Sample records for 13c nmr spectral

  1. Spectral Editing in 13 C MAS NMR under Moderately Fast

    E-print Network

    Frydman, Lucio

    Spectral Editing in 13 C MAS NMR under Moderately Fast Spinning Conditions1 Enrico De Vita-angle spinning (10­14 kHz MAS), CH and CH2 moieties behave to a large extent as if they were effectively isolated), magic-angle spinning (MAS), and efficient forms of proton decoupling has made the acquisition of 13 C

  2. 13C NMR spectral characterization of epimeric rotenone and some related tetrahydrobenzopyranofurobenzopyranones

    USGS Publications Warehouse

    Abidi, S.L.; Abidi, M.S.

    1983-01-01

    The 13C nuclear magnetic resonance (nmr) spectra of epimers of rotenone and four 12a-hydroxy-analogues were examined to determine the stereochemical effect of the B/C ring fusion involving the 6a- and 12a-carbon centers. Chemical shift differences between the epimeric carbon resonances of cis- and trans-6a,12a-compounds were notably larger than those of diastereoisomers derived from the same B/C ring junction stereochemistry. Results of the spectral analysis have been useful for the quantification of mixtures of epimers and for the measurement of rates of epimerization and oxygenation.

  3. (1)H, (13)C and (15)N NMR spectral assignments for new triazapentalene derivatives.

    PubMed

    Palmas, Pascal; Nyffenegger, Coralie; Pasquinet, Eric; Guillaumet, Gérald

    2009-09-01

    Mesomeric heteropentalene betaines are conjugated fused polyheterocyclic structures that represent interesting intermediates for organic synthesis. Five such structures, containing at least four nitrogen atoms and various substituents, have been characterized by (1)H, (13)C and (15)N NMR. We report, apparently for the first time, nitrogen NMR data and coupling information on such systems. Inter-ring long-range correlations across five bonds with (15)N ((5)J(HN)) and up to seven bonds with (13)C ((6)J(HC) and (7)J(HC)) were observed in HSQC experiments. The incorporation of an electron-withdrawing substituent such as NO(2) was observed to cause an increase in the magnitude of the remote couplings and deshielding of nearby protons, carbons and on all nitrogen atoms of the structure, including remote ones situated on other cycles. PMID:19475541

  4. (13)C NMR Metabolomics: INADEQUATE Network Analysis.

    PubMed

    Clendinen, Chaevien S; Pasquel, Christian; Ajredini, Ramadan; Edison, Arthur S

    2015-06-01

    The many advantages of (13)C NMR are often overshadowed by its intrinsically low sensitivity. Given that carbon makes up the backbone of most biologically relevant molecules, (13)C NMR offers a straightforward measurement of these compounds. Two-dimensional (13)C-(13)C correlation experiments like INADEQUATE (incredible natural abundance double quantum transfer experiment) are ideal for the structural elucidation of natural products and have great but untapped potential for metabolomics analysis. We demonstrate a new and semiautomated approach called INETA (INADEQUATE network analysis) for the untargeted analysis of INADEQUATE data sets using an in silico INADEQUATE database. We demonstrate this approach using isotopically labeled Caenorhabditis elegans mixtures. PMID:25932900

  5. Complete 1H-NMR and 13C-NMR spectral analysis of the pairs of 20(S) and 20(R) ginsenosides

    PubMed Central

    Yang, Heejung; Kim, Jeom Yong; Kim, Sun Ok; Yoo, Young Hyo; Sung, Sang Hyun

    2014-01-01

    Background Ginsenosides, the major ingredients of Panax ginseng, have been studied for many decades in Asian countries as a result of their wide range of pharmacological properties. The less polar ginsenosides, with one or two sugar residues, are not present in nature and are produced during manufacturing processes by methods such as heating, steaming, acid hydrolysis, and enzyme reactions. 1H-NMR and 13C-NMR spectroscopic data for the identification of the less polar ginsenosides are often unavailable or incomplete. Methods We isolated 21 compounds, including 10 pairs of 20(S) and 20(R) less polar ginsenosides (1–20), and an oleanane-type triterpene (21) from a processed ginseng preparation and obtained complete 1H-NMR and 13C-NMR spectroscopic data for the following compounds, referred to as compounds 1–21 for rapid identification: 20(S)-ginsenosides Rh2 (1), 20(R)-Rh2 (2), 20(S)-Rg3 (3), 20(R)-Rg3 (4), 6?-O-acetyl-20(S)-Rh2 [20(S)-AcetylRh2] (5), 20(R)-AcetylRh2 (6), 25-hydroxy-20(S)-Rh2 (7), 25-hydroxy-20(S)-Rh2 (8), 20(S)-Rh1 (9), 20(R)-Rh1 (10), 20(S)-Rg2 (11), 20(R)-Rg2 (12), 25-hydroxy-20(S)-Rh1 (13), 25-hydroxy-20(R)-Rh1 (14), 20(S)-AcetylRg2 (15), 20(R)-AcetylRg2 (16), Rh4 (17), Rg5 (18), Rk1 (19), 25-hydroxy-Rh4 (20), and oleanolic acid 28-O-?-D-glucopyranoside (21). PMID:25378994

  6. Separation of floridoside and isofloridosides by HPLC and complete (1)H and (13)C NMR spectral assignments for D-isofloridoside.

    PubMed

    Bondu, Stéphanie; Kervarec, Nelly; Deslandes, Eric; Pichon, Roger

    2007-11-26

    Isofloridosides (1-O-alpha-D-galactopyranosylglycerol) and floridoside (2-O-alpha-D-galactopyranosylglycerol) were extracted from the red alga Porphyra umbilicalis (Linné) Kützing (Bangiales, Rhodophyta). Their separation was achieved by HPLC (NH(2) P50 column) after successive purification of the crude extract by ion-exchange chromatography and HPLC (Sugar-Pak TM1 column). 1D and 2D NMR spectroscopy experiments allowed to completely assign the (1)H and (13)C spectra of D-isofloridoside. PMID:17765883

  7. Assignments of 1H and 13C NMR spectral data for ondansetron and its two novel metabolites, 1-hydroxy-ondansetron diastereoisomers.

    PubMed

    Duan, Mingyu; Huang, Haihua; Li, Xinnan; Chen, Xiaoyan; Zhong, Dafang

    2006-10-01

    Assignments of 1H and 13C NMR chemical shifts were made by means of heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlation (HMBC) experiments for ondansetron, and by means of 1H-1H correlation spectroscopy (1H-1H COSY) and two-dimensional nuclear Overhauser effect spectroscopy (NOESY) experiments for two novel metabolites (M1 and M2) of ondansetron. These two metabolites were isolated for the first time from Mucor circinelloides. PMID:16835896

  8. Functional groups identified by solid state 13C NMR spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Animal manure is generally high in organic matter intensity so it is well suitable for 13C nuclear magnetic resonance (NMR) analysis. Solid-state 13C NMR techniques used in characterizing organic matter and its components include, but are not limited to, cross-polarization /magic angle spinning (CP...

  9. Whole-core analysis by sup 13 C NMR

    SciTech Connect

    Vinegar, H.J.; Tutunjian, P.N. (Shell Development Co. (US)); Edelstein, W.A.; Roemer, P.B. (General Electric Corp. (US))

    1991-06-01

    This paper reports on a whole-core nuclear magnetic resonance (NMR) system that was used to obtain natural abundance {sup 13}C spectra. The system enables rapid, nondestructive measurements of bulk volume of movable oil, aliphatic/aromatic ratio, oil viscosity, and organic vs. carbonate carbon. {sup 13}C NMR can be used in cores where the {sup 1}H NMR spectrum is too broad to resolve oil and water resonances separately. A 5 1/4-in. {sup 13}C/{sup 1}H NMR coil was installed on a General Electric (GE) CSI-2T NMR imager/spectrometer. With a 4-in.-OD whole core, good {sup 13}C signal/noise ratio (SNR) is obtained within minutes, while {sup 1}H spectra are obtained in seconds. NMR measurements have been made of the {sup 13}C and {sup 1}H density of crude oils with a wide range of API gravities. For light- and medium-gravity oils, the {sup 13}C and {sup 1}H signal per unit volume is constant within about 3.5%. For heavy crudes, the {sup 13}C and {sup 1}H density measured by NMR is reduced by the shortening of spin-spin relaxation time. {sup 13}C and {sup 1}H NMR spin-lattice relaxation times were measured on a suite of Cannon viscosity standards, crude oils (4 to 60{degrees} API), and alkanes (C{sub 5} through C{sub 16}) with viscosities at 77{degrees}F ranging from 0.5 cp to 2.5 {times} 10{sup 7} cp. The {sup 13}C and {sup 1}H relaxation times show a similar correlation with viscosity from which oil viscosity can be estimated accurately for viscosities up to 100 cp. The {sup 13}C surface relaxation rate for oils on water-wet rocks is very low. Nonproton decoupled {sup 13}C NMR is shown to be insensitive to kerogen; thus, {sup 13}C NMR measures only the movable hydrocarbon content of the cores. In carbonates, the {sup 13}C spectrum also contains a carbonate powder pattern useful in quantifying inorganic carbon and distinguishing organic from carbonate carbon.

  10. Development of LC-13C NMR

    NASA Technical Reports Server (NTRS)

    Dorn, H. C.; Wang, J. S.; Glass, T. E.

    1986-01-01

    This study involves the development of C-13 nuclear resonance as an on-line detector for liquid chromatography (LC-C-13 NMR) for the chemical characterization of aviation fuels. The initial focus of this study was the development of a high sensitivity flow C-13 NMR probe. Since C-13 NMR sensitivity is of paramount concern, considerable effort during the first year was directed at new NMR probe designs. In particular, various toroid coil designs were examined. In addition, corresponding shim coils for correcting the main magnetic field (B sub 0) homogeneity were examined. Based on these initial probe design studies, an LC-C-13 NMR probe was built and flow C-13 NMR data was obtained for a limited number of samples.

  11. 13 C13 C NOESY spectra of a 480 kDa protein: solution NMR of ferritin

    Microsoft Academic Search

    Manolis Matzapetakis; Paola Turano; Elizabeth C. Theil; Ivano Bertini

    2007-01-01

    Molecular size has limited solution NMR analyses of proteins. We report 13C13C NOESY experiments on a 480 kDa protein, the multi-subunit ferritin nanocage with gated pores. By exploiting 13C-resonance-specific chemical shifts and spin diffusion effects, we identified 75% of the amino acids, with intraresidue C–C\\u000a connectivities between nuclei separated by 1–4 bonds. These results show the potential of 13C13C NOESY for

  12. 13C NMR spectroscopy applications to brain energy metabolism

    PubMed Central

    Rodrigues, Tiago B.; Valette, Julien; Bouzier-Sore, Anne-Karine

    2013-01-01

    13C nuclear magnetic resonance (NMR) spectroscopy is the method of choice for studying brain metabolism. Indeed, the most convincing data obtained to decipher metabolic exchanges between neurons and astrocytes have been obtained using this technique, thus illustrating its power. It may be difficult for non-specialists, however, to grasp thefull implication of data presented in articles written by spectroscopists. The aim of the review is, therefore, to provide a fundamental understanding of this topic to facilitate the non-specialists in their reading of this literature. In the first part of this review, we present the metabolic fate of 13C-labeled substrates in the brain in a detailed way, including an overview of some general neurochemical principles. We also address and compare the various spectroscopic strategies that can be used to study brain metabolism. Then, we provide an overview of the 13C NMR experiments performed to analyze both intracellular and intercellular metabolic fluxes. More particularly, the role of lactate as a potential energy substrate for neurons is discussed in the light of 13C NMR data. Finally, new perspectives and applications offered by 13C hyperpolarization are described. PMID:24367329

  13. QUANTITATIVE SOLID-STATE 13C NMR SPECTROSCOPY OF ORGANIC MATTER FRACTIONS IN LOWLAND RICE SOILS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spin counting on solid-state **13C cross-polarization (CP) nuclear magnetic resonance (NMR) spectra of two humic fractions isolated from tropical lowland soils showed that only 32-81% of potential **13C NMR signal was detected. The observability of **13C NMR signal (Cobs) was higher in the mobile h...

  14. Structural Revision and Elucidation of the Biosynthesis of Hypodoratoxide by (13) C,(13) C COSY NMR Spectroscopy.

    PubMed

    Barra, Lena; Ibrom, Kerstin; Dickschat, Jeroen S

    2015-05-26

    Feeding of (2,3,4,5,6-(13) C5 )mevalonolactone to the fungus Hypomyces odoratus resulted in a completely labeled sesquiterpene ether. The connectivity of the carbon atoms was easily deduced from a (13) C,(13) C?COSY spectrum, revealing a structure that was different from the previously reported structure of hypodoratoxide, even though the reported (13) C?NMR data matched. A structural revision of hypodoratoxide is thus presented. Its absolute configuration was tentatively assigned from its co-metabolite cis-dihydroagarofuran. Its biosynthesis was investigated by feeding of (3-(13) C)- and (4,6-(13) C2 )mevalonolactone, which gave insights into the complex rearrangement of the carbon skeleton during terpene cyclization by analysis of the (13) C,(13) C couplings. PMID:25876559

  15. 13C NMR of Nephila clavipes major ampullate silk gland.

    PubMed

    Hijirida, D H; Do, K G; Michal, C; Wong, S; Zax, D; Jelinski, L W

    1996-12-01

    The major ampullate glands of the spider Nephila clavipes contain approximately 0.2 microliter each of a highly concentrated (approximately 50%) solution of silk fibroin. Therefore, the reservoir of silk in these glands presents an ideal opportunity to observe prefolded conformations of a protein in its native state. To this end, the structure and conformation of major ampullate gland silk fibroin within the glands of the spider N. clavipes were examined by 13C NMR spectroscopy. These results were compared to those from silk protein first drawn from the spinneret and then denatured. The 13C NMR chemical shifts, along with infrared and circular dichroism data, suggest that the silk fibroin in the glands exists in dynamically averaged helical conformations. Furthermore, there is no evidence of proline residues in U-(13)C-D-glucose-labeled silk. This transient prefolded "molten fibril" state may correspond to the silk I form found in Bombyx mori silk. There is no evidence of the final beta-sheet structure in the ampullate gland silk fibroin before final silk processing. However, the conformation of silk in the glands appears to be in a highly metastable state, as plasticization with water produces the beta-sheet structure. Therefore, the ducts connecting the ampullate glands to the spinnerets play a larger role in silk processing than previously thought. PMID:8968613

  16. 13C NMR of Nephila clavipes major ampullate silk gland.

    PubMed Central

    Hijirida, D H; Do, K G; Michal, C; Wong, S; Zax, D; Jelinski, L W

    1996-01-01

    The major ampullate glands of the spider Nephila clavipes contain approximately 0.2 microliter each of a highly concentrated (approximately 50%) solution of silk fibroin. Therefore, the reservoir of silk in these glands presents an ideal opportunity to observe prefolded conformations of a protein in its native state. To this end, the structure and conformation of major ampullate gland silk fibroin within the glands of the spider N. clavipes were examined by 13C NMR spectroscopy. These results were compared to those from silk protein first drawn from the spinneret and then denatured. The 13C NMR chemical shifts, along with infrared and circular dichroism data, suggest that the silk fibroin in the glands exists in dynamically averaged helical conformations. Furthermore, there is no evidence of proline residues in U-(13)C-D-glucose-labeled silk. This transient prefolded "molten fibril" state may correspond to the silk I form found in Bombyx mori silk. There is no evidence of the final beta-sheet structure in the ampullate gland silk fibroin before final silk processing. However, the conformation of silk in the glands appears to be in a highly metastable state, as plasticization with water produces the beta-sheet structure. Therefore, the ducts connecting the ampullate glands to the spinnerets play a larger role in silk processing than previously thought. PMID:8968613

  17. Structure of uniaxially aligned 13C labeled silk fibroin fibers with solid state 13C-NMR

    Microsoft Academic Search

    Makoto Demura; Yasunobu Yamazaki; Tetsuo Asakura; Katsuaki Ogawa

    1998-01-01

    Carbon-13 isotopic labeling of B. mori silk fibroin was achieved biosynthetically with [1-13C] glycine in order to determine the carbonyl bond orientation angle of glycine sites with the silk fibroin. Angular dependence of 13C solid state NMR spectra of uniaxially oriented silk fibroin fiber block sample due to the carbonyl 13C chemical shift anisotropy was simulated according to the chemical

  18. An in Vivo 13C NMR Analysis of the Anaerobic Yeast Metabolism of 1-13C-Glucose

    Microsoft Academic Search

    Brent J. Giles; Zenziwe Matsche; Ryan D. Egeland; Ryan A. Reed; Scott S. Morioka; Richard L. Taber

    1999-01-01

    A biochemistry laboratory experiment that studies the dynamics of the anaerobic yeast metabolism of 1-13C-D-glucose via NMR is described. Fleischmann's Active Dry yeast, under anaerobic conditions, produces primarily 2-13C-ethanol and some 1-13C-glycerol as end products. An experiment is described in which the yeast is subjected to osmotic shock from an increasing sodium chloride concentration. Under these conditions, the yeast increases

  19. (13)C and (15)N solid-state NMR studies on albendazole and cyclodextrin albendazole complexes.

    PubMed

    Ferreira, M João G; García, A; Leonardi, D; Salomon, Claudio J; Lamas, M Celina; Nunes, Teresa G

    2015-06-01

    (13)C and (15)N solid-state nuclear magnetic resonance (NMR) spectra were recorded from albendazole (ABZ) and from ABZ:?-cyclodextrin, ABZ:methyl-?-cyclodextrin, ABZ:hydroxypropyl-?-cyclodextrin and ABZ:citrate-?-cyclodextrin, which were prepared by the spray-drying technique. ABZ signals were typical of a crystalline solid for the pure drug and of an amorphous compound obtained from ABZ:cyclodextrin samples. Relevant spectral differences were correlated with chemical interaction between ABZ and cyclodextrins. The number and type of complexes revealed a strong dependence on the cyclodextrin group substituent. Solid-state NMR data were consistent with the presence of stable inclusion complexes. PMID:25843843

  20. Accurate measurements of 13C-13C distances in uniformly 13C-labeled proteins using multi-dimensional four-oscillating field solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Straasø, Lasse Arnt; Nielsen, Jakob Toudahl; Bjerring, Morten; Khaneja, Navin; Nielsen, Niels Chr.

    2014-09-01

    Application of sets of 13C-13C internuclear distance restraints constitutes a typical key element in determining the structure of peptides and proteins by magic-angle-spinning solid-state NMR spectroscopy. Accurate measurements of the structurally highly important 13C-13C distances in uniformly 13C-labeled peptides and proteins, however, pose a big challenge due to the problem of dipolar truncation. Here, we present novel two-dimensional (2D) solid-state NMR experiments capable of extracting distances between carbonyl (13C') and aliphatic (13Caliphatic) spins with high accuracy. The method is based on an improved version of the four-oscillating field (FOLD) technique [L. A. Straasø, M. Bjerring, N. Khaneja, and N. C. Nielsen, J. Chem. Phys. 130, 225103 (2009)] which circumvents the problem of dipolar truncation, thereby offering a base for accurate extraction of internuclear distances in many-spin systems. The ability to extract reliable accurate distances is demonstrated using one- and two-dimensional variants of the FOLD experiment on uniformly 13C,15N-labeled-L-isoleucine. In a more challenging biological application, FOLD 2D experiments are used to determine a large number of 13C'-13Caliphatic distances in amyloid fibrils formed by the SNNFGAILSS fibrillating core of the human islet amyloid polypeptide with uniform 13C,15N-labeling on the FGAIL fragment.

  1. Complete 1H and 13C spectral assignment of floridoside.

    PubMed

    Simon-Colin, Christelle; Kervarec, Nelly; Pichon, Roger; Deslandes, Eric

    2002-02-11

    Floridoside (2-O-alpha-D-galactopyranosylglycerol) was extracted from the red marine alga Rhodymenia palmata, and purified by ion-exchange chromatography: 1D and 2D NMR spectroscopy experiments were used to unambiguously assign the complete 1H and 13C spectra. PMID:11844498

  2. An in Vivo 13C NMR Analysis of the Anaerobic Yeast Metabolism of 1-13C-Glucose

    NASA Astrophysics Data System (ADS)

    Giles, Brent J.; Matsche, Zenziwe; Egeland, Ryan D.; Reed, Ryan A.; Morioka, Scott S.; Taber, Richard L.

    1999-11-01

    A biochemistry laboratory experiment that studies the dynamics of the anaerobic yeast metabolism of 1-13C-D-glucose via NMR is described. Fleischmann's Active Dry yeast, under anaerobic conditions, produces primarily 2-13C-ethanol and some 1-13C-glycerol as end products. An experiment is described in which the yeast is subjected to osmotic shock from an increasing sodium chloride concentration. Under these conditions, the yeast increases the ratio of glycerol to ethanol. The experiment can be accomplished in a single laboratory period.

  3. Stable isotope-enhanced two- and three-dimensional diffusion ordered 13C-NMR spectroscopy (SIE-DOSY 13C-NMR)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stable Isotope-Enhanced Diffusion Ordered (SIE-DOSY) 13C-NMR has been applied to 13C-enriched carbohydrates and has been used to determine diffusion coefficients for pentose and hexose monosaccharides, a disaccharide and a trisaccharide. These 2D spectra were obtained with as little as 8 min of acq...

  4. Quantitative solid-state 13C NMR with signal enhancement by multiple cross polarization

    NASA Astrophysics Data System (ADS)

    Johnson, Robert L.; Schmidt-Rohr, Klaus

    2014-02-01

    A simple new method is presented that yields quantitative solid-state magic-angle spinning (MAS) 13C NMR spectra of organic materials with good signal-to-noise ratios. It achieves long (>10 ms) cross polarization (CP) from 1H without significant magnetization losses due to relaxation and with a moderate duty cycle of the radio-frequency irradiation, by multiple 1-ms CP periods alternating with 1H spin-lattice relaxation periods that repolarize the protons. The new method incorporates previous techniques that yield less distorted CP/MAS spectra, such as a linear variation (“ramp”) of the radio-frequency field strength, and it overcomes their main limitation, which is T1? relaxation of the spin-locked 1H magnetization. The ramp of the radio-frequency field strength and the asymptotic limit of cross polarization makes the spectral intensity quite insensitive to the exact field strengths used. The new multiCP pulse sequence is a “drop-in” replacement for previous CP methods and produces no additional data-processing burden. Compared to the only reliable quantitative 13C NMR method for unlabeled solids previously available, namely direct-polarization NMR, the measuring time is reduced by more than a factor of 50, enabling higher-throughput quantitative NMR studies. The new multiCP technique is validated with 14-kHz MAS on amino-acid derivatives, plant matter, a highly aromatic humic acid, and carbon materials made by low-temperature pyrolysis.

  5. Quantitative solid-state 13C NMR with signal enhancement by multiple cross polarization.

    PubMed

    Johnson, Robert L; Schmidt-Rohr, Klaus

    2014-02-01

    A simple new method is presented that yields quantitative solid-state magic-angle spinning (MAS) (13)C NMR spectra of organic materials with good signal-to-noise ratios. It achieves long (>10ms) cross polarization (CP) from (1)H without significant magnetization losses due to relaxation and with a moderate duty cycle of the radio-frequency irradiation, by multiple 1-ms CP periods alternating with (1)H spin-lattice relaxation periods that repolarize the protons. The new method incorporates previous techniques that yield less distorted CP/MAS spectra, such as a linear variation ("ramp") of the radio-frequency field strength, and it overcomes their main limitation, which is T1? relaxation of the spin-locked (1)H magnetization. The ramp of the radio-frequency field strength and the asymptotic limit of cross polarization makes the spectral intensity quite insensitive to the exact field strengths used. The new multiCP pulse sequence is a "drop-in" replacement for previous CP methods and produces no additional data-processing burden. Compared to the only reliable quantitative (13)C NMR method for unlabeled solids previously available, namely direct-polarization NMR, the measuring time is reduced by more than a factor of 50, enabling higher-throughput quantitative NMR studies. The new multiCP technique is validated with 14-kHz MAS on amino-acid derivatives, plant matter, a highly aromatic humic acid, and carbon materials made by low-temperature pyrolysis. PMID:24374751

  6. Structure of uniaxially aligned 13C labeled silk fibroin fibers with solid state 13C-NMR

    NASA Astrophysics Data System (ADS)

    Demura, Makoto; Yamazaki, Yasunobu; Asakura, Tetsuo; Ogawa, Katsuaki

    1998-01-01

    Carbon-13 isotopic labeling of B. mori silk fibroin was achieved biosynthetically with [1- 13C] glycine in order to determine the carbonyl bond orientation angle of glycine sites with the silk fibroin. Angular dependence of 13C solid state NMR spectra of uniaxially oriented silk fibroin fiber block sample due to the carbonyl 13C chemical shift anisotropy was simulated according to the chemical shift transformation with Euler angles, ?F and ?F, from principal axis system (PAS) to fiber axis system (FAS). The another Euler angles, ?DCO and ?DCO, for transformation from PAS to the molecular symmetry axis were determined from the [1- 13C] glycine sequence model compounds for the silk fibroin. By the combination of these Euler angles, the carbonyl bond orientation angle with respect to FAS of the [1- 13C] glycine sites of the silk fibroin was determined to be 90 ± 5°. This value is in agreement with the X-ray diffraction and our previous solid state NMR data of B. mori silk fibroin fiber (a typical ?-pleated sheet) within experimental error.

  7. NMR structure analysis of uniformly 13C-labeled carbohydrates.

    PubMed

    Fontana, Carolina; Kovacs, Helena; Widmalm, Göran

    2014-06-01

    In this study, a set of nuclear magnetic resonance experiments, some of them commonly used in the study of (13)C-labeled proteins and/or nucleic acids, is applied for the structure determination of uniformly (13)C-enriched carbohydrates. Two model substances were employed: one compound of low molecular weight [(UL-(13)C)-sucrose, 342 Da] and one compound of medium molecular weight ((13)C-enriched O-antigenic polysaccharide isolated from Escherichia coli O142, ~10 kDa). The first step in this approach involves the assignment of the carbon resonances in each monosaccharide spin system using the anomeric carbon signal as the starting point. The (13)C resonances are traced using (13)C-(13)C correlations from homonuclear experiments, such as (H)CC-CT-COSY, (H)CC-NOESY, CC-CT-TOCSY and/or virtually decoupled (H)CC-TOCSY. Based on the assignment of the (13)C resonances, the (1)H chemical shifts are derived in a straightforward manner using one-bond (1)H-(13)C correlations from heteronuclear experiments (HC-CT-HSQC). In order to avoid the (1) J CC splitting of the (13)C resonances and to improve the resolution, either constant-time (CT) in the indirect dimension or virtual decoupling in the direct dimension were used. The monosaccharide sequence and linkage positions in oligosaccharides were determined using either (13)C or (1)H detected experiments, namely CC-CT-COSY, band-selective (H)CC-TOCSY, HC-CT-HSQC-NOESY or long-range HC-CT-HSQC. However, due to the short T2 relaxation time associated with larger polysaccharides, the sequential information in the O-antigen polysaccharide from E. coli O142 could only be elucidated using the (1)H-detected experiments. Exchanging protons of hydroxyl groups and N-acetyl amides in the (13)C-enriched polysaccharide were assigned by using HC-H2BC spectra. The assignment of the N-acetyl groups with (15)N at natural abundance was completed by using HN-SOFAST-HMQC, HNCA, HNCO and (13)C-detected (H)CACO spectra. PMID:24771296

  8. Direct (13)C NMR detection in HPLC hyphenation mode: analysis of Ganoderma lucidum terpenoids.

    PubMed

    Wubshet, Sileshi G; Johansen, Kenneth T; Nyberg, Nils T; Jaroszewski, Jerzy W

    2012-05-25

    Solid phase extraction (SPE) was introduced as a crucial step in the HPLC-SPE-NMR technique to enable online analyte enrichment from which proton-detected NMR experiments on submicrogram amounts from complex mixtures were possible. However, the significance of direct-detected (13)C NMR experiments is indubitable in simplifying structural elucidations. In the current study, we demonstrated direct (13)C NMR detection of triterpenoids from a Ganoderma lucidum extract in hyphenation mode. The combined advantage of a cryogenically cooled probe, miniaturization, and multiple trapping enabled the first reported application of HPLC-SPE-NMR analysis using direct-detected (13)C NMR spectra. HPLC column loading, accumulative SPE trappings, and the effect of different elution solvents were evaluated and optimized. A column loading of approximately 600 ?g of a prefractionated triterpenoid mixture, six trappings, and an acquisition time of 13 h resulted in spectra with adequate signal-to-noise ratios to detect all C-13 signals. PMID:22515483

  9. /sup 13/C FT-NMR analysis of the isolated by-products of TATB

    SciTech Connect

    Clink, G.L.

    1980-08-01

    A /sup 13/C NMR analysis and characterization of the isolated by-products produced in the preparation of 1,3,5-triaminotrinitrobenzene (TATB) was effected. Two additional materials, not previously reported, were isolated and identified.

  10. Long-Range Correlations between Aliphatic [superscript 13]C Nucleic in Protein MAS NMR Spectroscopy

    E-print Network

    Bayro, Marvin?J.

    Highly efficient polarization transfer can be achieved in the magic-angle spinning NMR analysis of proteins by the combination of [superscript 13]C labeling at alternating positions and band-selective radio-frequency-driven ...

  11. Applications of High-Resolution 13C and 15N n.m.r. of Solids

    Microsoft Academic Search

    J. Schaefer; E. O. Stejskal; M. D. Sefcik; R. A. McKay

    1981-01-01

    The combination of cross polarization, dipolar decoupling and magic angle spinning results in liquid-like high-resolution 13C and 15N n.m.r. spectra of a wide variety of solid materials. Structural determinations based on such 13C n.m.r. spectra include the measurement of the extent to which pyrolysed polyacrylonitrile fibres (Orlon) retain aliphatic character during the first step of the production of a carbon

  12. Analytical 13 C NMR spectroscopy of fatty quaternary amines

    Microsoft Academic Search

    E. H. Fairchild

    1982-01-01

    Natural abundance13C nuclear magnetic resonance spectroscopy (CMR) has been used for the rapid, nondestructive analysis of fatty quaternary ammonium\\u000a compounds. Quantitative analysis of mixtures of mono-, di-and tri-fatty ammonium chlorides can be accommpublished under conditions\\u000a that do not involve heat or extremes of pH and that are independent of solvent present. In order to determine optimal conditions\\u000a for quantitative studies,

  13. Solid-state (13)C NMR reveals effects of temperature and hydration on elastin.

    PubMed Central

    Perry, Ashlee; Stypa, Michael P; Tenn, Brandon K; Kumashiro, Kristin K

    2002-01-01

    Elastin is the principal protein component of the elastic fiber in vertebrate tissue. The waters of hydration in the elastic fiber are believed to play a critical role in the structure and function of this largely hydrophobic, amorphous protein. (13)C CPMAS NMR spectra are acquired for elastin samples with different hydration levels. The spectral intensities in the aliphatic region undergo significant changes as 70% of the water in hydrated elastin is removed. In addition, dramatic differences in the CPMAS spectra of hydrated, lyophilized, and partially dehydrated elastin samples over a relatively small temperature range (-20 degrees C to 37 degrees C) are observed. Results from other experiments, including (13)C T(1) and (1)H T(1 rho) measurements, direct polarization with magic-angle spinning, and static CP of the hydrated and lyophilized elastin preparations, also support the model that there is significant mobility in fully hydrated elastin. Our results support models in which water plays an integral role in the structure and proper function of elastin in vertebrate tissue. PMID:11806948

  14. Metabolite Characterization in Peritoneal Dialysis Effluent Using High-resolution 1H and 1H-13C NMR Spectroscopy

    E-print Network

    Guleria, Anupam; Rawat, Atul; Khetrapal, C L; Prasad, Narayan; Kumar, Dinesh

    2014-01-01

    Metabolite analysis of peritoneal dialysis (PD) effluent may provide information regarding onset and progression of complications associated with prolonged PD therapy. In this context, the NMR detectable small metabolites of PD effluent samples were characterized using high resolution 1H and 1H-13C NMR spectroscopy. The various spectra were recorded (at 800 MHz proton frequency) on PD effluent samples obtained after 4 hour (intraperitoneal) dwell time from patients with end stage renal failure (ESRF) and continuing normally on PD therapy. Inspite of devastating spectral feature of PD effluent due to the presence of intense resonances from glucose and lactate, we were able to identify about 53 small endogenous metabolites (including many complex coupled spin systems) and more than 90 % of the total CH cross peaks of 1H-13C HSQC spectrum were identified specific to various metabolites of PD effluent. We foresee that the characteristic fingerprints of various metabolites of control PD effluent samples will be us...

  15. 13C NMR study on helix inversion barrier in polyguanidines

    NASA Astrophysics Data System (ADS)

    Lim, A. R.; Novak, B. M.

    1999-10-01

    The activation energy of the main-chain carbons for copolymerization of both enantiomers in polyguanidines has been studied using measurements of 13C T1? relaxation times. The activation energies of main-chain carbons depend on the ratios for copolymerization of both enantiomers. The activation energies of the carbons in three polyguanidines are distinctly different from those in pure [R] and [S] polyguanidines previously reported. It is worth noting that the carbon of 24.6% EE has a larger activation energy than 48.8 and 81.7%EE polymers. This large activation energy means that the backbone mobility is hindered; we think that this prevents a smooth precession of the chain around the helix axis.

  16. Combined chemometric analysis of (1)H NMR, (13)C NMR and stable isotope data to differentiate organic and conventional milk.

    PubMed

    Erich, Sarah; Schill, Sandra; Annweiler, Eva; Waiblinger, Hans-Ulrich; Kuballa, Thomas; Lachenmeier, Dirk W; Monakhova, Yulia B

    2015-12-01

    The increased sales of organically produced food create a strong need for analytical methods, which could authenticate organic and conventional products. Combined chemometric analysis of (1)H NMR-, (13)C NMR-spectroscopy data, stable-isotope data (IRMS) and ?-linolenic acid content (gas chromatography) was used to differentiate organic and conventional milk. In total 85 raw, pasteurized and ultra-heat treated (UHT) milk samples (52 organic and 33 conventional) were collected between August 2013 and May 2014. The carbon isotope ratios of milk protein and milk fat as well as the ?-linolenic acid content of these samples were determined. Additionally, the milk fat was analyzed by (1)H and (13)C NMR spectroscopy. The chemometric analysis of combined data (IRMS, GC, NMR) resulted in more precise authentication of German raw and retail milk with a considerably increased classification rate of 95% compared to 81% for NMR and 90% for IRMS using linear discriminate analysis. PMID:26041156

  17. Dynamic nuclear polarization-enhanced 13C NMR spectroscopy of static biological solids

    NASA Astrophysics Data System (ADS)

    Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

    2013-06-01

    We explore the possibility of using dynamic nuclear polarization (DNP) to enhance signals in structural studies of biological solids by solid state NMR without sample spinning. Specifically, we use 2D 13C-13C exchange spectroscopy to probe the peptide backbone torsion angles (?, ?) in a series of selectively 13C-labeled 40-residue ?-amyloid (A?1-40) samples, in both fibrillar and non-fibrillar states. Experiments are carried out at 9.39 T and 8 K, using a static double-resonance NMR probe and low-power microwave irradiation at 264 GHz. In frozen solutions of A?1-40 fibrils doped with DOTOPA-TEMPO, we observe DNP signal enhancement factors of 16-21. We show that the orientation- and frequency-dependent spin polarization exchange between sequential backbone carbonyl 13C labels can be simulated accurately using a simple expression for the exchange rate, after experimentally determined homogeneous 13C lineshapes are incorporated in the simulations. The experimental 2D 13C-13C exchange spectra place constraints on the ? and ? angles between the two carbonyl labels. Although the data are not sufficient to determine ? and ? uniquely, the data do provide non-trivial constraints that could be included in structure calculations. With DNP at low temperatures, 2D 13C-13C exchange spectra can be obtained from a 3.5 mg sample of A?1-40 fibrils in 4 h or less, despite the broad 13C chemical shift anisotropy line shapes that are observed in static samples.

  18. Dynamic nuclear polarization-enhanced 13C NMR spectroscopy of static biological solids

    PubMed Central

    Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

    2013-01-01

    We explore the possibility of using dynamic nuclear polarization (DNP) to enhance signals in structural studies of biological solids by solid state NMR without sample spinning. Specifically, we use 2D 13C-13C exchange spectroscopy to probe the peptide backbone torsion angles (?,?) in a series of selectively 13C-labeled 40-residue ?-amyloid (A?1–40) samples, in both fibrillar and non-fibrillar states. Experiments are carried out at 9.39 T and 8 K, using a static double-resonance NMR probe and low-power microwave irradiation at 264 GHz. In frozen solutions of A?1–40 fibrils doped with DOTOPA-TEMPO, we observe DNP signal enhancement factors of 16–21. We show that the orientation- and frequency-dependent spin polarization exchange between sequential backbone carbonyl 13C labels can be simulated accurately using a simple expression for the exchange rate, after experimentally determined homogeneous 13C lineshapes are incorporated in the simulations. The experimental 2D 13C-13C exchange spectra place constraints on the ? and ? angles between the two carbonyl labels. Although the data are not sufficient to determine ? and ? uniquely, the data do provide non-trivial constraints that could be included in structure calculations. With DNP at low temperatures, 2D 13C-13C exchange spectra can be obtained from a 3.5 mg sample of A?1–40 fibrils in 4 hr or less, despite the broad 13C chemical shift anisotropy line shapes that are observed in static samples. PMID:23562665

  19. 13C-NMR spectra and contact time experiment for Skjervatjern fulvic and humic acids

    USGS Publications Warehouse

    Malcolm, R.L.

    1992-01-01

    The T(CP) and T(1p) time constants for Skjervatjern fulvic and humic acids were determined to be short with T(CP) values ranging from 0.14 ms to 0.53 ms and T(1p) values ranging from 3.3 ms to 5.9 ms. T(CP) or T(1p) time constants at a contact time of 1 ms are favorable for quantification of 13C-NMR spectra. Because of the short T(CP) values, correction factors for signal intensity for various regions of the 13C-NMR spectra would be necessary at contact times greater than 1.1 ms or less than 0.9 ms. T(CP) and T(1p) values have a limited non-homogeneity within Skjervatjern fulvic and humic acids. A pulse delay or repeat time of 700 ms is more than adequate for quantification of these 13C-NMR spectra. Paramagnetic effects in these humic substances are precluded due to low inorganic ash contents, low contents of Fe, Mn, and Co, and low organic free-radical contents. The observed T(CP) values suggest that all the carbon types in Skjervatjern fulvic and humic acids are fully cross-polarized before significant proton relaxation occurs. The 13C-NMR spectra for Skjervatjern fulvic acid is similar to most aquatic fulvic acids as it is predominantly aliphatic, low in aromaticity (fa1 = 24), low in phenolic content, high in carboxyl content, and has no resolution of a methoxyl peak. The 13C-NMR spectra for Skjervatjern humic acid is also similar to most other aquatic humic acids in that it is also predominantly aliphatic, high in aromaticity (fa1 = 38), moderate in phenolic content, moderate in carboxyl content, and has a clear resolution of a methoxyl carbon region. After the consideration of the necessary 13C-NMR experimental conditions, these spectra are considered to be quantitative. With careful consideration of the previously determined 13C-NMR experimental conditions, quantitative spectra can be obtained for humic substances in the future from the HUMEX site. Possible changes in humic substances due to acidification should be determined from 13C-NMR data.

  20. Triple resonance experiments for aligned sample solid-state NMR of 13C and 15N labeled proteins

    Microsoft Academic Search

    Neeraj Sinha; Christopher V. Grant; Sang Ho Park; Jonathan Miles Brown

    2007-01-01

    Initial steps in the development of a suite of triple-resonance 1H\\/13C\\/15N solid-state NMR experiments applicable to aligned samples of 13C and 15N labeled proteins are described. The experiments take advantage of the opportunities for 13C detection without the need for homonuclear 13C\\/13C decoupling presented by samples with two different patterns of isotopic labeling. In one type of sample, the proteins

  1. 1H, 13C and 31P MAS NMR studies of lyophilized brain tumors

    Microsoft Academic Search

    R. Marsza?ek; M. Pisklak; D. Horszty?ski; I. Wawer

    2010-01-01

    1H, 13C and 31P magic angle spinning magnetic resonance spectra (MAS NMR) of lyophilized brain tissue specimens were recorded. Among the 35 cases of brain tumors there were 24 glioblastomas, seven meningiomas and a few other types. 1H NMR measurements were performed with a MAS speed of 33kHz. The intense CH3, CH2 and CH? peaks in the 1H spectrum result

  2. Nuclear spin-lattice relaxation via paramagnetic centers in solids. 13C NMR of diamonds

    NASA Astrophysics Data System (ADS)

    Mark Henrichs, P.; Cofield, Milton L.; Young, Ralph H.; Michael Hewitt, J.

    Diamonds of gem quality give narrow 13C NMR signals (about 200 Hz width at half height) even in a spectrometer designed for use with liquids. Industrial diamond powders require magic-angle spinning to give narrow NMR resonances. Spin-lattice relaxation in the industrial powders depends on time ( t) exponentially in t {1}/{2}. A theory is developed to explain this behavior in terms of relaxation by paramagnetic centers in the absence of nuclear spin diffusion.

  3. Accurate measurements of {sup 13}C-{sup 13}C distances in uniformly {sup 13}C-labeled proteins using multi-dimensional four-oscillating field solid-state NMR spectroscopy

    SciTech Connect

    Straasø, Lasse Arnt; Nielsen, Jakob Toudahl; Bjerring, Morten; Nielsen, Niels Chr., E-mail: ncn@inano.au.dk [Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Khaneja, Navin [Division of Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)

    2014-09-21

    Application of sets of {sup 13}C-{sup 13}C internuclear distance restraints constitutes a typical key element in determining the structure of peptides and proteins by magic-angle-spinning solid-state NMR spectroscopy. Accurate measurements of the structurally highly important {sup 13}C-{sup 13}C distances in uniformly {sup 13}C-labeled peptides and proteins, however, pose a big challenge due to the problem of dipolar truncation. Here, we present novel two-dimensional (2D) solid-state NMR experiments capable of extracting distances between carbonyl ({sup 13}C?) and aliphatic ({sup 13}C{sub aliphatic}) spins with high accuracy. The method is based on an improved version of the four-oscillating field (FOLD) technique [L. A. Straasø, M. Bjerring, N. Khaneja, and N. C. Nielsen, J. Chem. Phys. 130, 225103 (2009)] which circumvents the problem of dipolar truncation, thereby offering a base for accurate extraction of internuclear distances in many-spin systems. The ability to extract reliable accurate distances is demonstrated using one- and two-dimensional variants of the FOLD experiment on uniformly {sup 13}C,{sup 15}N-labeled-L-isoleucine. In a more challenging biological application, FOLD 2D experiments are used to determine a large number of {sup 13}C?-{sup 13}C{sub aliphatic} distances in amyloid fibrils formed by the SNNFGAILSS fibrillating core of the human islet amyloid polypeptide with uniform {sup 13}C,{sup 15}N-labeling on the FGAIL fragment.

  4. Development of a 13C-Optimized 1.5-mm High Temperature Superconducting NMR Probe

    PubMed Central

    Ramaswamy, Vijaykumar; Hooker, Jerris W.; Withers, Richard S.; Nast, Robert E.; Brey, William W.; Edison, Arthur S.

    2013-01-01

    We report a 1.5-mm NMR probe based on high temperature superconductors operating at 14.1 T optimized for 13C detection. The probe has a total sample volume of about 35 microliters (?L) with an active volume of 20 ?L and provides exceptional mass sensitivity for 13C detection. The probe also has excellent 1H sensitivity and employs a 2H channel lock; 15N irradiation capability can be added in the future. The coils are cooled to about 20 K using a standard Agilent cryogenic refrigeration system, and the sample temperature is regulated near room temperature. The coil design considerations are discussed in detail. This probe is ideal for directly detected 13C NMR experiments for natural products chemistry and metabolomics applications, for which 35 ?L is an optimal sample volume. The outstanding 13C sensitivity of this probe allowed us to directly determine the 13C connectivity on 1.1 mg of natural abundance histidine using an INADEQUATE experiment. We demonstrated the utility of this probe for 13C-based metabolomics using a synthetic mixture of common natural abundance metabolites whose concentrations ranged from 1 to 5 mM (40 to 200 nmol). PMID:23969086

  5. 13C and 15N NMR spectroscopic investigation on the formation of fossil algal residues

    Microsoft Academic Search

    Heike Knicker; Alan W. Scaroni; Patrick G. Hatcher

    1996-01-01

    13C and 15N NMR spectroscopy was applied to modern (a mixed algal culture, its algaenan and its compost), ancient (algal derived sediments from Mangrove Lake, Bermuda) and fossilized algal residues (Torbanite, Green River Shale) for the purpose of establishing the forms of nitrogen algal remains and evaluating their long-term stabilities. The results indicate that proteinaceous material can resist microbial degradation

  6. Solid-state 13 C NMR analysis of size and density fractions

    E-print Network

    Long, Bernard

    C) and lignin phenol analyses, to size and density fractions of sediments influenced by either mixed in this sediment appears to be dom- inated by lignin and black carbon whereas the source of the marine endmemberSolid-state 13 C NMR analysis of size and density fractions of marine sediments: Insight

  7. QUANTITATIVE 13C NMR CHARACTERIZATION OF MILLED WOOD LIGNINS ISOLATED BY DIFFERENT MILLING TECHNIQUES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    MWL preparations prepared from finely milled wood flour produced by different milling techniques were compared by quantitative 13C NMR. Wiley wood meal was milled for either six weeks in a porcelain rotary mill with porcelain balls, or by two variations of our standard technique. Specifically the Wi...

  8. 1H and 13C Solid-state NMR of Gossypium barbadense (Pima) Cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The interaction of water with cellulose and its influence on the nuclear spin dynamics in G. barbadense (Pima) cotton were investigated by 1H and 13C solid-state NMR techniques. 1H spin diffusion results from a Goldman-Shen experiment indicate that the water is multilayered. 1H MAS experiments pro...

  9. /sup 11/B and /sup 13/C NMR studies on silica modified by borate esters

    SciTech Connect

    Kasperskii, V.A.; Brei, V.V.; Gorlov, Yu.I.; Chuiko, A.A.

    1988-07-01

    /sup 11/B and /sup 13/C NMR has been applied along with programmed desorption and boron analysis to the surface of aerosol specimens modified by trimethoxyborane and dimethoxybutylborane. It is concluded that methanol is coordinated to the boron atoms in the dimethoxyborosilyl groups.

  10. Characterizing biomass fast pyrolysis oils by 13C-NMR and chemometric analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Several biomass fast pyrolysis oils were characterized by 13C and DEPT NMR analysis to determine chemical functional group compositions as related to their energy content. Pyrolysis oils were produced from a variety of feedstocks including energy crops, woods, animal wastes and oil seed presscakes,...

  11. Adiabatic 1H decoupling scheme for very accurate intensity measurements in 13C NMR.

    PubMed

    Tenailleau, Eve; Akoka, Serge

    2007-03-01

    Adiabatic proton decoupling has been optimized in order to obtain accurate quantitative measurements of intensities on 13C NMR spectra. For each offset, the minimum adiabaticity factor (Km) reached during the pulse was computed. This K(m) profile was used to optimize the peak value and the swept frequency range of the adiabatic pulses. With a cosinus amplitude modulation, offset-independent-adiabaticity, and the M4P5-M4P9-M4P5'-M4P9' phase cycle, an accuracy of 2 per thousand for the 13C NMR measurements was reached. An approach using bi-labeled 13C acetic acid and ethanol at 99% allowed a fine experimental determination of the uniformity of the decoupling profile. The comparison with WALTZ-16 highlights the improvements in the uniformity of the proton decoupling. PMID:17142076

  12. Conformational studies by 1H and 13C NMR of lisinopril

    NASA Astrophysics Data System (ADS)

    Sakamoto, Yohko; Ishi, Tomoko

    1993-10-01

    Lisinopril, N-N-[( s-1-carboxy-3-phenylpropyl]- L-lysyl- L-proline) (MK-521), is an inhibitor of angiotensin-converting enzyme and a new drug for the treatment of hypertension. 1H and 13C NMR studies have shown that the s-cis equilibrium about the amide bond is strongly dependent on the configuration of the chiral centres. Vicinal coupling constants of stereochemical significance were obtained in deuterated solvent using NMR techniques. Comparison with values calculated for lisinopril using potential energy calculations and NMR show that lisinopril exists in preferred optimum conformation in solution.

  13. A novel approach to the rapid assignment of (13)C NMR spectra of major components of vegetable oils such as avocado, mango kernel and macadamia nut oils.

    PubMed

    Retief, Liezel; McKenzie, Jean M; Koch, Klaus R

    2009-09-01

    Assignment of (13)C nuclear magnetic resonance (NMR) spectra of major fatty acid components of South African produced vegetable oils was attempted using a method in which the vegetable oil was spiked with a standard triacylglycerol. This proved to be inadequate and therefore a new rapid and potentially generic graphical linear correlation method is proposed for assignment of the (13)C NMR spectra of major fatty acid components of apricot kernel, avocado pear, grapeseed, macadamia nut, mango kernel and marula vegetable oils. In this graphical correlation method, chemical shifts of fatty acids present in a known standard triacylglycerol is plotted against the corresponding chemical shifts of fatty acids present in the vegetable oils. This new approach (under carefully defined conditions and concentrations) was found especially useful for spectrally crowded regions where significant peak overlap occurs and was validated with the well-known (13)C NMR spectrum of olive oil which has been extensively reported in the literature. In this way, a full assignment of the (13)C{1H} NMR spectra of the vegetable oils, as well as tripalmitolein was readily achieved and the resonances belonging to the palmitoleic acid component of the triacylglycerols in the case of macadamia nut and avocado pear oil resonances were also assigned for the first time in the (13)C NMR spectra of these oils. PMID:19544589

  14. Morphology changes during radiation-thermal degradation of polyethylene and an EPDM copolymer by 13C NMR spectroscopy

    Microsoft Academic Search

    Roger A. Assink; Mathew Celina; Kenneth T. Gillen; Roger L. Clough; Todd M. Alam

    2001-01-01

    The ? radiation induced degradation of an EPDM copolymer was compared to that of a 13C enriched polyethylene at exposure temperatures of 22 and 80°C. Morphological changes were measured by MAS 13C NMR spectroscopy and DSC. By first examining the high quality and less complex spectra of 13C enriched polyethylene, a protocol for the interpretation and deconvolution of the more

  15. 1H, 13C and 31P MAS NMR studies of lyophilized brain tumors.

    PubMed

    Marsza?ek, R; Pisklak, M; Horszty?ski, D; Wawer, I

    2010-01-01

    (1)H, (13)C and (31)P magic angle spinning magnetic resonance spectra (MAS NMR) of lyophilized brain tissue specimens were recorded. Among the 35 cases of brain tumors there were 24 glioblastomas, seven meningiomas and a few other types. (1)H NMR measurements were performed with a MAS speed of 33 kHz. The intense CH(3), CH(2) and CH peaks in the (1)H spectrum result from fatty acid residues of phospholipids, which are "mobile enough" besides the anhydrous environment. (13)C CPMAS spectra revealed the resonances of creatine and guanidine carbons; the high intensity signals arise from carbonyl groups and methylene carbons of lipids. In particular we found a fraction of mobile lipids, characterized by narrow resonances and long T(1rho)(H) Overlapped resonances of phospholipids head groups contributed to the peak at 4-7 ppm in the (31)P MAS NMR spectra. Our results indicate that (1)H and (13)C MAS NMR are able to characterize tumor types: differentiate glioblastomas from meningiomas and shed light on tumor biochemical characteristics. However, water soluble metabolites are not observed and macromolecules yield broad overlapped resonances. Generally, lyophilization significantly decreases discriminative potential of NMR analysis. PMID:20133109

  16. Characterisation of the 1H and 13C NMR spectra of methylcitric acid

    NASA Astrophysics Data System (ADS)

    Krawczyk, Hanna; Martyniuk, Tomasz

    2007-06-01

    Methylcitric acid (MCA) was synthesised in Reformatsky reaction (2 RS, 3 RS stereoisomers) and in the nucleophilic addition (2 RS, 3 SR stereoisomers). The stereoselectivity of these reactions was analysed. 1H and 13C NMR spectra of diastereoisomers of methylcitric acid were recorded and interpreted. The values of 1H chemical shifts and 1H- 1H coupling constants were analysed. Proton-decoupled high-resolution 13C NMR spectra of MCA diastereoisomers were measured in a series of dilute water solutions of various acidities. These data may provide a basis for unequivocal determination of the presence of MCA in the urine samples of patients' suffering from propionic acidemia, methylmalonic aciduria, or holocarboxylase synthetase deficiency. NMR spectroscopy enables determination of MCA diastereoisomers in body fluids and can be a complementary and useful diagnostic tool.

  17. 1H and 13C NMR assignments of new methoxylated furanoflavonoids from Lonchocarpus araripensis.

    PubMed

    Lima, Almi F; Mileo, Paulo Graziane M; Andrade-Neto, Manoel; Braz-Filho, Raimundo; Silveira, Edilberto R; Pessoa, Otília Deusdênia L

    2009-02-01

    Two new polymethoxylated flavonoids, 2',5',6'-trimethoxy-[2'',3'' : 3',4']furano dihydrochalcone and 2,4',4,5-tetramethoxy-[2'',3'' : 6,7]-furanodihydroaurone, were isolated from the root barks of Lonchocarpus araripensis, along with the known compounds 3,4,5,6-tetramethoxy-[2'',3'' : 7,8]-furanoflavan, 3,6-dimethoxy-1'',1''-dimethylcromene-[2'',3'' : 7,8]-flavone, 3',4'-methylenodioxy-5,6-dimethoxy-[2'',3'' : 7,8]-furanoflavone, 3,5,6-trimethoxy-[2'',3'' : 7,8]-furanoflavanone, 3,5,6-trimethoxy-[2'',3'' : 7,8]-furanoflavone, and 6alpha-hydroxy-medicarpin. The complete (1)H and (13)C NMR assignments of the new furan flavonoids were performed using 1D and 2D pulse sequences, including COSY, HSQC, and HMBC experiments, and comparison with spectral data for analog compounds from the literature, particularly for the new furanodihydroaurone because of several inconsistencies on the carbonyl chemical shifts from the literature. PMID:18932264

  18. Heterogeneous exchange behavior of Samia cynthia ricini silk fibroin during helix–coil transition studied with 13C NMR

    Microsoft Academic Search

    Yasumoto Nakazawa; Tetsuo Asakura

    2002-01-01

    The structure and structural transition of the glycine residue adjacent to the N-terminal alanine residue of the poly(L-alanine), (Ala)12–13, region in Samia cynthia ricini silk fibroin was studied using 13C nuclear magnetic resonance (NMR). Most of the glycine carbonyl peaks in the 13C solution NMR spectrum of [1-13C]glycine-silk fibroin could be assigned to the primary structure from the comparison of

  19. 15N and13C NMR investigation of hydroxylamine-derivatized humic substances

    USGS Publications Warehouse

    Thorn, K.A.; Arterburn, J.B.; Mikita, M.A.

    1992-01-01

    Five fulvic and humic acid samples of diverse origins were derivatized with 15N-labeled hydroxylamine and analyzed by liquid-phase 15N NMR spectrometry. The 15N NMR spectra indicated that hydroxylamine reacted similarly with all samples and could discriminate among carbonyl functional groups. Oximes were the major derivatives; resonances attributable to hydroxamic acids, the reaction products of hydroxylamine with esters, and resonances attributable to the tautomeric equilibrium position between the nitrosophenol and monoxime derivatives of quinones, the first direct spectroscopic evidence for quinones, also were evident. The 15N NMR spectra also suggested the presence of nitriles, oxazoles, oxazolines, isocyanides, amides, and lactams, which may all be explained in terms of Beckmann reactions of the initial oxime derivatives. INEPT and ACOUSTIC 15N NMR spectra provided complementary information on the derivatized samples. 13C NMR spectra of derivatized samples indicated that the ketone/quinone functionality is incompletely derivatized with hydroxylamine. ?? 1991 American Chemical Society.

  20. Methylation patterns of aquatic humic substances determined by 13C NMR spectroscopy

    USGS Publications Warehouse

    Thorn, K.A.; Steelink, C.; Wershaw, R.L.

    1987-01-01

    13C NMR spectroscopy is used to examine the hydroxyl group functionality of a series of humic and fulvic acids from different aquatic environments. Samples first are methylated with 13C-labeled diazomethane. The NMR spectra of the diazomethylated samples allow one to distinguish between methyl esters of carboxylic acids, methyl ethers of phenolic hydroxyls, and methyl ethers of phenolic hydroxyls adjacent to two substituents. Samples are then permethylated with 13C-labeled methyl iodide/NaH. 13C NMR spectra of permethylated samples show that a significant fraction of the hydroxyl groups is not methylated with diazomethane alone. In these spectra methyl ethers of carbohydrate and aliphatic hydroxyls overlap with methyl ethers of phenolic hydroxyls. Side reactions of the methyltion procedure including carbon methylation in the CH3I/NaH procedure, are also examined. Humic and fulvic acids from bog, swamp, groundwater, and lake waters showssome differences in their distribution of hydroxyl groups, mainly in the concentrations of phenolic hydroxyls, which may be attributed to their different biogeochemical origins. ?? 1987.

  1. Determination of solid-state NMR structures of proteins by means of three-dimensional 15N-13C-13C dipolar correlation spectroscopy and chemical shift analysis.

    PubMed

    Castellani, Federica; van Rossum, Barth-Jan; Diehl, Annette; Rehbein, Kristina; Oschkinat, Hartmut

    2003-10-01

    In this paper, a three-dimensional (3D) NMR-based approach for the determination of the fold of moderately sized proteins by solid-state magic-angle spinning (MAS) NMR is presented and applied to the alpha-spectrin SH3 domain. This methodology includes the measurement of multiple (13)C-(13)C distance restraints on biosynthetically site-directed (13)C-enriched samples, obtained by growing bacteria on [2-(13)C]glycerol and [1,3-(13)C]glycerol. 3D (15)N-(13)C-(13)C dipolar correlation experiments were applied to resolve overlap of signals, in particular in the region where backbone carbon-carbon correlations of the C(alpha)-C(alpha), CO-CO, C(alpha)-CO, and CO-C(alpha) type appear. Additional restraints for confining the structure were obtained from phi and psi backbone torsion angles of 29 residues derived from C(alpha), C(beta), CO, NH, and H(alpha) chemical shifts. Using both distance and angular restraints, a refined structure was calculated with a backbone root-mean-square deviation of 0.7 A with respect to the average structure. PMID:14516199

  2. 13 C-NMR Study of propionate metabolism by sludges from bioreactors treating sulfate and sulfide rich wastewater

    Microsoft Academic Search

    P. N. L. Lens; C. Dijkema; A. J. M. Stams

    1998-01-01

    Applications of nuclear magnetic resonance (NMR) to study a variety of physiological and biochemical aspects of bacteria with a role in the sulfur cycle are reviewed. Then, a case-study of high resolution13 C-NMR spectroscopy on sludges from bioreactors used for treating sulfate and sulfide rich wastewaters is presented.13 C-NMR was used to study the effect of sulfate and butyrate on

  3. 1H to 13C Energy Transfer in Solid State NMR Spectroscopy of Natural Organic Systems

    NASA Astrophysics Data System (ADS)

    Berns, Anne E.; Conte, Pellegrino

    2010-05-01

    Cross polarization (CP) magic angle spinning (MAS) 13C-NMR spectroscopy is a solid state NMR technique widely used to study chemical composition of organic materials with low or no solubility in the common deuterated solvents used to run liquid state NMR experiments. Based on the magnetization transfer from abundant nuclei (with spin of 1 -2) having a high gyromagnetic ratio (?), such as protons, to the less abundant 13C nuclei with low ? values, 13C-CPMAS NMR spectroscopy is often applied in environmental chemistry to obtain quantitative information on the chemical composition of natural organic matter (NOM) (Conte et al., 2004), although its quantitative assessment is still matter of heavy debates. Many authors (Baldock et al., 1997; Conte et al., 1997, 2002; Dria et al., 2002; Kiem et al., 2000; Kögel-Knabner, 2000; Preston, 2001), reported that the application of appropriate instrument setup as well as the use of special pulse sequences and correct spectra elaboration may provide signal intensities that are directly proportional to the amount of nuclei creating a NMR signal. However, many other papers dealt with the quantitative unsuitability of 13C-CPMAS NMR spectroscopy. Among those, Mao et al. (2000), Smernik and Oades (2000 a,b), and Preston (2001) reported that cross-polarized NMR techniques may fail in a complete excitation of the 13C nuclei. In fact, the amount of observable carbons via 13C-CPMAS NMR spectroscopy appeared, in many cases, lower than that measured by a direct observation of the 13C nuclei. As a consequence, cross-polarized NMR techniques may provide spectra where signal distribution may not be representative of the quantitative distribution of the different natural organic matter components. Cross-polarization is obtained after application of an initial 90° x pulse on protons and a further spin lock pulse (along the y axis) having a fixed length (contact time) for both nuclei (1H and 13C) once the Hartmann-Hahn condition is matched. The Hartmann-Hahn condition can be expressed as ?HB1H = ?CB1C, where ?H and ?C are the gyromagnetic ratios of protons and carbons, whereas B1H and B1C are the 1H and 13C radio-frequency (r.f.) fields applied to the nuclei. The Hartmann-Hahn condition is affected by the H-C dipolar interaction strength (Stejskal & Memory, 1994). All the factors affecting dipolar interactions may mismatch the Hartmann-Hahn condition and prevent a quantitative representation of the NOM chemical composition (Conte et al., 2004). It has been reported that under low speed MAS conditions, broad matching profiles are centered around the Hartmann-Hahn condition....... With increasing spinning speed the Hartmann-Hahn matching profiles break down in a series of narrow matching bands separated by the rotor frequency (Stejskal & Memory, 1994). In order to account for the instability of the Hartmann-Hahn condition at higher rotor spin rates (>10 kHz), variable amplitude cross-polarization techniques (RAMP-CP) have been developed (Metz et al., 1996). So far, to our knowledge, the prevailing way used to obtain quantitative 13C-CPMAS NMR results was to optimize the 1H and 13C spin lock r.f. fields on simple standard systems such as glycine and to use those r.f. field values to run experiments on unknown organic samples. The aim of the present study was to experimentally evidence that the stability of the Hartmann-Hahn condition was different for different samples with a known structure. Moreover, Hartmann-Hahn profiles of four different humic acids (HAs) were also provided in order to show that the 1H/13C r.f. spin lock field strength must also be tested on the HAs prior to a quantitative evaluation of their 13C-CPMAS NMR spectra. Baldock, J.A., Oades, J.M., Nelson, P.N., Skene, T.M., Golchin, A. & Clarke, P., 1997. Assessing the extent of decomposition of natural organic materials using solid-state C-13 NMR spectroscopy. Australian Journal of Soil Research, 35, 1061-1083. Conte, P., Piccolo, A., van Lagen, B., Buurman, P. & de Jager, P.A., 1997. Quantitative Aspects of So

  4. Solid state 13C NMR characterisation study on fourth generation Ziegler-Natta catalysts.

    PubMed

    Heikkinen, Harri; Liitiä, Tiina; Virkkunen, Ville; Leinonen, Timo; Helaja, Tuulamari; Denifl, Peter

    2012-01-01

    In this study, solid state (13)C NMR spectroscopy was utilised to characterize and identify the metal-ester coordination in active fourth generation (phthalate) Ziegler-Natta catalysts. It is known that different donors affect the active species in ZN catalysts. However, there is still limited data available of detailed molecular information how the donors and the active species are interplaying. One of the main goals of this work was to get better insight into the interactions of donor and active species. Based on the anisotropy tensor values (?(11), ?(22), ?(33)) from low magic-angle spinning (MAS) (13)C NMR spectra in combination with chemical shift anisotropy (CSA) calculations (?(aniso) and ?), both the coordinative metal (Mg/Ti) and the symmetry of this interaction between metal and the internal donor in the active catalyst (MgCl(2)/TiCl(4)/electron donor) system could be identified. PMID:22425229

  5. 13C NMR studies of the molecular dynamics of chlorpromazine in solution

    NASA Astrophysics Data System (ADS)

    Sakamoto, Yohko; Ishii, Tomoko; Kurokawa, Noriko; Aoki, Toshikazu; Ohshima, Shigeru

    1996-02-01

    The optimum structure, which is expected to lead to biological activity, of chlorpromazine hydrochloride salt (compound ( I)) in solution was determined on the basis of NMR data and molecular orbital calculations; compound ( I) favours a bent structure in which the side-chain tilts toward the chlorinated benzene ring. The molecular mobility of compound ( I) in CDCl 3 and D 2O was also examined on the basis of 13C NMR spin-lattice relaxation time ( T1). T1 depends on the magnetic field strength and the solvent. The dependence indicates that the molecular mobility of compound ( I) is larger in D 2O than in CDCl 3

  6. Studies of Fossil and Modern Spore Wall Biomacromolecules using 13C Solid State NMR

    Microsoft Academic Search

    ALAN R. HEMSLEY; ANDREW C. SCOTT; PATRICK J. BARRIE; WILLIAM G. CHALONER

    1996-01-01

    A range of Carboniferous lycophyte megaspore exines have been investigated using13C magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Their composition differs considerably from sporopollenin obtained from an extant lycophyte. The differences observed result in part from varying degrees of diagenesis.Fossil fern spores, gymnosperm megaspore-membranes and pollen have also been examined. These show a similar composition to the fossil lycophyte

  7. The high resolution 13 C NMR spectrum of poly(N,N?-bis(phenoxyphenyl) pyromellitimide), (Kapton)

    Microsoft Academic Search

    J. H. O'Donnell; A. K. Whittaker

    1984-01-01

    The high resolution 13C NMR spectrum of Kapton in sulfuric acid solution is reported. Assignments to the spectrum were made by comparison with non-proton-decoupled spectra, and with improved solid-state spectra. The solid-state spectrum of the reprecipitate from a H2SO4 solution showed that no change in the chemical structure of Kapton occurred during dissolution, but that the regular morphology present in

  8. Calculation of the 13C NMR shieldings of the C0 2 complexes of aluminosilicates

    NASA Astrophysics Data System (ADS)

    Tossell, J. A.

    1995-04-01

    13C NMR shieldings have been calculated using the random-phase-approximation, localized-orbital local-origins version of ab initio coupled Hartree-Fuck perturbation theory for CO 2 and and for several complexes formed by the reaction of CO 2 with molecular models for aluminosilicate glasses, H 3TOT'H3 3-n, T,T' = Si,Al. Two isomeric forms of the CO 2-aluminosilicate complexes have been considered: (1) "CO 2-like" complexes, in which the CO 2 group is bound through carbon to a bridging oxygen and (2) "CO 3-like" complexes, in which two oxygens of a central CO 3 group form bridging bonds to the two TH 3 groups. The CO 2-like isomer of CO 2-H 3SiOSiH 3 is quite weakly bonded and its 13C isotropic NMR shielding is almost identical to that in free CO 2. As Si is progressively replaced by Al in the - H terminated aluminosilicate model, the CO 2-like isomers show increasing distortion from the free CO 2 geometry and their 13C NMR shieldings decrease uniformly. The calculated 13C shielding value for H 3AlO(CO 2)AlH 3-2 is only about 6 ppm larger than that calculated for point charge stabilized CO 3-2. However, for a geometry of H 3SiO(CO 2) AlH 3-1, in which the bridging oxygen to C bond length has been artificially increased to that found in the - OH terminated cluster (OH) 3SiO(CO 2)Al(OH) 3-1, the calculated 13C shielding is almost identical to that for free CO 2. The CO 3-like isomers of the CO 2-aluminosili-cate complexes show carbonate like geometries and 13C NMR shieldings about 4-9 ppm larger than those of carbonate for all T,T' pairs. For the Si,Si tetrahedral atom pair the CO 2-like isomer is more stable energetically, while for the Si,Al and Al,Al cases the CO 3-like isomer is more stable. Addition of Na + ions to the CO 3-2 or H 3AlO(CO 2)AlH 3-2 complexes reduces the 13C NMR shieldings by about 10 ppm. Complexation with either Na + or CO 2 also reduces the 29Si NMR shieldings of the aluminosilicate models, while the changes in 27Al shielding with Na + or CO 2 complexation are much smaller. Complexation with CO 2 greatly increases the electric field gradient at the bridging oxygen of H 3AlOAlH 3-2, raising it to a value similar to that found for Si?O?Si linkages. Comparison of these results with the experimental 13C NMR spectra support the formation of CO 2-like complexes at SiOSi bridges in albite glasses and CO 3-like complexes at SiOAl and AlOAl bridges in albite and nepheline glasses. Changes in the calculated shieldings as Na + ions are added to the complexes suggest that some of the observed complexes may be similar in their CO 2-aluminosilicate interactions, but different with respect to the positions of the charge-compensating Na + ions.

  9. Structure elucidation and NMR spectral assignment of five new xanthones from the bark of Garcinia xanthochymus.

    PubMed

    Chen, Yu; Zhong, Fangfang; He, Hongwu; Hu, Yun; Zhu, Dan; Yang, Guangzhong

    2008-12-01

    Five new xanthones, namely Garcinexanthones A-E (1-5), were isolated from the barks of Garcinia xanthochymus. Their structures were elucidated by spectral analysis, primarily NMR, MS, and UV. The complete assignments of the (1)H NMR and (13)C NMR chemical shifts for the compounds were achieved by using 1D and 2D NMR techniques, including DEPT, HSQC, and HMBC NMR experiments. PMID:18800340

  10. Determination of Spin-Lattice Relaxation of Time Using (Super 13)C NMR: An Undergraduate Physical Chemistry Laboratory Experiment

    ERIC Educational Resources Information Center

    Gasyna, Zbigniew L.; Jurkiewicz, Antoni

    2004-01-01

    An experiment designed for the physical chemistry laboratory where (super 13)C NMR is applied to determine the spin-lattice relaxation time for carbon atoms in n-hexanol is proposed. It is concluded that students learn the principles and concepts of NMR spectroscopy as well as dynamic NMR experiments.

  11. NMR Observations of 13C-Enriched Coenzyme B12 Bound to the Ribonucleotide Reductase from Lactobacillus leichmannii

    PubMed Central

    Brown, Kenneth L.; Li, Jing; Zou, Xiang

    2008-01-01

    The 13C NMR resonance and one-bond 1H-13C coupling constants of coenzyme B12 enriched in 13C in the cobalt-bound carbon have been observed in the complex of the coenzyme with the B12-dependent ribonucleotide reductase from Lactobacillus leichmannii. Neither the 13C chemical shift nor the 1H-13C coupling constants are significantly altered by binding of the coenzyme to the enzyme. The results suggest that ground state Co-C bond distortion is not utilized by this enzyme to activate coenzyme B12 for carbon-cobalt bond homolysis. PMID:17083212

  12. Improved Carbohydrate Structure Generalization Scheme for (1)H and (13)C NMR Simulations.

    PubMed

    Kapaev, Roman R; Toukach, Philip V

    2015-07-21

    The improved Carbohydrate Structure Generalization Scheme has been developed for the simulation of (13)C and (1)H NMR spectra of oligo- and polysaccharides and their derivatives, including those containing noncarbohydrate constituents found in natural glycans. Besides adding the (1)H NMR calculations, we improved the accuracy and performance of prediction and optimized the mathematical model of the precision estimation. This new approach outperformed other methods of chemical shift simulation, including database-driven, neural net-based, and purely empirical methods and quantum-mechanical calculations at high theory levels. It can process structures with rarely occurring and noncarbohydrate constituents unsupported by the other methods. The algorithm is transparent to users and allows tracking used reference NMR data to original publications. It was implemented in the Glycan-Optimized Dual Empirical Spectrum Simulation (GODESS) web service, which is freely available at the platform of the Carbohydrate Structure Database (CSDB) project ( http://csdb.glycoscience.ru ). PMID:26087011

  13. Cerebral glucose metabolism and the glutamine cycle as detected by in vivo and in vitro 13 C NMR spectroscopy

    Microsoft Academic Search

    Mar??a A Garc??a-Espinosa; Tiago B Rodrigues; Alejandra Sierra; Marina Benito; Carla Fonseca; Heather L Gray; Brenda L Bartnik; Mar??a L Garc??a-Mart??n; Paloma Ballesteros; Sebastián Cerdán

    2004-01-01

    We review briefly 13C NMR studies of cerebral glucose metabolism with an emphasis on the roles of glial energetics and the glutamine cycle. Mathematical modeling analysis of in vivo 13C turnover experiments from the C4 carbons of glutamate and glutamine are consistent with: (i) the glutamine cycle being the major cerebral metabolic route supporting glutamatergic neurotransmission, (ii) glial glutamine synthesis

  14. NMR analyses of the cold cataract. III. /sup 13/C acrylamide studies

    SciTech Connect

    Lerman, S.; Megaw, J.M.; Moran, M.N.

    1985-10-01

    /sup 13/C-enriched acrylamide was employed to further delineate the action of this compound in preventing the cold cataract phenomenon when it is incorporated (in vitro) into young human and rabbit lenses. The extent of acrylamide incorporation, in the dark and with concurrent UV exposure, was monitored by /sup 13/C NMR spectroscopy. These studies provide further evidence that UV exposure causes permanent acrylamide photobinding within the lens. In such lenses, the gamma crystallin fraction of the soluble lens proteins is affected to the greatest extent. It appears to become aggregated and/or combined with the alpha and beta fractions resulting in an apparent loss of most of the gamma monomers. There is also an age-related effect with respect to the amount of acrylamide that can be incorporated into the lens. The decrease in acrylamide incorporation with age directly parallels the age-related decline in gamma crystallin levels.

  15. Mapping monoclonal antibody structure by 2D 13C NMR at natural abundance.

    PubMed

    Arbogast, Luke W; Brinson, Robert G; Marino, John P

    2015-04-01

    Monoclonal antibodies (mAbs) represent an important and rapidly growing class of biotherapeutics. Correct folding of a mAb is critical for drug efficacy, while misfolding can impact safety by eliciting unwanted immune or other off-target responses. Robust methods are therefore needed for the precise measurement of mAb structure for drug quality assessment and comparability. To date, the perception in the field has been that NMR could not be applied practically to mAbs due to the size (?150 kDa) and complexity of these molecules, as well as the insensitivity of the method. The feasibility of applying NMR methods to stable isotope-labeled, protease-cleaved, mAb domains (Fab and Fc) has been demonstrated from both E. coli and Chinese hamster ovaries (CHO) cell expression platforms; however, isotopic labeling is not typically available when analyzing drug products. Here, we address the issue of feasibility of NMR-based mapping of mAb structure by demonstrating for the first time the application of a 2D (13)C NMR methyl fingerprint method for structural mapping of an intact mAb at natural isotopic abundance. Further, we show that 2D (13)C NMR spectra of protease-cleaved Fc and Fab fragments can provide accurate reporters on the domain structures that can be mapped directly to the intact mAb. Through combined use of rapid acquisition and nonuniform sampling techniques, we show that these Fab and Fc fingerprint spectra can be rapidly acquired in as short as approximately 30 min. PMID:25728213

  16. The binding of metal ions and angiotensin converting enzyme (ACE) inhibitor by 13C NMR

    NASA Astrophysics Data System (ADS)

    Sakamoto, Yohko; Sakamoto, Yuko; Ishii, Tomoko; Ohmoto, Taichi

    1991-06-01

    Enalaprilat (MK-422, 1- [ N- [1 (S)-carboxy-3-phenylpropyl]- L-alanyl]- L-proline (1)) and Lisinopril (MK521, N- N- [ (s)-l-carboxy-3- phenylpropyl]- L-lysyl- L-proline, (2)) exhibit the capacity to act as a chelate, unidentate or bridge towards metal ions in aqueous solution, as determined by 13C NMR. By adding metal ions, in the series of Zn 2+, Ni 2+, Pb 2+, Pd 2+ and Cd 2+, the active site of the ACE inhibitor was well defined. MK-521 was more influenced by nuclei that were distant from the active site than MK-422.

