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1

Phosphorus-31 NMR Spectra of Some Tertiary Phosphine Rhodium Compounds.  

National Technical Information Service (NTIS)

Phosphorus-31 nmr data are reported for trans-chlorocarbonylbis (tris-phenylphosphine) rhodium (I) and for three compounds of the type tri-chlorotris(Triorganophosphine) rhodium (III). The spectra unambiguously confirm the trans configurations for the rho...

S. O. Grim R. A. Ference

1966-01-01

2

Phosphorus31 NMR studies of maltose and glucose metabolism in Streptococcus lactis  

Microsoft Academic Search

Streptococcus lactis ferments glucose in a homolactic fashion but a heterolactic fermentation pattern is observed when it is grown on maltose. Using in vivo phosphorus-31 and carbon-13 NMR studies of glucose-metabolizing cells we confirmed that fructosediphosphate (FDP) is the major glycolytic intermediate and that the production of lactate causes major changes both in the intra- and extracellular pH values. Starved

Elke M. Lohmeier-Vogel; Bärbel Hahn-Hägerdahl; Hans J. Vogel

1986-01-01

3

Hydrolysis of Pyrophosphate in a Highly Calcareous Soil: A Solid-State Phosphorus31 NMR Study  

Microsoft Academic Search

PyrophosphateisthemainformofcondensedPinthefluidfertilizer ammonium polyphosphate (APP). When APP is applied to soil, pyro- phosphate is hydrolyzed to orthophosphate. Hydrolysis of pyrophos- phatewas investigated in a highly calcareous soil over 3 wk. Changes in P speciation were measured using solid-state 31 P nuclear magnetic resonance (NMR) spectroscopy for dried soil samples and ion chro- matography for NaOH extracts. Both techniques showed a decrease

T. M. McBeath; R. J. Smernik; E. Lombi; M. J. McLaughlin

4

Phosphorus-31 NMR magnetization-transfer measurements of ATP turnover during steady-state isometric muscle contraction in the rat hind limb in vivo  

SciTech Connect

Phosphorus-31 NMR magnetization-transfer measurement have been used to measure the flux between ATP and inorganic phosphate during steady-state isometric muscle contraction in the rat hind limb in vivo. Steady-state contraction was obtained by supramaximal sciatic nerve stimulation. Increasing the stimulation pulse width from 10 to 90 ms, at a pulse frequency of 1 Hz, or increasing the frequency of a 10-ms pulse from 0.5 to 2 Hz resulted in an increase in the flux which was an approximately linear function of the increase in the tension-time integral. The flux showed an approximately linear dependence on the calculated free cytosolic ADP concentration up to an ADP concentration of about 90 {mu}M. The data are consistent with control of mitochondrial ATP synthesis by the cytosolic ADP concentration and indicate that the apparent K{sub m} of the mitochondria for ADP is at least 30 {mu}M.

Brindle, K.M.; Blackledge, M.J.; Challiss, R.A.J.; Radda, G.K. (Univ. of Oxford (England))

1989-05-30

5

Solid-state phosphorus-31 NMR spectroscopy of a multiple-spin system: an investigation of a rhodium-triphosphine complex.  

PubMed

Phosphorus-31 NMR spectra of solid [tris(dimethylphenylphosphine)](2,5-norbornadiene) rhodium(I) hexafluorophosphate have been acquired at several applied magnetic field strengths. The phosphorus nuclei of the three phosphine ligands are spin-spin coupled to each other and to 103Rh, resulting in complex NMR spectra; however, the three phosphorus chemical shift (CS) tensors were determined through the analysis of NMR spectra of slow magic angle spinning and stationary samples. Spectra of spinning samples in rotational resonance and two-dimensional 31P NMR spectra were particularly useful for determining the magnitudes of the indirect spin-spin couplings, and to probe their signs. Despite being in similar environments, the three phosphorus nuclei of the phosphine ligands have distinct CS tensors. In particular, the spans of these tensors, delta11-delta33, range from 80 to 176 ppm. The phosphorus CS tensors have been assigned to specific sites determined by X-ray crystallography, based on a combination of the experimental results and the results of quantum chemical calculations of the phosphorus shielding and 2J(31P,31P) values. The effect of coordination of dimethylphenylphosphine with rhodium has been investigated by comparing calculated phosphorus CS tensors for the uncoordinated ligand with those obtained for the ligands in the complex. PMID:18956090

Bernard, Guy M; Feindel, Kirk W; Wasylishen, Roderick E; Cameron, T Stanley

2008-09-28

6

Mechanism of adenylate kinase. Demonstration of a functional relationship between aspartate 93 and Mg sup 2+ by site-directed mutagenesis and proton, phosphorus-31, and magnesium-25 NMR  

SciTech Connect

Earlier magnetic resonance studies suggested no direct interaction between Mg{sup 2+} ions and adenylate kinase (AK) in the AK{center dot}MgATP (adenosine 5'-triphosphate) complex. However, recent NMR studies concluded that the carboxylate of aspartate 119 accepts a hydrogen bond from a water ligand of the bound Mg{sup 2+} ion in the muscle AK {center dot} MgATP complex. On the other hand, in the 2.6-{angstrom} crystal structure of the yeast AK{center dot}MgAP{sub 5}A (P{sup 1}, P{sup 5}-bis(5'-adenosyl)pentaphosphate) complex, the Mg{sup 2+} ion is in proximity to aspartate 93. Substitution of Asp-93 with alanine resulted in no change in dissociation constants, 4-fold increases in K{sub m}, and a 650-fold decrease in k{sub cat}. Notable changes have been observed in the chemical shifts of the aromatic protons of histidine 36 and a few other aromatic residues. However, the results of detailed analyses of the free enzymes and the AK{center dot}MgAP{sub 5}A complexes by one- and two-dimensional NMR suggested that the changes are due to localized perturbations. Thus it is concluded that Asp-93 stabilizes the transition state by ca. 3.9 kcal/mol. Other results raised the question of whether Mg{sup 2+} could bind to D93A{center dot}nucleotide complexes, which was then probed by {sup 25}MgNMR. The results suggest that Mg{sup 2+} does bind to the D93A{center dot}AP{sub 5}A complex, but possibly only weakly.

Yan, Honggao; Tsai, Mingdaw (Ohio State Univ., Columbus (United States))

1991-06-04

7

Flavodoxin from Anabaena 7120: uniform nitrogen-15 enrichment and hydrogen-1, nitrogen-15, and phosphorus-31 NMR investigation of the flavin mononucleotide binding site in the reduced and oxidized states  

SciTech Connect

Interactions between flavin mononucleotide (FMN) and apoprotein have been investigated in the reduced and oxidized states of the flavodoxin isolated from Anabaena 7120 (M/sub r/ approx. 21,000). /sup 1/H, /sup 15/N, and /sup 31/P NMR have been used to characterize the FMN-protein interactions in both redox states. These are compared with those seen in other flavodoxins. Uniformly enriched (/sup 15/N) flavodoxin was isolated from Anabaena 7120 grown on K/sup 15/NO/sub 3/ as the sole nitrogen source. /sup 15/N insensitive nucleus enhanced by polarization transfer (INEPT) and nuclear Overhauser effect (NOE) studies of this sample provided information regarding protein structure and dynamics. A /sup 1/H-detected /sup 15/N experiment allowed the correlation of nitrogen resonances to those of their attached protons. Over 90% of the expected N-H cross peaks could be resolved in this experiment.

Stockman, B.J.; Westler, W.M.; Mooberry, E.S.; Markley, J.L.

1988-01-12

8

Poly(Tertiary Phosphines and Arsines). XI. Phosphorus-31 Nuclear Magnetic Resonance Studies on Some Metal Complexes of Poly(Tertiary, Phosphines).  

National Technical Information Service (NTIS)

Proton noise-decoupled pulsed Fourier transform phosphorus-31 NMR spectra of metal complexes of the di(tertiary phosphine) (CH3)2PCH2CH2P(C6H5)2, the symmetrical tri(tertiary Phosphines) R'P(CH2CH2PR2) (R and R' = methyl or phenyl), the unsymmetrical tri(...

R. B. King J. C. Cloyd

1974-01-01

9

Soil and litter phosphorus-31 nuclear magnetic resonance spectroscopy: extractants, metals, and phosphorus relaxation times.  

PubMed

Phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy is an excellent tool with which to study soil organic P, allowing quantitative, comparative analysis of P forms. However, for 31P NMR to be tative, all peaks must be completely visible, and in their correct relative proportions. There must be no line broadening, and adequate delay times must be used to avoid saturation of peaks. The objective of this study was to examine the effects of extractants on delay times and peak saturation. Two samples (a forest litter and a mineral soil sample) and three extractants (0.25 M NaOH, NaOH plus Chelex (Bio-Rad Laboratories, Hercules, CA), and NaOH plus EDTA) were used to determine the differences in the concentration of P and cations solubilized by each extractant, and to measure spin-lattice (T1) relaxation times of P peaks in each extract. For both soil and litter, NaOH-Chelex extracted the lowest concentrations of P. For the litter sample, T1 values were short for all extractants due to the high Fe concentration remaining after extraction. For the soil sample, there were noticeable differences among the extractants. The NaOH-Chelex sample had less Fe and Mn remaining in solution after extraction than the other extractants, and the longest delay times used in the study, 6.4 s, were not long enough for quantitative analysis. Delay times of 1.5 to 2 s for the NaOH and NaOH-EDTA were adequate. Line broadening was highest in the NaOH extracts, which had the highest concentration of Fe. On the basis of these results, recommendations for future analyses of soil and litter samples by solution 31P NMR spectroscopy include: careful selection of an extractant; measurement of paramagnetic ions extracted with P; use of appropriate delay times and the minimum number of scans; and measurement of T1 values whenever possible. PMID:11931434

Cade-Menun, B J; Liu, C W; Nunlist, R; McColl, J G

2002-01-01

10

Transverse nuclear spin relaxation of fluorine-19 and phosphorus-31 in PFO3S in high magnetic fields  

SciTech Connect

The low-frequency line in the ZF NMR spectrum of PFO3S is much broader than the high-frequency line while for the T P NMR spectrum the high-frequency line is broader than the low-frequency line. The experimental conditions needed for the occurrence of such differential line broadening (DLB) in coupled spin systems are discussed. Experimental measurements of T/sub 1p/ and the line widths for fluorine-19 and phosphorus-31 are reported for the PFO3S ion in water-ethylene glycol solutions. These results are compared to the theoretical predictions of Shimizu. Theory and experiment are in excellent agreement. The absolute sign of the spin coupling constant is negative, J/sub PF/ = -870.0 +/- 0.5 Hz. It is shown that T/sub 1p/ measurements of simple two-spin systems can be used to obtain accurate information about the chemical shift anisotropy of the two spins, the bond distance, and the molecular correlation time.

Farrar, T.C.; Quintero-Arcaya, R.A.

1987-06-04

11

Noninvasive study of high-energy phosphate metabolism in human heart by depth-resolved T P NMR spectroscopy  

Microsoft Academic Search

Phosphorus-31 nuclear magnetic resonance (NMR) spectra showing the relative concentrations of high-energy phosphate metabolites have been recorded noninvasively from the human heart in vivo. Spectral data were spatially localized by combining a pulsed magnetic field gradient with surface NMR excitation-detection coils. The location of the selected spectral region was determined by conventional proton NMR imaging immediately before examination by phosphorus-31

P. Bottomley

1985-01-01

12

Deuterium and phosphorus-31 nuclear magnetic resonance study of the interaction of melittin with dimyristoylphosphatidylcholine bilayers and the effects of contaminating phospholipase A/sub 2/  

SciTech Connect

The interaction of bee venom melittin with dimyristoylphosphatidylcholine (DMPC) selectively deuteriated in the choline head group has been studied by deuterium and phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy. The action of residual phospholipase A/sub 2/ in melittin samples resulted in mixtures of DMPC and its hydrolytic products that underwent reversible transitions at temperatures between 30 and 35/sup 0/C from extended bilayers to micellar particles which gave narrow single-line deuterium and phosphorus-31 NMR spectra. Similar transitions were observed in DMPC-myristoyllysophosphatidylcholine (lysoPC)-myristic acid mixtures containing melittin but not in melittin-free mixtures, indicating that melittin is able to stabilize extended bilayers containing DMPC and its hydrolytic products in the liquid-crystalline phase. Melittin, free of phospholipase A/sub 2/ activity, and at 3-5 mol % relative to DMPC, induced reversible transitions between extended bilayers and micellar particles on passing through the liquid-crystalline to gel phase transition temperature of the lipid, effects similar to those observed in melittin-acyl chain deuteriated dipalmitoylphosphatidylcholine (DPPC) mixtures. LysoPC at concentrations of 20 mol % or greater relative to DMPC induced transitions between extended bilayers and micellar particles with characteristics similar to those induced by melittin. It is proposed that these melittin- and lysoPC-induced transitions share similar mechanisms. The effects of melittin on the quadrupole splittings and T/sub 1/ relaxation times of head-group-deuteriated DMPC in the liquid-crystalline phase share features similar to the effects of metal ions on DPPC head groups, indicating that the conformational properties of the choline head group in PC bilayers may be affected by melittin and by metal ions in a similar manner.

Dempsey, C.E.; Watts, A.

1987-09-08

13

In vivo phosphorus-31 nuclear magnetic resonance reveals lowered ATP during heat shock of Tetrahymena  

SciTech Connect

Cells synthesize a characteristic set of proteins--heat shock proteins--in response to a rapid temperature jump or certain other stress treatments. The technique of phosphorus-31 nuclear magnetic resonance spectroscopy was used to examine in vivo the effects of temperature jump on two species of Tetrahymena that initiate the heat shock response at different temperatures. An immediate 50 percent decrease in cellular adenosine triphosphate was observed when either species was jumped to a temperature that strongly induces synthesis of heat shock proteins. This new adenosine triphosphate concentration was maintained at the heat shock temperature.

Findly, R.C.; Gillies, R.J.; Shulman, R.G.

1983-03-11

14

Phosphorus-31 MRI of hard and soft solids using quadratic echo line-narrowing  

PubMed Central

Magnetic resonance imaging (MRI) of solids is rarely attempted. One of the main reasons is that the broader MR linewidths, compared to the narrow resonance of the hydrogen (1H) in free water, limit both the attainable spatial resolution and the signal-to-noise ratio. Basic physics research, stimulated by the quest to build a quantum computer, gave rise to a unique MR pulse sequence that offers a solution to this long-standing problem. The “quadratic echo” significantly narrows the broad MR spectrum of solids. Applying field gradients in sync with this line-narrowing sequence offers a fresh approach to carry out MRI of hard and soft solids with high spatial resolution and with a wide range of potential uses. Here we demonstrate that this method can be used to carry out three-dimensional MRI of the phosphorus (31P) in ex vivo bone and soft tissue samples.

Frey, Merideth A.; Michaud, Michael; VanHouten, Joshua N.; Insogna, Karl L.; Madri, Joseph A.; Barrett, Sean E.

2012-01-01

15

Phosphorus-31 MRI of hard and soft solids using quadratic echo line-narrowing.  

PubMed

Magnetic resonance imaging (MRI) of solids is rarely attempted. One of the main reasons is that the broader MR linewidths, compared to the narrow resonance of the hydrogen ((1)H) in free water, limit both the attainable spatial resolution and the signal-to-noise ratio. Basic physics research, stimulated by the quest to build a quantum computer, gave rise to a unique MR pulse sequence that offers a solution to this long-standing problem. The "quadratic echo" significantly narrows the broad MR spectrum of solids. Applying field gradients in sync with this line-narrowing sequence offers a fresh approach to carry out MRI of hard and soft solids with high spatial resolution and with a wide range of potential uses. Here we demonstrate that this method can be used to carry out three-dimensional MRI of the phosphorus ((31)P) in ex vivo bone and soft tissue samples. PMID:22431609

Frey, Merideth A; Michaud, Michael; VanHouten, Joshua N; Insogna, Karl L; Madri, Joseph A; Barrett, Sean E

2012-04-01

16

Phosphorus-31 nuclear magnetic resonance spectroscopic study of the canine pancreas: applications to acute alcoholic pancreatitis  

SciTech Connect

The first nuclear magnetic resonance spectroscopic study of the canine pancreas is described. Both in-vivo, ex-vivo protocols and NMR observables are discussed. The stability of the ex-vivo preparation based on the NMR observables is established for at least four hours. The spectra obtained from the in-vivo and ex-vivo preparations exhibited similar metabolite ratios, further validating the model. Metabolite levels were unchanged by a 50% increase in perfusion rate. Only trace amounts of phosphocreatine were observed either in the intact gland or in extracts. Acute alcoholic pancreatitis was mimicked by free fatty acid infusion. Injury resulted in hyperamylasemia, edema (weight gain), increased hematocrit and perfusion pressure, and depressed levels of high energy phosphates.

Janes, N.; Clemens, J.A.; Glickson, J.D.; Cameron, J.L.

1988-01-01

17

Preliminary Study on Hepatocyte-Targeted Phosphorus-31 MRS Using ATP-Loaded Galactosylated Chitosan Oligosaccharide Nanoparticles  

PubMed Central

Background. The clinical applications of hepatic phosphorus-31 magnetic resonance spectroscopy (31P MRS) remain to be difficult because the changes of phosphates between normal hepatic tissues and pathological tissues are not so obvious, and furthermore, up to now there is few literature on hepatocyte-targeted 31P MRS. Materials and Methods. The ATP-loaded Gal-CSO (Gal-CSO/ATP) nanoparticles were prepared and the special cellular uptake of them as evaluated by using HepG-2 tumor cells and A549 tumor cells, respectively. Two kinds of cells were incubated with the nanoparticles suspension, respectively. Then were prepared the cell samples and the enhancement efficiency of ATP peaks detected by 31P MRS was evaluated. Results. The cellular uptake rate of Gal-CSO/ATP nanoparticles in HepG-2 cells was higher than that in A549 cells. Furthermore, the enlarged ATP peaks of Gal-CSO/ATP nanoparticles in HepG-2 cells were higher than those in A549 cells in vitro detected by 31P MRS. Conclusions. Gal-CSO/ATP nanoparticles have significant targeting efficiency in hepatic cells in vitro and enhancement efficiency of ATP peaks in HepG-2 cells. Furthermore, 31P MRS could be applied in the research of hepatic molecular imaging.

Yu, Ri-Sheng; Zhu, Xiu-Liang; Sun, Jian-Zhong; Shi, Dan; Chen, Ying; Wang, Zhi-Kang; Tang, Ke-Zhong; Du, Yong-Zhong

2013-01-01

18

Transverse nuclear spin relaxation of fluorine-19 and phosphorus-31 in PFO3S in high magnetic fields  

Microsoft Academic Search

The low-frequency line in the ZF NMR spectrum of PFO3S is much broader than the high-frequency line while for the T P NMR spectrum the high-frequency line is broader than the low-frequency line. The experimental conditions needed for the occurrence of such differential line broadening (DLB) in coupled spin systems are discussed. Experimental measurements of T\\/sub 1p\\/ and the line

T. C. Farrar; R. A. Quintero-Arcaya

1987-01-01

19

Interactions of inorganic mercury with phospholipid micelles and model membranes. A 31 P-NMR study  

Microsoft Academic Search

The binding of inorganic mercury Hg(II) to phospholipid headgroups has been investigated by phosphorus-31 nuclear magnetic resonance of phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylcholine (PC) in water micellar and multilamellar phases. HgCl2 triggers the aggregation of phospholipid micelles, leading to a lipid-mercury precipitate that is no longer detectable by high-resolution31P-NMR. The remaining signal area corresponds to micelles in the soluble

Laurent Girault; Philippe Lemaire; Alain Boudou; Jean-Claude Debouzy; Erick J. Dufourc

1996-01-01

20

Destabilization of cationic lipid vesicles by an anionic hydrophobically modified poly( N-isopropylacrylamide) copolymer: a solid-state 31P NMR and 2H NMR study  

Microsoft Academic Search

The effect of binding PNIPAM–Py–Gly, a copolymer of N-isopropylacrylamide, N-[4-(1-pyrenyl)butyl]-N-n-octadecylacrylamide and N-glycydyl-acrylamide, on membrane stability in cationic multilamellar vesicles (MLVs) was examined using solid-state phosphorus (31P) and deuterium (2H) nuclear magnetic resonance (NMR) spectroscopy. For MLVs of composition n-octadecyldiethylene oxide (ODEO)+cholesterol (CHOL)+1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)+dimethyldioctadecylammonium bromide (DODAB) (molar ratios 75:10.5:10.5:4), PNIPAM–Py–Gly induced a complete conversion from a bilayer-type 31P NMR spectrum to

Carla M. Franzin; Peter M. Macdonald; Alla Polozova; Françoise M. Winnik

1998-01-01

21

Protective effect of pretreatment with the calcium antagonist anipamil on the ischemic-reperfused rat myocardium: a phosphorus-31 nuclear magnetic resonance study  

SciTech Connect

To assess whether the prophylactic administration of anipamil, a new calcium antagonist, protects the heart against the effects of ischemia and reperfusion, rats were injected intraperitoneally twice daily for 5 days with 5 mg/kg body weight of this drug. The heart was then isolated and perfused by the Langendorff technique. Phosphorus-31 nuclear magnetic resonance spectroscopy was used to monitor myocardial energy metabolism and intracellular pH during control perfusion and 30 min of total ischemia (37/sup 0/C), followed by 30 min of reperfusion. Pretreatment with anipamil altered neither left ventricular developed pressure under normoxic conditions nor the rate and extent of depletion of adenosine triphosphate (ATP) and creatine phosphate during ischemia. Intracellular acidification, however, was attenuated. On reperfusion, hearts from anipamil-pretreated animals recovered significantly better than untreated hearts with respect to replenishment of ATP and creatine phosphate stores, restitution of low levels of intracellular inorganic phosphate and recovery of left ventricular function and coronary flow. Intracellular pH recovered rapidly to preischemic levels, whereas in untreated hearts a complex intracellular inorganic phosphate peak indicated the existence of areas of different pH within the myocardium. It is concluded that anipamil pretreatment protects the heart against some of the deleterious effects of ischemia and reperfusion. Because this protection occurred in the absence of a negative inotropic effect during normoxia, it cannot be attributed to an energy-sparing effect during ischemia. Therefore, alternative mechanisms of action are to be considered.

Kirkels, J.H.; Ruigrok, T.J.; Van Echteld, C.J.; Meijler, F.L.

1988-05-01

22

Intercalation complex of proflavine with DNA: Structure and dynamics by solid-state NMR  

SciTech Connect

The structure of the complex formed between the intercalating agent proflavine and fibrous native DNA was studied by one- and two-dimensional high-resolution solid-state nuclear magnetic resonance (NMR). Carbon-13-labeled proflavine was used to show that the drug is stacked with the aromatic ring plane perpendicular to the fiber axis and that it is essentially immobile. Natural abundance carbon-13 NMR of the DNA itself shows that proflavine binding does not change the puckering of the deoxyribose ring. However, phosphorus-31 NMR spectra show profound changes in the orientation of the phosphodiester grouping on proflavine binding, with some of the phosphodiesters tilting almost parallel to the helix axis, and a second set almost perpendicular. The first group to the phosphodiesters probably spans the intercalation sites, whereas the tilting of the second set likely compensates for the unwinding of the DNA by the intercalator.

Tang, Pei; Juang, Chilong; Harbison, G.S. (State Univ. of New York, Stony Brook (USA))

1990-07-06

23

NMR Spectroscopy  

NSDL National Science Digital Library

Quiz questions from the organic chemistry question bank provide students with an excellent opportunity to review key concepts. These questions pertain to Nuclear magnetic resonance (NMR) spectroscopy and include topics such as: Chemical Shift, Proton NMR, and Carbon NMR.

Reich, Ieva

2008-03-25

24

Phospholipids chiral at phosphorus. Characterization of the subgel phase of thiophosphatidylcholines by use of X-ray diffraction, Phosphorus-31 nuclear magnetic resonance, and Fourier transform infrared spectroscopy  

SciTech Connect

A recent study using differential scanning calorimetry (DSC) showed that the thermotropic phase behavior of 1,2-dipalmitoyl-sn-glycero-3-thiophosphocholine (DPPsC) is sensitive to the configuration at phosphorus and that the R/sub P/ isomer displayed only a broad transition at 45.6/sup 0/C. The authors have employed x-ray diffraction, /sup 31/P NMR, and Fourier transform infrared (FT-IR) spectroscopy to characterize various phases of the isomers of DPPsC, to compare the structural differences between 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and isomers of DPPsC, and to identify structural factors responsible for the unique behavior of the R/sub P/ isomer. The results from all three techniques support the previous proposal based on DSC studies that (S/sub P/)- and (R/sub P/ + S/sub P/)-DPPsC undergo a subtransition, a pretransition, and a main transition analogous to those of DPPC, while (R/sub P/)-DDPsC is quite stable at the subgel phase and undergoes a direct subgel ..-->.. liquid-crystalline transition at 46/sup 0/C. Quantitative differences between DPPC and DPPsC in the subgel phase have also been observed in the chain spacing, the motional averaging, and the factor group splitting. In particular, DPPsC isomers are motionally rigid and show enhanced factor group splitting in the subgel phase. These results suggest that DPPsC is packed in different subcells relative to DPPC in the subgel phase. Two unique structural features of (R/sub P/)-DPPsC have also been observed in the subgel phase: The bilayer spacing is small,and the C=O stretching band is asymmetric. These features could be responsible for the unusual stability of the subgel phase of (R/sub P/)-DPPsC.

Sarvis, H.E.; Loffredo, W.; Dluhy, R.A.; Hernqvist, L.; Wisner, D.A.; Tsai, M.T.

1988-06-28

25

Lanthanide-cyclodextrin complexes as probes for elucidating optical purity by NMR spectroscopy  

SciTech Connect

A multidentate ligand is bonded to cyclodextrins by the reaction of diethylenetriaminepentaacetic dianhydride with 6-mono- and 2-mono(ethylenediamine) derivatives of cyclodextrin. Adding Dy(III) to the cyclodextrin derivatives enhances the enantiomeric resolution in the [sup 1]H NMR spectra of carbionoxamine maleate, doxylamine succinate, pheniramine maleate, propranolol hydrochloride, and tryptophan. The enhancement is more pronounced with the secondary derivative. The Dy(III)-induced shifts can be used to elucidate the geometry of cyclodextrin-substrate inclusion complexes. Lanthanide-induced shifts are reported for complexes of aspartame, tryptophan, propranolol, and 1-anilino-8-naphthalenesulfonate with cyclodextrins, and the relative magnitudes of the shifts agree with previously reported structures of the complexes. 37 refs., 9 figs., 5 tabs.

Wenzel, T.J.; Bogyo, M.S.; Lebeau, E.L. (Bates College, Lewiston, ME (United States))

1994-06-01

26

NMR Spectroscopy  

NSDL National Science Digital Library

This site contains web-based programs that allow the user to predict chemical shifts, spin-spin coupling patterns and NMR line shapes affected by dynamic chemical exchange. This site will be most useful for students with a good background in the fundamentals of NMR theory.

Shattuck, Thomas W.

2011-07-01

27

Quantitative NMR  

NSDL National Science Digital Library

This site features a learning module focused on principles and practice of NMR for quantitative analysis, an application less commonly associated with the technique than is structure determination. Links to simulation packages are included.

Korir, Albert K.; Larive, Cynthia K.

2011-07-18

28

NMR Animations  

NSDL National Science Digital Library

This site features animated tutorials on NMR with sufficient depth to be useful to the non NMR savvy. The animations are accompanied by short descriptions so that the processes displayed can be understood by the viewer. This site goes beyond just showing precession. There are nice animations showing the effect of different pulses, including composite pulses on the magnetization, the effects of magnetic gradient pulses to measure diffusion and do coherence pathway selection.

2011-07-26

29

Destabilization of cationic lipid vesicles by an anionic hydrophobically modified poly(N-isopropylacrylamide) copolymer: a solid-state 31P NMR and 2H NMR study.  

PubMed

The effect of binding PNIPAM-Py-Gly, a copolymer of N-isopropylacrylamide, N-[4-(1-pyrenyl)butyl]-N-n-octadecylacrylamide and N-glycydyl-acrylamide, on membrane stability in cationic multilamellar vesicles (MLVs) was examined using solid-state phosphorus (31P) and deuterium (2H) nuclear magnetic resonance (NMR) spectroscopy. For MLVs of composition n-octadecyldiethylene oxide (ODEO)+cholesterol (CHOL)+1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)+dimethyldioctadecylammonium bromide (DODAB) (molar ratios 75:10.5:10.5:4), PNIPAM-Py-Gly induced a complete conversion from a bilayer-type 31P NMR spectrum to one characteristic of lipids undergoing isotropic motional averaging, indicating the existence of regions of high local membrane curvature. This response was sustained even at elevated temperatures. For MLVs of composition POPC+1,2-dioleoyloxy-3-(trimethylammonio)-propane (DOTAP), only at high levels of DOTAP and ionic strength did PNIPAM-Py-Gly induce even a partial conversion to an isotropic-type 31P NMR spectrum. At lower pH this effect was diminished. Raising the temperature eliminated the isotropic 31P NMR spectral component, and this effect was not reversible upon returning to room temperature. 2H NMR spectroscopy of headgroup-deuterated DOTAP and POPC confirmed the 31P NMR results, but did not provide specific surface electrostatic information. We conclude that the binding of PNIPAM-Py-Gly to phospholipid-based vesicles is dominated by electrostatic attraction between cationic lipids and the polymer's glycine residues. At high binding levels, the polymer assumes a collapsed conformation at the surface, resulting in regions of high local curvature of the lipid assembly. For ODEO-based liposomes, these effects are magnified by the additional contribution of hydrogen bonding to the strength of polymer binding. PMID:9858737

Franzin, C M; Macdonald, P M; Polozova, A; Winnik, F M

1998-12-01

30

Single-Crystal (31)P NMR and X-ray Diffraction Study of a Molybdenum Phosphine Complex: (5-Methyldibenzophosphole)pentacarbonylmolybdenum(0).  

PubMed

The molecular structure of (5-methyldibenzophosphole)pentacarbonylmolybdenum(0), 1, has been determined by X-ray crystallography. The crystal is monoclinic C2/c, Z = 8, with unit cell dimensions of: a = 31.113(2) Å, b =7.7917(5) Å, c = 17.9522(12) Å, and beta = 122.135(4) degrees. Least-squares refinement converged to R(F) = 0.0245 for 2407 independent reflections. The molecular structure is typical of phosphine-substituted metal carbonyls. It contains an approximate mirror plane which bisects the dibenzophosphole framework. Phosphorus-31 NMR spectra of powder and single-crystal samples of 1 have been obtained with cross-polarization and (1)H high-power decoupling. The (31)P CP/MAS NMR spectra exhibit exceptionally well-resolved satellites due to spin-spin coupling interactions with (95,97)Mo (I = (5)/(2)). Using first-order perturbation theory, the multiplets have been analyzed to yield (1)J((95,97)Mo,(31)P) = 123(2) Hz and estimates of the molybdenum nuclear quadrupolar coupling constants, chi((95)Mo) = -0.87 MHz and chi((97)Mo) = 10.1 MHz. Phosphorus-31 NMR spectra of a large single crystal of 1 have been investigated as a function of orientation about three orthogonal axes in the applied magnetic field. Analysis of the data yields the three principal components of the phosphorus chemical shift tensor, delta(11) = 112 ppm, delta(22) = -23 ppm, and delta(33) = -40 ppm; delta(22) lies close to the Mo-P bond (8 degrees ), while delta(11) lies in the approximate mirror plane. The phosphorus chemical shift tensor determined for 1 is compared with the limited anisotropic phosphorus shift data available in the literature. PMID:11670035

Eichele, Klaus; Wasylishen, Roderick E.; Maitra, Kalyani; Nelson, John H.; Britten, James F.

1997-07-30

31

Lanthanides as NMR probes of fast molecular dynamics at high magnetic fields and temperature sensors: conformational interconversion of erbium ethylenediaminetetraacetate complexes.  

PubMed

(1)H NMR measurements are reported for D2O solutions of paramagnetic complex [Er(H2O)(EDTA(4-))](-) (I) for temperature interval 273-319 K. Diamagnetic complex [Lu(H2O)(EDTA(4-))](-) (II) was used as an NMR reference compound. The spectra obtained have been analyzed using a band-shape analysis technique in the framework of dynamic NMR (DNMR) taking into account the temperature dependence of lanthanide-induced shifts. Intramolecular dynamics in I was assigned to the interconversion of ?-?E-???? and ?-?E-???? conformers with estimated activation free energy ?G(‡)(298 K) = 50 ± 4 kJ/mol. The methodology of paramagnetic 4f-element probe applications on the example of Er(3+) for the study of free-energy changes in chemical exchange processes, as well as the advantages of this method in comparison with DNMR studies of diamagnetic substances, is discussed. In accordance with the literature reviewed, the fulfilled experimental study is the first example of intramolecular dynamics determination for erbium complexes. An additional advantage of the investigation is in the approach proposed which extends the range of measurement of the NMR rate constants for paramagnetic 4f-element complexes compared to diamagnetic ones. Coordination compounds investigated represent a new type of thermometric NMR sensors and lanthanide paramagnetic probes for in situ temperature control in solutions. PMID:23587055

Babailov, Sergey P; Stabnikov, Pavel A; Zapolotsky, Eugeny N; Kokovkin, Vasily V

2013-05-01

32

In vivo sup 31 P-NMR spectroscopy of chronically stimulated canine skeletal muscle  

SciTech Connect

Chronic stimulation converts skeletal muscle of mixed fiber type to a uniform muscle made up of type I, fatigue-resistant fibers. Here, the bioenergetic correlates of fatigue resistance in conditioned canine latissimus dorsi are assessed with in vivo phosphorus-31 nuclear magnetic resonance ({sup 31}P-NMR) spectroscopy. After chronic electrical stimulation, five dogs underwent {sup 31}P-NMR spectroscopic and isometric tension measurements on conditioned and contralateral control muscle during stimulation for 200, 300, 500, and 800 ms of an 1,100-ms duty cycle. With stimulation, phosphocreatine (PCr) fell proportional to the degree of stimulation in both conditioned and control muscle but fell significantly less in conditioned muscle at all the least intense stimulation period (200 ms). Isometric tension, expressed as a tension time index per gram muscle, was significantly greater in the conditioned muscle at the two longest stimulation periods. The overall small change in PCr and the lack of a plateau in tension observed in the conditioned muscle are similar to that seen in cardiac muscle during increased energy demand. This study indicates that the conditioned muscle's markedly enhanced resistance to fatigue is in part the result of its increased capacity for oxidative phosphorylation.

