for example as fermentation by-products, metabolites or degradants of natural product-based drugs.

- by Stephan Zech
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- Genetics, Microbiology, Mass Spectrometry, Taxonomy

Competition between glucose and lactate as oxidative energy substrates was investigated in both primary cultures of astrocytes and neurons using physiological concentrations (1.1 mm for each). Glucose metabolism was distinguished from lactate metabolism by using alternatively labelled substrates in the medium ([1-13 C]glucose + lactate or glucose + [3-13 C]lactate). After 4 h of incubation, 1 H and 13 C-NMR spectra were realized on perchloric acid extracts of both cells and culture media. For astrocytic cultures, spectra showed that amino acids (glutamine and alanine) were more labelled in the glucose-labelled condition, indicating that glucose is a better substrate to support oxidative metabolism in these cells. The opposite was observed on spectra from neuronal cultures, glutamate being much more labelled in the lactate-labelled condition, confirming that neurons consume lactate preferentially as an oxidative energy substrate. Analysis of glutamine and glutamate peaks (singlets or multiplets) also suggests that astrocytes have a less active oxidative metabolism than neurons. In contrast, they exhibit a stronger glycolytic metabolism than neurons as indicated by their high lactate production yield. Using a mathematical model, we have estimated the relative contribution of exogenous glucose and lactate to neuronal oxidative metabolism. Under the aforementioned conditions, it represents 25% for glucose and 75% for lactate. Altogether, these results obtained on separate astrocytic and neuronal cultures support the idea that lactate, predominantly produced by astrocytes, is used as a supplementary fuel by neurons in vivo already under resting physiological conditions.

- by Luc Pellerin
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- Psychology, Cognitive Science, NMR Spectroscopy, Magnetic Resonance Spectroscopy

Nucleosome assembly proteins (Nap) are histone chaperones with vital roles in chromatin assembly and disassembly. Decoding of histone post-translational modifications by histone chaperones is central in regulation of gene expression. We probed binding interfaces in Nap-histone complexes using histone peptide interaction arrays and chemical shift perturbation techniques. Phosphorylation at H3T32 and H3T118 enhanced Nap-peptide interactions while post-translational modifications like H3K122, H4K59 and H2AK36 diminished it. Nap recognition regions in histones H2A, H2B, H3 and H4 lie in core regions of the histone octamer, and form a surface exposed contiguous patch. Nap binding sites on H2A-H2B and H3-H4 fall on opposite surfaces of histone octamer, and the latter can therefore accommodate two dimeric Nap molecules simultaneously. Interfacial residues between Nap and histone octamer overlap with route of wrapped DNA on histone octamer, implying non-concurrent residency on the octamer by either Nap or DNA. Using NMR, we mapped Nap residues that undergo chemical shift perturbations in presence of histone peptides. Taken together, we provide an architectural model of a Nap-octamer complex which likely forms during chromatin reorganisation.

- by Manickam Yogavel
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- Structural Biology, NMR Spectroscopy, Nucleosomes, Histones

Treatment of [RuHCl(CO)(PPh 3 ) 2 ] with [Hg{C 6 H 4 -2-H(O 2 C 2 H 4 )} 2 ] (1) in refluxing toluene affords [RuCl{g 2 -C,O-C 6 H 4 -2-CH(O 2 C 2 H 4 )}(CO)(PPh 3 ) 2 ] (2a). Compound 2a reacts with Ag[BF 4 ] followed by NaX (X = Br, I, F) to give [RuX{g 2 -C,O-C 6 H 4 -2-CH(O 2 C 2 H 4 )}(CO)(PPh 3 ) 2 ] (2b-d). All compounds have been characterized by elemental analysis (C and H), IR, 1 H, 13 C-{ 1 H} and 31 P-{ 1 H} NMR spectroscopy. A crystallographic study of 2a shows the presence one pair of enantiomers and one pair of diastereoisomers in the asymmetric unit. Theoretical calculations (B3LYP using the LanL2DZ basis set) on the model compounds [RuCl-(CH 3 )(EH 2 )(CO)(PH 3 ) 2 ] (E = O, S) (3a,b show that for 3a a planar geometry at the OH 2 ligand and for 3b a pyramidal structure at SH 2 is favoured. The calculated electrostatic potentials for EH 2 and the acetals CH 2 E 2 C 2 H 4 (E = O, S) are used to comment on the nature of the lone pairs at the chalcogen atoms and the coordination geometries of ether and thioether ligands. The X-ray crystallographically determined molecular structure of [BrHg(g 2 -C,O-C 6 H 4 -2-CHO 2 C 2 H 4 )] (4) is also described and model compounds studied theoretically.