  17. 1H and 13C resonance designation of antimycin A1 by two-dimensional NMR spectroscopy

    USGS Publications Warehouse

    Abidi, S.L.; Adams, B.R.

    1987-01-01

    Complete 1H and 13C resonance assignments of antimycin A1 were accomplished by two-dimensional NMR techniques, viz. 1H homonuclear COSY correlation, heteronuclear 13C-1H chemical shift correlation and long-range heteronuclear 13C-1H COLOC correlation. Antimycin A1 was found to consist of two isomeric components in a 2:1 ratio based on NMR spectroscopic evidence. The structure of the major component was newly assigned as the 8-isopentanoic acid ester. The spectra of the minor component were consistent with the known structure of antimycin A1.

  18. Solid-state /sup 13/C NMR and X-ray diffraction of dermatan sulfate

    SciTech Connect

    Winter, W.T.; Taylor, M.G.; Stevens, E.S.; Morris, E.R.; Rees, D.A.

    1986-05-29

    Dermatan sulfate in the solid state has been studied by /sup 13/C CP/MAS nmr and X-ray diffraction in order to establish the ring conformation of the L-iduronate moiety. The solid state nmr spectrum is similar to the solution spectrum obtained previously, indicating that a ring conformation at least approximating to /sup 1/C/sub 4/ predominates in the solid state. X-ray powder diffraction data from the same sample indicate the presence of the 8-fold helix form previously observed by fiber diffraction, and interpreted in terms of a /sup 4/C/sub 1/ ring form. A likely explanation of the results is that a distorted /sup 1/C/sub 4/ L-iduronate ring conformation, not considered in the initial X-ray analysis, may emerge to provide a satisfactory interpretation of all available physical-chemical data.

  19. Imazalil–cyclomaltoheptaose (?-cyclodextrin) inclusion complex: preparation by supercritical carbon dioxide and 13C CPMAS and 1H NMR characterization

    Microsoft Academic Search

    Simona Lai; Emanuela Locci; Alessandra Piras; Silvia Porcedda; Adolfo Lai; Bruno Marongiu

    2003-01-01

    An inclusion complex between imazalil (IMZ), a selected fungicide, and cyclomaltoheptaose (?-cyclodextrin, ?CD) was obtained using supercritical fluid carbon dioxide. The best preparation conditions were determined, and the inclusion complex was investigated by means of 1H NMR spectroscopy in aqueous solution and 13C CPMAS NMR spectroscopy in the solid state. Information on the geometry of the ?CD\\/IMZ complex was obtained

  20. Signal intensities in 1H-13C CP and INEPT MAS NMR of liquid crystals

    NASA Astrophysics Data System (ADS)

    Nowacka, A.; Bongartz, N. A.; Ollila, O. H. S.; Nylander, T.; Topgaard, D.

    2013-05-01

    Spectral editing with CP and INEPT in 13C MAS NMR enables identification of rigid and mobile molecular segments in concentrated assemblies of surfactants, lipids, and/or proteins. In order to get stricter definitions of the terms "rigid" and "mobile", as well as resolving some ambiguities in the interpretation of CP and INEPT data, we have developed a theoretical model for calculating the CP and INEPT intensities as a function of rotational correlation time ?c and C-H bond order parameter SCH, taking the effects of MAS into account. According to the model, the range of ?c can at typical experimental settings (5 kHz MAS, 1 ms ramped CP at 80-100 kHz B1 fields) be divided into four regimes: fast (?c < 1 ns), fast-intermediate (?c ? 0.1 ?s), intermediate (?c ? 1 ?s), and slow (?c > 0.1 ms). In the fast regime, the CP and INEPT intensities are independent of ?c, but strongly dependent on |SCH|, with a cross-over from dominating INEPT to dominating CP at |SCH| > 0.1. In the intermediate regime, neither CP nor INEPT yield signal on account of fast T1? and T2 relaxation. In both the fast-intermediate and slow regimes, there is exclusively CP signal. The theoretical predictions are tested by experiments on the glass-forming surfactant n-octyl-?-D-maltoside, for which ?c can be varied continuously in the nano- to millisecond range by changing the temperature and the hydration level. The atomistic details of the surfactant dynamics are investigated with MD simulations. Based on the theoretical model, we propose a procedure for calculating CP and INEPT intensities directly from MD simulation trajectories. While MD shows that there is a continuous gradient of ?c from the surfactant polar headgroup towards the methyl group at the end of the hydrocarbon chain, analysis of the experimental CP and INEPT data indicates that this gradient gets steeper with decreasing temperature and hydration level, eventually spanning four orders of magnitude at completely dry conditions.

  1. Identifying Inter-Residue Resonances in Crowded 2D 13C-13C Chemical Shift Correlation Spectra of Membrane Proteins by Solid-State MAS NMR Difference Spectroscopy

    PubMed Central

    Miao, Yimin; Cross, Timothy A.; Fu, Riqiang

    2013-01-01

    The feasibility of using difference spectroscopy, i.e. subtraction of two correlation spectra at different mixing times, for substantially enhanced resolution in crowded two-dimensional 13C-13C chemical shift correlation spectra is presented. With the analyses of 13C-13C spin diffusion in simple spin systems, difference spectroscopy is proposed to partially separate the spin diffusion resonances of relatively short intra-residue distances from the longer inter-residue distances, leading to a better identification of the inter-residue resonances. Here solid-state magic-angle-spinning (MAS) NMR spectra of the full length M2 protein embedded in synthetic lipid bilayers have been used to illustrate the resolution enhancement in the difference spectra. The integral membrane M2 protein of Influenza A virus assembles as a tetrameric bundle to form a protonconducting channel that is activated by low pH and is essential for the viral lifecycle. Based on known amino acid resonance assignments from amino acid specific labeled samples of truncated M2 sequences or from time-consuming 3D experiments of uniformly labeled samples, some inter-residue resonances of the full length M2 protein can be identified in the difference spectra of uniformly 13C labeled protein that are consistent with the high resolution structure of the M2 (22–62) protein (Sharma et al. 2010). PMID:23708936

  2. 13C NMR investigation of nonenzymatic glucosylation of protein. Model studies using RNase A.

    PubMed

    Neglia, C I; Cohen, H J; Garber, A R; Ellis, P D; Thorpe, S R; Baynes, J W

    1983-12-10

    Nonenzymatic glucosylation of protein is initiated by the reversible condensation of glucose in its open chain form with the amino groups on the protein. The initial product is an aldimine (Schiff base) which cyclizes to the glycosylamine derivative. The aldimine can undergo a slow Amadori rearrangement to yield the relatively stable ketoamine adduct which is structurally analogous to fructose. 13C NMR has been used to characterize these early products of nonenzymatic glucosylation, using RNase A as a model protein. C-1 of the beta-pyranose anomer of the glycosylamine was identified at 88.8 ppm in the spectrum of RNase glucosylated approximately 1:1 with D-[1-13C]glucose. C-1 of the Amadori product was also apparent in this spectrum, resonating as a pair of intense peaks at 52.7 and 53.1 ppm. The anomeric (C-2) resonances of the Amadori adduct were seen in the spectrum of RNase glucosylated approximately 1:1 with [U-13C]glucose. This spectrum was interpreted by comparison to the spectra of reference compounds: D-fructose, fructose-glycine, N alpha-formyl-N epsilon-fructose-lysine, and glucosylated poly-L-lysine. In the protein spectrum, the most intense of the C-2 resonances was that of the beta-fructopyranose anomer at 95.8 ppm. The alpha- and beta-fructofuranose anomers were also observed at 101.7 and 99.2 ppm, respectively. One unidentified signal in the anomeric region was observed in the spectra of poly-L-lysine and RNase, both glucosylated with [U-13C]glucose; no comparable resonances were observed in the spectra of the model compounds. PMID:6643480

  3. Solid-state 13C NMR analysis of size and density fractions of marine sediments: Insight into organic carbon sources and preservation mechanisms

    NASA Astrophysics Data System (ADS)

    Dickens, Angela F.; Baldock, Jeffrey A.; Smernik, Ronald J.; Wakeham, Stuart G.; Arnarson, Thórarinn S.; Gélinas, Yves; Hedges, John I.

    2006-02-01

    Burial of organic carbon (OC) in ocean sediments acts as the ultimate long-term sink for both terrestrial and marine carbon, however, the mechanisms controlling the preservation of this carbon are poorly understood. To better understand these mechanisms, we applied solid-state 13C nuclear magnetic resonance (NMR) spectroscopy, along with elemental, stable carbon isotopic (? 13C) and lignin phenol analyses, to size and density fractions of sediments influenced by either mixed terrestrial and marine OC inputs (Washington Coast slope) or dominantly marine inputs (Mexican Margin). Elemental, isotopic and lignin analyses all reveal that within the Washington Coast sediment, the OC mixes linearly between nitrogen-poor and 13C-depleted, lignin-rich OC in the large and light fractions and nitrogen-rich and 13C-enriched, lignin-poor OC in the small and dense fractions, suggesting that this sediment contains a two-component mixture of terrestrial vascular plant- and marine-derived OC. The integral areas of each of seven NMR spectral regions in the different samples trend linearly when plotted versus ? 13C signature, with most R2 values of 0.78 or greater, demonstrating that the NMR spectra of the two sources of carbon also mix linearly between the two endmembers. The terrestrial endmember in this sediment appears to be dominated by lignin and black carbon whereas the source of the marine endmember is less clear from the NMR spectra. In contrast, all of the analyses indicate that OC in the Mexican Margin sediment fractions is homogenous and derives almost exclusively from marine sources. It appears that selective preservation of (bio)chemically recalcitrant lignin and black carbon is the primary mechanism of preservation of terrestrial OC, whereas mineral-protection is the dominant mechanism preserving marine OC in the Washington coast sediment. There is little evidence showing that either preservation mechanism functions in the Mexican Margin sediments.

  4. Identification of archaeological triterpenic resins by the non-separative techniques FTIR and 13C NMR: the case of Pistacia resin (mastic) in comparison with frankincense.

    PubMed

    Bruni, Silvia; Guglielmi, Vittoria

    2014-01-01

    The use of spectroscopic techniques such as Fourier-transform infrared (FTIR) spectroscopy and carbon 13 nuclear magnetic resonance ((13)C NMR) using the J-mod experiment is proposed as an effective alternative to gas chromatography-mass spectrometry (GC-MS) for the analysis and identification of natural resin samples found in archaeological environments. The spectral features of the most common diterpenic and triterpenic resins and also two gum-resins are reported and discussed for both techniques. The analytical procedure based on the combined use of FTIR and (13)C NMR is then applied to two archaeological samples from the Milano of the Roman age allowing their identification as Pistacia resin, or mastic, as confirmed by the traditional GC-MS method, and also elucidating some effects of aging on such material. PMID:24291439

  5. sup 13 C and sup 31 P NMR (Nuclear Magnetic Resonance) studies of prostate tumor metabolism

    SciTech Connect

    Sillerud, L.O.; Halliday, K.R.; Freyer, J.P; Griffey, R.H.; Fenoglio-Preiser, C.

    1989-01-01

    The current research on prostate cancer by NMR spectroscopy and microscopy will most significantly contribute to tumor diagnosis and characterization only if sound biochemical models of tumor metabolism are established and tested. Prior searches focused on universal markers of malignancy, have to date, revealed no universal markers by any method. It is unlikely that NMRS will succeed where other methods have failed, however, NMR spectroscopy does provide a non-invasive means to analyze multiple compounds simultaneously in vivo. In order to fully evaluate the ability of NMRS to differentiate non-malignant from malignant tissues it is necessary to determine sufficient multiple parameters from specific, well-diagnosed, histological tumor types that, in comparison to normal tissue and non-neoplastic, non-normal pathologies from which the given neoplasm must be differentiated, one has enough degrees of freedom to make a mathematically and statistically significant determination. Confounding factors may consist of tumor heterogeneity arising from regional variations in differentiation, ischemia, necrosis, hemorrhage, inflammation and the presence of intermingled normal tissue. One related aspect of our work is the development of {l brace}{sup 13}C{r brace}-{sup 1}H metabolic imaging of {sup 13}C for metabolic characterization, with enhanced spatial localization (46). This should markedly extend the range of potential clinical NMR uses because the spatial variation in prostate metabolism may prove to be just as important in tumor diagnoses as bulk (volume-averaged) properties themselves. It is our hope that NMRS and spectroscopic imaging will reveal a sound correlation between prostate metabolism and tumor properties that will be clinically straightforward and useful for diagnosis.

  6. Dynamic nuclear polarization-enhanced 1H-13C double resonance NMR in static samples below 20 K

    NASA Astrophysics Data System (ADS)

    Potapov, Alexey; Thurber, Kent R.; Yau, Wai-Ming; Tycko, Robert

    2012-08-01

    We demonstrate the feasibility of one-dimensional and two-dimensional 1H-13C double resonance NMR experiments with dynamic nuclear polarization (DNP) at 9.4 T and temperatures below 20 K, including both 1H-13C cross-polarization and 1H decoupling, and discuss the effects of polarizing agent type, polarizing agent concentration, temperature, and solvent deuteration. We describe a two-channel low-temperature DNP/NMR probe, capable of carrying the radio-frequency power load required for 1H-13C cross-polarization and high-power proton decoupling. Experiments at 8 K and 16 K reveal a significant T2 relaxation of 13C, induced by electron spin flips. Carr-Purcell experiments and numerical simulations of Carr-Purcell dephasing curves allow us to determine the effective correlation time of electron flips under our experimental conditions. The dependence of the DNP signal enhancement on electron spin concentration shows a maximum near 80 mM. Although no significant difference in the absolute DNP enhancements for triradical (DOTOPA-TEMPO) and biradical (TOTAPOL) dopants was found, the triradical produced greater DNP build-up rates, which are advantageous for DNP experiments. Additionally the feasibility of structural measurements on 13C-labeled biomolecules was demonstrated with a two-dimensional 13C-13C exchange spectrum of selectively 13C-labeled ?-amyloid fibrils.

  7. Dynamic nuclear polarization-enhanced 1H–13C double resonance NMR in static samples below 20 K

    PubMed Central

    Potapov, Alexey; Thurber, Kent R.; Yau, Wai-Ming; Tycko, Robert

    2012-01-01

    We demonstrate the feasibility of one-dimensional and two-dimensional 1H–13C double resonance NMR experiments with dynamic nuclear polarization (DNP) at 9.4 T and temperatures below 20 K, including both 1H–13C cross-polarization and 1H decoupling, and discuss the effects of polarizing agent type, polarizing agent concentration, temperature, and solvent deuteration. We describe a two-channel low-temperature DNP/NMR probe, capable of carrying the radio-frequency power load required for 1H–13C cross-polarization and high-power proton decoupling. Experiments at 8 K and 16 K reveal a significant T2 relaxation of 13C, induced by electron spin flips. Carr–Purcell experiments and numerical simulations of Carr–Purcell dephasing curves allow us to determine the effective correlation time of electron flips under our experimental conditions. The dependence of the DNP signal enhancement on electron spin concentration shows a maximum near 80 mM. Although no significant difference in the absolute DNP enhancements for triradical (DOTOPA-TEMPO) and biradical (TOTAPOL) dopants was found, the triradical produced greater DNP build-up rates, which are advantageous for DNP experiments. Additionally the feasibility of structural measurements on 13C-labeled biomolecules was demonstrated with a two-dimensional 13C13C exchange spectrum of selectively 13C-labeled ?-amyloid fibrils. PMID:22743540

  8. Localized In Vivo 1H NMR Detection of Neurotransmitter Labeling in Rat Brain During Infusion of [1-13C] D-Glucose

    E-print Network

    Jegelka, Stefanie

    Localized In Vivo 1H NMR Detection of Neurotransmitter Labeling in Rat Brain During Infusion of [1: localized 13C editing; ACED-STEAM; adiabatic broad- band decoupling; neurotransmitter labeling; [1-13C

  9. Discovering [superscript 13]C NMR, [superscript 1]H NMR, and IR Spectroscopy in the General Chemistry Laboratory through a Sequence of Guided-Inquiry Exercises

    ERIC Educational Resources Information Center

    Iler, H. Darrell; Justice, David; Brauer, Shari; Landis, Amanda

    2012-01-01

    This sequence of three guided-inquiry labs is designed for a second-semester general chemistry course and challenges students to discover basic theoretical principles associated with [superscript 13]C NMR, [superscript 1]H NMR, and IR spectroscopy. Students learn to identify and explain basic concepts of magnetic resonance and vibrational…

  10. Localized in vivo 13C-NMR of Glutamate Metabolism in the Human Brain: Initial Results at 4 Tesla

    Microsoft Academic Search

    Rolf Gruetter; Elizabeth R. Seaquist; Suckwon Kim

    1998-01-01

    Using optimized administration of 13C-labeled glucose, the time course of the specific activity of glucose was measured directly by in vivo 13C-NMR in the human brain at 4 Tesla. Subsequent label incorporation was measured at the C2, C3 and C4 positions of both glutamate and the well-resolved C2, C3 and C4 resonances of glutamine and at the C2 and C3

  11. Experimental studies of the 13C NMR of iodoalkynes in Lewis-basic solvents.

    PubMed

    Webb, Jeffrey A; Klijn, Jaap E; Hill, Philip Aru; Bennett, Jordan L; Goroff, Nancy S

    2004-02-01

    The (13)C NMR spectra of two different iodoalkynes, 1-iodo-1-hexyne (1) and diiodoethyne (2), exhibit a strong solvent dependence. Comparisons of the data with several common empirical models, including Gutmann's Donor numbers, Reichardt's E(N)(T), and Taft and Kamlet's beta and pi, demonstrate that this solvent effect arises from a specific acid-base interaction. Solvent basicity measures such as Donor numbers and beta values correlate well with the alpha-carbon chemical shift of 1, but polarity measures such as E(N)(T) and pi do not correlate. The similarity of the solvent effect for 1 and 2 suggests that carbon-carbon bond polarization may not play a role in the change in chemical shift, as previously hypothesized. PMID:14750789

  12. Conditions for (13)C NMR detection of 2-hydroxyglutarate in tissue extracts from isocitrate dehydrogenase-mutated gliomas.

    PubMed

    Pichumani, Kumar; Mashimo, Tomoyuki; Baek, Hyeon-Man; Ratnakar, James; Mickey, Bruce; DeBerardinis, Ralph J; Maher, Elizabeth A; Bachoo, Robert M; Malloy, Craig R; Kovacs, Zoltan

    2015-07-15

    (13)C NMR (nuclear magnetic resonance) spectroscopy of extracts from patient tumor samples provides rich information about metabolism. However, in isocitrate dehydrogenase (IDH)-mutant gliomas, (13)C labeling is obscured in oncometabolite 2-hydroxyglutaric acid (2HG) by glutamate and glutamine, prompting development of a simple method to resolve the metabolites. J-coupled multiplets in 2HG were similar to glutamate and glutamine and could be clearly resolved at pH 6. A cryogenically cooled (13)C probe, but not J-resolved heteronuclear single quantum coherence spectroscopy, significantly improved detection of 2HG. These methods enable the monitoring of (13)C-(13)C spin-spin couplings in 2HG expressing IDH-mutant gliomas. PMID:25908561

  13. Acetate and Bicarbonate Assimilation and Metabolite Formation in Chlamydomonas reinhardtii: A 13C-NMR Study

    PubMed Central

    Singh, Himanshu; Shukla, Manish R.; Chary, Kandala V. R.; Rao, Basuthkar J.

    2014-01-01

    Cellular metabolite analyses by 13C-NMR showed that C. reinhardtii cells assimilate acetate at a faster rate in heterotrophy than in mixotrophy. While heterotrophic cells produced bicarbonate and CO2aq, mixotrophy cells produced bicarbonate alone as predominant metabolite. Experiments with singly 13C-labelled acetate (13CH3-COOH or CH3-13COOH) supported that both the 13C nuclei give rise to bicarbonate and CO2aq. The observed metabolite(s) upon further incubation led to the production of starch and triacylglycerol (TAG) in mixotrophy, whereas in heterotrophy the TAG production was minimal with substantial accumulation of glycerol and starch. Prolonged incubation up to eight days, without the addition of fresh acetate, led to an increased TAG production at the expense of bicarbonate, akin to that of nitrogen-starvation. However, such TAG production was substantially high in mixotrophy as compared to that in heterotrophy. Addition of mitochondrial un-coupler blocked the formation of bicarbonate and CO2aq in heterotrophic cells, even though acetate uptake ensued. Addition of PSII-inhibitor to mixotrophic cells resulted in partial conversion of bicarbonate into CO2aq, which were found to be in equilibrium. In an independent experiment, we have monitored assimilation of bicarbonate via photoautotrophy and found that the cells indeed produce starch and TAG at a much faster rate as compared to that in mixotrophy and heterotrophy. Further, we noticed that the accumulation of starch is relatively more as compared to TAG. Based on these observations, we suggest that acetate assimilation in C. reinhardtii does not directly lead to TAG formation but via bicarbonate/CO2aq pathways. Photoautotrophic mode is found to be the best growth condition for the production of starch and TAG and starch in C. reinhardtii. PMID:25207648

  14. 13C solid-state NMR analysis of heterogeneous structure of beeswax in native state

    NASA Astrophysics Data System (ADS)

    Kameda, Tsunenori

    2005-12-01

    I investigated the molecular structure of natural wax from Japanese bees (Apis cerana japonica) in its native state (neither purified nor recrystallized) by 13C and 1H solid-state NMR. Two strong 13C peaks at 32.9 and 34.0 ppm were attributed to signals from internal-chain methylene carbons [int-(CH2)] in two types of crystal form. The peak at 32.9 ppm was assigned to an orthorhombic crystal form, and that at 34.0 ppm was assigned to a triclinic or monoclinic form. In both crystalline regions, bi-exponential decay of 13C spin-lattice relaxation [T1(C)] for the crystalline peaks due to chain diffusion was observed. 1H spin-lattice relaxation [T1(H)] values for protons of the CH3 group and for int-(CH2) in the crystalline and amorphous regions were identical; this was interpreted as being due to averaging of the T1(H) relaxation rates via spin diffusion. In contrast, although the T_{{1}_{\\rho}}(H) decay curves for protons of the CH3 group and for int-(CH2) in the amorphous and orthorhombic forms were almost identical, those of the triclinic or monoclinic forms were different. This unhomogeneous character of T_{{1}_{\\rho}}(H) was interpreted as resulting from differences in the molecular composition of each crystal form. Moreover, two components with long and short 1H spin-spin relaxation [T2(H)] values, arising from the mobile and rigid phases, respectively, were observed at above about -30 °C.

  15. Biosynthesis of aromatic compounds: 13C NMR spectroscopy of whole Escherichia coli cells.

    PubMed Central

    Ogino, T; Garner, C; Markley, J L; Herrmann, K M

    1982-01-01

    13C and 31P NMR spectra of wild-type Escherichia coli showed resonances from metabolic intermediates of glycolysis and ATP formation but no detectable signals from aromatic amino acids. However, tyrosine biosynthesis from D-[l-13C]glucose was observed in cells harboring a feedback-resistant allele of aroF, the gene encoding tyrosine-sensitive 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase [7-phospho-2-keto-3-deoxy-D-arabino-heptonate D-erythrose-4-phosphate-lyase (pyruvate-phosphorylating), EC4.1.2.15], one of the isoenzymes that control carbon flow through the common aromatic biosynthetic pathway. A similar accumulation of tyrosine and phenylalanine is seen in cells carrying a multiple-copy plasmid that carries a wild-type aroF allele in addition to pheA and tyrA, the structural genes for controlling enzymes of the terminal pathways to phenylalanine and tyrosine biosynthesis. These in vivo measurements by a noninvasive probe suggest feedback inhibition as the quantitatively major mechanism controlling carbon flow in the common aromatic compound biosynthetic pathway. In strains accumulating aromatic amino acids, a transient accumulation of trehalose was detected, indicating that previously unknown changes in Escherichia coli metabolism accompany overproduction of aromatic compounds. PMID:6136965

  16. Preparation of partially 2H/13C-labelled RNA for NMR studies. Stereo-specific deuteration of the H5?? in nucleotides

    PubMed Central

    Cromsigt, Jenny; Schleucher, Jürgen; Gustafsson, Tomas; Kihlberg, Jan; Wijmenga, Sybren

    2002-01-01

    An effective in vitro enzymatic synthesis is described for the production of nucleoside triphosphates (NTPs) which are stereo-specifically deuterated on the H5?? position with high selectivity (>98%), and which can have a variety of different labels (13C, 15N, 2H) in other positions. The NTPs can subsequently be employed in the enzymatic synthesis of RNAs using T7 polymerase from a DNA template. The stereo-specific deuteration of the H5?? immediately provides the stereo-specific assignment of H5? resonances in NMR spectra, giving access to important structural parameters. Stereo-chemical H-exchange was used to convert commercially available 1,2,3,4,5,6,6-2H-1,2,3,4,5,6-13C-d-glucose (d7-13C6-d-glucose) into [1,2,3,4,5,6(R)-2H-1,2,3,4,5,6-13C]-d-glucose (d6-13C6-d-glucose). [1?,3?,4?,5??-2H-1?,2?,3?,4?,5?-13C]GTP (d4-13C5-GTP) was then produced from d6-13C6-d-glucose and guanine base via in vitro enzymatic synthesis employing enzymes from the pentose-phosphate, nucleotide biosynthesis and salvage pathways. The overall yield was ?60 mg NTP per 1 g glucose, comparable with the yield of NTPs isolated from Escherichia coli grown on enriched media. The d4-13C5-GTP, together with in vitro synthesised d5-UTP, d5-CTP and non-labelled ATP, were used in the synthesis of a 31 nt RNA derived from the primer binding site of hepatitis B virus genomic RNA. (13C,1H) hetero-nuclear multiple-quantum spectra of the specifically deuterated sample and of a non-deuterated uniformly 13C/15N-labelled sample demonstrates the reduced spectral crowding and line width narrowing compared with 13C-labelled non-deuterated RNA. PMID:11917025

  17. Cigarette Butt Decomposition and Associated Chemical Changes Assessed by 13C CPMAS NMR

    PubMed Central

    Bonanomi, Giuliano; Incerti, Guido; Cesarano, Gaspare; Gaglione, Salvatore A.; Lanzotti, Virginia

    2015-01-01

    Cigarette butts (CBs) are the most common type of litter on earth, with an estimated 4.5 trillion discarded annually. Apart from being unsightly, CBs pose a serious threat to living organisms and ecosystem health when discarded in the environment because they are toxic to microbes, insects, fish and mammals. In spite of the CB toxic hazard, no studies have addressed the effects of environmental conditions on CB decomposition rate. In this study we investigate the interactive effects of substrate fertility and N transfer dynamics on CB decomposition rate and carbon quality changes. We carried out an experiment using smoked CBs and wood sticks, used as a slow decomposing standard organic substrate, incubated in both laboratory and field conditions for two years. CB carbon quality changes during decomposition was assessed by 13C CPMAS NMR. Our experiment confirmed the low degradation rate of CBs which, on average, lost only 37.8% of their initial mass after two years of decomposition. Although a net N transfer occurred from soil to CBs, contrary to our hypothesis, mass loss in the medium-term (two years) was unaffected by N availability in the surrounding substrate. The opposite held for wood sticks, in agreement with the model that N-rich substrates promote the decomposition of other N-poor natural organic materials with a high C/N ratio. As regards CB chemical quality, after two years of decomposition 13C NMR spectroscopy highlighted very small changes in C quality that are likely to reflect a limited microbial attack. PMID:25625643

  18. Thermal maturity of type II kerogen from the New Albany Shale assessed by 13C CP/MAS NMR.

    PubMed

    Werner-Zwanziger, Ulrike; Lis, Grzegorz; Mastalerz, Maria; Schimmelmann, Arndt

    2005-01-01

    Thermal maturity of oil and gas source rocks is typically quantified in terms of vitrinite reflectance, which is based on optical properties of terrestrial woody remains. This study evaluates 13C CP/MAS NMR parameters in kerogen (i.e., the insoluble fraction of organic matter in sediments and sedimentary rocks) as proxies for thermal maturity in marine-derived source rocks where terrestrially derived vitrinite is often absent or sparse. In a suite of samples from the New Albany Shale (Middle Devonian to the Early Mississippian, Illinois Basin) the abundance of aromatic carbon in kerogen determined by 13C CP/MAS NMR correlates linearly well with vitrinite reflectance. PMID:15589735

  19. 13C CPMAS NMR studies and DFT calculations of triterpene xylosides isolated from Actaea racemosa

    NASA Astrophysics Data System (ADS)

    Jamróz, Marta K.; Paradowska, Katarzyna; Gli?ski, Jan A.; Wawer, Iwona

    2011-05-01

    13C CPMAS NMR spectra of four triterpene glycosides: cimigenol xyloside ( 1), 26-deoxyactein ( 2), cimicifugoside H-1 ( 3) and 24-acethylhydroshengmanol xyloside ( 4) were recorded and analyzed to characterize their solid-state structure. Experimental data were supported by theoretical calculations of NMR shielding constants with the GIAO/6-31G**-su1 approach. A number of methods for the conformational search and a number of functionals for the DFT calculations were applied to ( 1). The best method was proven to be MMFF or MMFFAQ for the conformational search and the PBE1PBE functional for the DFT calculations. Extra calculations simulating C16 dbnd O⋯HOH hydrogen bond yield the isotropic shielding closer to the experimental solid-state value. For all the compounds CP kinetics parameters were calculated using either the I-S or the I-I*-S model. The analysis of CP kinetics data for methyl groups revealed differences in the T2 time constant for two methyl groups (C29 and C30) linked at C4.

  20. Assignment of non-crystalline forms in cellulose I by CP\\/MAS 13C NMR spectroscopy

    Microsoft Academic Search

    Kristina Wickholm; Per Tomas Larsson; Tommy Iversen

    1998-01-01

    Non-crystalline forms of cellulose in birch pulp, cotton linters and Cladophora sp were studied by CP\\/MAS 13C NMR spectroscopy. New assignments were made for the NMR-signals in the lower shift part of the C-4 region (80–86ppm). These signals were assigned to cellulose at accessible fibril surfaces, cellulose at inaccessible fibril surfaces and hemicellulose. Also, further evidence was found for para-crystalline

  1. Heterocyclic compounds used as corrosion inhibitors: correlation between 13C and 1H NMR spectroscopy and inhibition efficiency

    Microsoft Academic Search

    E. m. m Sutter; F Ammeloot; M. J Pouet; C Fiaud; R Couffignal

    1999-01-01

    Among the corrosion inhibitors of copper, four aromatic heterocyclic compounds, their corresponding sodium salts and Cu(I) complexes are studied using 13C NMR and 1H NMR spectroscopies in DMSO d6. With regard to the spectra of the neutral molecules, the spectra of the sodium salts are always shifted upfield. By contrast, the spectra of the copper complexes shift either downfield or

  2. /sup 31/P NMR saturation-transfer and /sup 13/C NMR kinetic studies of glycolytic regulation during anaerobic and aerobic glycolysis

    SciTech Connect

    Campbell-Burk, S.L.; den Hollander, J.A.; Alger, J.R.; Shulman, R.G.

    1987-11-17

    /sup 31/P NMR saturation-transfer techniques have been employed in glucose-gown derepressed yeast to determine unidirectional fluxes in the upper part of the Embden-Meyerhof-Parnas pathway. The experiments were performed during anaerobic and aerobic glycolysis by saturating the ATP/sub ..gamma../ resonances and monitoring changes in the phosphomonoester signals from glucose 6-phosphate and fructose 1,6-bisphosphate. These experiments were supplemented with /sup 13/C NMR measurements of glucose utilization rates and /sup 13/C NMR label distribution studies. Combined with data obtained previously from radioisotope measurement, these /sup 31/P and /sup 13/C NMR kinetic studies allowed estimation of the net glycolytic flow in addition to relative flows through phosphofructokinase (PFK) and Fru-1,6-P/sub 2/ase during anaerobic and aerobic glycolysis. The /sup 31/P NMR saturation-transfer results are consistent with previous results obtained from measurements of metabolite levels, radioisotope data, and /sup 13/C NMR studies, providing additional support for in vivo measurement of the flows during glycolysis.

  3. 13C NMR isotopomer analysis reveals a connection between pyruvate cycling and glucose-stimulated insulin secretion (GSIS)

    Microsoft Academic Search

    Danhong Lu; Hindrik Mulder; Piyu Zhao; Shawn C. Burgess; Mette V. Jensen; Svetlana Kamzolova; Christopher B. Newgard; A. Dean Sherry

    2002-01-01

    Cellular metabolism of glucose is required for stimulation of insulin secretion from pancreatic cells, but the precise metabolic coupling factors involved in this process are not known. In an effort to better understand mechanisms of fuel-mediated insulin secretion, we have adapted 13C NMR and isotopomer methods to measure influx of metabolic fuels into the tricarboxylic acid (TCA) cycle in insulinoma

  4. Refractory organic carbon in C-depleted arable soils, as studied by 13C NMR spectroscopy and carbohydrate analysis

    Microsoft Academic Search

    Rita Kiem; Heike Knicker; Martin Körschens; Ingrid Kögel-Knabner

    2000-01-01

    Soil organic matter (SOM) comprises refractory compounds, to which a turnover time of more than 1000 years has been attributed in SOM models. The goal of this study is to characterize the chemical structure of refractory compounds of organic carbon in arable soils by means of 13C NMR spectroscopy and analysis of carbohydrates. C-depleted soils that are expected to be

  5. Class selection of amino acid metabolites in body fluids using chemical derivatization and their enhanced 13C NMR

    PubMed Central

    Shanaiah, Narasimhamurthy; Desilva, M. Aruni; Nagana Gowda, G. A.; Raftery, Michael A.; Hainline, Bryan E.; Raftery, Daniel

    2007-01-01

    We report a chemical derivatization method that selects a class of metabolites from a complex mixture and enhances their detection by 13C NMR. Acetylation of amines directly in aqueous medium with 1,1?-13C2 acetic anhydride is a simple method that creates a high sensitivity and quantitative label in complex biofluids with minimal sample pretreatment. Detection using either 1D or 2D 13C NMR experiments produces highly resolved spectra with improved sensitivity. Experiments to identify and compare amino acids and related metabolites in normal human urine and serum samples as well as in urine from patients with the inborn errors of metabolism tyrosinemia type II, argininosuccinic aciduria, homocystinuria, and phenylketonuria demonstrate the method. The use of metabolite derivatization and 13C NMR spectroscopy produces data suitable for metabolite profiling analysis of biofluids on a time scale that allows routine use. Extension of this approach to enhance the NMR detection of other classes of metabolites has also been accomplished. The improved detection of low-concentration metabolites shown here creates opportunities to improve the understanding of the biological processes and develop improved disease detection methodologies. PMID:17606902

  6. Cell wall changes in ripening kiwifruit: 13C solid state NMR characterisation of relatively rigid cell wall polymers

    Microsoft Academic Search

    R. H. Newman; R. J. Redgwell

    2002-01-01

    Cell wall material was isolated from the outer pericarp of kiwifruit at harvest and at several ripening stages following a postharvest ethylene treatment. Solid state 13C NMR spectra showed no evidence for changes in the nature of the cellulose crystallites or the polysaccharides adhering to crystallite surfaces even in cell wall material isolated from fruits in which cell wall dissolution

  7. DFT calculations of 1H and 13C NMR chemical shifts in transition metal hydrides.

    PubMed

    del Rosal, I; Maron, L; Poteau, R; Jolibois, F

    2008-08-14

    Transition metal hydrides are of great interest in chemistry because of their reactivity and their potential use as catalysts for hydrogenation. Among other available techniques, structural properties in transition metal (TM) complexes are often probed by NMR spectroscopy. In this paper we will show that it is possible to establish a viable methodological strategy in the context of density functional theory, that allows the determination of 1H NMR chemical shifts of hydride ligands attached to transition metal atoms in mononuclear systems and clusters with good accuracy with respect to experiment. 13C chemical shifts have also been considered in some cases. We have studied mononuclear ruthenium complexes such as Ru(L)(H)(dppm)2 with L = H or Cl, cationic complex [Ru(H)(H2O)(dppm)2]+ and Ru(H)2(dppm)(PPh3)2, in which hydride ligands are characterized by a negative 1H NMR chemical shift. For these complexes all calculations are in relatively good agreement compared to experimental data with errors not exceeding 20% except for the hydrogen atom in Ru(H)2(dppm)(PPh3)2. For this last complex, the relative error increases to 30%, probably owing to the necessity to take into account dynamical effects of phenyl groups. Carbonyl ligands are often encountered in coordination chemistry. Specific issues arise when calculating 1H or 13C NMR chemical shifts in TM carbonyl complexes. Indeed, while errors of 10 to 20% with respect to experiment are often considered good in the framework of density functional theory, this difference in the case of mononuclear carbonyl complexes culminates to 80%: results obtained with all-electron calculations are overall in very satisfactory agreement with experiment, the error in this case does not exceed 11% contrary to effective core potentials (ECPs) calculations which yield errors always larger than 20%. We conclude that for carbonyl groups the use of ECPs is not recommended, although their use could save time for very large systems, for instance in cluster chemistry. The reliance of NMR chemical shielding on dynamical effects, such as intramolecular rearrangements or trigonal twists, is also examined for H2Fe(CO)4, K+[HFe(CO)](-), HMn(CO)5 and HRe(CO)5. The accuracy of the theory is also examined for complexes with two dihydrogen ligands (Tp*RuH(H2)2 and [FeH(H2)(DMPE)2]+) and a ruthenium cluster, [H3Ru4(C6H6)4(CO)]+. It is shown that for all complexes studied in this work, the effect of the ligands on the chemical shielding of hydrogen coordinated to metal is suitably calculated, thus yielding a very good correlation between experimental chemical shifts and theoretical chemical shielding. PMID:18648699

  8. 2-Octyl thiophene based three ring mesogens: solid state (13)C NMR and XRD investigations.

    PubMed

    Veeraprakash, B; Lobo, Nitin P; Narasimhaswamy, T; Mandal, A B

    2015-07-22

    2-Octyl thiophene based three-ring mesogens namely 4-n-alkoxyphenyl 4-(5-n-octyl-2-thienyl)benzoates are synthesized by employing palladium acetate based direct arylation. The alkoxy terminal is varied with even carbons from C2 to C14 and enantiotropic polymesomorphism is noticed for all the homologs. Accordingly, phase sequence consisting of nematic, smectic A, smectic C and smectic B is seen for mesogens with terminal chains C6, C8, C10 and C12 on cooling the isotropic phase. For mesogens with C2, C4, C8 and C10 terminal alkoxy chains, the mesophase assignment from hot-stage optical microscopy and differential scanning calorimetry is further confirmed by variable temperature powder X-ray diffraction measurements. The appearance of smectic B phase is established by noticing sharp and intense peaks in both small-angle and wide-angle regions. For a representative mesogen, i.e. T10, high-resolution solid-state (13)C NMR investigations are carried out in all the phases, viz. nematic, smectic A, smectic C and smectic B phases. The orientational order parameters calculated from (13)C-(1)H dipolar couplings from 2D SAMPI-4 experiments are found to be 0.44, 0.67, 0.73 and 0.79 in nematic, smectic A, smectic C and smectic B mesophases for the center phenyl ring respectively. Remarkably, the thiophene order parameter in all mesophases is found to be higher than that of phenyl rings and is explained by considering the molecular shape, which has a terminal bend. Further, the mesogens are found to be photoemissive in chloroform solution with an emission band at ?410 nm. PMID:26166360

  9. Complete assignments of (1)H and (13)C NMR data for two new sesquiterpenes from Cyperus rotundus L.

    PubMed

    Xu, Yan; Zhang, Hong-Wu; Wan, Xiao-Chun; Zou, Zhong-Mei

    2009-06-01

    Two new sesquiterpenes, epi-guaidiol A (1) and sugebiol (3), together with four known sesquiterpenes, guaidiol A(2), sugetriol triacetate (4), cyperenoic acid (5), and cyperotundone (6) were isolated from the rhizomes of Cyperus rotundus L. Their structures were identified by MS and NMR experiments, and the complete assignments of (1)H and (13)C NMR data for two new sesquiterpenes were obtained by the aid of two-dimensional (2D) NMR techniques, including HSQC, HMBC, (1)H-(1)HCOSY and nuclear overhauser enhancement spectroscopy(NOESY). PMID:19288546

  10. Variable-temperature 13C solid-state NMR study of the molecular structure of honeybee wax and silk.

    PubMed

    Kameda, Tsunenori; Tamada, Yasushi

    2009-01-01

    To elucidate the native-state crystal structure of beeswax from the Japanese bee, Apis cerana japonica, we determined the relationship between temperature and the 13C solid-state nuclear magnetic resonance (NMR) chemical shift of methylene carbon of beeswax, with comparison to n-alkanes and polyethylene in the orthorhombic, monoclinic, or triclinic crystal form. Variable-temperature 13C solid-state NMR observations of n-alkanes and polyethylene revealed that the chemical shifts of methylene carbon in the orthorhombic crystal form increased linearly with increasing temperature, that of the triclinic form decreased, and that of the monoclinic form was unaltered. These relations were compared with results of variable-temperature 13C solid-state NMR observation of beeswax. Results clarified that the two crystal forms comprising the beeswax in the native state are orthorhombic and monoclinic. The variable-temperature 13C solid-state NMR observations were also applied to interpret the differential scanning calorimetry (DSC) curve of beeswax. They were used to clarify the structural changes of beeswax for widely various temperatures. For beeswax secreted by the Japanese bee, the transition from the orthorhombic form to the rotator phase occurred at 36 degrees C, that is from the crystalline to the intermediate state at 45 degrees C. Moreover, the variable-temperature 13C solid-state NMR spectrum of honeybee silk in the native state was observed. Results demonstrated that the secondary structures of honeybee silk proteins in the native state comprised coexisting alpha-helix and beta-sheet conformations and that the amount of alpha-helices was greater. The alpha-helix content of honeybee silk was compared with that of hornet silk produced by Vespa larvae. PMID:19007807

  11. Method for determining molar concentrations of metabolites in complex solutions from two-dimensional 1H-13C NMR spectra.

    PubMed

    Lewis, Ian A; Schommer, Seth C; Hodis, Brendan; Robb, Kate A; Tonelli, Marco; Westler, William M; Sussman, Michael R; Markley, John L

    2007-12-15

    One-dimensional (1D) (1)H nuclear magnetic resonance (NMR) spectroscopy is used extensively for high-throughput analysis of metabolites in biological fluids and tissue extracts. Typically, such spectra are treated as multivariate statistical objects rather than as collections of quantifiable metabolites. We report here a two-dimensional (2D) (1)H-(13)C NMR strategy (fast metabolite quantification, FMQ, by NMR) for identifying and quantifying the approximately 40 most abundant metabolites in biological samples. To validate this technique, we prepared mixtures of synthetic compounds and extracts from Arabidopsis thaliana, Saccharomyces cerevisiae, and Medicago sativa. We show that accurate (technical error 2.7%) molar concentrations can be determined in 12 min using our quantitative 2D (1)H-(13)C NMR strategy. In contrast, traditional 1D (1)H NMR analysis resulted in 16.2% technical error under nearly ideal conditions. We propose FMQ by NMR as a practical alternative to 1D (1)H NMR for metabolomics studies in which 50-mg (extract dry weight) samples can be obtained. PMID:17985927

  12. An efficient NMR method for the characterisation of 14N sites through indirect 13C detection

    PubMed Central

    Jarvis, James A.; Haies, Ibraheem M.

    2013-01-01

    Nitrogen is one of the most abundant elements and plays a key role in the chemistry of biological systems. Despite its widespread distribution, the study of the naturally occurring isotope of nitrogen, 14N (99.6%), has been relatively limited as it is a spin-1 nucleus that typically exhibits a large quadrupolar interaction. Accordingly, most studies of nitrogen sites in biomolecules have been performed on samples enriched with 15N, limiting the application of NMR to samples which can be isotopically enriched. This precludes the analysis of naturally occurring samples and results in the loss of the wealth of structural and dynamic information that the quadrupolar interaction can provide. Recently, several experimental approaches have been developed to characterize 14N sites through their interaction with neighboring ‘spy’ nuclei. Here we describe a novel version of these experiments whereby coherence between the 14N site and the spy nucleus is mediated by the application of a moderate rf field to the 14N. The resulting 13C/14N spectra show good sensitivity on natural abundance and labeled materials; whilst the 14N lineshapes permit the quantitative analysis of the quadrupolar interaction. PMID:23589073

  13. An efficient NMR method for the characterisation of 14N sites through indirect 13C detection.

    PubMed

    Jarvis, James A; Haies, Ibraheem M; Williamson, Philip T F; Carravetta, Marina

    2013-05-28

    Nitrogen is one of the most abundant elements and plays a key role in the chemistry of biological systems. Despite its widespread distribution, the study of the naturally occurring isotope of nitrogen, (14)N (99.6%), has been relatively limited as it is a spin-1 nucleus that typically exhibits a large quadrupolar interaction. Accordingly, most studies of nitrogen sites in biomolecules have been performed on samples enriched with (15)N, limiting the application of NMR to samples which can be isotopically enriched. This precludes the analysis of naturally occurring samples and results in the loss of the wealth of structural and dynamic information that the quadrupolar interaction can provide. Recently, several experimental approaches have been developed to characterize (14)N sites through their interaction with neighboring 'spy' nuclei. Here we describe a novel version of these experiments whereby coherence between the (14)N site and the spy nucleus is mediated by the application of a moderate rf field to the (14)N. The resulting (13)C/(14)N spectra show good sensitivity on natural abundance and labeled materials; whilst the (14)N lineshapes permit the quantitative analysis of the quadrupolar interaction. PMID:23589073

  14. Spectral-Density Mapping of 13C ?- 1H ?Vector Dynamics Using Dipolar Relaxation Rates Measured at Several Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Jarvet, Jüri; Allard, Peter; Ehrenberg, Anders; Gräslund, Astrid

    The spectral-density mapping of a 13C ?- 1H ?vector of Leu 10in the 22-residue peptide hormone motilin [P. Allard, J. Jarvet, A. Ehrenberg, and A. Gräslund, J. Biomol. NMR5,133-146 (1995)] is extended in this paper to three polarizing fields 9.4, 11.7, and 14.1 T in order to improve the accuracy of the calculated spectral-density function J(?) and to extend the sampling range up to 750 MHz. The problem with a usually large relative error in J(? H) is eliminated since the generally more precise J(? H- ? C) and J(? H+ ? C) determined at other fields appear at nearly the same frequencies. The fitting of dynamic models to the points of spectral density was made with error weighting, and the influence of J(? H) was found to be negligible. Therefore, the high-frequency part of the spectral-density function is determined essentially without influence from the two transverse-type relaxation rates. In the case of a carbon-proton vector, the relaxation is mainly determined by dipolar interaction and is only weakly influenced by other relaxation mechanisms, which makes it particularly suitable for the spectral-density mapping technique. The measured relaxation rates in the time domain are transformed into the frequency domain by spectral-density mapping, and the slopes in different frequency regions are important parameters when comparing experimental data with theoretical models of motion. Using an adjustable internuclear distance reff, combined with the model-free approach, it is possible to obtain a reasonable fit to measured spectral-density points at J(0) and around J(? C). At the same time, however, the high-frequency slope of the spectral-density function defined by J(? H- ? C) and J(? H+ ? C) could not be reproduced.

  15. DFT study of molecular structures and 13C NMR parameters of two fluorinated biphenyls and their ?6-tricarbonylchromium complexes

    NASA Astrophysics Data System (ADS)

    Gryff-Keller, Adam; Szczeci?ski, Przemys?aw

    2015-07-01

    The molecular structures of 2,2?-difluoro-6,6?-dimethylbiphenyl, 4,5-difluoro-9,10-dihydrophenanthrene and of their ?6-tricarbonylchromium complexes have been discussed in the light of the results of molecular energy calculations. Also the isotropic magnetic shielding constants and carbon-fluorine spin-spin coupling constants for these objects have been calculated and compared with the experimental values of 13C NMR chemical shifts and J constants. The calculational methods used were: DFT/BHandH/6-311++G(2d,p) and/or DFT/B3LYP/6-311++G(2d,p). It has been confirmed that experimental 13C NMR chemical shifts for ?6-arene tricarbonylchromium complexes can be satisfactorily predicted using both methods, although the method exploiting BHandH functional is not able to reproduce the 13C NMR chemical shifts of Cr(CO)3 carbon atoms. On the other hand, this method provides the J(13C, 19F) values which are close to the experimental ones.

  16. Prediction of protein 13C ? NMR chemical shifts using a combination scheme of statistical modeling and quantum-mechanical analysis

    NASA Astrophysics Data System (ADS)

    Liu, Xiuhong; Ren, Yanrong; Zhou, Peng; Shang, Zhicai

    2011-05-01

    Quantitative structure-property relationships (QSPRs) on the basis of constitutional, topological, geometrical, and electrostatic descriptors are developed for 2454 13C ? NMR chemical shifts of 21 structure-known, high-quality monomeric proteins. In this procedure, heuristic approach is employed to perform variable-selection for obtaining few independent and significant descriptors. Coupled with various machine learning methods, including MLR, PLS, LSSVM, RF, and GP, these selected variables are then used to create both linear and nonlinear statistical models with the experimentally determined 13C ? NMR chemical shifts of proteins. In addition, the secondary structural effect and environmental influence on protein chemical shifts are also investigated in detail through structural survey and quantum-mechanical calculations. We demonstrate that (i) relationship between 13C ? NMR chemical shifts and local structural features is, to some extent, nonlinear, and (ii) the 13C ? chemical shift values are not only determined by corresponding side-chain conformations, but also affected from the arrangement and configuration of spatially vicinal residues.

  17. 13C NMR and isotopic (?13C) investigations on modern vegetation samples: a tool to understand the soil organic matter degradation dynamics and preferences

    NASA Astrophysics Data System (ADS)

    Rakshit, Subhadeep; Sanyal, Prasanta; Vardhan Gaur, Harsh

    2015-04-01

    Soil organic carbon, one of the largest reservoirs of carbon, is a heterogeneous mixture of organic compounds with dominant contribution derived from decomposition of plants in various stages. Although general ideas about the processes and mechanisms of soil organic matter (SOM) degradation have been developed, a very few study has linked the SOM with its parent material. In this study we aim to generate reference data set of functional groups from modern vegetation samples (C3 and C4plants) to better understand the degradation dynamics and preferences. The carbon functional groups from modern vegetation samples (eight C3 and nine C4 plants collected from Mohanpur, Nadia, West Bengal, India) were examined by solid state 13C CPMAS NMR spectroscopy. Additionally, isotopic investigations (?13C) has also been carried out on the modern vegetation samples to understand the relationship of bulk isotopic values to the concentration of functional groups. The major functional groups (alkyl C, O-alkyl C, aromatic C, carbonyl C and aldehyde/ketone) of modern vegetation samples form 16%, 65%, 5%, 14% and 1% respectively in C3 plants. Considerable differences has been observed for C4 plants with average values of alkyl C, O-alkyl C, aromatic C, carbonyl C and aldehyde/ketone are 8%, 83%, 3%, 5% and 1% respectively. The concentration of functional groups from the modern vegetational samples can be considered as reference scale to compare with the 13C NMR data derived from the different soil horizons to understand the SOM degradation dynamics. The ?13CV PDB values of modern vegetation samples plotted against the individual concentration of functional groups shows significant correlation in C4 plants, whereas a lack in correlation has been observed for C3 plants. We assume this difference in relationship of ?13CV PDB values with functional groups of C3 and C4plants can be due to the differences in photosynthesis pathways, the fractionation of CO2 and accumulation of the products during various stages of photosynthesis. A more detailed investigation is warranted to understand the governing mechanism behind this observation.

  18. Thermal maturity of type II kerogen from the New Albany Shale assessed by13C CP/MAS NMR

    USGS Publications Warehouse

    Werner-Zwanziger, U.; Lis, G.; Mastalerz, Maria; Schimmelmann, A.

    2005-01-01

    Thermal maturity of oil and gas source rocks is typically quantified in terms of vitrinite reflectance, which is based on optical properties of terrestrial woody remains. This study evaluates 13C CP/MAS NMR parameters in kerogen (i.e., the insoluble fraction of organic matter in sediments and sedimentary rocks) as proxies for thermal maturity in marine-derived source rocks where terrestrially derived vitrinite is often absent or sparse. In a suite of samples from the New Albany Shale (Middle Devonian to the Early Mississippian, Illinois Basin) the abundance of aromatic carbon in kerogen determined by 13C CP/MAS NMR correlates linearly well with vitrinite reflectance. ?? 2004 Elsevier Inc. All rights reserved.

  19. 13C-direct detected NMR experiments for the sequential J-based resonance assignment of RNA oligonucleotides

    PubMed Central

    Richter, Christian; Kovacs, Helena; Buck, Janina; Wacker, Anna; Fürtig, Boris; Bermel, Wolfgang

    2010-01-01

    We present here a set of 13C-direct detected NMR experiments to facilitate the resonance assignment of RNA oligonucleotides. Three experiments have been developed: (1) the (H)CC-TOCSY-experiment utilizing a virtual decoupling scheme to assign the intraresidual ribose 13C-spins, (2) the (H)CPC-experiment that correlates each phosphorus with the C4? nuclei of adjacent nucleotides via J(C,P) couplings and (3) the (H)CPC-CCH-TOCSY-experiment that correlates the phosphorus nuclei with the respective C1?,H1? ribose signals. The experiments were applied to two RNA hairpin structures. The current set of 13C-direct detected experiments allows direct and unambiguous assignment of the majority of the hetero nuclei and the identification of the individual ribose moieties following their sequential assignment. Thus, 13C-direct detected NMR methods constitute useful complements to the conventional 1H-detected approach for the resonance assignment of oligonucleotides that is often hindered by the limited chemical shift dispersion. The developed methods can also be applied to large deuterated RNAs. Electronic supplementary material The online version of this article (doi:10.1007/s10858-010-9429-5) contains supplementary material, which is available to authorized users. PMID:20544375

  20. High-field 13C NMR spectroscopy of tissue in Vivo. A double-resonance surface-coil probe

    NASA Astrophysics Data System (ADS)

    Reo, Nicholas V.; Ewy, Coleen S.; Siegfried, Barry A.; Ackerman, Joseph J. H.

    A double-resonance surface-coil NMR probe is described for performance of high-field (8.5 T) proton decoupled carbon-13 experiments with tissue in vivo. The probe may be accommodated in standard, 89 mm i.d. clear bore, commercial spectrometers and is suitable for studies utilizing small laboratory animals such as mice, hamsters, and rats. A coaxial coil design is employed (10 mm diameter 13C coil, 20 mm diameter 1H coil) which provides ca. 40 dB attenuation between the 13C observe and 1H decouple channels. The inherent efficiency of the surface-coil configuration provides a sensitivity comparable to a commercial probe of the same nominal dimension (10 mm Helmholtz coil) and assures adequate decoupling in conductive samples with ca. 3-5 W power. In the absence of 13C isotopic enrichment, NMR spectra of rat leg, liver, and brain in vivo provide signalto-noise sufficient for 10 min time resolution. Administration of 100 mg of 90% 13C-labeled glucose into a peripheral vein of a ca. 300 g rat resulted in a liver glucose resonance which could be monitored with good signal-to-noise and 3 min time resolution.

  1. Aspects of the chemical structure of soil organic materials as revealed by solid-state13C NMR spectroscopy

    Microsoft Academic Search

    J. A. Baldock; J. M. Oades; A. G. Waters; X. Peng; A. M. Vassallo; M. A. Wilson

    1992-01-01

    Solid-state cross-polarisation\\/magic-angle-spinning3C nuclear magnetic resonance (CP\\/MAS13C NMR) spectroscopy was used to characterise semi-quantitatively the organic materials contained in particle size and density fractions isolated from five different mineral soils: two Mollisols, two Oxisols and an Andosol. The acquired spectra were analysed to determine the relative proportion of carboxyl, aromatic, O-alkyl and alkyl carbon contained in each fraction. Although similar types

  2. 1H, 13C MAS NMR and GIAO-CPHF calculations of chloramphenicol, thiamphenicol and their pyrrole analogues

    NASA Astrophysics Data System (ADS)

    ?o?ek, Teresa; Paradowska, Katarzyna; Krajewska, Dorota; Ró?a?ski, Andrzej; Wawer, Iwona

    2003-02-01

    The 13C CP MAS and 1H MAS NMR and ab initio (GIAO-CPHF) calculations were used to obtain structural information on two known antibiotics: chloramphenicol, and thiamphenicol, and two new analogues: DL- threo-1-(1-methyl-4-nitro-pyrrole-2-yl)-2-dichloroacetamidopropane-1,3-diol and DL- threo-1-(1-methylsulfonylpyrrole-3-yl)-2-dichloroacetamidopropane-1,3-diol.

  3. 13C and 15N N.M.R. in thorium carbides and carbonitrides J. L. Boutard (*),

    E-print Network

    Paris-Sud XI, Université de

    845 13C and 15N N.M.R. in thorium carbides and carbonitrides J. L. Boutard (*), SFMA, DECPu, Centre-réseau et les dépla- cements de fréquence mesurés contiennent de fortes contributions orbitales solid solution ThC1 -xNx. The carbide ThCy can be made non-stoichiometric with 0.70 S y S 0.98. The elec

  4. 15N- and 13C-labeled media from Anabaena sp. for universal isotopic labeling of bacteriocins: NMR resonance assignments of leucocin A from Leuconostoc gelidum and nisin A from Lactococcus lactis.

    PubMed

    Sailer, M; Helms, G L; Henkel, T; Niemczura, W P; Stiles, M E; Vederas, J C

    1993-01-12

    A procedure for universal 13C and/or 15N labeling of microbial peptides which are produced by fermentation in complex media and its application to two food-preserving bacteriocins from lactic acid bacteria are described. Isotopic enrichment of nisin A (from Lactococcus lactis) and of leucocin A (from Leuconostoc gelidum) is readily achieved using a soluble peptone derived from enzymatic hydrolysis (pepsin and chymopapain) of Anabaena sp. ATCC 27899 cells grown on sodium [13C]bicarbonate and/or sodium [15N]nitrate as sole carbon and nitrogen sources. Combustion of this peptone followed by mass spectrometric analysis indicates that 45% of the labeled carbon and 65% of the labeled nitrogen added to the Anabaena culture are utilized in the amino acids of the peptone and that the isotopic purity for both 13C and 15N remains essentially unchanged provided that the cells are grown under argon atmosphere to avoid nitrogen fixation. NMR analyses of [13C,15N]nisin A using H[13C]MQC, H[13C]MBC, 2D INADEQUATE, and H[15N]MQC techniques confirmed 1H spectral assignments previously reported for unlabeled material and readily provided carbon and nitrogen assignments. The results show that universal but not uniform 13C labeling occurs unless the nutrient source is completely isotopically enriched at high level (> or = 98%) because of differential levels of de novo amino acid synthesis. Application of NMR techniques such as TOCSY, DQF-COSY, NOESY, and H[13C]MQC to unlabeled and [13C]leucocin A afforded the complete 1H and 13C assignment. Leucocin A does not possess clearly defined conformational structure in DMSO or aqueous solutions. PMID:8418850

  5. Unified and isomer-specific NMR metabolomics database for the accurate analysis of (13)C-(1)H HSQC spectra.

    PubMed

    Bingol, Kerem; Li, Da-Wei; Bruschweiler-Li, Lei; Cabrera, Oscar A; Megraw, Timothy; Zhang, Fengli; Brüschweiler, Rafael

    2015-02-20

    A new metabolomics database and query algorithm for the analysis of (13)C-(1)H HSQC spectra is introduced, which unifies NMR spectroscopic information on 555 metabolites from both the Biological Magnetic Resonance Data Bank (BMRB) and Human Metabolome Database (HMDB). The new database, termed Complex Mixture Analysis by NMR (COLMAR) (13)C-(1)H HSQC database, can be queried via an interactive, easy to use web interface at http://spin.ccic.ohio-state.edu/index.php/hsqc/index . Our new HSQC database separately treats slowly exchanging isomers that belong to the same metabolite, which permits improved query in cases where lowly populated isomers are below the HSQC detection limit. The performance of our new database and query web server compares favorably with the one of existing web servers, especially for spectra of samples of high complexity, including metabolite mixtures from the model organisms Drosophila melanogaster and Escherichia coli. For such samples, our web server has on average a 37% higher accuracy (true positive rate) and a 82% lower false positive rate, which makes it a useful tool for the rapid and accurate identification of metabolites from (13)C-(1)H HSQC spectra at natural abundance. This information can be combined and validated with NMR data from 2D TOCSY-type spectra that provide connectivity information not present in HSQC spectra. PMID:25333826

  6. Use of {sup 13}C NMR to assess the biodegradation of 1-{sup 13}C-labeled acenaphthene in the presence of creosote polynuclear hydrocarbons (PAHs) and naphthalene by mixed bacterial cultures

    SciTech Connect

    Selifonov, S.A. [Univ. of Minnesota, St. Paul, MN (United States); Bortiatynski, J.M.; Nanny, M.A.; Hatcher, P.G. [Pennsylvania State Univ., University Park, PA (United States)

    1996-10-01

    1-{sup 13}C-acenaphthene mixed with creosote PAH`s or naphthalene was incubated with bacterial strains known to degrade naphthalene, phenanthrene and acenaphthene. After incubation, the reaction mixtures were extracted with organic solvent, and the biodegradation products were identified by {sup 13}C NMR. An accumulation of intermediate degradation products was identified and attributed to the non-specific action of naphthalene catabolic pathways of the mixed bacterial cultures. An acenaphthene degrading strain, Pseudomonas sp. strain A2279 was added to the nixed bacterial cultures to minimize the formation of the observed dead-end products. The {sup 13}C NMR spectra obtained from the experiments in which strain A2279 was present clearly showed the complete biodegradation of 1-{sup 13}C-acenaphthene without the accumulation of {sup 13}C-labeled products. This set of experiments clearly demonstrates the utility of {sup 13}C NMR as an effective tool for the assessment of the biodegradation of PAH`s such as 1-{sup 13}C-acenaphthene by various microbial strains.

  7. Local structure and molecular motions in imidazolium hydrogen malonate crystal as studied by 2H and 13C NMR

    NASA Astrophysics Data System (ADS)

    Mizuno, M.; Chizuwa, M.; Umiyama, T.; Kumagai, Y.; Miyatou, T.; Ohashi, R.; Ida, T.; Tansho, M.; Shimizu, T.

    2015-04-01

    The local structure and molecular motion of the imidazolium hydrogen malonate crystal were investigated using solid-state 2H and 13C NMR. The imidazolium ion undergoes isotropic rotation, which is correlated with a defect in the crystal, as observed by 2H NMR broadline spectra above 263 K. A 180? flip of the imidazolium ion in the regular site was observed from 2H NMR quadrupole Carr-Purcell-Meiboom-Gill (QCPMG) spectra. The Grotthuss mechanism was accompanied by a 180? flip of the imidazolium ion in regular sites. Moreover, the proton transfer associated with the imidazolium ion of the defective crystal is important for proton conductivity of the imidazolium hydrogen malonate crystal.

  8. Practical aspects of high-sensitivity multidimensional 13C MAS NMR spectroscopy of perdeuterated proteins

    NASA Astrophysics Data System (ADS)

    Akbey, Ümit; van Rossum, Barth-Jan; Oschkinat, Hartmut

    2012-04-01

    The double nucleus enhanced recoupling (DONER) experiment employs simultaneous irradiation of protons and deuterons to promote spin diffusion processes in a perdeuterated protein. This results in 4-5 times higher sensitivity in 2D 13C-13C correlation experiments as compared to PDSD [1]. Here, a quantitative comparison of PDSD, 1H-DARR, 2H-DARR, and 1H + 2H DONER has been performed to analyze the influence of spin diffusion on polarization transfer processes. Cross peak buildup curves were analyzed to obtain guidelines for choosing the best experimental parameters. The largest cross peak intensities were observed for the DONER experiments. The fastest build-up rate was observed in the 2H-DARR experiment within a buildup range of ˜18-45 ms, whereas values between 24 and 69 ms are observed for the DONER experiment. Furthermore, the effects of direct excitation and cross polarization (CP) are compared. A comparison between DONER and RFDR experiments reveal ˜50% more intense cross peaks in the C?-CO and C?-Calip regions of the 2D 13C-13C DONER spectrum applying proton CP (1H-13C). As a parameter determining the S/N in 13C-13C correlation experiments, proton CP efficiency is investigated using deuterated samples with proton/deuterium ratios at 20%, 40%, and 100% H2O. Sufficiently strong 13C CPMAS signal intensity is observed for such proteins even with very low proton concentration. The effect of proton and/or deuterium decoupling is analyzed at various MAS spinning frequencies. Deuterium decoupling was found most crucial for obtaining high resolution. Long range correlations are readily observed representing distances up to ˜6 Å by using DONER approach.

  9. Uranyl nitrate inhibits lactate gluconeogenesis in isolated human and mouse renal proximal tubules: A {sup 13}C-NMR study

    SciTech Connect

    Renault, Sophie; Faiz, Hassan; Gadet, Rudy; Ferrier, Bernard; Martin, Guy; Baverel, Gabriel [Metabolomique et Maladies Metaboliques, Institut National de la Sante et de la recherche Medicale, Unit 820, Faculte de Medecine R.T.H. Laennec, Universite de Lyon, 7-11 rue G. Paradin, 69372 Lyon Cedex 08 (France); Conjard-Duplany, Agnes, E-mail: agnes.duplany@recherche.univ-lyon1.f [Metabolomique et Maladies Metaboliques, Institut National de la Sante et de la recherche Medicale, Unit 820, Faculte de Medecine R.T.H. Laennec, Universite de Lyon, 7-11 rue G. Paradin, 69372 Lyon Cedex 08 (France)

    2010-01-01

    As part of a study on uranium nephrotoxicity, we investigated the effect of uranyl nitrate in isolated human and mouse kidney cortex tubules metabolizing the physiological substrate lactate. In the millimolar range, uranyl nitrate reduced lactate removal and gluconeogenesis and the cellular ATP level in a dose-dependent fashion. After incubation in phosphate-free Krebs-Henseleit medium with 5 mM L-[1-{sup 13}C]-, or L-[2-{sup 13}C]-, or L-[3-{sup 13}C]lactate, substrate utilization and product formation were measured by enzymatic and NMR spectroscopic methods. In the presence of 3 mM uranyl nitrate, glucose production and the intracellular ATP content were significantly reduced in both human and mouse tubules. Combination of enzymatic and NMR measurements with a mathematical model of lactate metabolism revealed an inhibition of fluxes through lactate dehydrogenase and the gluconeogenic enzymes in the presence of 3 mM uranyl nitrate; in human and mouse tubules, fluxes were lowered by 20% and 14% (lactate dehydrogenase), 27% and 32% (pyruvate carboxylase), 35% and 36% (phosphoenolpyruvate carboxykinase), and 39% and 45% (glucose-6-phosphatase), respectively. These results indicate that natural uranium is an inhibitor of renal lactate gluconeogenesis in both humans and mice.

  10. Synthetic, Infrared, 1H and 13C NMR Spectral Studies on N-(2-/3-Substituted Phenyl)-4-Substituted Benzenesulphonamides, 4-X'C6H4SO2NH(2-/3-XC6H4), where X' = H, CH3, C2H5, F, Cl or Br, and X = CH3 or Cl

    NASA Astrophysics Data System (ADS)

    Gowda, B. Thimme; Shetty, Mahesha; Jayalakshmi, K. L.

    2005-02-01

    Twenty three N-(2-/3-substituted phenyl)-4-substituted benzenesulphonamides of the general formula, 4-X'C6H4SO2NH(2-/3-XC6H4), where X' = H, CH3, C2H5, F, Cl or Br and X = CH3 or Cl have been prepared and characterized, and their infrared spectra in the solid state, 1H and 13C NMR spectra in solution were studied. The N-H stretching vibrations, ?N-H, absorb in the range 3285 - 3199 cm-1, while the asymmetric and symmetric SO2 vibrations vary in the ranges 1376 - 1309 cm-1 and 1177 - 1148 cm-1, respectively. The S-N and C-N stretching vibrations absorb in the ranges 945 - 893 cm-1 and 1304 - 1168 cm-1, respectively. The compounds do not exhibit particular trends in the variation of these frequencies on substitution either at ortho or meta positions with either a methyl group or Cl. The observed 1H and 13C chemical shifts of are assigned to protons and carbons of the two benzene rings. Incremental shifts of the ring protons and carbons due to -SO2NH(2-/3-XC6H4) groups in C6H5SO2NH(2-/3-XC6H4), and 4- X'C6H4SO2- and 4-X'C6H4SO2NH- groups in 4-X'C6H4SO2NH(C6H5) are computed and employed to calculate the chemical shifts of the ring protons and carbons in the substituted compounds, 4-X'C6H4SO2NH(2-/3-XC6H4). The computed values agree well with the observed chemical shifts.

  11. Noninvasive measurements of glycogen in perfused mouse livers using chemical exchange saturation transfer NMR and comparison to (13)c NMR spectroscopy.

    PubMed

    Miller, Corin O; Cao, Jin; Chekmenev, Eduard Y; Damon, Bruce M; Cherrington, Alan D; Gore, John C

    2015-06-01

    Liver glycogen represents an important physiological form of energy storage. It plays a key role in the regulation of blood glucose concentrations, and dysregulations in hepatic glycogen metabolism are linked to many diseases including diabetes and insulin resistance. In this work, we develop, optimize, and validate a noninvasive protocol to measure glycogen levels in isolated perfused mouse livers using chemical exchange saturation transfer (CEST) NMR spectroscopy. Model glycogen solutions were used to determine optimal saturation pulse parameters which were then applied to intact perfused mouse livers of varying glycogen content. Glycogen measurements from serially acquired CEST Z-spectra of livers were compared with measurements from interleaved natural abundance (13)C NMR spectra. Experimental data revealed that CEST-based glycogen measurements were highly correlated with (13)C NMR glycogen spectra. Monte Carlo simulations were then used to investigate the inherent (i.e., signal-to-noise-based) errors in the quantification of glycogen with each technique. This revealed that CEST was intrinsically more precise than (13)C NMR, although in practice may be prone to other errors induced by variations in experimental conditions. We also observed that the CEST signal from glycogen in liver was significantly less than that observed from identical amounts in solution. Our results demonstrate that CEST provides an accurate, precise, and readily accessible method to noninvasively measure liver glycogen levels and their changes. Furthermore, this technique can be used to map glycogen distributions via conventional proton magnetic resonance imaging, a capability universally available on clinical and preclinical magnetic resonance imaging (MRI) scanners vs (13)C detection, which is limited to a small fraction of clinical-scale MRI scanners. PMID:25946616

  12. Preservation of proteinaceous material during the degradation of the green alga Botryococcus braunii: A solid-state 2D 15N 13C NMR spectroscopy study

    Microsoft Academic Search

    Xu Zang; Reno T. Nguyen; H. Rodger Harvey; Heike Knicker; Patrick G. Hatcher

    2001-01-01

    Using solid-state cross-polarization-magic-angle-spinning (CPMAS) 13C and 15N nuclear magnetic resonance (NMR) and 2-D double cross polarization (DCP) MAS 15N 13C NMR techniques, microbially degraded Botryococcus braunii was analyzed to study the chemical nature of organic nitrogen in the algal residue. The amide linkage, as found in protein, was observed as the major nitrogen component in 201-day-old degraded algae. No significant

  13. Poly(methyl acrylate- co-sodium methacrylate) ionomer studied by solid state 13C T1? NMR

    NASA Astrophysics Data System (ADS)

    Lim, A. R.; Kim, J.-S.

    2000-06-01

    The poly(methyl acrylate) (PMA) and poly(methyl acrylate- co-sodium methacrylate) containing 6.9 mol% of ionic groups (PMANa-6.9) were studied by 13C CP/MAS NMR. The 13C spin-lattice relaxation times in a rotating frame, T1?, have been measured as a function of temperature. Using these T1? spin-lattice relaxation times, we discuss the mobility, the correlation time, and activation energy for the PMA and PMANa-6.9, respectively. The molecular motion in the PMANa-6.9 needs higher activation energies than in PMA. It is worth noting that the motion of the 1-methyl carbons in the PMANa-6.9 ionomer distinctly differs from that in the PMA homopolymer. The slow side of the T1? minimum associated with the 1-methyl carbons is ascribed to stronger interactions between the polymer chains in the ionomer than in the homopolymer.

  14. 1H MAS, 13C CP/MAS, and 2H NMR spectra studies of piperidinium ph{p}-chlorobenzoate

    NASA Astrophysics Data System (ADS)

    Nakano, Ryo; Honda, Hisashi; Ishimaru, Shin'ichi; Noro, Sumiko

    2013-05-01

    Anomalous H/D isotope effects were detected in the 1H MAS NMR spectra of piperidinium p-chlorobenzoate (C5H10NH2{+}\\cdot ClC6H4COO - ) upon deuterium substitution of hydrogen atoms which form two kinds of N-H⋯O H-bonds in the crystal; in contrast to these spectra, only slight chemical shifts were recorded in 13C CP/MAS NMR spectra. 2H NMR spectrum of the deuterated sample show quadrupole coupling constants of 148 and 108 kHz, and reveal that there are a few motions contributing to the electric-field modulation of the 2H nucleus. The 1H MAS NMR spectra of piperidinium p-chlrobenzoate- d 16 (C5D10ND2{+}\\cdot ClC6D4COO - ) and - d 14 (C5D10NH2{+}\\cdot ClC6D4COO - ) revealed that the change in the envelope is caused by chemical shifts of each signal upon deuteration. Calculations based on the density-functional-theory showed that the N-H distance along the crystallographic a-axis mainly contributes to the anomalous isotope effects on 1H MAS NMR envelopes.

  15. Aspects of the chemical structure of soil organic materials as revealed by solid-state 13 C NMR spectroscopy

    Microsoft Academic Search

    J. A. Baldock; J. M. Oades; A. G. Waters; X. Peng; A. M. Vassallo; M. A. Wilson

    1992-01-01

    Solid-state cross-polarisation\\/magic-angle-spinning3C nuclear magnetic resonance (CP\\/MAS13C NMR) spectroscopy was used to characterise semi-quantitatively the organic materials contained in particle size and density\\u000a fractions isolated from five different mineral soils: two Mollisols, two Oxisols and an Andosol. The acquired spectra were\\u000a analysed to determine the relative proportion of carboxyl, aromatic, O-alkyl and alkyl carbon contained in each fraction.\\u000a Although similar types

  16. Use of solid-state 13C NMR in structural studies of humic acids and humin from Holocene sediments

    USGS Publications Warehouse

    Hatcher, P.G.; VanderHart, D.L.; Earl, W.L.