Clark, B.J. III; McCully, A.K.; Subramanian, H.V.; Hammond, R.L.; Salmons, S.; Chance, B.; Stephenson, L.W. (Children's Hospital of Philadelphia, Harrison (USA) Univ. of Pennsylvania School of Medicine, Philadelphia (USA) Univ. of Birmingham (England))

1988-02-01

33

Identification of trapped and boundary lipid binding sites in M13 coat protein/lipid complexes by deuterium NMR spectroscopy  

SciTech Connect

The major coat protein of M13 bacteriophage has been incorporated into bilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine, deuterated in the trimethyl segments of the choline headgroup (DMPC-d9). Two-component deuterium and phosphorus-31 NMR spectra have been observed from bilayer complexes containing the coat protein, indicating slow exchange (on the deuterium quadrupole anisotropy and phosphorus-31 chemical shift averaging time scales) of lipid molecules of less than 10(3) Hz between two motionally distinct environments in the complexes. The fraction of the isotropic spectral component increases with increasing M13 protein concentration, and this component is attributed to lipid headgroups, which are disordered relative to their order in protein-free bilayers. The activation energy of the fast local motions of the trimethyl groups of the choline residue in the headgroup decreases from 23 kJ mol-1 in the pure lipid bilayers to 20 kJ mol-1 for the protein-associated lipid headgroups. The chemical exchange rate of lipid molecules between the two motionally distinct environments has been estimated to be 20-50 Hz by steady-state line-shape simulations of the deuterium spectra of DMPC-d9/M13 coat protein complexes using exchange-coupled modified Bloch equations. The off-rate was, as expected from one-to-one exchange, independent of the L/P ratio; tau off -1 = 0.23 kHz. It is suggested that the protein-associated lipid may be trapped between closely packed parallel aggregates of M13 coat protein and that the high local concentration of protein in a one-dimensional arrangement in lipid bilayers may be required for the fast reassembly of phage particles before release from an infected cell.

Van Gorkom, L.C.; Horvath, L.I.; Hemminga, M.A.; Sternberg, B.; Watts, A. (Univ. of Oxford (England))

1990-04-24

34

Interaction of the Saccharomyces cerevisiae. alpha. -factor with phospholipid vesicles as revealed by proton and phosphorus NMR  

SciTech Connect

Proton and phosphorus-31 nuclear magnetic resonance ({sup 1}H and {sup 31}P NMR) studies of the interaction between a tridecapeptide pheromone, the {alpha}-factor of Saccharomyces cerevisiae, and sonicated lipid vesicles are reported. {sup 31}P NMR studies demonstrate that there is interaction of the peptide with the phosphorus headgroups, and quasielastic light scattering (QLS) studies indicate that lipid vesicles increase in size upon addition of peptide. Previous solution (aqueous and DMSO) studies from this laboratory indicate that {alpha}-factor is highly flexible with only one long-lived identifiable structural feature, a type II {beta}-turn spanning the central portion of the peptide. Two-dimensional (2D) {sup 1}H nuclear Overhauser effect spectroscopy (NOESY) studies demonstrate a marked ordering of the peptide upon interaction with lipid, suggesting a compact N-terminus, in addition to a stabilized {beta}-turn. In contrast to these results in both solution and lipid environment, Wakamatsu et al. proposed a lipid environment conformation, on the basis of one-dimensional transferred NOE studies in D{sub 2}O, which does not include the {beta}-turn.

Jelicks, L.A.; Broido, M.S.; Becker, J.M.; Naider, F.R. (City Univ. of New York, NY (USA))

1989-05-16

35

Fundamentals of NMR  

NSDL National Science Digital Library

This e-text presents an introduction to the fundamentals of NMR covering magnetic resonance, pulsed NMR, relaxation, chemical shift, spin-spin coupling, the nuclear Overhauser effect and chemical exchange. The document may be downloaded in PDF format.

James, Thomas L.

2011-03-30

36

NMR Quantum Information Processing  

Microsoft Academic Search

Nuclear magnetic resonance (NMR) has provided a valuable experimental testbed for quantum information processing (QIP). Here, we briefly review the use of nuclear spins as qubits, and discuss the current status of NMR-QIP. Advances in the techniques available for control are described along with the various implementations of quantum algorithms and quantum simulations that have been performed using NMR. The

Chandrasekhar Ramanathan; Nicolas Boulant; Zhiying Chen; David G. Cory; Isaac Chuang; Matthias Steffen

2004-01-01

37

Basics of NMR  

NSDL National Science Digital Library

Dr. Joseph Hornak of the Rochester Institute of Technology presents this high quality hypertextbook for in-depth coverage of the physics and technique behind Nuclear Magnetic Resonance (NMR) (For Dr. Hornak's Basics of MRI, see the August 4, 1999 Scout Report for Science & Engineering). The material is presented in a detailed and clear manner without over simplifying the concepts. Chapters include "The Mathematics of NMR," "Spin Physics," "NMR Spectroscopy," "Fourier Transforms," "Pulse Sequences," and much more. A chapter on "NMR Hardware" offers an overview of components (like the superconducting magnet and various coils) used in most NMR systems. The "Practical Considerations" chapter emphasizes spectroscopic techniques. With the screen split into two separate frames, explanatory graphics can be viewed alongside the text. A glossary and a list of symbols are also included in this carefully produced textbook.

Hornak, Joseph P.

38

Lanthanide(III) complexes with a tetrapyridine pendant-armed macrocyclic ligand: 1H NMR structural determination in solution, X-ray diffraction, and density-functional theory calculations.  

PubMed

Complexes between the tetrapyridyl pendant-armed macrocyclic ligand (L) and the trivalent lanthanide ions have been synthesized, and structural studies have been made both in the solid state and in aqueous solution. The crystal structures of the La, Ce, Pr, Gd, Tb, Er, and Tm complexes have been determined by single-crystal X-ray crystallography. In the solid state, all the cation complexes show a 10-coordinated geometry close to a distorted bicapped antiprism, with the pyridine pendants situated alternatively above and below the main plane of the macrocycle. The conformations of the two five-membered chelate rings present in the complexes change along the lanthanide series. The La(III) and Ce(III) complexes show a lambdadelta (or deltalambda) conformation, while the complexes of the heavier lanthanide ions present lambdalambda (or deltadelta) conformation. The cationic [Ln(L)]3+ complexes (Ln = La, Pr, Eu, Tb, and Tm) were also characterized by theoretical calculations at the density-functional theory (DFT) B3LYP level. The theoretical calculations predict a stabilization of the lambdalambda (or deltadelta) conformation on decreasing the ionic radius of the Ln(III) ion, in agreement with the experimental evidence. The solution structures show a good agreement with the calculated ones, as demonstrated by paramagnetic NMR measurements (lanthanide induced shifts and relaxation rate enhancements). The 1H NMR spectra indicate an effective D2 symmetry of the complexes in D2O solution. The 1H lanthanide induced shifts (LIS) observed for the Ce(III), Tm(III), and Yb(III) complexes can be fit to a theoretical model assuming that dipolar contributions are dominant for all protons. The resulting calculated values are consistent with highly rhombic magnetic susceptibility tensors with the magnetic axes being coincident with the symmetry axes of the molecule. In contrast with the solid-state structure, the analysis of the LIS data indicates that the Ce(III) complexes present a lambdalambda (or deltadelta) conformation in solution. PMID:16711699

Del C Fernandez-Fernandez, M; Bastida, R; Macías, A; Pérez-Lourido, P; Platas-Iglesias, C; Valencia, L

2006-05-29

39

Catalytic mechanism of ?-phosphate attack in dUTPase is revealed by X-ray crystallographic snapshots of distinct intermediates, 31P-NMR spectroscopy and reaction path modelling  

PubMed Central

Enzymatic synthesis and hydrolysis of nucleoside phosphate compounds play a key role in various biological pathways, like signal transduction, DNA synthesis and metabolism. Although these processes have been studied extensively, numerous key issues regarding the chemical pathway and atomic movements remain open for many enzymatic reactions. Here, using the Mason–Pfizer monkey retrovirus dUTPase, we study the dUTPase-catalyzed hydrolysis of dUTP, an incorrect DNA building block, to elaborate the mechanistic details at high resolution. Combining mass spectrometry analysis of the dUTPase-catalyzed reaction carried out in and quantum mechanics/molecular mechanics (QM/MM) simulation, we show that the nucleophilic attack occurs at the ?-phosphate site. Phosphorus-31 NMR spectroscopy (31P-NMR) analysis confirms the site of attack and shows the capability of dUTPase to cleave the dUTP analogue ?,?-imido-dUTP, containing the imido linkage usually regarded to be non-hydrolyzable. We present numerous X-ray crystal structures of distinct dUTPase and nucleoside phosphate complexes, which report on the progress of the chemical reaction along the reaction coordinate. The presently used combination of diverse structural methods reveals details of the nucleophilic attack and identifies a novel enzyme–product complex structure.

Barabas, Orsolya; Nemeth, Veronika; Bodor, Andrea; Perczel, Andras; Rosta, Edina; Kele, Zoltan; Zagyva, Imre; Szabadka, Zoltan; Grolmusz, Vince I.; Wilmanns, Matthias; Vertessy, Beata G.

2013-01-01

40

NMR imaging microscopy  

SciTech Connect

In the past several years, proton nuclear magnetic resonance (NMR) imaging has become an established technique in diagnostic medicine and biomedical research. Although much of the work in this field has been directed toward development of whole-body imagers, James Aguayo, Stephen Blackband, and Joseph Schoeninger of the Johns Hopkins University School of Medicine working with Markus Hintermann and Mark Mattingly of Bruker Medical Instruments, recently developed a small-bore NMR microscope with sufficient resolution to image a single African clawed toad cell (Nature 1986, 322, 190-91). This improved resolution should lead to increased use of NMR imaging for chemical, as well as biological or physiological, applications. The future of NMR microscopy, like that of many other newly emerging techniques, is ripe with possibilities. Because of its high cost, however, it is likely to remain primarily a research tool for some time. ''It's like having a camera,'' says Smith. ''You've got a way to look at things at very fine levels, and people are going to find lots of uses for it. But it is a very expensive technique - it costs $100,000 to add imaging capability once you have a high-resolution NMR, which itself is at least a $300,000 instrument. If it can answer even a few questions that can't be answered any other way, though, it may be well worth the cost.''

Not Available

1986-10-01

41

Practical NMR imaging  

SciTech Connect

This book contains the following chapters: General principles; Siting and installation of x-ray equipment; Practical testing; The image slice; NMR in clinical practice; Development of tissue contrast in magnetic resonance imaging; The clinical use of contrast agents in magnetic resonance imaging; Advanced imaging techniques; In vivo spectroscopy; and Safety considerations.

Foster, M.A.; Hutchison, J.M.S.

1987-01-01

42

Modern NMR Spectroscopy.  

ERIC Educational Resources Information Center

Discusses direct chemical information that can be obtained from modern nuclear magnetic resonance (NMR) methods, concentrating on the types of problems that can be solved. Shows how selected methods provide information about polymers, bipolymers, biochemistry, small organic molecules, inorganic compounds, and compounds oriented in a magnetic…

Jelinski, Lynn W.

1984-01-01

43

Educational NMR Software  

NASA Astrophysics Data System (ADS)

A description of a compilation of computer programs (EduNMRSoft) suitable for teaching NMR at an introductory to advanced level is presented. Each program is categorised and described by function, hardware requirements, availability, author, and references in the list. The compilation is available in electronic form at http://www.chem.umu.se/divisions/fk/EduNMRSoft.html.

Lundberg, Peter

1997-12-01

44

NMR magnet technology at MIT  

SciTech Connect

The design and construction of high field superconducting NMR magnets has much in common with other types of adiabatic superconducting magnets. However, two issues have a particular relevance to NMR magnets. They are field drift and homogeneity. In this paper the control of these factors in the particular context of high field NMR spectrometer magnets is examined.

Williams, J.E.C.; Bobrov, E.S.; Iwasa, Y.; Punchard, W.F.B.; Wrenn, J.; Zhukovsky, A. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Francis Bitter National Magnet Lab.)

1992-01-01

45

NMR Characterization of Mechanical Waves  

Microsoft Academic Search

NMR characterization of biological tissues or materials (MR elastography) is a challenging and promising area of research. A review of ongoing progress in acoustic wave detection and characterization using NMR is given. After recalling some basic physical principles of acoustics (strain–stress relationship, viscoelasticity), NMR methods for shear or longitudinal wave detection are described, emphasizing pioneer works. Both spectroscopic and imaging

GUILLAUME MADELIN; NATHALIE BARIL; JACQUES DONALD DE CERTAINES; JEAN-MICHEL FRANCONI; ERIC THIAUDIÈRE

2004-01-01

46

The NMR phased array.  

PubMed

We describe methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils. The approach is conceptually similar to phased array radar and ultrasound and hence we call our techniques the "NMR phased array." The NMR phased array offers the signal-to-noise ratio (SNR) and resolution of a small surface coil over fields-of-view (FOV) normally associated with body imaging with no increase in imaging time. The NMR phased array can be applied to both imaging and spectroscopy for all pulse sequences. The problematic interactions among nearby surface coils is eliminated (a) by overlapping adjacent coils to give zero mutual inductance, hence zero interaction, and (b) by attaching low input impedance preamplifiers to all coils, thus eliminating interference among next nearest and more distant neighbors. We derive an algorithm for combining the data from the phased array elements to yield an image with optimum SNR. Other techniques which are easier to implement at the cost of lower SNR are explored. Phased array imaging is demonstrated with high resolution (512 x 512, 48-cm FOV, and 32-cm FOV) spin-echo images of the thoracic and lumbar spine. Data were acquired from four-element linear spine arrays, the first made of 12-cm square coils and the second made of 8-cm square coils. When compared with images from a single 15 x 30-cm rectangular coil and identical imaging parameters, the phased array yields a 2X and 3X higher SNR at the depth of the spine (approximately 7 cm). PMID:2266841

Roemer, P B; Edelstein, W A; Hayes, C E; Souza, S P; Mueller, O M

1990-11-01

47

NMR Studies of Peroxidases.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. Peroxidases are a haem-containing group of enzymes with a wide diversity of function within biological systems. While a common characteristic is the ability to catalyse the conversion of hydrogen peroxide to water, it is the accompanying processes of hormone synthesis and degradation which have generated such a high level of interest. However, information at the molecular level is limited to a single well-resolved crystal structure, that of yeast cytochrome c peroxidase. This thesis presents a strategy for the investigation of peroxidase structure and function based on proton nuclear magnetic resonance spectroscopy, a technique which has the ability to address aspects of both protein structure and protein dynamics in solution. The application of one- and two-dimensional NMR techniques has been developed in the context of plant peroxidases, notably the isoenzyme HRP-C derived from the horseradish root. Characterisation of the proton NMR spectra of HRP -C in resting and ligated states provided new information enabling the structure of the binding site for aromatic donor molecules, such as indole-3-propionic, ferulic and benzhydroxamic acids, to be resolved. In order to overcome difficulties encountered with a protein of the complexity of peroxidase, additional information was obtained from chemical shift parameters and the use of peroxidase variants produced by site-directed mutagenesis. A comparative study using NMR spectroscopy was undertaken for wild-type recombinant HRP-C expressed in Escherichia coli, and two protein variants with substitutions made to residues located on the distal side of the haem pocket, Phe41 to Val and Arg38 to Lys. NMR analyses of a plant peroxidase from barley grains and the fungal peroxidase from Coprinus cinereus were also successful using methods conceived with HRP-C. Examination of three specifically constructed recombinant protein variants of C. cinereus peroxidase was essential in confirming the identity of residues participating in the aromatic donor molecule binding site of peroxidases.

Veitch, Nigel Charles

48

Flow NMR applications in combinatorial chemistry  

Microsoft Academic Search

Flow NMR techniques are now well accepted and widely used in many areas of drug discovery. Although natural-product-, rational-drug-design-, and NMR-screening-programs have begun to use flow NMR more routinely, flow NMR has not yet gained widespread acceptance in combinatorial chemistry, even though it has been shown to be a potentially useful tool. Recent developments in DI-NMR, FIA-NMR, and LC-NMR will

Paul A Keifer

2003-01-01

49

Assessment of glucosylifosfamide mustard biodistribution in rats with prostate adenocarcinomas by means of in vivo 31P NMR and in vitro uptake experiments.  

PubMed

A combined in vitro/in vivo study was performed to evaluate the possible application of phosphorus (31P) NMR spectroscopy for therapy monitoring and to investigate glucosylifosfamide mustard (Glc-IPM) transport and biodistribution by radiotracer techniques. Dynamic in vivo 31P NMR measurements were performed in rats with prostate adenocarcinoma after i.v. injection of 1 mmol/kg body weight (bw) of ifosfamide (IFO) (n = 4) and 1 mmol/kg bw (n = 4) or 2.15 mmol/kg bw (n = 9) of Glc-IPM. In a biodistribution study with 14C-labeled Glc-IPM and a final dose of 0.8 mmol Glc-IPM/kg bw, the animals were killed 5, 30, 60, and 120 min after drug administration, an ethanol extraction was performed from several tissues, and the dose per g tissue was calculated. The same tumor cell line was used in saturation and competition experiments to further elucidate the transport mechanism. The 31P NMR signals of IFO and Glc-IPM showed no overlap with the endogenous phosphorus peaks. A rapid washout with a half-life between 25.9 +/- 5.6 min for the lower dose and 34.3 +/- 4.2 min for the higher dose of Glc-IPM was observed in the tumor. No statistically significant change of the pH value was observed during the examination period. The beta-nucleoside 5'-triphosphate (NTP)/inorganic phosphate (Pi) signal intensity ratio showed a tendency to decrease but without statistical significance. A rapid elimination was demonstrated by both the noninvasive NMR technique and the biodistribution study. No saturation was found in vitro for the Glc-IPM uptake, even at the concentration of 5 mM. Furthermore, the Glc-IPM uptake was not inhibited by the presence of 2-deoxyglucose and vice versa. The data show that the pharmacokinetics of Glc-IPM in the tumor can be followed in vivo by 31P NMR. The results presented are evidence for diffusion as the transport mechanism for Glc-IPM in this tumor model. However, the better visualization of Glc-IPM as compared to ifosfamide may be due to metabolic trapping of a negatively charged metabolite after deglycosylation. PMID:9581607

Haberkorn, U; Krems, B; Gerlach, L; Bachert, P; Morr, I; Wiessler, M; van Kaick, G

1998-05-01

50

Rheo NMR and shear banding  

Microsoft Academic Search

The phenomenon of shear banding in complex fluids has been investigated using NMR velocimetry and NMR spectroscopy, mostly\\u000a in wormlike micelle systems, but more recently in colloidal systems and multilayer vesicles. A particular advantage of NMR\\u000a is the ability to simultaneously investigate structural ordering and to compare such ordering with local strain rates. In\\u000a this paper, we describe the basics

Paul T. Callaghan

2008-01-01

51

Hepatic lipid profiling of deer mice fed ethanol using 1H and 31P NMR spectroscopy: A dose-dependent subchronic study  

PubMed Central

Chronic alcohol abuse is a 2nd major cause of liver disease resulting in significant morbidity and mortality. Alcoholic liver disease (ALD) is characterized by a wide spectrum of pathologies starting from fat accumulation (steatosis) in early reversible stage to inflammation with or without fibrosis and cirrhosis in later irreversible stages. Previously, we reported significant steatosis in the livers of hepatic alcohol dehydrogenase (ADH)-deficient (ADH?) vs. hepatic ADH-normal (ADH+) deer mice fed 4% ethanol daily for 2 months [Bhopale et al., 2006, Alcohol 39, 179–188]. However, ADH? deer mice fed 4% ethanol also showed a significant mortality. Therefore, a dose-dependent study was conducted to understand the mechanism and identify lipid(s) involved in the development of ethanol-induced fatty liver. ADH? and ADH+ deer mice fed 1, 2 or 3.5% ethanol daily for 2 months and fatty infiltration in the livers were evaluated by histology and by measuring dry weights of extracted lipids. Lipid metabolomic changes in extracted lipids were determined by proton (1H) and 31phosphorus (31P) nuclear magnetic resonance (NMR) spectroscopy. The NMR data was analyzed by hierarchical clustering (HC) and principle component analyses (PCA) for pattern recognition. Extensive vacuolization by histology and significantly increased dry weights of total lipids found only in the livers of ADH? deer mice fed 3.5% ethanol vs. pair-fed controls suggest a dose-dependent formation of fatty liver in ADH? deer mouse model. Analysis of NMR data of ADH? deer mice fed 3.5% ethanol vs. pair-fed controls shows increases for total cholesterol, esterified cholesterol, fatty acid methyl esters (FAMEs), triacylglycerides and unsaturation, and decreases for free cholesterol, phospholipids and allylic and diallylic protons. Certain classes of neutral lipids (cholesterol esters, fatty acyl chain (-COCH2-) and FAMEs) were also mildly increased in ADH? deer mice fed 1 or 2% ethanol. Only small increases were observed for allylic and diallylic protons, FAMEs and unsaturations in ADH+ deer mice fed 3.5% ethanol vs. pair-fed controls. PCA of NMR data showed increased clustering by gradual separation of ethanol-fed ADH? deer mice groups from their respective pair-fed control groups and corresponding ethanol-fed ADH+ deer mice groups. Our data indicate that dose of ethanol and hepatic ADH deficiency are two key factors involved in initiation and progression of alcoholic fatty liver disease. Further studies on characterization of individual lipid entities and associated metabolic pathways altered in our deer mouse model after different durations of ethanol feeding could be important to delineate mechanism(s) and identify potential biomarker candidate(s) of early stage ALD.

Fernando, Harshica; Bhopale, Kamlesh K.; Boor, Paul J.; Shakeel Ansari, G. A.; Kaphalia, Bhupendra S.

2012-01-01

52

Flow NMR applications in combinatorial chemistry.  

PubMed

Flow NMR techniques are now well accepted and widely used in many areas of drug discovery. Although natural-product-, rational-drug-design-, and NMR-screening-programs have begun to use flow NMR more routinely, flow NMR has not yet gained widespread acceptance in combinatorial chemistry, even though it has been shown to be a potentially useful tool. Recent developments in DI-NMR, FIA-NMR, and LC-NMR will help flow NMR eventually gain a wider acceptance within combinatorial chemistry. These developments include LC-NMR-MS instrumentation, flow probe improvements, new pulse sequences, improved automation of NMR data analysis, and the application of flow NMR to related fields in drug discovery. PMID:12826127

Keifer, Paul A

2003-06-01

53

NMR measurement of pore structure  

SciTech Connect

An attempt was made to pursue {sup 129}Xe NMR as a pore measurement technique. Samples studied were synthetic imogolite (tubular aluminosilicate with gibbsite structure), sodium Y-zeolite, and an aerogel and a xerogel. Gases used were normal Xe, {sup 13}CO{sub 2}, and {sup 15}N{sub 2}. Although a completely general NMR technique for measuring pore size distributions may not be possible, information about molecular motion and interactions can be obtained, because NMR is sensitive to short range interactions (1 nm or less) and to molecular dynamics in the range 10{sup {minus}2} to 10{sup {minus}6}s.

Earl, W.L. [Los Alamos National Lab., NM (United States); Kim, Yong-Wah [Los Alamos National Lab., NM (United States)]|[New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics; Smith, D.M. [New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics

1993-05-31

54

NMR measurement of pore structure  

SciTech Connect

An attempt was made to pursue [sup 129]Xe NMR as a pore measurement technique. Samples studied were synthetic imogolite (tubular aluminosilicate with gibbsite structure), sodium Y-zeolite, and an aerogel and a xerogel. Gases used were normal Xe, [sup 13]CO[sub 2], and [sup 15]N[sub 2]. Although a completely general NMR technique for measuring pore size distributions may not be possible, information about molecular motion and interactions can be obtained, because NMR is sensitive to short range interactions (1 nm or less) and to molecular dynamics in the range 10[sup [minus]2] to 10[sup [minus]6]s.

Earl, W.L. (Los Alamos National Lab., NM (United States)); Kim, Yong-Wah (Los Alamos National Lab., NM (United States) New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics); Smith, D.M. (New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics)

1993-05-31

55

Nuclear magnetic resonance (NMR) blood flow imaging  

Microsoft Academic Search

Picture element values in NMR images are dependent not only upon T⁠and Tâ relaxation times but also on the local density and velocity of hydrogen nuclei moving through the region being imaged. In 1959 the potential of non-imaging NMR for measuring blood flow was demonstrated. Recently several investigators have proposed methods for combining NMR imaging with NMR blood flow

R. R. Price; J. A. Patton; M. D. Kulkarni; D. R. Pickens; J. J. Erickson; W. H. Stephens; C. L. Partain; A. E. Jr. James

1984-01-01

56

NMR-Tomographie des menschlichen Auges  

Microsoft Academic Search

The NMR relaxation data of tissue are the basis of an appropriate adjustment of NMR imaging parameters. The relaxation data of ocular tissues are presented, and the relaxation behaviour of the eye is discussed. NMR imaging of eyes with intraocular silicone and pseudophakia are shown. Up to the present time, neuritis of the optic nerve is not detectable by NMR

T. Seiler; J. Wollensak; V. Miszalok

1986-01-01

57

Compact orthogonal NMR field sensor  

DOEpatents

A Compact Orthogonal Field Sensor for emitting two orthogonal electro-magnetic fields in a common space. More particularly, a replacement inductor for existing NMR (Nuclear Magnetic Resonance) sensors to allow for NMR imaging. The Compact Orthogonal Field Sensor has a conductive coil and a central conductor electrically connected in series. The central conductor is at least partially surrounded by the coil. The coil and central conductor are electrically or electro-magnetically connected to a device having a means for producing or inducing a current through the coil and central conductor. The Compact Orthogonal Field Sensor can be used in NMR imaging applications to determine the position and the associated NMR spectrum of a sample within the electro-magnetic field of the central conductor.

Gerald, II, Rex E. (Brookfield, IL); Rathke, Jerome W. (Homer Glen, IL)

2009-02-03

58

NMR characterization of thin films  

DOEpatents

A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

Gerald, II, Rex E. (Brookfield, IL); Klingler, Robert J. (Glenview, IL); Rathke, Jerome W. (Homer Glen, IL); Diaz, Rocio (Chicago, IL); Vukovic, Lela (Westchester, IL)

2008-11-25

59

Multispectral Analysis of NMR Imagery  

NASA Technical Reports Server (NTRS)

Conference paper discusses initial efforts to adapt multispectral satellite-image analysis to nuclear magnetic resonance (NMR) scans of human body. Flexibility of these techniques makes it possible to present NMR data in variety of formats, including pseudocolor composite images of pathological internal features. Techniques do not have to be greatly modified from form in which used to produce satellite maps of such Earth features as water, rock, or foliage.

Butterfield, R. L.; Vannier, M. W. And Associates; Jordan, D.

1985-01-01

60

NMR insights into protein allostery  

PubMed Central

Allosterism is one of nature's principal methods for regulating protein function. Allosterism utilizes ligand binding at one site to regulate the function of the protein by modulating the structure and dynamics of a distant binding site. In this review, we first survey solution NMR techniques and how they may be applied to the study of allostery. Subsequently, we describe several examples of application of NMR to protein allostery and highlight the unique insight provided by this experimental technique.

Manley, Gregory; Loria, J. Patrick

2014-01-01

61

Optical pumping and xenon NMR  

SciTech Connect

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping [sup 129]Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the [sup 131]Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

Raftery, M.D.

1991-11-01

62

Optical pumping and xenon NMR  

SciTech Connect

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping {sup 129}Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the {sup 131}Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

Raftery, M.D.

1991-11-01

63

Advanced NMR characterization of zeolite catalysts  

NASA Astrophysics Data System (ADS)

The program discussed in this report is a two-year two-phase joint UOP-University of Illinois study of the application of improved high resolution solid state nuclear magnetic resonance (NMR) techniques to the characterization of zeolite catalysts. During the first phase of this program very pure, and in some cases isotopically enriched faujasites will be prepared and studied by magic angle sample spinning NMR (MASS NMR) and variable engine sample spinning NMR (VASS NMR) on 500 and 360 MHz (proton frequency) NMR spectrometers. The NMR techniques that will be emphasized are the measurement and analysis of the (17)O NMR properties, (27)Al NMR intensity quantitation, and (27)Al and (29)Si NMR relaxation rates. During the second phase of this program these NMR techniques will be used to study the effects of impurity concentration, dealumination treatments and cation exchange on the NMR properties of faujasites. The initial emphasis of this program during Phase I is on the preparation and measurement of the NMR properties of (17)O enriched Na-Y faujasties.

Welsh, L. B.

1985-04-01

64

A SENSITIVE NMR THERMOMETER FOR MULTINUCLEI FT NMR  

EPA Science Inventory

A pernicious problem in multinuclei FT NMR is accurate measurement of sample temperature. This arises from several factors including widespread use of high-power decoupling, large sample tubes (with potentially large temperature gradients across the sample volume), and lack of su...

65

"Solvent Effects" in 1H NMR Spectroscopy.  

ERIC Educational Resources Information Center

Describes a simple undergraduate experiment in chemistry dealing with the "solvent effects" in nuclear magnetic resonance (NMR) spectroscopy. Stresses the importance of having students learn NMR spectroscopy as a tool in analytical chemistry. (TW)

Cavaleiro, Jose A. S.

1987-01-01

66

Complete NMR assignments of tubulosine.  

PubMed

This article reports the structural elucidation of the Alangium alkaloid, tubulosine (1) on the basis of systematic 2D-NMR analyses (DEPT, COSY, TOCSY, NOESY, ROESY, HMQC and HMBC). The data obtained allowed the unambiguous assignment of all proton and carbon signals in 1 for the first time. PMID:22428233

Kantamreddia, Venkata Siva Satyanarayana; Wright, Colin W

2012-01-01

67

Computer Simulation of NMR Spectra.  

ERIC Educational Resources Information Center

Describes a PASCAL computer program which provides interactive analysis and display of high-resolution nuclear magnetic resonance (NMR) spectra from spin one-half nuclei using a hard-copy or monitor. Includes general and theoretical program descriptions, program capability, and examples of its use. (Source for program/documentation is included.)…

Ellison, A.

1983-01-01

68

NMR properties of alginate microbeads  

Microsoft Academic Search

Alginates are a family of unbranched polysaccharides with properties that vary widely depending on their composition. In the presence of multivalent cations (frequently Ca2+), alginates form a gel. Consequently, alginates have been used to encapsulate a variety of biological materials, including cells. In this study, we present NMR relaxation and diffusion data from alginate microbeads with similar size and properties

Nicholas E. Simpson; Samuel C. Grant; Stephen J. Blackband; Ioannis Constantinidis

2003-01-01

69

Deuterium Exchange Kinetics by NMR.  

ERIC Educational Resources Information Center

Describes a physical chemistry experiment which allows such concepts as kinetics, catalysis, isotope shifts, coupling constants, and the use of nuclear magnetic resonance (NMR) for quantitative work to be covered in the same exercise. Background information, experimental procedures used, and typical results obtained are included. (JN)

Roper, G. C.

1985-01-01

70

QUANTITATIVE 15N NMR SPECTROSCOPY  

EPA Science Inventory

Line intensities in 15N NMR spectra are strongly influenced by spin-lattice and spin-spin relaxation times, relaxation mechanisms and experimental conditions. Special care has to be taken in using 15N spectra for quantitative purposes. Quantitative aspects are discussed for the 1...

71

Ultrahigh-resolution NMR spectroscopy.  

PubMed

All psyched up: A flexible and general pure shift experiment (PSYCHE) has been developed that offers superior sensitivity, spectral purity, and tolerance of strong coupling over existing methods for broadband homonuclear decoupling. The partial spectra of estradiol in [D6 ]DMSO obtained by normal (1) H?NMR spectroscopy and PSYCHE are shown for comparison. PMID:24861024

Foroozandeh, Mohammadali; Adams, Ralph W; Meharry, Nicola J; Jeannerat, Damien; Nilsson, Mathias; Morris, Gareth A

2014-07-01

72

Contact replacement for NMR resonance assignment  

Microsoft Academic Search

Motivation: Complementing its traditional role in structural studies of proteins, nuclear magnetic resonance (NMR) spectroscopy is playing an increasingly important role in functional studies. NMR dynamics experiments characterize motions involved in target recognition, ligand binding, etc., while NMR chemical shift perturbation experiments identify and localize protein-protein and protein-ligand interactions. The key bottleneck in these studies is to determine the backbone

Fei Xiong; Gopal Pandurangan; Chris Bailey-kellogg

2008-01-01

73

Contact Replacement for NMR Resonance Assignment  

Microsoft Academic Search

Motivation: Complementing its traditional role in structural studies of proteins, nuclear magnetic resonance (NMR) spectroscopy is playing an increasingly important role in functional studies. NMR dynamics experiments characterize motions involved in target reco- gnition, ligand binding, etc., while NMR chemical shift perturbation experiments identify and localize protein-protein and protein-ligand interactions. The key bottleneck in these studies is to determine the

Fei Xiong; Gopal Pandurangan; Chris Bailey-Kellogg

74

Quality Assessment of Horticultural Products by NMR  

Microsoft Academic Search

The potential for developing NMR as an on-line sensor of the internal quality of fruits and vegetables is discussed. The literature on the NMR of horticultural products is first surveyed for potentially useful correlations between NMR characteristics and internal quality factors in commercially important harvested products. This is followed by discussions on the cellular origins of these correlations and of

B. P HILLS; C. J CLARK

2003-01-01

75

Applications of NMR to food science  

Microsoft Academic Search

This report reviews the literature on the applications of NMR to food science from 1995 until March 2001. In order to be able to keep the number of references to manageable proportions, the number of papers referred to has been limited to those applications where NMR plays a major role in the experimental programme. Applications where NMR is simply used

E Alberti; P. S Belton; A. M Gil

2002-01-01

76

LC–NMR–MS in drug discovery  

Microsoft Academic Search

Nuclear magnetic resonance spectroscopy (NMR) is arguably the most versatile analytical platform for complex mixture analysis. Specifically, interfacing liquid chromatography with parallel NMR and mass spectrometry (LC–NMR–MS) gives comprehensive structural data on metabolites of novel drugs in development. Applications in natural product, combinatorial chemistry and drug metabolism studies are reviewed. Microcoil probes and capillary separation methods have enormous potential. Recent

Olivia Corcoran; Manfred Spraul

2003-01-01

77

Two dimensional NMR and NMR relaxation studies of coal structure  

SciTech Connect

This report covers the progress made on the title project for the project period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups that determine the reactivity of coals. Special attention is being paid to methods that are compatible with the very high magic angle sample spinning rates needed for operation at the high magnetic field strengths available today. Polarization inversion methods utilizing the difference in heat capacities of small groups of spins are particularly promising. Methods combining proton-proton spin diffusion with [sup 13]C CPMAS readout are being developed to determine the connectivity of functional groups in coals in a high sensitivity relay type of experiment. Additional work is aimed at delineating the role of methyl group rotation in the proton NMR relaxation behavior of coals.

