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Nuclear Magnetic Resonance Spectroscopy (nuclear + magnetic_resonance_spectroscopy)
Kinds of Nuclear Magnetic Resonance Spectroscopy Selected AbstractsMolecular Dynamics of Podand Studied by Broadband Dielectric and Nuclear Magnetic Resonance Spectroscopies,,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19-20 2007Bakyt Orozbaev Abstract Nuclear magnetic resonance (NMR) and broadband dielectric spectroscopies (BDS) were used to analyze the molecular dynamics in P10.3H Podand. The temperature studies of NMR line and magnetic spin,lattice relaxation times accompanied by DS investigation enabled us to distinguish three main dynamical processes connected with the motions of the P10.3H Podand chains. In the low-temperature region the magnetic relaxation was associated with fast axial C3 rotation of methyl groups. Moreover, two other independent processes were observed and interpreted as (i) segmental motion of both oxyethylene and ethylene units, and (ii) the overall motion involved in the melting process. [source] Research Article: Fingerprinting Analysis of Saposhnikovia divaricata using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid ChromatographyJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2010Yue-Yang Xin The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar and polar extracts (control substance for plant drug [CSPD] A and B) from the roots of 12 specimens of Saposhnikovia divaricata (Turcz.) Schischk were achieved with Fourier Transform (FT)-NMR spectrometer and assigned by comparison to each other and to the 1H NMR spectra of the isolated individual compounds. These fingerprints were found to be uniform in terms of the specificity for the implication of all 12 specimens being systematically of the same origin. The uniformity was further affirmed by high performance liquid chromatography (HPLC), which also revealed exactly identical specificity for the identified S. divaricata species with the 1H NMR appearances of corresponding CSPD on the part of the composition of characteristic constituents when comparing to corresponding individual compounds. This investigation unambiguously shows that the specific signals from the chemotaxonomically significant compounds of chromones and coumarins in S. divaricata are exhibited distinctively in the composite features of both 1H NMR fingerprints and HPLC profiles. The 1H NMR and HPLC profiles established can successfully be used as reference for the authentication of the origin of S. divaricata species as well as for chemotaxonomic studies. [source] Fingerprinting Analysis of Rhizoma Chuanxiong of Commercial Types using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid Chromatography MethodJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2009Hai-Lin Qin Abstract The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar extracts (control substance for a plant drug (CSPD) A) from Rhizoma chuanxiong, the rhizomes of Ligusticum chuanxiong Hort., of seven specimens from different sources were measured on Fourier Transform (FT)-NMR spectrometer and assigned by comparing them with the 1H NMR spectra of the isolated pure compounds. The 1H NMR fingerprints showed exclusively characteristic resonance signals of the major special constituents of the plant. Although the differences in the relative intensity of the 1H NMR signals due to a discrepancy in the ratio of the major constituents among these samples could be confirmed by high performance liquid chromatography analysis, the general features of the 1H NMR fingerprint established for an authentic sample of the rhizomes of L. chuanxiong exhibited exclusive data from those special compounds and can be used for authenticating L. Chuanxiong species. [source] Characterization of Phase Separation and Thermal History Effects in Magnesium Silicate Glass Fibers by Nuclear Magnetic Resonance SpectroscopyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2009Jonathan F. Stebbins Liquid,liquid immiscibility, leading to the separation of silica-rich and silica-poor domains, is a common phenomenon in binary silicate glasses, but can be difficult to detect and characterize when rapid cooling results in nano-scale domain dimensions. 29Si nuclear magnetic resonance (NMR) spectroscopy can be very useful for detecting such phase separation, because the exclusion of paramagnetic impurity ions from the silica-rich regions can greatly slow their spin-lattice relaxation rates. Properly designed experiments can therefore largely isolate the NMR signals from high-silica and low-silica domains, and thus provide information about their proportions, compositions, and short- to intermediate-range structures. We demonstrate this approach here for fiber glasses that are predominantly magnesium, or calcium-magnesium silicates, with minor contents of alumina. For bulk compositions within the known region of stable liquid immiscibility, phase separation occurs even when extremely rapid cooling yields fibers less than 1 ,m in mean diameter. Slower cooling increases the extent of separation, while the addition of small amounts of alumina reduces it. [source] Quantitative Determination of Sodium Dodecatungstosilicate Speciation by 183W Nuclear Magnetic