    1980-01-01

    13C NMR spectra of solid humic substances in Holocene sediments have been obtained using cross polarization with magic-angle sample spinning techniques. The results demonstrate that this technique holds great promise for structural characterizations of complex macromolecular substances such as humin and humic acids. Quantifiable distinctions can be made between structural features of aquatic and terrestrial humic substances. The aliphatic carbons of the humic substances are dominant components suggestive of input from lipid-like materials. An interesting resemblance is also noted between terrestrial humic acid and humin spectra. ?? 1980.

  17. Specific 13C labeling of leucine, valine and isoleucine methyl groups for unambiguous detection of long-range restraints in protein solid-state NMR studies

    NASA Astrophysics Data System (ADS)

    Fasshuber, Hannes Klaus; Demers, Jean-Philippe; Chevelkov, Veniamin; Giller, Karin; Becker, Stefan; Lange, Adam

    2015-03-01

    Here we present an isotopic labeling strategy to easily obtain unambiguous long-range distance restraints in protein solid-state NMR studies. The method is based on the inclusion of two biosynthetic precursors in the bacterial growth medium, ?-ketoisovalerate and ?-ketobutyrate, leading to the production of leucine, valine and isoleucine residues that are exclusively 13C labeled on methyl groups. The resulting spectral simplification facilitates the collection of distance restraints, the verification of carbon chemical shift assignments and the measurement of methyl group dynamics. This approach is demonstrated on the type-three secretion system needle of Shigella flexneri, where 49 methyl-methyl and methyl-nitrogen distance restraints including 10 unambiguous long-range distance restraints could be collected. By combining this labeling scheme with ultra-fast MAS and proton detection, the assignment of methyl proton chemical shifts was achieved.

  18. Specific 13C labeling of leucine, valine and isoleucine methyl groups for unambiguous detection of long-range restraints in protein solid-state NMR studies.

    PubMed

    Fasshuber, Hannes Klaus; Demers, Jean-Philippe; Chevelkov, Veniamin; Giller, Karin; Becker, Stefan; Lange, Adam

    2015-03-01

    Here we present an isotopic labeling strategy to easily obtain unambiguous long-range distance restraints in protein solid-state NMR studies. The method is based on the inclusion of two biosynthetic precursors in the bacterial growth medium, ?-ketoisovalerate and ?-ketobutyrate, leading to the production of leucine, valine and isoleucine residues that are exclusively (13)C labeled on methyl groups. The resulting spectral simplification facilitates the collection of distance restraints, the verification of carbon chemical shift assignments and the measurement of methyl group dynamics. This approach is demonstrated on the type-three secretion system needle of Shigella flexneri, where 49 methyl-methyl and methyl-nitrogen distance restraints including 10 unambiguous long-range distance restraints could be collected. By combining this labeling scheme with ultra-fast MAS and proton detection, the assignment of methyl proton chemical shifts was achieved. PMID:25625825

  19. 13C NMR Metabolomic Evaluation of Immediate and Delayed Mild Hypothermia in Cerebrocortical Slices After Oxygen-Glucose Deprivation

    PubMed Central

    Liu, Jia; Segal, Mark; Kelly, Mark J.S.; Pelton, Jeffrey G.; Kim, Myungwon; James, Thomas L.; Litt, Lawrence

    2013-01-01

    Background Mild brain hypothermia (32°C–34°C) after human neonatal asphyxia improves neurodevelopmental outcomes. Astrocytes but not neurons have pyruvate carboxylase (PC) and an acetate uptake transporter. 13C NMR spectroscopy of rodent brain extracts after administering [1-13C]glucose and [1,2-13C]acetate can distinguish metabolic differences between glia and neurons, and tricarboxylic acid cycle (TCA cycle) entry via pyruvate dehydrogenase (PDH) and PC. Methods Neonatal rat cerebrocortical slices receiving a 13C-acetate/glucose mixture underwent a 45-min asphyxia simulation via oxygen-glucose-deprivation (OGD) followed by 6 h of recovery. Protocols in three groups of N = 3 experiments were identical except for temperature management. The three temperature groups were: normothermia (37°C), hypothermia (32°C for 3.75 h beginning at OGD start), and delayed hypothermia (32°C for 3.75 h, beginning 15 min after OGD start). Multivariate analysis of nuclear magnetic resonance metabolite quantifications included principal component analyses and the L1-Penalized Regularized Regression algorithm known as the Least Absolute Shrinkage and Selection Operator (LASSO). Results The most significant metabolite difference (p < 0.0056) was [2-13C]glutamine’s higher final/control ratio for the Hypothermia group (1.75 ± 0.12) compared to ratios for the Delayed (1.12 ± 0.12) and Normothermia group (0.94 ± 0.06), implying a higher PC/PDH ratio for glutamine formation. LASSO found the most important metabolites associated with adenosine triphosphate preservation: [3,4-13C]glutamate—produced via PDH entry, [2-13C]taurine--an important osmolyte, and phosphocreatine. Final principal component analyses scores plots suggested separate cluster formation for the hypothermia group, but with insufficient data for statistical significance. Conclusions Starting mild hypothermia simultaneously with OGD, compared with delayed starting or no hypothermia, has higher PC throughput, suggesting that better glial integrity is one important neuroprotection mechanism of earlier hypothermia. PMID:23748856

  20. Combined 1H-NMR and 1H-13C HSQC-NMR to improve urinary screening in autism spectrum disorders.

    PubMed

    Nadal-Desbarats, Lydie; Aïdoud, Nacima; Emond, Patrick; Blasco, Hélène; Filipiak, Isabelle; Sarda, Pierre; Bonnet-Brilhault, Frédérique; Mavel, Sylvie; Andres, Christian R

    2014-07-01

    Autism spectrum disorders (ASD) are neurodevelopmental diseases with complex genetic and environmental etiological factors. Although genetic causes play a significant part in the etiology of ASD, metabolic disturbances may also play a causal role or modulate the clinical features of ASD. The number of ASD studies involving metabolomics is increasing, and sometime with conflicting findings. We assessed the metabolomics profiling of urine samples to determine a comprehensive biochemical signature of ASD. Furthermore, to date no study has combined metabolic profiles obtained from different analytical techniques to distinguish patient with ASD from healthy individuals. We obtained (1)H-NMR spectra and 2D (1)H-(13)C HSQC NMR spectra from urine samples of patients with ASD or healthy controls. We analyzed these spectra by multivariate statistical data analysis. The OPLS-DA model obtained from (1)H NMR spectra showed a good discrimination between ASD samples and non-ASD samples (R(2)Y(cum) = 0.70 and Q(2) = 0.51). Combining the (1)H NMR spectra and the 2D (1)H-(13)C HSQC NMR spectra increased the overall quality and predictive value of the OPLS-DA model (R(2)Y(cum) = 0.84 and Q(2) = 0.71), leading to a better sensitivity and specificity. Urinary excretion of succinate, glutamate and 3-methyl-histidine differed significantly between ASD and non-ASD samples. Urinary screening of children with neurodevelopmental disorders by combining NMR spectroscopies (1D and 2D) in multivariate analysis is a better sensitive and a straightforward method that could help the diagnosis ASD. PMID:24841505

  1. PMR and 13 C NMR Spectra of Biologically Active Compounds. XII. Taraxasterol and Its Acetate from the Aerial Part of Onopordum acanthium

    Microsoft Academic Search

    L. M. Khalilov; A. Z. Khalilova; E. R. Shakurova; I. F. Nuriev; V. V. Kachala; A. S. Shashkov; U. M. Dzhemilev

    2003-01-01

    Crystalline taraxasterol and its acetate were isolated for the first time from Onopordum acanthium. Two-dimensional COSY, HSQC, and HMBC NMR experimentswere carried out forcomplete assignment of signals in the PMR and 13C NMR. Chemical shifts of stereochemically important methyl C atoms C-28 and C-29 were measured.

  2. Effect of Oxygen Concentration on Viability and Metabolism in a Fluidized-Bed Bioartificial Liver Using 31P and 13C NMR Spectroscopy

    PubMed Central

    Jeffries, Rex E.; Gamcsik, Michael P.; Keshari, Kayvan R.; Pediaditakis, Peter; Tikunov, Andrey P.; Young, Gregory B.; Lee, Haakil; Watkins, Paul B.

    2013-01-01

    Many oxygen mass-transfer modeling studies have been performed for various bioartificial liver (BAL) encapsulation types; yet, to our knowledge, there is no experimental study that directly and noninvasively measures viability and metabolism as a function of time and oxygen concentration. We report the effect of oxygen concentration on viability and metabolism in a fluidized-bed NMR-compatible BAL using in vivo 31P and 13C NMR spectroscopy, respectively, by monitoring nucleotide triphosphate (NTP) and 13C-labeled nutrient metabolites, respectively. Fluidized-bed bioreactors eliminate the potential channeling that occurs with packed-bed bioreactors and serve as an ideal experimental model for homogeneous oxygen distribution. Hepatocytes were electrostatically encapsulated in alginate (avg. diameter, 500??m; 3.5×107 cells/mL) and perfused at 3?mL/min in a 9-cm (inner diameter) cylindrical glass NMR tube. Four oxygen treatments were tested and validated by an in-line oxygen electrode: (1) 95:5 oxygen:carbon dioxide (carbogen), (2) 75:20:5 nitrogen:oxygen:carbon dioxide, (3) 60:35:5 nitrogen:oxygen:carbon dioxide, and (4) 45:50:5 nitrogen:oxygen:carbon dioxide. With 20% oxygen, ?-NTP steadily decreased until it was no longer detected at 11?h. The 35%, 50%, and 95% oxygen treatments resulted in steady ?-NTP levels throughout the 28-h experimental period. For the 50% and 95% oxygen treatment, a 13C NMR time course (?5?h) revealed 2-13C-glycine and 2-13C-glucose to be incorporated into [2-13C-glycyl]glutathione (GSH) and 2-13C-lactate, respectively, with 95% having a lower rate of lactate formation. 31P and 13C NMR spectroscopy is a noninvasive method for determining viability and metabolic rates. Modifying tissue-engineered devices to be NMR compatible is a relatively easy and inexpensive process depending on the bioreactor shape. PMID:22835003

  3. Modified Spectral Editing Methods for 13C CP/MAS Experiments in Solids

    NASA Astrophysics Data System (ADS)

    Hu, Jian Zhi; Harper, James K.; Taylor, Craig; Pugmire, Ronald J.; Grant, David M.

    2000-02-01

    The spectral editing approach of Zilm and coworkers utilizes polarization, polarization inversion, and spin depolarization methods for enhancing or suppressing NMR spectral lines in solids. The proposed pulse sequences allow nonprotonated C, CH, CH 2, and CH 3 types of carbon resonances to be separated from one another and identified accordingly. The former method tentatively separates the nonprotonated C and CH 3 peaks with a cutoff shift of 35 ppm. This shift is a reasonable demarcation shift for a preponderance of organic molecules, but exceptions do exist that could constitute a serious drawback in a few instances. The new approach separates the nonprotonated C and CH 3 carbon peaks unequivocally using modified pulse sequences similar to those of Zilm. Further, both the CH only and CH 2 only spectra, respectively, can be acquired directly from combining so called (+) and (-) sequences using different spectral delay periods and pulse parameters. The (+) and the (-) pulse sequences produce signals for the nonprotonated and methyl carbons that have essentially the same amplitude but opposite phases. These spectra, combined with the previously reported CH 3 and nonprontonated C only spectra, offer a complete spectral editing technique for solid samples. Examples of these spectral editing methods are provided for 3-methylglutaric acid, fumaric acid monoethyl ester, and two complex natural products: methyl o-methylpodocarpate and 10-deacetylbaccatin III.

  4. A (13)C NMR analysis of the effects of electron radiation on graphite/polyetherimide composites

    NASA Technical Reports Server (NTRS)

    Ferguson, Milton W.

    1989-01-01

    Initial investigations have been made into the use of high resolution nuclear magnetic resonance (NMR) for the characterization of radiation effects in graphite and Kevlar fibers, polymers, and the fiber/matrix interface in graphite/polyetherimide composites. Sample preparation techniques were refined. Essential equipment has been procured. A new NMR probe was constructed to increase the proton signal-to-noise ratio. Problem areas have been identified and plans developed to resolve them.

  5. 13C NMR shielding tensors of carboxyl carbon in amino acids calculated by ONIOM method

    Microsoft Academic Search

    Anmin Zheng; Minghui Yang; Yong Yue; Chaohui Ye; Feng Deng

    2004-01-01

    Our-own-N-layered integrated molecular orbital+molecular mechanics (ONIOM) method has been applied to calculate 13C chemical shift shielding tensor of the carboxyl carbon in three amino acid crystals. The calculated shielding tensors are in good agreement with the experimental values. The root mean square (RMS) has dramatically decreased to 5.9 ppm compared to that (35.5 ppm) previously reported in reference. The present

  6. 13C NMR Relaxation Studies of Molecular Motion in Peptide Fragments from Human Transthyretin

    NASA Astrophysics Data System (ADS)

    Jarvis, J. A.; Craik, D. J.

    Natural-abundance 13C T1 and NOE measurements have been made for backbone and side-chain sites in peptide fragments of transthyretin (TTR 10-20, TTR 105-115, and TTR 105-115 Met111) at 13C Larmor frequencies of 125 and 75 MHz. These peptides have previously been implicated in the formation of amyloid fibrils, The data were systematically assessed for their consistency with theoretical relaxation parameters derived from models of molecular motion, It was shown that of four models, ranging from simple isotropic motion to one defining internal wobbling of the 13C- 1H vector, the "model-free approach" (Lipari and Szabo, J. Am. Chem. Soc.104, 4546, 1982) was best able to predict the experimental data, These peptides exhibited overall correlation times close to 1 ns. Internal motions with effective correlation times of 0.08 ns were observed for backbone carbon sites, and side-chain carbons exhibited more rapid and less ordered motions, No indication of retarded motion due to the presence of small peptide aggregates was detected, in agreement with reports of the rapid incorporation of these species into amyloid fibrils.

  7. Observation of 1H-13C and 1H-1H proximities in a paramagnetic solid by NMR at high magnetic field under ultra-fast MAS.

    PubMed

    Li, Shenhui; Trébosc, Julien; Lafon, Olivier; Zhou, Lei; Shen, Ming; Pourpoint, Frédérique; Amoureux, Jean-Paul; Deng, Feng

    2015-02-01

    The assignment of NMR signals in paramagnetic solids is often challenging since: (i) the large paramagnetic shifts often mask the diamagnetic shifts specific to the local chemical environment, and (ii) the hyperfine interactions with unpaired electrons broaden the NMR spectra and decrease the coherence lifetime, thus reducing the efficiency of usual homo- and hetero-nuclear NMR correlation experiments. Here we show that the assignment of (1)H and (13)C signals in isotopically unmodified paramagnetic compounds with moderate hyperfine interactions can be facilitated by the use of two two-dimensional (2D) experiments: (i) (1)H-(13)C correlations with (1)H detection and (ii) (1)H-(1)H double-quantum?single-quantum correlations. These methods are experimentally demonstrated on isotopically unmodified copper (II) complex of l-alanine at high magnetic field (18.8 T) and ultra-fast Magic Angle Spinning (MAS) frequency of 62.5 kHz. Compared to (13)C detection, we show that (1)H detection leads to a 3-fold enhancement in sensitivity for (1)H-(13)C 2D correlation experiments. By combining (1)H-(13)C and (1)H-(1)H 2D correlation experiments with the analysis of (13)C longitudinal relaxation times, we have been able to assign the (1)H and (13)C signals of each l-alanine ligand. PMID:25557861

  8. Identification of reaction products and intermediates of aromatic-amine dehydrogenase by 15N and 13C NMR.

    PubMed

    Bishop, G R; Zhu, Z; Whitehead, T L; Hicks, R P; Davidson, V L

    1998-03-15

    13C- and 15N-NMR studies of the reaction of aromatic amine dehydrogenase (AADH) with methylamine demonstrated that the products of the reductive half-reaction are an equivalent of formaldehyde hydrate and a reduced aminoquinol form of the tryptophan tryptophylquinone (TTQ) cofactor which contains covalently bound substrate-derived N. These data are consistent with the Ping Pong kinetic mechanism and aminotransferase-type chemical reaction mechanism which have been previously proposed for AADH. Comparison of the 15N-NMR spectra of the aminoquinol TTQ intermediates of AADH and methylamine dehydrogenase (MADH) revealed that the substrate-derived aminoquinol N of AADH and MADH exhibited distinct 15N chemical shifts which are separated by approx. 7 p.p.m. In each case, the signal for the substrate-derived aminoquinol N appears optimally with short pulse delay and exhibits a relaxation time and chemical shift which are consistent with 15N covalently bound to an aromatic ring (i.e. aminoquinol) which is attached to a rigid protein matrix. The aminoquinol of AADH is less stable against reoxidation than that of MADH. These data suggest that differences in the active-site mediated electrostatic environments of the aminoquinol N in the respective enzymes may influence both the observed 15N chemical shift and the relative reactivities of the TTQ aminoquinols towards oxygen. These data also demonstrate the utility of 13C- and 15N-NMR spectroscopy as a tool for monitoring the intermediates and products of enzyme-catalysed transformations. PMID:9494080

  9. Restraints on backbone conformations in solid state NMR studies of uniformly labeled proteins from quantitative amide 15N–15N and carbonyl 13C13C dipolar recoupling data

    PubMed Central

    Hu, Kan-Nian; Qiang, Wei; Bermejo, Guillermo A.; Schwieters, Charles D.; Tycko, Robert

    2013-01-01

    Recent structural studies of uniformly 15N, 13C-labeled proteins by solid state nuclear magnetic resonance (NMR) rely principally on two sources of structural restraints: (i) restraints on backbone conformation from isotropic 15N and 13C chemical shifts, based on empirical correlations between chemical shifts and backbone torsion angles; (ii) restraints on inter-residue proximities from qualitative measurements of internuclear dipole–dipole couplings, detected as the presence or absence of inter-residue crosspeaks in multidimensional spectra. We show that site-specific dipole–dipole couplings among 15N-labeled backbone amide sites and among 13C-labeled backbone carbonyl sites can be measured quantitatively in uniformly-labeled proteins, using dipolar recoupling techniques that we call 15N-BARE and 13C-BARE (BAckbone REcoupling), and that the resulting data represent a new source of restraints on backbone conformation. 15N-BARE and 13C-BARE data can be incorporated into structural modeling calculations as potential energy surfaces, which are derived from comparisons between experimental 15N and 13C signal decay curves, extracted from crosspeak intensities in series of two-dimensional spectra, with numerical simulations of the 15N-BARE and 13C-BARE measurements. We demonstrate this approach through experiments on microcrystalline, uniformly 15N, 13C-labeled protein GB1. Results for GB1 show that 15N-BARE and 13C-BARE restraints are complementary to restraints from chemical shifts and inter-residue crosspeaks, improving both the precision and the accuracy of calculated structures. PMID:22449573

  10. The guest ordering and dynamics in urea inclusion compounds studied by solid-state 1H and 13C MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, Xiaorong; Müller, Klaus

    2011-12-01

    Urea inclusion compounds with different guest species were studied by 13C CP MAS and 1H MAS NMR spectroscopy. It is possible to arrange the asymmetric guest species in three different ways: head-head, head-tail and tail-tail. 13C CP MAS NMR studies indicate that the preference arrangement is determined by the interaction strength of the end functional groups. 13C relaxation experiments are used to study the dynamic properties of urea inclusion compounds. 13C relaxation studies on urea inclusion compounds with n-alkane or decanoic acid show that the 13C T1 and 13C T1? values exhibit the position dependence towards the center of the chain, indicating internal chain mobility. The analysis of variable-temperature 13C T1? experiments on urea inclusion compounds with hexadecane and pentadecane, for the first time, suggests that chain fluctuations and lateral motion of n-alkane guests may contribute to the 13C T1? relaxation.

  11. Kinetic analysis of glycogen turnover: relevance to human brain 13C-NMR spectroscopy

    PubMed Central

    DiNuzzo, Mauro

    2013-01-01

    A biophysical model of the glycogen molecule is developed, which takes into account the points of attack of synthase and phosphorylase at the level of the individual glucose chain. Under the sole assumption of steric effects governing enzyme accessibility to glucosyl residues, the model reproduces the known equilibrium structure of cellular glycogen at steady state. In particular, experimental data are reproduced assuming that synthase (1) operates preferentially on inner chains of the molecule and (2) exhibits a faster mobility than phosphorylase in translocating from an attacked chain to another. The model is then used to examine the turnover of outer versus inner tiers during the labeling process of isotopic enrichment (IE) experiments. Simulated data are fitted to in vivo 13C nuclear magnetic resonance spectroscopy measurements obtained in the human brain under resting conditions. Within this experimental set-up, analysis of simulated label incorporation and retention shows that 7% to 35% of labeled glucose is lost from the rapidly turning-over surface of the glycogen molecule when stimulation onset is delayed by 7 to 11.5?hours after the end of [1-13C]glucose infusion as done in actual procedures. The substantial label washout before stimulation suggests that much of the subsequent activation-induced glycogenolysis could remain undetected. Overall, these results show that the molecular structure significantly affects the patterns of synthesis and degradation of glycogen, which is relevant for appropriate design of labeling experiments aiming at investigating the functional roles of this glucose reserve. PMID:23756693

  12. Molecular composition of recycled organic wastes, as determined by solid-state {sup 13}C NMR and elemental analyses

    SciTech Connect

    Eldridge, S.M., E-mail: simon.eldridge@dpi.nsw.gov.au [Environmental Futures Centre, School of Environment, Griffith University, Nathan, QLD 4111 (Australia); NSW Department of Primary Industries, Bruxner Highway, Wollongbar, NSW 2477 (Australia); Chen, C.R. [Environmental Futures Centre, School of Environment, Griffith University, Nathan, QLD 4111 (Australia); Xu, Z.H. [Environmental Futures Centre, School of Biomolecular and Physical Sciences, Griffith University, Nathan, QLD 4111 (Australia); Nelson, P.N. [School of Earth and Environmental Sciences, James Cook University, Cairns, QLD 4870 (Australia); Boyd, S.E. [Environmental Futures Centre, School of Biomolecular and Physical Sciences, Griffith University, Nathan, QLD 4111 (Australia); Meszaros, I. [Formerly NSW Department of Primary Industries, Richmond, NSW 2753 (Australia); Chan, K.Y. [Graduate School of Environment, Macquarie University, North Ryde, NSW 2109 (Australia); Formerly NSW Department of Primary Industries, Richmond, NSW 2753 (Australia)

    2013-11-15

    Highlights: • Model estimated the molecular C components well for most RO wastes. • Molecular nature of organic matter in RO wastes varied widely. • Molecular composition by NMR modelling preferable to extraction techniques. • Some model shortcomings in estimating molecular composition of biochars. • Waste molecular composition important for carbon/nutrient outcomes in soil. - Abstract: Using solid state {sup 13}C NMR data and elemental composition in a molecular mixing model, we estimated the molecular components of the organic matter in 16 recycled organic (RO) wastes representative of the major materials generated in the Sydney basin area. Close correspondence was found between the measured NMR signal intensities and those predicted by the model for all RO wastes except for poultry manure char. Molecular nature of the organic matter differed widely between the RO wastes. As a proportion of organic C, carbohydrate C ranged from 0.07 to 0.63, protein C from <0.01 to 0.66, lignin C from <0.01 to 0.31, aliphatic C from 0.09 to 0.73, carbonyl C from 0.02 to 0.23, and char C from 0 to 0.45. This method is considered preferable to techniques involving imprecise extraction methods for RO wastes. Molecular composition data has great potential as a predictor of RO waste soil carbon and nutrient outcomes.

  13. Hydration properties of regioselectively etherified celluloses monitored by 2H and 13C solid-state MAS NMR spectroscopy.

    PubMed

    Larsen, Flemming H; Schöbitz, Michael; Schaller, Jens

    2012-06-20

    The hydration properties of 2,3-O-hydroxypropylcellulose (HPC) and 2,3-O-hydroxyethylcellulose (HEC) were analyzed by multi-nuclear solid-state MAS NMR spectroscopy. By 13C single-pulse (SP) MAS and cross-polarization (CP) MAS NMR, differences between the immobile regions and all parts of the polysaccharides were detected as a function of hydration. Complementary information about the water environments was observed by 2H MAS NMR. By this approach it was demonstrated that side chains in 2,3-O-HPC and 2,3-O-HEC were easier to hydrate than the cellulose backbone. Furthermore the motion of water was more restricted (slower) in 2,3-O-HPC than in 2,3-O-HEC. For both polysaccharides the hydration could be explained by a two-step process: in step one increased ordering of the immobile regions occurs after which the entire polymer is hydrated in step two. PMID:24750769

  14. Microscopic structural analysis of fractured silk fibers from Bombyx mori and Samia cynthia ricini using 13C CP\\/MAS NMR with a 1 mm microcoil MAS NMR probehead

    Microsoft Academic Search

    Kazuo Yamauchi; Shizuo Yamasaki; Rui Takahashi; Tetsuo Asakura

    2010-01-01

    Conformational changes have been studied in silk fibers from the domestic silkworm Bombyx mori and a wild silkworm Samia cynthia ricini as a result of fractured by stretching. About 300 samples consisting of only the fractured regions of [1-13C]Ala or [1-13C]Gly labeled silk fibers were collected and observed by 13C CP\\/MAS NMR spectra. The total amount of these fractured fibers

  15. Multidimensional High-Resolution Magic Angle Spinning and Solution-State NMR Characterization of 13C-labeled Plant Metabolites and Lignocellulose

    PubMed Central

    Mori, Tetsuya; Tsuboi, Yuuri; Ishida, Nobuhiro; Nishikubo, Nobuyuki; Demura, Taku; Kikuchi, Jun

    2015-01-01

    Lignocellulose, which includes mainly cellulose, hemicellulose, and lignin, is a potential resource for the production of chemicals and for other applications. For effective production of materials derived from biomass, it is important to characterize the metabolites and polymeric components of the biomass. Nuclear magnetic resonance (NMR) spectroscopy has been used to identify biomass components; however, the NMR spectra of metabolites and lignocellulose components are ambiguously assigned in many cases due to overlapping chemical shift peaks. Using our 13C-labeling technique in higher plants such as poplar samples, we demonstrated that overlapping peaks could be resolved by three-dimensional NMR experiments to more accurately assign chemical shifts compared with two-dimensional NMR measurements. Metabolites of the 13C-poplar were measured by high-resolution magic angle spinning NMR spectroscopy, which allows sample analysis without solvent extraction, while lignocellulose components of the 13C-poplar dissolved in dimethylsulfoxide/pyridine solvent were analyzed by solution-state NMR techniques. Using these methods, we were able to unambiguously assign chemical shifts of small and macromolecular components in 13C-poplar samples. Furthermore, using samples of less than 5 mg, we could differentiate between two kinds of genes that were overexpressed in poplar samples, which produced clearly modified plant cell wall components. PMID:26143886

  16. Decreased TCA cycle rate in the rat brain after acute 3NP treatment measured by in vivo 1H-{13C} NMR spectroscopy

    Microsoft Academic Search

    Pierre-Gilles Henry; Vincent Lebon; Francoise Vaufrey; Emmanuel Brouillet; Philippe Hantrayeand; Gilles Bloch

    Inhibition of succinate dehydrogenase (SDH) by the mitoch- ondrial toxin 3-nitropropionic acid (3-NP) has gained accept- ance as an animal model of Huntington's disease. In this study 13 C NMR spectroscopy was used to measure the tricarboxylic acid (TCA) cycle rate in the rat brain after 3-NP treatment. The time course of both glutamate C4 and C3 13C labelling was

  17. 2D 1H and 13C NMR conformational studies of thienopyridines and carboline biarylic compounds

    NASA Astrophysics Data System (ADS)

    Corona, D.; Díaz, E.; Barrios, H.; Sánchez, E.; Alvarado, C.; Jankowski, C. K.; Guzmán, A.

    2009-10-01

    In this paper, we report on conformational studies of biarylic compounds, as prepared through the well-known aza-Wittig methodology. The conformational studies were mainly realized by bidimensional (2D) nuclear magnetic resonance spectroscopy (NMR) and NOESY experiments. The conformational behavior showed that these biarylic compounds display an orthogonal symmetry and adopt a characteristic arrangement around the pivotal bond. Molecular modeling calculations were performed to support structure conformations.

  18. Solid-state 13C NMR and quantum chemical investigation of metal diene complexes.

    PubMed

    Ma, Zhiru; Facelli, Julio C; Pugmire, Ronald J; Dunn, Brian C; Turpin, Gregory C; Eyring, Edward M; Ernst, Richard D

    2007-05-01

    This paper presents novel measurements and calculations of the olefinic (13)C chemical shift tensor principal values in several metal diene complexes. The experimental values and the calculations show shifts as large as 70 ppm with respect to the values in the parent olefinic compounds. These shifts are highly anisotropic, with the largest ones observed in the less shielded principal components and the smallest ones in the most shielded principal components of the tensor. The orientations of the principal components of the tensors remain, within 10 degrees , at their directions in ethylene and other olefinic compounds. The calculations, performed using the GIAO method and the LanDZ pseudopotential basis set, show good agreement with the experiments, and were used to establish definite evidence for the existence of a Cl-bridge structure in the bicyclo[2.2.1]hepta-2,5-diene (BCHD)dichlororuthenium(II) polymer. PMID:17394221

  19. Comparison of the substituent effects on the (13) C NMR with the (1) H NMR chemical shifts of CH?N in substituted benzylideneanilines.

    PubMed

    Wang, Linyan; Cao, Chaotun; Cao, Chenzhong

    2015-07-01

    Fifty-two samples of substituted benzylideneanilines XPhCH?NPhYs (XBAYs) were synthesized, and their NMR spectra were determined in this paper. Together with the NMR data of other 77 samples of XBAYs quoted from literatures, the (1) H NMR chemical shifts (?H (CH?N)) and (13) C NMR chemical shifts (?C (CH?N)) of the CH?N bridging group were investigated for total of 129 samples of XBAYs. The result shows that the ?H (CH?N) and ?C (CH?N) have no distinctive linear relationship, which is contrary to the theoretical thought that declared the ?H (CH?N) values would increase as the ?C (CH?N) values increase. With the in-depth analysis, we found that the effects of ?F and ?R of X/Y group on the ?H (CH?N) and the ?C (CH?N) are opposite; the effects of the substituent specific cross-interaction effect between X and Y (??(2) ) on the ?H (CH?N) and the ?C (CH?N) are different; the contributions of parameters in the regression equations of the ?H (CH?N) and the ?C (CH?N) [Eqns and 7), respectively] also have an obvious difference. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26031232

  20. The influence of thermochemical treatments on the lignocellulosic structure of wheat straw as studied by natural abundance 13C NMR.

    PubMed

    Habets, S; de Wild, P J; Huijgen, W J J; van Eck, E R H

    2013-10-01

    The effects of thermochemical treatments (aquathermolysis, pyrolysis, and combinations thereof) on the lignocellulosic structure and composition of wheat straw were studied with (13)C and (1)H solid state NMR spectroscopy and proton T1? relaxation measurements. Results show that aquathermolysis removes hemicellulose, acetyl groups, and ash minerals. As a result, the susceptibility of lignocellulose to pyrolysis is reduced most likely due to the removal of catalytically active salts, although recondensation of lignin during aquathermolysis treatment can also play a role. In contrast to pyrolysis of wheat straw, pyrolysis of aquathermolysed wheat straw leaves traces of cellulose in the char as well as more intense lignin methoxy peaks. Finally, it was found that both pyrolysis chars contain aliphatic chains, which were attributed to the presence of cutin or cutin-like materials, a macromolecule that covers the aerial surface of plants, not soluble in water and seemingly stable under the pyrolysis conditions applied. PMID:23973979

  1. Communication: Competition between ?⋯? interaction and halogen bond in solution: A combined 13C NMR and density functional theory study

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Ji, Baoming; Tian, Anmin; Wang, Weizhou

    2012-04-01

    Competition between ?⋯? interaction and halogen bond in solution has been investigated by using carbon nuclear magnetic resonance spectroscopy (13C NMR) combined with density functional theory calculation. Both experimental and theoretical results clearly show that there are no C-Cl⋯? or C-Br⋯? halogen bonds and only the ?⋯? interactions exist in the binary liquid mixtures of C6D6 with C6F5Cl and C6F5Br, respectively. The case is totally different for the binary liquid mixtures of C6D6 with C6F5I in which the C-I⋯? halogen bonds not the ?⋯? interactions are present. The important role of entropy in the competition between ?⋯? interaction and halogen bond in solution was also discussed.

  2. Temperature dependence of the folding and unfolding kinetics of the GCN4 leucine zipper via 13C(alpha)-NMR.

    PubMed Central

    Holtzer, M E; Bretthorst, G L; d'Avignon, D A; Angeletti, R H; Mints, L; Holtzer, A

    2001-01-01

    Studies by one-dimensional NMR are reported on the interconversion of folded and unfolded forms of the GCN4 leucine zipper in neutral saline buffer. The peptide bears 99% 13C(alpha) labels at three sites: V9, L12, and G31. Time-domain 13C(alpha)-NMR spectra are interpreted by global Bayesian lineshape analysis to extract the rate constants for both unfolding and folding as functions of temperature in the range 47-71 degrees C. The data are well fit by the assumption that the same rate constants apply at each labeled site, confirming that only two conformational states need be considered. Results show that 1) both processes require a free energy of activation; 2) unfolding is kinetically enthalpy-opposed and entropy-driven, while folding is the opposite; and 3) the transition state dimer ensemble averages approximately 40% helical. The activation parameters for unfolding, derived from NMR data at the elevated temperatures where both conformations are populated, lead to estimates of the rate constant at low temperatures (5-15 degrees C) that agree with extant values determined by stopped-flow CD via dilution from denaturing media. However, the corresponding estimated values for the folding rate constant are larger by two to three orders of magnitude than those obtained by stopped flow. We propose that this apparent disagreement is caused by the necessity, in the stopped-flow experiment, for initiation of new helices as the highly denaturant-unfolded molecule adjusts to the newly created benign solvent conditions. This must reduce the success rate of collisions in producing the folded molecule. In the NMR determinations, however, the unfolded chains always have a small, but essential, helix content that makes such initiation unnecessary. Support for this hypothesis is adduced from recent extant experiments on the helix-coil transition in single-chain helical peptides and from demonstration that the folding rate constants for coiled coils, as obtained by stopped flow, are influenced by the nature of the denaturant used. PMID:11159461

  3. Spectral fitting for signal assignment and structural analysis of uniformly 13 C-labeled solid proteins by simulated annealing based on chemical shifts and spin dynamics

    Microsoft Academic Search

    Yoh Matsuki; Hideo Akutsu; Toshimichi Fujiwara

    2007-01-01

    We describe an approach for the signal assignment and structural analysis with a suite of two-dimensional 13C13C magic-angle-spinning solid-state NMR spectra of uniformly 13C-labeled peptides and proteins. We directly fit the calculated spectra to experimental ones by simulated annealing in restrained\\u000a molecular dynamics program CNS as a function of atomic coordinates. The spectra are calculated from the conformation dependent\\u000a chemical

  4. Preservation of proteinaceous material during the degradation of the green alga Botryococcus braunii: A solid-state 2D 15N 13C NMR spectroscopy study

    NASA Astrophysics Data System (ADS)

    Zang, Xu; Nguyen, Reno T.; Harvey, H. Rodger; Knicker, Heike; Hatcher, Patrick G.

    2001-10-01

    Using solid-state cross-polarization-magic-angle-spinning (CPMAS) 13C and 15N nuclear magnetic resonance (NMR) and 2-D double cross polarization (DCP) MAS 15N 13C NMR techniques, microbially degraded Botryococcus braunii was analyzed to study the chemical nature of organic nitrogen in the algal residue. The amide linkage, as found in protein, was observed as the major nitrogen component in 201-day-old degraded algae. No significant amount of heterocyclic nitrogen, or evidence for melanoidin products, was found. The results strongly suggest that proteinaceous material can survive early diagenesis and be preserved via its encapsulation by refractory, macromolecular, organic matter.

  5. Characterization of alkyl carbon in forest soils by CPMAS 13C NMR spectroscopy and dipolar dephasing

    USGS Publications Warehouse

    Kogel-Knabner, I.; Hatcher, P.G.

    1989-01-01

    Samples obtained from forest soils at different stages of decomposition were treated sequentially with chloroform/methanol (extraction of lipids), sulfuric acid (hydrolysis), and sodium chlorite (delignification) to enrich them in refractory alkyl carbon. As revealed by NMR spectroscopy, this treatment yielded residues with high contents of alkyl carbon. In the NMR spectra of residues obtained from litter samples, resonances for carbohydrates are also present, indicating that these carbohydrates are tightly bound to the alkyl carbon structures. During decomposition in the soils this resistant carbohydrate fraction is lost almost completely. In the litter samples the alkyl carbon shows a dipolar dephasing behavior indicative of two structural components, a rigid and a more mobile component. As depth and decomposition increase, only the rigid component is observed. This fact could be due to selective degradation of the mobile component or to changes in molecular mobility during decomposition, e.g., because of an increase in cross linking or contact with the mineral matter of the soil.

  6. Charge disproportionation in ( TMTTF )2 SCN observed by 13 C NMR

    NASA Astrophysics Data System (ADS)

    Fujiyama, Shigeki; Nakamura, Toshikazu

    2004-07-01

    The results of the C13NMR spectra and nuclear spin-lattice relaxation rate 1/T1 for the quasi-one-dimensional quarter-filled organic material (TMTTF)2SCN are presented. Below the anion ordering temperature (TAO) , a new broad line appears in the NMR spectra and the intensity of the distinct line owing to the inner carbon site from the inversion center is almost halved. The remarkable difference in the temperature dependence of 1/T1 below TAO for the two sharp lines corresponding to outer and inner carbon sites shows the development of a local electronic state. Our simple model of a charge configuration based on the electrostatic interaction between the SCN anions and TMTTF molecules is consistent with our observation of a local gap for the spin excitation. Nevertheless, we reveal that only the electrostatic interaction is insufficient to reproduce the observed divergence of the frequency shift and the linewidth of the newly appearing broad line stemming from the charge-accepting inner site at a much lower temperature than TAO .

  7. Molecular composition of recycled organic wastes, as determined by solid-state 13C NMR and elemental analyses.

    PubMed

    Eldridge, S M; Chen, C R; Xu, Z H; Nelson, P N; Boyd, S E; Meszaros, I; Chan, K Y

    2013-11-01

    Using solid state (13)C NMR data and elemental composition in a molecular mixing model, we estimated the molecular components of the organic matter in 16 recycled organic (RO) wastes representative of the major materials generated in the Sydney basin area. Close correspondence was found between the measured NMR signal intensities and those predicted by the model for all RO wastes except for poultry manure char. Molecular nature of the organic matter differed widely between the RO wastes. As a proportion of organic C, carbohydrate C ranged from 0.07 to 0.63, protein C from <0.01 to 0.66, lignin C from <0.01 to 0.31, aliphatic C from 0.09 to 0.73, carbonyl C from 0.02 to 0.23, and char C from 0 to 0.45. This method is considered preferable to techniques involving imprecise extraction methods for RO wastes. Molecular composition data has great potential as a predictor of RO waste soil carbon and nutrient outcomes. PMID:23896223

  8. 1H, 13C, 15N NMR analysis of sildenafil base and citrate (Viagra) in solution, solid state and pharmaceutical dosage forms.

    PubMed

    Wawer, Iwona; Pisklak, Maciej; Chilmonczyk, Zdzis?aw

    2005-08-10

    Sildenafil citrate (SC) (Viagra) and sildenafil base in pure form are easily and unequivocally characterized by multinuclear NMR spectroscopy. Analysis of chemical shifts indicates that: (i) N6-H forms intramolecular hydrogen bonds, (ii) N25 is protonated in the salt and (iii) intermolecular OH...N hydrogen bonds involving N2 and N4 are present in the solid sildenafil citrate. 13C CPMAS NMR method has been proposed for the identification and quantitation of Viagra in its pharmaceutical formulations. PMID:16087048

  9. Determination of the structural changes by Raman and {sup 13}C CP/MAS NMR spectroscopy on native corn starch with plasticizers

    SciTech Connect

    Cozar, O. [Academy of Romanian Scientists, Splaiul Independentei 54, 050094, Bucharest, Romania and National Institute of Research-Development for Machines and Installations Designed to Agriculture and Food Industry - INMA Bucure?ti - Cluj-Napoca Branch (Romania)] [Academy of Romanian Scientists, Splaiul Independentei 54, 050094, Bucharest, Romania and National Institute of Research-Development for Machines and Installations Designed to Agriculture and Food Industry - INMA Bucure?ti - Cluj-Napoca Branch (Romania); Filip, C.; Tripon, C. [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)] [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania); Cioica, N.; Co?a, C.; Nagy, E. M. [National Institute of Research-Development for Machines and Installations Designed to Agriculture and Food Industry - INMA Bucure?ti - Cluj-Napoca Branch, RO-400458 Cluj-Napoca (Romania)] [National Institute of Research-Development for Machines and Installations Designed to Agriculture and Food Industry - INMA Bucure?ti - Cluj-Napoca Branch, RO-400458 Cluj-Napoca (Romania)

    2013-11-13

    The plasticizing - antiplasticizing effect of water and glycerol contents on native corn starch samples is investigated by FT-Raman and {sup 13}C CP/MAS NMR spectroscopy. The presence of both amorphous and crystalline structural phases was evidenced in pure native corn starch and also in the samples containing plasticizers. Among the crystalline starch structures, the A- and V- types were suggested by CP/MAS NMR spectra.

  10. Effect of beta-carotene on structural and dynamic properties of model phosphatidylcholine membranes. II. A 31P-NMR and 13C-NMR study.

    PubMed

    Jezowska, I; Wolak, A; Gruszecki, W I; Strza?ka, K

    1994-08-24

    Spin label EPR studies (Strza?ka and Gruszecki (1994) Biochim. Biophys. Acta 1194, 138-142) revealed that beta-carotene affects structural and dynamic properties of model dipalmitoylphosphatidylcholine (DPPC) membranes (multilamellar liposomes) more than polar carotenoid lutein. NMR measurements presented in this paper demonstrate that beta-carotene exerts different effect on various groups of the DPPC molecule. It was found that beta-carotene: (1) increases motional freedom of lipid headgroups as revealed by means of 31P-NMR; (2) increases motional freedom of alkyl chains forming the hydrophobic core of the membrane greater than that of a choline moiety as revealed by means of 13C-NMR. In all cases the effect of beta-carotene with respect to the dynamics of DPPC molecules is found to be more pronounced below the main phase transition temperature than in the membrane's fluid state. The influence of beta-carotene on the molecular dynamics of DPPC molecules is discussed in terms of localization and orientation of this pigment within lipid bilayer. PMID:8075128

  11. Estimation of procyanidin/prodelphinidin and cis/trans flavanol ratios of condensed tannin fractions by 1H-13C HSQC NMR spectroscopy: Correlation with thiolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Integration of cross-peak contours of H/C-2’,6’ signals from prodelphinidin (PD) and of H/C-6’ signals from procyanidin (PC) units in 1H-13C HSQC nuclear magnetic resonance (NMR) spectra of condensed tannins yielded nuclei-adjusted PC/PD estimates that were highly correlated with PC/PD ratios obtain...

  12. Chemical structures of swine-manure chars produced under different carbonization conditions investigated by advanced solid-state 13C nuclear magnetic resonance (NMR) spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two types of swine manure chars, hydrothermally-produced hydrochar and slow-pyrolysis pyrochar, and their raw swine manure solid were characterized using advanced 13C solid-state nuclear magnetic resonance (NMR) spectroscopy. Compared with the parent raw swine manure, both hydrochars and pyrochar di...

  13. Estimating the molecular composition of a diverse range of natural organic materials from solid-state 13 C NMR and elemental analyses

    Microsoft Academic Search

    Paul N. Nelson; Jeffrey A. Baldock

    2005-01-01

    Most techniques for determining the chemical nature of natural organic matter in soil, sediment and water require prior extraction or concentration steps that are not quantitative and that create artifacts. 13C nuclear magnetic resonance (NMR) analysis can avoid these problems, but it gives little information at the scale of molecules. Here we show that the molecular composition of a diverse

  14. High-resolution solid-state {sup 13}C and {sup 15}N NMR spectroscopy of pyrazole and 3,5-dimethylpyrazole adsorbed on alumina and silica

    SciTech Connect

    Aguilar-Parrilla, F.; Limbach, H.H. [Ciudad Universitaria, Madrid (Spain); Claramunt, R.M. [Instituto de Quimica Medica, Madrid (Spain)] [and others

    1994-09-01

    Using pyrazole and 3,5-dimethylpyrazole mixtures with alumina and silica, high-resolution solid state {sup 13}C and {sup 15}N CPMAS NMR was performed to compare the spectra. The NH-N proton tautomers resulting depend strongly on the environment. 70 refs., 8 figs., 4 tabs.

  15. FT-RAMAN AND 13C CP-MAS NMR SPECTROSCOPIC ASSESSMENT OF CONFORMATIONAL CHANGES IN PROTEIN AND STARCH UNDER VARIOUS PARABOILING CONDITIONS FOR RICE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    FT-Raman and solid-state 13C CP-MAS NMR spectroscopies were employed to assess the conformational changes to protein and starch in rice under variable conditions of parboiling. TOX 3108 rice from Ghana, was parboiled by the soaking-steaming-drying method under conditions that mimicked various local...

  16. CHANGES IN PROTEIN AND STARCH CONFORMATION DURING VARIABLE TEMPERATURE PARBOILING OF RICE: FT-RAMAN AND 13C CP-MAS NMR SPECTROSCOPIC ASSESSMENT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    FT-Raman and solid-state 13C cross polarization magic-angle spinning (CP-MAS) NMR spectroscopies were employed to assess the conformational changes to protein and starch in paddy rice under variable conditions of parboiling. Rice variety, TOX 3108 from Ghana, was parboiled by the soaking-steaming-d...

  17. 1H-13C HSQC NMR spectroscopy for estimating procyanidin/prodelphinidin and cis/trans flavan-3-ol ratios of condensed tannin samples: correlation with thiolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Studies with a diverse array of 22 condensed tannin (CT) fractions from 9 plant species demonstrated that procyanidin/prodelphinidin (PC/PD) and cis/trans flavan-3-ol ratios can be appraised by 1H-13C HSQC NMR. The method was developed from fractions containing 44 to ~100% CT, PC/PD ratios ranging f...

  18. PMR and 13 C NMR spectra of biologically active compounds. XIII.* Structure and stereochemistry of a new phenylpropanoid glycoside isolated from Onopordum acanthium seeds

    Microsoft Academic Search

    T. V. Tyumkina; I. F. Nuriev; L. M. Khalilov; V. R. Akhmetova; U. M. Dzhemilev

    2009-01-01

    The structure of a new compound was determined using PMR and 13C NMR spectroscopy (HHCOSY, HSBC, HMBC, ROESY) as 2-[3?-methoxy,4-O-?-D-galactopyranos-1-yl)benzyl]-3-(3?,4?-dimethoxybenzyl)-4hydroxybutyric acid, which was isolated for the first time from\\u000a seeds of Scotch thistle Onopordum acanthium L.

  19. Molecular structure, vibrational and 13C NMR spectra of two ent-kaurenes spirolactone type diterpenoids rabdosinate and rabdosin B: a combined experimental and density functional methods.

    PubMed

    Wang, Tao; Wang, Xueliang

    2015-01-25

    The title compounds, rabdosinate and rabdosin B, were isolated from the leaves of Isodon japonica, and characterized by IR-NMR spectroscopy. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO-13C) chemical shift values of the title compounds have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set. In addition, obtained results were related to the linear regression of experimental 13C NMR chemical shifts values. The integral equation formalism polarized continuum model (IEFPCM) was used in treating chloroform solvation effects on optimized structural parameters and 13C chemical shifts. Besides, molecular electrostatic potential (MEP), HOMO-LUMO analysis were performed by the B3LYP method. PMID:25123947

  20. Molecular structure, vibrational and 13C NMR spectra of two ent-kaurenes spirolactone type diterpenoids rabdosinate and rabdosin B: A combined experimental and density functional methods

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Wang, Xueliang

    2015-01-01

    The title compounds, rabdosinate and rabdosin B, were isolated from the leaves of Isodon japonica, and characterized by IR-NMR spectroscopy. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO-13C) chemical shift values of the title compounds have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set. In addition, obtained results were related to the linear regression of experimental 13C NMR chemical shifts values. The integral equation formalism polarized continuum model (IEFPCM) was used in treating chloroform solvation effects on optimized structural parameters and 13C chemical shifts. Besides, molecular electrostatic potential (MEP), HOMO-LUMO analysis were performed by the B3LYP method.

  1. Dynamic 13C NMR investigations of substrate interaction and catalysis by cobalt(II) human carbonic anhydrase I.

    PubMed

    Williams, T J; Henkens, R W

    1985-05-01

    Using 13C NMR spectroscopy, we have further investigated the binding of HCO3- in the active site of an artificial form of human carbonic anhydrase I in which the native zinc is replaced by Co(II). The Co(II) enzyme, unlike all other metal-substituted derivatives, has functional properties closely similar to those of the native zinc enzyme. By measuring the spin-lattice relaxation rate and the line width for both the CO2 and HCO3- at two field strengths, we have determined both the paramagnetic effects that reflect substrate binding and the exchange effects due to catalysis at chemical equilibrium. The following are the results at 14 degrees C and pH 6.3 (1) HCO3- is bound in the active site of the catalytically competent enzyme with the 13C of the HCO3- located 3.22 +/- 0.02 A from the Co(II); (2) the apparent equilibrium dissociation constant for the bound HCO3- is 7.6 +/- 1.5 mM, determined by using the paramagnetic effects on the line widths, and 10 +/- 2 mM, determined by using the exchange effects; (3) the lifetime of HCO3- bound to the metal is (4.4 +/- 0.4) X 10(-5) s; (4) the overall catalyzed CO2 in equilibrium HCO3- exchange rate constant of the Co(II) enzyme is (9.6 +/- 0.4) X 10(3) s-1; (5) the electron spin relaxation time of the Co(II), determined by using paramagnetic effects on the bound HCO3-, is (1.1 +/- 0.1) X 10(-11) s. The data did not provide any direct information on the binding of CO2.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2990529

  2. 1H NMR, 13C NMR, and computational DFT studies of the structure of 2-acylcyclohexane-1,3-diones and their alkali metal salts in solution.

    PubMed

    Szczeci?ski, Przemys?aw; Gryff-Keller, Adam; Molchanov, Sergey

    2006-06-01

    1H and 13C NMR spectra of 2-acyl-substituted cyclohexane-1,3-diones (acyl = formyl, 1; 2-nitrobenzoyl, 2; 2-nitro-4-trifluoromethylbenzoyl, 3) and lithium sodium and potassium salts of 1 have been measured. The compound 3, known as NTBC, is a life-saving medicine applied in tyrosinemia type I. The optimum molecular structures of the investigated objects in solutions have been found using the DFT method with B3LYP functional and 6-31G** and/or 6-311G(2d,p) basis set. The theoretical values of the NMR parameters of the investigated compounds have been calculated using GIAO DFT B3LYP/6-311G(2d,p) method. The theoretical data obtained for compounds 1-3 have been exploited to interpret their experimental NMR spectra in terms of the equilibrium between different tautomers. It has been found that for these triketones an endo-tautomer prevails. The differences in NMR spectra of the salts of 1 can be rationalized taking into account the size of the cation and the degree of salt dissociation. It seems that in DMSO solution the lithium salt exists mainly as an ion pair stabilized by the chelation of a lithium cation with two oxygen atoms. The activation free energy the of formyl group rotation for this salt has been estimated to be 51.5 kJ/mol. The obtained results suggest that in all the investigated objects, including the free enolate ions, all atoms directly bonded to the carbonyl carbons lie near the same plane. Some observations concerning the chemical shift changes could indicate strong solvation of the anion of 1 by water molecules. Implications of the results obtained in this work for the inhibition mechanism of (4-hydroxyphenyl) pyruvate dioxygenase by NTBC are commented upon. PMID:16749798

  3. Interactions between a humic acid and a paramagnetic cation as assessed by CPMAS 13C NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Conte, P.; van Lagen, B.

    2009-04-01

    Humic substances (HSs) are natural organic materials playing a very important role in environment due to their ability in interacting with organic and inorganic compounds. From the one side, HSs can reduce the toxic effects of organic and inorganic contaminants, while, from the other side, they can enhance availability of nutrients, such as cations, to living organisms including plants. For this reason it is very crucial to understand the mechanisms of the interactions between humic substances and the environmentally relevant chemical components. In the present work, we have investigated the mechanisms of interaction between a HS and iron (III) by using cross polarization magic angle spinning (CPMAS) 13C NMR spectroscopy. For that, complexes between HS and different amounts of Fe(III) were prepared. All the HS-Fe(III) complexes were analysed by variable contact time (VCT) NMR experiments in order to obtain estimations of the values of the cross-polarization time (TCH) and the proton longitudinal relaxation time in the rotating frame (T1rho(H)). Results confirmed literature findings by which carboxyl groups are the most important humic fraction endowing with the ability to chelate Fe(III). However, our results also demonstrated that direct bondages between HS and Fe(III) involve the remaining polar systems such as carbohydrates and peptides. Conversely, alkyls and aromatics appeared not to be directly bound to the paramagnetic iron (III). We also evaluated the distances between Fe(III) and the different functional groups in the HS through the analysis of the proton spin diffusion into the HS-Fe(III) complexes.

  4. Effects of solvent concentration and composition on protein dynamics: (13)C MAS NMR studies of elastin in glycerol-water mixtures.

    PubMed

    Demuth, Dominik; Haase, Nils; Malzacher, Daniel; Vogel, Michael

    2015-08-01

    We use (13)C CP MAS NMR to investigate the dependence of elastin dynamics on the concentration and composition of the solvent at various temperatures. For elastin in pure glycerol, line-shape analysis shows that larger-scale fluctuations of the protein backbone require a minimum glycerol concentration of ~0.6g/g at ambient temperature, while smaller-scale fluctuations are activated at lower solvation levels of ~0.2g/g. Immersing elastin in various glycerol-water mixtures, we observe at room temperature that the protein mobility is higher for lower glycerol fractions in the solvent and, thus, lower solvent viscosity. When decreasing the temperature, the elastin spectra approach the line shape for the rigid protein at 245K for all studied samples, indicating that the protein ceases to be mobile on the experimental time scale of ~10(-5)s. Our findings yield evidence for a strong coupling between elastin fluctuations and solvent dynamics and, hence, such interaction is not restricted to the case of protein-water mixtures. Spectral resolution of different carbon species reveals that the protein-solvent couplings can, however, be different for side chain and backbone units. We discuss these results against the background of the slaving model for protein dynamics. PMID:25917596

  5. 1H and 13C NMR spectra and solution structures of novel derivatives of 5-substituted creatinines.

    PubMed

    Krawczyk, Hanna; Pietras, Agnieszka; Kraska, Anna

    2007-01-01

    Five creatinine derivatives were prepared by the treatment of creatinine with activated carbon and appropriate alcohol (1-4), or ammonia solution (5). Product structures were determined by 1H and 13C NMR spectroscopy in solution, including 2D HSQC and HMBC experiments. Then, the proton and carbon chemical shifts for these compounds were calculated using GIAO-DFT [B3LYP/6-311G(2d,p)] method and the Gaussian 03W program and furthermore for 1 and 5 using polarizable continuum model (PCM). The conclusions coming from the comparison of the experimental and theoretical spectra supported the adopted signal assignments and solved the structural problems due to the potential annular tautomerism of the investigated compounds. One can predict that 5-substituted creatinines, just like creatinine, appear in solution in the form of 2-amino-1,5-dihydro-1-methyl-4-imidazolone. Correlations between experimental and calculated substituent-induced chemical shifts for two tautomeric forms of 5-substituted creatinines indicate that the mechanism of the substituent influence in both tautomers for the investigated compounds appears to be analogous. We can predict that in solution this accepting inductive effect of substituent groups does not significantly influence the structure of creatinine molecule in solution. The analysis of coupling constants for 5-substituted creatinines gives information about conformation of the investigated molecules in solution. PMID:16920395

  6. Linking phosphorus sequestration to carbon humification in wetland soils by 31P and 13C NMR spectroscopy.

    PubMed

    Hamdan, Rasha; El-Rifai, Hasan M; Cheesman, Alexander W; Turner, Benjamin L; Reddy, K Ramesh; Cooper, William T

    2012-05-01

    Phosphorus sequestration in wetland soils is a prerequisite for long-term maintenance of water quality in downstream aquatic systems, but can be compromised if phosphorus is released following changes in nutrient status or hydrological regimen. The association of phosphorus with relatively refractory natural organic matter (e.g., humic substances) might protect soil phosphorus from such changes. Here we used hydrofluoric acid (HF) pretreatment to remove phosphorus associated with metals or anionic sorption sites, allowing us to isolate a pool of phosphorus associated with the soil organic fraction. Solution (31)P and solid state (13)C NMR spectra for wetland soils were acquired before and after hydrofluoric acid pretreatment to assess quantitatively and qualitatively the changes in phosphorus and carbon functional groups. Organic phosphorus was largely unaffected by HF treatment in soils dominated by refractory alkyl and aromatic carbon groups, indicating association of organic phosphorus with stable, humified soil organic matter. Conversely, a considerable decrease in organic phosphorus following HF pretreatment was detected in soils where O-alkyl groups represented the major fraction of the soil carbon. These correlations suggest that HF treatment can be used as a method to distinguish phosphorus fractions that are bound to the inorganic soil components from those fractions that are stabilized by incorporation into soil organic matter. PMID:22423890

  7. NMR 13C-isotopic enrichment experiments to study carbon-partitioning into organic solutes in the red alga Grateloupia doryphora.

    PubMed

    Simon-Colin, Christelle; Kervarec, Nelly; Pichon, Roger; Deslandes, Eric

    2004-01-01

    The red alga Grateloupia doryphora Montagne (Howe) (Cryptonemiales, Halymeniaceae) was used as a model to investigate the effects of changes in seawater salinity on the intracellular low-molecular-weight organic compounds. Carbon-partitioning into major organic solutes was followed by 13C nuclear magnetic resonance (NMR) spectroscopy on living algae incubated in NaH13CO3-enriched seawater, and by high resolution 1H and 13C NMR experiments performed on 13C-enriched algal extracts. NMR and high performance liquid chromatography (HPLC) analyses both demonstrated that floridoside level was the most affected by changes in salinity: it rose under the hypersaline treatment and decreased under hyposaline one. Moreover, at low salinity, the high labeling of floridoside (45.3% 13C-enrichment for C1) together with its low concentrations both provided evidence of great increase in the de novo biosynthesis and turnover rate. Our experiments also demonstrated a high incorporation of photosynthetic carbon into amino acids, especially glutamate, under hypoosmotic conditions. On the other hand, isethionic acid and N-methyl-methionine sulfoxide were only partly labeled, which indicates they do not directly derive from carbon photoassimilation. In algae exposed to high salinity, elevated concentrations of floridoside coupled to a low labeling (9.4%) were observed. These results suggest that hyperosmotic conditions stimulated floridoside biosynthesis from endogen storage products rather than from carbon assimilation through photosynthesis. PMID:15061080

  8. Study of the metabolism of /sup 13/C labeled substrates by /sup 13/C NMR spectroscopy of intact cells, tissues, and organs

    SciTech Connect

    Matwiyoff, N.A.; London, R.E.; Hutson, J.Y.

    1982-01-01

    Carbon-13 nuclear magnetic resonance spectroscopy, in conjunction with carbon-13 labeling, has become an important analytical technique for the study of biological systems and biologically important molecules. The growing list of its well established applications to isolated molecules in solution includes the investigation of: metabolic pathways; the microenvironments of ligands bound to proteins; the architecture and dynamics of macromolecules; the structures of coenzymes and other natural products; and the mechanisms of reactions. Recently interest has been reawakened in the use of the technique for the study of metabolic pathways and structural components in intact organelles, cells, and tissues. The promise and problems in the use of /sup 13/C labeling in such investigations can be illustrated by the results on suspensions of the yeast, Candida utilis.

  9. Use of solid-state sup 13 C NMR spectroscopy to quantify the degree of asymmetry of bonding for semibridging CO groups in iron carbonyl complexes

    SciTech Connect

    Hawkes, G.E.; Sales, K.D. (Queen Mary and Westfield College, London (England)); Aime, S.; Gobetto, R. (Universita de Torino (Italy)); Lian, Luyun (Univ. of Oxford (England))

    1991-04-03

    The solid-state {sup 13}C NMR spectra of some substituted iron carbonyl complexes have been analyzed to give values for the carbonyl carbon chemical shift tensor components. It is shown that the lowest frequency tensor component and the chemical shift anisotropy correlate with the degree of bonding asymmetry in double-bridging carbonyl groups, whereas the {sup 13}C isotropic chemical shift does not correlate. The correlations are proposed to form the basis for a method of estimating iron-carbon bond lengths for {mu}{sub 2}-CO groups in this type of complex. 1 table, 4 figs., 30 refs.

  10. sup 31 P and sup 13 C-NMR studies of the phosphorus and carbon metabolites in the halotolerant alga, Dunaliella salina

    SciTech Connect

    Bental, M.; Oren-Shamir, M.; Avron, M.; Degani, H. (Weizmann Institute of Science, Rehovot (Israel))

    1988-06-01

    The intracellular phosphorus and carbon metabolites in the halotolerant alga Dunaliella salina adapted to different salinities were monitored in living cells by {sup 31}P- and {sup 13}C-nuclear magnetic resonance (NMR) spectroscopy. The {sup 13}C-NMR studies showed that the composition of the visible intracellular carbon metabolites other than glycerol is not significantly affected by the salinity of the growth medium. The T{sub 1} relaxation rates of the {sup 13}C-glycerol signals in intact cells were enhanced with increasing salinity of the growth medium, in parallel to the expected increase in the intracellular viscosity due to the increase in intracellular glycerol. The {sup 31}P-NMR studies showed that cells adapted to the various salinities contained inorganic phosphate, phosphomonoesters, high energy phosphate compounds, and long chain polyphosphates. In addition, cells grown in media containing up to 1 molar NaCl contained tripolyphosphates. The tripolyphosphate content was also controlled by the availability of inorganic phosphate during cell growth. Phosphate-depleted D. salina contained no detectable tripolyphosphate signal. Excess phosphate, however, did not result in the appearance of tripolyphosphate in {sup 31}P-NMR spectra of cells adapted to high (>1.5 molar NaCl) salinities.

  11. Multidimensional spatial-spectral holographic interpretation of NMR photography

    NASA Astrophysics Data System (ADS)

    Kiruluta, Andrew J. M.

    2006-05-01

    A spectral holographic interpretation arises naturally in nuclear magnetic resonance (NMR) photography from either the intrinsic chemical shift anisotropy of the spin system or the field inhomogeneity due to the applied spatial encoding gradients. We can thus think of NMR photography as arising from a "diffraction" off a spatial-spectral holographic grating. The spatial holographic component arises from a high dielectric constant (>50) of the NMR medium at high field strength (>4T) when the excitation wavelength is commensurate with the size of the NMR sample; otherwise, it is a volume spectral holographic grating. In this paper, the NMR localized spectroscopy (imaging) equation is derived from the principles of spatial-spectral holography. Holographic properties of storage and programmable time delay and time reversal are shown to follow naturally from this viewpoint and are experimentally demonstrated in an inhomogeneously broadened NMR sample. These ideas are shown to be extendable to complex signal processing functions such as recognition, correlations, and triple products.

  12. Luminescence dynamics and {sup 13}C NMR characteristics of dinuclear complexes exhibiting coupled lanthanide(III) cation pairs

    SciTech Connect

    Matthews, K.D.; Bailey-Folkes, S.A.; Kahwa, I.A. [Univ. of the West Indies, Mona, Kingston (Jamaica)] [and others

    1992-08-20

    Luminescence and cross-polarization magic angle spinning (CP-MAS) {sup 13}C NMR properties of lanthanide dinuclear macrocyclic complexes of a compartmental Schiff base chelate (1) derived from the condensation of 2,6-diformyl-p-cresol and 3,6-dioxa-1,8-octanediamine are reported. The Schiff base chromophore in 1 is a strong light absorber and an efficient sensitizer for intense Tb{sup 3+}({sup 5}D{sub 4}) and Eu{sup 3+}({sup 5}D{sub 0})(T < 110 K ) emission which does not exhibit self-quenching effects. Emission from Tb{sup 3+} is sensitized by the ligand singlet state; in striking contrast, Eu{sup 3+} emission is sensitized by the triplet state and reveals an unusual nonradiative quenching process at T > 110 K with a thermal barrier of {approx} 2300 cm{sup {minus}1}. Weak emission is observed from Dy{sup 3+}({sup 4}F{sub 9/2}), Sm{sup 3+}({sup 4}G{sub 5/2}), and Pr{sup 3+}({sup 1}D{sub 2}) diluted in Gd{sup 3+} (i.e., from Gd{sup 3+}-Ln{sup 3+} heteropairs, Ln = Pr, Sm, Dy). Intramolecular metal-metal (Ln-Ln = 4 {Angstrom}) interactions account for the greatly quenched emission from Sm{sup 3+}-Sm{sup 3+} and Dy{sup 3+}-Dy{sup 3+} homopairs compared to Gd{sup 3+}-Ln heteropairs (Ln = Sm, Dy). Gd{sup 3+}-Ln{sup 3+} emission lifetimes at 77 K are 1610 (Tb{sup 3+}), 890 (Eu{sup 3+}), 14 (Dy{sup 3+}) and {approx} 13 {mu}s (Sm{sup 3+}). Nonradiative relaxation processes at 77 K in dilute Ln{sup 3+}:Gd{sub 2}1(NO{sub 3}){sub 4}{center_dot}H{sub 2}O, being temperature independent for Sm{sup 3+} and Eu{sup 3+} but temperature dependent for Tb{sup 3+}, follow the energy gap law with {alpha} {approx} - 10{sup {minus}3} cm and B {approx} 2 x 10{sup 8} s{sup {minus}1}. CP-MAS data show paramagnetic broadening of {sup 13}C resonances which increases with the magnetic moment of Ln{sup 3+}. Surprisingly, no significant shifts in resonance positions corresponding to the changing nature of paramagnetic Ln{sup 3+} ions are observed. 43 refs., 8 figs., 2 tabs.

  13. Synthesis of D-[U-{sup 13}C]Glucal, D-[U-{sup 13}C] Galactal, and L-[U-{sup 13}C]Fucose for NMR structure studies of oligosaccharides

    SciTech Connect

    Wu, R.; Unkefer, C.J.; Silks, L.A. III [Los Alamos National Lab., NM (United States)

    1996-12-31

    The role of carbohydrates is well recognized in a variety of important biological phenomena such as cell surface recognition. Recent advances in carbohydrate chemistry, including the development of solid phase synthesis methods, have helped to provide significant quantities of material by offering general protocols for synthesis of well-defined, pure material. However, the study of the solution structure of oligosaccharides by nuclear magnetic resonance techniques have been hampered by the lack of enriched {sup 13}C material. In an effort to help alleviate this situation, we have been interested in the construction of the title compounds from a single economical carbon source, D-[U-{sup 13}C]glucose. Details of the syntheses will be provided.

  14. A new Schiff base compound N,N'-(2,2-dimetylpropane)-bis(dihydroxylacetophenone): synthesis, experimental and theoretical studies on its crystal structure, FTIR, UV-visible, 1H NMR and 13C NMR spectra.

    PubMed

    Saheb, Vahid; Sheikhshoaie, Iran

    2011-10-15

    The Schiff base compound, N,N'-(2,2-dimetylpropane)-bis(dihydroxylacetophenone) (NDHA) is synthesized through the condensation of 2-hydroxylacetophenone and 2,2-dimethyl 1,3-amino propane in methanol at ambient temperature. The yellow crystalline precipitate is used for X-ray single-crystal determination and measuring Fourier transform infrared (FTIR), UV-visible, (1)H NMR and (13)C NMR spectra. Electronic structure calculations at the B3LYP, PBEPBE and PW91PW91 levels of theory are performed to optimize the molecular geometry and to calculate the FTIR, (1)H NMR and (13)C NMR spectra of the compound. Time-dependent density functional theory (TDDFT) method is used to calculate the UV-visible spectrum of NDHA. Vibrational frequencies are determined experimentally and compared with those obtained theoretically. Vibrational assignments and analysis of the fundamental modes of the compound are also performed. All theoretical methods can well reproduce the structure of the compound. The (1)H NMR and (13)C NMR chemical shifts calculated by all DFT methods are consistent with the experimental data. However, the NMR shielding tensors computed at the B3LYP/6-31+G(d,p) level of theory are in better agreement with experimental (1)H NMR and (13)C NMR spectra. The electronic absorption spectrum calculated at the B3LYP/6-31+G(d,p) level by using TD-DFT method is in accordance with the observed UV-visible spectrum of NDHA. In addition, some quantum descriptors of the molecule are calculated and conformational analysis is performed and the results were compared with the crystallographic data. PMID:21763188

  15. Soil organic degradation: bridging the gap between Rock-Eval pyrolysis and chemical characterization (CPMAS 13C NMR)

    NASA Astrophysics Data System (ADS)

    Albrecht, Remy; Sebag, David; Verrecchia, Eric

    2013-04-01

    Being a source of mineral nutrients, organic matter contributes to soil chemical fertility and acts on soil physical fertility through its role in soil structure. Soil organic matter (SOM) is a key component of soils. Despite the paramount importance of SOM, information on its chemistry and behaviour in soils is incomplete. Numerous methods are used to characterize and monitor OM dynamics in soils using different approaches (Kogel-Knabner, 2000). Two of the main approaches are evaluated and compared in this study. Rock-Eval pyrolysis (RE pyrolysis) provides a description of a SOM's general evolution using its thermal resistance. The second tool (13C CPMAS NMR) aims to give precise and accurate chemical information on OM characterization. The RE pyrolysis technique was designed for petroleum exploration (Lafargue et al., 1998) and because of its simplicity, it has been applied to a variety of other materials such as soils or Recent sediments (Disnar et al., 2000; Sebag, 2006). Recently, RE pyrolysis became a conventional tool to study OM dynamics in soils. In RE pyrolysis, a peak deconvolution is applied to the pyrolysis signal in order to get four main components related to major classes of organic constituents. These components differ in origin and resistance to pyrolysis: labile biological constituents (F1), resistant biological constituents (F2), immature non-biotic constituents (F3) and a mature refractory fraction (F4) (Sebag, 2006; Coppard, 2006). Main advantages of the technique are its repeatability, and rapidity to provide an overview of OM properties and stocks. However, do the four major classes used in the literature reflect a pertinent chemical counterpart? To answer this question, we used 13C Nuclear Magnetic Resonance Spectroscopy in the solid state (13C CPMAS NMR) to collect direct information on structural and conformational characteristics of OM. NMR resonances were assigned to chemical structures according to five dominant forms: alkyl C, O-alkyl C, aromatic C and phenolic C and carbonyl-carboxyl C. Moreover, in order to avoid the influence of pedogenesis, we decided to use "less complex OM", i.e. compost samples. The choice to use compost samples has been dictated by the fact that i) composting processes are well described and referenced in the literature, and ii) these samples have already been studied previously (Albrecht, 2009). Significantly high correlations are observed between classes, or indices, from RE pyrolysis and main classes of organic matter detected by NMR e.g. F1 and labile / easily degradable components (alkyl C et O-alkyl C); F3/F4 and humified OM (aromatic C and phenolic C); R index (contributions of bio-macromolecules) and phenolic and aromatic C; I index (related to immature OM) and labile / easily degradable components (alkyl C et O-alkyl C). This work confirms the interest of RE pyrolysis in soil science (notably by using the R/I index ratio). Compost was an ideal model with a clear chronological evolution of organic matter. The next step consists of using more complex samples such as bulk soil samples. REFERENCES Albrecht, R., Joffre, R., Le Petit, J., Terrom, G., Périssol, C. 2009. Calibration of Chemical and Biological Changes in Cocomposting of Biowastes Using Near-Infrared Spectroscopy. Environmental Science & Technology, 43(3), 804-811. Copard, Y., Di-Govanni, C., Martaud, T., Alberic, P., Olivier, J.E. 2006. Using Rock-Eval 6 pyrolysis for tracking fossil organic carbon in modern environments: implications for the roles of erosion and weathering. Earth Surface Processes and Landforms, 31(2), 135-153. Disnar, J.R., Guillet, B., Keravis, D., Di-Giovanni, C., Sebag, D. 2003. Soil organic matter (SOM) characterization by Rock-Eval pyrolysis: scope and limitations. Organic Geochemistry, 34(3), 327-343. Kogel-Knabner, I. 2000. Analytical approaches for characterizing soil organic matter. Organic Geochemistry, 31(7-8), 609-625. Lafargue, E., Marquis, F., Pillot, D. 1998. Rock-Eval 6 applications in hydrocarbon exploration, production, and soil contamination studi

  16. 13C NMR studies of methylene and methine carbons of substrate bound to a 280,000-dalton protein, porphobilinogen synthase.

    PubMed

    Jaffe, E K; Markham, G D

    1988-06-14

    13C NMR has been used to observe the equilibrium complex of [5,5-2H,5-13C]-5-aminolevulinate [( 5,5-2H,5-13C]ALA) bound to porphobilinogen (PBG) synthase (5-aminolevulinate dehydratase), a 280,000-dalton protein. [5,5-2H,5-13C]ALA (chemical shift 46.9 ppm in D2O) was prepared from [5-13C]ALA through enolization in deuteriated neutral potassium phosphate buffer. In the PBG synthase reaction [5,5-2H,5-13C]ALA forms [2,11,11-2H,2,11-13C]PBG (chemical shifts 116.2 ppm for C2 and 34.2 ppm for C11 in D2O). For the complex formed between [5,5-2H,5-13C]ALA and methyl methanethiosulfonate (MMTS) modified PBG synthase, which does not catalyze PBG formation but can form a Schiff base adduct, the chemical shift of 44.2 ppm (line width 92 Hz) identifies an imine structure as the predominant tautomeric form of the Schiff base. By comparison to model compounds, the stereochemistry of the imine has been deduced; however, the protonation state of the imine nitrogen remains unresolved. Reconstitution of the MMTS-modified enzyme-Schiff base complex with Zn(II) and 2-mercaptoethanol results in the holoenzyme-bound equilibrium complex; this complex contains predominantly enzyme-bound PBG, and spectra reveal two peaks from bound PBG and two from free PBG. For bound PBG, C2 is -2.8 ppm from the free signal and C11 is +2.6 ppm from the free signal; the line widths of the bound signals are 55 and 75 Hz, respectively.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3166990

  17. A straightforward method for stereospecific assignment of val and leu prochiral methyl groups by solid-state NMR: Scrambling in the [2-13C]Glucose labeling scheme

    NASA Astrophysics Data System (ADS)

    Lv, Guohua; Faßhuber, Hannes Klaus; Loquet, Antoine; Demers, Jean-Philippe; Vijayan, Vinesh; Giller, Karin; Becker, Stefan; Lange, Adam

    2013-03-01

    The unambiguous stereospecific assignment of the prochiral methyl groups in Val and Leu plays an important role in the structural investigation of proteins by NMR. Here, we present a straightforward method for their stereospecific solid-state NMR assignment based on [2-13C]Glucose ([2-13C]Glc) as the sole carbon source during protein expression. The approach is fundamentally based on the stereo-selective biosynthetic pathway of Val and Leu, and the co-presence of [2-13C]pyruvate produced mainly by glycolysis and [3-13C]/[1,3-13C]pyruvate most probably formed through scrambling in the pentose phosphate pathway. As a consequence, the isotope spin pairs 13C?-13C?2 and 13C?-13C?1 in Val, and 13C?-13C?2 and 13C?-13C?1 in Leu are obtained. The approach is successfully demonstrated with the stereospecific assignment of the methyl groups of Val and Leu of type 3 secretion system PrgI needles and microcrystalline ubiquitin.