Zilm, K.W.

1992-11-25

78

SEnD NMR: Sensitivity Enhanced n-Dimensional NMR  

PubMed Central

Sparse sampling offers tremendous potential for overcoming the time limitations imposed by traditional Cartesian sampling of indirectly detected dimensions of multidimensional NMR data. However, in many instances sensitivity rather than time remains of foremost importance when collecting data on protein samples. Here we explore how to optimize the collection of radial sampled multidimensional NMR data to achieve maximal signal-to-noise. A method is presented that exploits a rigorous definition of the minimal set of radial sampling angles required to resolve all peaks of interest in combination with a fundamental statistical property of radial sampled data. The approach appears general and can achieve a substantial sensitivity advantage over Cartesian sampling for the same total data acquisition time. Termed Sensitivity Enhanced n-Dimensional or SEnD NMR, the method involves three basic steps. First, data collection is optimized using routines to determine a minimal set of radial sampling angles required to resolve frequencies in the radially sampled chemical shift evolution dimensions. Second, appropriate combinations of experimental parameters (transients and increments) are defined by simple statistical considerations in order to optimize signal-to-noise in single angle frequency domain spectra. Finally, the data is processed with a direct multidimensional Fourier transform and a statistical artifact and noise removal step is employed.

Gledhill, John M.; Wand, A. Joshua

2009-01-01

79

REDOR NMR for Drug Discovery  

PubMed Central

Rotational-Echo DOuble-Resonance (REDOR) NMR is a powerful and versatile solid-state NMR measurement that has been recruited to elucidate drug modes of action and to drive the design of new therapeutics. REDOR has been implemented to examine composition, structure, and dynamics in diverse macromolecular and whole-cell systems, including taxol-bound microtubules, enzyme-cofactor-inhibitor ternary complexes, and antibiotic-whole-cell complexes. The REDOR approach involves the integrated design of specific isotopic labeling strategies and the selection of appropriate REDOR experiments. By way of example, this digest illustrates the versatility of the REDOR approach, with an emphasis on the practical considerations of experimental design and data interpretation.

Cegelski, Lynette

2014-01-01

80

NMR investigation of Ag nanoparticles  

NASA Astrophysics Data System (ADS)

109Ag nuclear magnetic resonance (NMR) and relaxation measurements have been performed on two powder samples of Ag nanoparticles with average sizes of 20 nm and 80 nm. The measurements have been done in an external field of 9.4 T and in the temperature range 10 K < T < 280 K. The 109Ag NMR spectra for both samples have close to Lorentzian shapes and turn out to be mixtures of homogeneous and inhomogeneous lines. The linewidth ? ? at room temperature is 1.3 kHz for both samples and gradually increases with decreasing temperature. Both the Knight shift ( K) and the nuclear spin-lattice relaxation rate (1/ T 1) are observed to be almost identical to the values reported for the bulk Ag metal, whereby the Korringa ratio R(= K 2 T 1 T/S) is found to be 2.0 for both samples in the investigated temperature range.

Son, Kwanghyo; Jang, Zeehoon

2013-01-01

81

REDOR NMR for drug discovery.  

PubMed

Rotational-echo double-resonance (REDOR) NMR is a powerful and versatile solid-state NMR measurement that has been recruited to elucidate drug modes of action and to drive the design of new therapeutics. REDOR has been implemented to examine composition, structure, and dynamics in diverse macromolecular and whole-cell systems, including taxol-bound microtubules, enzyme-cofactor-inhibitor ternary complexes, and antibiotic-whole-cell complexes. The REDOR approach involves the integrated design of specific isotopic labeling strategies and the selection of appropriate REDOR experiments. By way of example, this digest illustrates the versatility of the REDOR approach, with an emphasis on the practical considerations of experimental design and data interpretation. PMID:24035486

Cegelski, Lynette

2013-11-01

82

NMR-Based Milk Metabolomics  

PubMed Central

Milk is a key component in infant nutrition worldwide and, in the Western parts of the world, also in adult nutrition. Milk of bovine origin is both consumed fresh and processed into a variety of dairy products including cheese, fermented milk products, and infant formula. The nutritional quality and processing capabilities of bovine milk is closely associated to milk composition. Metabolomics is ideal in the study of the low-molecular-weight compounds in milk, and this review focuses on the recent nuclear magnetic resonance (NMR)-based metabolomics trends in milk research, including applications linking the milk metabolite profiling with nutritional aspects, and applications which aim to link the milk metabolite profile to various technological qualities of milk. The metabolite profiling studies encompass the identification of novel metabolites, which potentially can be used as biomarkers or as bioactive compounds. Furthermore, metabolomics applications elucidating how the differential regulated genes affects milk composition are also reported. This review will highlight the recent advances in NMR-based metabolomics on milk, as well as give a brief summary of when NMR spectroscopy can be useful for gaining a better understanding of how milk composition is linked to nutritional or quality traits.

Sundekilde, Ulrik K.; Larsen, Lotte B.; Bertram, Hanne C.

2013-01-01

83

NMR-Based Milk Metabolomics.  

PubMed

Milk is a key component in infant nutrition worldwide and, in the Western parts of the world, also in adult nutrition. Milk of bovine origin is both consumed fresh and processed into a variety of dairy products including cheese, fermented milk products, and infant formula. The nutritional quality and processing capabilities of bovine milk is closely associated to milk composition. Metabolomics is ideal in the study of the low-molecular-weight compounds in milk, and this review focuses on the recent nuclear magnetic resonance (NMR)-based metabolomics trends in milk research, including applications linking the milk metabolite profiling with nutritional aspects, and applications which aim to link the milk metabolite profile to various technological qualities of milk. The metabolite profiling studies encompass the identification of novel metabolites, which potentially can be used as biomarkers or as bioactive compounds. Furthermore, metabolomics applications elucidating how the differential regulated genes affects milk composition are also reported. This review will highlight the recent advances in NMR-based metabolomics on milk, as well as give a brief summary of when NMR spectroscopy can be useful for gaining a better understanding of how milk composition is linked to nutritional or quality traits. PMID:24957988

Sundekilde, Ulrik K; Larsen, Lotte B; Bertram, Hanne C

2013-01-01

84

Hyperpolarized (131)Xe NMR spectroscopy.  

PubMed

Hyperpolarized (hp) (131)Xe with up to 2.2% spin polarization (i.e., 5000-fold signal enhancement at 9.4 T) was obtained after separation from the rubidium vapor of the spin-exchange optical pumping (SEOP) process. The SEOP was applied for several minutes in a stopped-flow mode, and the fast, quadrupolar-driven T(1) relaxation of this spin I = 3/2 noble gas isotope required a rapid subsequent rubidium removal and swift transfer into the high magnetic field region for NMR detection. Because of the xenon density dependent (131)Xe quadrupolar relaxation in the gas phase, the SEOP polarization build-up exhibits an even more pronounced dependence on xenon partial pressure than that observed in (129)Xe SEOP. (131)Xe is the only stable noble gas isotope with a positive gyromagnetic ratio and shows therefore a different relative phase between hp signal and thermal signal compared to all other noble gases. The gas phase (131)Xe NMR spectrum displays a surface and magnetic field dependent quadrupolar splitting that was found to have additional gas pressure and gas composition dependence. The splitting was reduced by the presence of water vapor that presumably influences xenon-surface interactions. The hp (131)Xe spectrum shows differential line broadening, suggesting the presence of strong adsorption sites. Beyond hp (131)Xe NMR spectroscopy studies, a general equation for the high temperature, thermal spin polarization, P, for spin I ? 1/2 nuclei is presented. PMID:21051249

Stupic, Karl F; Cleveland, Zackary I; Pavlovskaya, Galina E; Meersmann, Thomas

2011-01-01

85

Hyperpolarized 131Xe NMR spectroscopy  

PubMed Central

Hyperpolarized (hp) 131Xe with up to 2.2% spin polarization (i.e., 5000-fold signal enhancement at 9.4 T) was obtained after separation from the rubidium vapor of the spin-exchange optical pumping (SEOP) process. The SEOP was applied for several minutes in a stopped-flow mode, and the fast, quadrupolar-driven T1 relaxation of this spin I = 3/2 noble gas isotope required a rapid subsequent rubidium removal and swift transfer into the high magnetic field region for NMR detection. Because of the xenon density dependent 131Xe quadrupolar relaxation in the gas phase, the SEOP polarization build-up exhibits an even more pronounced dependence on xenon partial pressure than that observed in 129Xe SEOP. 131Xe is the only stable noble gas isotope with a positive gyromagnetic ratio and shows therefore a different relative phase between hp signal and thermal signal compared to all other noble gases. The gas phase 131Xe NMR spectrum displays a surface and magnetic field dependent quadrupolar splitting that was found to have additional gas pressure and gas composition dependence. The splitting was reduced by the presence of water vapor that presumably influences xenon-surface interactions. The hp 131Xe spectrum shows differential line broadening, suggesting the presence of strong adsorption sites. Beyond hp 131Xe NMR spectroscopy studies, a general equation for the high temperature, thermal spin polarization, P, for spin I?1/2 nuclei is presented.

Stupic, Karl F.; Cleveland, Zackary I.; Pavlovskaya, Galina E.; Meersmann, Thomas

2011-01-01

86

NMR Measures of Heterogeneity Length  

NASA Astrophysics Data System (ADS)

Advanced solid state NMR spectroscopy provides a wealth of information about structure and dynamics of complex systems. On a local scale, multidimensional solid state NMR has elucidated the geometry and the time scale of segmental motions at the glass transition. The higher order correlation functions which are provided by this technique led to the notion of dynamic heterogeneities, which have been characterized in detail with respect to their rate memory and length scale. In polymeric and low molar mass glass formers of different fragility, length scales in the range 2 to 4 nm are observed. In polymeric systems, incompatibility of backbone and side groups as in polyalkylmethacrylates leads to heteogeneities on the nm scale, which manifest themselves in unusual chain dynamics at the glass transition involving extended chain conformations. References: K. Schmidt-Rohr and H.W. Spiess, Multidimensional Solid-State NMR and Polymers,Academic Press, London (1994). U. Tracht, M. Wilhelm, A. Heuer, H. Feng, K. Schmidt-Rohr, H.W. Spiess, Phys. Rev. Lett. 81, 2727 (1998). S.A. Reinsberg, X.H. Qiu, M. Wilhelm, M.D. Ediger, H.W. Spiess, J.Chem.Phys. 114, 7299 (2001). S.A. Reinsberg, A. Heuer, B. Doliwa, H. Zimmermann, H.W. Spiess, J. Non-Crystal. Solids, in press (2002)

Spiess, Hans W.

2002-03-01

87

Alterations in Phosphate Metabolism during Cellular Recovery of Radiation Damage in Yeast,  

National Technical Information Service (NTIS)

Alterations were examined in phosphate pools during cellular recovery from radiation damage in intact, wild-type diploid yeast cells using phosphorus 31 nuclear magnetic resonance (NMR) spectroscopy. Concurrent cell survival analysis was determined follow...

P. K. Holahan S. A. Knizner C. M. Gabriel C. E. Swenberg

1988-01-01

88

Quantitative 2D liquid-state NMR.  

PubMed

Two-dimensional liquid-state NMR has a very high potential to simultaneously determine the absolute concentration of small molecules in complex mixtures, thanks to its capacity to separate overlapping resonances. However, 2D NMR experiments suffer from a number of limitations which affect their quantitative performance. The last ten years have witnessed an increasing number of contributions where quantitative approaches based on 2D NMR were developed and applied to solve real analytical issues. In this review special feature article, Dr. Patrick Giraudeau (University of Nantes) describes these recent efforts to reach a high trueness and precision in quantitative measurements by 2D NMR. Different strategies are presented in a critical way, combining NMR developments with analytical chemistry protocols. The recent efforts to speed up the duration of quantitative 2D NMR experiments are particularly highlighted. PMID:24817633

Giraudeau, P

2014-06-01

89

Development of LC-13C NMR  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

90

Phosphorus-31 metabolism of post-menopausal breast cancer studied in vivo by magnetic resonance spectroscopy.  

PubMed Central

We have studied the metabolism of 31P-containing metabolites of post-menopausal breast cancers in vivo using magnetic resonance spectroscopy (MRS) and a 5.5 cm surface coil. Spectra were acquired from 23 diameter. The spectra of the 19 previously untreated tumours had significantly higher phosphomonoester (PME) 31P relative peak areas than the normal breasts of eight post-menopausal women (11.7% and 7.7% respectively, P = 0.002). Although an increased PME relative peak area was characteristic of malignancy, PME relative peak area is similarly raised in lactating breast and, therefore, not a specific feature of cancer. An apparently lower nucleotide triphosphate (NTP) relative peak area in tumours than healthy postmenopausal breast was secondary to the differences in PME relative peak area; contamination by signal from chest wall muscle probably accounts for the ostensibly higher phosphocreatine (PCr) relative peak area of the tumours. Spectroscopy was repeated following chemotherapy in six women. An increase in PCr relative peak area was seen in all five patients who responded, but again this may represent increased contamination secondary to changes in tumour size. A fall in PME relative peak area was noted in four responders, but also one non-responder, so this finding may not be sufficiently specific to be of use clinically. Further studies are need to elucidate fully the role of MRS in breast cancer.

Twelves, C. J.; Porter, D. A.; Lowry, M.; Dobbs, N. A.; Graves, P. E.; Smith, M. A.; Rubens, R. D.; Richards, M. A.

1994-01-01

91

NMR analysis of plant nitrogen metabolism  

Microsoft Academic Search

The analysis of primary and secondary nitrogen metabolism in plants by nuclear magnetic resonance (NMR) spectroscopy is comprehensively reviewed. NMR is a versatile analytical tool, and the combined use of 1H, 2H, 13C, 14N and 15N NMR allows detailed investigation of the acquisition, assimilation and metabolism of nitrogen. The analysis of tissue extracts can be complemented by the in vivo

F. Mesnard; R. G. Ratcliffe

2005-01-01

92

Applications of NMR in Dairy Research  

PubMed Central

NMR is a robust analytical technique that has been employed to investigate the properties of many substances of agricultural relevance. NMR was first used to investigate the properties of milk in the 1950s and has since been employed in a wide range of studies; including properties analysis of specific milk proteins to metabolomics techniques used to monitor the health of dairy cows. In this brief review, we highlight the different uses of NMR in the dairy industry.

Maher, Anthony D.; Rochfort, Simone J.

2014-01-01

93

Solution NMR of Large Molecules and Assemblies †  

Microsoft Academic Search

Solution NMR spectroscopy represents a powerful tool for examining the structure and function of biological macromolecules. The advent of multidimensional (2D-4D) NMR, together with the widespread use of uniform isotopic labeling of proteins and RNA with the NMR-active isotopes, 15N and 13C, opened the door to detailed analyses of macromolecular structure, dynamics, and interactions of smaller macromolecules (<25 kDa). Over

Mark P. Foster; Craig A. McElroy; Carlos D. Amero

2007-01-01

94

NMR Spectroscopy of Experimentally Shocked Silicate Minerals  

Microsoft Academic Search

Magic-angle spinning nuclear magnetic resonance (MAS NMR) techniques were used to analyze experimentally shocked quartz and feldspar powders. ²⁹Si NMR spectra were determined for quartz and labradorite feldspar and ²⁷Al and ²³Na spectra for labradorite. Both minerals were shocked to 7.5, 16.4, and 22 GPA using the Sandia Momma Bear'' recovery fixtures. The MAS NMR results for quartz are in

R. T. Cygan; M. B. Boslough; R. J. Kirkpatrick

1991-01-01

95

Quantitative 2D liquid-state NMR.  

PubMed

Two-dimensional (2D) liquid-state NMR has a very high potential to simultaneously determine the absolute concentration of small molecules in complex mixtures, thanks to its capacity to separate overlapping resonances. However, it suffers from two main drawbacks that probably explain its relatively late development. First, the 2D NMR signal is strongly molecule-dependent and site-dependent; second, the long duration of 2D NMR experiments prevents its general use for high-throughput quantitative applications and affects its quantitative performance. Fortunately, the last 10?years has witnessed an increasing number of contributions where quantitative approaches based on 2D NMR were developed and applied to solve real analytical issues. This review aims at presenting these recent efforts to reach a high trueness and precision in quantitative measurements by 2D NMR. After highlighting the interest of 2D NMR for quantitative analysis, the different strategies to determine the absolute concentrations from 2D NMR spectra are described and illustrated by recent applications. The last part of the manuscript concerns the recent development of fast quantitative 2D NMR approaches, aiming at reducing the experiment duration while preserving - or even increasing - the analytical performance. We hope that this comprehensive review will help readers to apprehend the current landscape of quantitative 2D NMR, as well as the perspectives that may arise from it. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24700689

Giraudeau, Patrick

2014-06-01

96

Analytical Applications of NMR: Summer Symposium on Analytical Chemistry.  

ERIC Educational Resources Information Center

Highlights a symposium on analytical applications of nuclear magnetic resonance spectroscopy (NMR), discussing pulse Fourier transformation technique, two-dimensional NMR, solid state NMR, and multinuclear NMR. Includes description of ORACLE, an NMR data processing system at Syracuse University using real-time color graphics, and algorithms for…

Borman, Stuart A.

1982-01-01

97

NMR View: A computer program for the visualization and analysis of NMR data  

Microsoft Academic Search

NMR View is a computer program designed for the visualization and analysis of NMR data. It allows the user to interact with a practically unlimited number of 2D, 3D and 4D NMR data files. Any number of spectral windows can be displayed on the screen in any size and location. Automatic peak picking and facilitated peak analysis features are included

Bruce A. Johnson; Richard A. Blevins

1994-01-01

98

Picoliter H-1 NMR Spectroscopy  

SciTech Connect

A RF probe that fits inside the bore of a small gradient coil package is described for routine 1H-NMR microscopy measurements on small samples. The probe operates at 500 MHz and houses a 267-um-diameter solenoid transceiver. When used in three dimensional chemical shift imaging (3D-CSI) experiments, the measured signal-to-noise ratio (SNR) is shown to be within 20-30 percent of theoretical limits formulated by only considering the solenoid's resistive losses. This is illustrated using a 100-um-diameter globule of triacylglycerols ({approx}900mM) that may be an oocyte precursor in young Xenopus Laevis frogs, and water sample containing choline at a concentration often found in live cells ({approx}33mM). In chemical shift images generated using a few thousand scans, the choline methyl line is found to have an acceptable SNR in resolved from just 5 picoliters in the Xenopus globule. It is concluded that the probe's sensitivity is sufficient for performing 1H-NMR on picoliter-scale volumes in biological cells and tissues.

Minard, Kevin R.(BATTELLE (PACIFIC NW LAB)) [BATTELLE (PACIFIC NW LAB); Wind, Robert A.(BATTELLE (PACIFIC NW LAB)) [BATTELLE (PACIFIC NW LAB)

2002-02-01

99

NMR studies of oriented molecules  

SciTech Connect

Deuterium and proton magnetic resonance are used in experiments on a number of compounds which either form liquid crystal mesophases themselves or are dissolved in a liquid crystal solvent. Proton multiple quantum NMR is used to simplify complicated spectra. The theory of nonselective multiple quantum NMR is briefly reviewed. Benzene dissolved in a liquid crystal are used to demonstrate several outcomes of the theory. Experimental studies include proton and deuterium single quantum (..delta..M = +-1) and proton multiple quantum spectra of several molecules which contain the biphenyl moiety. 4-Cyano-4'-n-pentyl-d/sub 11/-biphenyl (5CB-d/sub 11/) is studied as a pure compound in the nematic phase. The obtained chain order parameters and dipolar couplings agree closely with previous results. Models for the effective symmetry of the biphenyl group in 5CB-d/sub 11/ are tested against the experimental spectra. The dihedral angle, defined by the planes containing the rings of the biphenyl group, is found to be 30 +- 2/sup 0/ for 5DB-d/sub 11/. Experiments are also described for 4,4'-d/sub 2/-biphenyl, 4,4' - dibromo-biphenyl, and unsubstituted biphenyl.

Sinton, S.W.

1981-11-01

100

Hypothesis driven assessment of an NMR curriculum  

NASA Astrophysics Data System (ADS)

The goal of this project was to develop a battery of assessments to evaluate an undergraduate NMR curriculum at Penn State University. As a chemical education project, we sought to approach the problem of curriculum assessment from a scientific perspective, while remaining grounded in the education research literature and practices. We chose the phrase hypothesis driven assessment to convey this process of relating the scientific method to the study of educational methods, modules, and curricula. We began from a hypothesis, that deeper understanding of one particular analytical technique (NMR) will increase undergraduate students' abilities to solve chemical problems. We designed an experiment to investigate this hypothesis, and data collected were analyzed and interpreted in light of the hypothesis and several related research questions. The expansion of the NMR curriculum at Penn State was funded through the NSF's Course, Curriculum, and Laboratory Improvement (CCLI) program, and assessment was required. The goal of this project, as stated in the grant proposal, was to provide NMR content in greater depth by integrating NMR modules throughout the curriculum in physical chemistry, instrumental, and organic chemistry laboratory courses. Hands-on contact with the NMR spectrometer and NMR data and repeated exposure of the analytical technique within different contexts (courses) were unique factors of this curriculum. Therefore, we maintained a focus on these aspects throughout the evaluation process. The most challenging and time-consuming aspect of any assessment is the development of testing instruments and methods to provide useful data. After key variables were defined, testing instruments were designed to measure these variables based on educational literature (Chapter 2). The primary variables measured in this assessment were: depth of understanding of NMR, basic NMR knowledge, problem solving skills (HETCOR problem), confidence for skills used in class (within the hands-on NMR modules), confidence for NMR tasks (not practiced), and confidence for general science tasks. Detailed discussion of the instruments, testing methods and experimental design used in this assessment are provided (Chapter 3). All data were analyzed quantitatively using methods adapted from the educational literature (Chapter 4). Data were analyzed and the descriptive statistics, independent t-tests between the experimental and control groups, and correlation statistics were calculated for each variable. In addition, for those variables included on the pretest, dependent t-tests between pretest and posttest scores were also calculated. The results of study 1 and study 2 were used to draw conclusions based on the hypothesis and research questions proposed in this work (Chapter 4). Data collected in this assessment were used to answer the following research questions: (1) Primary research question: Is depth of understanding of NMR linked to problem solving skills? (2) Are the NMR modules working as intended? Do they promote depth of understanding of NMR? (a) Will students who complete NMR modules have a greater depth of understanding of NMR than students who do not complete the modules? (b) Is depth of understanding increasing over the course of the experiment? (3) Is confidence an intermediary between depth of understanding and problem solving skills? Is it linked to both variables? (4) What levels of confidence are affected by the NMR modules? (a) Will confidence for the NMR class skills used in the modules themselves be greater for those who have completed the modules? (b) Will confidence for NMR tasks not practiced in the course be affected? (c) Will confidence for general science tasks be affected? (d) Are different levels of confidence (class skills, NMR tasks, general science tasks) linked to each other? Results from this NMR curriculum assessment could also have implications outside of the courses studied, and so there is potential to impact the chemical education community (section 5.2.1). In addition to providing reliable testing instrume

Cossey, Kimberly

101

Large NMR signals and polarization asymmetries.  

SciTech Connect

A large modulation in the series Q-meter can lead to nonlinear NMR signals and asymmetric polarization values. With a careful circuit analysis the nonlinearity can be estimated and corrections to polarization can be determined as a function of the strength of the modulation. We describe the recent LAMPF polarized proton target experiment, its NMR measurement and corrections to the measured polarizations.

Penttila, S. I.

1998-11-25

102

NMR Spectroscopy and Its Value: A Primer  

ERIC Educational Resources Information Center

Nuclear magnetic resonance (NMR) spectroscopy is widely used by chemists. Furthermore, the use of NMR spectroscopy to solve structures of macromolecules or to examine protein-ligand interactions is popular. Yet, few students entering graduate education in biological sciences have been introduced to this method or its utility. Over the last six…

Veeraraghavan, Sudha

2008-01-01

103

Nanostructured electrode surfaces studied by electrochemical NMR  

Microsoft Academic Search

Electrochemical nuclear magnetic resonance (EC-NMR) is a powerful local probe, which combines solid state NMR with electrochemistry. It is a unique technique that permits a unified, electronic-level study of the metal and adsorbate side of the electrochemical interface. Experiments can be performed either under direct potentiostatic control and in situ potential adjustment, or with samples prepared in a separate electrochemical

P. K. Babu; Y. Y. Tong; H. S. Kim; A. Wieckowski

2002-01-01

104

An Integrated Laboratory Project in NMR Spectroscopy.  

ERIC Educational Resources Information Center

Describes an advanced NMR project that can be done with a 60-MHz continuous-wave proton spectrometer. Points out the main purposes are to give students experience in second-order NMR analysis, the simplification of spectra by raising the frequency, and the effect of non-hydrogen nuclei on proton resonances. (MVL)

Hudson, Reggie L.; Pendley, Bradford D.

1988-01-01

105

An Inversion Recovery NMR Kinetics Experiment  

ERIC Educational Resources Information Center

A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this…

Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping

2011-01-01

106

NMR spectroscopy of experimentally shocked silicate minerals.  

National Technical Information Service (NTIS)

Magic-angle spinning nuclear magnetic resonance (MAS NMR) techniques were used to analyze experimentally shocked quartz and feldspar powders. (sup 29)Si NMR spectra were determined for quartz and labradorite feldspar and (sup 27)Al and (sup 23)Na spectra ...

R. T. Cygan M. B. Boslough R. J. Kirkpatrick

1991-01-01

107

Additivity of NMR isotope shifts  

SciTech Connect

One of the most interesting and useful aspects of the isotope effect on nuclear magnetic shielding is the proportionality of the shift to the number of substituted atoms in equivalent positions. In this paper we show the quantitative basis for the additivity of isotope shifts in NMR, using the CX/sub 4-n/Y/sub n/ (X,Y = H,D,T) system and the linear triatomic systems CO/sub 2/, NNO, and OCS as examples. We also predict small deviations from additivity and find that these deviations are consistent with those observed for /sup 14/N shifts in the NH/sub 4-n/D/sup +//sub n/ homologous series. Furthermore, we determine the mass dependence of the one-bond isotope shift.

Jameson, C.J.; Osten, H.

1984-11-15

108

Probing porous media with gas diffusion NMR  

NASA Technical Reports Server (NTRS)

We show that gas diffusion nuclear magnetic resonance (GD-NMR) provides a powerful technique for probing the structure of porous media. In random packs of glass beads, using both laser-polarized and thermally polarized xenon gas, we find that GD-NMR can accurately measure the pore space surface-area-to-volume ratio, S/V rho, and the tortuosity, alpha (the latter quantity being directly related to the system's transport properties). We also show that GD-NMR provides a good measure of the tortuosity of sandstone and complex carbonate rocks.

Mair, R. W.; Wong, G. P.; Hoffmann, D.; Hurlimann, M. D.; Patz, S.; Schwartz, L. M.; Walsworth, R. L.

1999-01-01

109

On electrophoretic NMR. Exploring high conductivity samples  

NASA Astrophysics Data System (ADS)

The performance of a new electrophoretic NMR (eNMR) method that uses a Carr-Purcell-Meiboom-Gill echo train with repeated electric field reversal is investigated. We show that this pulse sequence, with acronym CPMGER, yields strongly reduced artifacts from convective flow effects caused by the simultaneous presence of electroosmotic and thermal driving forces. We demonstrate the achieved improvements in various aqueous solutions. Ultimately, the method can be used for obtaining electrophoretic mobilities by eNMR without relying on uncharged reference molecules, otherwise a significant limitation for electrophoretic experiments performed with nuclei other than 1H.

Bielejewski, Micha?; Giesecke, Marianne; Furó, István

2014-06-01

110

Biological magnetic resonance: vol. 5  

SciTech Connect

This book discusses magnetic resonance techniques (NMR and ESR) as applied to biochemical research. Topics considered include the applications of carbon-13 NMR spectroscopy in investigations of metabolic pathways in vivo, the use of nitrogen-15 NMR in studies of systems of biological interest, phosphorus-31 NMR investigations of enzyme systems, the principles and state-of-the-art advances in the use of oxygen isotopes in phosphorus-31 and oxygen-17 NMR studies of biophosphates, and electron spin resonance and nuclear magnetic resonance studies of lipid-protein interactions in membranes.

Berliner, L.J.; Reuben, J.

1983-01-01

111

A New Microcell Technique for NMR Analysis.  

ERIC Educational Resources Information Center

Describes a new laboratory technique for working with small samples of compounds used in nuclear magnetic resonance (NMR) analysis. Demonstrates how microcells can be constructed for each experiment and samples can be recycled. (TW)

Yu, Sophia J.

1987-01-01

112

Bayesian peak picking for NMR spectra.  

PubMed

Protein structure determination is a very important topic in structural genomics, which helps people to understand varieties of biological functions such as protein-protein interactions, protein-DNA interactions and so on. Nowadays, nuclear magnetic resonance (NMR) has often been used to determine the three-dimensional structures of protein in vivo. This study aims to automate the peak picking step, the most important and tricky step in NMR structure determination. We propose to model the NMR spectrum by a mixture of bivariate Gaussian densities and use the stochastic approximation Monte Carlo algorithm as the computational tool to solve the problem. Under the Bayesian framework, the peak picking problem is casted as a variable selection problem. The proposed method can automatically distinguish true peaks from false ones without preprocessing the data. To the best of our knowledge, this is the first effort in the literature that tackles the peak picking problem for NMR spectrum data using Bayesian method. PMID:24184964

Cheng, Yichen; Gao, Xin; Liang, Faming

2014-02-01

113

Diffusion Techniques for In vivo NMR.  

National Technical Information Service (NTIS)

In vivo NMR experiments can result in a number of biophysical properties of the measured object. Among these properties are: morphology, concentrations of metabolites, reaction rates, relaxation rates, velocity, magnetic coupling (by magnetization transfe...

P. van Gelderen

1993-01-01

114

Solvent Signal is a NMR Concentration Reference  

PubMed Central

We propose that the NMR solvent signal be utilized as a universal concentration reference because most solvents can be observed by NMR, and solvent concentrations can be readily calculated or determined independently. In particular, a highly protonated solvent such as water can serve as a primary concentration standard for its stability, availability and ease of observation. The potential issues of radiation damping associated with a strong NMR signal can be alleviated by small pulse angle excitations. The solvent signal then can be detected by the NMR receiver with the same efficiency as a dilute analyte. We demonstrated that the analyte's proton concentration can be accurately determined from 4 ?M to more than 100 M, referenced by solvent (water) protons of concentrations more than 10 M. The proposed method is robust and indifferent to probe tuning, and does not require any additional concentration standard.

Mo, Huaping; Raftery, Daniel

2009-01-01

115

NMR spectroscopy of peptides and proteins  

Microsoft Academic Search

High resolution nuclear magnetic resonance (NMR) spectroscopy is the only method available for determining the three-dimensional\\u000a structures of peptides and proteins in solution at atomic resolution. This article deals with a range of practical considerations\\u000a associated with such studies, including sample preparation, instrumental setup, one- and two-dimensional NMR methods, interpretation\\u000a of spectral data, and structure calculations.

Mark G. Hinds; Raymond S. Norton

1997-01-01

116

Frontiers of NMR in Molecular Biology  

SciTech Connect

NMR spectroscopy is expanding the horizons of structural biology by determining the structures and describing the dynamics of blobular proteins in aqueous solution, as well as other classes of proteins including membrane proteins and the polypeptides that form the aggregates diagnostic of prion and amyloid diseases. Significant results are also emerging on DNA and RNA oligomers and their complexes with proteins. This meeting focused attention on key structural questions emanating from molecular biology and how NMR spectroscopy can be used to answer them.