- by laura leal
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- Inorganic Chemistry, Organic Chemistry, Crystallography, Organometallic Chemistry

With respect to carbon sequestration in soil, attempts have been made to identify soil organic matter (SOM) fractions that respond more rapidly to changes in land-use than bulk SOM, which could thus serve as early indicators for the overall stock change. We used a combination of physical fractionation (size and density separation) and chemical characterisation (C-to-N ratios, CuO lignin signature, 13 C NMR spectroscopy) to identify sensitive SOM fractions in an agricultural system with sandy dystric cambisols in Bavaria, Germany, 7 years after a land-use change. Land-use types included long-term arable land and grassland, and conversion from one system to the other. Soil carbon and nitrogen contents in 0 -3 cm increased from 14 to 39 mg organic carbon g À 1 soil, and from 1.7 to 3.9 mg nitrogen g À 1 soil in the following order: permanent arable, conversion grassland to arable, conversion arable to grassland, and permanent grassland. Wet sieving and ultrasonic dispersion with 22 J ml À 1 released < 5% and 60% to 80%, respectively, of the amount of particles >20 Am relative to complete dispersion. The most sensitive fraction, with respect to land-use, was SOM in the fraction >20 Am not released after sequential wet sieving and ultrasonic dispersion. In contrast, the proportion of free light (wet sieving, density < 1.8 g cm À 3 ) and occluded light (ultrasonic dispersion with 22 J ml À 1 , < 1.8 g cm À 3 ) particulate organic matter (POM) showed no clear response to land-use. The structural composition of POM indicated its vegetation origin with a selective enrichment of lignin and a loss of O-alkyl C relative to its plant precursors. Decomposition of the occluded light POM was only slightly advanced relative to the free light POM. In mineral fractions < 20 Am, SOM was significantly more transformed than in the coarse fractions, as shown by NMR spectroscopy; however, it revealed no specific land-use pattern. An exception to this was the proportion of O-alkyl C in the clay fraction, which increased with SOC content. Ratios of alkyl to O-alkyl C in mineral fractions < 20 Am differentiated samples gave a better differentiation of samples than the C-to-N ratios. We conclude that neither free nor occluded light POM are appropriate early indicators for changes in land-use at the investigated sites; however, total SOM, its distribution with depth, and SOM allocated in stable aggregates >20 Am were more sensitive. D

AbstractÐTwo novel bisnorsesquiterpenes (1R,4S,5R)-esquel-6-en-9-one (1) and (1R,4S,5S)-esquel-7-en-9-one (2) were isolated from the essential oil of Adesmia boronioides. Their structures and relative stereochemistry were elucidated by 1D and 2D NMR data, including carbon±carbon connectivity and NOESY experiments. The absolute con®guration was determined by chemical conversion of 1 into phenol 6, whose Cotton effect was compared with that of cacalol. The conformational behavior of the new compounds containing the hydrindane skeleton was studied by molecular mechanics. Compound 1 possesses a very pleasant fruity odor. q . Structure and absolute con®guration of esquelane derivatives 1±4, indane derivatives 5 and 6, and cacalol .

- by Arnaldo Bandoni and +1
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- Organic Chemistry, NMR Spectroscopy, Molecular Mechanics, Essential Oil

Complexes of copper (II), zinc (II), nickel (II), cobalt (II) and iron (III) with 4-methyl-7-hydroxycoumarin sodium salt (Mendiaxon, Hymecromone) were synthesized by mixing of equimolar amounts of the respective metal nitrates and 4-methyl-7-hydroxycoumarin sodium salt in water. The complexes were characterized and identified by elemental analysis, conductivities, IR, 1 H NMR spectroscopy and mass spectral data. DTA and TGA have been applied to study the compositions of the compounds. Thermal analysis of the complexes indicate the formation of compounds which correspond to the compositions Met(HL) 2 ·nH 2 O, where Met = Cu, Zn, Ni, Co; n= 2, 3 or 4 and Fe(HL) 3 ·5H 2 O. The newly synthesized compounds were assayed for acute intraperitoneal and per oral toxicity, influence on blood clotting time and the most active complex was investigated for spasmolytic activity.

- by Irena Kostova and +2
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- Organic Chemistry, NMR Spectroscopy, Magnetic Resonance Spectroscopy, Cell line

Natural dipeptide antioxidants (L-carnosine) are recieving increasing attention because of their noticeable potential as biopreservatives in food recent technology. Encapsulation of antioxidants by nanoliposomes could represent an ameliorative approach to overcome the problems related to the direct application of these antioxidant peptides in food.