  18. Interaction between a recombinant prion protein and organo-mineral complexes as evidenced by CPMAS 13C-NMR

    NASA Astrophysics Data System (ADS)

    Russo, F.; Scotti, R.; Gianfreda, L.; Conte, P.; Rao, M. A.

    2009-04-01

    Prion proteins (PrP) are the main responsible for Transmissible Spongiform Encephalopathies (TSE). The TSE etiological agent is a misfolded form of the normal cellular prion protein. The amyloidal aggregates accumulated in the brain of infected animals and mainly composed of PrPSc exhibit resistance to protease attack and many conventional inactivating procedures. The prion protein diseases cause an environmental issue because the environment and in particular the soil compartment can be contaminated and then become a potential reservoir and diffuser of TSEs infectivity as a consequence of (i) accidental dispersion from storage plants of meat and bone meal, (ii) incorporation of contaminated material in fertilizers, (iii) possible natural contamination of pasture soils by grazing herds, and (v) burial of carcasses. The environmental problem can be even more relevant because very low amounts of PrPSc are able to propagate the disease. Several studies evidenced that infectious prion protein remains active in soils for years. Contaminated soils result, thus, a possible critical route of TSE transmission in wild animals. Soil can also protect prion protein toward degradation processes due to the presence of humic substances and inorganic components such as clays. Mineral and organic colloids and the more common association between clay minerals and humic substances can contribute to the adsorption/entrapment of molecules and macromolecules. The polymerization of organic monomeric humic precursors occurring in soil in the presence of oxidative enzymes or manganese and iron oxides, is considered one of the most important processes contributing to the formation of humic substances. The process is very fast and produces a population of polymeric products of different molecular structures, sizes, shapes and complexity. Other molecules and possibly biomacromolecules such as proteins may be involved. The aim of the present work was to study by CPMAS 13C-NMR the interactions between a non pathogenic ovine recombinant prion protein and a model soil system represented by a manganese oxide in the form of birnessite (?-MnO2), coated with a polymerized catechol. To better understand the effect of the polymerization process, PrP was added to the birnessite-cathecol system either before or after the polymerization processes. The NMR spectra of the prion protein interacting directly with birnessite revealed disappearance of the signals due to the paramagnetic nature of manganese oxide or abiotic degradation. Conversely, the signal pattern of the protein re-appeared as it is mixed to the soil-like system either during or after the catechol polymerization process. Results suggested that the possible interactions of the prion protein on soil systems can be mediated by natural organic matter. However, deeper studies on more complex real soil systems are needed to definitely confirm such hypothesis.

  19. Density functional investigation of intermolecular effects on {sup 13}C NMR chemical-shielding tensors modeled with molecular clusters

    SciTech Connect

    Holmes, Sean T.; Dybowski, Cecil [Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 (United States); Iuliucci, Robbie J. [Department of Chemistry, Washington and Jefferson College, Washington, Pennsylvania 15301 (United States); Mueller, Karl T. [Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)

    2014-10-28

    A quantum-chemical method for modeling solid-state nuclear magnetic resonance chemical-shift tensors by calculations on large symmetry-adapted clusters of molecules is demonstrated. Four hundred sixty five principal components of the {sup 13}C chemical-shielding tensors of 24 organic materials are analyzed. The comparison of calculations on isolated molecules with molecules in clusters demonstrates that intermolecular effects can be successfully modeled using a cluster that represents a local portion of the lattice structure, without the need to use periodic-boundary conditions (PBCs). The accuracy of calculations which model the solid state using a cluster rivals the accuracy of calculations which model the solid state using PBCs, provided the cluster preserves the symmetry properties of the crystalline space group. The size and symmetry conditions that the model cluster must satisfy to obtain significant agreement with experimental chemical-shift values are discussed. The symmetry constraints described in the paper provide a systematic approach for incorporating intermolecular effects into chemical-shielding calculations performed at a level of theory that is more advanced than the generalized gradient approximation. Specifically, NMR parameters are calculated using the hybrid exchange-correlation functional B3PW91, which is not available in periodic codes. Calculations on structures of four molecules refined with density plane waves yield chemical-shielding values that are essentially in agreement with calculations on clusters where only the hydrogen sites are optimized and are used to provide insight into the inherent sensitivity of chemical shielding to lattice structure, including the role of rovibrational effects.

  20. Alkaline Hydrolysis/Polymerization of 2,4,6-Trinitrotoluene: Characterization of Products by 13C and 15N NMR

    USGS Publications Warehouse

    Thorn, K.A.; Thorne, P.G.; Cox, L.G.

    2004-01-01

    Alkaline hydrolysis has been investigated as a nonbiological procedure for the destruction of 2,4,6-trinitrotoluene (TNT) in explosives contaminated soils and munitions scrap. Nucleophilic substitutions of the nitro and methyl groups of TNT by hydroxide ion are the initial steps in the alkaline degradation of TNT. Potential applications of the technique include both in situ surface liming and ex situ alkaline treatment of contaminated soils. A number of laboratory studies have reported the formation of an uncharacterized polymeric material upon prolonged treatment of TNT in base. As part of an overall assessment of alkaline hydrolysis as a remediation technique, and to gain a better understanding of the chemical reactions underlying the hydrolysis/polymerization process, the soluble and precipitate fractions of polymeric material produced from the calcium hydroxide hydrolysis of unlabeled and 15N-labeled TNT were analyzed by elemental analysis and 13C and 15N nuclear magnetic resonance spectroscopy. Spectra indicated that reactions leading to polymerization included nucleophilic displacement of nitro groups by hydroxide ion, formation of ketone, carboxyl, alcohol, ether, and other aliphatic carbons, conversion of methyl groups to diphenyl methylene carbons, and recondensation of aromatic amines and reduced forms of nitrite, including ammonia and possibly hydroxylamine, into the polymer. Compared to the distribution of carbons in TNT as 14% sp 3- and 86% sp2-hybridized, the precipitate fraction from hydrolysis of unlabeled TNT contained 33% sp3- and 67% sp 2-hybridized carbons. The concentration of nitrogen in the precipitate was 64% of that in TNT. The 15N NMR spectra showed that, in addition to residual nitro groups, forms of nitrogen present in the filtrate and precipitate fractions include aminohydroquinone, primary amide, indole, imine, and azoxy, among others. Unreacted nitrite was recovered in the filtrate fraction. The toxicities and susceptibilities to microbial or chemical degradation of the polymeric materials remain unknown.

  1. Computational identification of a phospholipidosis toxicophore using (13)C and (15)N NMR-distance based fingerprints.

    PubMed

    Slavov, Svetoslav H; Wilkes, Jon G; Buzatu, Dan A; Kruhlak, Naomi L; Willard, James M; Hanig, Joseph P; Beger, Richard D

    2014-12-01

    Modified 3D-SDAR fingerprints combining (13)C and (15)N NMR chemical shifts augmented with inter-atomic distances were used to model the potential of chemicals to induce phospholipidosis (PLD). A curated dataset of 328 compounds (some of which were cationic amphiphilic drugs) was used to generate 3D-QSDAR models based on tessellations of the 3D-SDAR space with grids of different density. Composite PLS models averaging the aggregated predictions from 100 fully randomized individual models were generated. On each of the 100 runs, the activities of an external blind test set comprised of 294 proprietary chemicals were predicted and averaged to provide composite estimates of their PLD-inducing potentials (PLD+ if PLD is observed, otherwise PLD-). The best performing 3D-QSDAR model utilized a grid with a density of 8ppm×8ppm in the C-C region, 8ppm×20ppm in the C-N region and 20ppm×20ppm in the N-N region. The classification predictive performance parameters of this model evaluated on the basis of the external test set were as follows: accuracy=0.70, sensitivity=0.73 and specificity=0.66. A projection of the most frequently occurring bins on the standard coordinate space suggested a toxicophore composed of an aromatic ring with a centroid 3.5-7.5Å distant from an amino-group. The presence of a second aromatic ring separated by a 4-5Å spacer from the first ring and at a distance of between 5.5Å and 7Å from the amino-group was also associated with a PLD+ effect. These models provide comparable predictive performance to previously reported models for PLD with the added benefit of being based entirely on non-confidential, publicly available training data and with good predictive performance when tested in a rigorous, external validation exercise. PMID:25228124

  2. Density functional investigation of intermolecular effects on 13C NMR chemical-shielding tensors modeled with molecular clusters

    NASA Astrophysics Data System (ADS)

    Holmes, Sean T.; Iuliucci, Robbie J.; Mueller, Karl T.; Dybowski, Cecil

    2014-10-01

    A quantum-chemical method for modeling solid-state nuclear magnetic resonance chemical-shift tensors by calculations on large symmetry-adapted clusters of molecules is demonstrated. Four hundred sixty five principal components of the 13C chemical-shielding tensors of 24 organic materials are analyzed. The comparison of calculations on isolated molecules with molecules in clusters demonstrates that intermolecular effects can be successfully modeled using a cluster that represents a local portion of the lattice structure, without the need to use periodic-boundary conditions (PBCs). The accuracy of calculations which model the solid state using a cluster rivals the accuracy of calculations which model the solid state using PBCs, provided the cluster preserves the symmetry properties of the crystalline space group. The size and symmetry conditions that the model cluster must satisfy to obtain significant agreement with experimental chemical-shift values are discussed. The symmetry constraints described in the paper provide a systematic approach for incorporating intermolecular effects into chemical-shielding calculations performed at a level of theory that is more advanced than the generalized gradient approximation. Specifically, NMR parameters are calculated using the hybrid exchange-correlation functional B3PW91, which is not available in periodic codes. Calculations on structures of four molecules refined with density plane waves yield chemical-shielding values that are essentially in agreement with calculations on clusters where only the hydrogen sites are optimized and are used to provide insight into the inherent sensitivity of chemical shielding to lattice structure, including the role of rovibrational effects.

  3. Major Groove Width Variations in RNA Structures Determined by NMR and Impact of 13C residual chemical shift anisotropy and 1H-13C residual dipolar coupling on refinement

    PubMed Central

    Tolbert, Blanton S; Miyazaki, Yasuyuki; Barton, Shawn; Kinde, Benyam; Starck, Patrice; Singh, Rashmi; Bax, Ad

    2010-01-01

    Ribonucleic acid structure determination by NMR spectroscopy relies primarily on local structural restraints provided by 1H-1H NOEs and J-couplings. When employed loosely, these restraints are broadly compatible with A- and B-like helical geometries and give rise to calculated structures that are highly sensitive to the force fields employed during refinement. A survey of recently reported NMR structures reveals significant variations in helical parameters, particularly the major groove width. Although helical parameters observed in high-resolution X-ray crystal structures of isolated A-form RNA helices are sensitive to crystal packing effects, variations among the published X-ray structures are significantly smaller than those observed in NMR structures. Here we show that restraints derived from aromatic 1H-13C residual dipolar couplings (RDCs) and residual chemical shift anisotropies (RCSAs) can overcome NMR restraint and force field deficiencies and afford structures with helical properties similar to those observed in high-resolution X-ray structures. PMID:20549304

  4. Structural investigation of Titan tholins by solution-state 1H, 13C, and 15N NMR: one-dimensional and decoupling experiments.

    PubMed

    He, Chao; Lin, Guangxin; Upton, Kathleen T; Imanaka, Hiroshi; Smith, Mark A

    2012-05-17

    Titan, the largest moon of Saturn, is enveloped in a reddish brown organic haze. Titan haze is presumed to be formed from methane and nitrogen (CH(4) and N(2)) in Titan's upper atmosphere through energetic photochemistry and particle bombardment. Though Titan haze has been directly investigated using methods including the Cassini mission, its formation mechanism and the contributing chemical structures and prebiotic potential are still not well developed. We report here the structural investigation of the (13)C and (15)N labeled, simulated Titan haze aerosol (tholin) by solution-state NMR. The one-dimensional (1)H, (13)C, and (15)N NMR spectra and decoupling experiments indicate that the tholin sample contains amine, nitrile, imine, and N-heteroaromatic compounds of tremendous import in understanding complex organic chemistry in anaerobic, extraterrestrial environments. PMID:22489539

  5. Mechanism of formation of humus coatings on mineral surfaces 3. Composition of adsorbed organic acids from compost leachate on alumina by solid-state 13C NMR

    USGS Publications Warehouse

    Wershaw, R.L.; Llaguno, E.C.; Leenheer, J.A.

    1996-01-01

    The adsorption of compost leachate DOC on alumina is used as a model for elucidation of the mechanism of formation of natural organic coatings on hydrous metal oxide surfaces in soils and sediments. Compost leachate DOC is composed mainly of organic acid molecules. The solid-state 13C NMR spectra of these organic acids indicate that they are very similar in composition to aquatic humic substances. Changes in the solid-state 13C NMR spectra of compost leachate DOC fractions adsorbed on alumina indicate that the DOC molecules are most likely adsorbed on metal oxide surfaces through a combination of polar and hydrophobic interaction mechanisms. This combination of polar and hydrophobic mechanism leads to the formation of bilayer coatings of the leachate molecules on the oxide surfaces.

  6. CP-MAS 13C NMR and FT-IR investigation of the degradation reactions of polymer constituents in wood welding

    Microsoft Academic Search

    L. Delmotte; C. Ganne-Chedeville; J. M. Leban; A. Pizzi; F. Pichelin

    2008-01-01

    The essential chemical modifications involving the polymeric constituents of wood in friction welding occur in the first 5–6s slowing down or even stopping afterwards. FT-IR and CP-MAS 13C NMR of the welded area of wood have shown dehydration and an apparent increase in the crystallinity of cellulose. A certain level of hemicelluloses degradation occurs, accompanied by the generation of some

  7. GlyNest and CASPER: two independent approaches to estimate 1H and 13C NMR shifts of glycans available through a common web-interface

    Microsoft Academic Search

    Alexander Loß; Roland Stenutz; Eberhard Schwarzer; Claus-wilhelm Von Der Lieth

    2006-01-01

    GlyNest and CASPER (www.casper.organ.su.se\\/ casper\\/) are two independent services aiming to predict 1H- and 13C-NMR chemical shifts of glycans. GlyNest estimates chemical shifts of glycans based on a spherical environment encoding scheme for each atom. CASPER is an increment rule-based approach which uses chemical shifts of the free reducing monosaccharides which are altered according to attached residues of an oligo-

  8. Conjugation effects. 27. Analysis of the 13 C NMR spectra and SK ? X-ray fluorescence spectra of 1-alkylthio-2,4,6-trimethylbenzenes

    Microsoft Academic Search

    G. N. Dolenko; V. M. Bzhezovskii; I. A. Aliev

    1988-01-01

    1.There is virtually no p, it-interaction of the sulfur atom with the aromatic ring in sterically hindered 1-alkylthio-2,4,6-trimethylbenzene due to the close-to-orthogonal effective conformation of these molecules.2.The occupancy of the close-to-planar conformation in 1-alkylthio-4-methylbenzenes decreases with increasing bulk of the -SAlk groups, while the occupancy of the nonplanar conformer increases. As a consequence, the13C NMR spectra display changes related to

  9. 1H, 13C NMR studies and GIAO/DFT calculations of substituted N-(4-aryl-1-piperazinylbutyl) derivatives, new analogues of buspirone

    NASA Astrophysics Data System (ADS)

    Pisklak, Maciej; Kossakowski, Jerzy; Perli?ski, Miros?aw; Wawer, Iwona

    2004-07-01

    13C cross-polarisation (CP) magic angle spinning (MAS) NMR data are reported for seven piperazinylbutyl derivatives of 1,4-dichloro-dibenzo[ e, h]bicyclo[2,2,3]octane-2,3-dicarboimide, new analogues of buspirone (anxiolytic drug). The assignment of solid state 13C NMR spectra were made with an aid of variable contact time experiments, as well as by comparison with solution data and calculated shielding constants. 13C CPMAS NMR spectra showed a disorder of methylene carbons in solids of 1- 7, in 1 and 3 two molecules differing in conformation of n-butyl chain are probably present in the asymmetric unit cell. In CDCl 3 solution, the barrier to piperazine ring inversion is 50 kJ/mol for 2, and lower than 46 kJ/mol for 1 and 3. Satisfactory agreement between the experimental chemical shifts (both in solution and solid state) and theoretical values of shielding constants (calculated by GIAO/DFT and GIAO/HF methods) was obtained (correlation coefficients R2>0.98).

  10. One-azabicyclic compounds. 22. Stereochemistry and /sup 13/C NMR spectra of salts of pyrrolizidine and its homologs with protonic acids

    SciTech Connect

    Subbotin, O.A.; Skvortsov, I.M.

    1986-06-01

    /sup 13/C NMR spectra were obtained for pyrrolizidinium salts and their homologs and their signals were assigned. With the exception of highly strained cis-3,8-H-cis-5,8-H-3,5-dimethylpyrrolizidine (VI), all the bases studied upon their direct mixing with CF/sub 3/CO/sub 2/H form salts only with cis-fused rings in the cation. Mixtures of salts with cis- and trans-fused pyrrolizidinium fragments are formed upon the reaction of cis-3,8-H-methyl- (III) and cis-3,8-H-cis-5,8-H-3,5-dimethylpyrrolizidine (VI) under conditions close to those for kinetically-controlled amine protonation. The /sup 13/C NMR spectra of the isomeric pyrrolizidinium salts obtained as a result of the absorption of base VI by sulfuric acid were used to evaluate the conformational equilibrium in the starting compound VI. The /sup 13/C NMR chemical shifts of unsubstituted trans-fused pyrrolizidinium salts were predicted.

  11. Bioreaction Network Topology and Metabolic Flux Ratio Analysis by Biosynthetic Fractional 13C Labeling and Two-Dimensional NMR Spectroscopy

    Microsoft Academic Search

    Thomas Szyperski; Ralf W. Glaser; Michel Hochuli; Jocelyne Fiaux; Uwe Sauer; James E. Bailey; Kurt Wüthrich

    1999-01-01

    Biosynthetically directed fractional 13C labeling of the proteinogenic amino acids is achieved by feeding a mixture of uniformly 13C-labeled and unlabeled carbon source compounds into a bioreaction network. Analysis of the resulting labeling pattern enables both a comprehensive characterization of the network topology and the determination of metabolic flux ratios. Attractive features with regard to routine applications are (i) an

  12. Rapid adaptation of rat brain and liver metabolism to a ketogenic diet: an integrated study using (1)H- and (13)C-NMR spectroscopy.

    PubMed

    Roy, Maggie; Beauvieux, Marie-Christine; Naulin, Jérôme; El Hamrani, Dounia; Gallis, Jean-Louis; Cunnane, Stephen C; Bouzier-Sore, Anne-Karine

    2015-07-01

    The ketogenic diet (KD) is an effective alternative treatment for refractory epilepsy in children, but the mechanisms by which it reduces seizures are poorly understood. To investigate how the KD modifies brain metabolism, we infused control (CT) and 7-day KD rats with either [1-(13)C]glucose (Glc) or [2,4-(13)C2]?-hydroxybutyrate (?-HB). Specific enrichments of amino acids (AAs) measured by (1)H- and (13)C-NMR in total brain perchloric acid extracts were similar between CT and KD rats after [1-(13)C]Glc infusion whereas they were higher in KD rats after [2,4-(13)C2]?-HB infusion. This suggests better metabolic efficiency of ketone body utilization on the KD. The relative rapid metabolic adaptation to the KD included (1) 11%-higher brain ?-amino butyric acid (GABA)/glutamate (Glu) ratio versus CT, (2) liver accumulation of the ketogenic branched-chain AAs (BCAAs) leucine (Leu) and isoleucine (ILeu), which were never detected in CT, and (3) higher brain Leu and ILeu contents. Since Glu and GABA are excitatory and inhibitory neurotransmitters, respectively, higher brain GABA/Glu ratio could contribute to the mechanism by which the KD reduces seizures in epilepsy. Increased BCAA on the KD may also contribute to better seizure control. PMID:25785828

  13. Chemical and nanometer-scale structure of kerogen and its change during thermal maturation investigated by advanced solid-state 13C NMR spectroscopy

    USGS Publications Warehouse

    Mao, J.; Fang, X.; Lan, Y.; Schimmelmann, A.; Mastalerz, Maria; Xu, L.; Schmidt-Rohr, K.

    2010-01-01

    We have used advanced and quantitative solid-state nuclear magnetic resonance (NMR) techniques to investigate structural changes in a series of type II kerogen samples from the New Albany Shale across a range of maturity (vitrinite reflectance R0 from 0.29% to 1.27%). Specific functional groups such as CH3, CH2, alkyl CH, aromatic CH, aromatic C-O, and other nonprotonated aromatics, as well as "oil prone" and "gas prone" carbons, have been quantified by 13C NMR; atomic H/C and O/C ratios calculated from the NMR data agree with elemental analysis. Relationships between NMR structural parameters and vitrinite reflectance, a proxy for thermal maturity, were evaluated. The aromatic cluster size is probed in terms of the fraction of aromatic carbons that are protonated (???30%) and the average distance of aromatic C from the nearest protons in long-range H-C dephasing, both of which do not increase much with maturation, in spite of a great increase in aromaticity. The aromatic clusters in the most mature sample consist of ???30 carbons, and of ???20 carbons in the least mature samples. Proof of many links between alkyl chains and aromatic rings is provided by short-range and long-range 1H-13C correlation NMR. The alkyl segments provide most H in the samples; even at a carbon aromaticity of 83%, the fraction of aromatic H is only 38%. While aromaticity increases with thermal maturity, most other NMR structural parameters, including the aromatic C-O fractions, decrease. Aromaticity is confirmed as an excellent NMR structural parameter for assessing thermal maturity. In this series of samples, thermal maturation mostly increases aromaticity by reducing the length of the alkyl chains attached to the aromatic cores, not by pronounced growth of the size of the fused aromatic ring clusters. ?? 2010 Elsevier Ltd. All rights reserved.

  14. 13C n.m.r. isotopomer and computer-simulation studies of the non-oxidative pentose phosphate pathway of human erythrocytes.

    PubMed Central

    Berthon, H A; Bubb, W A; Kuchel, P W

    1993-01-01

    13C double-quantum filtered correlation spectroscopy (DQF-COSY) provides a novel method for the detection of reactions involving carbon-bond scissions. We report the use of this technique to investigate isotopic exchange reactions of the non-oxidative pentose phosphate pathway in human erythrocytes. These exchange reactions resulted in the formation of a range of isotopic isomers (isotopomers) of glucose 6-phosphate after incubation of a mixture of universally 13C-labelled and unlabelled glucose 6-phosphate with fructose 1,6-bisphosphate and haemolysates. These isotopomers were detected in the coupling patterns of cross-peaks within the DQF-COSY spectrum of the deproteinized sample. A computer model which fully describes the reactions of the non-oxidative pentose phosphate pathway in human erythrocytes has previously been constructed and tested with 31P n.m.r. time-course data in our laboratory. This model was refined using 13C n.m.r. time-course data and extended to include the range of isotopomers which may be formed experimentally by the reactions of the non-oxidative pentose phosphate pathway. The isotopomer ratios obtained experimentally from the DQF-COSY spectrum were consistent with simulations generated by this model. PMID:8257428

  15. Recoupling of chemical shift anisotropies in solid-state NMR under high-speed magic-angle spinning and in uniformly 13C-labeled systems

    NASA Astrophysics Data System (ADS)

    Chan, Jerry C. C.; Tycko, Robert

    2003-05-01

    We demonstrate the possibility of recoupling chemical shift anisotropy (CSA) interactions in solid-state nuclear magnetic resonance (NMR) under high-speed magic-angle spinning (MAS) while retaining a static CSA powder pattern line shape and simultaneously attenuating homonuclear dipole-dipole interactions. CSA recoupling is accomplished by a rotation-synchronized radio-frequency pulse sequence with symmetry properties that permit static CSA line shapes to be obtained. We suggest a specific recoupling sequence, which we call ROCSA, for which the scaling factors for CSA and homonuclear dipole-dipole interactions are 0.272 and approximately 0.05, respectively. This sequence is suitable for high-speed 13C MAS NMR experiments on uniformly 13C-labeled organic compounds, including biopolymers. We demonstrate the ROCSA sequence experimentally by measuring the 13C CSA patterns of the uniformly labeled, polycrystalline compounds L-alanine and N-acetyl-D,L-valine at MAS frequencies of 11 and 20 kHz. We also present experimental data for amyloid fibrils formed by a 15-residue fragment of the ?-amyloid peptide associated with Alzheimer's disease, in which four amino acid residues are uniformly labeled, demonstrating the applicability to biochemical systems of high molecular weight and significant complexity. Analysis of the CSA patterns in the amyloid fibril sample demonstrates the utility of ROCSA measurements as probes of peptide and protein conformation in noncrystalline solids.

  16. The conformational stability, solvation and the assignments of the experimental infrared, Raman, 1H and 13C NMR spectra of the local anesthetic drug lidocaine

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.; Förner, Wolfgang; Ali, Shaikh A.

    2015-05-01

    The structure, vibrational and 1H and 13C NMR spectra of the local anesthetic drug lidocaine were investigated by the B3LYP/6-311G?? calculations. The molecule was predicted to have the non-planar cis (NCCN ? 0°) structures being about 2-6 kcal/mol lower in energy than the corresponding trans (NCCN ? 180°) forms. The calculated NCCN (9.6°) and CNCC (-132.2°) torsional angles were in a good qualitative agreement with the reported X-ray angles (3.1 and 13.0°, -102.67 and -77.9°, respectively, for H-bonded dimers). The Gibbs energy of solution of lidocaine in formamide, water, dimethylsulfoxide, acetonitrile, methanol, ethanol and chloroform solutions was estimated at the B3LYP level. The predicted affinity of lidocaine toward the alcohols, acetonitrile and chloroform solutions was in excellent agreement with the reported experimental solubility of the drug in organic solvents. The analysis of the observed vibrational spectra is consistent with the presence of lidocaine in only one conformation at room temperature. The 1H and 13C NMR spectra of lidocaine were interpreted by experimental and DFT calculated chemical shifts of the drug. The RMSD between experimental and theoretical 1H and 13C chemical shifts for lidocaine is 0.47 and 8.26 ppm, respectively.

  17. Rate determining step in phospholipase A/sub 2/ mechanism: /sup 18/O isotope exchange determined by /sup 13/C NMR

    SciTech Connect

    Fanni, T.; Lombardo, D.; Plueckthun, A.; Dennis, E.A.

    1986-05-01

    Pancreatic and venom phospholipase A/sub 2/ display a marked preference for micellar substrates and act poorly on monomeric substrates. The authors have now examined the merit of the proposal that the product-release step is slow, but is accelerated when the enzyme acts on aggregated phospholipids. Measurements of H/sub 2/ /sup 18/O isotope exchange into specifically-labeled substrate was used to obtain information on the rate-limiting step in the enzyme action. A novel technique of distinguishing /sup 18/O incorporation by /sup 13/C-/sup 18/O vs /sup 13/C-/sup 16/O chemical shift differences at 126 MHz for /sup 13/C NMR was employed. The enzymatic hydrolysis of a micellar phosphatidylcholine analogue of platelet activating factor, 1-alkyl, 2 (1-/sup 13/C)-lauroyl-sn-glycero-3-phosphoryl-choline proceeds by O-acyl cleavage of the sn-2 ester bond. The reaction was examined for the possibility of simultaneous /sup 18/O incorporation into the substrate. No exchange was found suggesting that the catalytic step is not followed by a higher energy transition state and that it or a step before it appears to be rate-limiting.

  18. 13C CP MAS NMR and GIAO-CHF/DFT calculations of flavonoids: Morin, kaempferol, tricin, genistein, formononetin and 3,7-dihydroxyflavone

    NASA Astrophysics Data System (ADS)

    Zieli?ska, Agnieszka; Paradowska, Katarzyna; Jakowski, Jacek; Wawer, Iwona

    2008-02-01

    13C CP MAS NMR spectra of the flavonoids: morin, kaempferol, 3,7-dihydroxyflavone, tricin and isoflavones: genistein and formononetin were recorded to characterize solid-state conformations. Intramolecular hydrogen bonds forming five-, six- and seven-membered rings are present in the two morin molecules in the crystals - their 13C resonances have been assigned with the aid of the calculated shielding constants. Linear relationships between the calculated shielding constants ?DFT (ppm) and chemical shifts ( ?CPMAS, ppm) were obtained for all studied compounds. Higher correlation coefficients suggest that the conformation with "clockwise" orientation of both OH groups is more probable in the solid 3,7-dihydroxyflavone, whereas in the solid formononetin the OH and OCH 3 substituents are directed "anticlockwise". The barrier to the rotation of phenyl ring B decreases in the order: morin (2'-OH, 3-OH) > kaempferol (3-OH) > tricin.

  19. Direct quantification of M/G ratio from (13)C CP-MAS NMR spectra of alginate powders by multivariate curve resolution.

    PubMed

    Salomonsen, Tina; Jensen, Henrik Max; Larsen, Flemming Hofmann; Steuernagel, Stefan; Engelsen, Søren Balling

    2009-10-12

    Multivariate curve resolution (MCR) was applied to (13)C cross-polarisation (CP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of non-depolymerised alginate powders obtained from brown seaweed plus a pure mannuronate sample isolated from Pseudomonas fluorescens for estimation of the mannuronic acid/guluronic acid ratio (M/G ratio). An excellent MCR model with a correlation coefficient of r(2)=0.99 was established between the estimated M/G ratios and the M/G ratios obtained from the traditional (1)H solution state NMR method. The new method allows for successful determination of the M/G ratio independent of the calcium content (at least up to 2.4%, which was the upper limit in this study) with a root mean square error of prediction of 0.05. It is thus concluded that (13)C CP-MAS NMR in combination with multivariate curve resolution is a reliable, convenient (no sample preparation is required) and relatively rapid method for M/G ratio determinations of alginates and it may serve as a good alternative to the chemical techniques traditionally used. PMID:19619871

  20. 13C and 2H NMR study of structure and dynamics in banana B2 phase of a bent-core mesogen.

    PubMed

    Xu, Jiadi; Dong, Ronald Y; Domenici, Valentina; Fodor-Csorba, K; Veracini, C A

    2006-05-18

    In this paper, the difficulty in orienting the B(2) phase of the banana mesogen 1,3-Phenylene-bis 4-[4-(10-undecenyloxy)-benzoyloxy] benzoate (Pbis11BB) in a relatively high magnetic field is reported based on some observations using both (13)C and (2)H NMR. (2)H NMR spectra recorded for the two labeled isotopomers of Pbis11BB in the isotropic and B(2) phases are shown here. Preliminary results on the deuteron spin-spin relaxation (T(2)) data are reported at 61 MHz in order to underline the peculiar slow dynamics of banana-shaped liquid crystals (BLC), and these results are discussed in the framework of recent studies on similar BLC. The molecular structure and dynamics in the B(2) and crystalline phases are also studied by (13)C solid-state NMR techniques. The results also point to the slow dynamics in the B(2) phase of Pbis11BB. In particular, two-dimensional MAS exchange experiment has been performed to shed light on the molecular conformation structure of the five-ring banana core in the crystalline phase of Pbis11BB, and to compare with that of quantum mechanical calculations reported in the literature. PMID:16686487

  1. Synthesis, mass spectral characterization, NMR analyses, and DFT calculations of 1-desoxymaquindox and 4-desoxymaquindox

    NASA Astrophysics Data System (ADS)

    Zhang, Jiaheng; Peng, Qingrong; Zhang, Suxia; Li, Yubo; Li, Songqing; Gao, Haixiang; Zhou, Zhiqiang

    2011-02-01

    Maquindox, 3-methyl-2-acetylquinoxaline-1,4-dioxide, is a quinoxaline-N,N-dioxide used in veterinary medicine as a feed additive. 1-Desoxymaquindox and 4-desoxymaquindox, two novel deoxidized metabolites of maquindox are synthesized from their parent drug. This study deals with the structural and spectral properties of the maquindox metabolites by employing experimental and theoretical methods. The investigation, using ultra-performance liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry, shows independent proof of the structures. Gauge-including atomic orbital NMR chemical shifts are calculated for isomeric quinoxaline metabolite pairs and several different parameters (correlation coefficient, mean absolute error, and corrected mean absolute error) are investigated. Comparison of the experimental and calculated 1H and 13C NMR chemical shifts allows the reliable assignment of the isomeric quinoxaline compound pairs.

  2. 1H and 13C NMR Chemical Shift Assignments and Conformational Analysis for the Two Diastereomers of the Vitamin K Epoxide Reductase Inhibitor Brodifacoum

    SciTech Connect

    Cort, John R.; Cho, Herman M.

    2009-10-01

    Proton and 13C NMR chemical shift assignments and 1H-1H scalar couplings for the two diastereomers of the vitamin K epoxide reductase (VKOR) inhibitor brodifacoum have been determined from acetone solutions containing both diastereomers. Data were obtained from homo- and heteronuclear correlation spectra acquired at 1H frequencies of 750 and 900 MHz over a 268-303 K temperature range. Conformations inferred from scalar coupling and 1-D NOE measurements exhibit large differences between the diastereomers. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  3. NMR profiling of biomolecules at natural abundance using 2D 1H-15N and 1H-13C multiplicity-separated (MS) HSQC spectra

    NASA Astrophysics Data System (ADS)

    Chen, Kang; Freedberg, Darón I.; Keire, David A.

    2015-02-01

    2D NMR 1H-X (X = 15N or 13C) HSQC spectra contain cross-peaks for all XHn moieties. Multiplicity-edited1H-13C HSQC pulse sequences generate opposite signs between peaks of CH2 and CH/CH3 at a cost of lower signal-to-noise due to the 13C T2 relaxation during an additional 1/1JCH period. Such CHn-editing experiments are useful in assignment of chemical shifts and have been successfully applied to small molecules and small proteins (e.g. ubiquitin) dissolved in deuterated solvents where, generally, peak overlap is minimal. By contrast, for larger biomolecules, peak overlap in 2D HSQC spectra is unavoidable and peaks with opposite phases cancel each other out in the edited spectra. However, there is an increasing need for using NMR to profile biomolecules at natural abundance dissolved in water (e.g., protein therapeutics) where NMR experiments beyond 2D are impractical. Therefore, the existing 2D multiplicity-edited HSQC methods must be improved to acquire data on nuclei other than 13C (i.e.15N), to resolve more peaks, to reduce T2 losses and to accommodate water suppression approaches. To meet these needs, a multiplicity-separated1H-X HSQC (MS-HSQC) experiment was developed and tested on 500 and 700 MHz NMR spectrometers equipped with room temperature probes using RNase A (14 kDa) and retroviral capsid (26 kDa) proteins dissolved in 95% H2O/5% D2O. In this pulse sequence, the 1/1JXH editing-period is incorporated into the semi-constant time (semi-CT) X resonance chemical shift evolution period, which increases sensitivity, and importantly, the sum and the difference of the interleaved 1JXH-active and the 1JXH-inactive HSQC experiments yield two separate spectra for XH2 and XH/XH3. Furthermore we demonstrate improved water suppression using triple xyz-gradients instead of the more widely used z-gradient only water-suppression approach.

  4. NMR profiling of biomolecules at natural abundance using 2D 1H-15N and 1H-13C multiplicity-separated (MS) HSQC spectra.

    PubMed

    Chen, Kang; Freedberg, Darón I; Keire, David A

    2015-02-01

    2D NMR (1)H-X (X=(15)N or (13)C) HSQC spectra contain cross-peaks for all XHn moieties. Multiplicity-edited(1)H-(13)C HSQC pulse sequences generate opposite signs between peaks of CH(2) and CH/CH(3) at a cost of lower signal-to-noise due to the (13)C T(2) relaxation during an additional 1/(1)JCH period. Such CHn-editing experiments are useful in assignment of chemical shifts and have been successfully applied to small molecules and small proteins (e.g. ubiquitin) dissolved in deuterated solvents where, generally, peak overlap is minimal. By contrast, for larger biomolecules, peak overlap in 2D HSQC spectra is unavoidable and peaks with opposite phases cancel each other out in the edited spectra. However, there is an increasing need for using NMR to profile biomolecules at natural abundance dissolved in water (e.g., protein therapeutics) where NMR experiments beyond 2D are impractical. Therefore, the existing 2D multiplicity-edited HSQC methods must be improved to acquire data on nuclei other than (13)C (i.e.(15)N), to resolve more peaks, to reduce T(2) losses and to accommodate water suppression approaches. To meet these needs, a multiplicity-separated(1)H-X HSQC (MS-HSQC) experiment was developed and tested on 500 and 700 MHz NMR spectrometers equipped with room temperature probes using RNase A (14 kDa) and retroviral capsid (26 kDa) proteins dissolved in 95% H(2)O/5% D(2)O. In this pulse sequence, the 1/(1)JXH editing-period is incorporated in to the semi-constant time (semi-CT) X resonance chemical shift evolution period, which increases sensitivity, and importantly, the sum and the difference of the interleaved (1)J(XH)-active and the (1)J(XH)-inactive HSQC experiments yield two separate spectra for XH(2) and XH/XH(3). Furthermore we demonstrate improved water suppression using triple xyz-gradients instead of the more widely used z-gradient only water-suppression approach. PMID:25562571

  5. NMR assignment of 1H, 13C, and 15N resonances of rat lipocalin-type prostaglandin D synthase.

    PubMed

    Liu, Jiafu; Lv, Ying; Guo, Chenyun; Lin, Donghai

    2010-10-01

    Lipocalin-type prostaglandin D synthase (L-PGDS) acts as both a PGD(2)-synthesizing enzyme and an extracellular transporter for small lipophilic molecules. Here we report the backbone and side-chain resonance assignments of uniformly (15)N, (13)C labeled rat L-PGDS. PMID:20617402

  6. Multidimensional spatial-spectral holographic interpretation of NMR photography.

    PubMed

    Kiruluta, Andrew J M

    2006-05-21

    A spectral holographic interpretation arises naturally in nuclear magnetic resonance (NMR) photography from either the intrinsic chemical shift anisotropy of the spin system or the field inhomogeneity due to the applied spatial encoding gradients. We can thus think of NMR photography as arising from a "diffraction" off a spatial-spectral holographic grating. The spatial holographic component arises from a high dielectric constant (>50) of the NMR medium at high field strength (>4 T) when the excitation wavelength is commensurate with the size of the NMR sample; otherwise, it is a volume spectral holographic grating. In this paper, the NMR localized spectroscopy (imaging) equation is derived from the principles of spatial-spectral holography. Holographic properties of storage and programmable time delay and time reversal are shown to follow naturally from this viewpoint and are experimentally demonstrated in an inhomogeneously broadened NMR sample. These ideas are shown to be extendable to complex signal processing functions such as recognition, correlations, and triple products. PMID:16729804

  7. Conformational changes of bacteriorhodopsin along the proton-conduction chain as studied with (13)C NMR of [3-(13)C]Ala-labeled protein: arg(82) may function as an information mediator.

    PubMed Central

    Tanio, M; Tuzi, S; Yamaguchi, S; Kawaminami, R; Naito, A; Needleman, R; Lanyi, J K; Saitô, H

    1999-01-01

    We have recorded (13)C NMR spectra of [3-(13)C]Ala-labeled wild-type bacteriorhodopsin (bR) and its mutants at Arg(82), Asp(85), Glu(194), and Glu(204) along the extracellular proton transfer chain. The upfield and downfield displacements of the single carbon signals of Ala(196) (in the F-G loop) and Ala(126) (at the extracellular end of helix D), respectively, revealed conformational differences in E194D, E194Q, and E204Q from the wild type. The same kind of conformational change at Ala(126) was noted also in the Y83F mutant, which lacks the van der Waals contact between Tyr(83) and Ala(126) present in the wild type. The absence of a negative charge at Asp(85) in the site-directed mutant D85N induced global conformational changes, as manifested in displacements or suppression of peaks from the transmembrane helices, cytoplasmic loops, etc., as well as the local changes at Ala(126) and Ala(196) seen in the other mutants. Unexpectedly, no conformational change at Ala(126) was observed in R82Q (even though Asp(85) is protonated at pH 6) or in D85N/R82Q. The changes induced in the Ala(126) signal when Asp(85) is uncharged could be interpreted therefore in terms of displacement of the positive charge of Arg(82) toward Tyr(83), where Ala(126) is located. It is possible that disruption of the proton transfer chain after protonation of Asp(85) in the photocycle could cause the same kind of conformational change we detect at Ala(196) and Ala(126). If so, the latter change would be also the result of rearrangement of the side chain of Arg(82). PMID:10465768

  8. Unique Backbone-Water Interaction Detected in Sphingomyelin Bilayers with 1H/31P and 1H/13C HETCOR MAS NMR Spectroscopy

    PubMed Central

    Holland, Gregory P.; Alam, Todd M.

    2008-01-01

    Two-dimensional 1H/31P dipolar heteronuclear correlation (HETCOR) magic-angle spinning nuclear magnetic resonance (NMR) is used to investigate the correlation of the lipid headgroup with various intra- and intermolecular proton environments. Cross-polarization NMR techniques involving 31P have not been previously pursued to a great extent in lipid bilayers due to the long 1H-31P distances and high degree of headgroup mobility that averages the dipolar coupling in the liquid crystalline phase. The results presented herein show that this approach is very promising and yields information not readily available with other experimental methods. Of particular interest is the detection of a unique lipid backbone-water intermolecular interaction in egg sphingomyelin (SM) that is not observed in lipids with glycerol backbones like phosphatidylcholines. This backbone-water interaction in SM is probed when a mixing period allowing magnetization exchange between different 1H environments via the nuclear Overhauser effect (NOE) is included in the NMR pulse sequence. The molecular information provided by these 1H/31P dipolar HETCOR experiments with NOE mixing differ from those previously obtained by conventional NOE spectroscopy and heteronuclear NOE spectroscopy NMR experiments. In addition, two-dimensional 1H/13C INEPT HETCOR experiments with NOE mixing support the 1H/31P dipolar HETCOR results and confirm the presence of a H2O environment that has nonvanishing dipolar interactions with the SM backbone. PMID:18390621

  9. Synthesis, proton and 13C NMR and reaction mechanism studies of novel isoindolones derivatives, obtained through TAWERS procedure

    NASA Astrophysics Data System (ADS)

    Corona, David; Díaz, Eduardo; Guzmán, Ángel; Jankowski, Christophe K.

    2005-09-01

    A series of novel isoindolone derivatives ( 13- 18) were prepared in goods yields by applying the TAWERS methodology. A general approach for formation of isoindolones from the aza-Wittig reaction of iminophosphoranes with dialdehydes under neutral and mild conditions was realized. Using 1D NMR a [ 1, 3]-hydride migration was detected. The assignment of the structures and conformation behavior of the derivatives was achieved using 1D and 2D NMR (NOESY, DEPT, HMQC, and HMBC).

  10. /sup 13/C NMR analysis of the effects of electron radiation on graphite/polyetherimide composites. Final report

    SciTech Connect

    Ferguson, M.W.

    1989-03-01

    Initial investigations have been made into the use of high resolution nuclear magnetic resonance (NMR) for the characterization of radiation effects in graphite and Kevlar fibers, polymers, and the fiber/matrix interface in graphite/polyetherimide composites. Sample preparation techniques were refined. Essential equipment has been procured. A new NMR probe was constructed to increase the proton signal-to-noise ratio. Problem areas have been identified and plans developed to resolve them.

  11. Ab initio calculation of the equilibrium geometry and the 13C, 17O and 27A1 NMR chemical shielding tensors of the system Al 3+/CO

    NASA Astrophysics Data System (ADS)

    Weller, Th.; Meiler, W.; Michael, A.; Köhler, H. J.; Lischka, H.; Höller, R.

    1982-11-01

    The complex Al 3+/CO was investigated with respect to the equilibrium geometry using ab initio SCF calculations. Two minima have been found, both with linear configurations. The minimum corresponding to CO … Al 3+ is slightly deeper (? EO = -0.206062 au) and reveals an elongation of the equilibrium bond length C?O (0.1195 nm) with respect to that of isolated CO (0.1102 nm) and a shorter equilibrium distance RO = 0.1743 nm between Al 3+ and O. The other minimum corresponding to Al 3+…CO amounts -0.198951 au and reveals a shortening of the equilibrium bond length C?O (0.1075 nm) and an equilibrium distance RC = 0.2062 nm between Al 3+ and C. Using the equilibrium distances from these calculations the 13C, 17O and 27Al NMR chemical shielding tensors were investigated using coupled Hartree-Fock calculations with large gaussian basis sets. The results are compared with 13C NMR investigations of carbon monoxide adsorbed on decationated zeolites.

  12. Search for basic relationships between "molecular size" and "chemical structure" of aquatic natural organic matter--answers from 13C and 15N CPMAS NMR spectroscopy.

    PubMed

    Lankes, Ulrich; Lüdemann, Hans-Dietrich; Frimmel, Fritz H

    2008-02-01

    To investigate the structural composition of natural organic matter (NOM), a 3-step micro- and ultrafiltration procedure was applied to 3 surface waters from southern Germany, and fractions from all filtration steps were collected. The NOM was characterized using solid-state 13C and 15N nuclear magnetic resonance (NMR) techniques. Routine integration of the 13C NMR spectra and extended data analysis procedures were carried out for a quantitative comparison of the structural components as well as for the elucidation of structural fractionation patterns. A common feature of the large molecular size fractions was the predominance of polysaccharide material, with the dissolved high molecular weight organics being mostly enriched in N-acetylated polysaccharides derived from microbial leftovers. Aromatic structures like lignin and tannin derivatives were most abundant in the intermediate size fraction. All membranes were found to be highly permeable for branched aliphatics, i.e. isoprenoids. Fouling layers of the ultrafiltration membrane were significantly enriched in long-chain aliphatics (lipids). Biofouling was not observed on any of the membranes. Overall, a strong interdependence between the chemical structural characteristics of NOM components and their size, shape, or interaction characteristics could be shown. The results provide the basis for a better understanding of water process technologies as treatment effectiveness is strongly dependent on the chemical composition and the "size" distribution of NOM. PMID:17959215

  13. HCN, A Triple-Resonance NMR Technique for Selective Observation of Histidine and Tryptophan Side Chains in 13C/ 15N-Labeled Proteins

    NASA Astrophysics Data System (ADS)

    Sudmeier, James L.; Ash, Elissa L.; Günther, Ulrich L.; Luo, Xuelian; Bullock, Peter A.; Bachovchin, William W.

    HCN, a new 3D NMR technique for stepwise coherence transfer from 1H to 13C to 15N and reverse through direct spin couplings 1JCHand 1JCN, is presented as a method for detection and assignment of histidine and tryptophan side-chain 1H, 13C, and 15N resonances in uniformly 13C/ 15N-labeled proteins. Product-operator calculations of cross-peak volumes vs adjustable delay ? 3were employed for determination of optimal ? 3. For the phosphatidylinositol 3-kinase (PI3K SH3 domain, MW = 9.6 kD) at pH 6, H(C)N, the 1H/ 15N projection, produced observable cross peaks within 20 min. and was completely selective for the single tryptophan and single histidine. The 3D HCN experiment yielded well-defined cross peaks in 20 h for the 13C/ 15N-labeled origin-specific DNA binding domain from simian virus 40 T-antigen (T-ag-OBD 131-259, MW = 15.4 kD) at pH 5.5. Resonances from all six histidines in T-ag-OBD were observed, and 11 of the 12 1H and 13C chemical shifts and 10 of the 12 15N chemical shifts were determined. The 13C dimension proved essential in assignment of the multiply overlapping 1H and 15N resonances. From the spectra recorded at a single pH, three of the imidazoles were essentially neutral and the other three were partially protonated (22-37%). HCN yielded strong cross peaks after 18 h on a 2.0 m Msample of phenylmethanesulfonyl fluoride (PMSF)-inhibited ?-lytic protease (MW = 19.8 kD) at pH 4.4. No spectra have been obtained, however, of native or boronic acid-inhibited ?-lytic protease after 18 h at various temperatures ranging from 5 to 55°C, probably due to efficient relaxation of active-site imidazole 1H and/or 15N nuclei.

  14. Accurate, fully-automated NMR spectral profiling for metabolomics.

    PubMed

    Ravanbakhsh, Siamak; Liu, Philip; Bjordahl, Trent C; Mandal, Rupasri; Grant, Jason R; Wilson, Michael; Eisner, Roman; Sinelnikov, Igor; Hu, Xiaoyu; Luchinat, Claudio; Greiner, Russell; Wishart, David S

    2015-01-01

    Many diseases cause significant changes to the concentrations of small molecules (a.k.a. metabolites) that appear in a person's biofluids, which means such diseases can often be readily detected from a person's "metabolic profile"-i.e., the list of concentrations of those metabolites. This information can be extracted from a biofluids Nuclear Magnetic Resonance (NMR) spectrum. However, due to its complexity, NMR spectral profiling has remained manual, resulting in slow, expensive and error-prone procedures that have hindered clinical and industrial adoption of metabolomics via NMR. This paper presents a system, BAYESIL, which can quickly, accurately, and autonomously produce a person's metabolic profile. Given a 1D 1H NMR spectrum of a complex biofluid (specifically serum or cerebrospinal fluid), BAYESIL can automatically determine the metabolic profile. This requires first performing several spectral processing steps, then matching the resulting spectrum against a reference compound library, which contains the "signatures" of each relevant metabolite. BAYESIL views spectral matching as an inference problem within a probabilistic graphical model that rapidly approximates the most probable metabolic profile. Our extensive studies on a diverse set of complex mixtures including real biological samples (serum and CSF), defined mixtures and realistic computer generated spectra; involving > 50 compounds, show that BAYESIL can autonomously find the concentration of NMR-detectable metabolites accurately (~ 90% correct identification and ~ 10% quantification error), in less than 5 minutes on a single CPU. These results demonstrate that BAYESIL is the first fully-automatic publicly-accessible system that provides quantitative NMR spectral profiling effectively-with an accuracy on these biofluids that meets or exceeds the performance of trained experts. We anticipate this tool will usher in high-throughput metabolomics and enable a wealth of new applications of NMR in clinical settings. BAYESIL is accessible at http://www.bayesil.ca. PMID:26017271

  15. Accurate, Fully-Automated NMR Spectral Profiling for Metabolomics

    PubMed Central

    Ravanbakhsh, Siamak; Liu, Philip; Bjordahl, Trent C.; Mandal, Rupasri; Grant, Jason R.; Wilson, Michael; Eisner, Roman; Sinelnikov, Igor; Hu, Xiaoyu; Luchinat, Claudio; Greiner, Russell; Wishart, David S.

    2015-01-01

    Many diseases cause significant changes to the concentrations of small molecules (a.k.a. metabolites) that appear in a person’s biofluids, which means such diseases can often be readily detected from a person’s “metabolic profile"—i.e., the list of concentrations of those metabolites. This information can be extracted from a biofluids Nuclear Magnetic Resonance (NMR) spectrum. However, due to its complexity, NMR spectral profiling has remained manual, resulting in slow, expensive and error-prone procedures that have hindered clinical and industrial adoption of metabolomics via NMR. This paper presents a system, BAYESIL, which can quickly, accurately, and autonomously produce a person’s metabolic profile. Given a 1D 1H NMR spectrum of a complex biofluid (specifically serum or cerebrospinal fluid), BAYESIL can automatically determine the metabolic profile. This requires first performing several spectral processing steps, then matching the resulting spectrum against a reference compound library, which contains the “signatures” of each relevant metabolite. BAYESIL views spectral matching as an inference problem within a probabilistic graphical model that rapidly approximates the most probable metabolic profile. Our extensive studies on a diverse set of complex mixtures including real biological samples (serum and CSF), defined mixtures and realistic computer generated spectra; involving > 50 compounds, show that BAYESIL can autonomously find the concentration of NMR-detectable metabolites accurately (~ 90% correct identification and ~ 10% quantification error), in less than 5 minutes on a single CPU. These results demonstrate that BAYESIL is the first fully-automatic publicly-accessible system that provides quantitative NMR spectral profiling effectively—with an accuracy on these biofluids that meets or exceeds the performance of trained experts. We anticipate this tool will usher in high-throughput metabolomics and enable a wealth of new applications of NMR in clinical settings. BAYESIL is accessible at http://www.bayesil.ca. PMID:26017271

  16. Use of solid waste for chemical stabilization: Adsorption isotherms and {sup 13}C solid-state NMR study of hazardous organic compounds sorbed on coal fly ash

    SciTech Connect

    Netzel, D.A.; Lane, D.C.; Rovani, J.F.; Cox, J.D.; Clark, J.A.; Miknis, F.P.

    1993-09-01

    Adsorption of hazardous organic compounds on the Dave Johnston plant fly ash is described. Fly ash from Dave Johnston and Laramie River power plants were characterized using elemental, x-ray, and {sup 29}Si NMR; the Dave Johnston (DJ) fly ash had higher quartz contents, while the Laramie River fly ash had more monomeric silicate anions. Adsorption data for hydroaromatics and chlorobenzenes indicate that the adsorption capacity of DJ coal fly ash is much less than that of activated carbon by a factor of >3000; but it is needed to confirm that solid-gas and solid-liquid equilibrium isotherms can indeed be compared. However, for pyridine, pentachlorophenol, naphthalene, and 1,1,2,2-tetrachloroethane, the DJ fly ash appears to adsorb these compounds nearly as well as activated carbon. {sup 13}C NMR was used to study the adsorption of hazardous org. cpds on coal fly ash; the nuclear spin relaxation times often were very long, resulting in long experimental times to obtain a spectrum. Using a jumbo probe, low concentrations of some hazardous org. cpds could be detected; for pentachlorophenol adsorbed onto fly ash, the chemical shift of the phenolic carbon was changed. Use of NMR to study the adsorption needs further study.

  17. Solid-state and solution /sup 13/C NMR in the conformational analysis of methadone-hydrochloride and related narcotic analgesics

    SciTech Connect

    Sumner, S.C.J.

    1986-01-01

    Solid state and solution /sup 13/C NMR have been used to study the conformations of the racemic mixtures and single enantiomers of methadone hydrochloride, alpha and beta methadol hydrochloride, and alpha and beta acetylmethadol hydrochloride. The NMR spectra acquired for the compounds as solids, and in polar and nonpolar solvents are compared, in order to determine the conformation of the molecules in solution. To determine the reliability of assigning solution conformations by comparing solution and solid state chemical shift data, three bond coupling constants measured in solution are compared with those calculated from X-ray data. The conformations of the racemic mixture and plus enantiomer of methadone hydrochloride have been shown to be very similar in the solid state, where minor differences in conformation can be seen by comparing NMR spectra obtained for the solids. Also shown is that the molecules of methadone hydrochloride have conformations in polar and in nonpolar solvents which are very similar to the conformation of the molecules in the solid state.

  18. Spectral editing through laser-flash excitation in two-dimensional photo-CIDNP MAS NMR experiments.

    PubMed

    Sai Sankar Gupta, Karthick Babu; Daviso, Eugenio; Jeschke, Gunnar; Alia, A; Ernst, Matthias; Matysik, Jörg

    2014-09-01

    In solid-state photochemically induced dynamic nuclear polarization (photo-CIDNP) MAS NMR experiments, strong signal enhancement is observed from molecules forming a spin-correlated radical pair in a rigid matrix. Two-dimensional (13)C-(13)C dipolar-assisted rotational resonance (DARR) photo-CIDNP MAS NMR experiments have been applied to obtain exact chemical shift assignments from those cofactors. Under continuous illumination, the signals are enhanced via three-spin mixing (TSM) and differential decay (DD) and their intensity corresponds to the electron spin density in pz orbitals. In multiple-(13)C labelled samples, spin diffusion leads to propagation of signal enhancement to all (13)C spins. Under steady-state conditions, direct signal assignment is possible due to the uniform signal intensity. The original intensities, however, are inaccessible and the information of the local electron spin density is lost. Upon laser-flash illumination, the signal is enhanced via the classical radical pair mechanism (RPM). The obtained intensities are related to isotropic hyperfine interactions aiso and both enhanced absorptive and emissive lines can be observed due to differences in the sign of the local isotropic hyperfine interaction. Exploiting the mechanism of the polarization, selectivity can be increased by the novel time-resolved two-dimensional dipolar-assisted rotational resonance (DARR) MAS NMR experiment which simplifies the signal assignment compared to complex spectra of the same RCs obtained by continuous illumination. Here we present two-dimensional time-resolved photo-CIDNP MAS NMR experiments providing both directly: signal assignment and spectral editing by sign and strength of aiso. Hence, this experiment provides a direct key to the electronic structure of the correlated radical pair. PMID:25063951

  19. Solid-state 13C-NMR spectroscopy shows that the xyloglucans in the primary cell walls of mung bean (Vigna radiata L.) occur in different domains: a new model for xyloglucan-cellulose interactions in the cell wall

    Microsoft Academic Search

    Tracey J. Bootten; Philip J. Harris; Laurence D. Melton; Roger H. Newman

    2004-01-01

    Xyloglucans (XG) with different mobilities were identified in the primary cell walls of mung beans (Vigna radiata L.) by solid-state 13C-NMR spectro- scopy. To improve the signal:noise ratios compared with unlabelled controls, Glc labelled at either C-1 or C-4 with 13C-isotope was incorporated into the cell- wall polysaccharides of mung bean hypocotyls. Using cell walls from seedlings labelled with D-(1-

  20. Choline metabolism in breast cancer; 2 H-, 13 C- and 31 P-NMR studies of cells and tumors

    Microsoft Academic Search

    R. Katz-Brull; R. Margalit; P. Bendel; H. Degani

    1998-01-01

    Choline metabolism in breast cancer cells and tumors has been investigated by multinuclear NMR in order to provide the biochemical\\u000a basis for the presence of high phosphocholine in breast carcinoma relative to benign breast tumors and normal breast tissue.\\u000a Choline was found to be transported into MCF7 human breast cancer cells and rapidly phosphorylated to phosphocholine which\\u000a was then accumulated

  1. ^13C NMR studies on the organic zero-gap system, theta-(BEDT-TTF)2I3 under pressure

    Microsoft Academic Search

    Kazuya Miyagawa; Motoaki Hirayama; Masafumi Tamura; Kazushi Kanoda

    2008-01-01

    We present NMR data for the organic material, theta-(BEDT-TTF)2I3 under pressure, which is a candidate for zero-gap conductor with cone-like dispersion. The quasi-two-dimensional organic conductor alpha-(BEDT-TTF)2I3 is known to show peculiar behaviors under high pressure. The resistivity is insensitive to temperature, while the Hall coefficient is strongly dependent on temperature. The band calculation suggests that this system is in the

  2. sup 13 C NMR identification of intermediates formed by 2-methyl-2-propanol adsorption in H-ZSM-5

    Microsoft Academic Search

    M. T. Aronson; R. J. Gorte; D. White; W. E. Farneth

    1989-01-01

    ¹³C NMR spectroscopy has been used to characterize intermediates formed by the adsorption of 2-methyl-2-propanol, (CHâ)â ¹³COH, on a H-ZSM-5 zeolite. Previous adsorption studies had shown that, upon exposure of H-ZSM-5 to this alcohol and subsequent evacuation at 295 K, an adsorption complex could be formed, which had a coverage of 1 alcohol molecule\\/Al atom in the zeolite and had

  3. Evidence of metabolic transformations of amino acids into higher alcohols through (13)C NMR studies of wine alcoholic fermentation.

    PubMed

    López-Rituerto, Eva; Avenoza, Alberto; Busto, Jesús H; Peregrina, Jesús M

    2010-04-28

    Because the metabolite transformations in wine fermentation processes play a crucial role in the organoleptic and hygienic quality of wines, the nuclear magnetic resonance (NMR) technique is presented as a significant tool to follow metabolic pathways. In this paper, we investigated the transformation of several amino acids into their corresponding higher alcohols during the alcoholic fermentation, showing that the amino acids are totally consumed in the first stages of the process. PMID:20369806

  4. Solid-state 13C NMR studies of a large fossil gymnosperm from the Yallourn Open Cut, Latrobe Valley, Australia

    USGS Publications Warehouse

    Bates, A.L.; Hatcher, P.G.

    1989-01-01

    A series of samples taken from the cross section of a 3-m-diameter fossilized gymnospermous log (Araucariaceae) in the Yallourn Seam of the Australian brown coals was examined by solid state 13C nuclear magnetic resonance to delineate chemical changes related to the combined processes of peatification and coalification. The results show that cellulosic materials were degraded and lost on the periphery of the log, however, the degree of such degradation in the central core is substantially less. The lignin is uniformly altered by coalification reactions to a macromolecular substance displaying decreased aryl ether linkages but significantly greater amounts of carbon linkages compared to modern lignin. Changes in the methoxyl carbon contents of lignin in cross section reveal demethylation reactions, but these do not appear to be related to degree of carbon linking. Both the degredation of cellulosic materials and demethylation of lignin appear to be early diagenetic processes occurring during peatification independently of the coalification reactions. ?? 1989.

  5. The structure and (local) stability constants of borate esters of mono- and di-saccharides as studied by 11B and 13C NMR spectroscopy.

    PubMed

    van den Berg, R; Peters, J A; van Bekkum, H

    1994-02-01

    The formation of borate esters of various mono- and di-saccharides in aqueous solution was studied by 11B and 13C NMR spectroscopy. Association constants K(B-L) at a carbohydrate-borate molar ratio of 1:1, pH 7, and 25 degrees C were determined and compared with literature values obtained from potentiometry. The association constants K(B-L) were converted into local association constants Kloc(B-L) by using the distribution of the various anomeric forms in D2O. In this way, values of Kloc(B-L) were obtained, which appear to be characteristic of the configuration concerned. They explain the favourable effect of borate in the alkaline isomerisation of lactose into lactulose. At a low molar ratio (1:3) of carbohydrate-borate, predominantly diborate esters (B-)2L were formed. PMID:8156542

  6. 13C NMR study of the magnetic properties of the quasi-one-dimensional conductor (TMTTF)2SbF6

    NASA Astrophysics Data System (ADS)

    Iwase, F.; Sugiura, K.; Furukawa, K.; Nakamura, T.

    2011-09-01

    Magnetic properties in the quasi-one-dimensional organic salt, (TMTTF)2SbF6, where TMTTF is tetramethyltetrathiafulvalene, are investigated by 13C NMR under pressures. Antiferromagnetic phase transition at ambient pressure (AFI) is confirmed. Charge ordering is suppressed by pressure and is not observed under 8 kbar. For 5

  7. Use of 13C NMR and ftir for elucidation of degradation pathways during natural litter decomposition and composting I. early stage leaf degradation

    USGS Publications Warehouse

    Wershaw, R.L.; Leenheer, J.A.; Kennedy, K.R.; Noyes, T.I.

    1996-01-01

    Oxidative degradation of plant tissue leads to the formation of natural dissolved organic carbon (DOC) and humus. Infrared (IR) and 13C nuclear magnetic resonance (NMR) spectrometry have been used to elucidate the chemical reactions of the early stages of degradation that give rise to DOC derived from litter and compost. The results of this study indicate that oxidation of the lignin components of plant tissue follows the sequence of O-demethylation, and hydroxylation followed by ring-fission, chain-shortening, and oxidative removal of substituents. Oxidative ring-fission leads to the formation of carboxylic acid groups on the cleaved ends of the rings and, in the process, transforms phenolic groups into aliphatic alcoholic groups. The carbohydrate components are broken down into aliphatic hydroxy acids and aliphatic alcohols.

  8. Detecting a new source for photochemically induced dynamic nuclear polarization in the LOV2 domain of phototropin by magnetic-field dependent (13)C NMR spectroscopy.

    PubMed

    Kothe, Gerd; Lukaschek, Michail; Link, Gerhard; Kacprzak, Sylwia; Illarionov, Boris; Fischer, Markus; Eisenreich, Wolfgang; Bacher, Adelbert; Weber, Stefan

    2014-10-01

    Phototropin is a flavin mononucleotide (FMN) containing blue-light receptor, which regulates, governed by its two LOV domains, the phototropic response of higher plants. Upon photoexcitation, the FMN cofactor triplet state, (3)F, reacts with a nearby cysteine to form a covalent adduct. Cysteine-to-alanine mutants of LOV domains instead generate a flavin radical upon illumination. Here, we explore the formation of photochemically induced dynamic nuclear polarization (CIDNP) in LOV2-C450A of Avena sativa phototropin and demonstrate that photo-CIDNP observed in solution (13)C NMR spectra can reliably be interpreted in terms of solid-state mechanisms including a novel triplet mechanism. To minimize cross-polarization, which transfers light-induced magnetization to adjacent (13)C nuclei, our experiments were performed on proteins reconstituted with specifically (13)C-labeled flavins. Two potential sources for photo-CIDNP can be identified: The photogenerated triplet state, (3)F, and the triplet radical pair (3)(F(-•)W(+•)), formed by electron abstraction of (3)F from tryptophan W491. To separate the two contributions, photo-CIDNP studies were performed at four different magnetic fields ranging from 4.7 to 11.8 T. Analysis revealed that, at fields <9 T, both (3)(F(-•)W(+•)) and (3)F contribute to photo-CIDNP, whereas at high magnetic fields, the calculated enhancement factors of (3)F agree favorably with their experimental counterparts. Thus, we have for the first time detected that a triplet state is the major source for photo-CIDNP in a photoactive protein. Since triplet states are frequently encountered upon photoexcitation of flavoproteins, the novel triplet mechanism opens up new means of studying electronic structures of the active cofactors in these proteins at atomic resolution. PMID:25207844

  9. Longitudinal relaxation properties of 1HN and 1H? determined by direct-detected 13C NMR experiments to study intrinsically disordered proteins (IDPs)

    NASA Astrophysics Data System (ADS)

    Hošek, Tomáš; Gil-Caballero, Sergi; Pierattelli, Roberta; Brutscher, Bernhard; Felli, Isabella C.

    2015-05-01

    Intrinsically disordered proteins (IDPs) are functional proteins containing large fragments characterized by high local mobility. Bioinformatic studies have suggested that a significant fraction (more than 30%) of eukaryotic proteins has disordered regions of more than 50 amino acids in length. Hence, NMR methods for the characterization of local compactness and solvent accessibility in such highly disordered proteins are of high importance. Among the available approaches, the HET-SOFAST/BEST experiments (Schanda et al., 2006, Rennella et al., 2014) provide semi-quantitative information by monitoring longitudinal 1H relaxation of amide protons under different initial conditions. However, when approaching physiological sample conditions, the potential of these amide 1H detected experiments is reduced due to rapid amide proton solvent exchange. 13C direct detection methods therefore provide a valuable alternative thanks to a higher chemical shift dispersion and their intrinsic insensitivity toward solvent exchange. Here we present two sets of 13C-detected experiments, which indirectly measure 1HN and 1H? inversion recovery profiles. The experiments consist of an initial spin inversion-recovery block optimized for selective manipulation of different types of proton spins followed by a CON read-out scheme. The proposed experiments were tested on human ?-synuclein and ubiquitin, two representative examples of unfolded and folded proteins.

  10. 1H and 13C NMR studies of the interaction of eugenol, phenol, and triethyleneglycol dimethacrylate with phospholipid liposomes as a model system for odontoblast membranes.

    PubMed

    Fujisawa, S; Kadoma, Y; Komoda, Y

    1988-11-01

    To clarify the mechanism of the interaction of eugenol with odontoblast membranes compared with that of phenol and triethyleneglycol dimethacrylate (TEGDMA), we employed dipalmitoylphosphatidylcholine (DPPC) liposomes as a model system for odontoblast membranes. 1H and 13C nuclear magnetic resonance spectroscopy (NMR) was used as the spectroscopic approach in the study of this interaction. No signals of 1H and 13C due to eugenol in the DPPC/eugenol liposomes were observed, indicating that the mobility of eugenol was strongly disturbed by DPPC and that eugenol did not diffuse from the liposomes once it was incorporated. The change in chemical shifts due to phenol between the free state and the DPPC/phenol liposomes was not found, indicating that phenol resides in the aqueous phase or near the surfaces of liposomes, its interaction being markedly weaker than that of eugenol. The signals due to TEGDMA in the DPPC/TEGDMA liposomes were split into two peaks: a lower-field peak (free TEGDMA) and a higher-field one (membrane-bound TEGDMA). TEGDMA with ethyleneglycol groups seemed to be activated on the liposomes as a surfactant-like agent. PMID:3183163

  11. Ionization of isocitrate bound to pig hear NADP/sup +/-dependent isocitrate dehydrogenase: /sup 13/C NMR study of substrate binding

    SciTech Connect

    Ehrlich, R.S.; Colman, R.F.

    1987-06-16

    Isocitrate and ..cap alpha..-ketoglutarate have been synthesized with carbon-13 enrichment at specific positions. The /sup 13/C NMR spectra of these derivatives were measured as a function of pH. The magnitudes of the changes in chemical shifts with pH for free isocitrate and the magnesium-isocitrate complex suggest that the primary site of ionization at the ..beta..-carboxyl. In the presence of the enzyme NADP/sup +/-dependent isocitrate dehydrogenase and the activating metal magnesium, the carbon-13 resonances of all three carboxyls remain constant from pH 5.5 to pH 7.5. Thus, the carboxyls remain in the ionized form in the enzyme-isocitrate complex. The ..cap alpha..-hydroxyl carbon resonance could not be located in the enzyme-isocitrate complex, suggesting immobilization of this group. Magnesium produces a 2 ppm downfield shift of the ..beta..-carboxyl but does not change the resonances of the ..cap alpha..- and ..gamma..-carboxyls. This result is consistent with metal activation of both the dehydrogenation and decarboxylation reactions. The /sup 13/C NMR spectrum of ..cap alpha..-ketoglutarate remains unchanged in the presence of isocitrate dehydrogenase, implying the absence of alterations in geometry in the enzyme-bound form. Formation of the quaternary complex with Mg/sup 2 +/ and NADPH leads to loss of the ..cap alpha..-ketoglutarate resonances and the appearance of new resonances characteristic of ..cap alpha..-hydroxyglutarate. In addition, a broad peak ascribed to the enol form of ..cap alpha..-ketoglutarate is observed. The substantial change in the shift of the ..beta..-carboxyl of isocitrate and the lack of significant shifts in the other carboxyls of isocitrate or ..cap alpha..-ketoglutarate suggest that interaction of the ..beta..-carboxyl with the enzyme contributes to the tighter binding of isocitrate and may be significant for the oxidative decarboxylation function of isocitrate dehydrogenase.

  12. 2D 1H and 13C NMR in the conformation of 4-aryl derivatives of thieno[3,2-c]pyridines

    NASA Astrophysics Data System (ADS)

    Cruz-Almanza, R.; Diaz-Torres, E.; Miranda, L. D.; Corona, D.; Lopez-Castañares, R.; Fuentes, A.; van Calsteren, M. R.; Jankowski, K.

    1999-05-01

    In this paper we report the synthesis and spectral analysis of new heterocyclic derivatives of 4-aryl thieno[3,2-c]pyridines. These functionalized compounds were obtained from heteroaromatic aldehyde derivative and a cyclisation via tandem aza-Wittig iminophosphorane reactions sequence. The assignment of the structures and conformation of the different derivatives were achieved using 1D and 2D NMR (NOESY, DEPT, HMQC and HMBC).

  13. Solid-state 13C NMR studies of dissolved organic matter in pore waters from different depositional environments

    USGS Publications Warehouse

    Orem, W.H.; Hatcher, P.G.

    1987-01-01

    Dissolved organic matter (DOM) in pore waters from sediments of a number of different depositional environments was isolated by ultrafiltration using membranes with a nominal molecular weight cutoff of 500. This > 500 molecular weight DOM represents 70-98% of the total DOM in these pore waters. We determined the gross chemical structure of this material using both solid-state 13C nuclear magnetic resonance spectroscopy and elemental analysis. Our results show that the DOM in these pore waters appears to exist as two major types: one type dominated by carbohydrates and paraffinic structures and the second dominated by paraffinic and aromatic structures. We suggest that the dominance of one or the other structural type of DOM in the pore water depends on the relative oxidizing/reducing nature of the sediments as well as the source of the detrital organic matter. Under dominantly anaerobic conditions carbohydrates in the sediments are degraded by bacteria and accumulate in the pore water as DOM. However, little or no degradation of lignin occurs under these conditions. In contrast, sediments thought to be predominantly aerobic in character have DOM with diminished carbohydrate and enhanced aromatic character. The aromatic structures in the DOM from these sediments are thought to arise from the degradation of lignin. The large amounts of paraffinic structures in both types of DOM may be due to the degradation of unidentified paraffinic materials in algal or bacterial remains. ?? 1987.

  14. Structural study of the fulvic fraction during composting of activated sludge-plant matter: elemental analysis, FTIR and 13C NMR.

    PubMed

    Jouraiphy, A; Amir, S; Winterton, P; El Gharous, M; Revel, J-C; Hafidi, M

    2008-03-01

    The starting fulvic structures isolated from an initial mixture of activated sludge and plant matter presented abundant peptide structures and hydrocarbons that absorb in FTIR spectra around (1650 and 1560 cm(-1)) and 1072 cm(-1), respectively. They also present a high resonance signal in the O- and N-alkyl areas of (13)C NMR spectra. As composting proceeded, some changes led to the formation of the molecular structures of fulvic fraction as demonstrated by a decrease of intensity of compounds absorbing around 1072 cm(-1) and an increase of those absorbing around 1140 cm(-1). The resonance of O- and N-substituted alkyl carbon also decreased from 55.7% to 33.8%, with an increase in the intensity of aromatic carbons, alkyls and carboxyls. These data indicate that the microbial community that developed during composting used polysaccharides as an energy source, structures which are supplied in abundance in the initial material. The fulvic fraction of the final compost is much richer in aromatic structures and aliphatic ethers/esters, which are most likely preserved from the original material but probably also synthesized through the microbial activities. The occurrence of alkyl ethers/esters at the end of composting is demonstrated by strong absorbance around 1140 cm(-1) in the FTIR spectra and large peaks at 32 and 174 ppm in the NMR spectra. These structures could also be produced following the creation of ether/ester bonds during the humification process. PMID:17446064

  15. Analysis of mercerization process based on the intensity change of deconvoluted resonances of (13)C CP/MAS NMR: Cellulose mercerized under cooling and non-cooling conditions.