NONE

1999-08-25

117

Deuterium NMR of polymer dispersed liquid crystals  

Microsoft Academic Search

Submicrometer-size droplets of monomeric liquid crystals dispersed in a solid polymer matrix are studied by deuterium NMR. Phase-separation processes are used to achieve droplets of a size comparable and less than the magnetic coherence length xi~0.5 mum, of the NMR magnetic field, 4.7 T. Selectively deuterated (4'-pentoxy- and 4'-methoxy-) 4-cyanobiphenyl compounds (5OCB-d2) and (1OCB-d3) deuterated in the alpha and methyl

A. Golemme; S. Zumer; J. W. Doane; M. E. Neubert

1988-01-01

118

Planar microcoil-based microfluidic NMR probes  

Microsoft Academic Search

Microfabricated small-volume NMR probes consisting of electroplated planar microcoils integrated on a glass substrate with etched microfluidic channels are fabricated and tested. 1H NMR spectra are acquired at 300MHz with three different probes having observed sample volumes of respectively 30, 120, and 470nL. The achieved sensitivity enables acquisition of an 1H spectrum of 160?g sucrose in D2O, corresponding to a

C. Massin; F. Vincent; A. Homsy; K. Ehrmann; G. Boero; P.-A Besse; A. Daridon; E. Verpoorte; N. F de Rooij; R. S Popovic

2003-01-01

119

Automated structure determination from NMR spectra  

Microsoft Academic Search

Automated methods for protein structure determination by NMR have increasingly gained acceptance and are now widely used for\\u000a the automated assignment of distance restraints and the calculation of three-dimensional structures. This review gives an\\u000a overview of the techniques for automated protein structure analysis by NMR, including both NOE-based approaches and methods\\u000a relying on other experimental data such as residual dipolar

Peter Güntert

2009-01-01

120

NMR Studies of a Timekeeping System  

Microsoft Academic Search

Cyanobacterial circadian clocks represent perhaps the best studied timekeeping system in terms of the molecular and mechanistic\\u000a information available; structural biology has contributed significantly in both respects. We present here an overview of progress\\u000a made using traditional high-resolution nuclear magnetic resonance (NMR) spectroscopy on the structures of these proteins in\\u000a solution. Combining NMR and a dissection approach yielded high-resolution structures

Ioannis Vakonakis; Andy LiWang

121

NMR exposure sensitizes tumor cells to apoptosis  

Microsoft Academic Search

NMR technology has dramatically contributed to the revolution of image diagnostic. NMR apparatuses use combinations of microwaves\\u000a over a homogeneous strong (1 Tesla) static magnetic field. We had previously shown that low intensity (0.3–66 mT) static magnetic\\u000a fields deeply affect apoptosis in a Ca2+ dependent fashion (Fanelli et al., 1999 FASEBJ., 13;95–102). The rationale of the present study is to examine whether

L. Ghibelli; C. Cerella; S. Cordisco; G. Clavarino; S. Marazzi; M. De Nicola; S. Nuccitelli; M. D'Alessio; A. Magrini; A. Bergamaschi; V. Guerrisi; L. M. Porfiri

2006-01-01

122

Moderne Entwicklung der NMR (Nuclear Magnetic Resonance)  

NASA Astrophysics Data System (ADS)

Die NMR-Spektroskopie kann sich altersmäßig nicht mit den Annalen der Physik messen; sie entstand vor rd. 45 Jahren. Ihre Entwicklung wurde und wird durch unterschiedliche Erfahrungen, Erkenntnisse und Techniken bestimmt; sie zeigt, daß auch heute noch die Fortschritte von Spezialgebieten Impulse aus weiten Bereichen der Physik, der Naturwissenschaften und Technik beziehen. In entsprechender Weise machen Spezialzeitschriften das Erscheinen allgemeiner Fachzeitschriften nicht überflüssig. Diese Zusammenhänge sollen an einigen Beispielen der NMR demonstriert werden.Translated AbstractModern Development of NMR (Nuclear Magnetic Resonance)The age of NMR-spectroscopy is not comparable with that of the Annalen der Physik; NMR was established only about 45 years ago. Its development was promoted by different experience, knowledge and techniques; it shows that also in these days the progress of a special topic depends on stimulations by other parts of physics, of natural and technical science. In an analogous way general scientific journals are not made superfluous by the existence of special papers. These relations are demonstrated with some examples in NMR.

Lösche, Artur

123

33S NMR cryogenic probe for taurine detection  

NASA Astrophysics Data System (ADS)

With the goal of a 33S nuclear magnetic resonance (NMR) probe applicable to in vivo NMR on taurine-biological samples, we have developed the 33S NMR cryogenic probe, which is applicable to taurine solutions. The NMR sensitivity gain relative to a conventional broadband probe is as large as 3.5. This work suggests that improvements in the preamplifier could allow NMR measurements on 100 ?M taurine solutions, which is the level of sensitivity necessary for biological samples.

Hobo, Fumio; Takahashi, Masato; Maeda, Hideaki

2009-03-01

124

NMR at low and ultralow temperatures.  

PubMed

Solid state nuclear magnetic resonance (NMR) measurements at low temperatures have been common in physical sciences for many years and are becoming increasingly important in studies of biomolecular systems. This Account reviews a diverse set of projects from my laboratory, dating back to the early 1990s, that illustrate the motivations for low-temperature solid state NMR, the types of information that are available from the measurements, and likely directions for future research. These projects include NMR studies of both physical and biological systems, performed at low (cooled with nitrogen, down to 77 K) and ultralow (cooled with helium, below 77 K) temperatures, and performed with and without magic-angle spinning (MAS). NMR studies of physical systems often focus on phenomena that occur only at low temperatures. Two examples from my laboratory are studies of molecular rotation and orientational ordering in solid C60 at low temperatures and studies of unusual electronic states, called skyrmions, in two-dimensionally confined electron systems within semiconductor quantum wells. To study quantum wells, we used optical pumping of nuclear spin polarizations to enhance their NMR signals. The optical pumping phenomenon exists only at ultralow temperatures. In studies of biomolecular systems, low-temperature NMR has several motivations. In some cases, low temperatures suppress molecular tumbling, thereby permitting solid state NMR measurements on soluble proteins. Studies of AIDS-related peptide/antibody complexes illustrate this effect. In other cases, low temperatures suppress conformational exchange, thereby permitting quantitation of conformational distributions. Studies of chemically denatured states of the model protein HP35 illustrate this effect. Low temperatures and rapid freeze-quenching can also be used to trap transient intermediate states in a non-equilibrium kinetic process, as shown in studies of a transient intermediate in the rapid folding pathway of HP35. NMR sensitivity generally increases with decreasing sample temperature. Therefore, it can be useful to carry out experiments at the lowest possible temperatures, particularly in studies of biomolecular systems in frozen solutions. However, solid state NMR studies of biomolecular systems generally require rapid MAS. A novel MAS NMR probe design that uses nitrogen gas for sample spinning and cold helium only for sample cooling allows a wide variety of solid state NMR measurements to be performed on biomolecular systems at 20-25 K, where signals are enhanced by factors of 12-15 relative to measurements at room temperature. MAS NMR at ultralow temperatures also facilitates dynamic nuclear polarization (DNP), allowing sizeable additional signal enhancements and large absolute NMR signal amplitudes with relatively low microwave powers. Current research in my laboratory seeks to develop and exploit DNP-enhanced MAS NMR at ultralow temperatures, for example, in studies of transient intermediates in protein folding and aggregation processes and studies of peptide/protein complexes that can be prepared only at low concentrations. PMID:23470028

Tycko, Robert

2013-09-17

125

AQUA and PROCHECK-NMR: Programs for checking the quality of protein structures solved by NMR  

Microsoft Academic Search

The AQUA and PROCHECK-NMR programs provide a means of validating the geometry and restraint violations of an ensemble of protein structures solved by solution NMR. The outputs include a detailed breakdown of the restraint violations, a number of plots in PostScript format and summary statistics. These various analyses indicate both the degree of agreement of the model structures with the

Roman A. Laskowski; J. Antoon C. Rullmann; Malcolm W. MacArthur; Robert Kaptein; Janet M. Thornton

1996-01-01

126

Nuclear magnetic resonance apparatus having semitoroidal rf coil for use in topical NMR and NMR imaging  

DOEpatents

An improved nuclear magnetic resonance (NMR) apparatus for use in topical magnetic resonance (TMR) spectroscopy and other remote sensing NMR applications includes a semitoroidal radio-frequency (rf) coil. The semitoroidal rf coil produces an effective alternating magnetic field at a distance from the poles of the coil, so as to enable NMR measurements to be taken from selected regions inside an object, particularly including human and other living subjects. The semitoroidal rf coil is relatively insensitive to magnetic interference from metallic objects located behind the coil, thereby rendering the coil particularly suited for use in both conventional and superconducting NMR magnets. The semitoroidal NMR coil can be constructed so that it emits little or no excess rf electric field associated with the rf magnetic field, thus avoiding adverse effects due to dielectric heating of the sample or to any other interaction of the electric field with the sample.

Fukushima, Eiichi (Los Alamos, NM); Roeder, Stephen B. W. (La Mesa, CA); Assink, Roger A. (Albuquerque, NM); Gibson, Atholl A. V. (Bryan, TX)

1986-01-01

127

Characterization of heroin samples by 1H NMR and 2D DOSY 1H NMR.  

PubMed

Twenty-four samples of heroin from different illicit drug seizures were analyzed using proton Nuclear Magnetic Resonance ((1)H NMR) and two-dimensional diffusion-ordered spectroscopy (2D DOSY) (1)H NMR. A careful assignment and quantification of (1)H signals enabled a comprehensive characterization of the substances present in the samples investigated: heroin, its main related impurities (6-acetylmorphine, acetylcodeine, morphine, noscapine and papaverine) and cutting agents (caffeine and acetaminophen in nearly all samples as well as lactose, lidocaine, mannitol, piracetam in one sample only), and hence to establish their spectral signatures. The good agreement between the amounts of heroin, noscapine, caffeine and acetaminophen determined by (1)H NMR and gas chromatography, the reference method in forensic laboratories, demonstrates the validity of the (1)H NMR technique. In this paper, 2D DOSY (1)H NMR offers a new approach for a whole characterization of the various components of these complex mixtures. PMID:24378299

Balayssac, Stéphane; Retailleau, Emmanuel; Bertrand, Geneviève; Escot, Marie-Pierre; Martino, Robert; Malet-Martino, Myriam; Gilard, Véronique

2014-01-01

128

Application of NMR spectroscopy and LC-NMR/MS to the identification of carbohydrates in beer.  

PubMed

The application of LC-NMR/MS for the direct identification of carbohydrates in beer has been studied. Carbohydrates are major beer components, and their structural characterization by NMR alone is seriously hindered by strong spectroscopic overlap. Direct analysis of beer by LC-NMR/MS enables the rapid (1-2 h) identification of dextrins with degree of polymerization (DP) of up to nine monomers, with degassing being the only sample treatment required. Although the presence of alpha(1-->6) branching points is easily indicated by NMR for each subfraction separated by LC, difficulties arise for the unambiguous assignment of linear or branched forms of high DP dextrins. The two beer samples investigated in this work were found to have significantly different oligosaccharide compositions, reflecting the different production conditions employed. The use of hyphenated NMR for the rapid characterization of the carbohydrate composition of beers may be the basis of a useful tool for the quality control of beer. PMID:12903934

Duarte, Iola F; Godejohann, Markus; Braumann, Ulrich; Spraul, Manfred; Gil, Ana M

2003-08-13

129

BOOK REVIEW: NMR Imaging of Materials  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) of materials is a field of increasing importance. Applications extend from fundamental science like the characterization of fluid transport in porous rock, catalyst pellets and hemodialysers into various fields of engineering for process optimization and product quality control. While the results of MRI imaging are being appreciated by a growing community, the methods of imaging are far more diverse for materials applications than for medical imaging of human beings. Blümich has delivered the first book in this field. It was published in hardback three years ago and is now offered as a paperback for nearly half the price. The text provides an introduction to MRI imaging of materials covering solid-state NMR spectroscopy, imaging methods for liquid and solid samples, and unusual MRI in terms of specialized approaches to spatial resolution such as an MRI surface scanner. The book represents an excellent and thorough treatment which will help to grow research in materials MRI. Blümich developed the treatise over many years for his research students, graduates in chemistry, physics and engineering. But it may also be useful for medical students looking for a less formal discussion of solid-state NMR spectroscopy. The structure of this book is easy to perceive. The first three chapters cover an introduction, the fundamentals and methods of solid-state NMR spectroscopy. The book starts at the ground level where no previous knowledge about NMR is assumed. Chapter 4 discusses a wide variety of transformations beyond the Fourier transformation. In particular, the Hadamard transformation and the 'wavelet' transformation are missing from most related books. This chapter also includes a description of noise-correlation spectroscopy, which promises the imaging of large objects without the need for extremely powerful radio-frequency transmitters. Chapters 5 and 6 cover basic imaging methods. The following chapter about the use of relaxation and spectroscopic methods to weight or filter the spin signals represents the core of the book. This is a subject where Blümich is deeply involved with substantial contributions. The chapter includes a lot of ideas to provide MR contrast between different regions based on their mobility, diffusion, spin couplings or NMR spectra. After describing NMR imaging methods for solids with broad lines, Blümich spends time on applications in the last two chapters of the book. This part is really fun to read. It underlines the effort to bring NMR into many kinds of manufacturing. Car tyres and high-voltage cables are just two such areas. Elastomeric materials, green-state ceramics and food science represent other interesting fields of applications. This part of the book represents a personal but nevertheless extensive compilation of modern applications. As a matter of course the MOUSE is presented, a portable permanent-magnet based NMR developed by Blümich and his co-workers. Thus the book is not only of interest to NMR spectroscopists but also to people in material science and chemical engineering. The bibliography and indexing are excellent and may serve as an attractive reference source for NMR spectroscopists. The book is the first on the subject and likely to become the standard text for NMR imaging of materials as the books by Abragam, Slicher and Ernst et al are for NMR spectroscopy. The purchase of this beautiful book for people dealing with NMR spectroscopy or medical MRI is highly recommended. Ralf Ludwig

Blümich, Bernhard

2003-09-01

130

Nuclear magnetic resonance (NMR) blood flow imaging  

SciTech Connect

Picture element values in NMR images are dependent not only upon T/sub 1/ and T/sub 2/ relaxation times but also on the local density and velocity of hydrogen nuclei moving through the region being imaged. In 1959 the potential of non-imaging NMR for measuring blood flow was demonstrated. Recently several investigators have proposed methods for combining NMR imaging with NMR blood flow measurements. The authors have investigated the relationships between various radiofrequency pulse sequences and flow rate and their effects on image intensity using a constant flow pump and a 0.5 Tesla Technicare Teslacon NMR imager. Dilute mixtures of ethylene glycol were used to simulate blood. Flow measurements were made in Tygon Tubing (12 mm) at variable velocities ranging from 0-35 cm/sec. The flow phantom was used to calibrate several pulse sequences relating image intensity and vascular flow velocity. Representative patient studies demonstrating blood-flow have been performed. The calibration is being extended to pulsatile flow systems.

Price, R.R.; Patton, J.A.; Kulkarni, M.D.; Pickens, D.R.; Erickson, J.J.; Stephens, W.H.; Partain, C.L.; James, A.E. Jr.

1984-01-01

131

Applications of NMR to biological systems  

SciTech Connect

This work describes the application of nuclear magnetic resonance spectrometry (NMR) for the study of three biological systems, namely, the pulmonary surfactant-associated protein, SPL(pVal), the myocardial calcium slow channel of the perfused guinea pig heart, and the intracellular buffering system of the Leishmania donovani promastigote. Investigations of structural features of bovine SPL(pVal) were performed using one and two-dimensional {sup 1}H-NMR techniques. Delayed Fourier transform {sup 1}H-NMR has been used to study the effects of bovine SPL(pVal) and temperature upon model membrane structure. A model describing the mechanism by which the SPL(pVal) lowers the membrane surface tension has been proposed. In order to study the dependence of the myocardial calcium slow channel activity on adenosine triphosphate levels and intracellular pH, and in vivo {sup 31}P-NMR probe capable of simultaneously and noninvasively monitoring these three parameters was designed. In vivo {sup 31}P-NMR was also applied for the study of the Leishmania donovani promastigote's ability to maintain a pH gradient across its cellular membrane at low extracellular pH.

Baatz, J.E.

1988-01-01

132

NMR methodologies in the analysis of blueberries.  

PubMed

An NMR analytical protocol based on complementary high and low field measurements is proposed for blueberry characterization. Untargeted NMR metabolite profiling of blueberries aqueous and organic extracts as well as targeted NMR analysis focused on anthocyanins and other phenols are reported. Bligh-Dyer and microwave-assisted extractions were carried out and compared showing a better recovery of lipidic fraction in the case of microwave procedure. Water-soluble metabolites belonging to different classes such as sugars, amino acids, organic acids, and phenolic compounds, as well as metabolites soluble in organic solvent such as triglycerides, sterols, and fatty acids, were identified. Five anthocyanins (malvidin-3-glucoside, malvidin-3-galactoside, delphinidin-3-glucoside, delphinidin-3-galactoside, and petunidin-3-glucoside) and 3-O-?-l-rhamnopyranosyl quercetin were identified in solid phase extract. The water status of fresh and withered blueberries was monitored by portable NMR and fast-field cycling NMR. (1) H depth profiles, T2 transverse relaxation times and dispersion profiles were found to be sensitive to the withering. PMID:24668393

Capitani, Donatella; Sobolev, Anatoly P; Delfini, Maurizio; Vista, Silvia; Antiochia, Riccarda; Proietti, Noemi; Bubici, Salvatore; Ferrante, Gianni; Carradori, Simone; De Salvador, Flavio Roberto; Mannina, Luisa

2014-06-01

133

Biological NMR FIDs and spectra normalization  

NASA Astrophysics Data System (ADS)

There is increasing use of spectroscopic techniques, such as high-resolution NMR spectroscopy, to examine variations in cell metabolism and / or structure in response to numerous physical, chemical, and biological agents. In these types of studies, in order to obtain relative quantitative information, a comparison between signal intensities of control samples and treated or exposed ones is often conducted. The methods thus far developed for this purpose are not directly related to the overall intrinsic properties of the samples, but rather to the addition of external substances of known concentrations or to indirect measurement of internal substances. Another possibility is to estimate, by an opportune algorithm, a normalization constant which takes into consideration all cell metabolites present in the sample. Recently, a new normalization algorithm, based on Principal Component Analysis (PCA), was presented. PCA is a well-known statistical technique for analysis of large, multivariate datasets, which extracts the basic features of the data. The PRICONA (PRincipal COmponent Normalization Algorithm) algorithm use PCA in a new totally different manner: PCA is, in fact, used to normalize spectra in order to obtain quantitative information about the treatment effects. In this paper, a comparison of results obtained in the time domain, that is on NMR FIDs (Free Induction Decay) and in the frequency domain, on NMR spectra, is conducted. The comparison is useful because in NMR spectroscopy analysis in the different domain can have different advantages. The algorithm was tested by Monte Carlo simulations of NMR FIDs.

Romano, R.; Canonico, R.; Acernese, F.; Giordano, G.; Barone, F.

2014-03-01

134

Gas NMR Characterization of Oil Shale  

NASA Astrophysics Data System (ADS)

Accurate descriptions and simulations of oil reservoirs such as carbonate-rich sedimentary rock are important for the efficient development and conversion of recoverable energy reserves. These descriptions depend on reliable measures of the properties of the formation rock such as absolute and effective porosity, mineralogical composition, permeability, and tortuosity. NMR signal relaxation time (T1 and T2) and measurements of restricted diffusion of gases in porous media can be used to probe multi-pore media, yielding valuable petrophysical information and allowing the characterization of internal topology and pore size distribution. We employ NMR techniques on imbibed fluorinated and hyperpolarized noble gases - gases with the unique properties of being chemically inert and minimally invasive while exhibiting favorable NMR properties - at various pressure and temperatures to characterize the shale heterogeneity. We show current results of our characterizations and explore ideas for future work.

Sorte, Eric; Laicher, Gernot; Saam, Brian

2007-10-01

135

Remote Tuning of NMR Probe Circuits  

NASA Astrophysics Data System (ADS)

There are many circumstances in which the probe tuning adjustments cannot be located near the rf NMR coil. These may occur in high-temperature NMR, low-temperature NMR, and in the use of magnets with small diameter access bores. We address here circuitry for connecting a fixed-tuned probe circuit by a transmission line to a remotely located tuning network. In particular, the bandwidth over which the probe may be remotely tuned while keeping the losses in the transmission line acceptably low is considered. The results show that for all resonant circuit geometries (series, parallel, series-parallel), overcoupling of the line to the tuned circuit is key to obtaining a large tuning bandwidth. At equivalent extents of overcoupling, all resonant circuit geometries have nearly equal remote tuning bandwidths. Particularly for the case of low-loss transmission line, the tuning bandwidth can be many times the tuned circuit's bandwidth, f o/Q.

Kodibagkar, Vikram D.; Conradi, Mark S.

2000-05-01

136

Remote tuning of NMR probe circuits.  

PubMed

There are many circumstances in which the probe tuning adjustments cannot be located near the rf NMR coil. These may occur in high-temperature NMR, low-temperature NMR, and in the use of magnets with small diameter access bores. We address here circuitry for connecting a fixed-tuned probe circuit by a transmission line to a remotely located tuning network. In particular, the bandwidth over which the probe may be remotely tuned while keeping the losses in the transmission line acceptably low is considered. The results show that for all resonant circuit geometries (series, parallel, series-parallel), overcoupling of the line to the tuned circuit is key to obtaining a large tuning bandwidth. At equivalent extents of overcoupling, all resonant circuit geometries have nearly equal remote tuning bandwidths. Particularly for the case of low-loss transmission line, the tuning bandwidth can be many times the tuned circuit's bandwidth, f(o)/Q. PMID:10783273

Kodibagkar, V D; Conradi, M S

2000-05-01

137

NMR Spectroscopy: Processing Strategies (by Peter Bigler)  

NASA Astrophysics Data System (ADS)

Peter Bigler. VCH: New York, 1997. 249 pp. ISBN 3-527-28812-0. $99.00. This book, part of a four-volume series planned to deal with all aspects of a standard NMR experiment, is almost the exact book I have been hoping to find. My department has acquired, as have hundreds of other undergraduate institutions, high-field NMR instrumentation and the capability of doing extremely sophisticated experiments. However, the training is often a one- or two-day experience in which the material retained by the faculty trained is garbled and filled with holes, not unlike the information our students seem to retain. This text, and the accompanying exercises based on data contained on a CD-ROM, goes a long way to fill in the gaps and clarify misunderstandings about NMR processing.

Mills, Nancy S.

1998-06-01

138

An NMR Study of Microvoids in Polymers  

NASA Technical Reports Server (NTRS)

An understanding of polymer defect structures, like microvoids in polymeric matrices, is most crucial to their fabrication and application potential. In this project guest atoms are introduced into the microvoids in PMR-15 and NMR is used to determine microvoid sizes and locations. Xenon is a relatively inert probe that would normally not be found naturally in polymer or in NMR probe materials. There are two NMR active Xenon isotopes, Xe-129 and Xe-131. The Xe atom has a very high polarizability, which makes it sensitive to the intracrystalline environment of polymers. Interactions between the Xe atoms and the host matrix perturb and Xe electron cloud, deshielding the nuclei, and thereby expanding the range of the observed NMR chemical shifts. This chemical shift range which may be as large as 5000 ppm, permits subtle structural and chemical effects to be studied with high sensitivity. The Xe-129-NMR line shape has been found to vary in response to changes in the pore symmetry of the framework hosts in Zeolites and Clathrasil compounds. Before exposure to Xe gas, the PMR-15 samples were dried in a vacuum oven at 150 C for 48 hours. The samples were then exposed to Xe gas at 30 psi for 72 hours and sealed in glass tubes with 1 atmosphere of Xenon gas. Xenon gas at 1 atmosphere was used to tune up the spectrometer and to set up the appropriate NMR parameters. A series of spectra were obtained interspersed with applications of vacuum and heating to drive out the adsorbed Xe and determine the role of Xe-Xe interactions in the observed chemical shift.

Toy, James; Mattrix, Larry

1996-01-01

139

Tritiation methods and tritium NMR spectroscopy  

SciTech Connect

We have used a simple process for the production of highly tritiated water and characterized the product species by {sup 1}H and {sup 3}H NMR spectroscopy. The water is readily manipulated and used in subsequent reactions either as T{sub 2}O, CH{sub 3}COOT or CF{sub 3}COOT. Development of tritiated diimide has progressed to the point where cis-hydrogenated products at 1-20 Ci/mmole S.A. are possible. Tri-n-butyl tin tritide has been produced at >95% tritium content and well characterized by multinuclear NMR techniques. 27 refs., 3 figs.

Jaiswal, D.K. [Defence Research and Development Establishment, Gwalior (India); Morimoto, H.; Salijoughian, M.; Williams, P.G. [Lawrence Berkeley Lab., CA (United States)

1991-09-01

140

NMR Structure of Human Thymosin Alpha-1  

PubMed Central

800 MHz NMR structure of the 28-residue peptide thymosin alpha-1 in 40% TFE/60% water (v/v) has been determined. Restrained molecular dynamic simulations with an explicit solvent box containing 40% TFE/60% TIP3P water (v/v) were used, in order to get the 3D model of the NMR structure. We found that the peptide adopts a structured conformation having two stable regions: an alpha-helix region from residues 14 to 26 and two double ?-turns in the N-terminal twelve residues which form a distorted helical structure.

Elizondo-Riojas, Miguel-Angel; Chamow, Steven M.; Tuthill, Cynthia W.; Gorenstein, David G.; Volk, David E.

2012-01-01

141

NMR structure of human thymosin alpha-1.  

PubMed

800 MHz NMR structure of the 28-residue peptide thymosin alpha-1 in 40% TFE/60% water (v/v) has been determined. Restrained molecular dynamic simulations with an explicit solvent box containing 40% TFE/60% TIP3P water (v/v) were used, in order to get the 3D model of the NMR structure. We found that the peptide adopts a structured conformation having two stable regions: an alpha-helix region from residues 14 to 26 and two double ?-turns in the N-terminal twelve residues which form a distorted helical structure. PMID:22115779

Elizondo-Riojas, Miguel-Angel; Chamow, Steven M; Tuthill, Cynthia W; Gorenstein, David G; Volk, David E

2011-12-16

142

Contactless NMR spectroscopy on a chip.  

PubMed

Inductively coupled planar resonators offer convenient integration of high-resolution NMR spectroscopy with microfluidic lab-on-a-chip devices. Planar spiral resonators are fabricated lithographically either by gold electroplating or by etching Cu laminated with polyimide. Their performance is characterized by NMR imaging as well as spectroscopy. A single-scan limit of detection LOD(t) = 0.95 nmol s(1/2) was obtained from sample volumes around 1 ?L. The sensitivity of this approach is similar to that obtained by microstripline and microslot probes. PMID:22409303

Ryan, Herbert; Song, Suk-Heung; Zaß, Anja; Korvink, Jan; Utz, Marcel

2012-04-17

143

NMR spectra of androstane analogs of brassinosteroids  

NASA Astrophysics Data System (ADS)

We have used two-dimensional NMR spectroscopy to make a complete assignment of signals from the nuclei of hydrogen and carbon atoms in the spectra of brassinosteroids in the androstane series. We have confirmed the stereochemistry of the chiral centers and the structure of the molecules. We have studied the effect of the configuration of the 2,3-diol groups in the A ring of the steroids on the chemical shift of adjacent atoms in the 13C and 1H NMR spectra.

Baranovskii, A. V.; Litvinovskaya, R. P.; Aver'kova, M. A.; Khripach, N. B.; Khripach, V. A.

2007-09-01

144

NMR lipid profiles of cells, tissues, and body fluids: proton NMR analysis of human erythrocyte lipids.  

PubMed

One- and two-dimensional high resolution NMR spectroscopy was applied to determine quantitatively and qualitatively the lipids extracted from human erythrocyte membranes. The relative amounts of the major lipids were determined from the spectra of unfractionated lipid extracts. After HPLC fractionation of the lipid extracts and NMR analysis of the fractions, it was possible to determine the features of the component lipids of each lipid class and to compare, especially, the fatty acid types and composition of the individual major glycerophospholipids. The results of this proton NMR analysis were compared to those obtained elsewhere using classical lipid analytical techniques and found to be in substantial agreement. PMID:7868971

Adosraku, R K; Choi, G T; Constantinou-Kokotos, V; Anderson, M M; Gibbons, W A

1994-11-01

145

Recommendations of the wwPDB NMR Validation Task Force.  

PubMed

As methods for analysis of biomolecular structure and dynamics using nuclear magnetic resonance spectroscopy (NMR) continue to advance, the resulting 3D structures, chemical shifts, and other NMR data are broadly impacting biology, chemistry, and medicine. Structure model assessment is a critical area of NMR methods development, and is an essential component of the process of making these structures accessible and useful to the wider scientific community. For these reasons, the Worldwide Protein Data Bank (wwPDB) has convened an NMR Validation Task Force (NMR-VTF) to work with wwPDB partners in developing metrics and policies for biomolecular NMR data harvesting, structure representation, and structure quality assessment. This paper summarizes the recommendations of the NMR-VTF, and lays the groundwork for future work in developing standards and metrics for biomolecular NMR structure quality assessment. PMID:24010715

Montelione, Gaetano T; Nilges, Michael; Bax, Ad; Güntert, Peter; Herrmann, Torsten; Richardson, Jane S; Schwieters, Charles D; Vranken, Wim F; Vuister, Geerten W; Wishart, David S; Berman, Helen M; Kleywegt, Gerard J; Markley, John L

2013-09-01

146

Study of Cultured Fibroblasts in Vivo Using NMR.  

National Technical Information Service (NTIS)

The goal was to study the compartmentation of phosphorylated glycolytic intermediates in intact Chicken Embryo Fibroblasts (CEFs) using sup 31 P NMR at 109 MHz. A technique for maintaining functional cells at high densities in an NMR magnet is described. ...

G. S. Karczmar

1984-01-01

147

Pulsed Zero Field NMR of Solids and Liquid Crystals.  

National Technical Information Service (NTIS)

This work describes the development and applications to solids and liquid crystals of zero field nuclear magnetic resonance (NMR) experiments with pulsed dc magnetic fields. Zero field NMR experiments are one approach for obtaining high resolution spectra...

A. M. Thayer

1987-01-01

148

A Primer of Fourier Transform NMR.  

ERIC Educational Resources Information Center

Fourier transform nuclear magnetic resonance (NMR) is a new spectroscopic technique that is often omitted from undergraduate curricula because of lack of instructional materials. Therefore, information is provided to introduce students to the technique of data collection and transformation into the frequency domain. (JN)

Macomber, Roger S.

1985-01-01

149

NMR Studies of Aqueous Solution Structure.  

National Technical Information Service (NTIS)

Nmr chemical shifts and linewidths are reported for eleven substituted ureas and related compounds as a function of pH in aqueous solution. The effect of various added electrolytes on proton exchange rates and nitrogen relaxation rates is determined. Tren...

R. L. Vold

1973-01-01

150

Molecular Structure and Dynamics by NMR Spectroscopy  

NSDL National Science Digital Library

This site provides PowerPoint slides for a lecture for a graduate-level course in NMR spectroscopy. The slides include useful animations which help to demonstrate the concepts described. While the casual student may find it hard to follow everything on the slides without an accompanying lecture, the files should be very useful for advanced students or educators putting together similar courses.

Edison, Arthur S.; Long, Joanna

2011-07-04

151

Advanced Laboratory NMR Spectrometer with Applications.  

ERIC Educational Resources Information Center

A description is given of an inexpensive nuclear magnetic resonance (NMR) spectrometer suitable for use in advanced laboratory courses. Applications to the nondestructive analysis of the oil content in corn seeds and in monitoring the crystallization of polymers are presented. (SK)

Biscegli, Clovis; And Others

1982-01-01

152

Solid-State NMR for Bacterial Biofilms  

PubMed Central

Bacteria associate with surfaces and one another by elaborating an extracellular matrix to encapsulate cells, creating communities termed biofilms. Biofilms are beneficial in some ecological niches, but also contribute to the pathogenesis of serious and chronic infectious diseases. New approaches and quantitative measurements are needed to define the composition and architecture of bacterial biofilms to help drive the development of strategies to interfere with biofilm assembly. Solid-state NMR is uniquely suited to the examination of insoluble and complex macromolecular and whole-cell systems. This article highlights three examples that implement solid-state NMR to deliver insights into bacterial biofilm composition and changes in cell-wall composition as cells transition to the biofilm lifestyle. Most recently, solid-state NMR measurements provided a total accounting of the protein and polysaccharide components in the extracellular matrix of an E. coli biofilm and transform our qualitative descriptions of matrix composition into chemical parameters that permit quantitative comparisons among samples. We present additional data for whole biofilm samples (cells plus the extracellular matrix) that complement matrix-only analyses. The study of bacterial biofilms by solid-state NMR is an exciting avenue ripe with many opportunities and we close the article by articulating some outstanding questions and future directions in this area.

Reichhardt, Courtney; Cegelski, Lynette

2014-01-01

153

Homogeneous NMR Spectra in Inhomogeneous Fields  

Microsoft Academic Search

Researchers interested in high-resolution nuclear magnetic resonance (NMR) spectroscopy have long sought higher magnetic fields to enhance resolution and simplify spectra. Magnets with substantially larger fields than those available in the best commercial spectrometers are available, but the inhomogeneity is unacceptable for high-resolution spectra. A detection method (termed HOMOGENIZED) is presented that removes inhomogeneity while retaining chemical shift differences and

Sujatha Vathyam; Sanghyuk Lee; Warren S. Warren

1996-01-01

154

Long-lived NMR echoes in solids  

NASA Astrophysics Data System (ADS)

A new type of long-lived NMR echo in solids with homogeneously broadened dipolar spectra is discussed. The echo can be generated by a simple two-pulse Hahn sequence in solid samples, where dipolar-coupled nuclei have different chemical shifts. We present general considerations and simple theoretical models which explain some features of this phenomenon.

Khitrin, A. K.

2011-12-01

155

NMR analog of Bell's inequalities violation test  

NASA Astrophysics Data System (ADS)

In this paper, we present an analog of Bell's inequalities violation test for N qubits to be performed in a nuclear magnetic resonance (NMR) quantum computer. This can be used to simulate or predict the results for different Bell's inequality tests, with distinct configurations and a larger number of qubits. To demonstrate our scheme, we implemented a simulation of the violation of the Clauser, Horne, Shimony and Holt (CHSH) inequality using a two-qubit NMR system and compared the results to those of a photon experiment. The experimental results are well described by the quantum mechanics theory and a local realistic hidden variables model (LRHVM) that was specifically developed for NMR. That is why we refer to this experiment as a simulation of Bell's inequality violation. Our result shows explicitly how the two theories can be compatible with each other due to the detection loophole. In the last part of this work, we discuss the possibility of testing some fundamental features of quantum mechanics using NMR with highly polarized spins, where a strong discrepancy between quantum mechanics and hidden variables models can be expected.