Resonance Spectroscopy.CHEMINFORM, Issue 41 2002Bradley J. Smith Abstract For Abstract see ChemInform Abstract in Full Text. [source] Availability of polycyclic aromatic hydrocarbons from lampblack-impacted soils at former oil-gas plant sites in California, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2007Lei Hong Abstract Lampblack-impacted soils at former oil-gas plant sites in California, USA, were characterized to assess the sorption of polycyclic aromatic hydrocarbons (PAHs) and the concentration-dependent effects of a residual oil tar phase on sorption mechanism and availability of PAHs. Nuclear magnetic resonance spectroscopy demonstrated similar aromaticity for both lampblack carbon and the oil tar phase, with pronounced resonance signals in the range of 100 to 150 ppm. Scanning-electron microscopic images revealed a physically distinct oil tar phase, especially at high concentrations in lampblack, which resulted in an organic-like film structure when lampblack particles became saturated with the oil tar. Sorption experiments were conducted on a series of laboratory-prepared lampblack samples to systematically evaluate influences of an oil tar phase on PAH sorption to lampblack. Results indicate that the sorption of PAHs to lampblack exhibits a competition among sorption phases at low oil tar contents when micro- and mesopores are accessible. When the oil tar content increases to more than 5 to 10% by weight, this tar phase fills small pores, reduces surface area, and dominates PAH sorption on lampblack surface. A new PAH partitioning model, Kd = KLB-C(1- ftar)° + ftarKtar (, = empirical exponent), incorporates these effects in which the control of PAH partitioning transits from being dominated by sorption in lampblack (KLB-C) to absorption in oil tar (Ktar), depending on the fraction of tar (ftar). This study illustrates the importance of understanding interactions among PAHs, oil tar, and lampblack for explaining the differences in availability of PAHs among site soils and, consequently, for refining site-specific risk assessment and establishing soil cleanup levels. [source] Reactivity of common functional groups with urethanes: Models for reactive compatibilization of thermoplastic polyurethane blendsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2002Qi-Wei Lu Abstract Two model urethane compounds, dibutyl 4,4,-methylenebis(phenyl carbamate) (BMB) and dioctyl 4,4,-methylenebis(phenyl carbamate) (OMO) were prepared by capping 4,4,-methylenebis(phenyl isocyanate) with n -butanol and n -octanol, respectively. The reactions of the two model urethane compounds with several small monofunctional compounds as well as two model poly(ethylene glycols) were carried out with neat mixtures at elevated temperatures. The ranking of reactivity of the functional groups with the urethanes was determined as follows,primary amine > secondary amine , hydroxyl , acid , anhydride , epoxide. Nuclear magnetic resonance spectroscopy (NMR) was used for the quantitative analysis. Fourier transform infrared spectroscopy was used to complement the NMR analysis. Conversions of carbamate in each reaction were monitored over time at constant temperature (200 °C). The reactions between OMO and primary amine were conducted at 170, 180, 190, and 200 °C and best described with a second-order bimolecular reaction model. The rate constant was estimated to be 1.8 × 10,3 L · mol,1 · s,1 and activation energy 115 kJ · mol,1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2310,2328, 2002 [source] Preparation and characterization of a polyimide nanofoam through grafting of labile poly(propylene glycol) oligomerPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2004Sang Hyub Han Abstract Preparation of a polyimide nanofoam (PI-F) for microelectronic applications was carried out using a polyimide precursor synthesized from poly[(amic acid)-co-(amic ester)] and grafted with a labile poly(propylene glycol) (PPG) oligomer. Polyimide precursor was synthesized by partial esterification of poly(amic acid) (PAA) derived from pyromellitic dianhydride (PMDA) and 4,4,-oxydianiline (ODA). The precursor was then grafted with bromide-terminated poly(propylene glycol) in the presence of K2CO3 in hexamethylphosphoramide and N -methylpyrrolidone, imidized at 200°C in nitrogen and the product was subsequently decomposed in air at 300°C to eliminate the labile PPG oligomer to produce PMDA/ODA polyimide nanofoam. Nuclear magnetic resonance spectroscopy (1H-NMR) and Fourier transform infrared spectroscopy (FT-IR) techniques were used to characterize the formation of polyimide precursor and extent of grafting of PPG with polyimide. The results of thermogravimetric analysis (TGA) showed three step decomposition of nanofoam with the removal of PPG at 350°C and decomposition of polyimide at around 600°C. The polyimide nanofoams were also characterized by small angle X-ray scattering (SAXS), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The morphology showed nanophase-separated structures with uniformly distributed and non-interconnected pores of 20,40,nm in size. Dynamic mechanical analysis (DMA) indicated higher storage modulus for the foamed structure compared to the pure PI with reduction in loss tangent for the former