    PubMed

    Miura, Kento; Nakano, Takato

    2015-08-01

    The area intensity change of C1, C4, and C6 in spectrum obtained by (13)C CP/MAS NMR and the mutual relationship between their changes were examined for cellulose samples treated with various concentrations of aqueous NaOH solutions under non-cooling and cooling conditions. The area intensity of C1-up and C6-down changed cooperatively with that of C4-down which corresponds to the crystallinity of samples: "-up" and "-down" are the up- and down- field component in a splitting peak of NMR spectrum, respectively. The intensity change of C1-up starts to decrease with decreasing in that of C4-down after that of C6-down is almost complete. These changes were more clearly observed for samples treated under cooling condition. It can be suggested that their characteristic change relates closely to the change in conformation of cellulose chains by induced decrystallization and the subsequent crystallization of cellulose II, and presumed that their changes at microscopic level relate to the macroscopic morphological changes such as contraction along the length of cellulose chains and recovery along the length. PMID:26042706

  16. NMR ((1)H and (13)C) based signatures of abnormal choline metabolism in oral squamous cell carcinoma with no prominent Warburg effect.

    PubMed

    Bag, Swarnendu; Banerjee, Deb Ranjan; Basak, Amit; Das, Amit Kumar; Pal, Mousumi; Banerjee, Rita; Paul, Ranjan Rashmi; Chatterjee, Jyotirmoy

    2015-04-17

    At functional levels, besides genes and proteins, changes in metabolome profiles are instructive for a biological system in health and disease including malignancy. It is understood that metabolomic alterations in association with proteomic and transcriptomic aberrations are very fundamental to unravel malignant micro-ambient criticality and oral cancer is no exception. Hence deciphering intricate dimensions of oral cancer metabolism may be contributory both for integrated appreciation of its pathogenesis and to identify any critical but yet unexplored dimension of this malignancy with high mortality rate. Although several methods do exist, NMR provides higher analytical precision in identification of cancer metabolomic signature. Present study explored abnormal signatures in choline metabolism in oral squamous cell carcinoma (OSCC) using (1)H and (13)C NMR analysis of serum. It has demonstrated down-regulation of choline with concomitant up-regulation of its break-down product in the form of trimethylamine N-oxide in OSCC compared to normal counterpart. Further, no significant change in lactate profile in OSCC possibly indicated that well-known Warburg effect was not a prominent phenomenon in such malignancy. Amongst other important metabolites, malonate has shown up-regulation but d-glucose, saturated fatty acids, acetate and threonine did not show any significant change. Analyzing these metabolomic findings present study proposed trimethyl amine N-oxide and malonate as important metabolic signature for oral cancer with no prominent Warburg effect. PMID:25769954

  17. /sup 13/C NMR study of effects of fasting and diabetes on the metabolism of pyruvate in the tricarboxylic acid cycle and of the utilization of pyruvate and ethanol in lipogenesis in perfused rat liver

    SciTech Connect

    Cohen, S.M.

    1987-01-27

    /sup 13/C NMR has been used to study the competition of pyruvate dehydrogenase with pyruvate carboxylase for entry of pyruvate into the tricarboxylic acid (TCA) cycle in perfused liver from streptozotocin-diabetic and normal donor rats. The relative proportion of pyruvate entering the TCA cycle by these two routes was estimated from the /sup 13/C enrichments at the individual carbons of glutamate when (3-/sup 13/C)alanine was the only exogenous substrate present. In this way, the proportion of pyruvate entering by the pyruvate dehydrogenase route relative to the pyruvate carboxylase route was determined to be 1:1.2 +/- 0.1 in liver from fed controls, 1:7.7 +/- 2 in liver from 24-fasted controls, and 1:2.6 +/- 0.3 in diabetic liver. Pursuant to this observation that conversion of pyruvate to acetyl coenzyme A (acetyl-CoA) was greatest in perfused liver from fed controls, the incorporation of /sup 13/C label into fatty acids was monitored in this liver preparation. With the exception of the repeating methylene carbons, fatty acyl carbons labeled by (1-/sup 13/C)acetyl-CoA (from (2-/sup 13/C)pyruvate) gave rise to resonances distinguishable on the basis of chemical shift from those observed when label was introduced by (3-/sup 13/C)alanine plus (2-/sup 13/C)ethanol, which are converted to (2-/sup 13/C)acetyl-CoA. Thus, measurement of /sup 13/C enrichment at several specific sites in the fatty acyl chains in time-resolved spectra of perfused liver offers a novel way of monitoring the kinetics of the biosynthesis of fatty acids. In addition to obtaining the rate of lipogenesis, it was possible to distinguish the contributions of chain elongation from those of the de novo synthesis pathway and to estimate the average chain length of the /sup 13/C-labeled fatty acids produced.

  18. Application of ChemDraw NMR Tool: Correlation of Program-Generated (Super 13)C Chemical Shifts and pK[subscript a] Values of Para-Substituted Benzoic Acids

    ERIC Educational Resources Information Center

    Hongyi Wang

    2005-01-01

    A study uses the ChemDraw nuclear magnetic resonance spectroscopy (NMR) tool to process 15 para-substituted benzoic acids and generate (super 13)C NMR chemical shifts of C1 through C5. The data were plotted against their pK[subscript a] value and a fairly good linear fit was found for pK[subscript a] versus delta[subscript c1].

  19. Conformational analysis, spectroscopic study (FT-IR, FT-Raman, UV, 1H and 13C NMR), molecular orbital energy and NLO properties of 5-iodosalicylic acid.

    PubMed

    Karaca, Caglar; Atac, Ahmet; Karabacak, Mehmet

    2015-02-01

    In this study, 5-iodosalicylic acid (5-ISA, C7H5IO3) is structurally characterized by FT-IR, FT-Raman, NMR and UV spectroscopies. There are eight conformers, Cn, n=1-8 for this molecule therefore the molecular geometry for these eight conformers in the ground state are calculated by using the ab-initio density functional theory (DFT) B3LYP method approach with the aug-cc-pVDZ-PP basis set for iodine and the aug-cc-pVDZ basis set for the other elements. The computational results identified that the most stable conformer of 5-ISA is the C1 form. The vibrational spectra are calculated DFT method invoking the same basis sets and fundamental vibrations are assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method with PQS program. Total density of state (TDOS) and partial density of state (PDOS) and also overlap population density of state (COOP or OPDOS) diagrams analysis for C1 conformer were calculated using the same method. The energy and oscillator strength are calculated by time-dependent density functional theory (TD-DFT) results complement with the experimental findings. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) are calculated and presented. The NMR chemical shifts ((1)H and (13)C) spectra are recorded and calculated using the gauge independent atomic orbital (GIAO) method. Mulliken atomic charges of the title molecule are also calculated, interpreted and compared with salicylic acid. The optimized bond lengths, bond angles and calculated NMR and UV, vibrational wavenumbers showed the best agreement with the experimental results. PMID:25448933

  20. Effect of organic matter application on CP-MAS-13C-NMR spectra of humic acids from a brown soil

    NASA Astrophysics Data System (ADS)

    Dou, S.

    2009-04-01

    The humified SOM or humic substances (HS) composed of humic acid (HA), fulvic acid (FA) and humin (HM) represent the most microbially recalcitrant and stable reservoir of organic carbon in soil (Piccolo et al., 2004). OM applications can influence the amount and structural characteristics of HS(Dou et al., 2008). During the past few decades, there has been much research on HS, but their chemical structure is still not fully understood (Dong, 2006).CP-MAS-13C-NMR spectroscopy was considered as an effective method to study structures of HS without dissolving problem compared with liquid 13C-NMR (Conte et al., 1997; Dou et al., 2008). It can directly measure the carbon framework and reflect the nature of HS transformation after OM application (Spaccini et al., 2000). For that reason, this method was applied in this study. The objective of this paper was to clarify the effect of long term OM application on the changes of structural characteristics in HAs, which provided new information for improving soil fertility by OM application. The experiment was carried out on a brown soil (Paleudalf in USDA Soil Taxonomy) at Shenyang Agricultural University, Liaoning province, China (N41°48'-E123°25'). The experiment included 3 treatments: zero-treatment (CKbr), and two pig manure (PM) treatments (O1 and O2) at the rates of 0.9 t ha-1 and 1.8 t ha-1 of organic carbon, respectively. The samples of the HA fraction were extracted, separated and purified according to the method described by Dou et al. (1991). Elemental composition, Differential thermal analysis (DTA), -lgK value, FT-IR and CP-MAS- 13C-NMR of HAs were performed. Effects on the contents of orgaic carbon and its composition. The contents of TOC were from 8.77 g kg-1 to 12.25 g kg-1. The relative contents in TOC for WSS, HA, and FA were 6.87%, 14.2% and 19.8%. Comparing the CKbr, the contents of WSS, HA and FA for O1 and O2 increased, but relative contents of WSS and FA decreased. The content of the HA increased after OM application, which was consistent with other studies (Wang et al., 2001). The content of the WSS increased after the OM application indicating that the increase of labile organic carbon. The C/H mole ratio of the HS could reflect the degree of condensation (Dou et al., 1995). Effects on HA chemical and optical properties. The chemical and optical properties of HA were listed. The C/H ratios decreased after OM application, from 0.830 (CKbr) to 0.754 (O2). While ?lgK increased, from 0.623 (CKbr) to 0.658 (O2). The HA structure tended to become simpler. The C/H ratio of the HA decreased after OM application. This indicates that OM application decreased the degree of condensation. The ?lgK values can be used as the index of HA molecule complexity in the soil. If ?lgK increased, the molecular structure becomes simpler. After OM application, ?lgK increased indicating that the molecular structure became simpler. Effects on HA thermal properties. It could be seen that HA had exothermic peaks in moderate and high temperature regions. After OM application, heat (H2) of exothermic peak increased in moderate temperature region, while heat (H3) of exothermic peak decreased in high temperature region. The the heat ratio of exothermic peaks in high temperature region to moderate (H3/H2) decreased. From CKbr to O2, H3/H2 decreased from 4.31 to0.86. The HA had moderate and high temperature exothermic peaks. The heat of exothermic peaks in the moderate temperature region might show that aliphatic compounds decomposed and peripheral functional groups decarboxylated. The heat of the exothermic peaks in the high temperature region might show that the HA was oxidized completely and inter-aromatic structures in the molecule decomposed. The heat ratio of the high to moderate temperature exothermic regions (H3/H2) decreased significantly after PM application, indicating that the proportion of aromatic structure decreased and the HA molecular structure simplified. Effects on CP-MAS-13C-NMR spectrum of HA. The CP-MAS- 13C-NMR spectra of the HA were quite similar to each other

  1. Quantification of xylooligomers in hot water wood extract by 1H-13C heteronuclear single quantum coherence NMR.

    PubMed

    Yan, Jipeng; Kiemle, David; Liu, Shijie

    2015-03-01

    A new method that employs 2D-HSQCNMRwasdeveloped to determine xylooligomer concentrations in the hot water extracts of Paulownia elongata, aspen, sugar maple, southern hardwood mixture, and willow woodchips. Equations for computing oligomer concentrations calculation were developed based on HSQC corresponding resonance integrals of xylooligomer C1H1 and monomeric sugar standard curves. The degree of polymerization (DP) of xylooligomers in the hot water extract was computed by equation obtained from a series of xylooligomer standard solutions with DPs that ranged from 2 to 6. Another group of hot water wood extract that is served as a control group was hydrolyzed by 4% sulfuric acid at 121 °C for 60 min in order to convert all xylooligomer into xylose. As 2D-HSQC resonance response is different for acetylated xylo-units, as compared with non-acetylated units, proton NMR was used to calibrate the acetylated xylooligomer concentration. Xylooligomer concentrations determined from HSQC compared fairly well with data after hydrolysis. PMID:25498715

  2. Solvent effect on pathways and mechanisms for D-fructose conversion to 5-hydroxymethyl-2-furaldehyde: in situ 13C NMR study.

    PubMed

    Kimura, Hiroshi; Nakahara, Masaru; Matubayasi, Nobuyuki

    2013-03-14

    Noncatalytic reactions of D-fructose were kinetically investigated in dimethylsulfoxide (DMSO), water, and methanol as a function of time at temperatures of 30-150 °C by applying in situ (13)C NMR spectroscopy. The products were quantitatively analyzed with distinction of isomeric species by taking advantage of site-selective (13)C labeling technique. In DMSO, D-fructose was converted first into 3,4-dihydroxy-2-dihydroxymethyl-5-hydroxymethyltetrahydrofuran having no double bond in the ring, subsequently into 4-hydroxy-5-hydroxymethyl-4,5-dihydrofuran-2-carbaldehyde having one double bond through dehydration, and finally into 5-hydroxymethyl-2-furaldehyde (5-HMF) having two double bonds. No other reaction pathways were involved, as shown from the carbon mass balance. In water, 5-HMF, the final product in DMSO, was generated with the precursors undetected and furthermore transformed predominantly into formic and levulinic acids and slightly into 1,2,4-benzenetriol accompanied by polymerization. D-glucose was also produced through the reversible transformation of the reactant D-fructose. In methanol, some kinds of anhydro-D-fructoses were generated instead of 5-HMF. The reaction pathways can thus be controlled by taking advantage of the solvent effect. The D-fructose conversion reactions are of the first order with respect to the concentration of D-fructose and proceed on the order of minutes in DMSO but on the order of hours in water and methanol. The rate constant was three orders of magnitude larger in DMSO than in water or methanol. PMID:23458365

  3. sup 15 N and sup 13 C NMR studies of ligands bound to the 280,000-dalton protein porphobilinogen synthase elucidate the structures of enzyme-bound product and a Schiff base intermediate

    SciTech Connect

    Jaffe, E.K.; Rajagopalan, J.S. (Univ. of Pennsylvania School of Dental Medicine, Philadelphia (USA)); Markham, G.D. (Fox Chase Cancer Center, Philadelphia, PA (USA))

    1990-09-11

    Porphobilinogen synthase (PBGS) catalyzes the asymmetric condensation of two molecules of 5-aminolevulinic acid (ALA). Despite the 280,000-dalton size of PBGS, much can be learned about the reaction mechanism through {sup 13}C and {sup 15}N NMR. The authors knowledge, these studies represent the largest protein complex for which individual nuclei have been characterized by {sup 13}C or {sup 15}N NMR. Here they extend their {sup 13}C NMR studies to PBGS complexes with (3,3-{sup 2}H{sub 2},3-{sup 13}C)ALA and report {sup 15}N NMR studies of ({sup 15}N)ALA bound to PBGS. As in their previous {sup 13}C NMR studies, observation of enzyme-bound {sup 15}N-labeled species was facilitated by deuteration at nitrogens that are attached to slowly exchanging hydrogens. For holo-PBGS at neutral pH, the NMR spectra reflect the structure of the enzyme-bound product porphobilinogen (PBG), whose chemical shifts are uniformly consistent with deprotonation of the amino group whose solution pK{sub a} is 11. Despite this local environment, the protons of the amino group are in rapid exchange with solvent. For methyl methanethiosulfonate (MMTS) modified PBGS, the NMR spectra reflect the chemistry of an enzyme-bound Schiff base intermediate that is formed between C{sub 4} of ALA and an active-site lysine. The {sup 13}C chemical shift of (3,3-{sup 2}H{sub 2},3-{sup 13}C)ALA confirms that the Schiff base is an imine of E stereochemistry. By comparison to model imines formed between ({sup 15}N)ALA and hydrazine or hydroxylamine, the {sup 15}N chemical shift of the enzyme-bound Schiff base suggests that the free amino group is an environment resembling partial deprotonation. Deprotonation of the amino group would facilitate formation of a Schiff base between the amino group of the enzyme-bound Schiff base and C{sub 4} of the second ALA substrate. This is the first evidence supporting carbon-nitrogen bond formation as the initial site of interaction between the two substrate molecules.

  4. Magic-angle-spinning NMR on solid biological systems. Analysis Of the origin of the spectral linewidths

    NASA Astrophysics Data System (ADS)

    Hemminga, M. A.; de Jager, P. A.; Krüse, J.; Lamerichs, R. M. J. N.

    Magic-angle-spinning (MAS) high-power 1H-decoupled 13C and 31P NMR has been applied to solid biological materials to obtain information about the mechanisms that determine the spectral linewidths. The line broadening in MAS 31P NMR spectra of solid tobacco mosaic virus (TMV) has been investigated by selective saturation and T2 measurements. About 90 Hz stems from homogeneous effects, whereas the inhomogeneous contribution is approximately 100 Hz. The inhomogeneous line broadening is assigned to macroscopic inhomogeneities in the sample and not to variations in the nucleotide bases along the RNA strand in TMV. It is concluded that sample preparation is of vital importance for obtaining well-resolved spectra. Under optimal preparation techniques the isotropic values of the chemical shift of the different 31P sites have been determined to obtain information about the secondary structure of the viral RNA. The chemical shift anisotropy has been determined from the relative intensities of the spinning side bands in the spectra. The chemical shift information is used to make a tentative assignment of the resonance in terms of the three structurally distinguishable phosphate groups in TMV. The origin of the linewidths in MAS NMR has been examined further by 13C NMR of approximately 10% 13C-enriched coat protein of cowpea chlorotic mottle virus, using selective excitation and saturation techniques, as well as measurements of the relaxation times T1 ? and T2. The C?O resonance in the spectrum is composed of an inhomogeneous and homogeneous part with a total linewidth of 700 Hz. The homogeneous linewidth, contributing with 200 Hz, is found to arise from slow molecular motions in the solid on a millisecond timescale.

  5. 2H NMR and 13C-IRMS analyses of acetic acid from vinegar, 18O-IRMS analysis of water in vinegar: international collaborative study report.

    PubMed

    Thomas, Freddy; Jamin, Eric

    2009-09-01

    An international collaborative study of isotopic methods applied to control the authenticity of vinegar was organized in order to support the recognition of these procedures as official methods. The determination of the 2H/1H ratio of the methyl site of acetic acid by SNIF-NMR (site-specific natural isotopic fractionation-nuclear magnetic resonance) and the determination of the 13C/12C ratio, by IRMS (isotope ratio mass spectrometry) provide complementary information to characterize the botanical origin of acetic acid and to detect adulterations of vinegar using synthetic acetic acid. Both methods use the same initial steps to recover pure acetic acid from vinegar. In the case of wine vinegar, the determination of the 18O/16O ratio of water by IRMS allows to differentiate wine vinegar from vinegars made from dried grapes. The same set of vinegar samples was used to validate these three determinations. The precision parameters of the method for measuring delta13C (carbon isotopic deviation) were found to be similar to the values previously obtained for similar methods applied to wine ethanol or sugars extracted from fruit juices: the average repeatability (r) was 0.45 per thousand, and the average reproducibility (R) was 0.91 per thousand. As expected from previous in-house study of the uncertainties, the precision parameters of the method for measuring the 2H/1H ratio of the methyl site were found to be slightly higher than the values previously obtained for similar methods applied to wine ethanol or fermentation ethanol in fruit juices: the average repeatability was 1.34 ppm, and the average reproducibility was 1.62 ppm. This precision is still significantly smaller than the differences between various acetic acid sources (delta13C and delta18O) and allows a satisfactory discrimination of vinegar types. The precision parameters of the method for measuring delta18O were found to be similar to the values previously obtained for other methods applied to wine and fruit juices: the average repeatability was 0.15 per thousand, and the average reproducibility was 0.59 per thousand. The above values are proposed as repeatability and reproducibility limits in the current state of the art. On the basis of this satisfactory inter-laboratory precision and on the accuracy demonstrated by a spiking experiment, the authors recommend the adoption of the three isotopic determinations included in this study as official methods for controlling the authenticity of vinegar. PMID:19664468

  6. Metal Carbonation of Forsterite in Supercritical CO2 and H2O Using Solid State 29Si, 13C NMR Spectroscop

    SciTech Connect

    Kwak, Ja Hun; Hu, Jian Z.; Hoyt, David W.; Sears, Jesse A.; Wang, Chong M.; Rosso, Kevin M.; Felmy, Andrew R.

    2010-03-11

    Ex situ solid state NMR was used for the first time to study fundamental mineral carbonation processes and reaction extent relevant to geologic carbon sequestration (GCS) using a model silicate mineral forsterite (Mg2SiO4)+supercriticalCO2 with and without H2O. Run conditions were 80 C and 96 atm. 29Si NMR clearly shows that in the absence of CO2, the role of H2O is to hydrolyze surface Mg-O-Si bonds to produce dissolved Mg2+, and mono- and oligomeric hydroxylated silica species. Surface hydrolysis products contain only Q0 (Si(OH)4) and Q1(Si(OH)3OSi) species. An equilibrium between Q0, Q1 and Mg2+ with a saturated concentration equivalent to less than 3.2% of the Mg2SiO4 conversion is obtained at a reaction time of up to 7 days. Using scCO2 without H2O, no reaction is observed within 7 days. Using both scCO2 and H2O, the surface reaction products for silica are mainly Q3 (SiOH(OSi)3) species accompanied by a lesser amount of Q2 (Si(OH)2(OSi)2) and Q4 (Si(OSi)4). However, no Q0 and Q1 were detected, indicating the carbonic acid formation/deprotonation and magnesite (MgCO3) precipitation reactions are faster than the forsterite hydrolysis process. Thus it can be concluded that the Mg2SiO4 hydrolysis process is the rate limiting step of the overall mineral carbonation process. 29Si NMR combined with XRD, TEM, SAED and EDX further reveal that the reaction is a surface reaction with the Mg2SiO4 crystallite in the core and with condensed Q2-Q4 species forming amorphous surface layers. 13C MAS NMR identified a possible reaction intermediate as (MgCO3)4-Mg(OH)2-5H2O. However, at long reaction times only crystallite magnesite MgCO3 products are observed.

  7. A comparative study of the conformational equilibria, vibrational, 1H and 13C NMR spectra of isobutyranilide and its derivative the anticancer drug flutamide

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.; Förner, Wolfgang; Ali, Shaikh A.

    2014-10-01

    The molecular structure of isobutyranilide and flutamide were investigated by DFT-B3LYP/6-311G** and MP2/6-311G** calculations. Isobutyranilide was predicted to exist predominantly in a planar cis conformation, while flutamide in non-planar structures with the CF3 and the NO2 groups adopting an out of the phenyl-plane configuration. The vibrational frequencies of the low energy structures of the two molecules were computed at the DFT-B3LYP level of theory. From the calculated Gibb's free energies, isobutyranilide is estimated to have an equilibrium mixture of 91% cis and 9% trans structures, while flutamide is calculated to have a mixture of 65% cis-cis and 28% trans-cis structures at 298.15 K. The analysis of the observed vibrational spectra supports the presence of isobutyranilide in only one conformation at room temperature. From a 1:1 acetonitrile solvent experiment flutamide is determined to exist in more than one conformation at ambient temperature. Complete vibrational assignments of the normal modes of isobutyranilide and flutamide were provided on the basis of combined normal coordinate calculations and experimental Infrared and Raman spectra. The 1H and 13C NMR spectra of isobutyranilide were measured and their chemical shifts were compared to the corresponding ones of flutamide.

  8. 13C NMR quantification of mono and diacylglycerols obtained through the solvent-free lipase-catalyzed esterification of saturated fatty acids.

    PubMed

    Fernandes, Jane Luiza Nogueira; de Souza, Rodrigo Octavio Mendonça Alves; de Vasconcellos Azeredo, Rodrigo Bagueira

    2012-06-01

    In the present investigation, we studied the enzymatic synthesis of monoacylglycerols (MAG) and diacylglycerols (DAG) via the esterification of saturated fatty acids (stearic, palmitic and an industrial residue containing 87% palmitic acid) and glycerol in a solvent-free system. Three immobilized lipases (Lipozyme RM IM, Lipozyme TL IM and Novozym 435) and different reaction conditions were evaluated. Under the optimal reaction conditions, esterifications catalyzed by Lipozyme RM IM resulted in a mixture of MAG and DAG at high conversion rates for all of the substrates. In addition, except for the reaction of industrial residue at atmospheric pressure, all of these products met the World Health Organization and European Union directives for acylglycerol mixtures for use in food applications. The products were quantified by (13)C NMR, with the aid of an external reference signal which was generated from a sealed coaxial tube filled with acetonitrile-d3. After calibrating the area of this signal using the classical external reference method, the same coaxial tube was used repeatedly to quantify the reaction products. PMID:22539418

  9. Formation of 1:1 and 2:1 host-guest inclusion complexes of ?-cyclodextrin with cycloalkanols: A 1H and 13C NMR spectroscopic study

    NASA Astrophysics Data System (ADS)

    Akita, Tomoki; Yoshikiyo, Keisuke; Yamamoto, Tatsuyuki

    2014-09-01

    Binding constants (Ka's) for the formation of inclusion complexes of ?-cyclodextrin (?-CD) with cycloalkanols (c-CnOH; n = 4-8) were determined by means of 1H and 13C NMR titration, under two different conditions: (i) only 1:1 host-guest inclusion complexes are formed when the guest is in excess; (ii) the formation of 2:1 inclusion complexes occurs only after that of 1:1 inclusion complexes, when the host is in excess. The results of this work showed that ?-CD can include c-C4OH or c-C5OH only when the molar ratio is 1:1; larger ring-sized cycloalkanols such as c-C6OH, c-C7OH or c-C8OH can be included only when the molar ratio is 2:1. These findings, together with those obtained for the four derivatives of ?-CD, per-6-O-methyl-?-CD, per-2-O-methyl-?-CD, per-3-O-methyl-?-CD, and per-2,6-di-O-methyl-?-CD, suggested that ?-CD forms 2:1 inclusion complexes with c-C6OH, c-C7OH or c-C8OH in a tail-to-tail manner, in which the secondary hydroxy sides of the two CD molecules face each other. Two-dimensional ROESY measurements confirmed our results.

  10. Early estrogen-induced metabolic changes and their inhibition by actinomycin D and cycloheximide in human breast cancer cells: 31P and 13C NMR studies.

    PubMed Central

    Neeman, M; Degani, H

    1989-01-01

    Metabolic changes following estrogen stimulation and the inhibition of these changes in the presence of actinomycin D and cycloheximide were monitored continuously in perfused human breast cancer T47D clone 11 cells with 31P and 13C NMR techniques. The experiments were performed by estrogen rescue of tamoxifen-treated cells. Immediately after perfusion with estrogen-containing medium, a continuous enhancement in the rates of glucose consumption, lactate production by glycolysis, and glutamate synthesis by the Krebs cycle occurred with a persistent 2-fold increase at 4 hr. The content of phosphocholine had increased by 10% to 30% within the first hour of estrogen stimulation, but the content of the other observed phosphate metabolites as well as the pH remained unchanged. Pretreatment with either actinomycin D or cycloheximide, at concentrations known to inhibit mRNA and protein synthesis, respectively, and simultaneous treatment with estrogen and each inhibitor prevented the estrogen-induced changes in glucose metabolism. This suggested that the observed estrogen stimulation required synthesis of mRNA and protein. These inhibitors also modulated several metabolic activities that were not related to estrogen stimulation. The observed changes in the in vivo kinetics of glucose metabolism may provide a means for the early detection of the response of human breast cancer cells to estrogen versus tamoxifen treatment. PMID:2748604

  11. I: Low Frequency NMR and NQR Using a dc SQUID. II: Variable-temperature 13C CP/MAS of Organometallics

    SciTech Connect

    Ziegeweid, M.A.

    1995-11-29

    NMR and NQR at low frequencies are difficult prospects due to small nuclear spin polarization. Furthermore, the sensitivity'of the inductive pickup circuitry of standard spectrometers is reduced as the frequency is lowered. I have used a cw-SQUID (Superconducting QUantum Interference Device) spectrometer, which has no such frequency dependence, to study the local atomic environment of {sup 14}N via the quadrupolar interaction. Because {sup 14}N has spin I = 1 and a 0-6 MHz frequency range, it is not possible to obtain well-resolved spectra in high magnetic fields. I have used a technique to observe {sup 14}N NQR resonances via their effect on neighboring protons mediated by the heteronuclear dipolar interaction to study peptides and narcotics. The sensitivity of the SQUID is not enough to measure low-frequency surface (or other low spin density) systems. The application of spin-polarized xenon has been previously used to enhance polarization in conventional NMR experiments. Because xenon only polarizes spins with which it is in contact, it is surface selective. While differences in chemical shifts between surface and bulk spins are not large, it is expected that the differences in quadrupole coupling constant should be very large due to the drastic change of the electric field gradient surrounding spins at the surface. With this in mind, I have taken preliminary steps to measure SQUID detected polarization transfer from Xe to another spin species at 4.2 K and in small magnetic fields (<50 G). In this regime, the spin-lattice relaxation of xenon is dependent on the applied magnetic field. The results of our efforts to characterize the relaxation of xenon are presented. The final section describes the solid-state variable-temperature (VT) one- and two-dimensional {sup 13}C cross polarization (CP)/magic angle spinning (MAS) NMR of Hf({eta}{sup 5}-C{sub 5}H{sub 5}){sub 2}({eta}{sup 1}-C{sub 5}H{sub 5}){sub 2}, Zr({eta}{sup 5}-C{sub 5}H{sub 5}){sub 3}({eta}{sup 1}-C{sub 5}H{sub 5}) and Sn({eta}{sup 1}-C{sub 5}H{sub 5}){sub 4}. This work was undertaken in the hope of gaining insight into the intramolecuhrr dynamics, specifically which fluxional processes exist in the solid state, by what mechanism rearrangements are occurring, and the activation energies by which these processes are governed.

  12. Parahydrogen Induced Polarization of 1-13C-Phospholactate-d2 for Biomedical Imaging with >30,000,000-fold NMR Signal Enhancement in Water

    PubMed Central

    2015-01-01

    The synthetic protocol for preparation of 1-13C-phosphoenolpyruvate-d2, precursor for parahydrogen-induced polarization (PHIP) of 1-13C-phospholactate-d2, is reported. 13C nuclear spin polarization of 1-13C-phospholactate-d2 was increased by >30,000,000-fold (5.75 mT) in water. The reported 13C polarization level approaching unity (>15.6%), long lifetime of 13C hyperpolarized 1-13C-phospholactate-d2 (58 ± 4 s versus 36 ± 2 s for nondeuterated form at 47.5 mT), and large production quantities (52 ?moles in 3 mL) in aqueous medium make this compound useful as a potential contrast agent for the molecular imaging of metabolism and other applications. PMID:24738968

  13. /sup 13/C and /sup 17/O NMR and IR spectroscopic study of a series of carbonyl(4-substituted pyridine)(meso-tetraphenylporphinato)iron(II) complexes. Correlations between NMR chemical shifts and IR stretching frequencies of the carbonyl ligand and Taft parameters of the pyridine substituent

    SciTech Connect

    Box, J.W.; Gray, G.M.

    1987-08-26

    The results of a /sup 13/C and /sup 17/O NMR and IR spectroscopic study of a series of carbonyl(4 substituted pyridine)(meso-tetraphenylporphinato)iron(II) (Fe(TPP)(CO)(py-4-X)) complexes are presented. Good to excellent linear correlations between the /sup 13/ and /sup 17/O NMR chemical shifts and the IR stretching frequencies of the carbonyl ligand are observed as the pyridine substituent is varied. Good to excellent linear correlations are also observed between these NMR chemical shifts and IR stretching frequencies and the NMR chemical shifts and IR stretching force constants for the trans carbonyls of a series of cis-Mo(CO)/sub 4/(py-4-X)/sub 2/ complexes as the pyridine substituent is varied. The relationship between the donor ability of the pyridine ligands and the /sup 13/C and /sup 17/O NMR chemical shifts and the IR stretching frequencies of the carbonyl ligands in the Fe(TPP)(CO)(py-4-X) complexes has been quantitated by fitting the spectroscopic data to the single and the dual Taft substituent parameters of the pyridine substituent. Good to excellent correlations are observed. The upfield shift in the /sup 13/C NMR resonance of the carbonyl ligand as the electron-donor ability of the pyridine increases is unique. This has been rationalized by using the Buchner and Schenk description of metal carbonyl /sup 13/C NMR chemical shifts. 49 references, 3 figures, 6 tables.

  14. Orientation and motion of tetrahydrofuran in graphite intercalation compounds. Proton NMR studies of Cs(THF){sub 1.3}C{sub 24} and K(THF){sub 2.5}C{sub 24}

    SciTech Connect

    Schmidt, C.; Rosen, M.E.; Caplan, D.F.; Pines, A. [Lawrence Berkeley Lab., CA (United States)]|[Univ. of California, Berkeley, CA (United States); Quinton, M.F. [Laboratoire de Physique Quantique, Paris (France)

    1995-06-29

    The orientation and motion of tetrahydrofuran (THF) in the ternary graphite intercalation compounds Cs(THF){sub 1.3}C{sub 24} and K(THF){sub 2.5}C{sub 24} have been studied by proton NMR. Simulations of the NMR spectra indicate that the THF molecules in Cs(THF){sub 1.3}C{sub 24} have their mean planes oriented parallel to the layers of the host lattice, while the THF molecules in K(THF){sub 2.5}C{sub 24} have their mean planes oriented at an angle between 50{degree} and 75{degree} from the graphite layers. The proton NMR spectra of both compounds show evidence that the THF molecules rotate about the normal to the graphite layers and confirm X-ray diffraction studies showing a degree of orientational disorder in the samples, corresponding to a mosaic spread in the graphite layer orientation. Simulations indicate that the conformation of intercalated THF is different than gas or liquid phase THF, which has been found to have a ring puckering amplitude of 0.38-0.44 A and to undergo nearly free pseudorotation through a series of conformations. Best agreement between simulated and experimental NMR spectra of Cs(THF){sub 1.3}C{sub 24} was obtained with THF interconverting between two conformations of C{sub s} symmetry and a puckering amplitude of 0.30 A. 31 refs., 15 figs.

  15. Multinuclear 183W and 13C NMR and indirect photometry study for the identification and the characterization of new complexes of sugar acids

    NASA Astrophysics Data System (ADS)

    Hlaïbi, Miloudi; Hor, Mustapha; Riri, Mohamed; Benjjar, Abdelkhalek; Verchère, Jean-François

    2009-02-01

    Colourless tungstate complexes of the sugar acids, L-manonnic, D-glucaric and galactaric acids have been studied in aqueous solutions. Multinuclear 13C and 183W NMR have been used to identify the structures of the complexes and the sites of chelation of each ligand. Indirect photometry has been used to determine the stoichiometry and the stability constants of the complexes. For mannonic acid, two complexes of the lactic type with a mono-nuclear and a di-nuclear tungsten core have been identified at acidic pH. In these complexes, a (OH) group at the carbon atom in ? position is necessary to the formation of the complex and only the hydroxyl groups (OH) of the carboxyl function and of the carbon atom in ? position belongs to the site of chelation. Upon increasing the pH, the lactic complexes disappear: first the mono-nuclear, then also the di-nuclear lactic complexes, however a new complex of mixed (lactic + erythro) type with a (5, 2) composition has been observed. Upon increasing the pH a single erythro complex appears and at pH 10 a small amount of threo (tetradentate) type complex has been observed. For glucaric and galactaric acids , a new tri-nuclear complex (3, 3, 6) is formed in acid medium, this complex is composed of three mono-nuclear bidentate sites of chelation related one to the other. Upon increasing the pH, these new tri-nuclear complexes disappear and only for the W-galactarate system there is formation of a di-nuclear tetradentate complex of type erythro analogous to the complex of the mannonic acid.

  16. Characterization of the spherical intermediates and fibril formation of hCT in HEPES solution using solid-state 13C-NMR and transmission electron microscopy.

    PubMed

    Itoh-Watanabe, Hikari; Kamihira-Ishijima, Miya; Kawamura, Izuru; Kondoh, Masashi; Nakakoshi, Masamichi; Sato, Michio; Naito, Akira

    2013-10-21

    Human calcitonin (hCT) is a 32-amino acid peptide hormone that contains an intrachain disulfide bridge between Cys1 and Cys7 and a proline amide at the C-terminus. hCT tends to associate to form a fibril precipitate of the same type as amyloid fibrils, and hence has been studied as a model of amyloid fibril formation. The fibrillation process in N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid (HEPES) solution was examined using transmission electron microscopy. The rate of hCT fibrillation in HEPES solution was much lower than in phosphate buffer and acetic acid solution. Spherical intermediate aggregates (nuclei) were observed during the early stage of fibril formation. Short proto-fibrils appeared on the surface of the spherical intermediates. Subsequently, the spherical intermediates transformed directly into long proto-fibrils, which then elongated into mature hCT fibrils. The fibrillation process was also examined using solid-state (13)C-NMR spectroscopy, which indicated that the fibril structure was a ?-sheet in the central region and a mixture of random coils and ?-sheets at the C-terminus. The kinetics of fibril formation was examined in terms of a two-step autocatalytic reaction mechanism. The first-step nucleation rate (k1) was lower in HEPES solution than in phosphate buffer and acetic acid solution because the half-life of the intermediates is significantly longer in HEPES solution. In contrast, the second-step fibril elongation rate (k2) was similar in HEPES solution and acidic solutions. Specific interaction of HEPES molecules with hCT may stabilize the spherical intermediates and consequently inhibit the fibril elongation process of hCT. PMID:24002168

  17. Solid-state {sup 19}F and {sup 13}C NMR of room temperature fluorinated graphite and samples thermally treated under fluorine: Low-field and high-resolution studies

    SciTech Connect

    Giraudet, J. [Matiere Condensee et Resonance Magnetique, Universite Libre de Bruxelles, Faculte des Sciences, CP 232, Boulevard du Triomphe, B-1050 (Belgium); Dubois, M. [Laboratoire des Materiaux Inorganiques, UMR-CNRS 6002-Universite Blaise Pascal, 24 av. des Landais, 63177 Aubiere Cedex (France); Guerin, K. [Laboratoire des Materiaux Inorganiques, UMR-CNRS 6002-Universite Blaise Pascal, 24 av. des Landais, 63177 Aubiere Cedex (France); Pinheiro, J.P. [Laboratoire des Materiaux Inorganiques, UMR-CNRS 6002-Universite Blaise Pascal, 24 av. des Landais, 63177 Aubiere Cedex (France); Hamwi, A. [Laboratoire des Materiaux Inorganiques, UMR-CNRS 6002-Universite Blaise Pascal, 24 av. des Landais, 63177 Aubiere Cedex (France); Stone, W.E.E. [Matiere Condensee et Resonance Magnetique, Universite Libre de Bruxelles, Faculte des Sciences, CP 232, Boulevard du Triomphe, B-1050 (Belgium); Pirotte, P. [Matiere Condensee et Resonance Magnetique, Universite Libre de Bruxelles, Faculte des Sciences, CP 232, Boulevard du Triomphe, B-1050 (Belgium); Masin, F. [Matiere Condensee et Resonance Magnetique, Universite Libre de Bruxelles, Faculte des Sciences, CP 232, Boulevard du Triomphe, B-1050 (Belgium)]. E-mail: fmasin@ulb.ac.be

    2005-04-15

    Room temperature graphite fluorides consisting of raw material and samples post-treated in pure fluorine atmosphere in the temperature range 100-500 deg. C have been studied by solid-state NMR. Several NMR approaches have been used, both high and low-field {sup 19}F, {sup 19}F MAS and {sup 13}C MAS with {sup 19}F to {sup 13}C cross polarization. The modifications, in the graphitic lattice, of the catalytic iodine fluorides products have been examined. A transformation of the C-F bond character from semi-ionic to covalent has been found to occur at a post-treatment temperature close to 400 deg. C. It is shown that covalency increases with temperature.

  18. 13C-NMR analysis of chain microstructure of copolyimides on the basis of 2,2-bis[(3,4-dicarboxyphenoxyl)-phenyl]-propane dianhydride synthesized in molten benzoic acid

    Microsoft Academic Search

    Alexander A. Kuznetsov; Anna Yu. Tsegelskaya; Nikolay S. Perov

    2012-01-01

    Three series of copolyimides CPI-1, CPI-2 and CPI-3 were prepared in molten benzoic acid, based on 2,2-bis-[(3,4-dicarboxyphenoxy)-phenyl]-propane dianhydride (intermonomer) and three pairs of diamines (comonomers): aromatic\\/aliphatic (CPI-1, CPI-3) and moderate basic aromatic\\/low basic aromatic (CPI-2). The chain microstructure of copolyimides was determined by means of the high resolution 13C NMR spectroscopy. It was found that microstructure of copolyimides depends on

  19. Distinguishing tautomerism in the crystal structure of (Z)-N-(5-ethyl-2,3-di-hydro-1,3,4-thiadiazol-2-ylidene) -4-methylbenzenesulfonamide using DFT-D calculations and {sup 13}C solid-state NMR

    SciTech Connect

    Li, Xiaozhou; Bond, Andrew D.; Johansson, Kristoffer E.; Van de Streek, Jacco, E-mail: jacco.vandestreek@sund.ku.dk [Department of Pharmacy, University of Copenhagen, Universitetsparken 2, Copenhagen DK-2100 (Denmark)

    2014-08-01

    The crystal structure of (Z)-N-(5-ethyl-2,3-di-hydro-1,3,4-thiadiazol-2-ylidene) -4-methylbenzenesulfonamide contains an imine tautomer, rather than the previously reported amine tautomer. The tautomers can be distinguished using dispersion-corrected density functional theory calculations and by comparison of calculated and measured {sup 13}C solid-state NMR spectra. The crystal structure of the title compound, C{sub 11}H{sub 13}N{sub 3}O{sub 2}S{sub 2}, has been determined previously on the basis of refinement against laboratory powder X-ray diffraction (PXRD) data, supported by comparison of measured and calculated {sup 13}C solid-state NMR spectra [Hangan et al. (2010 ?). Acta Cryst. B66, 615–621]. The mol@@ecule is tautomeric, and was reported as an amine tautomer [systematic name: N-(5-ethyl-1,3,4-thia@@diazol-2-yl)-p-toluene@@sulfonamide], rather than the correct imine tautomer. The protonation site on the mol@@ecule’s 1,3,4-thia@@diazole ring is indicated by the inter@@molecular contacts in the crystal structure: N—H?O hydrogen bonds are established at the correct site, while the alternative protonation site does not establish any notable inter molecular inter@@actions. The two tautomers provide essentially identical Rietveld fits to laboratory PXRD data, and therefore they cannot be directly distinguished in this way. However, the correct tautomer can be distinguished from the incorrect one by previously reported qu@@anti@@tative criteria based on the extent of structural distortion on optimization of the crystal structure using dispersion-corrected density functional theory (DFT-D) calculations. Calculation of the {sup 13}C SS-NMR spectrum based on the correct imine tautomer also provides considerably better agreement with the measured {sup 13}C SS-NMR spectrum.

  20. Solid-State Dipolar INADEQUATE NMR Spectroscopy with a Large Double-Quantum Spectral Width

    E-print Network

    Hong, Mei

    Solid-State Dipolar INADEQUATE NMR Spectroscopy with a Large Double-Quantum Spectral Width Mei Hong Academic Press Key Words: solid-state NMR; INADEQUATE; double-quan- tum; C7; dipolar recoupling. Recently, solid-state homonuclear double-quantum NMR spec- troscopy has been increasingly employed to obtain

  1. C NMR Spectra C NMR Spectra

    E-print Network

    Collum, David B.

    S16 1 H and 13 C NMR Spectra (see p S3) Me N-i-Pr #12;S17 1 H and 13 C NMR Spectra (see p S3) Me NBn #12;S18 1 H and 13 C NMR Spectra (see p S4) NBn #12;S19 1 H and 13 C NMR Spectra (see p S4) NBn Me Me Me #12;S20 1 H and 13 C NMR Spectra (see p S4) N-n-Bu Me Me Me #12;S21 1 H and 13 C NMR Spectra

  2. Experimental (X-ray, (13)C CP/MAS NMR, IR, RS, INS, THz) and Solid-State DFT Study on (1:1) Co-Crystal of Bromanilic Acid and 2,6-Dimethylpyrazine.

    PubMed

    ?uczy?ska, Katarzyna; Dru?bicki, Kacper; Lyczko, Krzysztof; Dobrowolski, Jan Cz

    2015-06-01

    A combined structural, vibrational spectroscopy, and solid-state DFT study of the hydrogen-bonded complex of bromanilic acid with 2,6-dimethylpyrazine is reported. The crystallographic structure was determined by means of low-temperature single-crystal X-ray diffraction, which reveals the molecular units in their native protonation states, forming one-dimensional infinite nets of moderate-strength O···H-N hydrogen bonds. The nature of the crystallographic forces, stabilizing the studied structure, has been drawn by employing the noncovalent interactions analysis. It was found that, in addition to the hydrogen bonding, the intermolecular forces are dominated by stacking interactions and C-H···O contacts. The thermal and calorimetric analysis was employed to probe stability of the crystal phase. The structural analysis was further supported by a computationally assisted (13)C CP/MAS NMR study, providing a complete assignment of the recorded resonances. The vibrational dynamics was explored by combining the optical (IR, Raman, TDs-THz) and inelastic neutron scattering (INS) spectroscopy techniques with the state-of-the-art solid-state density functional theory (DFT) computations. Despite the quasi-harmonic approximation assumed throughout the study, an excellent agreement between the theoretical and experimental data was achieved over the entire spectral range, allowing for a deep and possibly thorough understanding of the vibrational characteristics of the system. Particularly, the significant influence of the long-range dipole coupling on the IR spectrum has been revealed. On the basis of a wealth of information gathered, the recent implementation of a dispersion-corrected linear-response scheme has been extensively examined. PMID:25961154

  3. Synthesis, properties, and multinuclear NMR (/sup 125/Te//sup 1/H/, /sup 13/C//sup 1/H/, /sup 1/H Studies of Di- and polytelluroether ligands

    SciTech Connect

    Hope, E.G.; Kemmitt, T.; Levason, W.

    1988-01-01

    Convenient syntheses for RTeLi (R = Me or Ph) from RLi and tellurium in tetrahydrofuran at low temperatures are described. The RTeLi react readily with organic dihalides X(CH/sub 2/)/sub n/X (X = Cl or Br), the products depending upon the temperature and the carbon chain length (n). Thus at low temperatures CH/sub 2/Cl/sub 2/ and Cl(CH/sub 2/) produce high yields of RTe(CH/sub 2/)/sub n/TeR (n = 1 or 3), but at room temperature Cl(CH/sub 2/)/sub n/ Cl (n = 2 or 3) affords R/sub 2/Te/sub 2/ olefin. 1,4-Dihalobutanes give R/sub 2/Te and Te(CH/sub 2/)/sub 3/Ch/sub 2/, while Cl(CH/sub 2/)/sub 5/Cl produced mixtures of R/sub 2/Te,RTe(CH/sub 2/)/sub 5/TeR, and Te(CH/sub 2/)/sub 4/CH/sub 2/. Preparations for RTe(CH/sub 2/)/sub 6/TeR, MeTe(CH/sub 2/)/sub 10/TeMe, and MeC(CH/sub 2/TeMe)/sub 3/ are described. PHTeLi and C(CH/sub 2/Br)/sub 4/ gave C(CH/sub 2/TePh)/sub 4/, but MeTeLi unexpectedly gave CH/sub 2/CH/sub 2/C(CH/sub 2/Te13/C//sup 1/H/, and /sup 125/Te//sup 1/H/ NMR and mass spectrometry and by the preparation of derivatives. Trends in the /sup 125/Te chemical shifts and /sup 1/J/sub Te-C/, /sup 2/J/sub Te-C/, and /sup 2/J/sub Te-H/ coupling constants are discussed and compared with the corresponding /sup 77/Se data of selenium analogues.

  4. A spectral atlas of the nu(sub 12) fundamental of (13)C(12)CH6 in the 12 micron region

    NASA Technical Reports Server (NTRS)

    Weber, Mark; Reuter, Dennis C.; Sirota, J. Marcos; Blass, William E.; Hillman, John J.

    1994-01-01

    The recent discovery of the minor isotopomer of ethane, (13)C(12)CH6, in the planetary atmospheres of Jupiter and Neptune, added ethane to the molecules which can be used to determine isotopic (12)C(12)C ratios for the jovian planets. The increased spectral resolution and coverage of the IR and far-IR instruments to be carried on the Cassini mission to Saturn and Titan may enable the detection of the minor isotopomer. Accurate frequency and cross-section measurements of the nu(sub 12) fundamental under controlled laboratory condition are important to interpret current and future planetary spectra. High resolution spectra of the minor isotopomer (13)C(12)CH6 have been recorded in the 12.2 micron region using the Kitt Peak Fourier Transform (FTS) and the Goddard Tunable Diode Laser spectrometer (TDL). In a global fit to 19 molecular constants in a symmetric top Hamiltonian, transition frequencies of the nu(sub 12) fundamental ranging up to J=35 and K=20 have been determined with a standard deviation of less than 0.0005 cm(exp -1). From selected line intensity measurements, a vibrational dipole moment for the nu(sub 12) fundamental has been derived. Observed and calculated spectra covering the region from 740 cm(exp -1) and to 910 cm(exp -1) are presented. A compilation of transition frequencies, line intensities, and lower state energies are included for general use in the astronomical community.

  5. (1)H-(13)C-(29)Si triple resonance and REDOR solid-state NMR-A tool to study interactions between biosilica and organic molecules in diatom cell walls.

    PubMed

    Wisser, Dorothea; Brückner, Stephan I; Wisser, Florian M; Althoff-Ospelt, Gerhard; Getzschmann, Jürgen; Kaskel, Stefan; Brunner, Eike

    2015-01-01

    Triple resonance solid-state NMR experiments using the spin combination (1)H-(13)C-(29)Si are still rarely found in the literature. This is due to the low natural abundance of the two heteronuclei. Such experiments are, however, increasingly important to study hybrid materials such as biosilica and others. A suitable model substance, ideally labeled with both (13)C and (29)Si, is thus very useful to optimize the experiments before applying them to studies of more complex samples such as biosilica. Tetraphenoxysilane could be synthesized in an easy, two-step synthesis including double isotope labelling. Using tetraphenoxysilane, we established a (1)H-(13)C-(29)Si double CP-based HETCOR experiment and applied it to diatom biosilica from the diatom species Thalassiosira pseudonana. Furthermore, we carried out (1)H-(13)C{(29)Si} CP-REDOR experiments in order to estimate the distance between the organic matrix and the biosilica. Our experiments on diatom biosilica strongly indicate a close contact between polyamine-containing parts of the organic matrix and the silica. This corroborates the assumption that the organic matrix is essential for the control of the cell wall formation. PMID:25638422

  6. Improvement of the inverse-gated-decoupling sequence for a faster quantitative analysis of various samples by 13C NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Giraudeau, Patrick; Baguet, Evelyne

    2006-05-01

    The inverse-gated-decoupling sequence enables quantitative 1H decoupled 13C spectra to be obtained. We modified this sequence so as to obtain the same result in less time for molecules containing carbons with various relaxation properties. For that, we determined the optimal 13C longitudinal-magnetization initial value for a faster relaxation while 1H decoupler is stopped. This value can be calculated precisely via the nuclear Overhauser effects, the longitudinal relaxation times, together with the determination of the relaxation rate constants of carbons while 1H are out of equilibrium. A supplementary delay of 1H decoupling and/or a series of selective pulses applied at the beginning of the recovery delay allow an acceleration of 13C longitudinal relaxation. We applied this method to the molecule of vanillin. The simultaneous quantification of all carbons was carried out with a recovery delay divided by two compared to the usual sequence.

  7. Phosphorus-31, sup 15 N, and sup 13 C NMR of glyphosate: Comparison of pH titrations to the herbicidal dead-end complex with 5-enolpyruvoylshikimate-3-phosphate synthase

    SciTech Connect

    Castellino, S.; Leo, G.C.; Sammons, R.D.; Sikorski, J.A. (Monsanto Agricultural Company, St. Louis, MO (USA))

    1989-05-02

    The herbicidal dead-end ternary complex (E{sup S3P}{sub Glyph}) of glyphosate (N-(phosphonomethyl)glycine) with 5-enolpyruvoylshikimate-3-phosphate synthase (EPSPS) and the substrate shikimate 3-phosphate (S3P) has been characterized by {sup 31}P, {sup 15}N, and {sup 13}C NMR. The NMR spectra of EPSPS-bound glyphosate show unique chemical shifts ({delta}) for each of the three nuclei. By {sup 31}P NMR, glyphosate in the dead-end complex is a distinct species 3.5 ppm downfield from free glyphosate. The {sup 13}C signal of glyphosate in the dead-end complex is shifted 4 ppm downfield from that of free glyphosate. The {sup 15}N signal for glyphosate (99%) in the dead-end complex is 5 ppm further downfield than that of any free zwitterionic species and 10 ppm downfield from that of the average free species at pH 10.1. The structures of each ionic state of glyphosate are modeled with force field calculations by using MacroModel. A correlation is made for the {sup 31}P {delta} and the C-P-O bond angle, and the {sup 13}C and {sup 15}N {delta} values are postulated to be related to C-C-O and C-N-C bond angles, respectively. The downfield {sup 31}P chemical shift perturbation for S3P in the EPSPS binary complex is consistent with ionization of the 3-phosphate of S3P upon binding. Comparison with the S3P {sup 31}P {delta} vs pH titration curve specifies predominantly the dianion of the 3-phosphate in the E{sup S3P} binary complex, while the E{sup S3P}{sub Glyph} complex indicates net protonation at the 3-phosphate. Chemical shift perturbations of this latter type may be explained by changes in the O-P-O bond angle.

  8. Accurate Measurement of Methyl 13C Chemical Shifts by Solid-State NMR for the Determination of Protein Sidechain Conformation: the Influenza A M2 Transmembrane Peptide as an Example

    PubMed Central

    Hong, Mei; Mishanina, Tatiana V.; Cady, Sarah D.

    2014-01-01

    The use of sidechain methyl 13C chemical shifts for the determination of the rotameric conformation of Val and Leu residues in proteins by solid-state NMR spectroscopy is described. Examination of the solution NMR stereospecifically assigned methyl groups shows significant correlation between the difference in the two methyl carbons’ chemical shifts and the sidechain conformation. It is found that ?-helical and ?-sheet backbones cause different sidechain methyl chemical shift trends. In ?-helical Leu’s, a relatively large absolute methyl 13C shift difference of 2.89 ppm is found for the most populated mt rotamer (?1=?60°, ?2=180°), while a much smaller value of 0.73 ppm is found for the next populated tp rotamer (?1=180°, ?2=60°). For ?-helical Val residues, the dominant t rotamer (?1=180°) has more downfield C?2 chemical shifts than C?1 by 1.71 ppm, while the next populated m rotamer (?1=?60°) shows the opposite trend of more downfield C?1 chemical shift by 1.23 ppm. These significantly different methyl 13C chemical shifts exist despite the likelihood of partial rotameric averaging at ambient temperature. We show that these conformation-dependent methyl 13C chemical shifts can be utilized for sidechain structure determination once the methyl 13C resonances are accurately measured by double-quantum (DQ) filtered 2D correlation experiments, most notably the dipolar DQ to single-quantum (SQ) correlation technique. The advantage of the DQ-SQ correlation experiment over simple 2D SQ – SQ correlation experiments is demonstrated on the transmembrane peptide of the influenza A M2 proton channel. The methyl chemical shifts led to predictions of the sidechain rotameric states for several Val and Leu residues in this tetrameric helical bundle. The predicted Val rotamers were further verified by dipolar correlation experiments that directly measure the ?1 torsion angles. It was found that the chemical-shift predicted sidechain conformations are fully consistent with the direct torsion angle results; moreover, the methyl 13C chemical shifts are sensitive to ~5° changes in the ?1 torsion angle due to drug binding. PMID:19441789

  9. Solid-state 13C-NMR spectroscopy shows that the xyloglucans in the primary cell walls of mung bean (Vigna radiata L.) occur in different domains: a new model for xyloglucan-cellulose interactions in the cell wall.

    PubMed

    Bootten, Tracey J; Harris, Philip J; Melton, Laurence D; Newman, Roger H

    2004-03-01

    Xyloglucans (XG) with different mobilities were identified in the primary cell walls of mung beans (Vigna radiata L.) by solid-state 13C-NMR spectroscopy. To improve the signal:noise ratios compared with unlabelled controls, Glc labelled at either C-1 or C-4 with 13C-isotope was incorporated into the cell-wall polysaccharides of mung bean hypocotyls. Using cell walls from seedlings labelled with d-[1-13C]glucose and, by exploiting the differences in rotating-frame and spin-spin proton relaxation, a small signal was detected which was assigned to Xyl of XGs with rigid glucan backbones. After labelling seedlings with d-[4-13C]glucose and using a novel combination of spin-echo spectroscopy with proton spin relaxation-editing, signals were detected that had 13C-spin relaxations and chemical shifts which were assigned to partly-rigid XGs surrounded by mobile non-cellulosic polysaccharides. Although quantification of these two mobility types of XG was difficult, the results indicated that the partly-rigid XGs were predominant in the cell walls. The results lend support to the postulated new cell-wall models in which only a small proportion of the total surface area of the cellulose microfibrils has XG adsorbed on to it. In these new models, the partly-rigid XGs form cross-links between adjacent cellulose microfibrils and/or between cellulose microfibrils and other non-cellulosic polysaccharides, such as pectic polysaccharides. PMID:14966211

  10. 13 C solid-state NMR study of the 13 C-labeled peptide, (E)8 GGLGGQGAG(A)6 GGAGQGGYGG as a model for the local structure of Nephila clavipes dragline silk (MaSp1) before and after spinning.

    PubMed

    Yazawa, Koji; Yamaguchi, Erika; Knight, David; Asakura, Tetsuo

    2012-06-01

    We prepared the water soluble model peptide, (E)(8) GGLGGQGAG(A)(6) GGAGQGGYGG, to throw light on the local structure of spidroin 1 (MaSpl) protein in spider dragline silk of Nephila clavipes before and after spinning. Solution (13) C NMR showed that the conformation of the peptide in aqueous solution was essentially random coil. Solid-state NMR was used to follow conformation-dependent (13) C chemical shifts in (13) C selectively labeled versions of the peptide. The peptide lyophilized from an aqueous solution at neutral pH (hereafter referred to as "without acid treatment)"was used to mimic the state of the spidroin stored in the spider's silk gland while the peptide precipitated from the acidic solution ("with acid treatment") was used to simulate the role of acid treatment in inducing conformation change in the natural spinning process. In without acid treatment, the fraction of random coil conformation was lowest in the N-terminal region (residues 15-18) when compared with the C-terminus. The conformational change produced by the acid treatment occurred in the sequence, G(15) AG(A)(6) GGAG(27), interposed between pairs of Gly residues pairs, Gly(12,13), and Gly(29,30). The acid treated peptide showed a remarkable decrease in the fraction of random coil conformation from A(20) to A(23) in the poly-Ala region when compared with the peptide without acid treatment. These observations taken together suggest that the peptide can be used as a model for studying the localization of the conformation change in spider silk fibroin in the natural spinning and the role of acid treatment in this process. PMID:21913180

  11. The role of irregular unit, GAAS, on the secondary structure of Bombyx mori silk fibroin studied with 13C CP/MAS NMR and wide-angle X-ray scattering

    PubMed Central

    Asakura, Tetsuo; Sugino, Rena; Okumura, Tatsushi; Nakazawa, Yasumoto

    2002-01-01

    Bombyx mori silk fibroin is a fibrous protein whose fiber is extremely strong and tough, although it is produced by the silkworm at room temperature and from an aqueous solution. The primary structure is mainly Ala-Gly alternative copolypeptide, but Gly-Ala-Ala-Ser units appear frequently and periodically. Thus, this study aims at elucidating the role of such Gly-Ala-Ala-Ser units on the secondary structure. The sequential model peptides containing Gly-Ala-Ala-Ser units selected from the primary structure of B. mori silk fibroin were synthesized, and their secondary structure was studied with 13C CP/MAS NMR and wide-angle X-ray scattering. The 13C isotope labeling of the peptides and the 13C conformation-dependent chemical shifts were used for the purpose. The Ala-Ala units take antiparallel ?-sheet structure locally, and the introduction of one Ala-Ala unit in (Ala-Gly)15 chain promotes dramatical structural changes from silk I (repeated ?-turn type II structure) to silk II (antiparallel ?-sheet structure). Thus, the presence of Ala-Ala units in B. mori silk fibroin chain will be one of the inducing factors of the structural transition for silk fiber formation. The role of Tyr residue in the peptide chain was also studied and clarified to induce "locally nonordered structure." PMID:12142441

  12. X-ray Crystallographic, Scanning Microprobe X-ray Diffraction, and Cross-Polarized/Magic Angle Spinning [superscript 13]C NMR Studies of the Structure of Cellulose III[subscript II

    SciTech Connect

    Wada, Masahisa; Heux, Laurent; Nishiyama, Yoshiharu; Langan, Paul; (U of Tokyo); (CNRS-CRMD); (LANL)

    2009-03-16

    The X-ray crystallographic structure of cellulose III{sub II} is characterized by disorder; the unit cell (space group P2{sub 1}; a = 4.45 {angstrom}, b = 7.64 {angstrom}, c = 10.36 {angstrom}, {alpha} = {beta} = 90{sup o}, {gamma} = 106.96{sup o}) is occupied by one chain that is the average of statistically disordered antiparallel chains. {sup 13}C CP/MAS NMR studies reveal the presence of three distinct molecular conformations that can be interpreted as a mixture of two different crystal forms, one equivalent to cellulose III{sub I}, and another with two independent glucosyl conformations in the asymmetric unit. Both X-ray crystallographic and {sup 13}C NMR spectroscopic results are consistent with an aggregated microdomain structure for cellulose III{sub II}. This structure can be generated from a new crystal form (space group P2{sub 1}; a = 4.45 {angstrom}, b = 14.64 {angstrom}, c = 10.36 {angstrom}, {alpha} = {beta} = 90{sup o}, {gamma} = 90.05{sup o}; two crystallographically independent and antiparallel chains; gt hydroxymethyl groups) by multiple dislocation defects. These defects produce microdomains of the new crystal form and cellulose III{sub I} that scanning microprobe diffraction studies show are distributed consistently through the cellulose III{sub II} fiber.

  13. Determining Actinobacillus succinogenes metabolic pathways and fluxes by NMR and GC-MS analyses of 13C-labeled metabolic product isotopomers

    Microsoft Academic Search

    James B. McKinlay; Yair Shachar-Hill; J. Gregory Zeikus; Claire Vieille

    2007-01-01

    Actinobacillus succinogenes is a promising candidate for industrial succinate production. However, in addition to producing succinate, it also produces formate and acetate. To understand carbon flux distribution to succinate and alternative products we fed A. succinogenes [1-13C]glucose and analyzed the resulting isotopomers of excreted organic acids, proteinaceous amino acids, and glycogen monomers by gas chromatography-mass spectrometry and nuclear magnetic resonance

  14. Vibrational (FT-IR and FT-Raman), electronic (UV-Vis), NMR (1H and 13C) spectra and reactivity analyses of 4,5-dimethyl-o-phenylenediamine

    NASA Astrophysics Data System (ADS)

    Atac, Ahmet; Karaca, Caglar; Gunnaz, Salih; Karabacak, Mehmet

    2014-09-01

    The structure of 4,5-dimethyl-o-phenylenediamine (C8H12N2, DMPDA) was investigated on the basis of spectroscopic data and theoretical calculations. The sterochemical structure was determined by FT-IR, FT-Raman, UV, 1H and 13C NMR spectra. An experimental study and a theoretical analysis were associated by using the B3LYP method with Gaussian09 package program. FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm-1 and 4000-10 cm-1, respectively. The vibrational spectra were calculated by DFT method and the fundamental vibrations were assigned on the basis of the total energy distribution (TED), calculated with scaled quantum mechanics (SQM) method with Parallel Quantum Solutions (PQS) program. The UV absorption spectrum of the compound that dissolved in ethanol solution were recorded in the range of 190-400 nm. Total density of state (TDOS) and partial density of state (PDOS) of the DMPDA in terms of HOMOs and LUMOs were calculated and analyzed. Chemical shifts were reported in ppm relative to tetramethylsilane (TMS) for 1H and 13C NMR spectra. The compound was dissolved in dimethyl sulfoxide (DMSO). Also, 1H and 13C chemical shifts calculated using the gauge independent atomic orbital (GIAO) method. Mullikan atomic charges and other thermo-dynamical parameters were investigated with the help of B3LYP (DFT) method using 6-311++G** basis set. On the basis of the thermodynamic properties of the title compound at different temperatures have been carried out, revealing the correlations between heat capacity (C), entropy (S), enthalpy changes (H) and temperatures. The optimized bond lengths, bond angles, chemical shifts and vibrational wavenumbers showed the best agreement with the experimental results.

  15. Vibrational (FT-IR and FT-Raman), electronic (UV-Vis), NMR (1H and 13C) spectra and reactivity analyses of 4,5-dimethyl-o-phenylenediamine.

    PubMed

    Atac, Ahmet; Karaca, Caglar; Gunnaz, Salih; Karabacak, Mehmet

    2014-09-15

    The structure of 4,5-dimethyl-o-phenylenediamine (C8H12N2, DMPDA) was investigated on the basis of spectroscopic data and theoretical calculations. The sterochemical structure was determined by FT-IR, FT-Raman, UV, 1H and 13C NMR spectra. An experimental study and a theoretical analysis were associated by using the B3LYP method with Gaussian09 package program. FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm(-1) and 4000-10 cm(-1), respectively. The vibrational spectra were calculated by DFT method and the fundamental vibrations were assigned on the basis of the total energy distribution (TED), calculated with scaled quantum mechanics (SQM) method with Parallel Quantum Solutions (PQS) program. The UV absorption spectrum of the compound that dissolved in ethanol solution were recorded in the range of 190-400 nm. Total density of state (TDOS) and partial density of state (PDOS) of the DMPDA in terms of HOMOs and LUMOs were calculated and analyzed. Chemical shifts were reported in ppm relative to tetramethylsilane (TMS) for 1H and 13C NMR spectra. The compound was dissolved in dimethyl sulfoxide (DMSO). Also, 1H and 13C chemical shifts calculated using the gauge independent atomic orbital (GIAO) method. Mullikan atomic charges and other thermo-dynamical parameters were investigated with the help of B3LYP (DFT) method using 6-311++G** basis set. On the basis of the thermodynamic properties of the title compound at different temperatures have been carried out, revealing the correlations between heat capacity (C), entropy (S), enthalpy changes (H) and temperatures. The optimized bond lengths, bond angles, chemical shifts and vibrational wavenumbers showed the best agreement with the experimental results. PMID:24813280

  16. Complete NMR spectral assignments of siloxanol based copolycarbonate including the configurational copolymer structure and the determination of each monomer conversion

    NASA Astrophysics Data System (ADS)

    Lim, Sung-Chul; Kim, Seong-Woo; Jung, Min-Hwan; Cho, Myo-kyung; Kim, Jong-Hoon; Cho, Hye-Sung; Ok, Jong-Hwa

    2008-08-01

    Siloxanol based copolycarbonate(SicoPC) of which the constitutional monomers are diphenyl carbonate, bisphenol A, and polydimethylsiloxanol(PDMS), was prepared by melt transesterification polymerization. The objective was to investigate the monomer conversion ratio for each monomer and the configurational structure of the SicoPC. A laboratory scale 5L reactor was used in the siloxanol preparation where the reactor jacket oil temperature was kept constant at 230 °C throughout the first and second polymerization phases. The reaction pressure was varied. For the first phase, the pressure was dropped from the atmospheric pressure 1000-200 mbar during the target reaction time of 30 min to remove the byproduct phenol. The second phase, the full vacuum pressure of was maintained for the second 30-min polymerization phase. An hour of reaction under such a condition gave a product of a highly viscous melt, of which the number average molecular weight read approximately 3000 g/mol. Complete NMR spectral assignments of the obtained melt (expected to be SicoPC) were made using both 1H and 13C, followed by 2D NMR spectroscopy. The measurements confirmed that the obtained melt was indeed the expected SicoPC; the conversion ratio of each monomer, BPA, DPC and PDMS were 100%, 99.5% and 86%, respectively. Furthermore, the HMBC (heteronuclear multiple quantum coherence) experiment confirmed the most important fact in determining the configurational structure of a SicoPC - all the PDMS monomers were located at the end chain of SicoPC.

  17. Molecular structure, spectroscopic (FT-IR, FT-Raman, 13C and 1H NMR, UV), polarizability and first-order hyperpolarizability, HOMO and LUMO analysis of 4'-methylbiphenyl-2-carbonitrile.

    PubMed

    Karabacak, Mehmet; Yilan, Erkan

    2012-02-15

    In the present study, the molecular structure, vibrational and electronic transition, isotropic chemical shifts analysis of 4'-methylbiphenyl-2-carbonitrile were presented using experimental techniques (FT-IR, FT-Raman, NMR and UV) and quantum chemical calculations. FT-IR and FT-Raman spectra in solid state were observed in the region 4000-400cm(-1) and 3500-50cm(-1), respectively. The ultraviolet absorption spectrum of studied compound that dissolved in ethanol was examined in the range of 200-400nm. The (1)H and (13)C NMR spectra were recorded in DMSO solution. To determine lowest-energy molecular conformation of the title molecule, the selected torsion angle is varied every 10° and molecular energy profile is calculated from 0° to 360°. The molecular structure and spectroscopic data of the molecule in the ground state were computed by density functional theory (DFT) using 6-31++G(d,p) basis set. The complete assignments of all vibrational modes were performed on the basis of the total energy distributions (TED) of the vibrational modes, computed with scaled quantum mechanics (SQM) method. (13)C and (1)H isotropic chemical shifts were computed using the gauge-invariant atomic orbital (GIAO) method. Moreover, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies, absorption wavelength were performed by time-dependent DFT approach. The dipole moment, linear polarizability and first hyperpolarizability values were also computed. The linear polarizabilities and first hyper polarizabilities of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. Comparison of the calculated frequencies, NMR chemical shifts, absorption wavelengths with the experimental values revealed that DFT method produces good results. PMID:22185952

  18. GC(Retention Indices), GC-MS, and 13C NMR of Two Citral-Rich Cymbopogon Leaf Oils: C. Flexuosus and C. tortilis

    Microsoft Academic Search

    Josephine Ottavioli; Ange Bighelli; Joseph Casanova; Bui Thi Bang; Pham van Y

    2009-01-01

    Leaf oils of Cymbopogon flexuosus and Cymbopogon tortilis were submitted to combined analysis by CG(retention indices), Gas Chromatography Mass Spectrometry (GC-MS), and C Nuclear Magnetic Resonance (NMR). The composition was dominated by geranial (39.2% and 32.0%) and neral (24.1% and 19.1%). Cis- and trans-7-hydroxy-3,7-dimethyl-3,6-oxyoctanal (synonym: cis- and trans-tetrahydro-5-(1-hydroxy-1-methylethyl)-2-methyl-2-furanacetaldehyde) were identified by C NMR by comparison with literature data.

  19. Complete 1H, 13C, and 15N NMR resonance assignments and secondary structure of human glutaredoxin in the fully reduced form.

    PubMed Central

    Sun, C.; Holmgren, A.; Bushweller, J. H.

    1997-01-01

    Human glutaredoxin is a member of the glutaredoxin family, which is characterized by a glutathione binding site and a redox-active dithiol/disulfide in the active site. Unlike Escherichia coli glutaredoxin-1, this protein has additional cysteine residues that have been suggested to play a regulatory role in its activity. Human glutaredoxin (106 amino acid residues, M(r) = 12,000) has been purified from a pET expression vector with both uniform 15N labeling and 13C/15N double labeling. The combination of three-dimensional 15N-edited TOCSY, 15N-edited NOESY, HNCA, HN(CO)CA, and gradient sensitivity-enhanced HNCACB and HNCO spectra were used to obtain sequential assignments for residues 2-106 of the protein. The gradient-enhanced version of the HCCH-TOCSY pulse sequence and HCCH-COSY were used to obtain side chain 1H and 13C assignments. The secondary structural elements in the reduced protein were identified based on NOE information, amide proton exchange data, and chemical shift index data. Human glutaredoxin contains five helices extending approximately from residues 4-10, 24-36, 53-64, 83-92, and 94-104. The secondary structure also shows four beta-strands comprised of residues 15-19, 43-48, 71-75, 78-80, which form a beta-sheet almost identical to that found in E. coli glutaredoxin-1. Complete 1H, 13C, and 15N assignments and the secondary structure of fully reduced human glutaredoxin are presented. Comparison to the structures of other glutaredoxins is presented and differences in the secondary structure elements are discussed. PMID:9041640

  20. Towards the automatic analysis of NMR spectra: part 7. Assignment of 1H by employing both 1H and 1H/13C correlation spectra.

    PubMed

    Griffiths, Lee; Beeley, Howard H; Horton, Rob

    2008-09-01

    A reliable method of automatically assigning one-dimensional proton spectra is described. The method relies on the alignment of the proton spectrum with an associated heteronuclear single-quantum coherence (HSQC) spectrum, transferring the stoichiometry and couplings to the HSQC. The HSQC spectrum is then assigned using a linear assignment procedure in which a fitness function incorporating (1)H chemical shifts, (1)H couplings and (13)C shifts are employed. The method uniquely employs a sequential procedure in which only correlations of like stoichiometry are assigned at the same time. PMID:18561211

  1. Monomeric and dimeric structures analysis and spectroscopic characterization of 3,5-difluorophenylboronic acid with experimental (FT-IR, FT-Raman, 1H and 13C NMR, UV) techniques and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Karabacak, Mehmet; Kose, Etem; Atac, Ahmet; Asiri, Abdullah M.; Kurt, Mustafa

    2014-01-01

    The spectroscopic properties of 3,5-difluorophenylboronic acid (3,5-DFPBA, C6H3F2B(OH)2) were investigated by FT-IR, FT-Raman UV-Vis, 1H and 13C NMR spectroscopic techniques. FT-IR (4000-400 cm-1) and FT-Raman spectra (3500-10 cm-1) in the solid phase and 1H and 13C NMR spectra in DMSO solution were recorded. The UV spectra that dissolved in ethanol and water were recorded in the range of 200-400 nm for each solution. The structural and spectroscopic data of the molecule have been obtained for possible three conformers from DFT (B3LYP) with 6-311++G(d,p) basis set calculations. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. Hydrogen-bonded dimer of title molecule, optimized by counterpoise correction, was also studied B3LYP at the 6-311++G(d,p) level and the effects of molecular association through O-H⋯O hydrogen bonding have been discussed. 1H and 13C NMR chemical shifts were calculated by using the gauge-invariant atomic orbital (GIAO) method. The electronic properties, such as excitation energies, oscillator strength, wavelengths, HOMO and LUMO energies, were performed by time-dependent density functional theory (TD-DFT) results complements with the experimental findings. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (OPDOS) diagrams analysis were presented. The effects due to the substitutions of boric acid group and halogen were investigated. The results of the calculations were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP), nonlinear optical properties (NLO) and thermodynamic features were performed.

  2. Model-free estimation of the effective correlation time for C-H bond reorientation in amphiphilic bilayers: (1)H-(13)C solid-state NMR and MD simulations.