Souza, A. M.; Magalhães, A.; Teles, J.; deAzevedo, E. R.; Bonagamba, T. J.; Oliveira, I. S.; Sarthour, R. S.

2008-03-01

156

NMR spectroscopy of experimentally shocked silicate minerals  

SciTech Connect

Magic-angle spinning nuclear magnetic resonance (MAS NMR) techniques were used to analyze experimentally shocked quartz and feldspar powders. {sup 29}Si NMR spectra were determined for quartz and labradorite feldspar and {sup 27}Al and {sup 23}Na spectra for labradorite. Both minerals were shocked to 7.5, 16.4, and 22 GPA using the Sandia Momma Bear'' recovery fixtures. The MAS NMR results for quartz are in full agreement with previous measurements, indicating a high degree of reproducibility. Numerical decomposition of quartz data are consistent with two distinct phases: a defective crystalline quartz and an amorphous-like silica phase. There is a strong correlation between the fraction of amorphous phase and the mean peak shock pressure. The labradorite data are much more complicated, consisting of multiple peaks with no obvious correlation with shock pressure. No amorphous phase was evident from the NMR spectra of the shocked labradorite, nor were high pressure phases detectable for either mineral. 6 refs., 3 figs., 1 tab.

Cygan, R.T.; Boslough, M.B. (Sandia National Labs., Albuquerque, NM (USA)); Kirkpatrick, R.J. (Illinois Univ., Urbana, IL (USA). Dept. of Geology)

1991-01-01

157

Solid-state NMR imaging system  

DOEpatents

An apparatus for use with a solid-state NMR spectrometer includes a special imaging probe with linear, high-field strength gradient fields and high-power broadband RF coils using a back projection method for data acquisition and image reconstruction, and a real-time pulse programmer adaptable for use by a conventional computer for complex high speed pulse sequences.

Gopalsami, Nachappa (Naperville, IL); Dieckman, Stephen L. (Elmhurst, IL); Ellingson, William A. (Naperville, IL)

1992-01-01

158

Ensemble quantum computing by NMR spectroscopy  

PubMed Central

A quantum computer (QC) can operate in parallel on all its possible inputs at once, but the amount of information that can be extracted from the result is limited by the phenomenon of wave function collapse. We present a new computational model, which differs from a QC only in that the result of a measurement is the expectation value of the observable, rather than a random eigenvalue thereof. Such an expectation value QC can solve nondeterministic polynomial-time complete problems in polynomial time. This observation is significant precisely because the computational model can be realized, to a certain extent, by NMR spectroscopy on macroscopic ensembles of quantum spins, namely molecules in a test tube. This is made possible by identifying a manifold of statistical spin states, called pseudo-pure states, the mathematical description of which is isomorphic to that of an isolated spin system. The result is a novel NMR computer that can be programmed much like a QC, but in other respects more closely resembles a DNA computer. Most notably, when applied to intractable combinatorial problems, an NMR computer can use an amount of sample, rather than time, which grows exponentially with the size of the problem. Although NMR computers will be limited by current technology to exhaustive searches over only 15 to 20 bits, searches over as much as 50 bits are in principle possible, and more advanced algorithms could greatly extend the range of applicability of such machines.

Cory, David G.; Fahmy, Amr F.; Havel, Timothy F.

1997-01-01

159

Al NMR: A novel NMR Data Processing Program Optimized for Sparse Sampling  

PubMed Central

Sparse sampling in biomolecular multidimensional NMR offers increased acquisition speed and resolution and, if appropriate conditions are met, an increase in sensitivity. Sparse sampling of indirectly detected time domains combined with the direct truly multidimensional Fourier transform has elicited particular attention because of the ability to generate a final spectrum amenable to traditional analysis techniques. A number of sparse sampling schemes have been described including radial sampling, random sampling, concentric sampling and variations thereof. A fundamental feature of these sampling schemes is that the resulting time domain data array is not amenable to traditional Fourier transform based processing and phasing correction techniques. In addition, radial sampling approaches offer a number of advantages and capabilities that are also not accessible using standard NMR processing techniques. These include sensitivity enhancement, sub-matrix processing and determination of minimal sets of sampling angles. Here we describe a new software package (Al NMR) that enables these capabilities in the context of a general NMR data processing environment.

Gledhill, John M.; Wand, A. Joshua

2011-01-01

160

Robustness of quantum discord to sudden death in NMR  

Microsoft Academic Search

We investigate the dynamics of entanglement and quantum discord of two qubits in liquid state homonuclear NMR. Applying a phenomenological description for NMR under relaxation process, and taking a group of typical parameters of NMR, we show that when a zero initial state $|00> $ experiences a relaxation process, its entanglement disappears completely after a sequence of so-called sudden deaths

Jianwei Xu; Qihui Chen

2011-01-01

161

Signal Reconstruction in Unstable Magnetic Field NMR with Wavelet Analysis  

Microsoft Academic Search

Recently, wavelet analysis has become a powerful tool and is widely used in nuclear magnetic resonance (NMR) signal processing. Wavelet transform can not only give the wavelet energy spectrum of NMR signals, but also give multiple characteristics of the signals, such as center frequency, maximum energy, and energy duration. Usually, wavelet transform is used in stable magnetic field NMR. In

Zhenmin Zhang; Ling Peng; Shuhui Cai; Zhong Chen

2009-01-01

162

An analytical methodology for magnetic field control in unilateral NMR  

Microsoft Academic Search

Traditionally, unilateral NMR systems such as the NMR-MOUSE have used the fringe field between two bar magnets joined with a yoke in a ‘U’ geometry. This allows NMR signals to be acquired from a sensitive volume displaced from the magnets, permitting large samples to be investigated. The drawback of this approach is that the static field (B0) generated in this

Andrew E. Marble; Igor V. Mastikhin; Bruce G. Colpitts; Bruce J. Balcom

2005-01-01

163

An NMR study of microvoids in polymers  

NASA Technical Reports Server (NTRS)

An understanding of polymer defect structures, like microvoids in polymeric matrices, is crucial to their fabrication and application potential. In this project guest atoms are introduced into the microvoids in PMR-15 and NMR is used to determine microvoid sizes and locations. Xenon is a relatively inert probe that would normally be found naturally in polymer or in NMR probe materials. There are two NMR active xenon isotopes, Xe-129 and Xe-131. The Xe atom has a very high polarizability, which makes it sensitive to the intracrystalline environment of polymers. Interactions between the Xe atoms and the host matrix perturb the Xe electron cloud, deshielding the nuclei, and thereby expanding the range of the observed NMR chemical shifts. This chemical shift range which may be as large as 5000 ppm, permits subtle structural and chemical effects to be studied with high sensitivity. The Xe(129)-NMR line shape has been found to vary in response to changes in the pore symmetry of the framework hosts line Zeolites and Clathrasil compounds. Before exposure to Xe gas, the PMR-15 samples were dried in a vacuum oven at 150 C for 48 hours. The samples were then exposed to Xe gas at 30 psi for 72 hours and sealed in glass tubes with 1 atmosphere of xenon gas. Xenon gas at 1 atmosphere was used to tune up the spectrometer and to set up the appropriate NMR parameters. A single Xe-129 line at 83.003498 Mhz (with protons at 300 Mhz) was observed for the gas. With the xenon charged PMR-15 samples, a second broader line is observed 190 ppm downfield from the gas line (also observed). The width of the NMR line from the Xe-129 absorbed in the polymer is at least partially due to the distribution of microvoid sizes. From the chemical shift (relative to the gas line) and the line width, we estimate the average void sizes to be 2.74 +/- 0.20 angstroms. Since Xe-129 has such a large chemical shift range (approximately 5000 ppm), we expect the chemical shift anisotropy to contribute to the line width (delta upsilon = 2.5 kHz).

Toy, James; Mattix, Larry

1995-01-01

164

Dynamic nuclear polarization surface enhanced NMR spectroscopy.  

PubMed

Many of the functions and applications of advanced materials result from their interfacial structures and properties. However, the difficulty in characterizing the surface structure of these materials at an atomic level can often slow their further development. Solid-state NMR can probe surface structure and complement established surface science techniques, but its low sensitivity often limits its application. Many materials have low surface areas and/or low concentrations of active/surface sites. Dynamic nuclear polarization (DNP) is one intriguing method to enhance the sensitivity of solid-state NMR experiments by several orders of magnitude. In a DNP experiment, the large polarization of unpaired electrons is transferred to surrounding nuclei, which provides a maximum theoretical DNP enhancement of ?658 for (1)H NMR. In this Account, we discuss the application of DNP to enhance surface NMR signals, an approach known as DNP surface enhanced NMR spectroscopy (DNP SENS). Enabling DNP for these systems requires bringing an exogeneous radical solution into contact with surfaces without diluting the sample. We proposed the incipient wetness impregnation technique (IWI), a well-known method in materials science, to impregnate porous and particulate materials with just enough radical containing solution to fill the porous volume. IWI offers several advantages: it is extremely simple, provides a uniform wetting of the surface, and does not increase the sample volume or substantially reduce the concentration of the sample. This Account describes the basic principles behind DNP SENS through results obtained for mesoporous and nanoparticulate samples impregnated with radical solutions. We also discuss the quantification of the overall sensitivity enhancements obtained with DNP SENS and compare that with ordinary room temperature NMR spectroscopy. We then review the development of radicals and solvents that give the best possible enhancements today. With the best polarizing mixtures, DNP SENS enhances sensitivity by a factor of up to 100, which decreases acquisition time by five orders of magnitude. Such enhancement enables the detailed and expedient atomic level characterization of the surfaces of complex materials at natural isotopic abundance and opens new avenues for NMR. To illustrate these improvements, we describe the successful application of DNP SENS to characterize hybrid materials, organometallic surface species, and metal-organic frameworks. PMID:23517009

Rossini, Aaron J; Zagdoun, Alexandre; Lelli, Moreno; Lesage, Anne; Copéret, Christophe; Emsley, Lyndon

2013-09-17

165

OPENCORE NMR: Open-source core modules for implementing an integrated FPGA-based NMR spectrometer  

NASA Astrophysics Data System (ADS)

A tool kit for implementing an integrated FPGA-based NMR spectrometer [K. Takeda, A highly integrated FPGA-based nuclear magnetic resonance spectrometer, Rev. Sci. Instrum. 78 (2007) 033103], referred to as the OPENCORE NMR spectrometer, is open to public. The system is composed of an FPGA chip and several peripheral boards for USB communication, direct-digital synthesis (DDS), RF transmission, signal acquisition, etc. Inside the FPGA chip have been implemented a number of digital modules including three pulse programmers, the digital part of DDS, a digital quadrature demodulator, dual digital low-pass filters, and a PC interface. These FPGA core modules are written in VHDL, and their source codes are available on our website. This work aims at providing sufficient information with which one can, given some facility in circuit board manufacturing, reproduce the OPENCORE NMR spectrometer presented here. Also, the users are encouraged to modify the design of spectrometer according to their own specific needs. A home-built NMR spectrometer can serve complementary roles to a sophisticated commercial spectrometer, should one comes across such new ideas that require heavy modification to hardware inside the spectrometer. This work can lower the barrier of building a handmade NMR spectrometer in the laboratory, and promote novel and exciting NMR experiments.

Takeda, Kazuyuki

2008-06-01

166

Squid detected NMR and MRI at ultralow fields  

DOEpatents

Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

Clarke, John (Berkeley, CA); Pines, Alexander (Berkeley, CA); McDermott, Robert F. (Monona, WI); Trabesinger, Andreas H. (London, GB)

2008-12-16

167

Squid detected NMR and MRI at ultralow fields  

DOEpatents

Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

Clarke, John (Berkeley, CA); McDermott, Robert (Louisville, CO); Pines, Alexander (Berkeley, CA); Trabesinger, Andreas Heinz (CH-8006 Zurich, CH)

2007-05-15

168

Multinuclear NMR studies of relaxor ferroelectrics  

NASA Astrophysics Data System (ADS)

Multinuclear NMR of 93Nb, 45Sc, and 207Pb has been carried out to study the structure, disorder, and dynamics of a series of important solid solutions: perovskite relaxor ferroelectric materials (1-x) Pb(Mg1/3Nb 2/3)O3-x Pb(Sc1/2Nb1/2)O 3 (PMN-PSN). 93Nb NMR investigations of the local structure and cation order/disorder are presented as a function of PSN concentration, x. The superb fidelity and accuracy of 3QMAS allows us to make clear and consistent assignments of spectral intensities to the 28 possible nearest B-site neighbor (nBn) configurations, (NMg, NSc, NNb), where each number ranges from 0 to 6 and their sum is 6. For most of the 28 possible nBn configurations, isotropic chemical shifts and quadrupole product constants have been extracted from the data. The seven configurations with only larger cations, Mg 2+ and Sc3+ (and no Nb5+) are assigned to the seven observed narrow peaks, whose deconvoluted intensities facilitate quantitative evaluation of, and differentiation between, different models of B-site (chemical) disorder. The "completely random" model is ruled out and the "random site" model is shown to be in qualitative agreement with the NMR experiments. To obtain quantitative agreement with observed NMR intensities, the random site model is slightly modified by including unlike-pair interaction energies. To date, 45Sc studies have not been as fruitful as 93Nb NMR because the resolution is lower in the 45Sc spectra. The lower resolution of 45Sc spectra is due to a smaller span of isotropic chemical shift (40 ppm for 45Sc vs. 82 ppm for 93Nb) and to the lack of a fortuitous mechanism that simplifies the 93Nb spectra; for 93Nb the overlap of the isotropic chemical shifts of 6-Sc and 6-Nb configurations results in the alignment of all the 28 configurations along only seven quadrupole distribution axes. Finally we present variable temperature 207Pb static, MAS, and 2D-PASS NMR studies. Strong linear correlations between isotropic and anisotropic chemical shifts show that Pb-O bonds vary from more ionic to more covalent environments. Distributions of Pb-O bond lengthes are also quantitatively described. Such distributions are used to examine two competing models of Pb displacements; the shell model and the unique direction model. Only the latter model is able to reproduce the observed Pb-O distance distribution.

Zhou, Donghua

169

WebSpectra: Problems in NMR and IR Spectroscopy  

NSDL National Science Digital Library

From the University of California at Los Angeles's Chemistry Department, WebSpectra provides chemistry students with a searchable library of Nuclear Magnetic Resonance (NMR) and Infrared (IR) spectroscopy problems. According to the makers of this innovative site, "Interpretation of spectra is a technique that requires practice - this site provides 1H NMR and 13C NMR, DEPT, COSY and IR spectra of various compounds for students to interpret." A set of instructional documents are entitled Solving Spectral Problems, Overview of NMR Spectroscopy, Notes on NMR Solvents, Types of NMR Spectra, Introduction to IR Spectra, and a Table of IR Absorptions. A wide variety of compounds and their spectra are available for interpretation and have been organized in categories from Beginning to Advanced. Spectrum for each compound may be magnified 16X by clicking on peaks. This is an outstanding learning tool for students coming to grips with interpreting NMR and IR spectra.

170

Protein Dynamics from NMR and Computer Simulation  

NASA Astrophysics Data System (ADS)

Proteins exhibit internal motions from the millisecond to sub-nanosecond time scale. The challenge is to relate these internal motions to biological function. A strategy to address this aim is to apply a combination of several techniques including high-resolution NMR, computer simulation of molecular dynamics (MD), molecular graphics, and finally molecular biology, the latter to generate appropriate samples. Two difficulties that arise are: (1) the time scale which is most directly biologically relevant (ms to ?s) is not readily accessible by these techniques and (2) the techniques focus on local and not collective motions. We will outline methods using ^13C-NMR to help alleviate the second problem, as applied to intestinal fatty acid binding protein, a relatively small intracellular protein believed to be involved in fatty acid transport and metabolism. This work is supported in part by PHS Grant GM34847 (FGP) and by a fellowship from the American Heart Association (QW).

Wu, Qiong; Kravchenko, Olga; Kemple, Marvin; Likic, Vladimir; Klimtchuk, Elena; Prendergast, Franklyn

2002-03-01

171

Some nitrogen-14 NMR studies in solids  

SciTech Connect

The first order quadrupolar perturbation of the /sup 14/N NMR spectrum yields information regarding the static and dynamic properties of the surrounding electronic environment. Signal to noise problems caused by long /sup 14/N longitudinal relaxation times (T/sub 1/) and small equilibrium polarizations are reduced by rotating frame cross polarization (CP) experiments between /sup 14/N and /sup 1/H. Using quadrupolar echo and CP techniques, the /sup 14/N quadrupolar coupling constants (e/sup 2/qQ/h) and asymmetry parameters (eta) have been obtained for a variety of tetraalkylammonium compounds by observation of their quadrupolar powder patterns at various temperatures. For choline chloride and iodide the /sup 14/N NMR powder patterns exhibit the effects of anisotropic molecular motion, while choline bromide spectra show no such effects.

Pratum, T.K.

1983-11-01

172

Protein structure determination from NMR chemical shifts.  

PubMed

NMR spectroscopy plays a major role in the determination of the structures and dynamics of proteins and other biological macromolecules. Chemical shifts are the most readily and accurately measurable NMR parameters, and they reflect with great specificity the conformations of native and nonnative states of proteins. We show, using 11 examples of proteins representative of the major structural classes and containing up to 123 residues, that it is possible to use chemical shifts as structural restraints in combination with a conventional molecular mechanics force field to determine the conformations of proteins at a resolution of 2 angstroms or better. This strategy should be widely applicable and, subject to further development, will enable quantitative structural analysis to be carried out to address a range of complex biological problems not accessible to current structural techniques. PMID:17535901

Cavalli, Andrea; Salvatella, Xavier; Dobson, Christopher M; Vendruscolo, Michele

2007-06-01

173

Protein structure determination from NMR chemical shifts  

PubMed Central

NMR spectroscopy plays a major role in the determination of the structures and dynamics of proteins and other biological macromolecules. Chemical shifts are the most readily and accurately measurable NMR parameters, and they reflect with great specificity the conformations of native and nonnative states of proteins. We show, using 11 examples of proteins representative of the major structural classes and containing up to 123 residues, that it is possible to use chemical shifts as structural restraints in combination with a conventional molecular mechanics force field to determine the conformations of proteins at a resolution of 2 ? or better. This strategy should be widely applicable and, subject to further development, will enable quantitative structural analysis to be carried out to address a range of complex biological problems not accessible to current structural techniques.

Cavalli, Andrea; Salvatella, Xavier; Dobson, Christopher M.; Vendruscolo, Michele

2007-01-01

174

Advances in automated NMR protein structure determination.  

PubMed

Around half of all protein structures solved nowadays using solution-state nuclear magnetic resonance (NMR) spectroscopy have been because of automated data analysis. The pervasiveness of computational approaches in general hides, however, a more nuanced view in which the full variety and richness of the field appears. This review is structured around a comparison of methods associated with three NMR observables: classical nuclear Overhauser effect (NOE) constraint gathering in contrast with more recent chemical shift and residual dipole coupling (RDC) based protocols. In each case, the emphasis is placed on the latest research, covering mainly the past 5 years. By describing both general concepts and representative programs, the objective is to map out a field in which--through the very profusion of approaches--it is all too easy to lose one's bearings. PMID:21411039

Guerry, Paul; Herrmann, Torsten

2011-08-01

175

NMR in a point contact device  

Microsoft Academic Search

Resistively-detected and ultra-sensitive nuclear magnetic resonance (NMR), which is suitable for high-mobility semiconductor hetero and nanostructures, has been developed. Fractional quantum hall physics enables us to dynamically polarize nuclear spins in a two-and one-dimensional channel and to detect the nuclear spin polarization by measuring the channel resistance. When an alternating magnetic field is applied to the channel, the coherent oscillation

Y. Hirayama

2006-01-01

176

High Pressure NMR Study of Ammonium Thiocyanate  

NASA Astrophysics Data System (ADS)

Wide-line proton NMR spectra of ammonium thiocyanate have been recorded at 77 K as a function of external hydrostatic pressure. Contrary to expectations the line-width and the second moment decrease with the increase of pressure. This, however, is in accordance with the anomalous behaviour observed in other magnetic resonance studies of this compound and can be understood in terms of the change of electron density around the nitrogen atom of the SCN- group.

Ramanathan, K. V.

1993-06-01

177

Understanding hydrated polymers: the perspective of NMR  

Microsoft Academic Search

This review examines the divergent views in the literature on the role of water in hydrated polymers, specifically the origin of non-freezable water. One approach, based largely on site-specific information furnished by NMR invokes binding sites in the host polymer matrix as a principal source of bound or non-freezable water; the second approach is based on the thermodynamics of metastable,

V. J. McBrierty; S. J. Martin; F. E. Karasz

1999-01-01

178

Automated protein structure calculation from NMR data  

Microsoft Academic Search

Current software is almost at the stage to permit completely automatic structure determination of small proteins of <15 kDa,\\u000a from NMR spectra to structure validation with minimal user interaction. This goal is welcome, as it makes structure calculation\\u000a more objective and therefore more easily validated, without any loss in the quality of the structures generated. Moreover,\\u000a it releases expert spectroscopists to

Mike P. Williamson; C. Jeremy Craven

2009-01-01

179

Automated NMR Structure Calculation With CYANA  

Microsoft Academic Search

Summary This chapter gives an introduction to automated nuclear magnetic resonance (NMR) structure calculation with the program CYANA. Given a sufficiently complete list of assigned chemical shifts and one or several lists of cross-peak positions and columes from two-, three-, or four- dimensional nuclear Overhauser effect spectroscopy (NOESY) spectra, the assignment of the NOESY cross-peaks and the three-dimensional structure of

Peter Güntert

180

Highly flexible pulse programmer for NMR applications  

NASA Technical Reports Server (NTRS)

A pulse generator for NMR application is described. Eighteen output channels are provided to allow use in single and double resonance experiments. Complex pulse sequences may be generated by loading instructions into a 256-word by 16-bit program memory. Features of the pulse generator include programmable time delays from 0.5 micros to 1000 s, branching and looping instructions, and the ability to be loaded and operated either manually or from a PDP-11/10 computer.

Dart, J.; Burum, D. P.; Rhim, W. K.

1980-01-01

181

NMR Structure of the Human Doppel Protein  

Microsoft Academic Search

The NMR structure of the recombinant human doppel protein, hDpl(24–152), contains a flexibly disordered “tail” comprising residues 24–51, and a globular domain extending from residues 52 to 149 for which a detailed structure was obtained. The globular domain contains four ?-helices comprising residues 72–80 (?1), 101–115 (?2a), 117–121 (?2b), and 127–141 (?3), and a short two-stranded anti-parallel ?-sheet comprising residues

Thorsten Lührs; Roland Riek; Peter Güntert; Kurt Wüthrich

2003-01-01

182

NMR Characterizations of Properties of Heterogeneous Media  

SciTech Connect

The overall goal of this project was to develop reliable methods for resolving macroscopic properties important for describing the flow of one or more fluid phases in reservoirs from formation measurements. Completed the facilities to house our new NMR imager, the equipment has been delivered and installed. New experimental designs will provide for more reliable estimation of permeability distributions were evaluated. Designed and built a new core holder to incorporate one of the new experimental designs.

Watson, A. Ted; Phan, Jack; Uh, Jinsoo; Michalak, Rudi; Xue, Song

2003-01-28

183

Video: Proton Nuclear Magnetic Resonance (NMR)  

NSDL National Science Digital Library

This video, distributed on YouTube by the Royal Society of Chemistry, describes the basic principles of Nuclear Magnetic Resonance. This video is a good primer and would be very useful to supplement introductory lectures on NMR. The video covers the basic theory behind a 1H spectrum and goes through actually acquiring a spectrum. The top-off look of the instrument is useful and how the superconducting magnet is mounted. Running time for the video is 8:43.

2011-06-03

184

NMR assessment on bone simulated under microgravity  

Microsoft Academic Search

Introduction Microgravity-induced bone loss has been suggested to be similar to disuse-osteoporosis on Earth which constitutes a challenging public health problem No current non-destructive method can provide the microstructural changes in bone particularly on cortical bone Recently the authors have applied low field nuclear magnetic resonance NMR spin-spin relaxation technique and computational analysis method to determine the porosity pore size

Q. Ni; Y. Qin

2006-01-01

185

NMR methodologies for studying mitochondrial bioenergetics.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy is a technique with an increasing importance in the study of metabolic diseases. Its initial important role in the determination of chemical structures (1, 2) has been considerably overcome by its potential for the in vivo study of metabolism (3-5). The main characteristic that makes this technique so attractive is its noninvasiveness. Only nuclei capable of transitioning between energy states, in the presence of an intense and constant magnetic field, are studied. This includes abundant nuclei such as proton ((1)H) and phosphorous ((31)P), as well as stable isotopes such as deuterium ((2)H) and carbon 13 ((13)C). This allows a wide range of applications that vary from the determination of water distribution in tissues (as obtained in a magnetic resonance imaging scan) to the calculation of metabolic fluxes under ex vivo and in vivo conditions without the need to use radioactive tracers or tissue biopsies (as in a magnetic resonance spectroscopy (MRS) scan). In this chapter, some technical aspects of the methodology of an NMR/MRS experiment as well as how it can be used to study mitochondrial bioenergetics are overviewed. Advantages and disadvantages of in vivo MRS versus high-resolution NMR using proton high rotation magic angle spinning (HRMAS) of tissue biopsies and tissue extracts are also discussed. PMID:22057574

Alves, Tiago C; Jarak, Ivana; Carvalho, Rui A

2012-01-01

186

NMR Studies of Cartilage Dynamics, Diffusion, Degradation  

NASA Astrophysics Data System (ADS)

An increasing number of people is suffering from rheumatic diseases, and, therefore, methods of early diagnosis of joint degeneration are urgently required. For their establishment, however, an improved knowledge about the molecular organisation of cartilage would be helpful. Cartilage consists of three main components: Water, collagen and chondroitin sulfate (CS) that is (together with further polysaccharides and proteins) a major constituent of the proteoglycans of cartilage. 1H and 13C MAS (magic-angle spinning) NMR (nuclear magnetic resonance) opened new perspectives for the study of the macromolecular components in cartilage. We have primarily studied the mobilities of CS and collagen in bovine nasal and pig articular cartilage (that differ significantly in their collagen/polysaccharide content) by measuring 13C NMR relaxation times as well as the corresponding 13C CP (cross polarisation) MAS NMR spectra. These data clearly indicate that the mobility of cartilage macromolecules is broadly distributed from almost completely rigid (collagen) to highly mobile (polysaccharides), which lends cartilage its mechanical strength and shock-absorbing properties.

Huster, Daniel; Schiller, Jürgen; Naji, Lama; et al.

187

Earth's field NMR; a surface moisture detector?  

NASA Astrophysics Data System (ADS)

Earth's field NMR (EFNMR), being free of magnets, would be an ideal teaching medium as well as a mobile NMR technique except for its weak S/N. The common EFNMR apparatus uses a powerful prepolarization field to enhance the spin magnetization before the experiment. We introduce a coil design geared to larger but manageable samples with sufficient sensitivity without prepolarization to move EFNMR closer to routine use and to provide an inexpensive teaching tool. Our coil consists of parallel wires spread out on a plywood to form a current sheet with the current return wires separated so they will not influence the main part of the coil assembly. The sensitive region is a relatively thin region parallel to the coil and close to it. A single turn of the coil is wound to be topologically equivalent to a figure-8. The two crossing segments in the center of a figure-8 form two of the parallel wires of the flat coil. Thus, a two-turn figure-8 has four crossing wires so its topologically equivalent coil will have four parallel wires with currents in phase. Together with the excellent sensitivity, this coil offers outstanding interference rejection because of the figure-8 geometry. An example of such a coil has 328 parallel wires covering a ˜1 meter square plywood which yields a good NMR signal from 26 liters of water spread out roughly over the area of the coil in less than one minute in a nearby park.

Fukushima, Eiichi; Altobelli, Stephen; McDowell, Andrew; Zhang, Tongsheng

2012-10-01

188

Direct chiral discrimination in NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Conventional nuclear magnetic resonance spectroscopy is unable to distinguish between the two mirror-image forms (enantiomers) of a chiral molecule. This is because the NMR spectrum is determined by the chemical shifts and spin-spin coupling constants which - in the absence of a chiral solvent - are identical for the two enantiomers. We discuss how chirality may nevertheless be directly detected in liquid-state NMR spectroscopy: In a chiral molecule, the rotating nuclear magnetic moment induces an electric dipole moment in the direction perpendicular to itself and to the permanent magnetic field of the spectrometer. We present computations of the precessing electric polarization following a ?/2 pulse. Our estimates indicate that the electric polarization should be detectable in favourable cases. We also predict that application of an electrostatic field induces a chirally sensitive magnetization oscillating in the direction of the permanent magnetic field. We show that the electric-field-perturbed chemical shift tensor, the nuclear magnetic shielding polarizability, underlies these chiral NMR effects.

Buckingham, A. D.; Fischer, P.

2006-05-01

189

NMR properties of petroleum reservoir fluids.  

PubMed

NMR well logging of petroleum reservoir require the measurement of the NMR response of water, oil, and gas in the pore space of rocks at elevated temperatures and pressures. The viscosity of the oil may range from less than 1 cp to greater than 10,000 cp. Also, the oil and gas are not a single component but rather a broad distribution of components. The log mean T1 and T2 relaxation time of dead (gas free) crude oils are correlated with viscosity/temperature and Larmor frequency. The relaxation time of live oils deviate from the correlation for dead crude oils. This deviation can be correlated with the methane content of the oil. Natural gas in the reservoir has components other than methane. Mixing rules are developed to accommodate components such as ethane, propane, carbon dioxide, and nitrogen. Interpretation of NMR logs uses both relaxation and diffusion to distinguish the different fluids present in the formation. Crude oils have a broad spectrum of components but the relaxation time distribution and diffusion coefficient distribution are correlated. This correlation is used to distinguish crude oil from the response of water in the pores of the rock. This correlation can also be used to estimate viscosity of the crude oil. PMID:12850718

Hirasaki, George J; Lo, Sho-Wei; Zhang, Ying

2003-01-01

190

RHODOPSIN-LIPID INTERACTIONS STUDIED BY NMR  

PubMed Central

The biophysical properties of the lipid matrix are known to influence function of integral membrane proteins. We report on a sample preparation method for reconstitution of membrane proteins which uses porous anodic aluminum oxide (AAO) filters with 200 nm-wide pores of high density. The substrate permits formation of tubular, single membranes that line the inner surface of pores. One square centimeter of filter with a thickness of 60 ?m yields on the order of 500 cm2 of solid-supported single bilayer surface, sufficient for NMR studies. The tubular bilayers are free of detergent, fully hydrated and accessible for ligands from one side of the membrane. The use of AAO filters greatly improves reproducibility of the reconstitution process such that the influence of protein on lipid order parameters can be studied with high resolution. As an example, results for the G protein-coupled receptor of class A, bovine rhodopsin, are shown. By 2H NMR order parameter measurements it is detected that rhodopsin insertion elastically deforms membranes near the protein. Furthermore, by 1H saturation-transfer NMR under conditions of magic-angle spinning (MAS), we demonstrate detection of preferences in interactions of rhodopsin with particular lipid species. It is assumed that function of integral membrane proteins depends on both protein-induced elastic deformations of the lipid matrix and preferences for interaction of the protein with particular lipid species in the first layer of lipids surrounding the protein.

Soubias, Olivier; Gawrisch, Klaus

2012-01-01

191

Analysis of lanthanide-induced conformational change of the C-terminal domain on centrin.  

PubMed

Centrin, an EF-hand calcium-binding protein with high homology to calmodulin (CaM), is an essential component of microtubule-organizing center (MTOC). Lanthanide (Ln) ions can improve the stability, increase the amount and enhance the orderliness of microtubules, which are components of cytoskeleton. In order to investigate the structural basis of Ln ions on enhancing orderliness of microtubules, we characterized the binding properties of Ln ions with the isolated C-terminal domain of the Euplotes centrin (C-EoCen). Results suggested that Ln ions may occupy the canonical Ca(2+) binding sites on C-EoCen with middle affinity. Near- and far-UV CD spectra of C-EoCen displayed pronounced differences before and after additing Ln ions. The asymmetry of microenvironments of Phe on C-EoCen was changed. Using 2-p-toluidinylnaphthalene-6- sulfonate (TNS) as probe, Ln ions induced C-EoCen to undergo conformational changes from closed state to open state, resulting in exposing hydrophobic patches to external environments. Ln ions have more obvious effect on the conformation of centrin than Ca(2+). The differences found in the interactions of centrin binding with Ln ions/Ca(2+) maybe provide some insights for structural basis of centrin functions in vivo. PMID:21947611

Zhao, Ya-Qin; Yan, Jun; Song, Li; Feng, Ya-Nan; Liang, Ai-Hua; Yang, Bin-Sheng

2012-01-01

192

NMR spectroscopy of experimentally shocked single crystal quartz: A reexamination of the NMR shock barometer  

NASA Technical Reports Server (NTRS)

Cygan and others report a broadening of the Si-29 nuclear magnetic resonance (NMR) peak for synthetic quartz powders with increasing shock pressure which they propose as a shock wave barometer for natural systems. These results are expanded by studying single crystal quartz shocked to 12 and 33 GPa using the 6.5 m two-stage light-gas gun at Lawrence Livermore National Laboratories. Our NMR results differ substantially from those of Cygan and others and suggest that the proposed shock wave barometer may require refinement. The difference in results between this study and that of Cygan and others is most likely caused by different starting materials (single crystal vs. powder) and different shock loading histories. NMR results from single crystal studies may be more applicable to natural systems.

Fiske, P. S.; Gratz, A. J.; Nellis, W. J.