system. Copyright © 2004 John Wiley & Sons, Ltd. [source] Clinical applications of 1H-MR spectroscopy in the evaluation of epilepsies , What do pathological spectra stand for with regard to current results and what answers do they give to common clinical questions concerning the treatment of epilepsies?ACTA NEUROLOGICA SCANDINAVICA, Issue 4 2003T. Hammen Nuclear magnetic resonance spectroscopy (1H-MRS) is a non-invasive method in detecting abnormal spectra of various brain metabolites containing N -acetylaspartate (NAA), Choline (Cho), Creatine (Cr), , -Aminobutyric acid (GABA) and Glutamate. Technical processing of the MR-systems, improved automated shimming methods and further development of special shim coils increase the magnetic field homogeneity and lead to a better spectral quality and spectral resolution. The handling of the systems becomes more user-friendly and is more likely to be used in routine diagnostics. The 1H-MRS has become a diagnostic tool for assessing a number of diseases of the central nervous system mainly including epilepsies and brain tumours. The role of 1H-MRS in the assessment of epilepsies will probably increase in future. In the following article, the principles of 1H-MRS and an overview of it in the evaluation and treatment of epilepsies with special regard to temporal lobe epilepsies (TLE) has been illustrated. [source] Derivatization reaction of the mycotoxin moniliformin with 1,2-diamino-4,5-dichlorobenzene: structure elucidation of an unexpected reaction product by liquid chromatography/tandem mass spectrometry and liquid chromatography/nuclear magnetic resonance spectroscopyJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2003Peter Zöllner Abstract The derivatization reaction of the mycotoxin moniliformin with 1,2-diamino-4,5-dichlorobenzene was previously introduced to improve distinctly the sensitivity of an assay applying high-performance liquid chromatography prior to fluorescence detection. In the course of the implementation of this derivatization approach into a liquid chromatographic/mass spectrometric method, an unexpected derivatization product has now been discovered by mass spectrometry. In order to elucidate its structure, detailed investigations with liquid chromatography/tandem mass spectrometry and liquid chromatography coupled on-line with NMR spectroscopy were performed. These studies give evidence for a heterocyclic structure that has been formed by the loss of one water and one carbon monoxide molecule. A reasonable mechanism for this derivatization reaction is proposed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Preparation, characterization, and properties of fluorene-containing benzoxazine and its corresponding cross-linked polymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2010Ying-Ling Liu Abstract A benzoxazine compound (FDP-FBz), which possesses a fluorene group and two terminal furan groups, and its corresponding cross-linked polymer (CR-FDP-FBz) have been prepared using 4,4,-(9-fluorenylidene)diphenol (FDP), furfurylamine, and formaldehyde as precursors. The chemical structure of FDP-FBz has been characterized with Fourier-transform infrared and 1H nuclear magnetic resonance spectroscopies. FDP-FBz displays a melting point at about 173 °C and a processing window of 52 °C as well as good solubility in common organic solvents. As a result, FDP-FBz can be fabricated in both molten and solution processes. Under an excitation at 365 nm, FDP-FBz exhibits a photoluminescent (PL) emission at about 445 nm. The PL intensity of FDP-FBz is as high as sixfolds of the intensity recorded with FDP. CR-FDP-FBz displays a glass transition temperature of 215 °C, a high storage modulus of 3.1 GPa, a 10% weight loss at 384 °C, and a high char yield of 56 wt % (900 °C, in nitrogen). Moreover, CR-FDP-FBz has a high refractive index of about 1.65 as a result of incorporating fluorene groups to its structure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4020,4026, 2010 [source] Hyperbranched polycarbosiloxane with dendritic boron cores: Synthesis, characterization, and structure regulationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2006Jie Kong Abstract The synthesis, characterization, and structure regulation of hyperbranched polycarbosiloxane with dendritic boron cores were realized in this paper. First, dendritic boron core was synthesized via hydroboration with borane dimethylsulfide and bis(allyloxy)dimethylsilane. Then, the hyperbranched polycarbosiloxanes with dendritic boron cores were synthesized via hydrosilylation with AB2 type monomer of bis(allyloxy)methylsilane and dendritic boron cores. The molecular structures of the dendritic boron core and resulting hyperbranched polymers were characterized by using Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, and 13C nuclear magnetic resonance spectroscopies. Size exclusion chromatography/multiangle laser light scattering analysis reveals that the structures of hyperbranched polycarbosiloxane can be regulated effectively by incorporation of functional dendritic boron cores. Compared with hyperbranched polycarbosiloxane of the same molecular weight level, the hyperbranched polycarbosiloxane with dendritic boron cores presents narrower molecular weight distribution as well as much smaller hydrodynamic radius and intrinsic viscosity. Thermalgravimetric analyzer analysis indicates that both the decomposition temperature and ceramic yields are increased as the results of the incorporation of dendritic boron cores into hyperbranched polycarbosiloxane. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3930,3941, 2006 [source] Synthesis and vibrational analysis of N-(2,-Furyl)-ImidazoleJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2009A. E. Ledesma Abstract The N-(2,-furyl)-imidazole (1) has been prepared and characterized using infrared, Raman and multidimensional nuclear magnetic resonance spectroscopies. Theoretical calculations have been carried out by employing the Density Functional Theory (DFT) method, in order to optimize the geometry of their two conformers in the gas phase and to support the assignments of the vibrational bands of 1 to their normal modes. For a complete assignment of the compound, DFT calculations were combined with Scaled Quamtum Mecanic Force Field (SQMFF) methodology in order to fit the theoretical wavenumber values to the experimental one. Furthermore, Natural Bond Orbital (NBO) and topological properties by Atoms In Molecules (AIM) calculations were performed to analyze the nature and magnitude of the intramolecular interactions. The result reveals that two conformers are expected in liquid phase. Copyright © 2009 John Wiley & Sons, Ltd. [source] ,-Zein secondary structure in solution by circular dichroismBIOPOLYMERS, Issue 3 2008Tatiana C. Bicudo Abstract The proline-rich N-terminal domain of ,-zein has been reported in relevant processes, which include its ability to cross the cell membranes. Evidences indicate that synthetic hexapeptide (PPPVHL), naturally found in N-terminal portion of ,-zein, can adopt the polyproline II (PPII) conformation in aqueous solution. The secondary structure of ,-zein in maize protein bodies had been analyzed by solid state Fourier transform infrared and nuclear magnetic resonance spectroscopies. However, it was not possible to measure PPII content in physiological environment since the ,-sheet and PPII signals overlap in both solid state techniques. Here, the secondary structure of ,-zein has been analyzed by circular dichroism in SDS aqueous solution with and without ditiothreitol (DTT), and in 60% of 2-propanol and water with DTT. The results show that ,-zein has high helical content in all solutions. The PPII conformation was present at about 7% only in water/DTT solution. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 175,178, 2008. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley. com [source] Analyses of second-generation ,legal highs' in the UK: Initial findingsDRUG TESTING AND ANALYSIS, Issue 8 2010Simon D. Brandt Abstract In the UK, mephedrone and other so-called ,legal high' derivatives have recently been classified as Class B, Schedule I under the Misuse of Drugs Act 1971. Since then, alternative products have been advertised on a number of websites. In order to obtain an immediate snapshot of the situation, 24 products were purchased online from 18 UK-based websites over a period of 6 weeks following the ban in April 2010. Qualitative analyses were carried out by gas chromatography ion trap mass spectrometry using electron- and chemical ionization modes, nuclear magnetic resonance spectroscopy, and comparison with reference standards. Overall, the purchased products consisted of single cathinones or cathinone mixtures including mephedrone, butylone, 4-methyl- N -ethylcathinone, flephedrone (4-fluoromethcathinone) and MDPV (3,4-methylenedioxypyrovalerone), respectively. Benzocaine, caffeine, lidocaine, and procaine were also detected. The emphasis was placed on ,Energy 1' (NRG-1), a product advertised as a legal replacement for mephedrone-type derivatives usually claiming to contain naphyrone (naphthylpyrovalerone, O-2482). It was found that 70% of NRG-1 and NRG-2 products appeared to contain a mixture of cathinones banned in April 2010 and rebranded as ,new' legal highs, rather than legal chemicals such as naphyrone as claimed by the retailers. Only one out of 13 NRG-1 samples appeared to show analytical data consistent with naphyrone. These findings also suggest that both consumers and online sellers (unlike manufacturers and wholesalers) are, most likely unknowingly, confronted with the risk of criminalization and potential harm. Copyright © 2010 John Wiley & Sons, Ltd. [source] Screening for the calstabin-ryanodine receptor complex stabilizers JTV-519 and S-107 in doping control analysisDRUG TESTING AND ANALYSIS, Issue 1 2009Mario Thevis Abstract Recent studies outlined the influence of exercise on the stability of the skeletal muscle calstabin1-ryanodine receptor1-complex, which represents a major Ca2+ release channel. The progressive modification of the type-1 skeletal muscle ryanodine receptor (RyR1) combined with reduced levels of calstabin1 and phosphodiesterase PDE4D3 resulted in a Ca2+ leak that has been a suggested cause of muscle damage and impaired exercise capacity. The use of 1,4-benzothiazepine derivatives such as the drug candidates JTV-519 and S-107 enhanced rebinding of calstabin1 to RyR1 and resulted in significantly improved skeletal