    PubMed

    Ferreira, Tiago Mendes; Ollila, O H Samuli; Pigliapochi, Roberta; Dabkowska, Aleksandra P; Topgaard, Daniel

    2015-01-28

    Molecular dynamics (MD) simulations give atomically detailed information on structure and dynamics in amphiphilic bilayer systems on timescales up to about 1 ?s. The reorientational dynamics of the C-H bonds is conventionally verified by measurements of (13)C or (2)H nuclear magnetic resonance (NMR) longitudinal relaxation rates R1, which are more sensitive to motional processes with correlation times close to the inverse Larmor frequency, typically around 1-10 ns on standard NMR instrumentation, and are thus less sensitive to the 10-1000 ns timescale motion that can be observed in the MD simulations. We propose an experimental procedure for atomically resolved model-free estimation of the C-H bond effective reorientational correlation time ?e, which includes contributions from the entire range of all-atom MD timescales and that can be calculated directly from the MD trajectories. The approach is based on measurements of (13)C?R1 and R1? relaxation rates, as well as (1)H-(13)C dipolar couplings, and is applicable to anisotropic liquid crystalline lipid or surfactant systems using a conventional solid-state NMR spectrometer and samples with natural isotopic composition. The procedure is demonstrated on a fully hydrated lamellar phase of 1-palmitoyl-2-oleoyl-phosphatidylcholine, yielding values of ?e from 0.1 ns for the methyl groups in the choline moiety and at the end of the acyl chains to 3 ns for the g1 methylene group of the glycerol backbone. MD simulations performed with a widely used united-atom force-field reproduce the ?e-profile of the major part of the acyl chains but underestimate the dynamics of the glycerol backbone and adjacent molecular segments. The measurement of experimental ?e-profiles can be used to study subtle effects on C-H bond reorientational motions in anisotropic liquid crystals, as well as to validate the C-H bond reorientation dynamics predicted in MD simulations of amphiphilic bilayers such as lipid membranes. PMID:25638007

  3. Synthesis, spectral (IR, UV-Vis and variable temperature NMR) characterization and crystal structure of (N-benzyl-N-furfuryldithicarbamato-S,S?)(thiocyanato-N)(triphenylphosphine)nickel(II)

    NASA Astrophysics Data System (ADS)

    Valarmathi, P.; Thirumaran, S.; Sarmal, Lovely; Kant, Rajni

    2014-08-01

    Planar (N-benzyl-N-furfuryldithiocarbamato-S,S?)(thiocyanato-N)(triphenylphospine)nickel(II), [Ni(bfdtc)(NCS)(PPh3)], (1) was prepared from bis(N-benzyl-N-furfuryldithiocarbamato-S,S?)nickel(II), [Ni(bfdtc)2], (2) and characterized by elemental analysis, cyclic voltammetry, electronic, IR and variable temperature 1H and 13C NMR spectra. For complex 1, the thioureide vCsbnd N value is shifted to higher wavenumber compared to 2 and N13CS2 carbon signal observed for 1 is additionally shielded compared to the parent complex 2, suggesting increased strength of the thioureide bond due to the presence of the ?-accepting phosphine. In the room temperature 13C NMR spectrum of 1, two pseudo doublets are observed in the aliphatic region. Variable temperature 13C NMR spectral studies suggest that the fast thiocyanate exchange appears to be responsible for the appearance of pseudo doublets. Single crystal X-ray structural analysis of 1 and 2 confirm the presence of four coordinated nickel in a distorted square planar arrangement with the NiS2PN and NiS4 chromophores, respectively. The Nisbnd S bonds are symmetric in 2 (2.1914(14) and 2.2073(13) Å). But significant asymmetry in Nisbnd S bond distances was observed in 1 (2.2202(8) Å and 2.1841 Å). This observation clearly supports the less effective trans effect of SCN- over PPh3. Cyclic voltammetric studies revealed easier reduction of nickel(II) to nickel(I) in complex 1 compared to 2.

  4. Automics: an integrated platform for NMR-based metabonomics spectral processing and data analysis

    PubMed Central

    Wang, Tao; Shao, Kang; Chu, Qinying; Ren, Yanfei; Mu, Yiming; Qu, Lijia; He, Jie; Jin, Changwen; Xia, Bin

    2009-01-01

    Background Spectral processing and post-experimental data analysis are the major tasks in NMR-based metabonomics studies. While there are commercial and free licensed software tools available to assist these tasks, researchers usually have to use multiple software packages for their studies because software packages generally focus on specific tasks. It would be beneficial to have a highly integrated platform, in which these tasks can be completed within one package. Moreover, with open source architecture, newly proposed algorithms or methods for spectral processing and data analysis can be implemented much more easily and accessed freely by the public. Results In this paper, we report an open source software tool, Automics, which is specifically designed for NMR-based metabonomics studies. Automics is a highly integrated platform that provides functions covering almost all the stages of NMR-based metabonomics studies. Automics provides high throughput automatic modules with most recently proposed algorithms and powerful manual modules for 1D NMR spectral processing. In addition to spectral processing functions, powerful features for data organization, data pre-processing, and data analysis have been implemented. Nine statistical methods can be applied to analyses including: feature selection (Fisher's criterion), data reduction (PCA, LDA, ULDA), unsupervised clustering (K-Mean) and supervised regression and classification (PLS/PLS-DA, KNN, SIMCA, SVM). Moreover, Automics has a user-friendly graphical interface for visualizing NMR spectra and data analysis results. The functional ability of Automics is demonstrated with an analysis of a type 2 diabetes metabolic profile. Conclusion Automics facilitates high throughput 1D NMR spectral processing and high dimensional data analysis for NMR-based metabonomics applications. Using Automics, users can complete spectral processing and data analysis within one software package in most cases. Moreover, with its open source architecture, interested researchers can further develop and extend this software based on the existing infrastructure. PMID:19291281

  5. Improvement of 13C and 15N CPMAS NMR spectra of bulk soils, particle size fractions and organic material by treatment with 10% hydrofluoric acid

    Microsoft Academic Search

    M. W. I. SCHMIDT; H. KNICKER; P. G. HATCHER; I. KOGEL-KNABNER

    1997-01-01

    Summary The small organic matter content of mineral soils makes it difficult to obtain I3C and 15N nuclear magnetic resonance (NMR) spectra with acceptable signal-to-noise ratios. Subjecting such samples to hydrofluoric acid removes mineral matter and leads to a relative increase in organic material. The effect of treatment with 10% hydrofluoric acid on bulk chemical composition and resolution of solid-state

  6. Successful combination of computationally inexpensive GIAO 13C NMR calculations and artificial neural network pattern recognition: a new strategy for simple and rapid detection of structural misassignments.

    PubMed

    Sarotti, Ariel M

    2013-08-01

    GIAO NMR chemical shift calculations coupled with trained artificial neural networks (ANNs) have been shown to provide a powerful strategy for simple, rapid and reliable identification of structural misassignments of organic compounds using only one set of both computational and experimental data. The geometry optimization, usually the most time-consuming step in the overall procedure, was carried out using computationally inexpensive methods (MM+, AM1 or HF/3-21G) and the NMR shielding constants at the affordable mPW1PW91/6-31G(d) level of theory. As low quality NMR prediction is typically obtained with such protocols, the decision making was foreseen as a problem of pattern recognition. Thus, given a set of statistical parameters computed after correlation between experimental and calculated chemical shifts the classification was done using the knowledge derived from trained ANNs. The training process was carried out with a set of 200 molecules chosen to provide a wide array of chemical functionalities and molecular complexity, and the results were validated with a set of 26 natural products that had been incorrectly assigned along with their 26 revised structures. The high prediction effectiveness observed makes this method a suitable test for rapid identification of structural misassignments, preventing not only the publication of wrong structures but also avoiding the consequences of such a mistake. PMID:23779148

  7. Deactivation of HDT catalysts by formation of silica gels from silicone oil. Characterization of spent catalysts from HDT of coker naphtha using [sup 29]Si and [sup 13]C CP/MAS NMR

    SciTech Connect

    Kellberg, L.; Jakobsen, H.J. (Univ. of Aarhus (Germany)); Zeuthen, P. (Haldor Topsoe Research Labs., Lyngby (Germany))

    1993-09-01

    Catalysts used for hydrotreating of coker naphtha are found to deactivate very quickly because of deposition of Si-containing species on their surface. These species originate from the silicone oil (polydimethylsiloxane) added to the coker unit in order to suppress foaming during the coking process. Six samples of a spent catalyst from a HDT reactor have been analyzed by [sup 29]Si MAS, [sup 29]Si CP/MAS, and [sup 13]C CP/MAS NMR spectroscopy. From these studies it is concluded that the silicone oil in the naphtha feed is transformed (oxidized) to modified silica gels, i.e., silica with a partly methylated surface, under the operating conditions of the catalyst. Physi- or chemisorption of the silica gels on the catalyst explains the fast irreversible loss of activity during HDT of coker naphtha. 23 refs., 3 figs., 2 tabs.

  8. Dynamic 13C NMR studies of ligand exchange in linear (d10) silver(I) and gold(I) and square-planar (d8) rhodium(I) homoleptic metal carbonyl cations in superacidic media.

    PubMed

    von Ahsen, B; Bach, C; Balzer, G; Bley, B; Bodenbinder, M; Hägele, G; Willner, H; Aubke, F

    2005-07-01

    The dynamic CO exchange of the monovalent metal carbonyl cations [Ag(13CO)]+, [Au(13CO)2]+-Au(13CO) SO3F and [Rh(12CO)4-x(13CO)x]+ (x < or = 1) in superacidic solutions was studied by variable-temperature 13C NMR methods. The exchange rates are strongly dependent on the acidity of the solvent, the concentration of metal carbonyl cations and temperature. Whereas a suitable exchange rate of the Ag(I) system is only accessible in magic acid (HSO3F-SbF5), the more stable Au(I) and Rh(I) systems were studied in the less acidic fluorosulfuric acid. Selected solutions of Ag(I), Rh(I) and Au(I) yielded activation barriers deltaG* of 42.7, 43.5, and 56.2 kJ mol(-1) respectively. PMID:15861386

  9. NMR study of non-structural proteins-part II: (1)H, (13)C, (15)N backbone and side-chain resonance assignment of macro domain from Venezuelan equine encephalitis virus (VEEV).

    PubMed

    Makrynitsa, Garyfallia I; Ntonti, Dioni; Marousis, Konstantinos D; Tsika, Aikaterini C; Lichière, Julie; Papageorgiou, Nicolas; Coutard, Bruno; Bentrop, Detlef; Spyroulias, Georgios A

    2014-10-01

    Macro domains consist of 130-190 amino acid residues and appear to be highly conserved in all kingdoms of life. Intense research on this field has shown that macro domains bind ADP-ribose and other similar molecules, but their exact function still remains intangible. Macro domains are highly conserved in the Alphavirus genus and the Venezuelan equine encephalitis virus (VEEV) is a member of this genus that causes fatal encephalitis to equines and humans. In this study we report the high yield recombinant expression and preliminary solution NMR study of the macro domain of VEEV. An almost complete sequence-specific assignment of its (1)H, (15)N and (13)C resonances was obtained and its secondary structure predicted by TALOS+. The protein shows a unique mixed ?/?-fold. PMID:25291978

  10. Photochemically induced nuclear spin polarization in reaction centers of photosystem II observed by 13C-solid-state NMR reveals a strongly asymmetric electronic structure of the P680.+ primary donor chlorophyll

    PubMed Central

    Matysik, Jörg; Alia; Gast, Peter; van Gorkom, Hans J.; Hoff, Arnold J.; de Groot, Huub J. M.

    2000-01-01

    We report 13C magic angle spinning NMR observation of photochemically induced dynamic nuclear spin polarization (photo- CIDNP) in the reaction center (RC) of photosystem II (PS2). The light-enhanced NMR signals of the natural abundance 13C provide information on the electronic structure of the primary electron donor P680 (chlorophyll a molecules absorbing around 680 nm) and on the pz spin density pattern in its oxidized form, P680?. Most centerband signals can be attributed to a single chlorophyll a (Chl a) cofactor that has little interaction with other pigments. The chemical shift anisotropy of the most intense signals is characteristic for aromatic carbon atoms. The data reveal a pronounced asymmetry of the electronic spin density distribution within the P680?. PS2 shows only a single broad and intense emissive signal, which is assigned to both the C-10 and C-15 methine carbon atoms. The spin density appears shifted toward ring III. This shift is remarkable, because, for monomeric Chl a radical cations in solution, the region of highest spin density is around ring II. It leads to a first hypothesis as to how the planet can provide itself with the chemical potential to split water and generate an oxygen atmosphere using the Chl a macroaromatic cycle. A local electrostatic field close to ring III can polarize the electronic charge and associated spin density and increase the redox potential of P680 by stabilizing the highest occupied molecular orbital, without a major change of color. This field could be produced, e.g., by protonation of the keto group of ring V. Finally, the radical cation electronic structure in PS2 is different from that in the bacterial RC, which shows at least four emissive centerbands, indicating a symmetric spin density distribution over the entire bacteriochlorophyll macrocycle. PMID:10944191

  11. Backbone and Ile-?1, Leu, Val Methyl 1H, 13C and 15N NMR chemical shift assignments for human interferon-stimulated gene 15 protein

    SciTech Connect

    Yin, Cuifeng; Aramini, James M.; Ma, LiChung; Cort, John R.; Swapna, G.V.T.; Krug, R. M.; Montelione, Gaetano

    2011-10-01

    Human interferon-stimulated gene 15 protein (ISG15), also called ubiquitin cross-reactive protein (UCRP), is the first identified ubiquitin-like protein containing two ubiquitin-like domains fused in tandem. The active form of ISG15 is conjugated to target proteins via the C-terminal glycine residue through an isopeptide bond in a manner similar to ubiquitin. The biological role of ISG15 is strongly associated with the modulation of cell immune function, and there is mounting evidence suggesting that many viral pathogens evade the host innate immune response by interfering with ISG15 conjugation to both host and viral proteins in a variety of ways. Here we report nearly complete backbone 1HN, 15N, 13CO, and 13Ca, as well as side chain 13Cb, methyl (Ile-d1, Leu, Val), amide (Asn, Gln), and indole NH (Trp) NMR resonance assignments for the 157-residue human ISG15 protein. These resonance assignments provide the basis for future structural and functional solution NMR studies of the biologically important human ISG15 protein.

  12. Degradation of mangrove tissues by arboreal termites (Nasutitermes acajutlae) and their role in the mangrove C cycle (Puerto Rico): Chemical characterization and organic matter provenance using bulk ?13C, C/N, alkaline CuO oxidation-GC/MS, and solid-state 13C NMR

    NASA Astrophysics Data System (ADS)

    Vane, Christopher H.; Kim, Alexander W.; Moss-Hayes, Vicky; Snape, Colin E.; Diaz, Miguel Castro; Khan, Nicole S.; Engelhart, Simon E.; Horton, Benjamin P.

    2013-08-01

    Arboreal termites are wood decaying organisms that play an important role in the first stages of C cycling in mangrove systems. The chemical composition of Rhizophora mangle, Avicennia germinans, and Laguncularia racemosa leaf, stem, and pneumatophore tissues as well as associated sediments was compared to that of nests of the termite Nasutitermes acajutlae. Nests gave ?13C values of -26.1 to -27.2‰ (±0.1) and C/N of 43.3 (±2.0) to 98.6 (±16.2) which were similar to all stem and pneumatophores but distinct from mangrove leaves or sediments. Organic matter processed by termites yielded lignin phenol concentrations (?, lambda) that were 2-4 times higher than stem or pneumatophores and 10-20 times higher than that of leaves or sediments, suggesting that the nests were more resistant to biodegradation than the mangrove vegetation source. 13C NMR revealed that polysaccharide content of mangrove tissues (50-69% C) was higher than that of the nests (46-51% C). Conversely, lignin accounted for 16.2-19.6% C of nest material, a threefold increase relative to living mangrove tissues; a similar increase in aromatic methoxyl content was also observed in the nests. Lipids (aliphatic and paraffinic moieties) were also important but rather variable chemical components of all three mangrove species, representing between 13.5 and 28.3% of the C content. Termite nests contained 3.14 Mg C ha-1 which represents approximately 2% of above ground C storage in mangroves, a value that is likely to increase upon burial due to their refractory chemical composition.

  13. Probing Sequence-specific DNA Flexibility in A-tracts and Pyrimidine-purine Steps by NMR 13C Relaxation and MD Simulations

    PubMed Central

    Nikolova, Evgenia N.; Bascom, Gavin D.; Andricioaei, Ioan; Al-Hashimi, Hashim M.

    2013-01-01

    Sequence-specific DNA flexibility plays a key role in a variety of cellular interactions that are critical for gene packaging, expression, and regulation. Yet, few studies have experimentally explored the sequence dependence of DNA dynamics that occur on biologically relevant timescales. Here, we use nuclear magnetic resonance (NMR) carbon spin relaxation combined with molecular dynamics (MD) simulations to examine the picosecond to nanosecond dynamics in a variety of dinucleotide steps as well as in varying length homopolymeric An•Tn repeats (An-tracts, n = 2, 4 and 6) that exhibit unusual structural and mechanical properties. We extend the NMR spin relaxation timescale sensitivity deeper into the nanosecond regime by using glycerol and a longer DNA duplex to slow down overall tumbling. Our studies reveal a structurally unique A-tract core (for n > 3) that is uniformly rigid, flanked by junction steps that show increasing sugar flexibility with A-tract length. High sugar mobility is observed at pyrimidine residues at the A-tract junctions, which is encoded at the dinucleotide level (CA, TG and CG steps) and increases with A-tract length. The MD simulations reproduce many of these trends, particularly the overall rigidity of A-tract base and sugar sites, and suggest that the sugar-backbone dynamics could involve transitions in sugar pucker and phosphate backbone BI?BII equilibria. Our results reinforce an emerging view that sequence-specific DNA flexibility can be imprinted in dynamics occurring deep within the nanosecond time regime that is difficult to characterize experimentally at the atomic level. Such large amplitude sequence-dependent backbone fluctuations might flag the genome for specific DNA recognition. PMID:23035755

  14. Tumbling motions of NH2(CH3)2 ions in [NH2(CH3)2]2ZnCl4 studied using 1H MAS NMR and 13C CP/MAS NMR

    NASA Astrophysics Data System (ADS)

    Kim, Nam Hee; Choi, Jae Hun; Lim, Ae Ran

    2014-12-01

    The structure and the phase transition temperatures of [NH2(CH3)2]2ZnCl4 were determined using X-ray diffraction and DSC, respectively. The temperature dependence of chemical shifts and the spin-lattice relaxation time T1? in the rotating frame were measured for the 1H and 13C nuclei in [NH2(CH3)2]2ZnCl4. From these results, it was observed that the structural change by chemical shifts does not occur with temperature. However, T1? for 1H and 13C in [NH2(CH3)2]2ZnCl4 showed a minimum, and it is apparent that both T1? values are governed by the same tumbling motions. The activation energies of tumbling motions for 1H and 13C are nearly the same owing to the connection between CH3 and NH2 ions in the [NH2(CH3)2]+ group.

  15. The electronic structure of the primary electron donor of reaction centers of purple bacteria at atomic resolution as observed by photo-CIDNP 13C NMR

    PubMed Central

    Daviso, Eugenio; Prakash, Shipra; Alia, A.; Gast, Peter; Neugebauer, Johannes; Jeschke, Gunnar; Matysik, Jörg

    2009-01-01

    Composed of the two bacteriochlorophyll cofactors, PL and PM, the special pair functions as the primary electron donor in bacterial reaction centers of purple bacteria of Rhodobacter sphaeroides. Under light absorption, an electron is transferred to a bacteriopheophytin and a radical pair is produced. The occurrence of the radical pair is linked to the production of enhanced nuclear polarization called photochemically induced dynamic nuclear polarization (photo-CIDNP). This effect can be used to study the electronic structure of the special pair at atomic resolution by detection of the strongly enhanced nuclear polarization with laser-flash photo-CIDNP magic-angle spinning NMR on the carotenoid-less mutant R26. In the electronic ground state, PL is strongly disturbed, carrying a slightly negative charge. In the radical cation state, the ratio of total electron spin densities between PL and PM is 2:1, although it is 2.5:1 for the pyrrole carbons, 2.2:1 for all porphyrinic carbons, and 4:1 for the pyrrole nitrogen. It is shown that the symmetry break between the electronic structures in the electronic ground state and in the radical cation state is an intrinsic property of the special pair supermolecule, which is particularly attributable to a modification of the structure of PL. The significant difference in electron density distribution between the ground and radical cation states is explained by an electric polarization effect of the nearby histidine. PMID:20018724

  16. NMR magnetic dipolar spectral density functions for two-dimensional lattice diffusion

    Microsoft Academic Search

    P. C. L. Stephenson; C. A. Sholl

    1993-01-01

    NMR magnetic dipolar spectral density functions are obtained for some lattice diffusion models for two-dimensional lattice diffusion and compared with the results for the BPP and continuum models. The systems considered are dipolar interactions between spins diffusing in a plane, and interactions between diffusing spins in a plane with fixed spins in a separate parallel plane. Numerical results and analytic

  17. Spin-counting NMR experiments for the spectral editing of structural motifs in solids.

    PubMed

    Deschamps, Michaël; Fayon, Franck; Hiet, Julien; Ferru, Geoffroy; Derieppe, Marc; Pellerin, Nadia; Massiot, Dominique

    2008-03-01

    Scalar couplings, recoupled or full dipolar interactions can be used to characterize multinuclear structural molecular motifs in solids, by counting the neighbouring spins in solid-state NMR, opening new ways for the differentiation of overlapping spectral responses which is a limiting factor in many high resolution experiments carried out on disordered systems. PMID:18292865

  18. Adducts of organotin(IV), tin(IV) and tin(II) halides with 1-methyl-imidazoline-2(3 H)-thione (Hmimt) and imidazoline-2(1,3 H)-thione (Himt). Synthesis, spectroscopic (IR, Mössbauer and 1H, 13C, 119Sn NMR) studies and in vitro antitumour activity

    Microsoft Academic Search

    Dimitra Kovala-Demertzi; Polymnia Tauridou; Umberto Russo; Marcel Gielen

    1995-01-01

    The reactions of 1-methyl-imidazoline-2(3H)-thione (Hmimt) and imidazoline-2(1,3H)-thione (Himt) with organotin(IV), tin(IV) and tin(II) halides were studied. Ten novel adducts were prepared and characterised by elemental analysis, conductivity measurements, IR, far-IR, 1H NMR, 13C NMR, 119Sn NMR and Mössbauer spectroscopy. The ligands behave as monodentate and exhibit sulfur coordination. The structure of the complexes, in the solid state, is discussed in

  19. Changes in Lignin and Polysaccharide Components in 13 Cultivars of Rice Straw following Dilute Acid Pretreatment as Studied by Solution-State 2D 1H-13C NMR

    PubMed Central

    Teramura, Hiroshi; Sasaki, Kengo; Oshima, Tomoko; Aikawa, Shimpei; Matsuda, Fumio; Okamoto, Mami; Shirai, Tomokazu; Kawaguchi, Hideo; Ogino, Chiaki; Yamasaki, Masanori; Kikuchi, Jun; Kondo, Akihiko

    2015-01-01

    A renewable raw material, rice straw is pretreated for biorefinery usage. Solution-state two-dimensional (2D) 1H-13 C hetero-nuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectroscopy, was used to analyze 13 cultivars of rice straw before and after dilute acid pretreatment, to characterize general changes in the lignin and polysaccharide components. Intensities of most (15 of 16) peaks related to lignin aromatic regions, such as p-coumarate, guaiacyl, syringyl, p-hydroxyphenyl, and cinnamyl alcohol, and methoxyl, increased or remained unchanged after pretreatment. In contrast, intensities of most (11 of 13) peaks related to lignin aliphatic linkages or ferulate decreased. Decreased heterogeneity in the intensities of three peaks related to cellulose components in acid-insoluble residues resulted in similar glucose yield (0.45–0.59 g/g-dry biomass). Starch-derived components showed positive correlations (r = 0.71 to 0.96) with glucose, 5-hydroxymethylfurfural (5-HMF), and formate concentrations in the liquid hydrolysates, and negative correlations (r = –0.95 to –0.97) with xylose concentration and acid-insoluble residue yield. These results showed the fate of lignin and polysaccharide components by pretreatment, suggesting that lignin aromatic regions and cellulose components were retained in the acid insoluble residues and starch-derived components were transformed into glucose, 5-HMF, and formate in the liquid hydrolysate. PMID:26083431

  20. Spectroscopic (IR, Raman, UV, 1H and 13C NMR) and microbiological studies of Fe(III), Ni(II), Cu(II), Zn(II) and Ag(I) picolinates

    NASA Astrophysics Data System (ADS)

    Kalinowska, M.; Borawska, M.; ?wis?ocka, R.; Piekut, J.; Lewandowski, W.

    2007-05-01

    The FT-IR, Raman spectra of picolinic acid as well as Fe(III), Zn(II), Cu(II), Ni(II) and Ag(I) picolinates were registered, assigned and compared. Some regularities in the spectra of studied picolinates within the regions: 1650-1340 cm -1 [ ?(CC) ar, ?as(COO -), ?s(COO -)]; 1300-1020 cm -1 [ ?(CH)]; 780-620 cm -1 [ ?(CH), ?(CCC)] were found. 1H and 13C NMR spectra for picolinic acid, Zn(II) and Ag(I) picolinates were recorded and studied as well. Moreover the UV spectra of picolinic and picolinates were registered and compared. The influence of Ag(I), Zn(II), Ni(II), Cu(II) and Fe(III) on the electronic system of picolinic acid was investigated. The microbiological activity of picolinates against two species of bacteria: Escherichia coli, Bacillus subtilis as well as two species of yeasts: Saccharomyces cerevisiae and Hansenula anomala was also studied.

  1. Comprehensive quantum chemical and spectroscopic (FTIR, FT-Raman, 1H, 13C NMR) investigations of (1,2-epoxyethyl)benzene and (1,2-epoxy-2-phenyl)propane

    NASA Astrophysics Data System (ADS)

    Arjunan, V.; Anitha, R.; Devi, L.; Mohan, S.; Yang, Haifeng

    2015-01-01

    Aromatic epoxides are causative factors for mutagenic and carcinogenic activity of polycyclic arenes. The 1,2- or 2,3-epoxy compounds are widely used to a considerable extent in the textile, plastics, pharmaceutical, cosmetics, detergent and photochemical industries. The FTIR and FT-Raman spectra of (1,2-epoxyethyl)benzene and (1,2-epoxy-2-phenyl)propane are recorded in the regions 4000-400 cm-1 and 4000-100 cm-1, respectively. The observed fundamentals are assigned to different normal modes of vibration. The structure of the compound has been optimised with B3LYP method using 6-311++G** and cc-pVTZ basis sets. The IR and Raman intensities are determined. The total electron density and molecular electrostatic potential surfaces of the molecule are constructed by using B3LYP/6-311++G(d,p) method to display electrostatic potential (electron + nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. Natural bond orbital analysis of the compounds has been performed to indicate the presence of intramolecular charge transfer. The 1H and 13C NMR chemical shifts of the molecules have been analysed.

  2. Examination of the structure in solid state of amino analogs of 4,4?-[1,5-pentanediylbis(oxy)]bisbenzonitrile by means of X-ray diffraction, 13C CP/MAS NMR, and theoretical calculations

    NASA Astrophysics Data System (ADS)

    Maciejewska, Dorota; Wolska, Irena; ?abi?ski, Jerzy

    2008-05-01

    A single crystal of X-ray diffraction structures is presented for 4,4'-[1,5-(3-oxapentanediylbis(amino))]bisbenzonitrile 2 and 4,4'-[1,5-( N-methyl-3-azapentane-diylbis(oxy))]bisbenzonitrile 3. The molecular structures of these derivatives differ especially in conformations of the central linker: in 2 this linker adopts a trans/ gauche conformation, whereas in 3 - a fully extended conformation. The N atoms in various positions of the aliphatic linker change dramatically the molecular packing mode of both bisnitriles. But in both cases the nitrile groups take part in intermolecular hydrogen bonds: a type of N sbnd H···N in 2 and of C sbnd H···N in 3. Various conformations of both molecules were reflected in 13C CP/MAS NMR spectra in solid state as single and double resonance patterns for 2 and 3, respectively. A preliminary anticancer assay against 60 cell lines of 3 reveals strong growth inhibition of leukemia, melanoma, and renal cancer cells.

  3. Development and validation of a RP-HPLC method for stability-indicating assay of gemifloxacin mesylate including identification of related substances by LC-ESI-MS/MS, 1H and 13C NMR spectroscopy.

    PubMed

    Rao, R Nageswara; Naidu, Ch Gangu; Prasad, K Guru; Narasimha, R

    2011-11-01

    A validated stability indicating RP-HPLC assay of gemifloxacin mesylate was developed by separating its related substances on an Inertsil-ODS3V-C18 (4.6 × 250 mm; 5 ?m) column using 0.1% trifluoroaceticacid (pH 2.5) and methanol as a mobile phase in a gradient elution mode at a flow rate of 1.0 mL/min at 27°C. The column effluents were monitored by a photodiode array detector set at 287 nm. The method was validated in terms of accuracy, precision and linearity as per ICH guidelines. Forced degradation of gemifloxacin (GFX) was carried out under acidic, basic, thermal, photolysis and peroxide conditions and the degradation products were separated and characterized by ESI-MS/MS, (1) H and (13) C NMR spectroscopy. The method was successfully applied to the analysis of bulk drugs and the recoveries of gemifloxacin and impurities were in the range of 97.60-102.90 and 96.99-102.10%, respectively. No previous reports were found in the literature on identification of degradation products of gemifloxacin. PMID:21370250

  4. A 13C and 1H NMR spectroscopic investigation of the structure of the iminium ion with a dipolar form in metal complexes of 2-N-substituted N-confused porphyrins.

    PubMed

    Chang, Wen-Pin; Lin, Wen-Chain; Chen, Jyh-Horung; Wang, Shin-Shin; Tung, Jo-Yu

    2012-11-21

    The crystal structures of chloro(2-aza-2-ethoxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N?N??) zinc(II) [Zn(2-NCH2COOC2H5NCTPP)Cl; 4], (2-aza-2-ethoxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N?N??) palladium(II) [Pd(2-NCH2COOC2H5NCTPP); 5], bromo(2-aza-2-ethoxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N?N??) manganese(III) [Mn(2-NCH2COOC2H5NCTPP)Br; 6], [2-aza-(3?-phenoxypropyl)-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N?N??] nickel(II) [Ni(2-NCH2CH2CH2OC6H5NCTPP); 7] and chloro(2-aza-2-methoxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N?N??) zinc(II) [Zn(2-NCH2COOCH3NCTPP)Cl; 8] have been established. The g value of 9.54, which was measured from the parallel polarization of the X-band EPR spectra in CHCl3 at 4 K, is consistent with the high spin mononuclear manganese(III) centre (S = 2) in 6. The magnitude of the axial (D) zero-field splitting (ZFS) for the mononuclear Mn(III) centre in 6 was determined approximately to be 1.63 cm(?1) by paramagnetic susceptibility measurements. The NMR spectroscopic investigation of the iminium ion with a dipolar canonical contribution to the metal complexes 5–7, Pd(2-NCH2C6H5NCTPP) (10) and Ni(2-NCH2C6H5NCTPP) (11) in CDCl3 is reported. A resonance between the dipolar canonical form II and covalent canonical form I exists for complexes 5–7, 10 and 11 in CDCl3. To develop the correlations between ?13C [C(3)], ?1H [H(3)] and the canonical form II in 5–7, 10 and 11, this work thoroughly examines the 13C and 1H NMR of N+=CH(Ar) fragment on seven metal complexes of 2-N substituted N-confused porphyrin. According to these results, the 13C [C(3)] and 1H [H(3)] chemical shifts of the N+=CH(Ar) fragment at 20 °C in CDCl3 are separately located at 152.6 ± 0.5 and 8.30 ± 0.15 ppm respectively for the iminium ion. This exists as a dipolar canonical form II for complexes 5–7, 10 and 11, and the N–CH(Ar) group appears at 121.1 ± 0.1 ppm and 6.35 ± 0.01 ppm, which is in a covalent canonical form I contribution to complexes 4 and 8. X-Ray diffraction data indicate that N(2)–C(3) = 1.315 ± 0.011 Å for the dipolar contribution of 5–7, 10–13, while N(2)–C(3) = 1.331 ± 0.008 Å for the covalent contribution of 4 and 8. PMID:23010770

  5. A Study of spectral integration and normalization in NMR-based metabonomic analyses

    Microsoft Academic Search

    Bobbie-Jo M. Webb-Robertson; David F. Lowry; Kristin H. Jarman; Sam J. Harbo; Quanxin Meng; Alfred F. Fuciarelli; Joel G. Pounds; K. Monica Lee

    2005-01-01

    Metabonomics involves the quantitation of the dynamic multivariate metabolic response of an organism to a pathological event or genetic modification [J.K. Nicholson, J.C. Lindon, E. Holmes, Xenobiotica 29 (1999) 1181–1189]. The analysis of these data involves the use of appropriate multivariate statistical methods; Principal Component Analysis (PCA) has been documented as a valuable pattern recognition technique for 1H NMR spectral

  6. Sensitivity gains, linearity, and spectral reproducibility in nonuniformly sampled multidimensional MAS NMR spectra of high dynamic range

    PubMed Central

    Suiter, Christopher L.; Paramasivam, Sivakumar; Hou, Guangjin; Sun, Shangjin; Rice, David; Hoch, Jeffrey C.; Rovnyak, David

    2014-01-01

    Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear 13C13C correlation spectra. We demonstrate on model compounds and on 1–73-(U-13C, 15N)/74–108-(U-15N) E. coli thioredoxin reassembly, that with appropriately constructed 50 % NUS schedules inherent sensitivity gains of 1.7–2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear 13C13C MAS correlation experiments that yield high-quality artifact-free datasets. PMID:24752819

  7. Characterization of polysulfone and polysulfone/vanillin microcapsules by 1H NMR spectroscopy, solid-state 13C CP/MAS-NMR spectroscopy, and N2 adsorption-desorption analyses.

    PubMed

    Peña, Brisa; de Ménorval, Louis-Charles; Garcia-Valls, Ricard; Gumí, Tània

    2011-11-01

    Textile detergent and softener industries have incorporated perfume microencapsulation technology to improve their products. Perfume encapsulation allows perfume protection until use and provides a long-lasting fragrance release. But, certain industrial microcapsules show low encapsulation capacity and low material stability. Polysulfone capsules have been already proposed to solve these drawbacks. Among them, PSf/Vanillin capsules were considered as a desirable system. They present both good material stability and high encapsulation capacity. However, several factors such as the final location of the perfume in the polymeric matrix, the aggregation state that it has in the capsule and its interaction with the capsule components have not been studied yet. These factors can provide vast information about the capsule performance and its improvement. With the aim to characterize these parameters, the physical and chemical properties of PSf/Vanillin capsules have been investigated by nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and N(2) adsorption-desorption measurements. AFM micrograph and N(2) isotherms confirm that the presence of vanillin modify the physical structure of PSf/Vanillin microcapsules as it is trapped in the capsule porosity. NMR results show that vanillin is present in solid state in PSf/Vanillin microcapsules. PMID:22008282

  8. Determination of second-order association constants by global analysis of 1H and 13C NMR chemical shifts. Application to the complexation of sodium fusidate and potassium helvolate by beta- and gamma-cyclodextrin.

    PubMed

    Al-Soufi, Wajih; Cabrer, Pedro Ramos; Jover, Aida; Budal, Rosane M; Tato, José Vázquez

    2003-01-01

    The host-guest interaction between the steroid antibiotics sodium fusidate and potassium helvolate as guests and the hosts beta- and gamma-cyclodextrin was studied by 13C and 1H NMR techniques. The analysis of chemical shifts of individual nuclei leads to inconsistent values of the association constants and fails generally in the case of mixtures of 1:1 and 1:2 stoichiometries. The problem of parameter correlation is identified and the global analysis of two or more nuclei is proposed as a very effective method for the detection of complexes of higher stoichiometries and for the precise determination of the involved association constants. A matrix formulation of global analysis and the determination of confidence intervals is described. An analytical solution of the cubic equation, necessary for the description of higher order complexes, is presented in detail and its use together with commercial fitting software is compared with dedicated implementations. gamma-Cyclodextrin forms with both studied steroids, sodium fusidate and potassium helvolate, 1:1 complexes with high values of the association constants, K(1)=(60+/-24)x10(3)lmol(-1), and K(2)=(22+/-9)x10(3)lmol(-1), respectively. To the contrary, beta-cyclodextrin forms 1:1 and 1:2 (guest:host) complexes with both steroids, with moderate K(1) and low K(2) values (K(1)=(0.74+/-0.13)x10(3)lmol(-1), K(2)=(0.210+/-0.075)x10(3)lmol(-1)), and (K(1)=(2.42+/-0.87)x10(3)lmol(-1), K(2)=(0.06+/-0.09)x10(3)lmol(-1)), respectively. PMID:12475722

  9. Focus: a robust workflow for one-dimensional NMR spectral analysis.

    PubMed

    Alonso, Arnald; Rodríguez, Miguel A; Vinaixa, Maria; Tortosa, Raül; Correig, Xavier; Julià, Antonio; Marsal, Sara

    2014-01-21

    One-dimensional (1)H NMR represents one of the most commonly used analytical techniques in metabolomic studies. The increase in the number of samples analyzed as well as the technical improvements involving instrumentation and spectral acquisition demand increasingly accurate and efficient high-throughput data processing workflows. We present FOCUS, an integrated and innovative methodology that provides a complete data analysis workflow for one-dimensional NMR-based metabolomics. This tool will allow users to easily obtain a NMR peak feature matrix ready for chemometric analysis as well as metabolite identification scores for each peak that greatly simplify the biological interpretation of the results. The algorithm development has been focused on solving the critical difficulties that appear at each data processing step and that can dramatically affect the quality of the results. As well as method integration, simplicity has been one of the main objectives in FOCUS development, requiring very little user input to perform accurate peak alignment, peak picking, and metabolite identification. The new spectral alignment algorithm, RUNAS, allows peak alignment with no need of a reference spectrum, and therefore, it reduces the bias introduced by other alignment approaches. Spectral alignment has been tested against previous methodologies obtaining substantial improvements in the case of moderate or highly unaligned spectra. Metabolite identification has also been significantly improved, using the positional and correlation peak patterns in contrast to a reference metabolite panel. Furthermore, the complete workflow has been tested using NMR data sets from 60 human urine samples and 120 aqueous liver extracts, reaching a successful identification of 42 metabolites from the two data sets. The open-source software implementation of this methodology is available at http://www.urr.cat/FOCUS. PMID:24354303

  10. Following Suberization in Potato Wound Periderm by Histochemical and Solid-State 13C Nuclear Magnetic Resonance Methods.

    PubMed Central

    Stark, R. E.; Sohn, W.; Pacchiano Jr, R. A.; Al-Bashir, M.; Garbow, J. R.

    1994-01-01

    The time course of suberization in wound periderm from potato (Solanum tuberosum L.) has been monitored by histochemical and high-resolution solid-state nuclear magnetic resonance (NMR) methods. Light microscopy conducted after selective staining of the lipid and double-bonded constituents shows that suberin is deposited at the outermost intact cell-wall surface during the first 7 d of wound healing; suberization forms a barrier to tissue infiltration at later times. Cross polarization-magic angle spinning 13C NMR spectra demonstrate the deposition of a polyester containing all major suberin functional groups after just 4 d of wound healing. Initially the suberin includes a large proportion of aromatic groups and fairly short aliphatic chains, but the spectral data demonstrate the growing dominance of long-chain species during the period 7 to 14 d after wounding. The results of preliminary 13C-labeling experiments with sodium [2-13C]acetate and DL-[1-13C]phenylalanine provide an excellent prospectus for future NMR-based studies of suberin biosynthesis. PMID:12232102

  11. Position-Specific Isotope Analysis of Xanthines: A (13)C Nuclear Magnetic Resonance Method to Determine the (13)C Intramolecular Composition at Natural Abundance.

    PubMed

    Diomande, Didier G; Martineau, Estelle; Gilbert, Alexis; Nun, Pierrick; Murata, Ariaki; Yamada, Keita; Watanabe, Naoharu; Tea, Illa; Robins, Richard J; Yoshida, Naohiro; Remaud, Gérald S

    2015-07-01

    The natural xanthines caffeine, theobromine, and theophylline are of major commercial importance as flavor constituents in coffee, cocoa, tea, and a number of other beverages. However, their exploitation for authenticity, a requirement in these commodities that have a large origin-based price-range, by the standard method of isotope ratio monitoring by mass spectrometry (irm-MS) is limited. We have now developed a methodology that overcomes this deficit that exploits the power of isotopic quantitative (13)C nuclear magnetic resonance (NMR) spectrometry combined with chemical modification of the xanthines to enable the determination of positional intramolecular (13)C/(12)C ratios (?(13)Ci) with high precision. However, only caffeine is amenable to analysis: theobromine and theophylline present substantial difficulties due to their poor solubility. However, their N-methylation to caffeine makes spectral acquisition feasible. The method is confirmed as robust, with good repeatability of the ?(13)Ci values in caffeine appropriate for isotope fractionation measurements at natural abundance. It is shown that there is negligible isotope fractionation during the chemical N-methylation procedure. Thus, the method preserves the original positional ?(13)Ci values. The method has been applied to measure the position-specific variation of the (13)C/(12)C distribution in caffeine. Not only is a clear difference between caffeine isolated from different sources observed, but theobromine from cocoa is found to show a (13)C pattern distinct from that of caffeine. PMID:26067163

  12. 1H and 13C MAS NMR analysis for the role of chemically inequivalent a-N(CH3)4 and b-N(CH3)4 ions in [N(CH3)4]2CuCl4

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2014-01-01

    The spin-lattice relaxation times in the laboratory frame, T1, and in the rotating frame, T1?, for 1H and 13C in [N(CH3)4]2CuCl4 were measured by static NMR and magic angle spinning (MAS) NMR as functions of temperature. The intensities of the 1H and 13C signals changed near phase transition temperatures TC1 and TC3, which indicated that N(CH3)4 plays an important role in these phase transitions. It was thus apparent that the T1 and T1? for 1H are governed by the same molecular motions. Two inequivalent ions, a-N(CH3)4 and b-N(CH3)4, were identified by 13C cross-polarization (CP)/MAS NMR. From these results, the behaviors of these two chemically inequivalent N(CH3)4 groups in the paraelastic and ferroelastic phases are discussed.

  13. GLOBAL ASSIGNMENT AND EXTENSION OF MILLIMETER- AND SUBMILLIMETER-WAVE SPECTRAL DATABASE OF {sup 13}C{sub 1}-METHYL FORMATE (H{sup 13}COOCH{sub 3}) IN THE GROUND AND FIRST EXCITED STATES

    SciTech Connect

    Carvajal, M. [Departamento de Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, 21071 Huelva (Spain); Kleiner, I. [Laboratoire Interuniversitaire des Systemes Atmospheriques, UMR CNRS 7583, CNRS/IPSL, Universite Paris 7 et Universite Paris Est, 61 Av. Charles de Gaulle, F-94010 Creteil Cedex (France); Demaison, J., E-mail: miguel.carvajal@dfa.uhu.e [Laboratoire de Physique des Lasers, Atomes, et Molecules, UMR CNRS 8523, Universite Lille I, F-59655 Villeneuve d'Ascq Cedex (France)

    2010-10-15

    A compilation of the available spectroscopic millimeter- and submillimeter-wave data of the ground and first excited states of {sup 13}C{sub 1}-methyl formate (H{sup 13}COOCH{sub 3}) has been carried out. The exhaustive analysis of the available transition lines of H{sup 13}COOCH{sub 3} has led to the assignment of 7457 spectral lines by means of a global fit of 45 parameters, using the Rho-Axis Method and the BELGI-Cs code, with a resulting unitless standard deviation of 0.57. Over 1600 lines are included for the first time in the fit. In addition, the line strengths of spectral lines are also calculated using the most recent experimental measurement of the electric dipole moment. In conclusion, the present study represents a notable improvement with respect to previous H{sup 13}COOCH{sub 3} spectral analyses. Therefore, the better accuracy of the present analysis may help the future identification of new H{sup 13}COOCH{sub 3} lines in the interstellar and circumstellar media, and may contribute to decrease some of the spectral confusion due to these species in astronomical surveys.

  14. A Study of Spectral Integration and Normalization in NMR-based Metabonomic Analyses

    SciTech Connect

    Webb-Robertson, Bobbie-Jo M.; Lowry, David F.; Jarman, Kristin H.; Harbo, Sam J.; Meng, Quanxin; Fuciarelli, Alfred F.; Pounds, Joel G.; Lee, Monica T.

    2005-09-15

    Metabonomics involves the quantitation of the dynamic multivariate metabolic response of an organism to a pathological event or genetic modification (Nicholson, Lindon and Holmes, 1999). The analysis of these data involves the use of appropriate multivariate statistical methods. Exploratory Data Analysis (EDA) linear projection methods, primarily Principal Component Analysis (PCA), have been documented as a valuable pattern recognition technique for 1H NMR spectral data (Brindle et al., 2002, Potts et al., 2001, Robertson et al., 2000, Robosky et al., 2002). Prior to PCA the raw data is typically processed through four steps; (1) baseline correction, (2) endogenous peak removal, (3) integration over spectral regions to reduce the number of variables, and (4) normalization. The effect of the size of spectral integration regions and normalization has not been well studied. We assess the variability structure and classification accuracy on two distinctly different datasets via PCA and a leave-one-out cross-validation approach under two normalization approaches and an array of spectral integration regions. This study indicates that independent of the normalization method the classification accuracy achieved from metabonomic studies is not highly sensitive to the size of the spectral integration region. Additionally, both datasets scaled to mean zero and unity variance (auto-scaled) has higher variability within classification accuracy over spectral integration window widths than data scaled to the total intensity of the spectrum.

  15. Solid state 13C-NMR, infrared, X-ray powder diffraction and differential thermal studies of the homologous series of some mono-valent metal (Li, Na, K, Ag) n-alkanoates: A comparative study

    NASA Astrophysics Data System (ADS)

    Nelson, Peter N.; Ellis, Henry A.; White, Nicole A. S.

    2015-06-01

    A comparative study of the molecular packing, lattice structures and phase behaviors of the homologous series of some mono-valent metal carboxylates (Li, Na, K and Ag) is carried out via solid state FT-infrared and 13C-NMR spectroscopes, X-rays powder diffraction, density measurements, differential scanning calorimetry, polarizing light microscopy and variable temperature infrared spectroscopy. It is proposed that, for lithium, sodium and potassium carboxylates, metal-carboxyl coordination is via asymmetric chelating bidentate bonding with extensive intermolecular interactions to form tetrahedral metal centers, irrespective of chain length. However, for silver n-alkanoates, carboxyl moieties are bound to silver ions via syn-syn type bridging bidentate coordination to form dimeric units held together by extensive head group inter-molecular interactions. Furthermore, the fully extended hydrocarbon chains which are crystallized in the all-trans conformation are tilted at ca. 30°, 27°, 15° and 31° with respect to a normal to the metal plane, for lithium, sodium, silver and potassium carboxylates, respectively. All compounds are packed as lamellar bilayer structures, however, lithium compounds are crystallized in a triclinic crystal system whilst silver, sodium and potassium n-alkanoates are all monoclinic with possible P1 bravais lattice. Odd-even alternation observed in various physical features is associated with different inter-planar spacing between closely packed layers in the bilayer which are not in the same plane; a phenomenon controlled by lattice packing symmetry requirements. All compounds, except silver carboxylates, show partially reversibly first order pre-melting transitions; the number of which increases with increasing chain length. These transitions are associated, for the most part, with lamellar collapse followed by increased gauche-trans isomerism in the methylene group assembly, irrespective of chain length. It is proposed that the absence of mesomorphic transitions in their phase sequences is due to a lack of sufficient balance between attractive and repulsive electrostatic and van der Waals forces during phase change. The evidence presented in this study shows that phase behaviors of mono-valent metal carboxylates are controlled, mainly, by head group bonding.

  16. In Situ Determination of Tacticity, Deactivation, and Kinetics in [rac-(C2H4(1-Indenyl)2)ZrMe][B(C6F5)4] and [Cp2ZrMe][B(C6F5)4]-Catalyzed Polymerization of 1-Hexene Using (13)C Hyperpolarized NMR.

    PubMed

    Chen, Chia-Hsiu; Shih, Wei-Chun; Hilty, Christian

    2015-06-01

    The stereochemistry, kinetics, and mechanism of olefin polymerization catalyzed by a set of zirconium-based metallocenes was studied by NMR using dissolution dynamic nuclear polarization (DNP). Hyperpolarized 1-hexene was polymerized in situ with a C2 symmetric catalyst, [(EBI)ZrMe][B(C6F5)4] (EBI = rac-(C2H4(1-indenyl)2)), and a C2v symmetric catalyst, [(Cp)2ZrMe][B(C6F5)4] (Cp = cyclopentadienyl). Hyperpolarized (13)C NMR spectra were used to characterize product tacticity following initiation of the reaction. At the same time, a signal gain of 3 orders of magnitude from (13)C hyperpolarization enabled the real time observation of catalyst-polymeryl species and deactivation products, such as vinylidene and a Zr-allyl complex. The compounds appearing in the reaction provide evidence for the existence of ?-hydride elimination and formation of a dormant site via a methane-generating mechanism. The presence of a deactivating mechanism was incorporated in a model used to determine kinetic parameters of the reaction. On this basis, rate constants were measured between 0.8 and 6.7 mol % of catalyst. The concentration dependence of the rate constants obtained indicates a second-order process for polymerization concomitant with a first-order process for deactivation. The simultaneous observation of both processes in the time evolution of (13)C NMR signals over the course of several seconds underlines the utility of hyperpolarized NMR for quantifying early events in polymerization reactions. PMID:25961793

  17. Molecular structure, spectroscopic (FTIR, FT-Raman, 13C and 1H NMR, UV), polarizability and first-order hyperpolarizability, HOMO-LUMO analysis of 2,4-difluoroacetophenone

    NASA Astrophysics Data System (ADS)

    Jeyavijayan, S.

    2015-02-01

    The FTIR and FT-Raman spectra of 2,4-difluoroacetophenone (DFAP) have been recorded in the regions 4000-400 cm-1 and 3500-50 cm-1, respectively. Utilizing the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound were carried out. The optimum molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, were calculated by density functional theory (DFT/B3LYP) method with 6-31+G(d,p) and 6-311++G(d,p) basis sets. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. A detailed interpretation of the infrared and Raman spectra of DFAP is also reported based on total energy distribution (TED). Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The MEP map shows the negative potential sites are on oxygen atom as well as the positive potential sites are around the hydrogen atoms. The UV-Vis spectral analysis of DFAP has also been done which confirms the charge transfer of DFAP. The chemical shifts of H atoms and C atoms were calculated using NMR analysis. Furthermore, the polarizability, the first hyperpolarizability and total dipole moment of the molecule have been calculated.

  18. C NMR Spectra (see p S10)

    E-print Network

    Collum, David B.

    S31 1 H and 13 C NMR Spectra (see p S10) NHBn Me Ph 10 #12;S32 1 H and 13 C NMR Spectra (see p S10) NHBn Me Ph 11 #12;S33 1 H and 13 C NMR Spectra (see p S11) NH-i-Pr n-Bu NH-i-Pr n-Bu 12 Me Me 13 #12;S34 1 H and 13 C NMR Spectra (see p S11)NH-i-Pr Me Ph 14 #12;S35 1 H and 13 C NMR Spectra (see p S11

  19. Proton NMR spectral study of UV treated live Escherichia coli Bacteria

    NASA Astrophysics Data System (ADS)

    Sorokopud, Michael

    The lethal effects of ultraviolet radiation on microorganisms have been known and utilized for many years. In sufficiently high photon fluences, light and in particular, UV light, is an effective and subtle means of killing or at least immobilizing most, if not all cells and micro-organisms. Because of their small size, light can penetrate the enclosing protective walls and enter the inner volumes where it can break organic bonds in components that are vital to cell function. Despite the fact that a very low dose of UV light (1-9 mJ/cm2) has been shown to inactivate many micro-organisms, there remains a dearth of biological information about light induced effects in molecules and their interactions within living microbial systems. The use of 1H NMR as a spectroscopic tool was chosen to undertake an examination of the possible effects resulting from exposing E. coli to lethal fluencies of UV radiation. Once sample preparation, treatment, and NMR mounting methods were optimized, the high sensitivity and high resolution capabilities of the method produced reproducible results for a series of experiments. These results reveal significant changes in the ratio of the 1H NMR spectra of the treated to untreated E.coli samples when the treated sample was exposed to a lethal fluence of 275nm light. Photons at the 275nm wavelength, used in this study, have enough energy to break all of the principle bonds in an organic molecule. The difference spectrum between treated to untreated samples appears to be fitted well using specific component spectra from these groups of compounds. Increases in NMR peak amplitudes are observed and appear to be correlated with the spectral locations of several amino acids, membrane components and several sugars/saccharides. Increases in peak intensities of 4-8% were observed in the 0.8-1.1 ppm chemical shift region, characteristic of lipid and amino acid groups. A 3.5-4% increase was observed in the 2 ppm and 3.4-4 ppm region characteristic of various sugars and possibly amino acid components.

  20. Kinetics of hyperpolarized 13 C1-pyruvate transport

    E-print Network

    Frydman, Lucio

    -regulation of glucose transporters in human malignan- cies, enhancing glucose influx into the proliferating cancer cellsKinetics of hyperpolarized 13 C1-pyruvate transport and metabolism in living human breast cancer in breast cancer. hyperpolarized NMR metabolic fluxes monocarboxylate transporters pyruvate

  1. High-sensitivity visualisation of contaminants in heparin samples by spectral filtering of 1H NMR spectra.

    PubMed

    Rudd, Timothy R; Gaudesi, Davide; Lima, Marcelo A; Skidmore, Mark A; Mulloy, Barbara; Torri, Giangiacomo; Nader, Helena B; Guerrini, Marco; Yates, Edwin A

    2011-04-01

    A novel application of two-dimensional correlation analysis has been employed to filter (1)H NMR heparin spectra distinguishing acceptable natural variation and the presence of foreign species. Analysis of contaminated heparin samples, compared to a dataset of accepted heparin samples using two-dimensional correlation spectroscopic analysis of their 1-dimensional (1)H NMR spectra, allowed the spectral features of contaminants to be recovered with high sensitivity, without having to resort to more complicated NMR experiments. Contaminants, which exhibited features distinct from those of heparin and those with features normally hidden within the spectral mass of heparin could be distinguished readily. A heparin sample which had been pre-mixed with a known contaminant, oversulfated chondroitin sulfate (OSCS), was tested against the heparin reference library. It was possible to recover the (1)H NMR spectrum of the OSCS component through difference 2D-COS power spectrum analysis of as little as 0.25% (w/w) with ease, and of 2% (w/w) for more challenging contaminants, whose NMR signals fell under those of heparin. The approach shows great promise for the quality control of heparin and provides the basis for greatly improved regulatory control for the analysis of heparin, as well as other intrinsically heterogeneous and varied products. PMID:21279244

  2. Neutrino Capture on $^{13}$C

    E-print Network

    T. Suzuki; A. B. Balantekin; T. Kajino

    2012-04-19

    We present neutrino cross sections on $^{13}$C. The charged-current cross sections leading to various states in the daughter $^{13}N$ and the neutral-current cross sections leading to various states in the daughter $^{13}$C are given. We also provide simple polynomial fits to those cross sections for quick estimates of the reaction rates. We briefly discuss possible implications for the current and future scintillator-based experiments.

  3. Identification of heparin samples that contain impurities or contaminants by chemometric pattern recognition analysis of proton NMR spectral data

    Microsoft Academic Search

    Qingda Zang; David A. Keire; Lucinda F. Buhse; Richard D. Wood; Dinesh P. Mital; Syed Haque; Shankar Srinivasan; Christine M. V. Moore; Moheb Nasr; Ali Al-Hakim; Michael L. Trehy; William J. Welsh

    Chemometric analysis of a set of one-dimensional (1D) 1H nuclear magnetic resonance (NMR) spectral data for heparin sodium active pharmaceutical ingredient (API) samples was employed\\u000a to distinguish USP-grade heparin samples from those containing oversulfated chondroitin sulfate (OSCS) contaminant and\\/or\\u000a unacceptable levels of dermatan sulfate (DS) impurity. Three chemometric pattern recognition approaches were implemented:\\u000a classification and regression tree (CART), artificial neural

  4. Quantitative determination of the electronic effects of 3- and 4-pyridazinyl groups from NMR spectral data for isomeric aminophenyl- and phenylpyridazines

    SciTech Connect

    Shkurko, O.P.; Kuznetsov, S.A.; Denisov, A.Yu.; Mamaev, V.P.

    1987-01-01

    The previously unknown aminophenylpyridazines were synthesized. The inductive and resonance constants of 3- and 4-pyridazinyl groups were calculated on the basis of H and TC NMR spectral data for isomeric aminophenyl- and phenylpyridazines in dimethyl sulfoxide (DMSO).

  5. NBO, conformational, NLO, HOMO-LUMO, NMR and electronic spectral study on 1-phenyl-1-propanol by quantum computational methods

    NASA Astrophysics Data System (ADS)

    Xavier, S.; Periandy, S.; Ramalingam, S.

    2015-02-01

    In this study, FT-IR, FT-Raman, NMR and UV spectra of 1-phenyl-1-propanol, an intermediate of anti-depressant drug fluoxetine, has been investigated. The theoretical vibrational frequencies and optimized geometric parameters have been calculated by using HF and density functional theory with the hybrid methods B3LYP, B3PW91 and 6-311+G(d,p)/6-311++G(d,p) basis sets. The theoretical vibrational frequencies have been found in good agreement with the corresponding experimental data. 1H and 13C NMR spectra were recorded and chemical shifts of the molecule were compared to TMS by using the Gauge-Independent Atomic Orbital (GIAO) method. A study on the electronic and optical properties, absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies are performed using HF and DFT methods. The thermodynamic properties (heat capacity, entropy and enthalpy) at different temperatures are also calculated. NBO analysis is carried out to picture the charge transfer between the localized bonds and lone pairs. The local reactivity of the molecule has been studied using the Fukui function. NLO properties related to polarizability and hyperpolarizability are also discussed.

  6. The program XEASY for computer-supported NMR spectral analysis of biological macromolecules

    Microsoft Academic Search

    Christian Bartels; Tai-he Xia; Martin Billeter; Peter Giintert; Kurt Wuthrich

    1995-01-01

    A new program package, XEASY, was written for interactive computer support of the analysis of NMR spectra for three-dimensional structure determination of biological macromolecules. XEASY was developed for work with 2D, 3D and 4D NMR data sets. It includes all the functions performed by the precursor program EASY, which was designed for the analysis of 2D NMR spectra, i.e., peak

  7. Solid-State NMR Study of Paramagnetic Bis(alaninato-?(2)N,O)copper(II) and Bis(1-amino(cyclo)alkane-1-carboxylato-?(2)N,O)copper(II) Complexes: Reflection of Stereoisomerism and Molecular Mobility in (13)C and (2)H Fast Magic Angle Spinning Spectra.

    PubMed

    Szalontai, Gábor; Csonka, Róbert; Speier, Gábor; Kaizer, József; Sabolovi?, Jasmina

    2015-05-18

    Solid-state stereochemistry and mobility of paramagnetic copper(II) complexes formed by aliphatic amino acids (l-alanine, d,l-alanine, 1-amino-2-methyl-alanine) and 1-amino(cyclo)alkane-1-carboxylic acids (alkane = propane, butane, pentane, hexane) as bidentate ligands has been studied by (13)C and (2)H solid-state fast magic angle spinning (MAS) NMR spectroscopy. We examined the prospective method to characterize solid-state paramagnetic compounds in a routine way. Both (13)C and (2)H MAS spectra can distinguish d,l and l,l diastereomers of natural and polydeuterated bis([Dn]alaninato)copper(II) (n = 0, 2, 8) complexes with axial and/or equatorial methyl positions (conformations) primarily due to different Fermi-contact (FC) contributions. The three-bond hyperfine couplings clearly show Karplus-like dependence on the torsional angles which turned out to be a useful assignment aid. Density functional theory calculations of the FC term and crystal structures were also used to aid the final assignments. The correlations obtained for bis(alaninato-?(2)N,O)copper(II) complexes were successfully used to characterize other complexes. The usefulness of the (2)H MAS spectra of the deuterated complexes was underlined. Even the spectra of the easily exchangeable amine protons contained essential stereochemical information. In the case of a dimer structure of bis(1-aminohexane-1-carboxylato-?(2)N,O)copper(II) both the (13)C and (2)H resolutions were good enough to confirm the presence of the cis and trans forms in the asymmetric unit. With regard to the internal solid-state motions in the crystal lattice, the obtained quadrupolar tensor parameters were similar for the d,l- and l,l-alaninato isomers and also for the cis-trans forms suggesting similar crystal packing effects, static amine deuterons involved in hydrogen bonding, and fast rotating methyl groups. PMID:25920900

  8. 13C Metabolic Flux Analysis

    Microsoft Academic Search

    Wolfgang Wiechert

    2001-01-01

    Metabolic flux analysis using 13C-labeled substrates has become an important tool in metabolic engineering. It allows the detailed quantification of all intracellular fluxes in the central metabolism of a microorganism. The method has strongly evolved in recent years by the introduction of new experimental procedures, measurement techniques, and mathematical data evaluation methods. Many of these improvements require advanced skills in

  9. Carbon relaxation in 13C?-H? and 13C?-D? spin pairs as a probe of backbone dynamics in proteins.

    PubMed

    Sun, Hechao; Long, Dong; Brüschweiler, Rafael; Tugarinov, Vitali

    2013-02-01

    NMR methodology for the measurements of ?-carbon R(1) and R(1?) spin relaxation rates in (13)C(?)-H(?) and (13)C(?)-D(?) spin pairs of U-[(13)C; (15)N] partially deuterated proteins is developed. The intra-HN[CA] NMR experiment isolates carbon nuclei belonging to either (13)C(?)-H(?) or (13)C(?)-D(?) spin systems in the same protein sample prior to the measurement of (13)C(?) relaxation rates. The differences between R(1) and R(2) rates in the two spin pairs (?R(1), ?R(2)) eliminate all contributions to (13)C(?) decay rates not associated with direct (13)C(?)-(1)H(?)(D(?)) dipolar interactions including chemical exchange and serve as robust measures of C(?)-H(?)(D(?)) bond vector motions in proteins. The methodology is applied to the relaxation study of ?-carbon sites in the protein ubiquitin at two temperatures. The measures of order of individual C(?)-H(?)(D(?)) bond vectors (S(2)) in ubiquitin derived from the fitting of differential rates (?R(1), ?R(2)) unambiguously report on protein dynamics, thereby eliminating potential contributions from modulations of C(?)-H(?)(D(?)) bond lengths by their environment. They are comparable to the ones obtained from a molecular dynamics simulation at 27 °C. PMID:23311577

  10. Experimental and quantum-chemical studies of 1H, 13C and 15N NMR coordination shifts in Pd(II) and Pt(II) chloride complexes with methyl and phenyl derivatives of 2,2'-bipyridine and 1,10-phenanthroline.

    PubMed

    Pazderski, Leszek; Tousek, Jaromír; Sitkowski, Jerzy; Kozerski, Lech; Sz?yk, Edward

    2007-12-01

    1H, 13C and 15N NMR studies of platinide(II) (M=Pd, Pt) chloride complexes with methyl and phenyl derivatives of 2,2'-bipyridine and 1,10-phenanthroline [LL=4,4'-dimethyl-2,2'-bipyridine (dmbpy); 4,4'-diphenyl-2,2'-bipyridine (dpbpy); 4,7-dimethyl-1,10-phenanthroline (dmphen); 4,7-diphenyl-1,10-phenanthroline (dpphen)] having a general [M(LL)Cl2] formula were performed and the respective chemical shifts (delta1H, delta13C, delta15N) reported. 1H high-frequency coordination shifts (Delta1Hcoord=delta1Hcomplex-delta1Hligand) were discussed in relation to the changes of diamagnetic contribution in the relevant 1H shielding constants. The comparison to literature data for similar [M(LL)(XX)], [M(LL)X2] and [M(LL)XY] coordination or organometallic compounds containing various auxiliary ligands revealed a large dependence of delta1H parameters on inductive and anisotropic effects. 15N low-frequency coordination shifts (Delta15Ncoord=delta 15Ncomplex-delta15Nligand) of ca 88-96 ppm for M=Pd and ca 103-111 ppm for M=Pt were attributed to both the decrease of the absolute value of paramagnetic contribution and the increase of the diamagnetic term in the expression for 15N shielding constants. The absolute magnitude of Delta15Ncoord parameter increased by ca 15 ppm upon Pd(II)-->Pt(II) transition and by ca 6-7 ppm following dmbpy-->dmphen or dpbpy-->dpphen ligand replacement; variations between analogous complexes containing methyl and phenyl ligands (dmbpy vs dpbpy; dmphen vs dpphen) did not exceed+/-1.5 ppm. Experimental 1H, 13C, 15N NMR chemical shifts were compared to those quantum-chemically calculated by B3LYP/LanL2DZ+6-31G**//B3LYP/LanL2DZ+6-31G*, both in vacuo and in DMSO or DMF solution. PMID:18044804

  11. Synthesis and applications of {sup 13}C glycerol

    SciTech Connect

    Stocking, E.; Khalsa, O.; Martinez, R.A.; Silks, L.A. III [Los Alamos National Laboratory, NM (United States)

    1994-12-01

    Due in part to the use of labeled glycerol for the {sup 13}C enrichment of biomolecules, we are currently developing new synthetic routes to various isotopomers of glycerol. Judging from our experience, traditional methods of glycerol synthesis are not easily adapted for isotopic enrichment and/or have poor overall yields (12 to 15%). Furthermore, the use of glycerol for enrichment can be prohibitively expensive and its availability is limited by the level of demand. We are presently developing a short de novo synthesis of glycerol from carbon dioxide ({approximately}53% overall yield for four steps) and are examining the feasibility of synthesizing site-specific {sup 13}C-labeled glycerol and dihydroxyacetone (DHA) from labeled methanol and carbon dioxide. One application of {sup 13}C glycerol we have examined is enzymatic conversion of glycerol to glyceraldehyde-3-monophosphate or dihydroxyacetone monophosphate (DHAP) with yields ranging from 25 to 50% (as determined by NMR spectroscopy). We are also pursuing the chemical conversion of {sup 13}C-labeled DHA to DHAP. We are especially interested in {sup 13}C-labeled DHAP because we are investigating its use as a chemo-enzymatic precursor for both labeled 2-deoxyribose and 2-deoxyribonucleic acids.

  12. GIAO DFT 13C/15N chemical shifts in regioisomeric structure determination of fused pyrazoles.

    PubMed

    Chimichi, Stefano; Boccalini, Marco; Matteucci, Alessandra; Kharlamov, Sergey V; Latypov, Shamil K; Sinyashin, Oleg G

    2010-08-01

    The combined use of two-dimensional NMR correlation experiments and gauge including atomic orbital density functional theory in (13)C NMR chemical shift (CS) calculations allowed reliable and simple structural determination of regioisomeric heterocyclic systems that originate from the reactions of acylquinolinones with substituted hydrazines. Moreover, the results of differential analysis between the calculated (15)N NMR CSs for hypothetical structures and the experimental data of the title azaheterocyclic systems were even more advantageous with respect to (13)C because there was no need for correlational analysis: structures of the regioisomeric compounds could be determined just by direct comparison. PMID:20589725

  13. IR and NMR spectral studies of 4-bromo-1-naphthyl chalcones-assessment of substituent effects

    Microsoft Academic Search

    G. Thirunarayanan; M. Gopalakrishnan; G. Vanangamudi

    2007-01-01

    Infrared ?CO (cm?1) of s-cis and s-trans frequencies and nuclear magnetic resonance chemical shifts ?1H (ppm) of H-? and H-?, ?13C (ppm) of C-? and C-? data were assigned from their respective spectra of a series of various substituted styryl 4-bromo-1-naphthyl chalcones. These values are correlated with various Hammett substituent constants. From the results of statistical analysis, the effect of

  14. Determination of isoprenyl and lavandulyl positions of flavonoids from Sophora flavescens by NMR experiment

    Microsoft Academic Search

    Shi Yong Ryu; Hyun Sun Lee; Young Kyoon Kim; Sung Hoon Kim

    1997-01-01

    All fifteen flavonoids (1?15) have been isolated from the roots ofSophora flavescens (Leguminosae) as active principles of the cytotoxic property toward human tumor cell lines such as A549, SK-OV-3, SK-Mel-2,\\u000a XF498 and HCT15,in vitro. By means of spectral analyses, particularly by the aid of various two dimensional NMR experiments, all1H-NMR and13C-NMR signals of1?15 were completely assigned, and thus the structures

  15. Influence of 13C isotopic labeling location of 13C DNP of acetate using TEMPO free radical

    NASA Astrophysics Data System (ADS)

    Parish, Christopher; Niedbalski, Peter; Lumata, Lloyd

    2015-03-01

    Dynamic nuclear polarization (DNP) via the dissolution method enhances the liquid-state magnetic resonance (NMR or MRI) signals of insensitive nuclear spins by at least 10,000-fold. The basis for all these signal enhancements at room temperature is the polarization transfer from the electrons to nuclear spins at cryogenic temperature and high magnetic field. In this work, we have studied the influence of the location of 13C isotopic labeling on the DNP of sodium acetate at 3.35 T and 1.4 K using a wide ESR linewidth free radical 4-oxo-TEMPO. The carbonyl [1-13C]acetate spins produced a polarization level that is almost twice that of the methyl [2-13C]acetate spins. On the other hand, the polarization of the methyl 13C spins doubled to reach the level of [1-13C]acetate when the methyl group was deuterated. Meanwhile, the solid-state nuclear relaxation of these samples are the same and do not correlate with the polarization levels. These behavior implies that the nuclear relaxation for these samples is dominated by the contribution from the free radicals and the polarization levels can be explained by a thermodynamic picture of DNP.

  16. Merremoside D: De novo synthesis of the purported structure, NMR analysis, comparison of spectral data

    PubMed Central

    Sharif, Ehesan U.; Wang, Hua-Yu Leo

    2014-01-01

    The first synthesis of the purported structure of Merremoside D has been achieved in 22 longest linear steps. The de novo asymmetric synthesis relied on the use of asymmetric catalysis to selectively install all 21 stereocenters in the final compounds from commercially available achiral starting materials. Adiabatic gradient 2D NMR techniques (gHSQCAD, gHMBCAD, gH2BCAD, gHSQCTOXYAD, ROESYAD) were used to completely assign the structure of synthetic Merremoside D. Comparison of our assignments with the limited NMR data reported for natural Merremoside D allows for the tentative confirmation of its structure. PMID:24354696

  17. Deuterium isotope shifts for backbone 1H, 15N and 13C nuclei in intrinsically disordered protein -synuclein

    PubMed Central

    Maltsev, Alexander S.; Ying, Jinfa; Bax, Ad

    2012-01-01

    Intrinsically disordered proteins (IDPs) are abundant in nature and characterization of their potential structural propensities remains a widely pursued but challenging task. Analysis of NMR secondary chemical shifts plays an important role in such studies, but the output of such analyses depends on the accuracy of reference random coil chemical shifts. Although uniform perdeuteration of IDPs can dramatically increase spectral resolution, a feature particularly important for the poorly dispersed IDP spectra, the impact of deuterium isotope shifts on random coil values has not yet been fully characterized. Very precise 2H isotope shift measurements for 13C?, 13C?, 13C’, 15N, and 1HN have been obtained by using a mixed sample of protonated and uniformly perdeuterated -synuclein, a protein with chemical shifts exceptionally close to random coil values. Decomposition of these isotope shifts into one-bond, two-bond and three-bond effects as well as intra- and sequential residue contributions shows that such an analysis, which ignores conformational dependence, is meaningful but does not fully describe the total isotope shift to within the precision of the measurements. Random coil 2H isotope shifts provide an important starting point for analysis of such shifts in structural terms in folded proteins, where they are known to depend strongly on local geometry. PMID:22960996

  18. Ediacaran ? 13C chemostratigraphy of South China

    Microsoft Academic Search

    Chuanming Zhou; Shuhai Xiao

    2007-01-01

    We report new ?13C chemostratigraphic data of the Ediacaran System in South China. Using litho- and biostratigraphic markers as independent calibrators, we combine new and previously published ?13C data to construct a composite ?13C profile for the Ediacaran System in South China. The composite curve shows, in chronostratigraphic order, 1) a negative ?13C excursion (EN1) in the Doushantuo cap carbonate

  19. Solid State FT-IR and (31)P NMR Spectral Features of Phosphate Compounds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Solid-state spectroscopic techniques, including Fourier transform infrared (FT-IR) and solid-state 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopies, are powerful tools for evaluating metal speciation and transformation mechanisms of P compounds in the environment. Studie...

  20. Etude spectroscopique RMN 1H et 13C de derives du benzofuro(3,2-b)benzofuranne et du benzofuro(2,3-b)benzofuranne

    NASA Astrophysics Data System (ADS)

    Ramah, Mohamed; Vebrel, Joël; Laude, Bernard

    The NMR spectroscopic properties ( 1H and 13C) of derivatives of benzofuro(3,2-b)benzofuran and benzofuro(2,3-b)benzofuran have been studied. Data allow us to determine structures of isomers and NMR 13C exhibits stereoelectronic effects of substituents.

  1. Coherence selection in double CP MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, Jen-Hsien; Chou, Fang-Chieh; Tzou, Der-Lii M.

    2008-11-01

    Applications of double cross-polarization (CP) magic-angle spinning (MAS) NMR spectroscopy, via 1H/ 15N and then 15N/ 13C coherence transfers, for 13C coherence selection are demonstrated on a 15N/ 13C-labeled N-acetyl-glucosamine (GlcNAc) compound. The 15N/ 13C coherence transfer is very sensitive to the settings of the experimental parameters. To resolve explicitly these parameter dependences, we have systematically monitored the 13C{ 15N/ 1H} signal as a function of the rf field strength and the MAS frequency. The data reveal that the zero-quantum coherence transfer, with which the 13C effective rf field is larger than that of the 15N by the spinning frequency, would give better signal sensitivity. We demonstrate in one- and two-dimensional double CP experiments that spectral editing can be achieved by tailoring the experimental parameters, such as the rf field strengths and/or the MAS frequency.

  2. Single-crystal and powder X-ray diffraction, 13C CP/MAS NMR, and DFT-GIAO calculations of methyl 3,4,6-tri-O-acetyl-2-O-(2,3,4,6-tetra-O-acetyl-?-D-galactopyranosyl)-?-D-glucopyranoside and methyl 2,4,6-tri-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-?-D-galactopyranosyl)-?-D-glucopyranoside

    NASA Astrophysics Data System (ADS)

    Gubica, Tomasz; St?pie?, Dorota K.; Pisklak, Dariusz M.; Ostrowski, Andrzej; Cyra?ski, Micha? K.

    2013-03-01

    Single-crystal and powder X-ray diffraction, 13C CP/MAS NMR, and DFT-GIAO calculations of shielding constants were performed for methyl 3,4,6-tri-O-acetyl-2-O-(2,3,4,6-tetra-O-acetyl-?-D-galactopyranosyl)-?-D-glucopyranoside (1) and methyl 2,4,6-tri-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-?-D-galactopyranosyl)-?-D-glucopyranoside (2). 1 crystallizes with three molecules whereas 2 with two molecules in an independent part of the unit cell. The macroscopic sample of 1 consists of one polymorph, while for 2 two or three polymorphs were detected. The existence of different numbers of the molecules in the asymmetric units as well as different numbers of polymorphs of 1 and 2 was verified by solid-state NMR spectroscopy.