1993-01-01

193

Quantum theory of NMR adiabatic pulses and their applications. [NMR (nuclear magnetic resonance)  

SciTech Connect

Recently explosive developments of in vivo NMR spectroscopy (NMRS) and imaging (NMRI) in biological and medical sciences have resulted in the establishment of NMR as one of the most advanced major technique in life sciences. These developments have created huge demands for a variety of NMR adiabatic pulses with play a very important role in NMR experiments in vivo. In order to develop new NMR adiabatic pulses, a rigorous systematical quantum theory for this kind of pulses is greatly needed. Providing such a theory is one of the important goals of this dissertation. Quantum density matrix theory and product operator method have been used throughout this dissertation. Another goal, which is the major goal of this thesis research, is to use the quantum theory as a guide to develop new NMR adiabatic pulses and their applications. To fill this goal, a technique to construct a new type of adiabatic pulses, narrow band selective adiabatic pulses, has been invented, which is described through the example of constructing an adiabatic DANTE inversion pulse. This new adiabatic pulse is the first narrow band selective adiabatic pulses: Adiabatic homonuclear and heteronuclear spectral editing sequences. Unique to the first pulse sequence is a B[sub 1]-field filter which is built by using two non-refocusing adiabatic full passage pulses to refocus the wanted signal and dephase unwanted signals. This extra filter greatly enhance the editing efficiency. Unlike commonly used heteronuclear spectral editing sequences which depend on the polarization transfer or spectral subtraction by phase cycling techniques, the second pulse sequences accomplishes the editing of heteronuclear J-coupled signals based on the fact that this sequence is transparent to the uncoupled spins and is equivalent a 90[degrees] excitation pulse to the heteronuclear J-coupled spins. Experimental results have confirmed the ability of spectral editing with these two new sequences.

Ke, Y.

1993-01-01

194

Fast automated protein NMR data collection and assignment by ADAPT-NMR on Bruker spectrometers  

NASA Astrophysics Data System (ADS)

ADAPT-NMR (Assignment-directed Data collection Algorithm utilizing a Probabilistic Toolkit in NMR) supports automated NMR data collection and backbone and side chain assignment for [U-13C, U-15N]-labeled proteins. Given the sequence of the protein and data for the orthogonal 2D 1H-15N and 1H-13C planes, the algorithm automatically directs the collection of tilted plane data from a variety of triple-resonance experiments so as to follow an efficient pathway toward the probabilistic assignment of 1H, 13C, and 15N signals to specific atoms in the covalent structure of the protein. Data collection and assignment calculations continue until the addition of new data no longer improves the assignment score. ADAPT-NMR was first implemented on Varian (Agilent) spectrometers [A. Bahrami, M. Tonelli, S.C. Sahu, K.K. Singarapu, H.R. Eghbalnia, J.L. Markley, PLoS One 7 (2012) e33173]. Because of broader interest in the approach, we present here a version of ADAPT-NMR for Bruker spectrometers. We have developed two AU console programs (ADAPT_ORTHO_run and ADAPT_NMR_run) that run under TOPSPIN Versions 3.0 and higher. To illustrate the performance of the algorithm on a Bruker spectrometer, we tested one protein, chlorella ubiquitin (76 amino acid residues), that had been used with the Varian version: the Bruker and Varian versions achieved the same level of assignment completeness (98% in 20 h). As a more rigorous evaluation of the Bruker version, we tested a larger protein, BRPF1 bromodomain (114 amino acid residues), which yielded an automated assignment completeness of 86% in 55 h. Both experiments were carried out on a 500 MHz Bruker AVANCE III spectrometer equipped with a z-gradient 5 mm TCI probe. ADAPT-NMR is available at http://pine.nmrfam.wisc.edu/ADAPT-NMR in the form of pulse programs, the two AU programs, and instructions for installation and use.

Lee, Woonghee; Hu, Kaifeng; Tonelli, Marco; Bahrami, Arash; Neuhardt, Elizabeth; Glass, Karen C.; Markley, John L.

2013-11-01

195

Universal quantitative NMR analysis of complex natural samples.  

PubMed

Nuclear Magnetic Resonance (NMR) is a universal and quantitative analytical technique. Being a unique structural tool, NMR also competes with metrological techniques for purity determination and reference material analysis. In pharmaceutical research, applications of quantitative NMR (qNMR) cover mostly the identification and quantification of drug and biological metabolites. Offering an unbiased view of the sample composition, and the possibility to simultaneously quantify multiple compounds, qNMR has become the method of choice for metabolomic studies and quality control of complex natural samples such as foods, plants or herbal remedies, and biofluids. In this regard, NMR-based metabolomic studies, dedicated to both the characterization of herbal remedies and clinical diagnosis, have increased considerably. PMID:24484881

Simmler, Charlotte; Napolitano, José G; McAlpine, James B; Chen, Shao-Nong; Pauli, Guido F

2014-02-01

196

Ischemic intervals during warm blood cardioplegia in the canine heart evaluated by phosphorus 31-magnetic resonance spectroscopy  

Microsoft Academic Search

Objective: Warm blood cardioplegia requires interruption by ischemic intervals to aid visualization. We evaluated the safety of repeated interruption of warm blood cardioplegia by normothermic ischemic periods of varying durations. Methods: In three groups of isolated cross-perfused canine hearts, left ventricular function was measured before and for 2 hours of recovery after arrest, which comprised four 15-minute periods of cardioplegia

Nilto Carias de Oliveira; Theodore J. Boeve; David F. Torchiana; Howard L. Kantor; James S. Titus; Christopher J. Schmidt; Cheng-zai Lu; Jeehyang Kim; Willard M. Daggett; Gillian A. Geffin

1997-01-01

197

Non-Invasive Phosphorus-31 Magnetic Resonance Spectral Characterization of Breast Tissue Anomalies Using Pattern Recognition and Artificial Intelligence.  

National Technical Information Service (NTIS)

It is highly desirable to develop a non-invasive and pattern recognition technique that can detect and reliably interpret images or spectral data from small volumes of the breast. Due to the pervasive nature of breast cancer in society today, and the cons...

D. Buzatu D. Lindquist J. A. Darsey R. Walker S. Harms

2006-01-01

198

Identification of organic phosphorus compounds in the Bronx River bed sediments by phosphorus-31 nuclear magnetic resonance spectroscopy.  

PubMed

Sediment characteristics influence the distribution and bioavailability of phosphorus (P) in rivers and lakes. The objectives of this study were to identify P compounds in sediments collected from 15 sites along the Bronx River to get insights on nutrient transport for management of highly variable and modified ecosystems such as the Bronx River. The nuclear magnetic resonance spectra showed that the dominant P species in Bronx River bed sediments are orthophosphate monoester and lesser phosphate diesters and pyrophosphates (pyro-P). The P compounds were mostly glycerophosphate, nucleoside monophosphates, and polynucleotides. A few sites showed a small amount of dihydroxyacetone phosphate, inosine monophosphate. By allowing a downstream comparison of P compound variations along the Bronx River, this study provides a step toward improving water quality in an urban river system such as New York City and helps to assess the bioavailability of P, in turn, design estuary habitat restoration projects in comparable region of the world. PMID:20013049

Wang, Jingyu; Pant, Hari K

2010-12-01

199

Phosphorus-31 and carbon-13 nuclear magnetic resonance study of glucose and xylose metabolism in agarose-immobilized Candida tropicalis.  

PubMed Central

Candida tropicalis can ferment both hexose and pentose sugars. Here, we have used 31P and 13C nuclear magnetic resonance spectroscopy to study the capacity of this yeast species to metabolize glucose or xylose when immobilized in small (< 1-mm-diameter) agarose beads. Immobilized C. tropicalis metabolizing glucose showed rapid initial growth within the beads. A corresponding drop in the intracellular pH (from 7.8 to 7.25) and hydrolysis of intracellular polyphosphate stores were observed. Although the initial rate of glucose metabolism with immobilized C. tropicalis was similar to the rate observed previously in cell suspensions, a decrease by a factor of 2.5 occurred over 24 h. In addition to ethanol, a significant amount of glycerol was also produced. When immobilized C. tropicalis consumed xylose, cell growth within the beads was minimal. The intracellular pH dropped rapidly by 1.05 pH units to 6.4. Intracellular ATP levels were lower and intracellular Pi levels were higher than observed with glucose-perfused cells. Consumption of xylose by immobilized C. tropicalis was slower than was previously observed for oxygen-limited cell suspensions, and xylitol was the only fermentation product.

Lohmeier-Vogel, E M; Hahn-Hagerdal, B; Vogel, H J

1995-01-01

200

Quantitative NMR spectroscopy--applications in drug analysis.  

PubMed

NMR spectroscopy being a primary ratio method of measurement is highly suitable to evaluate the quality of drugs. NMR spectroscopy can be used for the identification of a drug substance, the identification and quantification of impurities arising from the synthesis pathway and degradation, or residual solvents as well as the determination of the content in the assay. This review gives an overview of the application of quantitative NMR spectroscopy in International Pharmacopoeias and for licensing purposes. PMID:15893899

Holzgrabe, U; Deubner, R; Schollmayer, C; Waibel, B

2005-08-10

201

Fluid-Rock Characterization and Interactions in NMR Well Logging  

SciTech Connect

The objective of this project was to characterize the fluid properties and fluid-rock interactions that are needed for formation evaluation by NMR well logging. The advances made in the understanding of NMR fluid properties are summarized in a chapter written for an AAPG book on NMR well logging. This includes live oils, viscous oils, natural gas mixtures, and the relation between relaxation time and diffusivity.

Hirasaki, George J.; Mohanty, Kishore K.

2003-02-10

202

NMR in rotating magnetic fields: Magic angle field spinning  

Microsoft Academic Search

Magic angle sample spinning has been one of the cornerstones in high-resolution solid state NMR. Spinning frequencies nowadays have increased by at least one order of magnitude over the ones used in the first experiments and the technique has gained tremendous popularity. It is currently a routine procedure in solid-state NMR, high-resolution liquid-state NMR and solid-state MRI. The technique enhances

Dimitris Sakellariou; Carlos A. Meriles; Rachel W. Martin; Alexander Pines

2004-01-01

203

NMR Study on the Acidity of TS1 Zeolite  

Microsoft Academic Search

The acidic properties of TS-1 and Silicalite-1 zeolites have been investigated by the solid-state MAS NMR technique capable of in situ sample pretreatment. As shown by a combination of the 31P MAS NMR and 1H MAS NMR techniques with trimethylphosphine, not only Brønsted acid sites but also Lewis acid sites exist in the TS-1 zeolites. Moreover, TS-1 zeolite is more

Jianqin Zhuang; Zhimin Yan; Xiumei Liu; Xianchun Liu; Xiuwen Han; Xinhe Bao; Ulrich Mueller

2002-01-01

204

NMR of textures in rotating 3He-A  

NASA Astrophysics Data System (ADS)

Four vortex textures in 3He-A, one analytic and three singular, are proposed as possible candidates to explain recent transverse NMR results in the Helsinki rotating cryostat. Although the analytic texture, previously discussed by Seppälä and Volovik, has a transverse NMR shift and absorption closest to the observed values, the agreement with experiment is not wholly satisfactory. Longitudinal NMR shifts and absorption are calculated for the four textures; such measurements might determine which vortex is present.

Vulovic, V. Z.; Stein, D. L.; Fetter, A. L.

1984-06-01

205

Synthesis and Characterization of Amphoteric Ligands Including the Crystal and Molecular Structure of ((Me3SiCH2)2InPPh2)2.  

National Technical Information Service (NTIS)

The new amphoteric ligands (Me3SiCH2)2GaPPh2, (Me3SiCH2)2InPPh2, and (Me3CCH2)2InPPh2 have been prepared and characterized by elemental analyses, cryoscopic molecular weight measurements and Hydrogen 1 NMR, Phosphorus 31 NMR and IR spectroscopic data. An ...

O. T. Beachley J. P. Kopasz H. Zhang W. E. Hunter J. L. Atwood

1986-01-01

206

Crystallographic phasing with NMR models: an envelope approach.  

PubMed

X-ray crystallography and NMR are complementary tools in structural biology. However, it is often difficult to use NMR structures as search models in molecular replacement (MR) to phase crystallographic data. In this study, a new approach is reported utilizing a molecular envelope of NMR structures for MR phasing with the program FSEARCH at low resolution (about 6?Å). Several targets with both crystallographic and NMR structures available have been tested. FSEARCH was able to find the correct translation and orientation of the search model in the crystallographic unit cell, while conventional MR procedures were unsuccessful. PMID:25004974

Zhang, Weizhe; Zhang, Tao; Zhang, Hongmin; Hao, Quan

2014-07-01

207

Laser-enhanced NMR spectroscopy: Theoretical considerations  

SciTech Connect

W. S. Warren et al. report that the proton magnetic resonance spectra of chiral molecules are modified slightly by circularly polarized laser light. While it is not unexpected that circularly polarized radiation can influence chiral molecules, the large magnitude of the reported results is surprising. From conservation of parity, and under the conditions of the experiment, the relevant energy shifts per randomly oriented molecule show several simple relations. The chemical shielding of a chiral molecule in right circularly polarized light must be the same as its enantiomer in left circularly polarized light. However, the splitting of nuclear magnetic resonance (NMR) lines in left circular polarization will not necessarily equal that for right circular polarization because of the zero magnetic field term, b[sup 0]I[sub 0]. Direct calculation using the standard Hamiltonian descriptive of the interaction between radiation and matter in a magnetic field shows that for light intensities of 10 W cm[sup [minus]2] the nonchiral chemical shift in the NMR spectrum should yield a value of aI[sub 0] on the order of 10[sup [minus]15] [sigma][sub 0]. The chiral chemical shift, bI[sub 0], is on the order of 10[sup [minus]18] [sigma][sub 0]; for a magnetic field of 10[sup 4] gauss, this intensity-dependent shift corresponds to about 10[sup [minus]15] Hz. The zero magnetic field shift (b[sup 0]I[sub 0]) is about 10[sup [minus]10]Hz. In conclusion, the ordinary manifestation of chirality on light-perturbed chemical shifts is too small to be observed. Shining laser light on a racemic mixture and seeing a single NMR line split into two lines would provide a convincing experimental result. The authors' calculations predict that it will not occur. 3 refs., 1 tab.

Harris, R.A.; Tinoco, I. Jr. (Univ. of California, Berkeley (United States))

1993-02-05

208

Analysis of multiple pulse NMR in solids  

NASA Technical Reports Server (NTRS)

The general problems associated with the removal of the effects of dipolar broadening from solid-state NMR spectra are analyzed. The effects of finite pulse width and H sub 1 inhomogeneity are shown to have limited the resolution of previous pulse cycles, and a new eight-pulse cycle designed to minimize these problems is discussed. Spectra for F-19 in CaF2 taken with this cycle are presented which show residual linewidth near 10 Hz. The feasibility of measuring proton chemical shift tensors is discussed.

Rhim, W.-K.; Elleman, D. D.; Vaughan, R. W.

1973-01-01

209

NMR-based quantification of organic diphosphates  

PubMed Central

Phosphorylated compounds are ubiquitous in life. Given their central role, many such substrates and analogues have been prepared for subsequent evaluation. Prior to biological experiments, it is typically necessary to determine the concentration of the target molecule in solution. Here we describe a method where concentrations of stock solutions of organic diphosphates and bisphosphonates are quantified using 31P NMR spectroscopy with standard instrumentation using a capillary tube with a secondary standard. The method is specific and is applicable down to a concentration of 200 ?M. The capillary tube provides the reference peak for quantification and deuterated solvent for locking.

Lenevich, Stepan

2010-01-01

210

Characterization of a paracetamol metabolite using on-line LC-SPE-NMR-MS and a cryogenic NMR probe  

Microsoft Academic Search

In this study, the hyphenation of LC-SPE-NMR-MS at 500MHz was applied to the structural elucidation of a low concentrated paracetamol metabolite present in human urine. Single or multiple peak trapping of the mass detected metabolite on SPE cartridges was employed to increase the sensitivity and quality NMR measurement over the conventional LC-NMR method. After the elution of the metabolite from

Markus Godejohann; Li-Hong Tseng; Ulrich Braumann; Jens Fuchser; Manfred Spraul

2004-01-01

211

Rapid NMR imaging using stimulated echoes  

NASA Astrophysics Data System (ADS)

Rapid NMR imaging with measuring times of the order of 200 ms (32 × 64 pixels) to 1 s (128 × 128 pixels) is demonstrated for the first time using a superconducting magnet supplied with a commercial gradient system. The technique is a simple extension of STEAM ( stimulated echo acquisition mode) imaging recently presented in this journal. In the basic 90°- t1-90°- t2-90°- t3 STEAM experiment, a single stimulated echo (STE) is recorded at t3 = t1. For rapid imaging the final part of the sequence, i.e., the 90°- t3(STE) period, is replaced by a series of acquisition periods with small angle pulses. Each of these pulses "reads" only a small part of the longitudinal magnetization prepared by the two leading 90° pulses. Application of a different phase-encoding gradient for each STE signal yields, after Fourier transformation, a series of projections sufficient for reconstruction of an image using a standard 2D FT algorithm. Since the entire acquisition time of the rapid STEAM imaging sequence is limited only by the T1 relaxation process, and since further the rf power deposition is considerably lower than for a multiple spin-echo sequence, the method is particularly suitable for high-field NMR imaging. 1H images of phantoms and human extremities have been obtained at 100 MHz using a 2.3 T magnet with a bore of 40 cm.

Frahm, J.; Haase, A.; Matthaei, D.; Merboldt, K.-D.; Hänicke, W.

212

Flow NMR imaging using stimulated echoes  

NASA Astrophysics Data System (ADS)

A new imaging method is described which allows a noninvasive determination of flow velocities by taking advantage of the stimulated-echo (STE) NMR signal. The method is a time-of-flight measurement of spins moving between excitation and detection. For this purpose the first and the third pulse of a STEAM ( stimulated- echo acquisition mode) sequence 90°- t1-90°- t2-90°- t3 are taken to be slice selective defining the tagging and target slice, respectively. Obviously, only those spins give rise to a STE signal that are affected by all three pulses, i.e., that are moving from the position of the tagging slice to the position of the target slice. For the determination of flow velocities the inflow of tagged spins is probed by recording images of the same target slice at different times in a single experiment. Flow directions are easily detected in the same experiment by using two target slices having different positions with respect to the tagging slice. In addition the distance between tagging and target slice may be varied in a number of experiments. Experimental results are presented for 1H NMR flow measurements of a phantom.

Derboldt, Klaus-Dietmar; Hänicke, Wolfgang; Frahm, Jens

213

NMR measurements in solutions of dialkylimidazolium haloaluminates  

SciTech Connect

{sup 27}Al and {sup 35}Cl NMR spectra of AlCl{sub 3}-1-ethyl-3-methyl imidazolium chloride (EMIC) melts were measured for initial compositions ranging from 50 to 67 mol % AlCl{sub 3} at various temperatures. It was shown by changing the preaquisition delay time (DE value) that the dominant aluminum species are AlCl{sub 4}{sup {minus}} in the melt formed by mixing 50 mol % with EMIC and Al{sub 2}Cl{sub 7}{sup {minus}} in the 67 mol % AlCl{sub 3} melt. In the equimolar mixture, the chemical shift of {sup 27}Al NMR spectrum is 103.28 ppm and the line width is 22.83Hz. In the 67 mol % AlCl{sub 3} mixture, the chemical shift is 103.41 ppm and the line width is 2624Hz. A third species observed at 97 ppm in the {sup 27}Al spectra for the 55 and 60 mol % AlCl{sub 3} mixtures is identified to be a product of the reaction with residual water. The relaxation rates for each species in the melts were determined.

Takahashi, S.; Saboungi, M.L.; Klingler, R.J.; Chen, M.J.; Rathke, J.W.

1992-06-01

214

The D0 solenoid NMR magnetometer  

SciTech Connect

A field monitoring system for the 2 Tesla Solenoid of the D0 detector is described. It is comprised of a very small NMR probe cabled to a DSP based signal processing board. The design magnetic field range is from 1.0 to 2.2 Tesla, corresponding to an RF frequency range of 42.57 to 93.67 MHz. The desired an accuracy is one part in 10{sup 5}. To minimize material in the interaction region of the D0 detector, the overall thickness of the NMR probe is 4 mm, including its mounting plate, and its width is 10 mm. To minimize cable mass, 4mm diameter IMR-100A cables are used for transmitting the RF signals from a nearby patch panel 25 meters to each of four probes mounted within the bore of the solenoid. RG213U cables 45 meters long are used to send the RF from the movable counting house to the patch panel. With this setup, the detector signal voltage at the moving counting room is in the range of 250-400 mV.

Sten Uldall Hansen Terry Kiper, Tom Regan, John Lofgren et al.

2002-11-20

215

Inductive shielding of NMR phase noise  

NASA Astrophysics Data System (ADS)

We report on a solution to the problem of phase noise in nuclear magnetic resonance (NMR) experiments. Phase noise refers to the variation in the phases of NMR signals from successive acquisitions due to an unstable applied field. Such a situation exists in high-field resistive Bitter magnets and, for sufficiently long timescales, can cause serious signal degradation upon signal averaging. An inductive shield, formed by a highly conducting metal tube placed around the sample and along the applied field, provides screening of the AC components of the applied field and thereby retains phase coherence over long periods. Although simple in principle there are technical difficulties for practical implementation of this method. We present demonstrations of the utility of this approach. In particular, we show a significant extension of the effective transverse coherence time of the 13C resonance in doubly 13C-labeled glycerol in a resistive Bitter magnet. This was accomplished through the use of a highly conducting aluminum shield, cooled to 4 K with liquid helium.

Sigmund, E. E.; Mitrovi?, V. F.; Calder, E. S.; Thomas, G. W.; Bachman, H. N.; Halperin, W. P.; Kuhns, P. L.; Reyes, A. P.

2002-12-01

216

Algorithmic cooling and scalable NMR quantum computers  

PubMed Central

We present here algorithmic cooling (via polarization heat bath)—a powerful method for obtaining a large number of highly polarized spins in liquid nuclear-spin systems at finite temperature. Given that spin-half states represent (quantum) bits, algorithmic cooling cleans dirty bits beyond the Shannon's bound on data compression, by using a set of rapidly thermal-relaxing bits. Such auxiliary bits could be implemented by using spins that rapidly get into thermal equilibrium with the environment, e.g., electron spins. Interestingly, the interaction with the environment, usually a most undesired interaction, is used here to our benefit, allowing a cooling mechanism. Cooling spins to a very low temperature without cooling the environment could lead to a breakthrough in NMR experiments, and our “spin-refrigerating” method suggests that this is possible. The scaling of NMR ensemble computers is currently one of the main obstacles to building larger-scale quantum computing devices, and our spin-refrigerating method suggests that this problem can be resolved.

Boykin, P. Oscar; Mor, Tal; Roychowdhury, Vwani; Vatan, Farrokh; Vrijen, Rutger

2002-01-01

217

NMR investigation of iron-based superconductors  

NASA Astrophysics Data System (ADS)

We report NMR investigation of the electronic properties of iron-based superconductors with primary focus on the 11 (FeSe) and 122 (Co-doped BaFe2As2) systems. From the ^77Se and ^75As NMR Knight shift K measurements, we will deduce the intrinsic temperature and concentration dependences of the uniform spin susceptibility, ?spin, in these systems. We will also demonstrate the evolution of antiferromagnetic spin fluctuations (AFSF) as a function of pressure (in FeSe) or the doping level (in Ba[Fe1-xCox]2As2). Our results show that the optimal superconducting phase exists in close proximity with SDW order; superconductivity sets in only after AFSF grow toward Tc. This work was carried out in collaboration with F.L. Ning and K. Ahilan (McMaster), T. McQueen and R.J. Cava (Princeton), A.S. Sefat, M.A. McGuire, B. C. Sales, and D. Mandrus (Oak Ridge), P. Cheng, B. Shen, and H.-H Wen (Chinese Academy of Sciences). The work at McMaster was supported by NSERC, CIFAR, and CFI.

Imai, Takashi

2010-03-01

218

NMR spectroscopy on domain dynamics in biomacromolecules.  

PubMed

Domain dynamics in biomacromolecules is currently an area of intense research because of its importance for understanding the huge quantity of available data relating the structure and function of proteins and nucleic acids. Control of structural flexibility is essential for the proper functioning of the biomacromolecules. Biophysical discoveries as well as computational algorithms and databases have reshaped our understanding of the often spectacular domain dynamics. At the residue level, such flexibility occurs due to local relaxation of peptide bond angles whose cumulative effect results in large changes in the secondary, tertiary or quaternary structures. The flexibility, or its absence, most often depends on the nature of interdomain linkages. Both the flexible and relatively rigid linkers are found in many multidomain biomacromolecules. Large-scale structural heterogeneity of multidomain biomacromolecules and their complexes is now seen as the norm rather than the exception. Absence of such motion, as in the so-called molecular rulers, also has desirable functional effects in architecture of biomacromolecules. The contemporary methods of NMR spectroscopy are capable to provide the detailed information on domain motions in biomacromolecules in the wide range of timescales related to the timescales of their functioning. We review here the current point of view on the nature of domain motions based on these last achievements in the field of NMR spectroscopy. Experimental and theoretical aspects of the collective intra- and interdomain motions are considered. PMID:23684958

Shapiro, Yury E

2013-08-01

219

7 CFR 1755.704 - Requirements applicable to both CCSR and NMR aerial service wires.  

Code of Federal Regulations, 2010 CFR

...Requirements applicable to both CCSR and NMR aerial service wires. 1755.704 Section...Requirements applicable to both CCSR and NMR aerial service wires. (a) Acceptance...Each conductor in the completed CCSR and NMR aerial service wire shall...

2010-01-01

220

7 CFR 1755.704 - Requirements applicable to both CCSR and NMR aerial service wires.  

Code of Federal Regulations, 2010 CFR

...Requirements applicable to both CCSR and NMR aerial service wires. 1755.704 Section...Requirements applicable to both CCSR and NMR aerial service wires. (a) Acceptance...Each conductor in the completed CCSR and NMR aerial service wire shall...

2009-01-01

221

Functional Dynamics of Response Regulators Using NMR Relaxation Techniques  

Microsoft Academic Search

A fundamental concept of phosphorylation?mediated signaling is the precise switching between discrete functional conformations. According to the traditional view, phosphorylation induces a new, active conformation. In this chapter, a series of NMR experiments performed on a response regulator are described that challenge this traditional notion. The combination of NMR relaxation experiments with chemical shift data and the linkage to structure\\/function

Alexandra K. Gardino; Dorothee Kern

2007-01-01

222

Rapid prediction of multi-dimensional NMR data sets.  

PubMed

We present a computational environment for Fast Analysis of multidimensional NMR DAta Sets (FANDAS) that allows assembling multidimensional data sets from a variety of input parameters and facilitates comparing and modifying such "in silico" data sets during the various stages of the NMR data analysis. The input parameters can vary from (partial) NMR assignments directly obtained from experiments to values retrieved from in silico prediction programs. The resulting predicted data sets enable a rapid evaluation of sample labeling in light of spectral resolution and structural content, using standard NMR software such as Sparky. In addition, direct comparison to experimental data sets can be used to validate NMR assignments, distinguish different molecular components, refine structural models or other parameters derived from NMR data. The method is demonstrated in the context of solid-state NMR data obtained for the cyclic nucleotide binding domain of a bacterial cyclic nucleotide-gated channel and on membrane-embedded sensory rhodopsin II. FANDAS is freely available as web portal under WeNMR ( http://www.wenmr.eu/services/FANDAS ). PMID:23143278

Gradmann, Sabine; Ader, Christian; Heinrich, Ines; Nand, Deepak; Dittmann, Marc; Cukkemane, Abhishek; van Dijk, Marc; Bonvin, Alexandre M J J; Engelhard, Martin; Baldus, Marc

2012-12-01

223

Simulation of the Burgers equation by NMR quantum information processing  

Microsoft Academic Search

We report on the implementation of Burgers equation as a type-II quantum computation on an NMR quantum information processor. Since the flow field evolving under the Burgers equation develops sharp features over time, this is a better test of liquid state NMR implementations of type-II quantum computers than the previous examples using the diffusion equation. In particular, we show that

Zhiying Chen; Jeffrey Yepez; David G. Cory

2004-01-01

224

Laser Heated Gradient NMR Studies of Ceramic Liquids.  

National Technical Information Service (NTIS)

We report progress in two areas of research on NMR of ceramic liquids: the synthesis and characterization of new materials along La-monazite - alumina/CaO joins, and the 27Al NMR measurement of incoherent Al motions in aluminum-containing ceramic melts. T...

R. F. Marzke, G. H. Wolf

2004-01-01

225

Chemical Equilibrium in Supramolecular Systems as Studied by NMR Spectrometry  

ERIC Educational Resources Information Center

Undergraduate students are required to study the chemical balance in supramolecular assemblies constituting two or more interacting species, by using proton NMR spectrometry. A good knowledge of physical chemistry, fundamentals of chemical balance, and NMR are pre-requisites for conducting this study.

Gonzalez-Gaitano, Gustavo; Tardajos, Gloria

2004-01-01

226

Web Spectra: Problems in NMR and IR spectroscopy  

NSDL National Science Digital Library

This site was established to provide chemistry students with a library of spectroscopy problems. Interpretation of spectra is a technique that requires practice - this site provides 1H NMR and 13 C NMR, DEPT, COSY and IR spectra of various compounds for students to interpret. Hopefully, these problems will provide a useful resource to better understand spectroscopy.

Merlic, Craig A.

2008-02-29

227

Fast automated NMR spectroscopy of short-lived biological samples.  

PubMed

Faster than death: NMR techniques that make use of nonlinear sampling and hyperdimensional processing enable the recording of complete NMR data sets for the automated assignment of the backbone and side-chain resonances of short-lived protein samples of cell lysates. PMID:22492650

Tikole, Suhas; Jaravine, Victor; Rogov, Vladimir V; Rozenknop, Alexis; Schmöe, Kerstin; Löhr, Frank; Dötsch, Volker; Güntert, Peter

2012-05-01

228

Studying the pore space of cuttings by NMR and ?CT  

NASA Astrophysics Data System (ADS)

Evaluating the formation quality by deriving porosity, pore size, and permeability from cuttings instead of drill cores is a promising and challenging field of research established in the past decade. Challenges with cuttings are their small and irregular size rendering them unsuitable for e.g. standard permeability measurements. Permeability can be estimated from nuclear magnetic resonance (NMR) measurements. NMR measurements on cuttings are especially challenging 1) because the total NMR signal is very low due to small sample sizes and 2) because the high ratio of outer surface to volume leads to a significant contribution of interstitial water to the NMR signal, which thus distorts the informative NMR signal from within the pore space. The aim of the study is to evaluate the use of NMR in combination with micro-computed tomography (?CT) as a method to determine the pore space characteristics of small drill cuttings from the Bückeberg Formation (German Wealden). After accurate removal of interstitial water and a CT based sorting, it was possible to measure NMR signals representative for the individual pore sizes. The representiveness of the measured values was verified by simulations of the NMR signals in pore spaces determined via ?CT. Porosity, relaxation time distributions, and permeability were calculated for cuttings assemblages with large, medium, small, and very small pores.

Hübner, Wiete

2014-05-01

229

Metabolite fingerprinting and profiling in plants using NMR  

Microsoft Academic Search

Although less sensitive than mass spectrometry (MS), nuclear magnetic resonance (NMR) spectroscopy pro- vides a powerful complementary technique for the identification and quantitative analysis of plant metab- olites either in vivo or in tissue extracts. In one approach, metabolite fingerprinting, multivariate anal- ysis of unassigned 1H NMR spectra is used to compare the overall metabolic composition of wild-type, mutant, and

P. Krishnan; N. J. Kruger; R. G. Ratcliffe

2010-01-01

230

Probe for high resolution NMR with sample reorientation  

DOEpatents

An improved NMR probe and method are described which substantially improve the resolution of NMR measurements made on powdered or amorphous or otherwise orientationally disordered samples. The apparatus mechanically varies the orientation of the sample such that the time average of two or more sets of spherical harmonic functions are zero.

Pines, Alexander (Berkeley, CA); Samoson, Ago (Tallinn, SU)

1990-01-01

231

Two-dimensional NMR spectroscopy. Applications for chemists and biochemists  

SciTech Connect

Two-dimensional nuclear magnetic resonance spectroscopy (2-D NMR) has become a very powerful class of experiments (in the hands of an adept scientist) with broad adaptability to new situations. It is the product of a happy marriage between modern pulse FT-NMR technology, with its large memory and high-speed computers, and the physicists and chemists who love to manipulate spin systems. Basic 2-D experiments are now a standard capability of modern NMR spectrometers, and this timely book intends to make 2-D NMR users of those who are familiar with normal 1-D NMR. The 2-D NMR goal is correlation of the lines of the observed NMR spectrum with other properties of the system. This book deals with applications to high-resolution spectrum analysis, utilizing either coupling between the NMR-active nuclei or chemical exchange to perform the correlation. The coupling can be scalar (through bonds) or direct through space (within 5 A). The coupling may be homonuclear (between like nuclei) or heteronuclear.

Croasmun, W.R.; Carlson, R.M.K.