muscle function and exercise performance in rodents. Due to the fact that the mechanism of RyR1 remodelling under exercise conditions were proven to be similar in mice and humans, a comparable effect of JTV-519 and S-107 on trained athletes is expected, making the compounds relevant for doping controls. After synthesis of JTV-519, S-107, and a putative desmethylated metabolite of S-107, target compounds were characterized using nuclear magnetic resonance spectroscopy and electrospray ionization (ESI),high-resolution/high-accuracy Orbitrap mass spectrometry. Collision-induced dissociation pathways were suggested based on the determination of elemental compositions of product ions and H/D-exchange experiments. The most diagnostic product ion of JTV-519 was found at m/z 188 (representing the 4-benzyl-1-methyl piperidine residue), and S-107 as well as its desmethylated analog yielded characteristic fragments at m/z 153 and 138 (accounting for 1-methoxy-4-methylsulfanyl-benzene and 4-methoxy-benzenethiol residues, respectively). The analytes were implemented in existing doping control screening procedures based on liquid chromatography, multiple reaction monitoring and simultaneous precursor ion scanning modes using a triple quadrupole mass spectrometer. Validation items such as specificity, recovery (68,92%), lower limit of detection (0.1,0.2 ng/mL), intraday (5.2,18.5%) and interday (8.7,18.8%) precision as well as ion suppression/enhancement effects were determined. Copyright © 2009 John Wiley & Sons, Ltd. [source] Characterization of biochar from fast pyrolysis and gasification systemsENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2009Catherine E. Brewer Abstract Thermochemical processing of biomass produces a solid product containing char (mostly carbon) and ash. This char can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. The most advantageous use of a given char depends on its physical and chemical characteristics, although the relationship of char properties to these applications is not well understood. Chars from fast pyrolysis and gasification of switchgrass and corn stover were characterized by proximate analysis, CHNS elemental analysis, Brunauer-Emmet-Teller (BET) surface area, particle density, higher heating value (HHV), scanning electron microscopy, X-ray fluorescence ash content analysis, Fourier transform infrared spectroscopy using a photo-acoustic detector (FTIR-PAS), and quantitative 13C nuclear magnetic resonance spectroscopy (NMR) using direct polarization and magic angle spinning. Chars from the same feedstocks produced under slow pyrolysis conditions, and a commercial hardwood charcoal, were also characterized. Switchgrass and corn stover chars were found to have high ash content (32,55 wt %), much of which was silica. BET surface areas were low (7,50 m2/g) and HHVs ranged from 13 to 21 kJ/kg. The aromaticities from NMR, ranging between 81 and 94%, appeared to increase with reaction time. A pronounced decrease in aromatic CH functionality between slow pyrolysis and gasification chars was observed in NMR and FTIR-PAS spectra. NMR estimates of fused aromatic ring cluster size showed fast and slow pyrolysis chars to be similar (,7,8 rings per cluster), while higher-temperature gasification char was much more condensed (,17 rings per cluster). © 2009 American Institute of Chemical Engineers Environ Prog, 2009 [source] A Study of the Influence of Composition on the Microstructural Properties of ZnO/Al2O3 Mixed Oxides,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2009Shaojun Miao Abstract A series of ZnO/Al2O3 mixed oxide samples with varyingZn/Al ratio is prepared by coprecipitation, ageing, drying, and calcination. Samples are investigated in the state after drying and calcination. The applied methods include X-ray diffraction, solid-state 27Al magic-angle spinning nuclear magnetic resonance spectroscopy, transmission electron microscopy and thermogravimetric experiments coupled with evolved gas analysis. Phases present in the dried precursor samples include hydrozincite, zaccagnaite, and an unknown phase. After calcination zinc oxide and spinel can be found. All results indicate the substitution of Al ions for Zn ions in zinc oxide of zinc-rich samples. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Determination of refractory organic matter in marine sediments by chemical oxidation, analytical pyrolysis and solid-state 13C nuclear magnetic resonance spectroscopyEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2008J. M. De La Rosa Summary Seeking to quantify the amount of refractory organic matter (ROM), which includes black carbon-like material (BC), in marine sediments, we have applied a two-step procedure that consists of a chemical oxidation with sodium chlorite of the demineralized sediments followed by integration of the aromatic C region in the remaining residues by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The efficacy for lignin removal was tested by analytical pyrolysis in the presence of tetramethyl ammonium hydroxide (TMAH). Riverine, estuarine and offshore marine sediment samples were collected from the southwest Atlantic coast of Spain, a site of geological and environmental interest. Measured contents of BC-like material