  3. Valence XPS, IR, and C13 NMR spectral analysis of 6 polymers by quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Endo, Kazunaka; Ida, Tomonori; Shimada, Shingo; Ortiz, Joseph Vincent; Deguchi, Kenzo; Shimizu, Tadashi; Yamada, Kazuhiko

    2012-11-01

    Valence XPS (VXPS), IR, and C13 NMR spectra of 6 polymers (PE, PS, PMMA, PET, Nylon6, PVC) have been analyzed using the model oligomers from B3LYP/6-31+G(d,p) basis calculations in GAUSSIAN 09. We simulated VXPS of the polymers by the negative of the orbital energies of the ground electronic state at the geometry-optimization of the model oligomers. The simulated VXPS spectra by B3LYP/6-31+G(d,p) basis level were compared with simulated spectra by calculations of SAOP method of ADF program. Simulated IR, and C13 NMR spectra of polymers were obtained from the other SCF calculations of B3LYP/6-31+G(d,p) basis using atomic coordinates of the model molecules at the geometry optimization, in order to gain the vibrational frequencies and nuclear magnetic shielding tensors, respectively. We have clarified the electronic states of the polymers from the good accordance of simulated VXPS, IR, and C13 NMR spectra of polymer models molecules with the experimental ones of the polymers.

  4. N NMR study of (pyrrolidine-2,2-diyl)bisphosphonic acid, tetraalkyl(pyrrolidine-2,2-diyl)bisphosphonates and acyclic tetraethyl

    E-print Network

    Boyer, Edmond

    A 1 H, 13 C, 31 P and 15 N NMR study of (pyrrolidine-2,2-diyl)bisphosphonic acid, tetraalkyl-381" #12;ABSTRACT: A multinuclear NMR study (1 H, 13 C, 31 P, 15 N) was performed on a series of new cyclic shifts and coupling constants of the various nuclei. KEYWORDS: NMR; 1 H NMR; 13 C NMR; 31 P NMR; 15 N NMR

  5. Unambiguous assignment of short- and long-range structural restraints by solid-state NMR spectroscopy with segmental isotope labeling.

    PubMed

    Schubeis, Tobias; Lührs, Thorsten; Ritter, Christiane

    2015-01-01

    We present an efficient method for the reduction of spectral complexity in the solid-state NMR spectra of insoluble protein assemblies, without loss of signal intensity. The approach is based on segmental isotope labeling by using the split intein DnaE from Nostoc punctiforme. We show that the segmentally (13)C, (15)N-labeled prion domain of HET-s exhibits significantly reduced spectral overlap while retaining the wild-type structure and spectral quality. A large number of unambiguous distance restraints were thus collected from a single two-dimensional (13)C, (13)C cross-correlation spectrum. The observed resonances could be unambiguously identified as intramolecular without the need for preparing a dilute, less sensitive sample. PMID:25394265

  6. NMR and Raman spectral studies of ammonium hydrogen selenites single crystals

    Microsoft Academic Search

    O. I. Nasluzova; I. S. Vinogradova; A. G. Lundin; L. L. Zhidkov

    2004-01-01

    The chemical composition and peculiarities of the structure of a salt that precipitates from aqueous solution of NH4HSeO3 at the 25?°C was studied by NMR and Raman spectroscopy methods using the single crystal samples with different heavy water contents. It was proved that this salt is actually monohydrate of hydrogen selenite, NH4HSeO3?H2O but not trihydrate of pyroselenite, (NH4)2Se2O5?3H2O as was

  7. Oil stability prediction by high-resolution (13)C nuclear magnetic resonance spectroscopy.

    PubMed

    Hidalgo, Francisco J; Gómez, Gemma; Navarro, José L; Zamora, Rosario

    2002-10-01

    (13)C NMR spectra of oil fractions obtained chromatographically from 66 vegetable oils were obtained and analyzed to evaluate the potential use of those fractions in predicting oil stabilities and to compare those results with oil stability prediction by using chemical determinations. The oils included the following: virgin olive oils from different cultivars and regions of Europe and north Africa; "lampante" olive, refined olive, refined olive pomace, low-erucic rapeseed, high-oleic sunflower, corn, grapeseed, soybean, and sunflower oils. Oils were analyzed for fatty acid and triacylglycerol composition, as well as for phenol and tocopherol contents. By using stepwise linear regression analysis (SLRA), the chemical determinations and the (13)C NMR data that better explained the oil stability determined by the Rancimat were selected. These selected variables were related to both the susceptibility of the oil to be oxidized and the content of minor components that most contributed to oil stability. Because (13)C NMR considered many more variables than those determined by chemical analysis, the predicted stabilities calculated by using NMR data were always better than those obtained by using chemical determinations. All these results suggest that (13)C NMR may be a powerful tool to predict oil stabilities when applied to chromatographically enriched oil fractions. PMID:12358445

  8. NMR of a Phospholipid: Modules for Advanced Laboratory Courses

    NASA Astrophysics Data System (ADS)

    Gaede, Holly C.; Stark, Ruth E.

    2001-09-01

    A laboratory project is described that builds upon the NMR experience undergraduates receive in organic chemistry with a battery of NMR experiments that investigate egg phosphatidylcholine (egg PC). This material, often labeled in health food stores as lecithin, is a major constituent of mammalian cell membranes. The NMR experiments may be used to make resonance assignments, to study molecular organization in model membranes, to test the effects of instrumental parameters, and to investigate the physics of nuclear spin systems. A suite of modular NMR exercises is described, so that the instructor may tailor the laboratory sessions to biochemistry, instrumental analysis, or physical chemistry. The experiments include solution-state one-dimensional (1D) 1H, 13C, and 31P experiments; two-dimensional (2D) TOtal Correlated SpectroscopY (TOCSY); and the spectral editing technique of Distortionless Enhancement by Polarization Transfer (DEPT). To demonstrate the differences between solution and solid-state NMR spectroscopy and instrumentation, a second set of experiments generates 1H, 13C, and 31P spectra of egg PC dispersed in aqueous solution, under both static and magic-angle spinning conditions.

  9. sup 13 C NMR investigation of crosslinking in organic aerogels

    SciTech Connect

    Ward, R. L.; Pekala, R. W.

    1989-09-15

    Organic aerogels are a special type of low density foam produced from the supercritical drying of resorcinol-formaldehyde (RF) gels. These aerogels have continuous porosity, ultrafine cell/pore sizes (<1000 {angstrom}), and a microstructure composed of interconnected colloidal-like particles with diameters ranging from 30-175 {angstrom}. The particle size, surface area, density, and mechanical properties of the aerogels are largely determined by the catalysts concentration used in the sol-gel polymerization. In order to gain some insight into the crosslinks between RF particles, aerogels were labeled with C-13 formaldehyde at various times in the polymerization. CPMAS and IRCP techniques were used to correlate the relaxation behavior of the C-13 enriched aerogels with their different microstructures. 9 refs., 1 fig., 2 tabs.

  10. Toward 13C hyperpolarized biomarkers produced by thermal mixing with hyperpolarized 129Xe

    PubMed Central

    Lisitza, Natalia; Muradian, Iga; Frederick, Eric; Patz, Samuel; Hatabu, Hiroto; Chekmenev, Eduard Y.

    2009-01-01

    The 13C NMR signal of acetic acid 1-13C-AcH is enhanced by polarization transfer from hyperpolarized 129Xe using a thermal mixing procedure. 1-13C-AcH acid and hyperpolarized 129Xe are mixed as gases to disperse 129Xe in the acetic acid. The mixture is frozen with liquid N2 at 0.5 T. The magnetic field is then momentarily dropped to allow for exchange of spin polarization between 13C and 129Xe. After polarization exchange the magnetic field is raised to its original value and the mixture is thawed, resulting in a solution of polarization enhanced 1-13C-AcH. A 13C nuclear spin polarization enhancement of 10 is observed compared to its thermal polarization at 4.7 T. This polarization enhancement is approximately three orders of magnitude lower than that predicted by theory. The discrepancy is attributed to the formation of either an inhomogeneous solid matrix and?or spin dynamics during polarization transfer. Despite the low polarization enhancement, this is the first report of polarization transfer from 129Xe to 13C nuclear spins achieved by thermal mixing for a proton-containing molecule of biomedical importance. If future work can increase the enhancement, this method will be useful in hyperpolarizing a wide range of 13C enriched compounds important in biomedical and biophysical research. PMID:19655895

  11. DFT-GIAO(1)H NMR chemical shifts prediction for the spectral assignment and conformational analysis of the anticholinergic drugs (-)-scopolamine and (-)-hyoscyamine.

    PubMed

    Muñoz, Marcelo A; Joseph-Nathan, Pedro

    2010-06-01

    The relatively large chemical shift differences observed in the (1)H NMR spectra of the anticholinergic drugs (-)-scopolamine 1 and (-)-hyoscyamine 2 measured in CDCl(3) are explained using a combination of systematic/molecular mechanics force field (MMFF) conformational searches and gas-phase density functional theory (DFT) single point calculations, geometry optimizations and chemical shift calculations within the gauge including/invariant atomic orbital (GIAO) approximation. These calculations show that both molecules prefer a compact conformation in which the phenyl ring of the tropic ester is positioned under the tropane bicycle, clearly suggesting that the chemical shift differences are produced by the anisotropic effect of the aromatic ring. As the calculations fairly well predict these experimental differences, diastereotopic NMR signal assignments for the two studied molecules are proposed. In addition, a cursory inspection of the published (1)H and (13)C NMR spectra of different forms of 1 and 2 in solution reveals that most of them show these diastereotopic chemical shift differences, strongly suggesting a preference for the compact conformation quite independent of the organic or aqueous nature of the solvent. PMID:20474024

  12. The Indian Ocean 13C Suess effect

    NASA Astrophysics Data System (ADS)

    Sonnerup, Rolf E.; Quay, Paul D.; McNichol, Ann P.

    2000-09-01

    The ?13C of dissolved inorganic carbon (DIC) decrease (the 13C Suess effect) in the Indian Ocean was calculated using a multiparameter linear regression comparison of the 1978 Geochemical Ocean Sections Study and 1995 World Ocean Circulation Experiment ?13C of DIC, hydrographic, and nutrient data. The surface ocean ?13C decrease rate along 80° and 115°E ranged from approximately -0.1‰ decade-1 at 55°S to a maximum of approximately -0.18‰ decade-1 at ˜ 35°S and decreased northward to around -0.13‰ decade-1 at the equator. Using a global extrapolation based on ocean model results [Bacastow et al., 1996] and previous ?13C changes calculated from 1970 to 1993 station reoccupations in the Pacific Ocean and based on preformed ?13C versus chlorofluorocarbon age trends in the Indian, Pacific, and Atlantic Oceans [Sonnerup et al., 1999], an ocean-wide average surface ocean ?13C rate of change of -0.15 to -0.17‰ decade-1 was estimated. The average depth-integrated ?13C change rate between 1978 and 1995 along 80° and 115°E was -6.9 ± 0.5‰ m yr-1 from 58°S to 5°N.

  13. New guidelines for delta13C measurements.

    PubMed

    Coplen, Tyler B; Brand, Willi A; Gehre, Matthias; Gröning, Manfred; Meijer, Harro A J; Toman, Blaza; Verkouteren, R Michael

    2006-04-01

    Consistency of delta13C measurements can be improved 39-47% by anchoring the delta13C scale with two isotopic reference materials differing substantially in 13C/12C. It is recommended that delta13C values of both organic and inorganic materials be measured and expressed relative to VPDB (Vienna Peedee belemnite) on a scale normalized by assigning consensus values of -46.6 per thousand to L-SVEC lithium carbonate and +1.95 per thousand to NBS 19 calcium carbonate. Uncertainties of other reference material values on this scale are improved by factors up to two or more, and the values of some have been notably shifted: the delta13C of NBS 22 oil is -30.03 per thousand. PMID:16579631

  14. Identification of heparin samples that contain impurities or contaminants by chemometric pattern recognition analysis of proton NMR spectral data.

    PubMed

    Zang, Qingda; Keire, David A; Buhse, Lucinda F; Wood, Richard D; Mital, Dinesh P; Haque, Syed; Srinivasan, Shankar; Moore, Christine M V; Nasr, Moheb; Al-Hakim, Ali; Trehy, Michael L; Welsh, William J

    2011-08-01

    Chemometric analysis of a set of one-dimensional (1D) (1)H nuclear magnetic resonance (NMR) spectral data for heparin sodium active pharmaceutical ingredient (API) samples was employed to distinguish USP-grade heparin samples from those containing oversulfated chondroitin sulfate (OSCS) contaminant and/or unacceptable levels of dermatan sulfate (DS) impurity. Three chemometric pattern recognition approaches were implemented: classification and regression tree (CART), artificial neural network (ANN), and support vector machine (SVM). Heparin sodium samples from various manufacturers were analyzed in 2008 and 2009 by 1D (1)H NMR, strong anion-exchange high-performance liquid chromatography, and percent galactosamine in total hexosamine tests. Based on these data, the samples were divided into three groups: Heparin, DS ? 1.0% and OSCS = 0%; DS, DS > 1.0% and OSCS = 0%; and OSCS, OSCS > 0% with any content of DS. Three data sets corresponding to different chemical shift regions (1.95-2.20, 3.10-5.70, and 1.95-5.70 ppm) were evaluated. While all three chemometric approaches were able to effectively model the data in the 1.95-2.20 ppm region, SVM was found to substantially outperform CART and ANN for data in the 3.10-5.70 ppm region in terms of classification success rate. A 100% prediction rate was frequently achieved for discrimination between heparin and OSCS samples. The majority of classification errors between heparin and DS involved cases where the DS content was close to the 1.0% DS borderline between the two classes. When these borderline samples were removed, nearly perfect classification results were attained. Satisfactory results were achieved when the resulting models were challenged by test samples containing blends of heparin APIs spiked with non-, partially, or fully oversulfated chondroitin sulfate A, heparan sulfate, or DS at the 1.0%, 5.0%, and 10.0% (w/w) levels. This study demonstrated that the combination of 1D (1)H NMR spectroscopy with multivariate chemometric methods is a nonsubjective, statistics-based approach for heparin quality control and purity assessment that, once standardized, minimizes the need for expert analysts. PMID:21678118

  15. New guidelines for ?13C measurements

    USGS Publications Warehouse

    Coplen, Tyler B.; Brand, Willi A.; Gehre, Matthias; Groning, Manfred; Meijer, Harro A. J.; Toman, Blaza; Verkouteren, R. Michael

    2006-01-01

    Consistency of ?13C measurements can be improved 39?47% by anchoring the ?13C scale with two isotopic reference materials differing substantially in 13C/12C. It is recommended that?13C values of both organic and inorganic materials be measured and expressed relative to VPDB (Vienna Peedee belemnite) on a scale normalized by assigning consensus values of ?46.6‰ to L-SVEC lithium carbonate and +1.95‰ to NBS 19 calcium carbonate. Uncertainties of other reference material values on this scale are improved by factors up to two or more, and the values of some have been notably shifted:? the ?13C of NBS 22 oil is ?30.03%.

  16. Structure of thin diamond films: A 1H and 13C nuclear-magnetic-resonance study

    NASA Astrophysics Data System (ADS)

    Pruski, M.; Lang, D. P.; Hwang, Son-Jong; Jia, H.; Shinar, J.

    1994-04-01

    The 1H and 13C nuclear magnetic resonance (NMR) of thin diamond films deposited from naturally abundant (1.1 at. %) as well as 50% and 100% 13enriched CH4 heavily diluted in H2 is described and discussed. Less than 0.6 at. % of hydrogen is found in the films which contain crystallites up to ~15 ?m across. The 1H NMR consists of a broad 50-65-kHz-wide Gaussian line attributed to H atoms bonded to carbon and covering the crystallite surfaces. A narrow Lorentzian line was only occasionally observed and is found not to be intrinsic to the diamond structure. The 13C NMR demonstrates that >99.5% of the C atoms reside in a quaternary diamondlike configuration. 1-13C cross-polarization measurement indicates that, at the very least, the majority of 13C nuclei cross polarized by 1H, i.e., within three bond distances from a 1H at a crystallite surface, reside in sp3 diamondlike coordinated sites. The 13C relaxation rates of the films are four orders of magnitude faster than that of natural diamond and believed to be due to 13C spin diffusion to paramagnetic centers, presumably carbon dangling bonds. Analysis of the measured relaxation rates indicates that within the 13C spin-diffusion length of ?DTc1 ~0.05 ?m, these centers are uniformly distributed in the diamond crystallites. The possibility that the dangling bonds are located at internal nanovoid surfaces is discussed.

  17. Biotransformation of [(12)C]- and [(13)C]-tert-amyl methyl ether and tert-amyl alcohol.

    PubMed

    Amberg, A; Bernauer, U; Scheutzow, D; Dekant, W

    1999-10-01

    tert-Amyl methyl ether (TAME) is intended for use as a gasoline additive to increase oxygen content. Increased oxygen content in gasoline reduces tailpipe emissions of hydrocarbons and carbon monoxide from cars. Due to possible widespread use of TAME, the toxicity of TAME is under investigation. We studied the biotransformation of TAME in rats and one human volunteer after inhalation of (12)C- or (13)C-labeled TAME. In addition, the biotransformation of [(13)C]-tert-amyl alcohol was studied in rats after gavage. Urinary metabolites were identified by GC/MS and (13)C NMR. Rats (two males and two females) were individually exposed to 2000 ppm [(12)C]- or [(13)C]TAME for 6 h, and urine was collected for 48 h. Free and glucuronidated 2-methyl-2,3-butanediol and a glucuronide of tert-amyl alcohol were identified by (13)C NMR, GC/MS, and LC/MS/MS as major urinary metabolites on the basis of the relative intensities of the (13)C NMR signals. The presence of several minor metabolites was also indicated by (13)C NMR; they were identified as tert-amyl alcohol, 2-hydroxy-2-methylbutyric acid, and 3-hydroxy-3-methylbutyric acid. One human volunteer was exposed to an initial concentration of 27 000 ppm [(13)C]TAME by inhalation for 4 min from a 2 L gas sampling bag, and metabolites of TAME excreted in urine were analyzed by (13)C NMR. All TAME metabolites identified in rats were also present in the human urine samples. To study tert-amyl alcohol biotransformation, male rats (n = 3) were treated with 250 mg/kg [(13)C]-tert-amyl alcohol dissolved in corn oil by gavage, and urine was collected for 48 h. (13)C NMR of the urine samples showed the presence of metabolites identical to those in the urine of [(13)C]TAME-treated rats. Our results suggest that TAME is extensively metabolized by rats and humans to tert-amyl alcohol which may be further oxidized to diols and carboxylic acids. These reactions are likely mediated by cytochrome P450-dependent oxidations. PMID:10525272

  18. Modeling 13C discrimination in Tree Rings

    NASA Astrophysics Data System (ADS)

    Berninger, Frank; Sonninen, Eloni; Aalto, Tuula; Lloyd, Jon

    2000-03-01

    Annual variations from 1877 to 1995 in tree-ring ?-cellulose 13C/12C isotopic ratios for four subarctic Pinus sylvestris trees were determined, and, in conjunction with a recent record of atmospheric 13CO2/12CO2 ratios, the historical pattern of photosynthetic isotope discrimination, ?13C, was evaluated. Year-to-year variability in ?13C has been as much as 1.5‰ with the period 1900-1920 showing an extended period of unusually high photosynthetic discriminations. The summers during these years were, on average, unusually cold. Since 1920 a long term trend of increasing ?13C of ˜0.016‰yr-1 is inferred. We compared measured ?13C with those predicted on the basis of the theoretical relationship between ?13C and the ratio of substomatal to ambient CO2 concentration, Ci/Ca using mechanistic equations for chloroplast biochemistry coupled with a stomatal conductance model. Two variations of a nonlinear optimal-regulation stomatal conductance model were compared. Although both models were based on the assumption that stomata serve to minimize the average transpiration rate for a given average rate of CO2 assimilation, one version of the model incorporated reductions in stomatal conductance in response to recent increases in atmospheric CO2 concentrations and the other did not. The CO2 sensitive stomatal model failed to describe the long-term increase in 13C discrimination, especially after 1950. The insensitive model gave good agreement, suggesting that an observed increase in subarctic Pinus sylvestris ?13C since 1920 is attributable to recent increases in atmospheric CO2 concentrations with subsequent increases in the ratio of substomatal to ambient CO2 concentrations. The model was also capable of accounting for high frequency (year-to-year) variations in ?13C, these differences being attributable to year-to-year fluctuations in the average leaf-to-air vapor pressure difference affecting stomatal conductance and hence Ci/Ca.

  19. Stereochemistry of 16a-hydroxyfriedelin and 3-Oxo-16-methylfriedel-16-ene established by 2D NMR spectroscopy.

    PubMed

    Duarte, Lucienir Pains; Silva de Miranda, Roqueline Rodrigues; Rodrigues, Salomão Bento Vasconcelos; de Fátima Silva, Grácia Divina; Vieira Filho, Sidney Augusto; Knupp, Vagner Fernandes

    2009-01-01

    Friedelin (1), 3beta-friedelinol (2), 28-hydroxyfriedelin (3), 16alpha-hydroxyfriedelin (4), 30-hydroxyfriedelin (5) and 16alpha,28-dihydroxyfriedelin (6) were isolated through fractionation of the hexane extract obtained from branches of Salacia elliptica. After a week in CDCl(3) solution, 16alpha-hydroxyfriedelin (4) reacted turning into 3-oxo-16-methylfriedel-16-ene (7). This is the first report of a dehydration followed by a Nametkin rearrangement of a pentacyclic triterpene in CDCl(3) solution occurring in the NMR tube. These seven pentacyclic triterpenes was identified through NMR spectroscopy and the stereochemistry of compound 4 and 7 was established by 2D NMR (NOESY) spectroscopy and mass spectrometry (GC-MS). It is also the first time that all the (13)C-NMR and 2D NMR spectral data are reported for compounds 4 and 7. PMID:19214150

  20. Evidence for Transaldolase Activity in the Isolated Heart Supplied with [U-13C3]Glycerol*

    PubMed Central

    Jin, Eunsook S.; Sherry, A. Dean; Malloy, Craig R.

    2013-01-01

    Studies of glycerol metabolism in the heart have largely emphasized its role in triglyceride synthesis. However, glycerol may also be oxidized in the citric acid cycle, and glycogen synthesis from glycerol has been reported in the nonmammalian myocardium. The intent of this study was to test the hypothesis that glycerol may be metabolized to glycogen in mammalian heart. Isolated rat hearts were supplied with a mixture of substrates including glucose, lactate, pyruvate, octanoate, [U-13C3]glycerol, and 2H2O to probe various metabolic pathways including glycerol oxidation, glycolysis, the pentose phosphate pathway, and carbon sources of stored glycogen. NMR analysis confirmed that glycogen production from the level of the citric acid cycle did not occur and that the glycerol contribution to oxidation in the citric acid cycle was negligible in the presence of alternative substrates. Quite unexpectedly, 13C from [U-13C3]glycerol appeared in glycogen in carbon positions 4–6 of glucosyl units but none in positions 1–3. The extent of [4,5,6-13C3]glucosyl unit enrichment in glycogen was enhanced by insulin but decreased by H2O2. Given that triose phosphate isomerase is generally assumed to fully equilibrate carbon tracers in the triose pool, the marked 13C asymmetry in glycogen can only be attributed to conversion of [U-13C3]glycerol to [U-13C3]dihydroxyacetone phosphate and [U-13C3]glyceraldehyde 3-phosphate followed by rearrangements in the nonoxidative branch of the pentose phosphate pathway involving transaldolase that places this 13C-enriched 3-carbon unit only in the bottom half of hexose phosphate molecules contributing to glycogen. PMID:23235149

  1. Quantitative determination of mebeverine HCl by NMR chemical shift migration

    Microsoft Academic Search

    Ian S. Blagbrough; Manal S. Elmasry; Timothy J. Woodman; Hanaa M. Saleh; Afaf Aboul Kheir

    2009-01-01

    Quantitative 1H NMR spectroscopic methods are not frequently reported, but current NMR instrumentation allows ready access to such data. Mebeverine HCl is an attractive molecule for NMR spectroscopy teaching purposes as it possesses a variety of simple but significant functional groups; we fully assign its 1H and 13C NMR spectra. Using mebeverine HCl, we show that concentration changes, in water

  2. Current Topics Solution NMR of Large Molecules and Assemblies

    E-print Network

    Foster, Mark P.

    with the widespread use of uniform isotopic labeling of proteins and RNA with the NMR-active isotopes, 15N and 13C macromolecules (isotope labeling methods have expanded of uniform isotopic labeling of proteins and RNA with the NMR-active isotopes, 15 N and 13 C, opened the door

  3. NMR in molecular crystals

    NASA Astrophysics Data System (ADS)

    Decressain, R.; Amoureux, J. P.; Carpentier, L.; Nagy, J. B.

    The 1H, 19F and 13C relaxation times of fluoroadamantane C10H15F are measured over a wide temperature range. These relaxation times are analysed with two dynamical descriptions: an isotropic rotational diffusion and a Frenkel jump model. In this jump model, the structural equilibrium positions are taken into account and therefore two molecular motions are able to explain adequately the experimental results obtained in the plastic phase: a three-fold uniaxial rotation around the dipolar C-F axis and a tumbling reorientation of this axis between <111> cubic axes. The refinements are first carried out using 1H and 19F NMR results in conjunction with the residence time deduced from the dielectric relaxation. Finally, by introducing the 13C NMR results obtained in the plastic phase a precise determination of the two residence time can be made from the NMR results alone.

  4. Carbon partitioning in soybean (Glycine max) leaves by combined (11) C and (13) C labeling.

    PubMed

    Dirks, Rebecca C; Singh, Manmilan; Potter, Gregory S; Sobotka, Lee G; Schaefer, Jacob

    2012-12-01

    We labeled soybean (Glycine max) leaves with 200 and 600 ppm (13) CO(2) spiked with (11) CO(2) and examined the effects of light intensity and water stress on metabolism by using a combination of direct positron imaging and solid-state (13) C nuclear magnetic resonance (NMR) of the same leaf. We first made 60-min movies of the transport of photosynthetically assimilated (11) C labels. The positron imaging identified zones or patches within which variations in metabolism could be probed later by NMR. At the end of each movie, the labeled leaf was frozen in liquid nitrogen to stop metabolism, the leaf was lyophilized, and solid-state NMR was used either on the whole leaf or on various leaf fragments. The NMR analysis determined total (13) C incorporation into sugars, starch, proteins, and protein precursors. The combination of (11) C and (13) C analytical techniques has led to three major conclusions regarding photosynthetically heterogeneous soybean leaves: transient starch deposition is not the temporary storage of sucrose excluded from a saturated sugar-transport system; peptide synthesis is reduced under high-light, high CO(2) conditions; and all glycine from the photorespiratory pathway is routed to proteins within photosynthetically active zones when the leaf is water stressed and under high-light and low CO(2) conditions. PMID:22998467

  5. (13)C-labelled microdialysis studies of cerebral metabolism in TBI patients.

    PubMed

    Carpenter, Keri L H; Jalloh, Ibrahim; Gallagher, Clare N; Grice, Peter; Howe, Duncan J; Mason, Andrew; Timofeev, Ivan; Helmy, Adel; Murphy, Michael P; Menon, David K; Kirkpatrick, Peter J; Carpenter, T Adrian; Sutherland, Garnette R; Pickard, John D; Hutchinson, Peter J

    2014-06-16

    Human brain chemistry is incompletely understood and better methodologies are needed. Traumatic brain injury (TBI) causes metabolic perturbations, one result of which includes increased brain lactate levels. Attention has largely focussed on glycolysis, whereby glucose is converted to pyruvate and lactate, and is proposed to act as an energy source by feeding into neurons' tricarboxylic acid (TCA) cycle, generating ATP. Also reportedly upregulated by TBI is the pentose phosphate pathway (PPP) that does not generate ATP but produces various molecules that are putatively neuroprotective, antioxidant and reparative, in addition to lactate among the end products. We have developed a novel combination of (13)C-labelled cerebral microdialysis both to deliver (13)C-labelled substrates into brains of TBI patients and recover the (13)C-labelled metabolites, with high-resolution (13)C NMR analysis of the microdialysates. This methodology has enabled us to achieve the first direct demonstration in humans that the brain can utilise lactate via the TCA cycle. We are currently using this methodology to make the first direct comparison of glycolysis and the PPP in human brain. In this article, we consider the application of (13)C-labelled cerebral microdialysis for studying brain energy metabolism in patients. We set this methodology within the context of metabolic pathways in the brain, and (13)C research modalities addressing them. PMID:24361470

  6. 13C-labelled microdialysis studies of cerebral metabolism in TBI patients?

    PubMed Central

    Carpenter, Keri L.H.; Jalloh, Ibrahim; Gallagher, Clare N.; Grice, Peter; Howe, Duncan J.; Mason, Andrew; Timofeev, Ivan; Helmy, Adel; Murphy, Michael P.; Menon, David K.; Kirkpatrick, Peter J.; Carpenter, T. Adrian; Sutherland, Garnette R.; Pickard, John D.; Hutchinson, Peter J.

    2014-01-01

    Human brain chemistry is incompletely understood and better methodologies are needed. Traumatic brain injury (TBI) causes metabolic perturbations, one result of which includes increased brain lactate levels. Attention has largely focussed on glycolysis, whereby glucose is converted to pyruvate and lactate, and is proposed to act as an energy source by feeding into neurons’ tricarboxylic acid (TCA) cycle, generating ATP. Also reportedly upregulated by TBI is the pentose phosphate pathway (PPP) that does not generate ATP but produces various molecules that are putatively neuroprotective, antioxidant and reparative, in addition to lactate among the end products. We have developed a novel combination of 13C-labelled cerebral microdialysis both to deliver 13C-labelled substrates into brains of TBI patients and recover the 13C-labelled metabolites, with high-resolution 13C NMR analysis of the microdialysates. This methodology has enabled us to achieve the first direct demonstration in humans that the brain can utilise lactate via the TCA cycle. We are currently using this methodology to make the first direct comparison of glycolysis and the PPP in human brain. In this article, we consider the application of 13C-labelled cerebral microdialysis for studying brain energy metabolism in patients. We set this methodology within the context of metabolic pathways in the brain, and 13C research modalities addressing them. PMID:24361470

  7. Recoupled long-range C-H dipolar dephasing in solid-state NMR, and its use for spectral selection of fused aromatic rings.

    PubMed

    Mao, J-D; Schmidt-Rohr, K

    2003-05-01

    This work introduces a simple new solid-state 13C NMR method for distinguishing various types of aromatic residues, e.g. those of lignin from fused rings of charcoal. It is based on long-range dipolar dephasing, which is achieved by recoupling of long-range C-H dipolar interactions, using two 1H 180 degrees pulses per rotation period. This speeds up dephasing of unprotonated carbon signals approximately threefold compared to standard dipolar dephasing without recoupling and thus provides much more efficient differential dephasing. It also reduces the effects of spinning-speed dependent effective proton-proton dipolar couplings on the heteronuclear dephasing. Signals of unprotonated carbons with two or more protons at a two-bond distance dephase to <3% within less than 0.9 ms, significantly faster than those of aromatic sites separated from the nearest proton by three or more bonds. Differential dephasing among different unprotonated carbons is demonstrated in a substituted anthraquinone and 3-methoxy benzamide. The data yield a calibration curve for converting the dephasing rates into estimated distances from the carbon to the nearest protons. This can be used for peak assignment in heavily substituted or fused aromatic molecules. Compared to lignin, slow dephasing is observed for the aromatic carbons in wood charcoal, and even slower for inorganic carbonate. Direct 13C polarization is used on these structurally complex samples to prevent loss of the signals of interest, which by design originate from carbons that are distant from protons and therefore crosspolarize poorly. In natural organic matter such as humic acids, this combination of recoupled dipolar dephasing and direct polarization at 7-kHz MAS enables selective observation of signals from fused rings that are characteristic of charcoal. PMID:12762998

  8. Recoupled long-range C-H dipolar dephasing in solid-state NMR, and its use for spectral selection of fused aromatic rings

    NASA Astrophysics Data System (ADS)

    Mao, J.-D.; Schmidt-Rohr, K.

    2003-05-01

    This work introduces a simple new solid-state 13C NMR method for distinguishing various types of aromatic residues, e.g. those of lignin from fused rings of charcoal. It is based on long-range dipolar dephasing, which is achieved by recoupling of long-range C-H dipolar interactions, using two 1H 180° pulses per rotation period. This speeds up dephasing of unprotonated carbon signals approximately threefold compared to standard dipolar dephasing without recoupling and thus provides much more efficient differential dephasing. It also reduces the effects of spinning-speed dependent effective proton-proton dipolar couplings on the heteronuclear dephasing. Signals of unprotonated carbons with two or more protons at a two-bond distance dephase to <3% within less than 0.9 ms, significantly faster than those of aromatic sites separated from the nearest proton by three or more bonds. Differential dephasing among different unprotonated carbons is demonstrated in a substituted anthraquinone and 3-methoxy benzamide. The data yield a calibration curve for converting the dephasing rates into estimated distances from the carbon to the nearest protons. This can be used for peak assignment in heavily substituted or fused aromatic molecules. Compared to lignin, slow dephasing is observed for the aromatic carbons in wood charcoal, and even slower for inorganic carbonate. Direct 13C polarization is used on these structurally complex samples to prevent loss of the signals of interest, which by design originate from carbons that are distant from protons and therefore crosspolarize poorly. In natural organic matter such as humic acids, this combination of recoupled dipolar dephasing and direct polarization at 7-kHz MAS enables selective observation of signals from fused rings that are characteristic of charcoal.

  9. Application of 13C Nuclear Magnetic Resonance To Elucidate the Unexpected Biosynthesis of Erythritol by Leuconostoc oenos

    PubMed Central

    Veiga-Da-Cunha, Maria; Firme, Paula; Romão, M. Vitória San; Santos, Helena

    1992-01-01

    Natural-abundance 13C nuclear magnetic resonance (13C-NMR) revealed the production of erythritol and glycerol by nongrowing cells of Leuconostoc oenos metabolizing glucose. The ratio of erythritol to glycerol was strongly influenced by the aeration conditions of the medium. The elucidation of the metabolic pathway responsible for erythritol production was achieved by 13C-NMR and 1H-NMR spectroscopy using specifically 13C-labelled d-glucose. The 1H-NMR spectrum of the cell supernatant resulting from the metabolism of [2-13C]glucose showed that only 75% of the glucose supplied was metabolized heterofermentatively and that the remaining 25% was channelled to the production of erythritol. The synthesis of this polyol resulted from the reduction of the C-4 moiety of the intermediate fructose 6-phosphate. Oxygen has an inhibitory effect on the production of erythritol by L. oenos. Preaeration of a suspension of nongrowing cells of L. oenos resulted in 30% less erythritol and in 70% more glycerol formed during the anaerobic metabolism of glucose. The anaerobic production of erythritol from glucose was also found in growing cultures of L. oenos, although to a smaller extent. PMID:16348738

  10. Synthesis Of [2h, 13c] And [2h3, 13c]Methyl Aryl Sulfides

    DOEpatents

    Martinez, Rodolfo A. (Santa Fe, NM); Alvarez, Marc A. (Santa Fe, NM); Silks, III, Louis A. (Los Alamos, NM); Unkefer, Clifford J. (Los Alamos, NM)

    2004-03-30

    The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2,.sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms. The present invention is also directed to the labeled compounds of [.sup.2 H.sub.1, .sup.13 C]methyl iodide and [.sup.2 H.sub.2, .sup.13 C]methyl iodide.

  11. Supporting Information A Multinuclear NMR Study of the Solution Structure and Reactivity of

    E-print Network

    Reich, Hans J.

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S-19 6 Li, 31 P, and 13 C NMR Spectroscopy of 0.08 M 1-6 Li in Ether Titrated with HMPA . . . . . . . . . S-21 6 Li, 31 P, and 13 C NMR Spectroscopy of 2-6 Li in 3:2 THF/ether Titrated with HMPA . . . . . . . . S-22 6 Li, 31 P, and 13 C NMR spectroscopy of 2-6 Li in Ether Titrated with HMPA

  12. Assignment of congested NMR spectra: Carbonyl backbone enrichment via the Entner Doudoroff pathway

    NASA Astrophysics Data System (ADS)

    Goldbourt, Amir; Day, Loren A.; McDermott, Ann E.

    2007-12-01

    In NMR spectra of complex proteins, sparse isotope enrichment can be important, in that the removal of many 13C- 13C homonuclear J-couplings can narrow the lines and thereby facilitate the process of spectral assignment and structure elucidation. We present a simple scheme for selective yet extensive isotopic enrichment applicable for production of proteins in organisms utilizing the Entner-Doudoroff (ED) metabolic pathway. An enrichment scheme so derived is demonstrated in the context of a magic-angle spinning solid-state NMR (MAS SSNMR) study of Pf1 bacteriophage, the host of which is Pseudomonas aeruginosa, strain K (PAK), an organism that uses the ED pathway for glucose catabolism. The intact and infectious Pf1 phage in this study was produced by infected PAK cells grown on a minimal medium containing 1- 13C D-glucose ( 13C in position 1) as the sole carbon source, as well as 15NH 4Cl as the only nitrogen source. The 37 MDa Pf1 phage consists of about 93% major coat protein, 1% minor coat proteins, and 6% single-stranded, circular DNA. As a consequence of this composition and the enrichment scheme, the resonances in the MAS SSNMR spectra of the Pf1 sample were almost exclusively due to carbonyl carbons in the major coat protein. Moreover, 3D heteronuclear NCOCX correlation experiments also show that the amino acids leucine, serine, glycine, and tyrosine were not isotopically enriched in their carbonyl positions (although most other amino acids were), which is as expected based upon considerations of the ED metabolic pathway. 3D NCOCX NMR data and 2D 15N- 15N data provided strong verification of many previous assignments of 15N amide and 13C carbonyl shifts in this highly congested spectrum; both the semi-selective enrichment patterns and the narrowed linewidths allowed for greater certainty in the assignments as compared with use of uniformly enriched samples alone.

  13. Chemical structural studies of natural lignin by dipolar dephasing solid-state 13C nuclear magnetic resonance

    USGS Publications Warehouse

    Hatcher, P.G.

    1987-01-01

    Two natural lignins, one from a gymnosperm wood the other from angiosperm wood, were examined by conventional solid-state and dipolar dephasing 13C nuclear magnetic resonance (NMR) techniques. The results obtained from both techniques show that the structure of natural lignins is consistent with models of softwood and hardwood lignin. The dipolar dephasing NMR data provide a measure of the degree of substitution on aromatic rings which is consistent with the models. ?? 1987.

  14. Robust hyperpolarized (13) C metabolic imaging with selective non-excitation of pyruvate (SNEP).

    PubMed

    Chen, Way Cherng; Teo, Xing Qi; Lee, Man Ying; Radda, George K; Lee, Philip

    2015-08-01

    In vivo metabolic imaging using hyperpolarized [1-(13) C]pyruvate provides localized biochemical information and is particularly useful in detecting early disease changes, as well as monitoring disease progression and treatment response. However, a major limitation of hyperpolarized magnetization is its unrecoverable decay, due not only to T1 relaxation but also to radio-frequency (RF) excitation. RF excitation schemes used in metabolic imaging must therefore be able to utilize available hyperpolarized magnetization efficiently and robustly for the optimal detection of substrate and metabolite activities. In this work, a novel RF excitation scheme called selective non-excitation of pyruvate (SNEP) is presented. This excitation scheme involves the use of a spectral selective RF pulse to specifically exclude the excitation of [1-(13) C]pyruvate, while uniformly exciting the key metabolites of interest (namely [1-(13) C]lactate and [1-(13) C]alanine) and [1-(13) C]pyruvate-hydrate. By eliminating the loss of hyperpolarized [1-(13) C]pyruvate magnetization due to RF excitation, the signal from downstream metabolite pools is increased together with enhanced dynamic range. Simulation results, together with phantom measurements and in vivo experiments, demonstrated the improvement in signal-to-noise ratio (SNR) and the extension of the lifetime of the [1-(13) C]lactate and [1-(13) C]alanine pools when compared with conventional non-spectral selective (NS) excitation. SNEP has also been shown to perform comparably well with multi-band (MB) excitation, yet SNEP possesses distinct advantages, including ease of implementation, less stringent demands on gradient performance, increased robustness to frequency drifts and B0 inhomogeneity as well as easier quantification involving the use of [1-(13) C]pyruvate-hydrate as a proxy for the actual [1-(13) C] pyruvate signal. SNEP is therefore a promising alternative for robust hyperpolarized [1-(13) C]pyruvate metabolic imaging with high fidelity. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26119950

  15. /sup 13/C nuclear magnetic resonance studies of the biosynthesis by Microbacterium ammoniaphilum of L-glutamate selectively enriched with carbon-13

    SciTech Connect

    Walker, T.E.; Han, C.H.; Kollman, V.H.; London, R.E.; Matwiyoff, N.A.

    1982-02-10

    /sup 13/C NMR of isotopically enriched metabolites has been used to study the metabolism of Microbacterium ammoniaphilum, a bacterium which excretes large quantities of L-glutamic acid into the medium. Biosynthesis from 90% (1-/sup 13/C) glucose results in relatively high specificity of the label, with (2,4-/sup 13/C/sub 2/) glutamate as the major product. The predominant biosynthetic pathway for synthesis of glutamate from glucose was determined to be the Embden Meyerhof glycolytic pathway followed by P-enolpyruvate carboxylase and the first third of the Krebs cycle. Different metabolic pathways are associated with different correlations in the enrichment of the carbons, reflected in the spectrum as different /sup 13/C-/sup 13/C scalar multiplet intensities. Hence, intensity and /sup 13/C-/sup 13/C multiplet analysis allows quantitation of the pathways involved. Although blockage of the Krebs cycle at the ..cap alpha..-ketoglutarate dehydrogenase step is the basis for the accumulation of glutamate, significant Krebs cycle activity was found in glucose grown cells, and extensive Krebs cycle activity in cells metabolizing (1-/sup 13/C) acetate. In addition to the observation of the expected metabolites, the disaccharide ..cap alpha..,..cap alpha..-trehalose and ..cap alpha..,..beta..-glucosylamine were identified from the /sup 13/C NMR spectra.

  16. Determination of (13)C (?) relaxation times in uniformly (13)C/ (15)N-enriched proteins.

    PubMed

    Engelke, J; Rüterjans, H

    1995-02-01

    Relaxation times of (13)C(?) carbons of uniformly (13)C/(15)N-enriched probes have been investigated. The relaxation behaviour was analyzed in terms of a multispin system. Pulse sequences for the determination of T(1), T(2) and the heteronuclear NOE of (13)C(?) in uniformly (13)C/(15)N-enriched ribonuclease T1 are presented. The experiments performed in order to obtain T(1) and the heteronuclear NOE were similar to those of the corresponding (15)N experiments published previously. The determination of T(2) for the C(?)-carbon in a completely labeled protein is more complicated, since the magnetization transfer during the T(2) evolution period owing to the scalar coupling of C(?)-C(?) must be suppressed. Various different pulse sequences for the T(2) evolution period were simulated in order to optimize the bandwidth for which reliable T(2) relaxation times can be obtained. A proof for the quality of these pulse sequences is given by fitting the intensity decay of individual (1)H-(13)C(?) cross peaks, in a series of ((1)H, (13)C)-ct-HSQC spectra with a modified CPMG sequence as well as a T(1p) sequence for the transverse relaxation time, to a single exponential using a simplex algorithm. PMID:22911465

  17. Intermolecular Packing and Alignment in an Ordered -Hairpin Antimicrobial Peptide Aggregate from 2D Solid-State NMR

    E-print Network

    Hong, Mei

    -bonding propensity. Incubation of PG-1 in phosphate buffer saline produced well-ordered nanometer-scale aggregates, as indicated by 13 C and 15 N NMR line widths, chemical shifts, and electron microscopy. Two-dimensional 13 C

  18. Phase transition in triglycine sulfate crystals by 1H and 13C nuclear magnetic resonance in the rotating frame

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Jeong, Se-Young

    2013-09-01

    The ferroelectric phase transition in triglycine sulfate ((NH2CH2COOH)3·H2SO4, TGS)) crystals, occurring at TC of 322 K, was studied using 1H and 13C CP/MAS NMR. From the spin-lattice relaxation time in the rotating frame, T1?, of 1H and 13C, we found that the slopes of the T1? versus temperature curve changed near TC. In addition, the change of intensities for the protons and carbons NMR signals in the ferroelectric and the paraelectric phases led to the noticeable changes in the environments of proton and carbon in the carboxyl groups. The carboxyl ordering was the dominant factor driving the phase transition. Our study of the 1H and 13C spectra showed that the ferroelectric phase transition of TGS is of the order-disorder type due to ordering of the carboxyl groups.

  19. Simulation of 13C nuclear magnetic resonance spectra of lignin compounds using principal component analysis and artificial neural networks

    NASA Astrophysics Data System (ADS)

    Jalali-Heravi, M.; Masoum, S.; Shahbazikhah, P.

    2004-11-01

    Theoretical models relating atom-based structural descriptors to 13C NMR chemical shifts were used to accurately simulate 13C NMR spectra of lignin model compounds (poly-substituted phenols). The structure-activity relationship (SAR) studies for 15 lignins using pattern recognition methods of principal component analysis (PCA) and artificial neural networks (ANNs) were performed in this work. The most important parameters affecting the 13C chemical shifts of different carbons were descriptors consisting of the charge density of the atoms at different distances from the center carbon. Among the large number of parameters, these descriptors were selected using PCA and were used as ANN input. The least square regression analyses of the results indicate correlation coefficient ( R) values in excess of 0.983 for the total data set.

  20. Solving structures by NMR Qinghua Wang

    E-print Network

    Hardy, Jeanne

    and 15NH4Cl for E. coli). Disadvantage is the substantial cost of isotopic labeling. #12;N H O OH N H O N (BPTI) from NOE derived dist restraints 1987 3D NMR: 13C, 15N labeling of recombinant proteins 1990 as a whole, leading to broad peaks. Problem #1 can be overcome by labeling protein with other NMR- sensitive

  1. Simultaneous continuous 13C, 12C analysis of expired gas in the 13C breath test.

    PubMed

    Ichinose, Y; Kanai, E; Yamasawa, F; Nishi, I; Toyama, K

    1998-03-01

    The 13C breath test is a method of clarifying the metabolism of loaded substances by administering 13C-labelled materials and calculating the 13CO2 and 12CO2 ratio (13C/12C isotope ratio) in the expired gas. The materials are metabolized and expelled in the expired gas. Because simultaneous continuous measurement of 13CO2 and 12CO2 in expired gas has been difficult up to the present, respective expired gases, including dead space before and after administration, have been sampled to separate sampling bags and 13C/12C has been measured in the bags and changed fraction of 13C/12C after administration (delta) has been used to judge the metabolic process. This method is affected by the contamination of the dead space gas. In the present study, in order to exclude the dead space effect, simultaneous continuous analysis of 12CO2 and 13CO2 of expired gas identifying alveolar gas was applied to the 13C-urea breath test in addition to the conventional sampling bag method. Both isotope detectors were attached to a mass spectrometer. Fifty-six cases receiving stomach health check-ups for Helicobacter pylori were examined. Delta was calculated in the bag or in phase III of continuous gas measurement. Because the bag contains dead space, delta was reduced and sensitivity and specificity with reference to gastric fluoroscopy or Helicobacter pylori IgG antibody were reduced. Decreasing the dead space contamination is important in reducing the measurement error in the 13C breath test and simultaneous continuous measurement is a good tool for this purpose. PMID:9657655

  2. Artificial Neural Network Approach for NMR Data Analyses

    E-print Network

    Schouten, Theo

    : : : : : : : : : : : : : : : : : : : : : : : : : : 25 3.7.2 13 C NMR : : : : : : : : : : : : : : : : : : : : : : : : : 26 3.7.3 31 P NMR 3.1 Meaning of a NMR­Spectrum : : : : : : : : : : : : : : : : : : 19 3.2 The Fourier TransformArtificial Neural Network Approach for NMR Data Analyses E.R. de Blouw (9102337) Master Thesis no

  3. Multisite Kinetic Modeling of 13C Metabolic MR Using [1-13C]Pyruvate

    PubMed Central

    Gómez Damián, Pedro A.; Sperl, Jonathan I.; Janich, Martin A.; Khegai, Oleksandr; Wiesinger, Florian; Glaser, Steffen J.; Haase, Axel; Schwaiger, Markus; Schulte, Rolf F.; Menzel, Marion I.

    2014-01-01

    Hyperpolarized 13C imaging allows real-time in vivo measurements of metabolite levels. Quantification of metabolite conversion between [1-13C]pyruvate and downstream metabolites [1-13C]alanine, [1-13C]lactate, and [13C]bicarbonate can be achieved through kinetic modeling. Since pyruvate interacts dynamically and simultaneously with its downstream metabolites, the purpose of this work is the determination of parameter values through a multisite, dynamic model involving possible biochemical pathways present in MR spectroscopy. Kinetic modeling parameters were determined by fitting the multisite model to time-domain dynamic metabolite data. The results for different pyruvate doses were compared with those of different two-site models to evaluate the hypothesis that for identical data the uncertainty of a model and the signal-to-noise ratio determine the sensitivity in detecting small physiological differences in the target metabolism. In comparison to the two-site exchange models, the multisite model yielded metabolic conversion rates with smaller bias and smaller standard deviation, as demonstrated in simulations with different signal-to-noise ratio. Pyruvate dose effects observed previously were confirmed and quantified through metabolic conversion rate values. Parameter interdependency allowed an accurate quantification and can therefore be useful for monitoring metabolic activity in different tissues. PMID:25548671

  4. Stereoregularity evolution of methyl acrylate and vinyl acetate copolymers by 2D NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Brar, A. S.; Goyal, Ashok Kumar; Ganai, Anal; Hooda, Sunita

    2008-10-01

    Copolymers of methyl acrylate (M) and vinyl acetate (V) were synthesized by free radical bulk polymerization using azobisisobutyronitrile (AIBN) as an initiator at 70 °C and their composition were calculated from 1H NMR spectra. These copolymer compositions were further used to calculate reactivity ratios of V/M copolymers. The reactivity ratios obtained from linear Kelen-Tudos (KT) and non-linear error-in-variable methods (EVM) are rM = 6.74 ± 1.03, rV = 0.04 ± 0.01 and rM = 6.72, rV = 0.04, respectively. The copolymers were analyzed for their stereochemical structure utilizing various 1D ( 1H, 13C{ 1H}, DEPT) and 2D (HSQC, TOCSY, HMBC) NMR techniques. 2D HSQC and TOCSY NMR experiments were employed to resolve the highly overlapped and complex 1H and 13C{ 1H} NMR spectra of copolymers. The complete spectral assignment of carbonyl carbons were done with the help of 2D HMBC spectra. The carbonyl carbon was found to be sensitive up to pentad configurational sequences and shows three and four bond couplings with methine and methylene protons.

  5. NMR spectroscopic analysis of lotusine.

    PubMed

    Yang, Jian

    2005-02-01

    Lotusine, a soluble alkaloid, is one of the major constituents of the Chinese medicine Lotus Plumule, and has antihypertension and antibacterial activity. In order to confirm the structures reported in the literature by explicit 1H and 13C assignments, we applied a series of NMR experiments including 1H-1H COSY, HSQC and HMBC. PMID:15562520

  6. Canopy-scale d13 C of photosynthetic and respiratory

    E-print Network

    Canopy-scale d13 C of photosynthetic and respiratory CO2 fluxes: observations in forest biomes the inversion technique. This approach is very sensitive to estimates of photosynthetic 13 C discrimination

  7. Novel methods based on 13C detection to study intrinsically disordered proteins

    NASA Astrophysics Data System (ADS)

    Felli, Isabella C.; Pierattelli, Roberta

    2014-04-01

    Intrinsically disordered proteins (IDPs) are characterized by highly flexible solvent exposed backbones and can sample many different conformations. These properties confer them functional advantages, complementary to those of folded proteins, which need to be characterized to expand our view of how protein structural and dynamic features affect function beyond the static picture of a single well defined 3D structure that has influenced so much our way of thinking. NMR spectroscopy provides a unique tool for the atomic resolution characterization of highly flexible macromolecules in general and of IDPs in particular. The peculiar properties of IDPs however have profound effects on spectroscopic parameters. It is thus worth thinking about these aspects to make the best use of the great potential of NMR spectroscopy to contribute to this fascinating field of research. In particular, after many years of dealing with exclusively heteronuclear NMR experiments based on 13C direct detection, we would like here to address their relevance when studying IDPs.

  8. Exploiting the Synergy of Powder X-ray Diffraction and Solid-State NMR Spectroscopy in Structure Determination of Organic Molecular Solids

    PubMed Central

    2013-01-01

    We report a strategy for structure determination of organic materials in which complete solid-state nuclear magnetic resonance (NMR) spectral data is utilized within the context of structure determination from powder X-ray diffraction (XRD) data. Following determination of the crystal structure from powder XRD data, first-principles density functional theory-based techniques within the GIPAW approach are exploited to calculate the solid-state NMR data for the structure, followed by careful scrutiny of the agreement with experimental solid-state NMR data. The successful application of this approach is demonstrated by structure determination of the 1:1 cocrystal of indomethacin and nicotinamide. The 1H and 13C chemical shifts calculated for the crystal structure determined from the powder XRD data are in excellent agreement with those measured experimentally, notably including the two-dimensional correlation of 1H and 13C chemical shifts for directly bonded 13C–1H moieties. The key feature of this combined approach is that the quality of the structure determined is assessed both against experimental powder XRD data and against experimental solid-state NMR data, thus providing a very robust validation of the veracity of the structure. PMID:24386493

  9. Optoacoustic 13C-breath test analyzer

    NASA Astrophysics Data System (ADS)

    Harde, Hermann; Helmrich, Günther; Wolff, Marcus

    2010-02-01

    The composition and concentration of exhaled volatile gases reflects the physical ability of a patient. Therefore, a breath analysis allows to recognize an infectious disease in an organ or even to identify a tumor. One of the most prominent breath tests is the 13C-urea-breath test, applied to ascertain the presence of the bacterium helicobacter pylori in the stomach wall as an indication of a gastric ulcer. In this contribution we present a new optical analyzer that employs a compact and simple set-up based on photoacoustic spectroscopy. It consists of two identical photoacoustic cells containing two breath samples, one taken before and one after capturing an isotope-marked substrate, where the most common isotope 12C is replaced to a large extent by 13C. The analyzer measures simultaneously the relative CO2 isotopologue concentrations in both samples by exciting the molecules on specially selected absorption lines with a semiconductor laser operating at a wavelength of 2.744 ?m. For a reliable diagnosis changes of the 13CO2 concentration of 1% in the exhaled breath have to be detected at a concentration level of this isotope in the breath of about 500 ppm.

  10. Multiplet component separation for measurement of methyl 13C-1H dipolar couplings in weakly aligned proteins.

    PubMed

    Kontaxis, G; Bax, A

    2001-05-01

    A simple spectral editing procedure is described that generates separate subspectra for the methyl 13C-[1H3] multiplet components of 1H-13C HSQC spectra. The editing procedure relies on co-addition of in-phase and antiphase spectra and yields 1H-coupled constant-time HSQC subspectra for the methyl region that have the simplicity of the regular decoupled CT-HSQC spectrum. Resulting spectra permit rapid and reliable measurement of 1H-13C J and dipolar couplings. The editing procedure is illustrated for a Ca2+-calmodulin sample in isotropic and liquid crystalline phases. PMID:11430758

  11. [Characterization of biochar by X-ray photoelectron spectroscopy and 13C nuclear magnetic resonance].

    PubMed

    Xu, Dong-yu; Jin, Jie; Yan, Yu; Han, Lan-fang; Kang, Ming-jie; Wang, Zi-ying; Zhao, Ye; Sun, Ke

    2014-12-01

    The wood (willow branch) and grass (rice straw) materials were pyrolyzed at different temperatures (300, 450 and 600 °C) to obtain the biochars used in the present study. The biochars were characterized using elementary analysis, X-ray photoelectron spectroscopy (XPS) and solid state 13C cross-polarization and magic angle spinning nuclear magnetic resonance spectroscopy (13C NMR) to illuminate the structure and composition of the biochars which were derived from the different thermal temperatures and biomass. The results showed that the H/C, O/C and (O+N)/C ratios of the biochars decreased with the increase in the pyrolysis temperatures. The surface polarity and ash content of the grass-derived biochars were higher than those of the wood-derived biochars. The minerals of the wood-derived biochars were mainly covered by the organic matter; in contrast, parts of the mineral surfaces of the grass-derived biochars were not covered by organic matter? The 13C NMR of the low temperature-derived biochars revealed a large contribution of aromatic carbon, aliphatic carbon, carboxyl and carbonyl carbon, while the high temperature-derived biochars contained a large amount of aromatic carbon. Moreover, the wood-derived biochars produced at low heat treatment temperatures contained more lignin residues than grass-derived ones, probably due to the existence of high lignin content in the feedstock soures of wood-derived biochars. The results of the study would be useful for environmental application of biochars. PMID:25881450

  12. (13)C isotopic fractionation during biodegradation of agricultural wastes.

    PubMed

    Chalk, Phillip M; Inácio, Caio T; Urquiaga, Segundo; Chen, Deli

    2015-06-01

    Significant differences in ?(13)C signatures occur within and between plant tissues and their constituent biochemical entities, and also within and between heterotrophic bacteria and fungi and their metabolic products. Furthermore, (13)C isotopic fractionation occurs during the biodegradation of organic molecules as seen in the substrate, respired CO2 and the microbial biomass, which could be related to substrate composition and/or microbial metabolism. The (13)C isotopic fractionation observed during the decomposition of a single defined C substrate appears to be due to the intra-molecular heterogeneity in (13)C in the substrate and to (13)C isotopic fractionation during microbial metabolism. Very limited data suggest that the latter may be quantitatively more important than the former. Studies with defined fungi in culture media have highlighted the complexities associated with the interpretation of the observed patterns of (13)C isotopic fractionation when a single defined C source is added to the culture medium which itself contains one or more C sources. Techniques involving (13)C enrichment or paired treatments involving an equivalent C3- and C4-derived substrate have been devised to overcome the problem of background C in the culture medium and (13)C isotopic fractionation during metabolism. Studies with complex substrates have shown an initial (13)C depletion phase in respired CO2 followed by a (13)C enrichment phase which may or may not be followed by another (13)C depletion phase. Basic studies involving an integrated approach are required to gain a new insight into (13)C isotopic fractionation during organic residue decomposition, by simultaneous measurements of ?(13)C in all C moieties. New analytical tools to measure real-time changes in ?(13)CO2 and the intra-molecular ?(13)C distribution within plant biochemical entities offer new opportunities for unravelling the complex interactions between substrate and microbial metabolism with respect to (13)C isotopic fractionation during biodegradation. PMID:25768051

  13. Biosynthetic production of universally (13)C-labelled polyunsaturated fatty acids as reference materials for natural health product research.

    PubMed

    Le, Phuong Mai; Fraser, Catherine; Gardner, Graeme; Liang, Wei-Wan; Kralovec, Jaroslav A; Cunnane, Stephen C; Windust, Anthony J

    2007-09-01

    Long-chain polyunsaturated fatty acids (LCPUFA) including eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) have become important natural health products with numerous proven benefits related to brain function and cardiovascular health. Not only are omega-3 fatty acids available in a plethora of dietary supplements, but they are also increasingly being incorporated as triglycerides into conventional foods, including bread, milk, yoghurt and confectionaries. Recently, transgenic oil seed crops and livestock have been developed that enhance omega-3 fatty acid content. This diverse array of matrices presents a difficult analytical challenge and is compounded further by samples generated through clinical research. Stable isotope (13)C-labelled LCPUFA standards offer many advantages as research tools because they may be distinguished from their naturally abundant counterparts by mass spectrometry and directly incorporated as internal standards into analytical procedures. Further, (13)C-labelled LCPUFAs are safe to use as metabolic tracers to study uptake and metabolism in humans. Currently, (13)C-labelled LCPUFAs are expensive, available in limited supply and not in triglyceride form. To resolve these issues, marine heterotrophic microorganisms are being isolated and screened for LCPUFA production with a view to the efficient biosynthetic production of U-(13)C-labelled fatty acids using U-(13)C glucose as a carbon source. Of 37 isolates obtained, most were thraustochytrids, and either DHA or omega-6 docosapentaenoic acid (22:5n-6) were produced as the major LCPUFA. The marine protist Hyalochlorella marina was identified as a novel source of EPA and omega-3 docosapentaenoic acid (22:5n-3). As proof of principle, gram-level production of (13)C-labelled DHA has been achieved with high chemical purity ( >99%) and high (13)C incorporation levels (>90%), as confirmed by NMR and MS analyses. Finally, U-(13)C-DHA was enzymatically re-esterified to glycerol to yield a (13)C-labelled tridocosahexaenoin. PMID:17486321

  14. Use of 13C nuclear magnetic resonance to assess fossil fuel biodegradation: fate of [1-13C]acenaphthene in creosote polycyclic aromatic compound mixtures degraded by bacteria.

    PubMed

    Selifonov, S A; Chapman, P J; Akkerman, S B; Gurst, J E; Bortiatynski, J M; Nanny, M A; Hatcher, P G

    1998-04-01

    [1-13C]acenaphthene, a tracer compound with a nuclear magnetic resonance (NMR)-active nucleus at the C-1 position, has been employed in conjunction with a standard broad-band-decoupled 13C-NMR spectroscopy technique to study the biodegradation of acenaphthene by various bacterial cultures degrading aromatic hydrocarbons of creosote. Site-specific labeling at the benzylic position of acenaphthene allows 13C-NMR detection of chemical changes due to initial oxidations catalyzed by bacterial enzymes of aromatic hydrocarbon catabolism. Biodegradation of [1-13C]acenaphthene in the presence of naphthalene or creosote polycyclic aromatic compounds (PACs) was examined with an undefined mixed bacterial culture (established by enrichment on creosote PACs) and with isolates of individual naphthalene- and phenanthrene-degrading strains from this culture. From 13C-NMR spectra of extractable materials obtained in time course biodegradation experiments under optimized conditions, a number of signals were assigned to accumulated products such as 1-acenaphthenol, 1-acenaphthenone, acenaphthene-1,2-diol and naphthalene 1,8-dicarboxylic acid, formed by benzylic oxidation of acenaphthene and subsequent reactions. Limited degradation of acenaphthene could be attributed to its oxidation by naphthalene 1,2-dioxygenase or related dioxygenases, indicative of certain limitations of the undefined mixed culture with respect to acenaphthene catabolism. Coinoculation of the mixed culture with cells of acenaphthene-grown strain Pseudomonas sp. strain A2279 mitigated the accumulation of partial transformation products and resulted in more complete degradation of acenaphthene. This study demonstrates the value of the stable isotope labeling approach and its ability to reveal incomplete mineralization even when as little as 2 to 3% of the substrate is incompletely oxidized, yielding products of partial transformation. The approach outlined may prove useful in assessing bioremediation performance. PMID:9546181

  15. Calculation of total meal d13C from individual food d13C.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Variations in the isotopic signature of carbon in biological samples can be used to distinguish dietary patterns and monitor shifts in metabolism. But for these variations to have meaning, the isotopic signature of the diet must be known. We sought to determine if knowledge of the 13C isotopic abund...

  16. CARBON-13 NUCLEAR MAGNETIC RESONANCE. 13C CHEMICAL SHIFTS AND 13C-199HG COUPLING CONSTANTS FOR SOME ORGANOMERCURY COMPOUNDS

    EPA Science Inventory

    The (13)C shieldings and (13)C-(199)Hg coupling constants of fourteen phenyl- and seven alkyl- and alkenyl-mercury compounds have been obtained. Substituent effects on the (13)C shieldings are similar to those in nonmercurated phenyl compounds, with a similar relationship between...

  17. Enzymatic Synthesis and Structural Characterization of 13C, 15N - Poly(ADP-ribose)

    PubMed Central

    Schultheisz, Heather L.; Szymczyna, Blair R.; Williamson, James R.

    2009-01-01

    Poly(ADP-ribose) is a significant nucleic acid polymer involved with diverse functions in eukaryotic cells, yet no structural information is available. A method for the synthesis of 13C, 15N- poly(ADP-ribose) (PAR) has been developed to allow characterization of the polymer using multidimensional nuclear magnetic resonance (NMR) spectroscopy. Successful integration of pentose phosphate, nicotinamide adenine dinucleotide biosynthesis, and cofactor recycling pathways with poly(ADP-ribose) polymerase-1 permitted labeling of PAR from 13C-glucose and 13C, 15N- ATP in a single pot reaction. The scheme is efficient, yielding ~ 400 nmoles of purified PAR from 5 ?moles ATP, and the behavior of the synthetic PAR is similar to data from PAR synthesized by cell extracts. The resonances for 13C, 15N-PAR were unambiguously assigned, but the polymer appears to be devoid of inherent regular structure. PAR may form an ordered macromolecular structure when interacting with proteins, and due to the extensive involvement of PAR in cell function and disease, further studies of PAR structure will be required. The labeled PAR synthesis reported here will provide an essential tool for the future study of PAR-protein complexes. PMID:19757771

  18. Sensitivity and resolution enhanced solid-state NMR for paramagnetic systems and biomolecules under very fast magic angle spinning.

    PubMed

    Parthasarathy, Sudhakar; Nishiyama, Yusuke; Ishii, Yoshitaka

    2013-09-17

    Recent research in fast magic angle spinning (MAS) methods has drastically improved the resolution and sensitivity of NMR spectroscopy of biomolecules and materials in solids. In this Account, we summarize recent and ongoing developments in this area by presenting (13)C and (1)H solid-state NMR (SSNMR) studies on paramagnetic systems and biomolecules under fast MAS from our laboratories. First, we describe how very fast MAS (VFMAS) at the spinning speed of at least 20 kHz allows us to overcome major difficulties in (1)H and (13)C high-resolution SSNMR of paramagnetic systems. As a result, we can enhance both sensitivity and resolution by up to a few orders of magnitude. Using fast recycling (?ms/scan) with short (1)H T1 values, we can perform (1)H SSNMR microanalysis of paramagnetic systems on the microgram scale with greatly improved sensitivity over that observed for diamagnetic systems. Second, we discuss how VFMAS at a spinning speed greater than ?40 kHz can enhance the sensitivity and resolution of (13)C biomolecular SSNMR measurements. Low-power (1)H decoupling schemes under VFMAS offer excellent spectral resolution for (13)C SSNMR by nominal (1)H RF irradiation at ?10 kHz. By combining the VFMAS approach with enhanced (1)H T1 relaxation by paramagnetic doping, we can achieve extremely fast recycling in modern biomolecular SSNMR experiments. Experiments with (13)C-labeled ubiquitin doped with 10 mM Cu-EDTA demonstrate how effectively this new approach, called paramagnetic assisted condensed data collection (PACC), enhances the sensitivity. Lastly, we examine (13)C SSNMR measurements for biomolecules under faster MAS at a higher field. Our preliminary (13)C SSNMR data of A? amyloid fibrils and GB1 microcrystals acquired at (1)H NMR frequencies of 750-800 MHz suggest that the combined use of the PACC approach and ultrahigh fields could allow for routine multidimensional SSNMR analyses of proteins at the 50-200 nmol level. Also, we briefly discuss the prospects for studying bimolecules using (13)C SSNMR under ultrafast MAS at the spinning speed of ?100 kHz. PMID:23889329

  19. Sensitivity and resolution enhancement of oriented solid-state NMR: application to membrane proteins.

    PubMed

    Gopinath, T; Mote, Kaustubh R; Veglia, Gianluigi

    2013-11-01

    Oriented solid-state NMR (O-ssNMR) spectroscopy is a major technique for the high-resolution analysis of the structure and topology of transmembrane proteins in native-like environments. Unlike magic angle spinning (MAS) techniques, O-ssNMR spectroscopy requires membrane protein preparations that are uniformly oriented (mechanically or magnetically) so that anisotropic NMR parameters, such as dipolar and chemical shift interactions, can be measured to determine structure and orientation of membrane proteins in lipid bilayers. Traditional sample preparations involving mechanically aligned lipids often result in short relaxation times which broaden the (15)N resonances and encumber the manipulation of nuclear spin coherences. The introduction of lipid bicelles as membrane mimicking systems has changed this scenario, and the more favorable relaxation properties of membrane protein (15)N and (13)C resonances make it possible to develop new, more elaborate pulse sequences for higher spectral resolution and sensitivity. Here, we describe our recent progress in the optimization of O-ssNMR pulse sequences. We explain the theory behind these experiments, demonstrate their application to small and medium size proteins, and describe the technical details for setting up these new experiments on the new generation of NMR spectrometers. PMID:24160761

  20. Millimeter and submillimeter wave spectra of 13C-glycolaldehydes

    NASA Astrophysics Data System (ADS)

    Haykal, I.; Motiyenko, R. A.; Margulès, L.; Huet, T. R.

    2013-01-01

    Context. Glycolaldehyde (CH2OHCHO) is the simplest sugar and an important intermediate in the path toward forming more complex biologically relevant molecules. Astronomical surveys of interstellar molecules, such as those available with the very sensitive ALMA telescope, require preliminary laboratory investigations of the microwave and submillimeter-wave spectra of molecular species including new isotopologs - to identify these in the interstellar media. Aims: To achieve the detection of the 13C isotopologs of glycolaldehyde in the interstellar medium, their rotational spectra in the millimeter and submillimeter-wave regions were studied. Methods: The spectra of 13CH2OHCHO and CH2OH13CHO were recorded in the 150-945 GHz spectral range in the laboratory using a solid-state submillimeter-wave spectrometer in Lille. The observed line frequencies were measured with an accuracy of 30 kHz up to 700 GHz and of 50 kHz above 700 GHz. We analyzed the spectra with a standard Watson Hamiltonian. Results: About 10 000 new lines were identified for each isotopolog. The spectroscopic parameters were determined for the ground- and the three lowest vibrational states up to 945 and 630 GHz. Previous microwave assignments of 13CH2OHCHO were not confirmed. Conclusions: The provided line-lists and sets of molecular parameters meet the needs for a first astrophysical search of 13C-glycolaldehydes. Full Tables 3 and 4 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/549/A96

  1. Size dependence of 13C nuclear spin-lattice relaxation in micro- and nanodiamonds.

    PubMed

    Panich, A M; Sergeev, N A; Shames, A I; Osipov, V Yu; Boudou, J-P; Goren, S D

    2015-02-25

    Size dependence of physical properties of nanodiamond particles is of crucial importance for various applications in which defect density and location as well as relaxation processes play a significant role. In this work, the impact of defects induced by milling of micron-sized synthetic diamonds was studied by magnetic resonance techniques as a function of the particle size. EPR and (13)C NMR studies of highly purified commercial synthetic micro- and nanodiamonds were done for various fractions separated by sizes. Noticeable acceleration of (13)C nuclear spin-lattice relaxation with decreasing particle size was found. We showed that this effect is caused by the contribution to relaxation coming from the surface paramagnetic centers induced by sample milling. The developed theory of the spin-lattice relaxation for such a case shows good compliance with the experiment. PMID:25646270

  2. Detection of intracellular lactate with localized diffusion { 1H- 13C}-spectroscopy in rat glioma in vivo

    NASA Astrophysics Data System (ADS)

    Pfeuffer, Josef; Lin, Joseph C.; DelaBarre, Lance; Ugurbil, Kamil; Garwood, Michael

    2005-11-01

    The aim of this study was to compare the diffusion characteristic of lactate and alanine in a brain tumor model to that of normal brain metabolites known to be mainly intracellular such as N-acetylaspartate or creatine. The diffusion of 13C-labeled metabolites was measured in vivo with localized NMR spectroscopy at 9.4 T (400 MHz) using a previously described localization and editing pulse sequence known as ACED-STEAM ('adiabatic carbon editing and decoupling'). 13C-labeled glucose was administered and the apparent diffusion coefficients of the glycolytic products, { 1H- 13C}-lactate and { 1H- 13C}-alanine, were determined in rat intracerebral 9L glioma. To obtain insights into { 1H- 13C}-lactate compartmentation (intra- versus extracellular), the pulse sequence used very large diffusion weighting (50 ms/?m 2). Multi-exponential diffusion attenuation of the lactate metabolite signals was observed. The persistence of a lactate signal at very large diffusion weighting provided direct experimental evidence of significant intracellular lactate concentration. To investigate the spatial distribution of lactate and other metabolites, 1H spectroscopic images were also acquired. Lactate and choline-containing compounds were consistently elevated in tumor tissue, but not in necrotic regions and surrounding normal-appearing brain. Overall, these findings suggest that lactate is mainly associated with tumor tissue and that within the time-frame of these experiments at least some of the glycolytic product ([ 13C] lactate) originates from an intracellular compartment.

  3. In Vivo Detection of 13C Isotopomer Turnover in the Human Brain by Sequential Infusion of 13C Labeled Substrates

    PubMed Central

    Li, Shizhe; Zhang, Yan; Araneta, Maria Ferraris; Xiang, Yun; Johnson, Christopher; Innis, Robert; Shen, Jun

    2012-01-01

    This study demonstrates the feasibility of simultaneously detecting human brain metabolites labeled by two substrates infused in a sequential order. In vivo 13C spectra of carboxylic/amide carbons were acquired only during the infusion of the second substrate. This approach allowed dynamic detection of 13C labeling from two substrates with considerably different labeling patterns. [2-13C]glucose and [U-13C6]glucose were used to generate singlet and doublet signals of the same carboxylic/amide carbon atom, respectively. Because of the large one-bond 13C-13C homonuclear J coupling between a carboxylic/amide carbon and an aliphatic carbon (~50 Hz), the singlet and doublet signals of the same carboxylic/amide carbon were well distinguished. The results demonstrated that different 13C isotopomer patterns could be simultaneously and distinctly measured in vivo in a clinical setting at 3 Tesla. PMID:22578550

  4. Journal of Biomolecular NMR, 14: 7174, 1999. KLUWER/ESCOM

    E-print Network

    Hong, Mei

    ; Accepted 8 February 1999 Key words: colicin Ia, double-quantum filter, isotopic labeling, resonance. Printed in the Netherlands. 71 Selective and extensive 13 C labeling of a membrane protein for solid assignment, solid-state NMR Abstract The selective and extensive 13C labeling of mostly hydrophobicamino acid

  5. Cross-strand coupling and site-specific unfolding thermodynamics of a trpzip beta-hairpin peptide using 13C isotopic labeling and IR spectroscopy.