1987-01-01

232

Principles and Demonstrations of Quantum Information Processing by NMR Spectroscopy  

Microsoft Academic Search

This paper surveys our recent research on quantum infor- mation processing by nuclear magnetic resonance (NMR) spectroscopy. We begin with a geometric introduction to the NMR of an ensemble of indistinguishable spins, and then show how this geometric interpretation is contained within an algebra of multispin product operators. This al- gebra is used throughout the rest of the paper to

Timothy F. Havel; S. S. Somaroo; C.-H. Tseng; D. G. Cory

2000-01-01

233

Application of software defined radio in 500MHz NMR spectrometers  

Microsoft Academic Search

Digital signal processing is one of the most important techniques in 500 MHz NMR spectrometers. Free Induction Decay (FID) signal should be quadrature-demodulated from 20 MHz intermediate frequency (IF) signal, decimated to a user-defined sample rate and spectrum width. In the design of digital processor of NMR spectrometer console, the techniques of Software Defined Radio (SDR) are applied to achieve

Minghua Tian; Hongfei Liu; Zhong Chen

2009-01-01

234

Version 1.2 of the Crystallography and NMR system  

Microsoft Academic Search

Version 1.2 of the software system, termed Crystallography and NMR system (CNS), for crystallographic and NMR structure determination has been released. Since its first release, the goals of CNS have been (i) to create a flexible computational framework for exploration of new approaches to structure determination, (ii) to provide tools for structure solution of difficult or large structures, (iii) to

Axel T Brunger

2007-01-01

235

H NMR Study of Some Thiosalicylic Acid Complexes  

Microsoft Academic Search

Five thiosalicylic acid (TSA) complexes were prepared. The H NMR of these complexes were recorded and analysed. It was found that molybdenum, arsenic, selenium, silver and tellurium metals coordinates through the sulfur atom. The H NMR chemical shift of ring protons of As, Se and Te shift to low field upon complexation, while it shifts to high field when TSA

I. M. Al-daher; S. R. Salman; M. A. Noori

1990-01-01

236

Fluid-Rock Characterization and Interactions in NMR Well Logging  

SciTech Connect

The objective of this report is to characterize the fluid properties and fluid-rock interactions that are needed for formation evaluation by NMR well logging. The advances made in the understanding of NMR fluid properties are summarized in a chapter written for an AAPG book on NMR well logging. This includes live oils, viscous oils, natural gas mixtures, and the relation between relaxation time and diffusivity. Oil based drilling fluids can have an adverse effect on NMR well logging if it alters the wettability of the formation. The effect of various surfactants on wettability and surface relaxivity are evaluated for silica sand. The relation between the relaxation time and diffusivity distinguishes the response of brine, oil, and gas in a NMR well log. A new NMR pulse sequence in the presence of a field gradient and a new inversion technique enables the T{sub 2} and diffusivity distributions to be displayed as a two-dimensional map. The objectives of pore morphology and rock characterization are to identify vug connectivity by using X-ray CT scan, and to improve NMR permeability correlation. Improved estimation of permeability from NMR response is possible by using estimated tortuosity as a parameter to interpolate between two existing permeability models.

George J. Hirasaki; Kishore K. Mohanty

2005-09-05

237

Automated Microflow NMR: Routine Analysis of Five-Microliter Samples  

PubMed Central

A microflow CapNMR probe double-tuned for 1H and 13C was installed on a 400-MHz NMR spectrometer and interfaced to an automated liquid handler. Individual samples dissolved in DMSO-d6 are submitted for NMR analysis in vials containing as little as 10 ?L of sample. Sets of samples are submitted in a low-volume 384-well plate. Of the 10 ?L of sample per well, as with vials, 5 ?L is injected into the microflow NMR probe for analysis. For quality control of chemical libraries, 1D NMR spectra are acquired under full automation from 384-well plates on as many as 130 compounds within 24 h using 128 scans per spectrum and a sample-to-sample cycle time of ?11 min. Because of the low volume requirements and high mass sensitivity of the microflow NMR system, 30 nmol of a typical small molecule is sufficient to obtain high-quality, well-resolved, 1D proton or 2D COSY NMR spectra in ?6 or 20 min of data acquisition time per experiment, respectively. Implementation of pulse programs with automated solvent peak identification and suppression allow for reliable data collection, even for samples submitted in fully protonated DMSO. The automated microflow NMR system is controlled and monitored using web-based software.

Jansma, Ariane; Chuan, Tiffany; Geierstanger, Bernhard H.; Albrecht, Robert W.; Olson, Dean L.; Peck, Timothy L.

2006-01-01

238

Straightforward and complete deposition of NMR data to the PDBe  

PubMed Central

We present a suite of software for the complete and easy deposition of NMR data to the PDB and BMRB. This suite uses the CCPN framework and introduces a freely downloadable, graphical desktop application called CcpNmr Entry Completion Interface (ECI) for the secure editing of experimental information and associated datasets through the lifetime of an NMR project. CCPN projects can be created within the CcpNmr Analysis software or by importing existing NMR data files using the CcpNmr FormatConverter. After further data entry and checking with the ECI, the project can then be rapidly deposited to the PDBe using AutoDep, or exported as a complete deposition NMR-STAR file. In full CCPN projects created with ECI, it is straightforward to select chemical shift lists, restraint data sets, structural ensembles and all relevant associated experimental collection details, which all are or will become mandatory when depositing to the PDB. Instructions and download information for the ECI are available from the PDBe web site at http://www.ebi.ac.uk/pdbe/nmr/deposition/eci.html. Electronic supplementary material The online version of this article (doi:10.1007/s10858-010-9439-3) contains supplementary material, which is available to authorized users.

Penkett, Christopher J.; van Ginkel, Glen; Velankar, Sameer; Swaminathan, Jawahar; Ulrich, Eldon L.; Mading, Steve; Stevens, Tim J.; Fogh, Rasmus H.; Gutmanas, Aleksandras; Kleywegt, Gerard J.; Henrick, Kim

2010-01-01

239

NMR spectroscopy of RNA duplexes containing pseudouridine in supercooled water  

Microsoft Academic Search

We have performed NMR experiments in supercooled water in order to decrease the temperature-dependent exchange of protons in RNA duplexes. NMR spectra of aqueous samples of RNA in bundles of narrow capillaries that were acquired at temperatures as low as ---188C reveal resonances of exchangeable protons not seen at higher temperatures. In particular, we detected the imino protons of terminal

KERSTEN T. SCHROEDER; JACK J. SKALICKY; NANCY L. GREENBAUM

2005-01-01

240

Probe for high resolution NMR with sample reorientation  

DOEpatents

An improved NMR probe and method are described which substantially improve the resolution of NMR measurements made on powdered or amorphous or otherwise orientationally disordered samples. The apparatus mechanically varies the orientation of the sample such that the time average of two or more sets of spherical harmonic functions are zero. 8 figs.

Pines, A.; Samoson, A.

1990-02-06

241

Robust quantum information processing with techniques from liquid state NMR  

Microsoft Academic Search

While Nuclear Magnetic Resonance (NMR) techniques are unlikely to lead to a large scale quantum computer they are well suited to investigating basic phenomena and developing new techniques. Indeed it is likely that many existing NMR techniques will find uses in quantum information processing. Here I describe how the composite rotation (composite pulse) method can be used to develop quantum

Jonathan A. Jones

2003-01-01

242

Noise figure characterization of preamplifiers at NMR frequencies  

Microsoft Academic Search

A method for characterizing the noise figure of preamplifiers at NMR frequencies is presented. The noise figure of preamplifiers as used for NMR and MRI detection varies with source impedance and with the operating frequency. Therefore, to characterize a preamplifier's noise behavior, it is necessary to perform noise measurements at the targeted frequency while varying the source impedance with high

J. A. Nordmeyer-Massner; N. de Zanche; K. P. Pruessmann

2011-01-01

243

Noise figure characterization of preamplifiers at NMR frequencies  

Microsoft Academic Search

A method for characterizing the noise figure of preamplifiers at NMR frequencies is presented. The noise figure of preamplifiers as used for NMR and MRI detection varies with source impedance and with the operating frequency. Therefore, to characterize a preamplifier’s noise behavior, it is necessary to perform noise measurements at the targeted frequency while varying the source impedance with high

J. A. Nordmeyer-Massner; N. De Zanche; K. P. Pruessmann

2011-01-01

244

Cultivator for NMR studies of suspended cell cultures.  

PubMed

When nuclear magnetic resonance (NMR) spectroscopy is employed for physiological experiments with suspended cells, providing for adequate nutrient and oxygen delivery is particularly important, because the inherent insensitivity of NMR requires that concentrated cell suspensions be used. In addition, it is desirable to be able to manipulate the growth rate of cells during a NMR experiment. To address these concerns, a continuous cell cultivator that provides convective oxygen and nutrient transport has been constructed for NMR experiments. The NMR detector coil is located within the cultivator volume. The location is advantageous because the rapid exchange of cells in and out of the coil leads to a small apparent spin lattice relaxation time, thus allowing for rapid pulsing and fast signal averaging. In this article we present the physical principles on which the cultivator's design is based. (31)P spectra showing the response of continuously cultivated Saccharomyces cerevisiae cultures to a phosphate bolus and growth rate shift are then given. PMID:18601092

Meehan, A J; Eskey, C J; Domach, M M; Koretsky, A P

1992-12-20

245

NMR-based methods and strategies for drug discovery.  

PubMed

Nuclear Magnetic Resonance (NMR) spectroscopy has long been a favourite tool of chemists interested in host-guest systems because it permits access to a wealth of information about the molecular recognition reaction. NMR has evolved dramatically in the last 15 years and, in parallel with the development of NMR methods for the determination of protein structure, a variety of tools aimed at detecting protein ligand interactions have been proposed and are being now used both in industrial and academic laboratories as valuable tools for structure-based drug discovery. Very recent developments have considerably increased the fraction of therapeutic targets that can be tackled by NMR and significantly reduced the amount of sample required for analysis; in this tutorial review we outline the essential NMR-based techniques and describe some examples of their implementation as part of drug discovery programmes. PMID:14671791

Salvatella, Xavier; Giralt, Ernest

2003-11-01

246

Membrane Protein Structure and Dynamics from NMR Spectroscopy  

PubMed Central

We review the current state of membrane protein structure determination using solid-state nuclear magnetic resonance (NMR) spectroscopy. Multidimensional magic-angle-spinning correlation NMR combined with oriented-sample experiments has made it possible to measure a full panel of structural constraints of membrane proteins directly in lipid bilayers. These constraints include torsion angles, interatomic distances, oligomeric structure, protein dynamics, ligand structure and dynamics, and protein orientation and depth of insertion in the lipid bilayer. Using solid-state NMR, researchers have studied potassium channels, proton channels, Ca2+ pumps, G protein–coupled receptors, bacterial outer membrane proteins, and viral fusion proteins to elucidate their mechanisms of action. Many of these membrane proteins have also been investigated in detergent micelles using solution NMR. Comparison of the solid-state and solution NMR structures provides important insights into the effects of the solubilizing environment on membrane protein structure and dynamics.

Hong, Mei; Zhang, Yuan; Hu, Fanghao

2014-01-01

247

Studies of organic paint binders by NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance spectroscopy is applied to the study of aged binding media used in paintings, namely linseed oil, egg tempera and an acrylic medium. High resolution 1D and 2D NMR experiments establish the state of hydrolysis and oxidation of the linseed and egg tempera binders after five years of aging, by determining several markers sensitive to the hydrolytic and oxidative processes of the binder lipid fraction. The composition of the acrylic binder co-polymer is determined by 2D NMR spectroscopy, while the identification of a surfactant, poly(ethylene glycol), found in greater amounts in aged acrylic medium, is reported. The non-destructive nature of the proposed analytical NMR methodology, and minimization of the amount of binder material needed through the use of sophisticated cryoprobes and hyphenated LC-NMR techniques, make NMR attractive for the arts analyst, in view of its rapid nature and experimental simplicity.

Spyros, A.; Anglos, D.

2006-06-01

248

?: a Quantitative Measure of NMR Signal Receiving Efficiency  

PubMed Central

Recognizing that the sensitivity of NMR is influenced by factors such as conductance and dielectric constant of the sample, we propose the receiving efficiency ? to characterize how efficiently the NMR signal can be observed from a unit transverse magnetization in a sample under optimal probe tuning and matching conditions. Conveniently, the relative receiving efficiency can be defined as the ratio of the NMR signal induced by a unit transverse magnetization in a sample of interest and a reference solution. Based on the reciprocal relationship between excitation and observation in NMR, the relative receiving efficiency can be correlated with the 90° pulse length (?90). In the special case of perfect probe tuning (impedance matched to 50 ?), ? is inversely proportional to ?90. Application of the NMR receiving efficiency in quantitative analysis potentially enables a single external concentration reference for almost any sample, eliminating the need to know its exact chemical composition or detailed electromagnetic properties.

Mo, Huaping; Harwood, John; Zhang, Shucha; Xue, Yi; Santini, Robert; Raftery, Daniel

2009-01-01

249

1H and 13C NMR data to aid the identification and quantification of residual solvents by NMR spectroscopy.  

PubMed

We present reference data and a javascript web page which allow the rapid identification and quantification of residual solvents by NMR. The data encompass all of the ICH-prescribed solvents and were obtained for a number of NMR solvents. We also present an example of its application. PMID:15809983

Jones, Ian C; Sharman, Gary J; Pidgeon, Julia

2005-06-01

250

Introducing the gNMR Program in an Introductory NMR Spectrometry Course to Parallel Its Use by Spectroscopists  

ERIC Educational Resources Information Center

An approach that is useful to any introductory nuclear magnetic resonance (NMR) spectroscopy course is developed. This approach to teaching NMR spectrometry includes spectral simulation along with the traditional elements of hands-on instrument use and structure elucidation to demonstrate the connection between simulating a spectrum and structure…

Rummey, Jackie M.; Boyce, Mary C.

2004-01-01

251

Double Quantum Filtered NMR Spectroscopy and Imaging  

NASA Astrophysics Data System (ADS)

As a result of the anisotropic motion of water molecules interacting with ordered biological tissues the proton-proton dipolar interaction and the deuteron quadrupolar interaction do not average to zero leaving some residual splittings. The technique of double quantum filtered (DQF) NMR capitalizes on this phenomenon, opening new possibilities to probe biological processes and to obtain a new kind of contrast in MRI. In the talk new applications of the DQF pulse sequences to the study of nerves, enabling the measurement of intercompartmental water exchange in sciatic and optic nerves, the study of the fiber architecture in cartilage under normal, compressed and diseased conditions and the imaging of tendons, enabling the monitoring their healing process following injury.

Navon, Gil

2007-03-01

252

Improved nuclear magnetic resonance apparatus having semitoroidal rf coil for use in topical NMR and NMR imaging  

DOEpatents

An improved nuclear magnetic resonance (NMR) apparatus for use in topical magnetic resonance (TMR) spectroscopy and other remote sensing NMR applications includes a semitoroidal radio frequency (rf) coil. The semitoroidal rf coil produces an effective alternating magnetic field at a distance from the poles of the coil, so as to enable NMR measurements to be taken from selected regions inside an object, particularly including human and other living subjects. The semitoroidal rf coil is relatively insensitive to magnetic interference from metallic objects located behind the coil, thereby rendering the coil particularly suited for use in both conventional and superconducting NMR magnets. The semitoroidal NMR coil can be constructed so that it emits little or no excess rf electric field associated with the rf magnetic field, thus avoiding adverse effects due to dielectric heating of the sample or to any other interaction of the electric field with the sample.

Fukushima, E.; Roeder, S.B.W.; Assink, R.A.; Gibson, A.A.V.

1984-01-01

253

Graph theoretical characterization of NMR groups, nonrigid nuclear spin species and the construction of symmetry adapted NMR spin functions  

NASA Astrophysics Data System (ADS)

NMR group defined by Woodman is shown to be the generalized wreath product group of the NMR graph which is constructed with protons as vertices and edges representing nuclear couplings. The NMR graph can be expressed as a generalized composition of its quotient graph and various types. It is shown that the NMR group is the automorphism group of the NMR graph that preserves the coupling matrix defined here. Using the representation theory of generalized wreath product groups developed in an earlier paper of the present author, the character tables of NMR groups can be obtained. The character tables of certain NMR groups are presented. The quotient graph of the NMR graph is shown to be the composite particle graph. The automorphism group of the quotient NMR graph is the symmetry group of the composite particles, preserving the NMR coupling constants. An iterative algorithm is formulated for obtaining the automorphism group of the composite particle tree. A combinatorial approach is expounded for identifying the nuclear spin species of nonrigid and rigid molecules. The coalescence diagrams describing the effect of nonrigidity on nuclear spin species are introduced and obtained to exemplify the utility of the proposed method. It is shown that using the automorphism group of the quotient graph, the symmetry adapted composite particle spin functions can be constructed. We illustrate this method with 2,3-dimethylbutane. The nuclear spin Hamiltonian matrix of 2,3-dimethylbutane of order 214×214 is reduced to a matrix of order 64×64 by the composite particle method. This matrix can be blocked in the symmetry adapted basis set constructed through the automorphism group of the quotient graph into 40 matrices of order 1×1 and 12 matrices of order 2×2.

Balasubramanian, K.

1980-10-01

254

High-resolution NMR spectroscopy under the fume hood.  

PubMed

This work reports the possibility to acquire high-resolution (1)H NMR spectra with a fist-sized NMR magnet directly installed under the fume hood. The small NMR sensor based on permanent magnets was used to monitor the trimerization of propionaldehyde catalyzed by indium trichloride in real time by continuously circulating the reaction mixture through the magnet bore in a closed loop with the help of a peristaltic pump. Thanks to the chemical selectivity of NMR spectroscopy the progress of the reaction can be monitored on-line by determining the concentrations of both reactant and product from the area under their respective lines in the NMR spectra as a function of time. This in situ measurement demonstrates that NMR probes can be used in chemistry laboratories, e.g. for reaction optimization, or installed at specific points of interest along industrial process lines. Therefore, it will open the door for the implementation of feedback control based on spectroscopic NMR data. PMID:21698335

Küster, Simon K; Danieli, Ernesto; Blümich, Bernhard; Casanova, Federico

2011-08-01

255

Solid-State NMR Studies of Amyloid Fibril Structure  

NASA Astrophysics Data System (ADS)

Current interest in amyloid fibrils stems from their involvement in neurodegenerative and other diseases and from their role as an alternative structural state for many peptides and proteins. Solid-state nuclear magnetic resonance (NMR) methods have the unique capability of providing detailed structural constraints for amyloid fibrils, sufficient for the development of full molecular models. In this article, recent progress in the application of solid-state NMR to fibrils associated with Alzheimer's disease, prion fibrils, and related systems is reviewed, along with relevant developments in solid-state NMR techniques and technology.

Tycko, Robert

2011-05-01

256

Characterization of a chiral nematic mesoporous organosilica using NMR  

NASA Astrophysics Data System (ADS)

Using templation with nanocrystalline cellulose, a mesoporous organosilica film with a chiral nematic pore structure has recently been developed. [1] We have used a variety of Nuclear Magnetic Resonance (NMR) techniques to characterize the pore structure. The pore size distribution has been found by analyzing the freezing point depression of absorbed water via NMR cryoporometry. The effective longitudinal and transverse pore diameters for diffusing water were investigated with Pulsed-Field Gradient (PFG) NMR and compared to a 1-D connected-pore model. Preliminary data on testing imposed chiral ordering in absorbed liquid crystals is also presented. [4pt] [1] K.E. Shopsowitz et al. JACS 134(2), 867 (2012)

Manning, Alan; Shopsowitz, Kevin; Giese, Michael; MacLachlan, Mark; Dong, Ronald; Michal, Carl

2012-10-01

257

77Se-NMR einiger titanocendiselenolen-metallacyclen  

NASA Astrophysics Data System (ADS)

The first 77Se NMR was carried out on a titanocene diselenopyrocatechol derivative with Se bonded directly to the transition metal. Surprisingly, the Ti metallacycle shows, compared with Zr, a reversed shielding effect by proceeding from the non-cyclic Se system to the five-membered Se,Se' co-ordinated heterocycle. This reflects the different bonding system in Ti and Zr bis (cyclopentadienyl) dichalcogenolene complexes. The results are discussed on the basis of the 77Se NMR spectra, the dynamic 1H NMR spectra ( 1H DNMR), and the V. B. and M. O. bonding theories.

Klapötke, Th.

258

Solid State NMR Studies of Amyloid Fibril Structure  

PubMed Central

Current interest in amyloid fibrils stems from their involvement in neurodegenerative and other diseases and from their role as an alternative structural state for many peptides and proteins. Solid state NMR methods have the unique capability of providing detailed structural constraints for amyloid fibrils, sufficient for the development of full molecular models. In this article, recent progress in the application of solid state NMR to fibrils associated with Alzheimer’s disease, prion fibrils, and related systems is reviewed, along with relevant developments in solid state NMR techniques and technology.

Tycko, Robert

2011-01-01

259

Exposing the Moving Parts of Proteins with NMR Spectroscopy  

PubMed Central

Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool for investigating the dynamics of biomolecules since it provides a description of motion that is comprehensive, site-specific, and relatively non-invasive. In particular, the study of protein dynamics has benefited from sustained methodological advances in NMR that have expanded the scope and time scales of accessible motion. Yet, many of these advances may not be well known to the more general physical chemistry community. Accordingly, this Perspective provides a glimpse of some of the more powerful methods in liquid state NMR that are helping reshape our understanding of functional motions of proteins.

Peng, J.W.

2012-01-01

260

Fragment-Based Drug Discovery Using NMR Spectroscopy  

PubMed Central

Nuclear magnetic resonance (NMR) spectroscopy has evolved into a powerful tool for fragment-based drug discovery over the last two decades. While NMR has been traditionally used to elucidate the three-dimensional structures and dynamics of biomacromolecules and their interactions, it can also be a very valuable tool for the reliable identification of small molecules that bind to proteins and for hit-to-lead optimization. Here, we describe the use of NMR spectroscopy as a method for fragment-based drug discovery and how to most effectively utilize this approach for discovering novel therapeutics based on our experience.

Harner, Mary J.; Frank, Andreas O.; Fesik, Stephen W.

2013-01-01

261

13 C NMR and mass spectrometry of soil organic matter  

Microsoft Academic Search

Liquid state, high resolution 13C NMR spectroscopy and mass spectrometry were used to study the composition and structure of soil organic matter (SOM) using\\u000a soil extracts from two long-term experiments at the Rothamsted Experimental Station. Both one- and two-dimensional NMR techniques\\u000a were applied. 13C NMR sub-spectra of the CH\\u000a n\\u000a (n=0...3) groups, obtained by the Distortionless Enhancement by Polarisation Transfer

Galya I. Ivanova; Edward W. Randall

2003-01-01

262

High-field NMR using resistive and hybrid magnets.  

PubMed

Resistive and resistive-superconducting hybrid magnets can generate dc magnetic fields much higher than conventional superconducting NMR magnets but the field spatial homogeneity and temporal stability are usually not sufficient for high-resolution NMR experiments. Hardware and technique development addressing these issues are presented for high-resolution NMR at magnetic fields up to 40T. Passive ferromagnetic shimming and magic-angle spinning are used effectively to reduce the broadening from inhomogeneous magnetic field. A phase correction technique based on simultaneous heteronuclear detection is developed to compensate magnetic field fluctuations to achieve high spectral resolution. PMID:18226940

Gan, Zhehong; Kwak, Hyung-Tae; Bird, Mark; Cross, Timothy; Gor'kov, Peter; Brey, William; Shetty, Kiran

2008-03-01

263

PENDANT 13C NMR Spectroscopy Applied to CHn Groups  

NASA Astrophysics Data System (ADS)

Polarization enhancement nurtured during attached nucleus testing (PENDANT) NMR spectroscopy gives signals of quaternary carbon atoms in addition to signals indicative of CH, CH2 and CH3 groups. In this study, using product operator theory, analytical description of PENDANT NMR spectroscopy for CHn (ISn, I = 1/2, S = 1/2, n = 0, 1, 2, 3) spin systems are presented. Simulation and experimental results of PENDANT NMR spectroscopy are also presented. Theoretical results are found to be in exact agreement with the simulation results and in good agreement with the experimental ones.

Gençten, Azmi; Šaka, Irfan; Gümüš, Sedat

2006-05-01

264

NMR imaging of components and materials for DOE application  

SciTech Connect

The suitability for using NMR imaging to characterize liquid, polymeric, and solid materials was reviewed. The most attractive applications for NMR imaging appear to be liquid-filled porous samples, partially cured polymers, adhesives, and potting compounds, and composite polymers/high explosives containing components with widely varying thermal properties. Solid-state NMR line-narrowing and signal-enhancing markedly improve the imaging possibilities of true solid and materials. These techniques provide unique elemental and chemical shift information for highly complex materials and complement images with similar spatial resolution, such as X-ray computed tomography (CT).

Richardson, B.R.

1993-12-01

265

Fragment-based drug discovery using NMR spectroscopy.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy has evolved into a powerful tool for fragment-based drug discovery over the last two decades. While NMR has been traditionally used to elucidate the three-dimensional structures and dynamics of biomacromolecules and their interactions, it can also be a very valuable tool for the reliable identification of small molecules that bind to proteins and for hit-to-lead optimization. Here, we describe the use of NMR spectroscopy as a method for fragment-based drug discovery and how to most effectively utilize this approach for discovering novel therapeutics based on our experience. PMID:23686385

Harner, Mary J; Frank, Andreas O; Fesik, Stephen W

2013-06-01

266

Capillary toroid cavity detector for high pressure NMR  

DOEpatents

A Toroid Cavity Detector (TCD) is provided for implementing nuclear magnetic resonance (NMR) studies of chemical reactions under conditions of high pressures and temperatures. A toroid cavity contains an elongated central conductor extending within the toroid cavity. The toroid cavity and central conductor generate an RF magnetic field for NMR analysis. A flow-through capillary sample container is located within the toroid cavity adjacent to the central conductor to subject a sample material flowing through the capillary to a static magnetic field and to enable NMR spectra to be recorded of the material in the capillary under a temperature and high pressure environment.

Gerald, II, Rex E. (Brookfield, IL); Chen, Michael J. (Downers Grove, IL); Klingler, Robert J. (Glenview, IL); Rathke, Jerome W. (Honer Glen, IL); ter Horst, Marc (Chapel Hill, NC)

2007-09-11

267

NMR Studies of Protein Structure and Dynamics  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. This thesis describes applications of 2D homonuclear NMR techniques to the study of protein structure and dynamics in solution. The sequential assignments for the 3G-residue bovine Pancreatic Polypeptide (bPP) are reported. The secondary and tertiary structure of bPP in solution has been determined from experimental NMR data. bPP has a well defined C-terminal alpha-helix and a rather ordered conformation in the N-terminal region. The two segments are joined by a turn which is poorly defined. Both the N- and the C-terminus are highly disordered. The mean solution structure of bPP is remarkably similar to the crystal structure of avian Pancreatic Polypeptide (aPP). The average conformations of most side-chains from the alpha-helix of bPP in solution are closely similar to those of aPP in the crystalline state. A large number of side-chains of bPP, however, show significant conformational averaging in solution. The 89-residue kringle domain of urokinase from both human and recombinant sources has been investigated. Sequential assignments based primarily on the recombinant sample and the determination of secondary structure are presented. Two helices have been identified; one of these corresponds to that reported for t-PA kringle 2, but does not exist in other kringles with known structures. The second helix is thus far unique to the urokinase kringle. Three antiparallel beta-sheets and three tight turns have also been identified. The tertiary fold of the molecule conforms broadly to that found for other kringles. Three regions in the urokinase kringle exhibit high local mobility; one of these, the Pro56-Pro62 segment, forms part of the proposed binding site. The other two mobile regions are the N- and C-termini which are likely to form the interfaces between the kringle and the other two domains (EGF and protease) in urokinase. The differential dynamic behaviours of the kringle and protease domains in urokinase have been analysed through calculations of the transverse relaxation and lineshapes of resolved methyl resonances in the intact urokinase spectra. The study has provided strong evidence of large domain mobility between the kringle and protease domains. The results are in good agreement with those obtained from simulations of 2D cross peaks in the aromatic region of the spectra. Similar results are also obtained from calculations applied to miniplasminogen. It appears therefore that the mobility and structural independence between the kringle and protease domains might be a general feature of fibrinolytic proteins.

Li, Xiang

268

Development of A 600 MHz wide bore (89 mm) NMR system using internal tin wires  

Microsoft Academic Search

Employing high performance internal-tin Nb3Sn superconducting wire in NMR superconducting magnets, it is possible to reduce NMR magnet system cost. A 600 MHz NMR magnet system with 89 mm room temperature bore has been designed, constructed and is being tested. The magnet and cryostat were designed to meet existing 600 MHz NMR superconducting magnet standards. The design involved extensive mechanical

Weijun Shen; M. Coffey; Wayne McGhee

2001-01-01

269

A Quantitative Scale of Electron Acceptor Strengths from F - NMR.  

National Technical Information Service (NTIS)

The NMR shielding effect of the fluorine atom in pfluorobenzonitrile served as the basis of preliminary studies directed toward the establishment of an 'intrinsic' scale of electron acceptor strengths of a series of Lewis acids.

R. W. Taft J. W. Carten

1964-01-01

270

A Demonstration of Imaging on an NMR Spectrometer.  

ERIC Educational Resources Information Center

Described is a simple demonstration that relates the techniques of magnetic resonance imaging (MRI) used in medicine and nuclear magnetic resonance (NMR) spectroscopy. Included are materials, procedures, and probable results. (KR)

Hull, L. A.

1990-01-01

271

Proton NMR Spectra: Deceptively Simple and Deceptively Complex Examples.  

ERIC Educational Resources Information Center

Describes relatively simple nuclear magnetic resonance (NMR) experiments that demonstrate unexpected results of the deceptively simple and deceptively complex types. Background information, experimental procedures, and typical results obtained are included. (JN)

Gurst, J. E.; And Others

1985-01-01

272

Study of molecular interactions with 13C DNP-NMR  

NASA Astrophysics Data System (ADS)

NMR spectroscopy is an established, versatile technique for the detection of molecular interactions, even when these interactions are weak. Signal enhancement by several orders of magnitude through dynamic nuclear polarization alleviates several practical limitations of NMR-based interaction studies. This enhanced non-equilibrium polarization contributes sensitivity for the detection of molecular interactions in a single NMR transient. We show that direct 13C NMR ligand binding studies at natural isotopic abundance of 13C gets feasible in this way. Resultant screens are easy to interpret and can be performed at 13C concentrations below ?M. In addition to such ligand-detected studies of molecular interaction, ligand binding can be assessed and quantified with enzymatic assays that employ hyperpolarized substrates at varying enzyme inhibitor concentrations. The physical labeling of nuclear spins by hyperpolarization thus provides the opportunity to devise fast novel in vitro experiments with low material requirement and without the need for synthetic modifications of target or ligands.

Lerche, Mathilde H.; Meier, Sebastian; Jensen, Pernille R.; Baumann, Herbert; Petersen, Bent O.; Karlsson, Magnus; Duus, Jens Ø.; Ardenkjær-Larsen, Jan H.

2010-03-01

273

77Se Enrichment of Proteins Expands the Biological NMR Toolbox  

PubMed Central

Sulfur, a key contributor to biological reactivity, is not amendable to investigations by biological NMR spectroscopy. To utilize selenium as a surrogate, we have developed a generally applicable 77Se isotopic enrichment method for heterologous proteins expressed in E. coli. We demonstrate 77Se NMR spectroscopy of multiple selenocysteine and selenomethionine residues in the sulfhydryl oxidase augmenter of liver regeneration (ALR). The resonances of the active site residues were assigned by comparing the NMR spectra of ALR bound to oxidized and reduced FAD. An additional resonance appears only in the presence of the reducing agent and disappears readily upon exposure to air and subsequent reoxidation of the flavin. Hence, 77Se NMR spectroscopy can be used to report the local electronic environment of reactive and structural sulfur sites, as well as changes taking place in those locations during catalysis.

Schaefer, Stephanie A.; Dong, Ming; Rubenstein, Renee P.; Wilkie, Wayne A.; Bahnson, Brian J.; Thorpe, Colin; Rozovsky, Sharon

2012-01-01

274

A Short Set of Carbon 13-NMR Correlation Tables.  

ERIC Educational Resources Information Center

Presents a short set of carbon-13 nuclear magnetic resonance (NMR) tables. These tables not only serve pedagogic purposes but also allow students to do calculations rapidly and with acceptable accuracy for a wide variety of compounds. (JN)

Brown, D. W.

1985-01-01

275

Use of NMR techniques for toxic organophosphorus compound profiling.  

PubMed

This review presents with selected examples the versatility of nuclear magnetic resonance (NMR) spectroscopy in the analysis of toxic organophosphorus (OP) compounds, i.e. OP pesticides and chemical warfare agents (CWAs). Several NMR applications of biological importance, like studies on inhibition mechanism, metabolism, and exposure determination, are presented. The review also concerns with the environmental analysis of OP compounds by NMR spectroscopy. Residue analysis of environment and food samples as well as characterization of degradation in environment is discussed. Some of the NMR studies that have been done to support the Chemical Weapons Convention, i.e. the development of suitable CWA detoxification means and the method development of verification analysis for CWAs and their degradation products, are outlined. PMID:19939751

Koskela, Harri

2010-05-15

276

Exp 13 C-NMR Tracer to Probe Coalification.  

National Technical Information Service (NTIS)

Solid-state NMR tracer experiments of synthetically prepared ( exp 13 C)lignins coalified under simulated geological conditions have illuminated a general chemical scheme for coalification. The labeling studies provide the first direct evidence for the co...

R. E. Botto R. Hayatsu R. G. Scott R. L. McBeth R. E. Winans

1985-01-01

277

Advances in NMR structures of integral membrane proteins.  

PubMed

Integral membrane proteins (IMPs) play a central role in cell communication with the environment. Their structures are essential for our understanding of the molecular mechanisms of signaling and for drug design, yet they remain badly underrepresented in the protein structure databank. Solution NMR is, aside from X-ray crystallography, the major tool in structural biology. Here we review recently reported solution NMR structures of polytopic IMPs and discuss the new approaches, which were developed in the course of these studies to overcome barriers in the field. Advances in cell-free protein expression, combinatorial isotope labeling, resonance assignment, and collection of structural data greatly accelerated IMP structure determination by solution NMR. In addition, novel membrane-mimicking media made possible determination of solution NMR structures of IMPs in a native-like lipid environment. PMID:23721747

Maslennikov, Innokentiy; Choe, Senyon

2013-08-01

278

Error analysis for NMR polymer microstructure measurement without calibration standards.  

PubMed

We report an error analysis method for primary analytical methods in the absence of calibration standards. Quantitative (13)C NMR analysis of ethylene/1-octene (E/O) copolymers is given as an example. Because the method is based on a self-calibration scheme established by counting, it is a measure of accuracy rather than precision. We demonstrate it is self-consistent and neither underestimate nor excessively overestimate the experimental errors. We also show the method identified previously unknown systematic biases in a NMR instrument. The method can eliminate unnecessary data averaging to save valuable NMR resources. The accuracy estimate proposed is not unique to (13)C NMR spectroscopy of E/O but should be applicable to all other measurement systems where the accuracy of a subset of the measured responses can be established. PMID:19764702

Qiu, XiaoHua; Zhou, Zhe; Gobbi, Gian; Redwine, Oscar D

2009-10-15

279

Solid-state NMR as an analytical tool: quantitative aspects.  