ranged between 3.0 and 45.7% of the total organic carbon. Greater relative BC contents were found in riverine sediments close to urban areas, which show an elevated input of anthropogenic organic material. The contents of BC-like material in offshore marine sediments (5.5,6.1%) were similar to those previously reported for these kinds of samples. However, NMR and pyrolysis-GC/MS of the isolated ROM reveals that abundant refractory aliphatic organic material remains in most of the marine samples after chlorite oxidation. We suggest that this pool of aliphatic carbon may play an important role as a stable carbon pool within the global C cycle. [source] Organic phosphorus speciation and pedogenesis: analysis by solution 31P nuclear magnetic resonance spectroscopyEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2007R. W. McDowell Summary Changes in phosphorus (P) during soil development are central to the understanding of labile P for plant productivity and soil P management. We used NaOH-EDTA extraction with 31P nuclear magnetic resonance spectroscopy (31P NMR), sequential P fractionation, and general soil chemical characterization to better our understanding of P dynamics within two chronosequences (Manawatu and Reefton) and one Basalt maturity sequence under original native vegetation. With time, orthophosphate and orthophosphate monoesters tended to increase with organic C to a maximum of about two-thirds of NaOH-EDTA-extractable P in young soils (16 000 years in the Reefton chronosequence), but gradually declined thereafter to about one-third of NaOH-EDTA-extractable P in the oldest soils (130 000 years old). This coincided with a depletion of P from primary minerals (e.g. apatite) and readily available P for plant production. This depletion of inorganic P resulted in a greater reliance on organic P cycling via mineralization, hence the depletion of the normally recalcitrant monoester-P pool. Concomitantly, the build-up of labile P species (diesters and pyrophosphate) and scyllo - over myo -inositol hexakisphosphate occurred as soils developed, and might be attributed to microbial activity, including scavenging for P. This work highlights the importance of organic P cycling during pedogenesis. [source] Molecular responses of Campylobacter jejuni to cadmium stressFEBS JOURNAL, Issue 20 2008Nadeem O. Kaakoush Cadmium ions are a potent carcinogen in animals, and cadmium is a toxic metal of significant environmental importance for humans. Response curves were used to investigate the effects of cadmium chloride on the growth of Camplyobacter jejuni. In vitro, the bacterium showed reduced growth in the presence of 0.1 mm cadmium chloride, and the metal ions were lethal at 1 mm concentration. Two-dimensional gel electrophoresis combined with tandem mass spectrometry analysis enabled identification of 67 proteins differentially expressed in cells grown without and with 0.1 mm cadmium chloride. Cellular processes and pathways regulated under cadmium stress included fatty acid biosynthesis, protein biosynthesis, chemotaxis and mobility, the tricarboxylic acid cycle, protein modification, redox processes and the heat-shock response. Disulfide reductases and their substrates play many roles in cellular processes, including protection against reactive oxygen species and detoxification of xenobiotics, such as cadmium. The effects of cadmium on thioredoxin reductase and disulfide reductases using glutathione as a substrate were studied in bacterial lysates by spectrophotometry and nuclear magnetic resonance spectroscopy, respectively. The presence of 0.1 mm cadmium ions modulated the activities of both enzymes. The interactions of cadmium ions with oxidized glutathione and reduced glutathione were investigated using nuclear magnetic resonance spectroscopy. The data suggested that, unlike other organisms, C. jejuni downregulates thioredoxin reductase and upregulates other disulfide reductases involved in metal detoxification in the presence of cadmium. [source] The osmotic stress tolerance of basidiomycetous yeastsFEMS YEAST RESEARCH, Issue 4 2010Obakeng M. Tekolo Abstract The growth and accumulation of intracellular polyols at reduced water activity (aw) were studied in 40 basidiomycetous yeast strains. The growth of most strains showed greater tolerance to NaCl than sorbitol at the same aw. No strain was able to grow below 0.90aw. 13C nuclear magnetic resonance spectroscopy revealed that glycerol was the major solute accumulated intracellularly by all the yeasts when grown to 0.96aw (NaCl). Arabitol or mannitol was also accumulated in some yeasts, whereas a few only accumulated glycerol. Analysis of six yeasts in detail revealed that the intracellular glycerol concentrations of five yeasts increased significantly when grown at 0.96aw (NaCl or sorbitol) compared with growth at 0.998aw. Arabitol and mannitol concentrations also increased, but not to the same degree. Intracellular potassium concentrations decreased when grown at 0.96aw (NaCl or sorbitol) and sodium increased, but only when grown at 0.96aw (NaCl). The survival of nine strains was evaluated in soil cultures and it was found that all grew at 100% field capacity, whereas at lower field capacity, only some strains grew or survived. The growth