    PubMed

    Huang, Rong; Wu, Ling; McElheny, Dan; Bour, Petr; Roy, Anjan; Keiderling, Timothy A

    2009-04-23

    Conformational properties of a 12-residue tryptophan zipper (trpzip) beta-hairpin peptide (AWAWENGKWAWK-NH(2), a modification of the original trpzip2 sequence) are analyzed under equilibrium conditions using ECD and IR spectra of a series of variants, singly and doubly C(1)-labeled with (13)C on the amide CO. The characteristic features of the (13)CO component of the amide I' IR band and their sensitivity to the local structure of the peptide are used to differentiate stabilities for parts of the hairpin structure. Doubly labeled peptide spectra indicate that the ends of the beta-strands are frayed and that the center part is more stable as would be expected from formation of a stable hydrophobic core consisting of four tryptophan residues, and supported by MD simulations. NMR analyses were used to determine a best fit solution structure that is in close agreement with that of trpzip2, except for a small variation in the turn geometry. The distinct vibrational coupling patterns of the labeled sites based on this structure are also well matched by ab initio DFT-level calculations of their IR spectral patterns. Thermal unfolding of the peptides as studied with CD spectra could be fit with an apparent two-state transition model. ECD senses only the tryptophan interactions (tertiary-like) and their overall environment, as shown by TD-DFT modeling of the Trp-Trp pi-pi ECD. However, variation of the amide I IR spectra of (13)C-isotopomers showed that the thermal unfolding process is not cooperative in terms of the peptide backbone (secondary structure), since the transition temperatures sensed for labeled modes differ from those for the whole peptide. The thermal data also evidence dependence on concentration and pH but these cause little spectral variation. This study illustrates the consequences of multistate conformational change at the residue- or sequence-specific level in a system whose structure is dominated by hydrophobic collapse. PMID:19326892

  6. X-ray, NMR and DFT studies on benzo[h]thiazolo[2,3-b]quinazoline derivatives

    NASA Astrophysics Data System (ADS)

    Gupta, Richa; Chaudhary, R. P.

    2013-10-01

    4-Phenyl-3,4,5,6-tetrahydrobenzo[h]quinazoline-2(1H)-thione 3, obtained by the condensation of 2-Benzylidene-3,4-dihydronapthalen-1(2H)-one 2 with thiourea, on reaction with chloroacetic acid and 1,2-dibromoethane furnish compounds 4 and 5 and not their possible isomers 7 and 8 respectively. The regiochemistry of the cyclized products and their structure is established by elemental analysis, 1H NMR, 13C NMR, IR and mass spectral data. Density functional theory (DFT) calculations have been carried out for compounds 4, 5 and their isomers 7 and 8 with Jaguar version 6.5112 using B3LYP density functional method and 6-31G?? basis set. X-ray diffraction technique indicates that compound 4 crystallizes in the triclinic space group P-1, with Z = 2 and cell parameters a = 6.3404 (11) Å, b = 9.997 (3) Å, c = 13.560 (2) Å, ? = 107.532(19)°, ? = 94.108(14)°, ? = 97.469(17)°. 1H and 13C NMR of compounds 4, 5, 7 and 8 have been calculated and correlated with experimental results. 2-Arylidene derivatives of 4 were obtained by two routes and their structure was established by spectral data. The lowest energy optimized geometry of the compound 4 in gas phase is consistent with that obtained by X-ray crystallographic studies.

  7. Synthesis Of [2h, 13c]M [2h2m 13c], And [2h3,, 13c] Methyl Aryl Sulfones And Sulfoxides

    DOEpatents

    Martinez, Rodolfo A. (Santa Fe, NM); Alvarez, Marc A. (Santa Fe, NM); Silks, III, Louis A. (Los Alamos, NM); Unkefer, Clifford J. (Los Alamos, NM); Schmidt, Jurgen G. (Los Alamos, NM)

    2004-07-20

    The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfones and [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfoxides, wherein the .sup.13 C methyl group attached to the sulfur of the sulfone or sulfoxide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing methyl aryl sulfones and methyl aryl sulfoxides.

  8. /sup 18/O-isotope effect in /sup 13/C nuclear magnetic resonance spectroscopy. 4. Oxygen exchange of (1-/sup 13/C, /sup 18/O/sub 2/)acetic acid in dilute acid

    SciTech Connect

    Risley, J.M.; Van Etten, R.L.

    1981-07-29

    The /sup 18/O-iosotope shift in /sup 13/C NMR spectroscopy is shown to provide a widely applicable technique for studying the kinetics of oxygen exchange reactions in a nearly continuous assay mode. Here, the technique is used to study the acid-catalyzed medium carboxyl(oxygen)-water exchange reaction of (1-/sup 13/C, /sup 18/O/sub 2/)acetic acid at 32/sup 0/C. The /sup 18/O-isotope-induced shift fo the /sup 13/C NMR signal of the /sup 13/C-enriched carboxyl carbon in acetic acid permits a facile and direct measurement of the relative concentrations of the three (oxygen) isotopic species of acetic acid. The pseudo-first-order rate constant is evaluated as a function of pH and added salt for the salts sodium chloride and sodium perchlorate. The pH profile is typical of those observed for related acid-catalyzed oxygen exchange reactions of the carboxyl group. In the dilute-acid region the rate is approximately first order in hydrogen ion. The present results definitively establish the salt effect on the exchange reaction, resolving a conflict between earlier reports. The rate of the exchange reaction is decreased by increasing concentrations of the two salts. The magnitude of the rate decrease depends on he nature as well as the concentration of the salt. Possible interpretations of the results are discussed.

  9. hNCOcanH pulse sequence and a robust protocol for rapid and unambiguous assignment of backbone ((1)H(N), (15)N and (13)C') resonances in (15)N/(13)C-labeled proteins.

    PubMed

    Kumar, Dinesh; Hosur, Ramakrishna V

    2011-09-01

    A three-dimensional nuclear magnetic resonance (NMR) pulse sequence named as hNCOcanH has been described to aid rapid sequential assignment of backbone resonances in (15)N/(13)C-labeled proteins. The experiment has been derived by a simple modification of the previously described HN(C)N pulse sequence [Panchal et al., J. Biomol. NMR 20 (2001) 135-147]; t2 evolution is used to frequency label (13)C' rather than (15)N (similar trick has also been used in the design of hNCAnH pulse sequence from hNcaNH [Frueh et al., JACS, 131 (2009) 12880-12881]). The modification results in a spectrum equivalent to HNCO, but in addition to inter-residue correlation peaks (i.e. Hi , Ci-1), the spectrum also contains additional intra-residue correlation peaks (i.e. Hi-1 , Ci-1) in the direct proton dimension which has maximum resolution. This is the main strength of the experiment and thus, even a small difference in amide (1) H chemical shifts (5-6 Hz) can be used for establishing a sequential connectivity. This experiment in combination with the HNN experiment described previously [Panchal et al., J. Biomol. NMR 20 (2001) 135-147] leads to a more robust assignment protocol for backbone resonances ((1) H(N) , (15)N) than could be derived from the combination of HNN and HN(C)N experiments [Bhavesh et al., Biochemistry, 40 (2001) 14727-14735]. Further, this new protocol enables assignment of (13)C' resonances as well. We believe that the experiment and the protocol presented here will be of immense value for structural-and functional-proteomics research by NMR. Performance of this experiment has been demonstrated using (13)C/(15)N labeled ubiquitin. PMID:21818779

  10. NMR assignment of the nonstructural protein nsp3(1066-1181) from SARS-CoV.

    PubMed

    Serrano, Pedro; Johnson, Margaret A; Chatterjee, Amarnath; Pedrini, Bill; Wüthrich, Kurt

    2008-12-01

    Sequence-specific NMR assignments of the globular core comprising the residues 1066-1181 within the non-structural protein nsp3e from the SARS coronavirus have been obtained using triple-resonance NMR experiments with the uniformly [(13)C, (15)N]-labeled protein. The backbone and side chain assignments are nearly complete, providing the basis for the ongoing NMR structure determination. A preliminary identification of regular secondary structures has been derived from the (13)C chemical shifts. PMID:19636888

  11. NMR assignment of the nonstructural protein nsp3(1066–1181) from SARS-CoV

    PubMed Central

    Serrano, Pedro; Johnson, Margaret A.; Chatterjee, Amarnath; Pedrini, Bill; Wüthrich, Kurt

    2009-01-01

    Sequence-specific NMR assignments of the globular core comprising the residues 1066–1181 within the non-structural protein nsp3e from the SARS coronavirus have been obtained using triple-resonance NMR experiments with the uniformly [13C,15N]-labeled protein. The backbone and side chain assignments are nearly complete, providing the basis for the ongoing NMR structure determination. A preliminary identification of regular secondary structures has been derived from the 13C chemical shifts. PMID:19636888

  12. In situ 1H NMR study on the trioctylphosphine oxide capping of colloidal InP nanocrystals.

    PubMed

    Hens, Zeger; Moreels, Iwan; Martins, Jose C

    2005-12-01

    We used trioctylphosphine oxide (TOPO) capped colloidal InP nanocrystals (Q-InP|TOPO) to explore the potential of solution 1H NMR spectroscopy in studying in situ the capping and capping exchange of sterically stabilized colloidal nanocrystals. The spectrum of Q-InP|TOPO shows resonances of free TOPO, superimposed on broadened spectral features. The latter were assigned to TOPO adsorbed at Q-InP by means of pulsed field gradient diffusion NMR and 1H-13C HSQC spectroscopy. The diffusion coefficient of Q-InP|TOPO nanocrystals was inferred from the decay of the adsorbed TOPO NMR signal. The corresponding hydrodynamic diameter correlates well with the diameter of Q-InP. By using the resolved methyl resonance of adsorbed TOPO, the packing density of TOPO at the InP surface can be estimated. Spectral hole burning was used to demonstrate explicitly that the adsorbed TOPO resonances are heterogeneously broadened. Exchange of the TOPO capping by pyridine was demonstrated by the disappearance of the resonances for adsorbed TOPO and the appearance of pyridine resonances in the 1H NMR spectrum. These results show that solution NMR spectroscopy should be considered a powerful technique for the in situ study of the capping of sterically stabilized colloidal nanocrystals. PMID:16259026

  13. Synthesis of metal complexes involving Schiff base ligand with methylenedioxy moiety: Spectral, thermal, XRD and antimicrobial studies

    NASA Astrophysics Data System (ADS)

    Sundararajan, M. L.; Jeyakumar, T.; Anandakumaran, J.; Karpanai Selvan, B.

    2014-10-01

    Metal complexes of Zn(II), Cd(II), Ni(II), Cu(II), Fe(III), Co(II), Mn(II) Hg(II), and Ag(I) have been synthesized from Schiff base ligand, prepared by the condensation of 3,4-(methylenedioxy)aniline and 5-bromo salicylaldehyde. All the compounds have been characterized by using elemental analysis, molar conductance, FT-IR, UV-Vis, 1H NMR, 13C NMR, mass spectra, powder XRD and thermal analysis (TG/DTA) technique. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). The FT-IR, 1H NMR, 13C NMR and UV-Vis spectral data suggest that the ligand coordinate to the metal atom by imino nitrogen and phenolic oxygen as bidentate manner. Mass spectral data further support the molecular mass of the compounds and their structure. Powder XRD indicates the crystalline state and morphology of the ligand and its metal complexes. The thermal behaviors of the complexes prove the presence of lattice as well as coordinated water molecules in the complexes. Melting point supports the thermal stability of all the compounds. The in vitro antimicrobial effects of the synthesized compounds were tested against five bacterial and three fungal species by well diffusion method. Antioxidant activities have also been performed for all the compounds. Metal complexes show more biological activity than the Schiff base.

  14. New optical analyzer for 13C-breath test

    NASA Astrophysics Data System (ADS)

    Harde, Hermann; Dressler, Matthias; Helmrich, Günther; Wolff, Marcus; Groninga, Hinrich

    2008-04-01

    Medical breath tests are well established diagnostic tools, predominantly for gastroenterological inspections, but also for many other examinations. Since the composition and concentration of exhaled volatile gases reflect the physical condition of a patient, a breath analysis allows one to recognize an infectious disease in an organ or even to identify a tumor. One of the most prominent breath tests is the 13C-urea-breath test, applied to ascertain the presence of the bacterium helicobacter pylori in the stomach wall as an indication of a gastric ulcer. In this contribution we present a new optical analyzer that is based on photoacoustic spectroscopy and uses a DFB diode laser at 2.744 ?m. The concentration ratio of the CO II isotopologues is determined by measuring the absorption on a 13CO II line in comparison to a 12CO II line. In the specially selected spectral range the lines have similar strengths, although the concentrations differ by a factor of 90. Therefore, the signals are well comparable. Due to an excellent signal-noise-ratio isotope variations of less than 1% can be resolved as required for the breath test.

  15. Quantitative analysis of molecular transport across liposomal bilayer by J-mediated 13C Overhauser dynamic nuclear polarization.

    PubMed

    Cheng, Chi-Yuan; Goor, Olga J G M; Han, Songi

    2012-11-01

    We introduce a new NMR technique to dramatically enhance the solution-state (13)C NMR sensitivity and contrast at 0.35 T and at room temperature by actively transferring the spin polarization from Overhauser dynamic nuclear polarization (ODNP)-enhanced (1)H to (13)C nuclei through scalar (J) coupling, a method that we term J-mediated (13)C ODNP. We demonstrate the capability of this technique by quantifying the permeability of glycine across negatively charged liposomal bilayers composed of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG). The permeability coefficient of glycine across this DPPC/DPPG bilayer is measured to be (1.8 ± 0.1) × 10(-11)m/s, in agreement with the literature value. We further observed that the presence of 20 mol % cholesterol within the DPPC/DPPG lipid membrane significantly retards the permeability of glycine by a factor of 4. These findings demonstrate that the high sensitivity and contrast of J-mediated (13)C ODNP affords the measurement of the permeation kinetics of small hydrophilic molecules across lipid bilayers, a quantity that is difficult to accurately measure with existing techniques. PMID:23072518

  16. Quantitative high resolution 13 C nuclear magnetic resonance of the olefinic and carbonyl carbons of edible vegetable oils

    Microsoft Academic Search

    Kurt F. Wollenberg

    1990-01-01

    The acyl distribution and acyl positional distribution (1,3-acyl and 2-acyl) of triacylglycerols derived from edible vegetable\\u000a oils has been examined by13C nuclear magnetic resonance (NMR) spectroscopy. The acyl profile of three natural oils (corn, peanut, canola) and one specialty\\u000a oil (high oleic sunflower oil, Trisun 80) has been defined from the high resolution (medium field 75.4 MHz) spectrum of the

  17. Methyl fluoride-13C in nematic liquid crystals: Anisotropy of the indirect 13C-19F spin-spin coupling and of the 1H, 13C, and 19F chemical shieldings

    NASA Astrophysics Data System (ADS)

    Jokisaari, J.; Hiltunen, Y.; Lounila, J.

    1986-09-01

    The anisotropy of the indirect 13C-19F spin-spin coupling tensor of methyl fluoride-13C in the liquid crystals ZLI 1167, EBBA, their mixtures, phase IV, and phase 1221 was studied by applying 1H and 19F NMR spectroscopy. The relative anisotropy ?JCF/JCF gets values between -4.3 (in ZLI 1167) and +30.7 (in EBBA) when determined in the conventional way from the experimental dipolar coupling constants taking into account only harmonic vibrational corrections. The inclusion of the deformational corrections in both the direct and indirect C-F coupling tensors leads to a constant, solvent independent relative anisotropy of -2.5±0.2. This result is also obtained when a mixture of the liquid crystals ZLI 1167 and EBBA is used which mixture gives an undistorted geometry for methyl fluoride. The chemical shielding anisotropies ??H, ??C, and ??F for methyl fluoride were determined by applying the method of mixing two thermotropic nematogens (ZLI 1167 and EBBA) with opposite anisotropies of diamagnetic susceptibility. The results ??H =+5.2±0.2 ppm, ??C =+87±4 ppm, and ??F =-90±4 ppm are in fair agreement with theoretical calculations.

  18. NMR diffusion measurements in complex mixtures using constant-time-HSQC-IDOSY and computer-optimized spectral aliasing for high resolution in the carbon dimension.

    PubMed

    Vitorge, Bruno; Jeannerat, Damien; Jeanneat, Damien

    2006-08-01

    A new 3D pulse sequence for NMR diffusion measurements in complex mixtures is presented. It is based on the constant-time (CT) HSQC experiment and combines diffusion delay with the carbon evolution time. This combination has great potential to obtain high resolution in the carbon dimension. When using classical sampling of the carbon dimension, maximal resolution would require a large number of time increments, leading to unrealistically long acquisition times. The application of computer-optimized spectral aliasing allows one to reduce the number of time increments and the total acquisition time by 1-2 orders of magnitude by taking advantage of the information content of 1D carbon spectra, HSQC experiments, or both. With the new CT-HSQC-IDOSY experiment, the diffusion rates of the six anomers present in a 0.1 M D2O solution of glucose, maltose, and maltotriose could be obtained at natural abundance in 8 h with standard deviations below 5%. PMID:16878902

  19. Quantification of wheat straw lignin structure by comprehensive NMR analysis.

    PubMed

    Zeng, Jijiao; Helms, Gregory L; Gao, Xin; Chen, Shulin

    2013-11-20

    A further understanding of the structure of lignin from herbaceous crops is needed for advancing technologies of lignocellulosic biomass processing and utilization. A method was established in this study for analyzing structural motifs found in milled straw lignin (MSL) and cellulase-digested lignin (CEL) isolated from wheat straw by combining quantitative (13)C and HSQC NMR spectral analyses. The results showed that guaiacyl (G) was the predominant unit in wheat straw cell wall lignin over syringyl (S) and hydroxyphenyl (H) units. Up to 8.0 units of tricin were also detected in wheat straw lignin per 100 aromatic rings. Various interunit linkages, including ?-O-4, ?-5, ?-?', ?-1, ?, ?-diaryl ether, and 5-5'/4-O-?' as well as potential lignin-carbohydrate complex (LCC) bonds, were identified and quantified. These findings provide useful information for the development of biofuels and lignin-based materials. PMID:24143908

  20. /sup 18/O-isotope effect in /sup 13/C nuclear magnetic resonance spectroscopy. 3. Additivity effects and steric effects

    SciTech Connect

    Risley, J.M.; Van Etten, R.L.

    1980-10-22

    An upfield shift was previously shown to occur in /sup 13/C NMR spectroscopy upon replacement of /sup 16/O by /sup 18/O. The additivity of this effect is now demonstrated in two types of compounds. The multiple replacement of equivalent oxygen-16 atoms by oxygen-18 atoms results in a shift of the /sup 13/C NMR signal of the oxygen-bearing carbon upfield by an equal amount upon each equivalent substitution. This direct additivity effect is demonstrated by a study of the mixed methyl n-(/sup 18/O)butyl orthocarbonates: the shift of the orthocarbonate carbon is 0.015 ppM//sup 18/O. The individual contributions of the carbonyl oxygen and of the ether oxygen to the total shift of the carboxyl carbon in /sup 18/O-labeled carboxylic esters are measured. The sum of the individual effects equals the shift observed for the totally labeled ester. The additivity observed for the effect of oxygen-18 on /sup 13/C NMR signals is qualitatively similar to effects previously observed for analogous isotope shifts with other nuclei. The possible importance of steric effects in influencing the magnitude of the /sup 18/O shift was explored by synthesizing /sup 18/O-labeled, sterically hindered alcohols and a ketone. It is concluded that electronic substituent effects rather than steric effects are primarily responsible for the large /sup 18/O-isotope shifts on the hydroxyl carbon of tertiary alcohols as compared to typical primary or secondary alcohols.

  1. Proton-Enhanced 13C Nuclear Magnetic Resonance of Lipids and Biomembranes

    PubMed Central

    Urbina, Julio; Waugh, J. S.

    1974-01-01

    A recently developed nuclear double resonance technique which permits sensitive detection, together with high resolution, of rare spins in solids or other dipolar-coupled nuclear systems [Pines, Gibby, and Waugh (1973) J. Chem. Phys. 59, 569] has been applied to the study of natural abundance 13C-nuclear magnetic resonance in lipid mesophases and of selectively labeled carbon sites in bacterial membranes. Detailed microscopic information on the molecular organization and phase transitions of the lipid phases and their interaction with ions and other molecules can be obtained from the study of the chemical shift anisotropies and dynamical aspects of the 13C NMR spectra of unsonicated lipid dispersions (liposomes). Experiments are reported which demonstrated the feasibility of quantitatively observing the 13C-nuclear magnetic resonance of specifically labeled sites in unperturbed Escherichia coli membrane vesicles for the study of the physical state of the lipids with the aim of relating it to the known lipid-dependent functional properties of the membranes. PMID:4531036

  2. Dynamic nuclear polarization of carbonyl and methyl 13C spins in acetate using trityl OX063

    NASA Astrophysics Data System (ADS)

    Niedbalski, Peter; Parish, Christopher; Lumata, Lloyd

    2015-03-01

    Hyperpolarization via dissolution dynamic nuclear polarization (DNP) is a physics technique that amplifies the magnetic resonance signals by several thousand-fold for biomedical NMR spectroscopy and imaging (MRI). Herein we have investigated the effect of carbon-13 isotopic location on the DNP of acetate (one of the biomolecules commonly used for hyperpolarization) at 3.35 T and 1.4 K using a narrow ESR linewidth free radical trityl OX063. We have found that the carbonyl 13C spins yielded about twice the polarization produced in methyl 13C spins. Deuteration of the methyl group, beneficial in the liquid-state, did not produce an improvement in the polarization level at cryogenic conditions. Concurrently, the solid-state nuclear relaxation of these samples correlate with the polarization levels achieved. These results suggest that the location of the 13C isotopic labeling in acetate has a direct impact on the solid-state polarization achieved and is mainly governed by the nuclear relaxation leakage factor.

  3. Distinct fungal and bacterial ?13C signatures can drive the increase in soil ?13C with depth

    NASA Astrophysics Data System (ADS)

    Kohl, Lukas; Laganièrea, Jérôme; Edwards, Kate A.; Billings, Sharon A.; Morrill, Penny L.; Van Biesen, Geert; Ziegler, Susan E.

    2015-04-01

    Soil microbial biomass is a key precursor of soil organic carbon (SOC), and the enrichment in 13C during SOC diagenesis has been purported to be driven by increasing proportions of microbially derived SOC. Yet, little is known about how the ?13C of soil microbial biomass - and by extension the ?13C of microbial inputs to SOC - vary in space, time, or with the composition of the microbial community. Phospholipid fatty acids (PLFA) can be analyzed to measure the variation of the natural abundance ?13C values of both individual groups of microorganisms and the microbial community as a whole. Here, we show how variations of ?13CPLFA within the soil profile provides insight into C fluxes in undisturbed soils and demonstrate that distinct ?13C of fungal and bacterial biomass and their relative abundance can drive the increase of bulk ?13CSOC with depth. We studied the variation in natural abundance ?13C signatures of PLFA in podzolic soil profiles from mesic boreal forests in Atlantic Canada. Samples from the organic horizons (L,F,H) and the mineral (B; top 10 cm) horizons were analyzed for ?13C values of PLFA specific to fungi, G+ bacteria, or G- bacteria as proxies for the ?13C of the biomass of these groups, and for ?13C values of PLFA produced by a wide range of microorganisms (e.g. 16:0) as a proxy for the ?13C value of microbial biomass as a whole. Results were compared to fungi:bacteria ratios (F:B) and bulk ?13CSOC values. The ?13C values of group-specific PLFA were driven by differences among source organisms, with fungal PLFA consistently depleted (2.1 to 6.4‰) relative to and G+ and G- bacterial PLFA in the same sample. All group-specific PLFA, however, exhibited nearly constant ?13C values throughout the soil profile, apparently unaffected by the over 2.8‰ increase in ?13CSOC with depth from the L to B horizons. This indicates that bulk SOC poorly represents the substrates actually consumed by soil microorganisms in situ. Instead, our results suggest that soil microorganisms primarily consume substrates that exhibit constant ?13C values throughout the soil profile, like root litter or dissolved organic carbon from litter leachates or root exudates that percolates through the soil column. ?13C values of PLFA produced by both fungi and bacteria, in contrast to the group specific PLFA, strongly increased with depth and were tightly correlated to F:B ratios (R2 > 0.84), which decreased with depth. Because group-specific PLFA did not exhibit increased ?13C with depth, the increase observed in the general biomarker ?13C values, associated with the aggregated microbial community, was not the consequence of microbial incorporation of more 13C enriched SOC at greater depth. Rather, the increase in community ?13C reflects a shift in community structure towards more 13C enriched bacteria with depth. Our results indicate that, higher ?13C values associated with microbial biomass at a greater depth likely contributes to the increase in ?13CSOC with depth via more 13C enriched contributions from necromass to SOC.

  4. Sodium ion effect on silk fibroin conformation characterized by solid-state NMR and generalized 2D NMR–NMR correlation

    Microsoft Academic Search

    Qing-Xia Ruan; Ping Zhou

    2008-01-01

    In the present work, we investigated Na+ ion effect on the silk fibroin (SF) conformation. Samples are Na+-involved regenerated silk fibroin films. 13C CP-MAS NMR demonstrates that as added [Na+] increases, partial silk fibroin conformation transit from helix-form to ?-form at certain Na+ ion concentration which is much higher than that in Bombyx mori silkworm gland. The generalized two-dimensional NMR–NMR

  5. Brute-Force Hyperpolarization for NMR and MRI.

    PubMed

    Hirsch, Matthew L; Kalechofsky, Neal; Belzer, Avrum; Rosay, Melanie; Kempf, James G

    2015-07-01

    Hyperpolarization (HP) of nuclear spins is critical for ultrasensitive nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). We demonstrate an approach for >1500-fold enhancement of key small-molecule metabolites: 1-(13)C-pyruvic acid, 1-(13)C-sodium lactate, and 1-(13)C-acetic acid. The (13)C solution NMR signal of pyruvic acid was enhanced 1600-fold at B = 1 T and 40 °C by pre-polarizing at 14 T and ?2.3 K. This "brute-force" approach uses only field and temperature to generate HP. The noted 1 T observation field is appropriate for benchtop NMR and near the typical 1.5 T of MRI, whereas high-field observation scales enhancement as 1/B. Our brute-force process ejects the frozen, solid sample from the low-T, high-B polarizer, passing it through low field (B < 100 G) to facilitate "thermal mixing". That equilibrates (1)H and (13)C in hundreds of milliseconds, providing (13)C HP from (1)H Boltzmann polarization attained at high B/T. The ejected sample arrives at a room-temperature, permanent magnet array, where rapid dissolution with 40 °C water yields HP solute. Transfer to a 1 T NMR system yields (13)C signals with enhancements at 80% of ideal for noted polarizing conditions. High-resolution NMR of the same product at 9.4 T had consistent enhancement plus resolution of (13)C shifts and J-couplings for pyruvic acid and its hydrate. Comparable HP was achieved with frozen aqueous lactate, plus notable enhancement of acetic acid, demonstrating broader applicability for small-molecule NMR and metabolic MRI. Brute-force avoids co-solvated free-radicals and microwaves that are essential to competing methods. Here, unadulterated samples obviate concerns about downstream purity and also exhibit slow solid-state spin relaxation, favorable for transporting HP samples. PMID:26098752

  6. Windowed Stochastic Proton Decoupling for in Vivo 13C Magnetic Resonance Spectroscopy with Reduced RF Power Deposition

    PubMed Central

    Xiang, Yun; Shen, Jun

    2011-01-01

    Purpose To propose a strategy for reducing RF power deposition by stochastic proton decoupling based on Rayleigh’s theorem. Materials and Methods Rayleigh’s theorem was used to remove frequency components of stochastic decoupling over the 3.90–6.83 ppm range. [2-13C] or [2,5-13C2]glucose was infused intravenously to anesthetized rats. 13C labeling of brain metabolites was detected in the carboxylic/amide spectral region at 11.7 Tesla using either the original stochastic decoupling method developed by Ernst or the proposed windowed stochastic decoupling method. Results By restricting frequency components of stochastic decoupling to 1.91–3.90 ppm and 6.83–7.60 ppm spectral regions decoupling power deposition was reduced by ~50%. The proposed windowed stochastic decoupling scheme is experimentally demonstrated for in vivo 13C MRS of rat brain at 11.7 Tesla. Conclusion The large reduction in decoupling power deposition makes it feasible to perform stochastic proton decoupling at very high magnetic fields for human brain 13C MRS studies. PMID:21769967

  7. 1H, 13C and 15N nuclear magnetic resonance studies of polyamidines prepared from di(4,4?-aminophenyl) methane and different triethyl orthoesters—polymers with a prototropic tautomerism

    Microsoft Academic Search

    H. Komber; C. Klinger; F. Böhme

    1997-01-01

    N1,N2-disubstituted polyform-, -acet- and -benzamidines containing the 4,4?-substituted diphenyl methane unit were studied by means of 1H, 13C and 15N nuclear magnetic resonance (n.m.r.) in solution. The n.m.r. signals were assigned. For the polyacet- and -benzamidine slow tautomerism on the n.m.r. time scale resulted in separate signals for the amino and imino moiety due to preference for the E-anti configuration

  8. Moving NMR

    Microsoft Academic Search

    Bernhard Blümich; Federico Casanova; Ernesto Danieli; Qingxia Gong; Marcus Greferath; Agnes Haber; Jürgen Kolz; Juan Perlo

    2008-01-01

    Initiated by the use of NMR for well logging, portable NMR instruments are being developed for a variety of novel applications in materials testing and process analysis and control. Open sensors enable non-destructive testing of large objects, and small, cup-size magnets become available for high throughput analysis by NMR relaxation and spectroscopy. Some recent developments of mobile NMR are reviewed

  9. Discrimination between 12 C and 13 C by marine plants

    Microsoft Academic Search

    S. C. Maberly; J. A. Raven; A. M. Johnston

    1992-01-01

    Summary  The natural abundance13C\\/12C ratios (as ?13C) of organic matter of marine macroalgae from Fife and Angus (East Scotland) were measured for comparison with the species'\\u000a ability to use CO2 and HCO\\u000a 3\\u000a -\\u000a for photosynthesis, as deduced from previously published pH-drift measurements. There was a clear difference in ?13C values for species able or unable to use HCO\\u000a 3\\u000a -

  10. Biosynthesis of hibarimicins. I. 13C-labeling experiments.

    PubMed

    Hori, Hiroshi; Kajiura, Takayuki; Igarashi, Yasuhiro; Furumai, Tamotsu; Higashi, Kazuaki; Ishiyama, Tadayuki; Uramoto, Masakazu; Uehara, Yoshimasa; Oki, Toshikazu

    2002-01-01

    Biosynthesis of hibarimicin was studied based on the feeding experiments with 13C labeled acetates. All carbons in the aglycon, except for the methoxy carbons, were derived from acetate. The carbon framework of the aglycon was proved to be constructed by dimerization of an intermediate which was biosynthesized via the decarboxylation and skeltal rearrangement starting from an undecaketide. The rearrangement was confirmed by detecting the long range (three-bond) coupling between two carbons in the difference spectra of selective 13C decoupled INADEQUATE of hibarimicin B labeled with sodium [1,2-13C2] acetate. PMID:11918065

  11. Constraining 3-PG with a new ?13C submodel: a test using the ?13C of tree rings.

    PubMed

    Wei, Liang; Marshall, John D; Link, Timothy E; Kavanagh, Kathleen L; DU, Enhao; Pangle, Robert E; Gag, Peter J; Ubierna, Nerea

    2014-01-01

    A semi-mechanistic forest growth model, 3-PG (Physiological Principles Predicting Growth), was extended to calculate ?(13)C in tree rings. The ?(13)C estimates were based on the model's existing description of carbon assimilation and canopy conductance. The model was tested in two ~80-year-old natural stands of Abies grandis (grand fir) in northern Idaho. We used as many independent measurements as possible to parameterize the model. Measured parameters included quantum yield, specific leaf area, soil water content and litterfall rate. Predictions were compared with measurements of transpiration by sap flux, stem biomass, tree diameter growth, leaf area index and ?(13)C. Sensitivity analysis showed that the model's predictions of ?(13)C were sensitive to key parameters controlling carbon assimilation and canopy conductance, which would have allowed it to fail had the model been parameterized or programmed incorrectly. Instead, the simulated ?(13)C of tree rings was no different from measurements (P > 0.05). The ?(13)C submodel provides a convenient means of constraining parameter space and avoiding model artefacts. This ?(13)C test may be applied to any forest growth model that includes realistic simulations of carbon assimilation and transpiration. PMID:23663114

  12. Structural analysis of a banana-liquid crystal in the B4 phase by solid-state NMR.

    PubMed

    Yamada, Kazuhiko; Kang, Sungmin; Takimoto, Koji; Hattori, Masaya; Shirata, Kei; Kawauchi, Susumu; Deguchi, Kenzo; Shimizu, Tadashi; Watanabe, Junji

    2013-06-01

    In this paper, we present a structural investigation of 1,3-phenylene bis[4-((4-10-decyloxyphenyl)iminomethyl)-benzoate], known as a banana-liquid crystal, in the B4 phase, which was performed by solid-state nuclear magnetic resonance (NMR) methodology combined with quantum chemical calculations. The present solid-state NMR measurements including (13)C CPMAS, 2D TOSS-deTOSS, dipole-dephase, 1D and 2D EXSY, and MAS-j-HMQC provided accurate spectral assignments and unambiguous NMR parameters such as (13)C chemical shift tensors, which were used for construction of the three-dimensional structure with the aid of density functional theory calculations. In the obtained molecular structure, two arms of the bent-core molecule are asymmetrically expanded such that the direction of the dipole moment is off alignment with respect to the middle line of the center benzene ring. It is this antisymmetric structure that is the origin of the twisted helical system in the B4 phase. PMID:23654351

  13. Anomalous 13C enrichment in modern marine organic carbon

    USGS Publications Warehouse

    Arthur, M.A.; Dean, W.E.; Claypool, G.E.

    1985-01-01

    Marine organic carbon is heavier isotopically (13C enriched) than most land-plant or terrestrial organic C1. Accordingly, ??13C values of organic C in modern marine sediments are routinely interpreted in terms of the relative proportions of marine and terrestrial sources of the preserved organic matter2,3. When independent geochemical techniques are used to evaluate the source of organic matter in Cretaceous or older rocks, those rocks containing mostly marine organic C are found typically to have lighter (more-negative) ??13C values than rocks containing mostly terrestrial organic C. Here we conclude that marine photosynthesis in mid-Cretaceous and earlier oceans generally resulted in a greater fractionation of C isotopes and produced organic C having lighter ??13C values. Modern marine photosynthesis may be occurring under unusual geological conditions (higher oceanic primary production rates, lower PCO2) that limit dissolved CO2 availability and minimize carbon isotope fractionation4. ?? 1985 Nature Publishing Group.

  14. NBO, HOMO-LUMO, UV, NLO, NMR and vibrational analysis of veratrole using FT-IR, FT-Raman, FT-NMR spectra and HF-DFT computational methods.

    PubMed

    Suvitha, A; Periandy, S; Gayathri, P

    2015-03-01

    This work deals with FT-IR, FT-Raman and FT-NMR spectral analysis and NBO, NLO, HOMO-LUMO and electronic transitions studies on veratrole. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands were interpreted with the aid of structure optimizations and geometrical parameter calculations based on Hartree-Fock (HF) and density functional theory (DFT) method with 6-311++G(d, p) basis set. A study on the electronic properties, such as HOMO and LUMO energies were performed by time independent DFT approach. In addition, molecular electrostatic potential (MEP), Natural Bond-Orbital (NBO) analysis and thermodynamic properties were performed. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by gauge independent atomic orbital (GIAO) method and compared with experimental chemical shift. PMID:25514662

  15. NBO, HOMO-LUMO, UV, NLO, NMR and vibrational analysis of veratrole using FT-IR, FT-Raman, FT-NMR spectra and HF-DFT computational methods

    NASA Astrophysics Data System (ADS)

    Suvitha, A.; Periandy, S.; Gayathri, P.

    2015-03-01

    This work deals with FT-IR, FT-Raman and FT-NMR spectral analysis and NBO, NLO, HOMO-LUMO and electronic transitions studies on veratrole. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands were interpreted with the aid of structure optimizations and geometrical parameter calculations based on Hartree-Fock (HF) and density functional theory (DFT) method with 6-311++G(d, p) basis set. A study on the electronic properties, such as HOMO and LUMO energies were performed by time independent DFT approach. In addition, molecular electrostatic potential (MEP), Natural Bond-Orbital (NBO) analysis and thermodynamic properties were performed. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by gauge independent atomic orbital (GIAO) method and compared with experimental chemical shift.

  16. The distribution of 13C in the Atlantic Ocean

    Microsoft Academic Search

    P. Kroopnick

    1980-01-01

    Individual vertical profiles and north-south sections for the distribution of the delta13C of total dissolved inorganic carbon are presented for the Atlantic stations of the GEOSECS program. In most cases the delta13C data parallel the distribution of dissolved O2. Differences are attributed to in-situ oxidation of organic matter and dissolution of particles of CaCO3. Antarctic Bottom and Intermediate Waters have

  17. Tripodal tris(hydroxypyridinone) ligands for immunoconjugate PET imaging with 89Zr4+: comparison with desferrioxamine-B† †Electronic supplementary information (ESI) available: 1H and 13C NMR data, reverse phase HPLC and size exclusion HPLC chromatograms, phosphoimages of ITLC plates, ex vivo biodistribution data. See DOI: 10.1039/c4dt02978j Click here for additional data file.

    PubMed Central

    Meszaros, Levente K.; Paterson, Brett M.; Berry, David J.; Cooper, Maggie S.; Ma, Yongmin; Hider, Robert C.; Blower, Philip J.

    2015-01-01

    Due to its long half-life (78 h) and decay properties (77% electron capture, 23% ?+, E max = 897 keV, E av = 397 keV, E? = 909 keV, I? = 100%) 89Zr is an appealing radionuclide for immunoPET imaging with whole IgG antibodies. Derivatives of the siderophore desferrioxamine-B (H3DFO) are the most widely used bifunctional chelators for coordination of 89Zr4+ because the radiolabeling of the resulting immunoconjugates is rapid under mild conditions. 89Zr-DFO complexes are reportedly stable in vitro but there is evidence that 89Zr4+ is released in vivo, and subsequently taken up by the skeleton. We have evaluated a novel tripodal tris(hydroxypyridinone) chelator, H3CP256 and its bifunctional maleimide derivative, H3YM103, for coordination of Zr4+ and compared the NMR spectra, and the 89Zr4+ radiolabeling, antibody conjugation, serum stability and in vivo distribution of radiolabelled immunoconjugates with those of H3DFO and its analogues. H3CP256 coordinates 89Zr4+ at carrier-free concentrations forming [89Zr(CP256)]+. Both H3DFO and H3CP256 were efficiently radiolabelled using [89Zr(C2O4)4]4– at ambient temperature in quantitative yield at pH 6–7 at millimolar concentrations of chelator. Competition experiments demonstrate that 89Zr4+ dissociates from [89Zr(DFO)]+ in the presence of one equivalent of H3CP256 (relative to H3DFO) at pH 6–7, resulting largely in [89Zr(CP256)]+. To assess the stability of H3DFO and H3YM103 immunoconjugates radiolabelled with 89Zr, maleimide derivatives of the chelators were conjugated to the monoclonal antibody trastuzumab via reduced cysteine side chains. Both immunoconjugates were labelled with 89Zr4+ in >98% yield at high specific activities and the labeled immunoconjugates were stable in serum with respect to dissociation of the radiometal. In vivo studies in mice indicate that 89Zr4+ dissociates from YM103-trastuzumab with significant amounts of activity becoming associated with bones and joints (25.88 ± 0.58% ID g–1 7 days post-injection). In contrast, <8% ID g–1 of 89Zr activity becomes associated with bone in animals administered 89Zr-DFO-trastuzumab over the course of 7 days. The tris(hydroxypyridinone) chelator, H3CP256, coordinates 89Zr4+ rapidly under mild conditions, but the 89Zr-labelled immunoconjugate, 89Zr-YM103-trastuzumab was observed to release appreciable amounts of 89Zr4+ in vivo, demonstrating inferior stability when compared with 89Zr-DFO-trastuzumab. The significantly lower in vivo stability is likely to be a result of lower kinetic stability of the Zr4+ tris(hydroxypyridinone complex) relative to that of DFO and its derivatives. PMID:25351250

  18. Catabolism of glucose and lactose in Bifidobacterium animalis subsp. lactis, studied by 13C Nuclear Magnetic Resonance.

    PubMed

    González-Rodríguez, Irene; Gaspar, Paula; Sánchez, Borja; Gueimonde, Miguel; Margolles, Abelardo; Neves, Ana Rute

    2013-12-01

    Bifidobacteria are widely used as probiotics in several commercial products; however, to date there is little knowledge about their carbohydrate metabolic pathways. In this work, we studied the metabolism of glucose and lactose in the widely used probiotic strain Bifidobacterium animalis subsp. lactis BB-12 by in vivo (13)C nuclear magnetic resonance (NMR) spectroscopy. The metabolism of [1-(13)C]glucose was characterized in cells grown in glucose as the sole carbon source. Moreover, the metabolism of lactose specifically labeled with (13)C on carbon 1 of the glucose or the galactose moiety was determined in suspensions of cells grown in lactose. These experiments allowed the quantification of some intermediate and end products of the metabolic pathways, as well as determination of the consumption rate of carbon sources. Additionally, the labeling patterns in metabolites derived from the metabolism of glucose specifically labeled with (13)C on carbon 1, 2, or 3 in cells grown in glucose or lactose specifically labeled in carbon 1 of the glucose moiety ([1-(13)Cglucose]lactose), lactose specifically labeled in carbon 1 of the galactose moiety ([1-(13)Cgalactose]lactose), and [1-(13)C]glucose in lactose-grown cells were determined in cell extracts by (13)C NMR. The NMR analysis showed that the recovery of carbon was fully compatible with the fructose 6-phosphate, or bifid, shunt. The activity of lactate dehydrogenase, acetate kinase, fructose 6-phosphate phosphoketolase, and pyruvate formate lyase differed significantly between glucose and lactose cultures. The transcriptional analysis of several putative glucose and lactose transporters showed a significant induction of Balat_0475 in the presence of lactose, suggesting a role for this protein as a lactose permease. This report provides the first in vivo experimental evidence of the metabolic flux distribution in the catabolic pathway of glucose and lactose in bifidobacteria and shows that the bifid shunt is the only pathway involved in energy recruitment from these two sugars. On the basis of our experimental results, a model of sugar metabolism in B. animalis subsp. lactis is proposed. PMID:24077711

  19. Detection of poly(ethylene glycol) residues from nonionic surfactants in surface water by sup 1 H and sup 13 C nuclear magnetic resonance spectrometry

    SciTech Connect

    Leenheer, J.A.; Wershaw, R.L.; Brown, P.A.; Noyes, T.I. (Geological Survey, Denver, CO (USA))

    1991-01-01

    Poly(ethylene glycol) (PEG) residues were detected in organic solute isolates from surface water by {sup 1}H nuclear magnetic resonance spectrometry (NMR), {sup 13}C NMR spectrometry, and colorimetric assay. PEG residues were separated from natural organic solutes in Clear Creek, CO, by a combination of methylation and chromatographic procedures. The isolated PEG residues, characterized by NMR spectrometry, were found to consist of neutral and acidic residues that also contained poly(propylene glycol) moieties. The {sup 1}H NMR and the colorimetric assays for poly(ethylene glycol) residues were done on samples collected in the lower Mississippi River and tributaries between S. Louis, MO, and New Orleans, LA, in July-August and November-December 1987. Aqueous concentrations for poly(ethylene glycol) residues based on colorimetric assay ranged from undetectable to {approximately}28 {mu}g/L. Concentrations based on {sup 1}H NMR spectrometry ranged from undetectable to 145 {mu}g/L.

  20. Detection of poly(ethylene glycol) residues from nonionic surfactants in surface water by1h and13c nuclear magnetic resonance spectrometry

    USGS Publications Warehouse

    Leenheer, J.A.; Wershaw, R.L.; Brown, P.A.; Noyes, T.I.

    1991-01-01

    ??? Poly(ethylene glycol) (PEG) residues were detected in organic solute isolates from surface water by 1H nuclear magnetic resonance spectrometry (NMR), 13C NMR spectrometry, and colorimetric assay. PEG residues were separated from natural organic solutes in Clear Creek, CO, by a combination of methylation and chromatographic procedures. The isolated PEG residues, characterized by NMR spectrometry, were found to consist of neutral and acidic residues that also contained poly(propylene glycol) moieties. The 1H NMR and the colorimetric assays for poly(ethylene glycol) residues were done on samples collected in the lower Mississippi River and tributaries between St. Louis, MO, and New Orleans, LA, in July-August and November-December 1987. Aqueous concentrations for poly(ethylene glycol) residues based on colorimetric assay ranged from undetectable to ???28 ??g/L. Concentrations based on 1H NMR spectrometry ranged from undetectable to 145 ??g/L.

  1. An analytic and systematic framework for estimating metabolic flux ratios from 13C tracer experiments

    PubMed Central

    Rantanen, Ari; Rousu, Juho; Jouhten, Paula; Zamboni, Nicola; Maaheimo, Hannu; Ukkonen, Esko

    2008-01-01

    Background Metabolic fluxes provide invaluable insight on the integrated response of a cell to environmental stimuli or genetic modifications. Current computational methods for estimating the metabolic fluxes from 13C isotopomer measurement data rely either on manual derivation of analytic equations constraining the fluxes or on the numerical solution of a highly nonlinear system of isotopomer balance equations. In the first approach, analytic equations have to be tediously derived for each organism, substrate or labelling pattern, while in the second approach, the global nature of an optimum solution is difficult to prove and comprehensive measurements of external fluxes to augment the 13C isotopomer data are typically needed. Results We present a novel analytic framework for estimating metabolic flux ratios in the cell from 13C isotopomer measurement data. In the presented framework, equation systems constraining the fluxes are derived automatically from the model of the metabolism of an organism. The framework is designed to be applicable with all metabolic network topologies, 13C isotopomer measurement techniques, substrates and substrate labelling patterns. By analyzing nuclear magnetic resonance (NMR) and mass spectrometry (MS) measurement data obtained from the experiments on glucose with the model micro-organisms Bacillus subtilis and Saccharomyces cerevisiae we show that our framework is able to automatically produce the flux ratios discovered so far by the domain experts with tedious manual analysis. Furthermore, we show by in silico calculability analysis that our framework can rapidly produce flux ratio equations – as well as predict when the flux ratios are unobtainable by linear means – also for substrates not related to glucose. Conclusion The core of 13C metabolic flux analysis framework introduced in this article constitutes of flow and independence analysis of metabolic fragments and techniques for manipulating isotopomer measurements with vector space techniques. These methods facilitate efficient, analytic computation of the ratios between the fluxes of pathways that converge to a common junction metabolite. The framework can been seen as a generalization and formalization of existing tradition for computing metabolic flux ratios where equations constraining flux ratios are manually derived, usually without explicitly showing the formal proofs of the validity of the equations. PMID:18534038

  2. In situ detection of changes in soil bacterial and fungal activities by measuring 13C incorporation into soil phospholipid fatty acids from 13C acetate

    Microsoft Academic Search

    Tomohito Arao

    1999-01-01

    Phospholipids in four types of soil incubated with 1-13C acetate for 24 h had much higher 13C contents than neutral lipids or glycolipids. 13C was mainly incorporated into 18:2?6, 16:0 and 18:1?9 phospholipids in a Low Humic Andosol and a Gray Lowland Soil. When soil was incubated with 1-13C acetate and cycloheximide, the incorporation of 13C into 18:2?6 could not

  3. Multinuclear and magic-angle spinning NMR investigations of molecular organization in phospholipid-triglyceride aqueous dispersions.

    PubMed

    Li, K L; Tihal, C A; Guo, M; Stark, R E

    1993-09-28

    The supramolecular organization of multi-bilayers formed by aqueous egg phosphatidylcholine-triolein (PC-TO) mixtures has been investigated using 31P, 13C, and 1H nuclear magnetic resonance (NMR). For these emulsions, which mimic substrates in the early hydrolytic stages of fat digestion, the NMR spectra obtained with magic-angle spinning (MAS) exhibit resolution comparable to that of sonicated vesicles and integrated peak intensities consistent with their chemical composition. Both 31P line shapes and MAS sideband patterns from the phosphocholine group indicate that mixing with triolein produces a PC bilayer which remains predominantly liquid crystalline in its organization; nevertheless, anomalous spectral features in MAS spectra may be attributed to additional phases in which the headgroups adopt a different orientation with respect to the bilayer normal, and tight packing enhances phosphorus-phosphorus interactions. 13C and 1H line widths monitored as a function of PC mole fraction, spinning speed, and decoupling strength show that the choline headgroups and glycerol backbones are anchored preferentially in the phospholipid-triglyceride assemblies, whereas all acyl chains become very fluid. The average degree of chain order also decreases for the mixed dispersions, as judged from spinning-sideband intensities in 1H MAS NMR spectra. The absence of proton spin-diffusion effects in the PC-TO multilayers is demonstrated by examination of their spinning sidebands and relaxation times, making it possible to use MAS-assisted two-dimensional NMR to assign overlapped 1H resonances and to identify proximal interactions between the two constituents. The usefulness of these NMR strategies in mechanistic studies of gastric fat digestion is also discussed. PMID:8399162

  4. Isolation and characterization of a novel rebaudioside M isomer from a bioconversion reaction of rebaudioside A and NMR comparison studies of rebaudioside M isolated from Stevia rebaudiana Bertoni and Stevia rebaudiana Morita.

    PubMed

    Prakash, Indra; Bunders, Cynthia; Devkota, Krishna P; Charan, Romila D; Ramirez, Catherine; Priedemann, Christopher; Markosyan, Avetik

    2014-01-01

    A minor product, rebaudioside M2 (2), from the bioconversion reaction of rebaudioside A (4) to rebaudioside D (3), was isolated and the complete structure of the novel steviol glycoside was determined. Rebaudioside M2 (2) is considered an isomer of rebaudioside M (1) and contains a relatively rare 1?6 sugar linkage. It was isolated and characterized with NMR (1H, 13C, COSY, HSQC-DEPT, HMBC, 1D-TOCSY, and NOESY) and mass spectral data. Additionally, we emphasize the importance of 1D and 2D NMR techniques when identifying complex steviol glycosides. Numerous NMR spectroscopy studies of rebaudioside M (1), rebaudioside D (3), and mixture of 1 and 3 led to the discovery that SG17 which was previously reported in literature, is a mixture of rebaudioside D (3), rebaudioside M (1), and possibly other related steviol glycosides. PMID:24970220

  5. Isolation and Characterization of a Novel Rebaudioside M Isomer from a Bioconversion Reaction of Rebaudioside A and NMR Comparison Studies of Rebaudioside M Isolated from Stevia rebaudiana Bertoni and Stevia rebaudiana Morita

    PubMed Central

    Prakash, Indra; Bunders, Cynthia; Devkota, Krishna P.; Charan, Romila D.; Ramirez, Catherine; Priedemann, Christopher; Markosyan, Avetik

    2014-01-01

    A minor product, rebaudioside M2 (2), from the bioconversion reaction of rebaudioside A (4) to rebaudioside D (3), was isolated and the complete structure of the novel steviol glycoside was determined. Rebaudioside M2 (2) is considered an isomer of rebaudioside M (1) and contains a relatively rare 1?6 sugar linkage. It was isolated and characterized with NMR (1H, 13C, COSY, HSQC-DEPT, HMBC, 1D-TOCSY, and NOESY) and mass spectral data. Additionally, we emphasize the importance of 1D and 2D NMR techniques when identifying complex steviol glycosides. Numerous NMR spectroscopy studies of rebaudioside M (1), rebaudioside D (3), and mixture of 1 and 3 led to the discovery that SG17 which was previously reported in literature, is a mixture of rebaudioside D (3), rebaudioside M (1), and possibly other related steviol glycosides. PMID:24970220

  6. NMR investigations of gas transport in fluidized beds

    Microsoft Academic Search

    R. Wang; J. Ng; M. Rosen; R. Mair; R. Walsworth; D. Candela

    2004-01-01

    We are using NMR of hyperpolarized xenon to study gas transport in fluidized beds. Our preliminary investigations have shown that both the xenon NMR frequency and linewidth are dependent on the bulk gas flow rate through the bed; and that a distinct xenon NMR frequency spectral peak can be observed in the bubbling regime. These changes of the xenon NMR

  7. Ultrahigh resolution protein structures using NMR chemical shift tensors

    PubMed Central

    Wylie, Benjamin J.; Sperling, Lindsay J.; Nieuwkoop, Andrew J.; Franks, W. Trent; Oldfield, Eric; Rienstra, Chad M.

    2011-01-01

    NMR chemical shift tensors (CSTs) in proteins, as well as their orientations, represent an important new restraint class for protein structure refinement and determination. Here, we present the first determination of both CST magnitudes and orientations for 13C? and 15N (peptide backbone) groups in a protein, the ?1 IgG binding domain of protein G from Streptococcus spp., GB1. Site-specific 13C? and 15N CSTs were measured using synchronously evolved recoupling experiments in which 13C and 15N tensors were projected onto the 1H-13C and 1H-15N vectors, respectively, and onto the 15N-13C vector in the case of 13C?. The orientations of the 13C? CSTs to the 1H-13C and 13C-15N vectors agreed well with the results of ab initio calculations, with an rmsd of approximately 8°. In addition, the measured 15N tensors exhibited larger reduced anisotropies in ?-helical versus ?-sheet regions, with very limited variation (18 ± 4°) in the orientation of the z-axis of the 15N CST with respect to the 1H-15N vector. Incorporation of the 13C? CST restraints into structure calculations, in combination with isotropic chemical shifts, transferred echo double resonance 13C-15N distances and vector angle restraints, improved the backbone rmsd to 0.16 ? (PDB ID code 2LGI) and is consistent with existing X-ray structures (0.51 ? agreement with PDB ID code 2QMT). These results demonstrate that chemical shift tensors have considerable utility in protein structure refinement, with the best structures comparable to 1.0-? crystal structures, based upon empirical metrics such as Ramachandran geometries and ?1/?2 distributions, providing solid-state NMR with a powerful tool for de novo structure determination. PMID:21969532

  8. Simulation of 13C nuclear magnetic resonance spectra for isodon terpenoid

    NASA Astrophysics Data System (ADS)

    Yang, Guochen; Tong, Jianbo; Liu, Shuling

    2008-11-01

    A quantitative structure spectroscopy relationship (QSSR) model of 13C nuclear magnetic resonance (NMR) of 7000 carbon atoms in 350 isodon terpenoid compounds has been developed using atomic electronegativity distance vector (AEDV) and atomic hybridization state index (AHSI). The prediction correlation coefficient ( R) value of the QSSR model based on multiple linear regression analysis was 0.9542. The stability and prediction capacity of the QSSR model have been tested using the leave-one-out cross-validation and test sets methodology. The correlation coefficients R obtained were 0.9540 and 0.9556, respectively, which showed that the predictive potential of the proposed models has good modeling stability and prediction ability.

  9. Demonstration of the ethylmalonyl-CoA pathway by using 13C metabolomics

    PubMed Central

    Peyraud, Rémi; Kiefer, Patrick; Christen, Philipp; Massou, Stephane; Portais, Jean-Charles; Vorholt, Julia A.

    2009-01-01

    The assimilation of one-carbon (C1) compounds, such as methanol, by serine cycle methylotrophs requires the continuous regeneration of glyoxylate. Instead of the glyoxylate cycle, this process is achieved by a not yet established pathway where CoA thioesters are known to play a key role. We applied state-of-the-art metabolomics and 13C metabolomics strategies to demonstrate how glyoxylate is generated during methylotrophic growth in the isocitrate lyase-negative methylotroph Methylobacterium extorquens AM1. High-resolution mass spectrometry showed the presence of CoA thioesters specific to the recently proposed ethylmalonyl-CoA pathway. The operation of this pathway was demonstrated by short-term 13C-labeling experiments, which allowed determination of the sequence of reactions from the order of label incorporation into the different CoA derivatives. Analysis of 13C positional enrichment in glycine by NMR was consistent with the predicted labeling pattern as a result of the operation of the ethylmalonyl-CoA pathway and the unique operation of the latter for glyoxylate generation during growth on methanol. The results also revealed that 2 molecules of glyoxylate were regenerated in this process. This work provides a complete pathway for methanol assimilation in the model methylotroph M. extorquens AM1 and represents an important step toward the determination of the overall topology of its metabolic network. The operation of the ethylmalonyl-CoA pathway in M. extorquens AM1 has major implications for the physiology of these methylotrophs and their role in nature, and it also provides a common ground for C1 and C2 compound assimilation in isocitrate lyase-negative bacteria. PMID:19261854

  10. Affordable uniform isotope labeling with (2)H, (13)C and (15)N in insect cells.

    PubMed

    Sitarska, Agnieszka; Skora, Lukasz; Klopp, Julia; Roest, Susan; Fernández, César; Shrestha, Binesh; Gossert, Alvar D

    2015-06-01

    For a wide range of proteins of high interest, the major obstacle for NMR studies is the lack of an affordable eukaryotic expression system for isotope labeling. Here, a simple and affordable protocol is presented to produce uniform labeled proteins in the most prevalent eukaryotic expression system for structural biology, namely Spodoptera frugiperda insect cells. Incorporation levels of 80 % can be achieved for (15)N and (13)C with yields comparable to expression in full media. For (2)H,(15)N and (2)H,(13)C,(15)N labeling, incorporation is only slightly lower with 75 and 73 %, respectively, and yields are typically twofold reduced. The media were optimized for isotope incorporation, reproducibility, simplicity and cost. High isotope incorporation levels for all labeling patterns are achieved by using labeled algal amino acid extracts and exploiting well-known biochemical pathways. The final formulation consists of just five commercially available components, at costs 12-fold lower than labeling media from vendors. The approach was applied to several cytosolic and secreted target proteins. PMID:25929326

  11. Local and global dynamics of atactic polypropylene melts by multiple field 13C nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Qiu, XiaoHua; Moe, N. E.; Ediger, M. D.; Fetters, Lewis J.

    2000-08-01

    13C NMR T1, NOE, and T1? were measured for an atactic polypropylene (aPP) melt at 5, 25, 75, and 125 MHz 13C Larmor frequencies from 43 °C to 260 °C. The data were fit very well with a model for C-H vector reorientation composed of very fast librational relaxation, intermediate segmental relaxation, and a normal mode contribution described by Rouse dynamics modified for entanglement effects. The longest relaxation time calculated from this fit agrees reasonably well with the value obtained from viscoelastic measurements on similar systems. The amplitude of the normal mode contribution for aPP is much smaller than that found for polyethylene in a previous study. The temperature dependence of the segmental dynamics is very similar to that of the viscosity indicating that conformational transitions are the fundamental motions for flow for aPP. The width of the distribution of relaxation times of segmental dynamics remains unchanged at about 1.3 decades from Tg+45 to Tg+250 K.

  12. Access to NMR Spectroscopy for Two-Year College Students: The NMR Site at Trinity University

    ERIC Educational Resources Information Center

    Mills, Nancy S.; Shanklin, Michael

    2011-01-01

    Students at two-year colleges and small four-year colleges have often obtained their exposure to NMR spectroscopy through "canned" spectra because the cost of an NMR spectrometer, particularly a high-field spectrometer, is prohibitive in these environments. This article describes the design of a NMR site at Trinity University in which spectral

  13. ESR Investigations on 13C enriched Sc3@C82

    NASA Astrophysics Data System (ADS)

    Rahmer, J.; Mehring, M.; Dorn, H. C.

    2002-10-01

    13C enrichment of Sc3@C82 for the first time allows the resolution of 13C hyperfine satellite lines in the electron spin resonance (ESR) spectra of this material. A simple model is proposed to simulate the spectra. The ESR data is well reproduced under the assumption that two or three carbon atoms have a significantly stronger hyperfine coupling than all other atoms. Relating this result to the geometry of the C3? cage leads to the conclusion that the electron density is concentrated on the upper hemisphere of the C82 cage.

  14. Chemical ligation of the influenza M2 protein for solid-state NMR characterization of the cytoplasmic domain.

    PubMed

    Kwon, Byungsu; Tietze, Daniel; White, Paul B; Liao, Shu Y; Hong, Mei

    2015-07-01

    Solid-state NMR-based structure determination of membrane proteins and large protein complexes faces the challenge of limited spectral resolution when the proteins are uniformly (13) C-labeled. A strategy to meet this challenge is chemical ligation combined with site-specific or segmental labeling. While chemical ligation has been adopted in NMR studies of water-soluble proteins, it has not been demonstrated for membrane proteins. Here we show chemical ligation of the influenza M2 protein, which contains a transmembrane (TM) domain and two extra-membrane domains. The cytoplasmic domain, which contains an amphipathic helix (AH) and a cytoplasmic tail, is important for regulating virus assembly, virus budding, and the proton channel activity. A recent study of uniformly (13) C-labeled full-length M2 by spectral simulation suggested that the cytoplasmic tail is unstructured. To further test this hypothesis, we conducted native chemical ligation of the TM segment and part of the cytoplasmic domain. Solid-phase peptide synthesis of the two segments allowed several residues to be labeled in each segment. The post-AH cytoplasmic residues exhibit random-coil chemical shifts, low bond order parameters, and a surface-bound location, thus indicating that this domain is a dynamic random coil on the membrane surface. Interestingly, the protein spectra are similar between a model membrane and a virus-mimetic membrane, indicating that the structure and dynamics of the post-AH segment is insensitive to the lipid composition. This chemical ligation approach is generally applicable to medium-sized membrane proteins to provide site-specific structural constraints, which complement the information obtained from uniformly (13) C, (15) N-labeled proteins. PMID:25966817

  15. Two dimensional NMR and NMR relaxation studies on coal structure. Final report, September 13, 1994--January 31, 1995

    SciTech Connect

    Zilm, K.W.

    1995-10-01

    This research program focused on developing new solids nuclear magnetic resonance (NMR) techniques for improved analysis of coal structure. Most work has been concentrated on the development of spectral editing NMR methods for solids.

  16. Variations in 13 C discrimination during CO2 exchange by

    E-print Network

    not predicted by either of the said models. Exploring the sensitivity of 13 D to possible respiratory isotope). The magnitude of photosyn- thetic 13 C discrimination is sensitive to environmental vari- ables such as vapour that of concurrent plant and soil respiratory fluxes, creating transient isotopic disequilibria (Lloyd et al. 1996

  17. Low-energy resonances in 13C(?,n)

    NASA Astrophysics Data System (ADS)

    Brune, C. R.; Licot, I.; Kavanagh, R. W.

    1993-12-01

    Two new resonances in the 13C(?,n) reaction, at E?=656 and 802 keV, have been observed and the resonance strengths have been measured. Limits on the (?,?) strengths have been determined. Strengths for previously known (?,n) resonances at 1053 and 1586 keV are also reported.

  18. Metabolic flux analysis using 13C peptide label measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    13C metabolic flux analysis (MFA) has become the experimental method of choice to investigate cellular metabolism. MFA has established flux maps of central metabolism for dozens of microbes, cell cultures, and plant seeds. Steady-state MFA utilizes isotopic labeling measurements of amino acids obtai...

  19. Modeling of the 2007 JET ^13C migration experiments

    NASA Astrophysics Data System (ADS)

    Strachan, J. D.; Likonen, J.; Hakola, A.; Coad, J. P.; Widdowson, A.; Koivuranta, S.; Hole, D. E.; Rubel, M.

    2010-11-01

    Using the last run day of the 2007 JET experimental campaign, ^13CH4 was introduced repeatedly from the vessel top into a single plasma type (H-mode, Ip= 1.6 MA, Bt= 1.6 T). Similar experiments were performed in 2001 (vessel top into L-Mode) and 2004 (outer divertor into H-Mode). Divertor and wall tiles were removed and been analysed using secondary ion mass spectrometry (SIMS) and Rutherford backscattering (RBS) to determine the ^13C migration. ^13C was observed to migrate both to the inner (largest deposit), outer divertor (less) , and the floor tiles (least). This paper reports the EDGE2D/NIMBUS based modelling of the carbon migration. The emphasis is on the comparison of the 2007 results with the 2001 results where both injections were from the machine top but ELMs were present in 2007 but not present in 2001. The ELMs seemed to cause more ^13C re-erosion near the inner strike point. Also of interest is the difference in the Private Flux Region deposits where the changes in divertor geometry between 2004 and 2007 caused differences in the deposits. In 2007, the tilting of the load bearing tile caused regions of the PFR to be shadowed from the inner strike point which were not shadowed in 2004, indicating ^13C neutrals originated from the OSP.

  20. Does the Shuram ?13C excursion record Ediacaran oxygenation?

    NASA Astrophysics Data System (ADS)

    Husson, J. M.; Maloof, A. C.; Schoene, B.; Higgins, J. A.

    2013-12-01

    The most negative carbon isotope excursion in Earth history is found in carbonate rocks of the Ediacaran Period (635-542 Ma). Known colloquially as the the 'Shuram' excursion, workers have long noted its tantalizing, broad concordance with the rise of abundant macro-scale fossils in the rock record, variously interpreted as animals, giant protists, macro-algae and lichen, and known as the 'Ediacaran Biota.' Thus, the Shuram excursion has been interpreted by many in the context of a dramatically changing redox state of the Ediacaran oceans - e.g., a result of methane cycling in a low O2 atmosphere, the final destruction of a large pool of recalcitrant dissolved organic carbon (DOC), and the step-wise oxidation of the Ediacaran oceans. More recently, diagenetic interpretations of the Shuram excursion - e.g. sedimentary in-growth of very ?13C depleted authigenic carbonates, meteoric alteration of Ediacaran carbonates, late-stage burial diagenesis - have challenged the various Ediacaran redox models. A rigorous geologic context is required to discriminate between these explanatory models, and determine whether the Shuram excursion can be used to evaluate terminal Neoproterozoic oxygenation. Here, we present chemo-stratigraphic data (?13C, ?18O, ?44/42Ca and redox sensitive trace element abundances) from 12 measured sections of the Ediacaran-aged Wonoka Formation (Fm.) of South Australia that require a syn-depositional age for the extraordinary range of ?13C values (-12 to +4‰) observed in the formation. In some locations, the Wonoka Fm. is ~700 meters (m) of mixed shelf limestones and siliclastics that record the full 16 ‰ ?13C excursion in a remarkably consistent fashion across 100s of square kilometers of basin area. Fabric-altering diagenesis, where present, occurs at the sub-meter vertical scale, only results in sub-permil offsets in ?13C and cannot be used to explain the full ?13C excursion. In other places, the Wonoka Fm. is host to deep (1 km) paleocanyons, which are partly filled by tabular-clast carbonate breccias that are sourced from eroded Wonoka canyon-shoulders. By measuring the isotopic values of 4100 canyon-shoulder horizons and carbonate clasts (an isotope conglomerate test), we show that canyon-shoulder carbonates acquired their ?13C-?18O values before brecciation and redeposition in the paleocanyons, thereby ruling out late stage alteration models and placing interpretations that depend upon the Ediacaran ocean redox state on firmer ground.

  1. The 12C/13C Isotopic Ratio In Titan's Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Nixon, Conor A.; Achterberg, R. K.; Vinatier, S.; Bezard, B.; Coustenis, A.; Teanby, N. A.; Irwin, P. G.; Cassini CIRS Team

    2007-10-01

    Isotopic ratios in planetary atmospheres are of considerable interest, yielding insights both about currently occurring processes, and also the formation and early evolution of the body. Before Cassini, ground-based measurements of Titan's 12C/13C in HCN showed no firm evidence of deviation from the terrestrial inorganic standard (88.9) - albeit with large error bars of 20% - contrasting the enrichment in nitrogen (15N/14N?4.5 terrestrial). Since 2004, the Composite Infrared Spectrometer (CIRS) instrument on Cassini has recorded spectra of Titan's stratosphere globally, including the emissions of multiple isotopologues for certain hydrocarbons. We selected spectra for analysis from four flybys (T4, T12, T19, T22), covering five latitudes from 65°S to 71°N. By means of a radiative transfer code and inversion scheme, we have first modeled the ?4 band of 12CH4 at 1304 cm-1 to retrieve stratospheric temperatures, and subsequently the emissions of 13CH4, 12C2H2, 13C12CH2, 12C2H6 and 13C12CH6. Our results indicate 12C/13C = 81.2±2.0 for all three species combined over all five latitudes, in excellent agreement with the Huygens GCMS value of 12CH4/13CH4 = 82.3±1.0 (Niemann et al. 2005), some 9% lower than terrestrial inorganic, and lower than in ethane on Saturn (91 (-13) (+26)) and Jupiter (99 (-23) (+43)) (Sada et al. 1996). No latitude variation was detected, however the 12C/13C in the C2 species (83.9±3.1 in acetylene, 89.9±7.2 in ethane) were consistently higher than in methane (78.0±2.7) after considering random errors. Although it is possible that this is a real chemical or physical (condensation) effect, it is more likely due to systematic errors in our temperature profile, as our spectra do not yield independent temperature information at 10 mbar where the emissions of 13C12CH2 and 13C12CH6 originate, and we default to the Huygens probe temperatures. In future, this problem may be resolved by modeling CIRS limb spectra.

  2. Vertical ?13C and ?15N changes during pedogenesis

    NASA Astrophysics Data System (ADS)

    Brunn, Melanie; Spielvogel, Sandra; Wells, Andrew; Condron, Leo; Oelmann, Yvonne

    2015-04-01

    The natural abundance of soil organic matter (SOM) stable C and N isotope ratios are subjected to vertical changes throughout the soil profile. This vertical distribution is a widely reported phenomenon across varieties of ecosystems and constitutes important insights of soil carbon cycling. In most ecosystems, SOM becomes enriched in heavy isotopes by several per mill in the first few centimeters of the topsoil. The enrichment of 13C in SOM with soil depth is attributed to biological and physical-chemical processes in soil e.g., plant physiological impacts, microbial decomposition, sorption and transport processes. Such vertical trends in 13C and 15N abundance have rarely been related to SOM composition during pedogenesis. The aims of our study were to investigate short and long-term ?13C and ?15N depth changes and their interrelations under progressing pedogenesis and ecosystem development. We sampled soils across the well studied fordune progradation Haast-chronosequence, a dune ridge system under super-humid climate at the West Coast of New Zealand's South Island (43° 53' S, 169° 3' E). Soils from 11 sites with five replicates each covered a time span of around 2870 yr of soil development (from Arenosol to Podzol). Vertical changes of ?13C and ?15N values of SOM were investigated in the organic layers and in 1-cm depth intervals of the upper 10 cm of the mineral soil. With increasing soil depth SOM became enriched in ?13C by 1.9 ± SE 0.1 o and in ?15N by 6.0 ± 0.4 ‰?Litter ?13C values slightly decreased with increasing soil age (r = -0.61; p = 0.00) likely due to less efficient assimilation linked to nutrient limitations. Fractionation processes during mycorrhizal transfer appeared to affect ?15N values in the litter. We found a strong decrease of ?15N in the early succession stages ? 300 yr B.P. (r = -0.95; p = 0.00). Positive relations of vertical 13C and 15N enrichment with soil age might be related to decomposition and appeared to be affected by a change of hydrology, nutrient limitations, secondary minerals and root impacts. The investigation of vertical changes of soil organic matter (SOM) stable isotope ratios provides the opportunity to detect combined processes that enhance our understanding of terrestrial ecosystem functioning and pedogenetic processes leading to stabilization/destabilization in soil and therefore addressing the soil's sink/source function.

  3. 13 C-Methyl isocyanide as an NMR probe for cytochrome P450 active sites

    Microsoft Academic Search

    Christopher R. McCullough; Phani Kumar Pullela; Sang-Choul Im; Lucy Waskell; Daniel S. Sem

    2009-01-01

    The cytochromes P450 (CYPs) play a central role in many biologically important oxidation reactions, including the metabolism\\u000a of drugs and other xenobiotic compounds. Because they are often assayed as both drug targets and anti-targets, any tools that\\u000a provide: (a) confirmation of active site binding and (b) structural data, would be of great utility, especially if data could\\u000a be obtained in

  4. 13 C NMR Study of the Acid-Catalyzed Carbonylation of Methyl tert Butyl Ether (MTBE)

    Microsoft Academic Search

    Ned C. Haubein; Linda J. Broadbelt; Edmund J. Mozeleski; Richard H. Schlosberg; Raymond A. Cook; Christian P. Mehnert; Dan F?rca?iu

    2002-01-01

    Methyl tert-butyl ether (MTBE) is a widely used additive in oxygenated gasoline that has recently been identified as a potential health threat to the drinking water supply due to leaking underground storage tanks. One alternate use for MTBE is the production of methyl 2,2-dimethylpropanoate (methyl pivalate) via Koch carbonylation chemistry. BF3\\/H2O catalysts are employed in industrial applications of Koch chemistry,

  5. 13C DYNAMIC NUCLEAR POLARIZATION: AN ALTERNATIVE DETECTOR FOR RECYCLED-FLOW NMR EXPERIMENTS. (R824871)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  6. In vivo investigation of cardiac metabolism in the rat using MRS of hyperpolarized [1-13C] and [2-13C]pyruvate

    PubMed Central

    Josan, Sonal; Park, Jae Mo; Hurd, Ralph; Yen, Yi-Fen; Pfefferbaum, Adolf; Spielman, Daniel; Mayer, Dirk

    2013-01-01

    Hyperpolarized 13C MRS allows the in vivo assessment of pyruvate dehydrogenase complex (PDC) flux, which converts pyruvate to acetyl-coenzyme A (acetyl-CoA). [1-13C]pyruvate has been used to measure changes in cardiac PDC flux, with demonstrated increase in 13C-bicarbonate production after dichloroacetate (DCA) administration. With [1-13C]pyruvate, the 13C label is released as 13CO2/13C-bicarbonate, and, hence, does not allow to follow the fate of acetyl-CoA. Pyruvate labeled in the C2 position has been used to track the 13C label into the TCA cycle and measure [5-13C]glutamate as well as study changes in [1-13C]acetylcarnitine with DCA and dobutamine. This work investigates changes in the metabolic fate of acetyl-CoA in response to metabolic interventions of DCA-induced increased PDC flux in the fed and fasted state, and increased cardiac workload with dobutamine in vivo in rat heart at two different pyruvate doses. DCA led to a modest increase in the 13C labeling of [5-13C]glutamate, and a considerable increase in [1-13C]acetylcarnitine and [1,3-13C]acetoacetate peaks. Dobutamine resulted in an increased labeling of [2-13C]lactate, [2-13C]alanine and [5-13C]glutamate. The change in glutamate with dobutamine was observed using a high pyruvate dose but not with a low dose. The relative changes in the different metabolic products provide information about the relationship between PDC-mediated oxidation of pyruvate and its subsequent incorporation into TCA cycle compared to other metabolic pathways. Using a high dose of pyruvate may provide an improved ability to observe changes in glutamate. PMID:23904148

  7. 13C nuclear Overhauser polarization nuclear magnetic resonance in rotating solids: Replacement of cross polarization in uniformly 13C labeled molecules with methyl groups

    NASA Astrophysics Data System (ADS)

    Takegoshi, K.; Terao, Takehiko

    2002-07-01

    A new 13C polarization technique in solids is presented on the basis of a recently proposed 13C-13C recoupling sequence [13C-1H dipolar-assisted rotational resonance (DARR), K. Takegoshi, S. Nakamura, and T. Terao, Chem. Phys. Lett. 344, 631 (2001)] operative under fast magic angle spinning (MAS), in which a rf field is applied to 1H with a rotary resonance condition but none to 13C. The 1H irradiation in DARR saturates 1H signals, leading to the 13C signal enhancement due to the nuclear Overhauser effect for fast rotating methyl groups, if any. If we use a uniformly 13C labeled sample, 13C-13C polarization transfer enhanced by DARR successively distributes the enhanced methyl carbon polarization to the other 13C spins, leading to uniform enhancement for all 13C spins even under very fast MAS. In uniformly 13C labeled rotating samples, the enhancement factor in cross polarization (CP) is about 2