of basidiomycetous yeasts appears to be more sensitive to reduced aw than ascomycetous yeasts. [source] Application of proton nuclear magnetic resonance spectroscopy to the study of Cryptococcus and cryptococcosisFEMS YEAST RESEARCH, Issue 4 2006Tania C. Sorrell Abstract Proton nuclear magnetic resonance spectroscopy is a nondestructive technique that identifies chemicals in solution and in living cells. It has been used in cryptococcal research to identify the primary structure of capsular glucuronoxylomannans, link cellular apoptosis susceptibility (CAS) genes to positioning of residues on the mannose backbone of glucuronoxylomannan, and verify that the cryptococcal virulence determinant, phospholipase B, is elaborated in vivo. Promising clinical applications include speciation (Cryptococcus neoformans and Cryptococcus gattii), with preliminary evidence that varieties neoformans and grubii can also be distinguished, non-invasive diagnosis of cerebral cryptococcomas, and, in cases of meningitis, monitoring therapeutic response by analysis of cerebrospinal fluid. [source] Molecular investigations into a globally important carbon pool: permafrost-protected carbon in Alaskan soilsGLOBAL CHANGE BIOLOGY, Issue 9 2010M. P. WALDROP Abstract The fate of carbon (C) contained within permafrost in boreal forest environments is an important consideration for the current and future carbon cycle as soils warm in northern latitudes. Currently, little is known about the microbiology or chemistry of permafrost soils that may affect its decomposition once soils thaw. We tested the hypothesis that low microbial abundances and activities in permafrost soils limit decomposition rates compared with active layer soils. We examined active layer and permafrost soils near Fairbanks, AK, the Yukon River, and the Arctic Circle. Soils were incubated in the lab under aerobic and anaerobic conditions. Gas fluxes at ,5 and 5 °C were measured to calculate temperature response quotients (Q10). The Q10 was lower in permafrost soils (average 2.7) compared with active layer soils (average 7.5). Soil nutrients, leachable dissolved organic C (DOC) quality and quantity, and nuclear magnetic resonance spectroscopy of the soils revealed that the organic matter within permafrost soils is as labile, or even more so, than surface soils. Microbial abundances (fungi, bacteria, and subgroups: methanogens and Basidiomycetes) and exoenzyme activities involved in decomposition were lower in permafrost soils compared with active layer soils, which, together with the chemical data, supports the reduced Q10 values. CH4 fluxes were correlated with methanogen abundance and the highest CH4 production came from active layer soils. These results suggest that permafrost soils have high inherent decomposability, but low microbial abundances and activities reduce the temperature sensitivity of C fluxes. Despite these inherent limitations, however, respiration per unit soil C was higher in permafrost soils compared with active layer soils, suggesting that decomposition and heterotrophic respiration may contribute to a positive feedback to warming of this eco region. [source] Microwave-assisted depolymerization of poly(ethylene terephthalate) [PET] at atmospheric pressureADVANCES IN POLYMER TECHNOLOGY, Issue 4 2006Mir Mohammad Alavi Nikje Abstract Microwave-assisted hydroglycolysis of poly(ethylene terephthalate) using an excess of methanol, ethanol, 1-butanol, 1-pentanol, and 1-hexanol in the presence of different simple basic catalysts, namely, potassium hydroxide, sodium hydroxide, sodium acetate, and zinc acetate, is reported. Reactions were performed at short times without any side reactions, namely, oxidation of ethylene glycol. The products terephthalic acid and ethylene glycol were obtained in their pure form with sufficiently high yields with potassium hydroxide. The purified product was characterized by IR and nuclear magnetic resonance spectroscopy. The process of hydroglycolysis reported here is economically viable since yields of recycled products are high, and it has potential for further improvement to produce useful products. This process is of economic interest because much of the raw materials can be recovered and used for virgin PET resin synthesis. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 25:242,246, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20080 [source] Synthesis and characterization of photopatternable epoxy hybrid materials for the fabrication of thick and thermally stable microstructures with a high aspect ratioJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Kyung Ho Jung Abstract Photosensitive cycloaliphatic-epoxy oligosiloxane was synthesized using a nonhydrolytic sol,gel reaction for the fabrication of thick and thermally stable microstructures with high aspect ratios. Its formation was confirmed by 29Si and 1H nuclear magnetic resonance spectroscopy, small-angle neutron scattering, and Fourier transform infrared spectroscopy. Photocuring of cycloaliphatic-epoxy oligosiloxane resin resulted in a thermally stable epoxy hybrid material (epoxy hybrimer). Micropatterns with a high aspect ratio (>5), an excellent sidewall shape, and low shrinkage were fabricated directly from these materials using a simple photolithographic process. The fabricated micropattern sustained temperatures of up to 250°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Protein disaggregation and refolding using high hydrostatic pressureJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2007David J Phelps Abstract Production of recombinant proteins often leads to aggregate formation. These aggregates may make it impossible to solubilize the protein for downstream applications such as assay development or structural studies by X-ray crystallography or nuclear magnetic resonance spectroscopy. High hydrostatic pressure technology has been developed which offers significant advantages over traditional methods of protein disaggregation and refolding. Pressure induced disruption of protein aggregates and subsequent refolding can take place at high concentrations in a single process step, without the need for high concentrations of chaotropic agents. Copyright © 2007 Society of Chemical Industry [source] Chiral discrimination via nuclear magnetic shielding polarisabilities from NMR spectroscopy: Theoretical study of (Ra)-1,3-dimethylallene, (2R)-2-methyloxirane, and (2R)- N -methyloxaziridineJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2007R. Zanasi Abstract Three medium-size optically active molecules have been studied to make a guess at candidates suitable for chiral discrimination in an isotropic medium via nuclear magnetic resonance spectroscopy. The criterion for experimental detection is given by the magnitude of the isotropic part of nuclear magnetic shielding polarisability tensors, related to a pseudoscalar of opposite sign for the two enantiomers. The pseudoscalar shielding polarisability at the 17O nucleus in N -methyloxaziridine, calculated at the Hartree-Fock level, is ,7.8 ×10,17 mV,1. To obtain an experimentally observable magnetic field induced at the 17O nucleus in N -methyloxaziridine, electric fields as large as ,107,108 Vm,1 should be applied to the probe. The molecular electric dipole moment induced by precession of the magnetic dipole of the 17O nucleus in a magnetic field of 10 T is, in absolute value, ,8.8 × 10,42 Cm. The estimated rf-voltage at a resonance circuit is ,10 nV. Smaller values have been estimated for N, C, and H nuclei in 1,3-dimethylallene and 2-methyloxirane. © 2007 Wiley Periodicals, Inc. J Comput Chem 2007 [source] N -Cyanomethyl- N -Methyl-1-(3,,4,-methylenedioxyphenyl)-2-propylamine: An MDMA Manufacturing By-ProductJOURNAL OF FORENSIC SCIENCES, Issue 5 2008Helen Salouros B.Sc. Abstract:, This paper describes the structural elucidation of a compound produced during the synthesis of 3,4-methylenedioxymethylamphetamine (MDMA) via the reductive amination of 3,4-methylenedioxyphenyl-2-propanone (3,4-MDP-2-P) with methylamine and sodium cyanoborohydride. The compound was isolated from MDMA by column chromatography, proton and carbon nuclear magnetic resonance spectroscopy, LC/mass spectrometry, and total synthesis were used to identify the compound as N -cyanomethyl- N -methyl-1-(3,,4,-methylenedioxyphenyl)-2-propylamine. This compound has been identified as a potential synthetic route marker for the reductive amination of 3,4-MDP-2-P with methylamine and sodium cyanoborohydride and as such it should prove valuable to forensic scientists engaged in profiling illicit drugs. Profiling MDMA can provide useful information to law enforcement agencies relating to synthetic route, precursor chemicals and reagents employed and may be used for comparative analyses of different drug seizures. This paper also describes the structural elucidation of the analogous methylamphetamine synthetic route marker compound, N -cyanomethyl- N -methyl-1-phenyl-2-propylamine, produced during the reductive amination of phenyl-2-propanone using methylamine and sodium cyanoborohydride. [source] Methyl 3-[3,,4,-(methylenedioxy)phenyl]-2-methyl glycidate: An Ecstasy Precursor Seized in Sydney, AustraliaJOURNAL OF FORENSIC SCIENCES, Issue 4 2007Michael Collins Ph.D. Abstract:, Five 44 gallon drums labeled as glycidyl methacrylate were seized by the Australian Customs Service and the Australian Federal Police at Port Botany, Sydney, Australia, in December 2004. Each drum contained a white, semisolid substance that was initially suspected to be 3,4-methylenedioxymethylamphetamine (MDMA). Gas chromatography,mass spectroscopy (GC/MS) analysis demonstrated that the material was neither glycidyl methacrylate nor MDMA. Because intelligence sources employed by federal agents indicated that this material was in some way connected to MDMA production, suspicion fell on the various MDMA precursor chemicals. Using a number of techniques including proton nuclear magnetic resonance spectroscopy (1H NMR), carbon nuclear magnetic resonance spectroscopy (13C NMR), GC/MS, infrared spectroscopy, and total synthesis, the unknown substance was eventually identified as methyl 3-[3,,4,(methylenedioxy)phenyl]-2-methyl glycidate. The substance was also subjected to a published hydrolysis and decarboxylation procedure and gave a high yield of the MDMA precursor chemical, 3,4-methylenedioxyphenyl-2-propanone, thereby establishing this material as a "precursor to a precursor." [source] | ||||||||||||||||||||||||||||||||||||||||