PubMed

Analytical methods based on solid-state NMR are becoming increasingly popular. However, these flourishing activities bring up the issue of how accurately NMR can assess an analyte proportion in a solid sample. The use of a chemical intensity reference for this purpose is a natural but often unsuitable choice, due to sample stability or preciousness. We propose here a protocol to perform quantitative measurements in solid-state NMR, by calibration of the circuit response through a low-power pulse injected during the acquisition (the so-called ERETIC method). Although this method has been in use for some time in liquid-phase and in vivo NMR, we point out here some peculiarities and useful applications typical of solids. Namely, the temperature dependence of the signal intensity imposes care in the application to MAS experiments. PMID:16229992

Ziarelli, Fabio; Caldarelli, Stefano

2006-02-01

280

1H NMR visibility of mammalian glycogen in solution.  

PubMed

High-resolution 1H NMR spectra of rabbit liver glycogen in 2H2O were obtained at 500 MHz, and several resonances were assigned by comparison with the chemical shifts of alpha-linked diglucose molecules. The NMR relaxation times T1 and T2 of glycogen in 2H2O were determined to be 1.1 and 0.029 s, respectively. The measured natural linewidth of the carbon-1 proton (12 +/- 2 Hz) is in excellent agreement with that calculated from T2. The visibility measurements made by digesting glycogen and comparing glucose and glycogen signal intensities demonstrate that in spite of the very high molecular weight, all of the proton nuclei in glycogen contribute to the NMR spectrum. The result is not unexpected, since 100% NMR visibility was previously observed from the carbon nuclei of glycogen, due to the rapid intramolecular motions. PMID:2308928

Zang, L H; Rothman, D L; Shulman, R G

1990-03-01

281

Using metamaterial yokes in NMR measurements  

NASA Astrophysics Data System (ADS)

Swiss rolls are one instance of metamaterials, and can be described as an effective medium with a complex, anisotropic magnetic permeability. It has been shown that bundles of Swiss rolls can guide the magnetic flux in magnetic resonance measurements and increase the coupling between the nuclear spins and the receiver coil. Here, we investigate, with a numerical model, whether Swiss rolls can boost the detected signal in a NMR experiment, where the rolls could provide a low-reluctance return path for the magnetic flux when shaped in a yoke encircling the sample. The system consisting of the nuclear spin, the rolls and the receiver coil is analyzed with the method of finite differences in time domain (FDTD). The results show that small gains in the received signal are possible, but only if the losses (resistive and dielectric) in the rolls are reduced by over one order of magnitude from their present value in state-of-the-art materials. This situation arises because of the energy dissipation in the rolls and the mode splitting caused by the coupling between the rolls and the resonant coil.

Allard, Mathieu; Henkelman, R. Mark

2006-10-01

282

Broadband Multiple-Quantum NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

A simple broadband radiofrequency pulse sequence for the excitation of multiple-quantum coherences in the presence of fast magic-angle spinning is introduced. This sequence involves back-to-back (BABA) 90° radiofrequency pulse cycles timed to span two rotor periods. It proved to be robust and insensitive to off-resonance effects, to isotropic chemical shifts, and to chemical-shift anisotropies. This is demonstrated on crystalline phosphates, composed of Q(1), Q(2), and Q(3)groups, which are characterized by a large chemical-shift anisotropy spanning more than 200 ppm. With these experiments, 31P high-resolution double-quantum NMR spectroscopy is introduced as a tool for the direct investigation of dipolar connectivities between like or different Q( n) units in phosphates. 31P dipolar connectivities in two samples, Mg 2P 2O 7and MgP 4O 11were established. Therefore, double-quantum spectroscopy of this kind has potential for the investigation of disordered solids, for instance, phosphorus glasses.

Feike, M.; Demco, D. E.; Graf, R.; Gottwald, J.; Hafner, S.; Spiess, H. W.

283

Dilute Bicellar Solutions for Structural NMR Work  

NASA Astrophysics Data System (ADS)

Deuterium NMR spectroscopy has been employed to characterize the concentration dependence of orientational order in DMPC/DHPC bicellar solutions with molar ratios q= [DMPC]/[DHPC] = 3.3, 2.7, and 2.3. The stability of a discotic nematic phase can, in general, be predicted from a simple Onsager picture involving the size and concentration of the mesogenic unit, but for the bicellar solutions this model is not adequate. Specifically, macroscopic alignment is observed at total lipid concentrations well below that, 1-10% (w/w) predicted by Onsager's model. Thus the discotic nematic phase is stable to ?3-5% (w/w) for q= 3.3-2.3, and the bicellar order is highest just before phase separation occurs at the minimum total phospholipid concentration. This implies the presence of a DHPC bic? DHPC solequilibrium in establishing bicellar size, thereby extending the range of concentrations for which alignment occurs. Bicellar morphology has been verified for a wide range of concentrations, temperatures, and q-values, but as viscosity measurements demonstrate, major morphological changes take place as the temperature is reduced below 30°C.

Struppe, Jochem; Vold, Regitze R.

1998-12-01

284

NMR velocity imaging of single liquid drops  

NASA Astrophysics Data System (ADS)

Liquid-liquid extraction processes are often found in industrial applications when a bulk phase needs to be purified from dissolved components. The extraction strategy consists of dissolving the impurities into a second, carrier phase, with optimal performance being guaranteed by maximizing both contact interface area and mass transfer rate, in the shape of a swarm of dispersed droplets. Their buoyancy-driven flow within the continuous medium induces internal fluid motion driven by momentum transfer at the drop surface. This convective transport enhances mass transfer and the efficiency of an extraction column. However, understanding mass transfer depends on a proper description of the flow field inside and outside the drops. For that purpose, a cell was built that enables the levitation of a single drop within a counterstream of water. NMR velocity imaging was then applied to drops of different fluids to monitor the internal dynamics as a function of drop size, age, and interface tension. Vortex-type patterns in at least part of the drop were observed where their size and velocity magnitude depended on the system impurity concentration.

Amar, A.; Stapf, S.; Bluemich, B.

2007-03-01

285

Para-hydrogen perspectives in hyperpolarized NMR.  

PubMed

The first instance of para-hydrogen induced polarization (PHIP) in an NMR experiment was serendipitously observed in the 1980s while investigating a hydrogenation reaction (Seldler et al., 1983; Bowers and Weitekamp, 1986, 1987; Eisenschmid et al., 1987) [1-4]. Remarkably a theoretical investigation of the applicability of para-hydrogen as a hyperpolarization agent was being performed in the 1980's thereby quickly providing a theoretical basis for the PHIP-effect (Bowers and Weitekamp, 1986) [2]. The discovery of signal amplification by a non-hydrogenating interaction with para-hydrogen has recently extended the interest to exploit the PHIP effect, as it enables investigation of compounds without structural alteration while retaining the advantages of spectroscopy with hyperpolarized compounds [5]. In this article we will place more emphasis of the future applications of the method while only briefly discussing the efforts that have been made in the understanding of the phenomenon and the development of the method so far. PMID:23932399

Glöggler, Stefan; Colell, Johannes; Appelt, Stephan

2013-10-01

286

Graphite lamellar compounds 13C NMR studies  

NASA Astrophysics Data System (ADS)

13C NMR (natural abundance, room temperature) in a range of graphite lamellar compounds with donors or acceptors is interpreted in terms of charge transfer. The observed shifts and structure are related to anisotropic chemical shifts, or to Knight shifts, or a combination of both effects. Donors shifts - towards high field - agree with an important indirect Knight shift superimposed to a chemical shift. Using Fermi level density of states N( EF) deduced from Mizutani and co-workers measurements, large charge transfer are deduced: 0.3< f<1. Acceptors compounds show narrow lines with a 150 ppm axial anisotropy, the H0 ? ( a, b) component being undisplaced as compared to the graphite one: f appears small or negligible. Donors results are consistent with the occurring of a narrow energy band just above the graphite Fermi level resulting in high N( EF). In acceptors, they seem to be characteristic of 2-D compounds without covalent bonding, the main effect of acceptor molecules being to separate the graphitic planes.

Conard, J.; Estrade, H.; Lauginie, P.; Fuzellier, H.; Furdin, G.; Vasse, R.

1980-01-01

287

Lithium NMR in Lithium-Carbon Solid State Compounds  

Microsoft Academic Search

\\u000a Historically, 7Li NMR started in 1946 with Li+ aqueous solutions whereas Li-alkyl where first studied in the early sixties. In spite of the importance of lithiated organic\\u000a compounds in organic synthesis and its high sensitivity, 7Li has not contributed so much to the development of NMR, like 1H, 13C, 17O and 15N because its predicted chemical shift range (5ppm) is

J. Conard; P. Lauginie

288

High resolution phosphorus NMR spectroscopy of transfer ribonucleic acids  

Microsoft Academic Search

The temperature dependence of the 31P NMR spectra of yeast phenylalanine tRNA, E. coli tyrosine, glutamate (2), and formylmethione tRNA, and bovine liver aspartate (2b) tRNA is presented. The major difference between the 31P NMR spectra of the different acceptor tRNAs is in the main cluster region between -0.5 and -1.3 ppm. This confirms earlier assignment of the main cluster

D. G. Gorenstein; E. M. Goldfield

1982-01-01

289

Fluid-Rock Characterization and Interactions in NMR Well Logging  

SciTech Connect

The objective of this project was to characterize the fluid properties and fluid-rock interactions which are needed for formation evaluation by NMR well logging. NMR well logging is finding wide use in formation evaluation. The formation parameters commonly estimated were porosity, permeability, and capillary bound water. Special cases include estimation of oil viscosity, residual oil saturation, location of oil/water contact, and interpretation on whether the hydrocarbon is oil or gas.

Hirasaki, George J.; Mohanty, Kishore K.

2003-02-10

290

NMR quantitation of natural products at the nanomole scale.  

PubMed

We describe a simple and accurate method for quantitation by solvent 13C-satellites (QSCS) of very small amounts of natural products using microprobe NMR spectroscopy. The method takes advantage of integration of 13C satellite peaks of deuterated solvents, in particular CDCl3, that have favorable intensities for measurements of samples in NMR microcoils and microprobe tubes in the 1-200 nanomole range. PMID:19399996

Dalisay, Doralyn S; Molinski, Tadeusz F

2009-04-01

291

NMR Quantitation of Natural Products at the Nanomole-Scale  

PubMed Central

We describe a simple and accurate method for quantitation by solvent 13C-satellites (QSCS), of very small amounts of natural products using microprobe NMR spectroscopy. The method takes advantage of integration of 13C satellite peaks of deuterated solvents, in particular CDCl3, that have favorable intensities for measurements of samples in NMR microcoils and microprobe tubes in the 1–200 nanomole range.

Dalisay, Doralyn S.; Molinski, Tadeusz F.

2009-01-01

292

Liquid domains in vesicles investigated by NMR and fluorescence microscopy.  

PubMed

We use (2)H-NMR, (1)H-MAS NMR, and fluorescence microscopy to detect immiscibility in three particular phospholipid ratios mixed with 30% cholesterol: 2:1 DOPC/DPPC, 1:1 DOPC/DPPC, and 1:2 DOPC/DPPC. Large-scale (>160 nm) phase separation into liquid-ordered (L(o)) and liquid-crystalline (L(alpha)) phases is observed by both NMR and fluorescence microscopy. By fitting superimposed (2)H-NMR spectra, we quantitatively determine that the L(o) phase is strongly enriched in DPPC and moderately enriched in cholesterol. Tie-lines estimated at different temperatures and membrane compositions are based on both (2)H-NMR observations and a previously published ternary phase diagram. (2)H- and (1)H-MAS NMR techniques probe significantly smaller length scales than microscopy experiments (submicron versus micron-scalp), and complex behavior is observed near the miscibility transition. Fluorescence microscopy of giant unilamellar vesicles shows micrometer-scale domains below the miscibility transition. In contrast, NMR of multilamellar vesicles gives evidence for smaller ( approximately 80 nm) domains just below the miscibility transition, whereas large-scale demixing occurs at a lower temperature, T(low). A transition at T(low) is also evident in fluorescence microscopy measurements of the surface area fraction of ordered phase in giant unilamellar vesicles. Our results reemphasize the complex phase behavior of cholesterol-containing membranes and provide a framework for interpreting (2)H-NMR experiments in similar membranes. PMID:15111407

Veatch, S L; Polozov, I V; Gawrisch, K; Keller, S L

2004-05-01

293

NMR study of tunneling states in solid CD4  

Microsoft Academic Search

We report an NMR study of solid CD4 in the temperature range 35-455 mK. At the lower temperatures, the area of the NMR absorption line shows a significant increase over that expected from the Curie law alone. We interpret this as evidence for spin-species conversion, associated with the thermal relaxation of the occupation of an array of tunneling levels. The

Saps Buchman; W. T. Vetterling; Donald Candela; R. V. Pound

1982-01-01

294

Structure-based protein NMR assignments using native structural ensembles  

Microsoft Academic Search

An important step in NMR protein structure determination is the assignment of resonances and NOEs to corresponding nuclei.\\u000a Structure-based assignment (SBA) uses a model structure (“template”) for the target protein to expedite this process. Nuclear\\u000a vector replacement (NVR) is an SBA framework that combines multiple sources of NMR data (chemical shifts, RDCs, sparse NOEs,\\u000a amide exchange rates, TOCSY) and has

Mehmet Serkan Apayd?n; Vincent Conitzer; Bruce Randall Donald

2008-01-01

295

Deuterium incorporation in biomass cell wall components by NMR analysis.  

PubMed

A commercially available deuterated kale sample was analyzed for deuterium incorporation by ionic liquid solution (2)H and (1)H nuclear magnetic resonance (NMR). This protocol was found to effectively measure the percent deuterium incorporation at 33%, comparable to the 31% value determined by combustion. The solution NMR technique also suggested by a qualitative analysis that deuterium is preferentially incorporated into the carbohydrate components of the kale sample. PMID:22223179

Foston, Marcus B; McGaughey, Joseph; O'Neill, Hugh; Evans, Barbara R; Ragauskas, Arthur

2012-03-01

296

Development and application of proton NMR methodology to lipoprotein analysis  

NASA Astrophysics Data System (ADS)

The present thesis describes the development of 1H NMR spectroscopy and its applications to lipoprotein analysis in vitro, utilizing biochemical prior knowledge and advanced lineshape fitting analysis in the frequency domain. A method for absolute quantification of lipoprotein lipids and proteins directly from the terminal methyl-CH3 resonance region of 1H NMR spectra of human blood plasma is described. Then the use of NMR methodology in time course studies of the oxidation process of LDL particles is presented. The function of the cholesteryl ester transfer protein (CETP) in lipoprotein mixtures was also assessed by 1H NMR, which allows for dynamic follow-up of the lipid transfer reactions between VLDL, LDL, and HDL particles. The results corroborated the suggestion that neutral lipid mass transfer among lipoproteins is not an equimolar heteroexchange. A novel method for studying lipoprotein particle fusion is also demonstrated. It is shown that the progression of proteolytically (?- chymotrypsin) induced fusion of LDL particles can be followed by 1H NMR spectroscopy and, moreover, that fusion can be distinguished from aggregation. In addition, NMR methodology was used to study the changes in HDL3 particles induced by phospholipid transfer protein (PLTP) in HDL3 + PLTP mixtures. The 1H NMR study revealed a gradual production of enlarged HDL particles, which demonstrated that PLTP-mediated remodeling of HDL involves fusion of the HDL particles. These applications demonstrated that the 1H NMR approach offers several advantages both in quantification and in time course studies of lipoprotein-lipoprotein interactions and of enzyme/lipid transfer protein function.

Korhonen, Ari Juhani

1998-11-01

297

Localized in vivo13C NMR spectroscopy of the brain  

PubMed Central

Localized 13C NMR spectroscopy provides a new investigative tool for studying cerebral metabolism. The application of 13C NMR spectroscopy to living intact humans and animals presents the investigator with a number of unique challenges. This review provides in the first part a tutorial insight into the ingredients required for achieving a successful implementation of localized 13C NMR spectroscopy. The difficulties in establishing 13C NMR are the need for decoupling of the one-bond 13C–1H heteronuclear J coupling, the large chemical shift range, the low sensitivity and the need for localization of the signals. The methodological consequences of these technical problems are discussed, particularly with respect to (a) RF front-end considerations, (b) localization methods, (c) the low sensitivity, and (d) quantification methods. Lastly, some achievements of in vivo localized 13C NMR spectroscopy of the brain are reviewed, such as: (a) the measurement of brain glutamine synthesis and the feasibility of quantifying glutamatergic action in the brain; (b) the demonstration of significant anaplerotic fluxes in the brain; (c) the demonstration of a highly regulated malate-aspartate shuttle in brain energy metabolism and isotope flux; (d) quantification of neuronal and glial energy metabolism; and (e) brain glycogen metabolism in hypoglycemia in rats and humans. We conclude that the unique and novel insights provided by 13C NMR spectroscopy have opened many new research areas that are likely to improve the understanding of brain carbohydrate metabolism in health and disease.

Gruetter, Rolf; Adriany, Gregor; Choi, In-Young; Henry, Pierre-Gilles; Lei, Hongxia; Oz, Gulin

2006-01-01

298

NMR analysis on microfluidic devices by remote detection  

SciTech Connect

We present a novel approach to perform high-sensitivity NMR imaging and spectroscopic analysis on microfluidic devices. The application of NMR, the most information rich spectroscopic technique, to microfluidic devices remains a challenge because the inherently low sensitivity of NMR is aggravated by small fluid volumes leading to low NMR signal, and geometric constraints resulting in poor efficiency for inductive detection. We address the latter by physically separating signal detection from encoding of information with remote detection. Thereby, we use a commercial imaging probe with sufficiently large diameter to encompass the entire device, enabling encoding of NMR information at any location on the chip. Because large-diameter coils are too insensitive for detection, we store the encoded information as longitudinal magnetization and flow it into the outlet capillary. There, we detect the signal with optimal sensitivity using a solenoidal microcoil, and reconstruct the information encoded in the fluid. We present a generally applicable design for a detection-only microcoil probe that can be inserted into the bore of a commercial imaging probe. Using hyperpolarized 129Xe gas, we show that this probe enables sensitive reconstruction of NMR spectroscopic information encoded by the large imaging probe while keeping the flexibility of a large coil.

McDonnell, Erin E.; Han, SongI; Hilty, Christian; Pierce,Kimberly; Pines, Alexander

2005-08-15

299

Design and applications of an in situ electrochemical NMR cell.  

PubMed

A device using a three-electrode electrochemical cell (referred to as an ECNMR cell) was successfully constructed that could be used in a standard 5mm NMR probe to acquire high-resolution NMR spectra while the working electrode was held at a constant electrical potential. The working electrode was a 20 nm thick gold film thermally coated on the outside of an inner 3mm glass tube. An underlayer consisting of (3-mercaptopropyl)trimethoxy-silane was coated on the glass surface in order to improve its adhesion to gold. Tests showed prolonged life of the gold film. Details of the design and construction of the ECNMR cell are described. The ECNMR cell could be routinely used in a multi-user service high-resolution NMR instrument under oxygen-free conditions in both aqueous and non-aqueous solvents. Different approaches were applied to suppress the noise transmitted between the potentiostat and the NMR spectrometer. These approaches were shown to be effective in reducing background noise in the NMR spectra. The electrochemical and NMR performance of the ECNMR cell is presented. The reduction of 1,4-benzoquinone in both aqueous and non-aqueous solvents was used for testing. The evolution of the in situ ECNMR spectra with time demonstrated that use of the ECNMR cell was feasible. Studies of caffeic acid and 9-chloroanthracene using this ECNMR cell were undertaken to explore its applications, such as monitoring reactions and studying their reaction mechanisms. PMID:21067948

Zhang, Xiaocan; Zwanziger, Josef W

2011-01-01

300

Design and applications of an in situ electrochemical NMR cell  

NASA Astrophysics Data System (ADS)

A device using a three-electrode electrochemical cell (referred to as an ECNMR cell) was successfully constructed that could be used in a standard 5 mm NMR probe to acquire high-resolution NMR spectra while the working electrode was held at a constant electrical potential. The working electrode was a 20 nm thick gold film thermally coated on the outside of an inner 3 mm glass tube. An underlayer consisting of (3-mercaptopropyl)trimethoxy-silane was coated on the glass surface in order to improve its adhesion to gold. Tests showed prolonged life of the gold film. Details of the design and construction of the ECNMR cell are described. The ECNMR cell could be routinely used in a multi-user service high-resolution NMR instrument under oxygen-free conditions in both aqueous and non-aqueous solvents. Different approaches were applied to suppress the noise transmitted between the potentiostat and the NMR spectrometer. These approaches were shown to be effective in reducing background noise in the NMR spectra. The electrochemical and NMR performance of the ECNMR cell is presented. The reduction of 1,4-benzoquinone in both aqueous and non-aqueous solvents was used for testing. The evolution of the in situ ECNMR spectra with time demonstrated that use of the ECNMR cell was feasible. Studies of caffeic acid and 9-chloroanthracene using this ECNMR cell were undertaken to explore its applications, such as monitoring reactions and studying their reaction mechanisms.

Zhang, Xiaocan; Zwanziger, Josef W.

2011-01-01

301

NMR methods for studying the structure and dynamics of RNA.  

PubMed

Proper functioning of RNAs requires the formation of complex three-dimensional structures combined with the ability to rapidly interconvert between multiple functional states. This review covers recent advances in isotope-labeling strategies and NMR experimental approaches that have promise for facilitating solution structure determinations and dynamics studies of biologically active RNAs. Improved methods for the production of isotopically labeled RNAs combined with new multidimensional heteronuclear NMR experiments make it possible to dramatically reduce spectral crowding and simplify resonance assignments for RNAs. Several novel applications of experiments that directly detect hydrogen-bonding interactions are discussed. These studies demonstrate how NMR spectroscopy can be used to distinguish between possible secondary structures and identify mechanisms of ligand binding in RNAs. A variety of recently developed methods for measuring base and sugar residual dipolar couplings are described. NMR residual dipolar coupling techniques provide valuable data for determining the long-range structure and orientation of helical regions in RNAs. A number of studies are also presented where residual dipolar coupling constraints are used to determine the global structure and dynamics of RNAs. NMR relaxation data can be used to probe the dynamics of macromolecules in solution. The power dependence of transverse rotating-frame relaxation rates was used here to study dynamics in the minimal hammerhead ribozyme. Improved methods for isotopically labeling RNAs combined with new types of structural data obtained from a growing repertoire of NMR experiments are facilitating structural and dynamic studies of larger RNAs. PMID:16138301

Latham, Michael P; Brown, Darin J; McCallum, Scott A; Pardi, Arthur

2005-09-01

302

LEGO-NMR spectroscopy: a method to visualize individual subunits in large heteromeric complexes.  

PubMed

Seeing the big picture: Asymmetric macromolecular complexes that are NMR active in only a subset of their subunits can be prepared, thus decreasing NMR spectral complexity. For the hetero heptameric LSm1-7 and LSm2-8 rings NMR spectra of the individual subunits of the complete complex are obtained, showing a conserved RNA binding site. This LEGO-NMR technique makes large asymmetric complexes accessible to detailed NMR spectroscopic studies. PMID:23946163

Mund, Markus; Overbeck, Jan H; Ullmann, Janina; Sprangers, Remco

2013-10-18

303

Advanced NMR characterization of zeolite catalysts. Third quarterly report, 1 March 1984-31 May 1984  

SciTech Connect

The program discussed in this report is a study of the application of improved high resolution solid state nuclear magnetic resonance (NMR) techniques to the characterization of zeolite catalysts. During the first phase of this program very pure, and in some cases isotopically enriched faujasites will be prepared and studied by magic angle sample spinning NMR (MASS NMR) and variable angle sample spinning NMR (VASS NMR) on 500 and 360 MHz (Proton frequency) NMR spectrometers. The NMR techniques that will be emphasized are the measurement and analysis of the /sup 17/O NMR properties, /sup 27/Al NMR intensity quantitation, and /sup 27/Al and /sup 29/Si NMR relaxation rates. During the second phase of this program these NMR techniques will be used to study the effects of impurity concentration, dealumination treatments and cation exchange on the NMR properties of faujasites. The initial emphasis of this program during Phase I is on the preparation and measurement of the NMR properties of /sup 17/O enriched Na-Y faujasites. The effort in each phase is broken into four tasks: (1) zeolite preparation, (2) standard zeolite characterization, (3) measurement of zeolite NMR properties, and (4) analysis of NMR data. The main efforts during the third three month period of the program have been the characterization of the /sup 17/O enriched zeolites, particularly X and Y zeolites, and the preparation of additional /sup 17/O enriched zeolites. MASS NMR and VASS NMR as well as static NMR measurements have been made on these materials for /sup 17/O NMR frequencies from 20.4 to 67.8 MHz. Computer simulations of the experimental NMR lineshapes are in progress. Results to date indicate that the observed spectra arise from two different types of oxygen sites, possibly O in Al-O-Si links and chemically bound OH groups. 2 references, 1 figure, 1 table.

Welsh, L.B.

1984-06-01

304

The use of non-uniform deuterium labelling ['NMR-window'] to study the NMR structure of a 21mer RNA hairpin.  

PubMed Central

The first synthesis of a non-uniformly deuterium labelled 21mer RNA is reported using our 'NMR-window' concept, showing its unique application in the unambiguous NMR assignment of the non-exchangeable aromatic and sugar protons.

Foldesi, A; Yamakage, S I; Nilsson, F P; Maltseva, T V; Chattopadhyaya, J

1996-01-01

305

Operation of a 500 MHz high temperature superconducting NMR: towards an NMR spectrometer operating beyond 1 GHz.  

PubMed

We have begun a project to develop an NMR spectrometer that operates at frequencies beyond 1 GHz (magnetic field strength in excess of 23.5 T) using a high temperature superconductor (HTS) innermost coil. As the first step, we developed a 500 MHz NMR with a Bi-2223 HTS innermost coil, which was operated in external current mode. The temporal magnetic field change of the NMR magnet after the coil charge was dominated by (i) the field fluctuation due to a DC power supply and (ii) relaxation in the screening current in the HTS tape conductor; effect (i) was stabilized by the 2H field-frequency lock system, while effect (ii) decreased with time due to relaxation of the screening current induced in the HTS coil and reached 10(-8)(0.01 ppm)/h on the 20th day after the coil charge, which was as small as the persistent current mode of the NMR magnet. The 1D (1)H NMR spectra obtained by the 500 MHz LTS/HTS magnet were nearly equivalent to those obtained by the LTS NMR magnet. The 2D-NOESY, 3D-HNCO and 3D-HNCACB spectra were achieved for ubiquitin by the 500 MHz LTS/HTS magnet; their quality was closely equivalent to that achieved by a conventional LTS NMR. Based on the results of numerical simulation, the effects of screening current-induced magnetic field changes are predicted to be harmless for the 1.03 GHz NMR magnet system. PMID:20149698

Yanagisawa, Y; Nakagome, H; Tennmei, K; Hamada, M; Yoshikawa, M; Otsuka, A; Hosono, M; Kiyoshi, T; Takahashi, M; Yamazaki, T; Maeda, H

2010-04-01

306

NMR Study of Strontium Binding by a Micaceous Mineral  

SciTech Connect

The nature of strontium binding by soil minerals directly affects the transport and sequestration/remediation of radioactive strontium species released from leaking high-level nuclear waste storage tanks. However, the molecular-level structure of strontium binding sites has seldom been explored in phyllosilicate minerals by direct spectroscopic means and is not well-understood. In this work, we use solid-state NMR to analyze strontium directly and indirectly in a fully strontium-exchanged synthetic mica of nominal composition Na4Mg6Al4Si4O20F4. Thermogravimetric analysis, X-ray diffraction analysis, and NMR evidence supports that heat treatment at 500 °C for 4 h fully dehydrates the mica, creating a hydrogen-free interlayer. Analysis of the strontium NMR spectrum of the heat-treated mica shows a single strontium environment with a quadrupolar coupling constant of 9.02 MHz and a quadrupolar asymmetry parameter of 1.0. These quadrupolar parameters are consistent with a highly distorted and asymmetric coordination environment that would be produced by strontium cations without water in the coordination sphere bound deep within the ditrigonal holes. Evidence for at least one additional strontium environment, where proton-strontium couplings may occur, was found via a 1H-87Sr transfer of populations by double resonance NMR experiment. We conclude that the strontium cations in the proton-free interlayer are observable by 87Sr NMR and bound through electrostatic interactions as nine coordinate inner-sphere complexes sitting in the ditrigonal holes. Partially hydrated strontium cations invisible to direct 87Sr NMR are also present and located on the external mica surfaces, which are known to hydrate upon exposure to atmospheric moisture. These results demonstrate that modern pulsed NMR techniques and high fields can be used effectively to provide structural details of strontium binding by phyllosilicate minerals.

Bowers, Geoffrey M.; Ravella, Ramesh; Komarneni, S.; Mueller, Karl T.

2006-04-13

307

Observations of aerobic, growing Escherichia coli metabolism using an on-line nuclear magnetic resonance spectroscopy system  

Microsoft Academic Search

An experimental system has been constructed which enables on-line measurements of phosphorus-31 ([sup 31]P) nuclear magnetic resonance (NMR) spectra for growing bacterial suspensions under anaerobic or aerobic conditions. A sample stream from a laboratory bioreactor is circulated to the NMR sample chamber in a gas exchange system which permits maintenance of aerobic conditions for high-cell-density cultures. [sup 31]P NMR spectra

Ruizhen Chen; James E. Bailey

1993-01-01

308

MQ NMR dynamics in dipolar ordered state at negative temperature.  

PubMed

We investigate theoretically the Multiple Quantum (MQ) NMR dynamics at negative absolute temperatures in systems of nuclear spins 1/2 coupled by the dipole-dipole interactions and with the initial conditions determined by the dipolar ordered state. Two different methods of MQ NMR are used. One of them is based on the measurement of the dipolar energy. The other method uses an additional resonance (?/4)y-pulse after the preparation period of the standard MQ NMR experiment. It is shown that at negative temperatures many-spin clusters and spin correlations are created faster, and the intensities of MQ coherences are higher than in the usual MQ NMR experiments. So, the eighth-order MQ coherence in 10-spin system of the cyclopentane molecule appears to be 1.5 times faster and its intensity is four orders higher than at positive temperatures. The proposed MQ NMR methods at negative absolute temperatures can be used for the investigation of many-spin dynamics of nuclear spins in solids. PMID:24992818

Furman, G B; Goren, S D; Meerovich, V M; Sokolovsky, V L

2014-01-01

309

Applications of toroids in high-pressure NMR spectroscopy  

SciTech Connect

Toroid detectors have distinct NMR sensitivity and imaging advantages. The magnetic field lines are nearly completely contained within the active volume element of a toroid. This results in high NMR signal sensitivity. In addition, the toroid detector may be placed next to the metallic walls of a containment vessel with minimal signal loss due to magnetic coupling with the metal container. Thus, the toroid detector is ideal for static high pressure or continuous flow monitoring systems. Toroid NMR detectors have been used to follow the hydroformylation of olefins in supercritical fluids under industrial process conditions. Supercritical fluids are potentially ideal media for conducting catalytic reactions that involve gaseous reactants, including H{sub 2}, CO, and CO{sub 2}. The presence of a single homogeneous reaction phase eliminates the gas-liquid mixing problem of alternative two-phase systems, which can limit process rates and adversely affect hydroformylation product selectivities. A second advantage of toroid NMR detectors is that they exhibit a well-defined gradient in the rf field. This magnetic field gradient can be used for NMR imaging applications. Distance resolutions of 20 {mu} have been obtained.

Klingler, R.J.; Rathke, J.W.; Woelk, K. [and others

1995-12-01

310

GFT projection NMR spectroscopy for proteins in the solid state  

PubMed Central

Recording of four-dimensional (4D) spectra for proteins in the solid state has opened new avenues to obtain virtually complete resonance assignments and three-dimensional (3D) structures of proteins. As in solution state NMR, the sampling of three indirect dimensions leads per se to long minimal measurement time. Furthermore, artifact suppression in solid state NMR relies primarily on radio-frequency pulse phase cycling. For an n-step phase cycle, the minimal measurement times of both 3D and 4D spectra are increased n times. To tackle the associated ‘sampling problem’ and to avoid sampling limited data acquisition, solid state G-Matrix Fourier Transform (SS GFT) projection NMR is introduced to rapidly acquire 3D and 4D spectral information. Specifically, (4,3)D (HA)CANCOCX and (3,2)D (HACA)NCOCX were implemented and recorded for the 6 kDa protein GB1 within about 10% of the time required for acquiring the conventional congeners with the same maximal evolution times and spectral widths in the indirect dimensions. Spectral analysis was complemented by comparative analysis of expected spectral congestion in conventional and GFT NMR experiments, demonstrating that high spectral resolution of the GFT NMR experiments enables one to efficiently obtain nearly complete resonance assignments even for large proteins.

Franks, W. Trent; Atreya, Hanudatta S.; Szyperski, Thomas

2011-01-01

311

Effective rotational correlation times of proteins from NMR relaxation interference  

NASA Astrophysics Data System (ADS)

Knowledge of the effective rotational correlation times, ?c, for the modulation of anisotropic spin-spin interactions in macromolecules subject to Brownian motion in solution is of key interest for the practice of NMR spectroscopy in structural biology. The value of ?c enables an estimate of the NMR spin relaxation rates, and indicates possible aggregation of the macromolecular species. This paper reports a novel NMR pulse scheme, [ 15N, 1H]-TRACT, which is based on transverse relaxation-optimized spectroscopy and permits to determine ?c for 15N- 1H bonds without interference from dipole-dipole coupling of the amide proton with remote protons. [ 15N, 1H]-TRACT is highly efficient since only a series of one-dimensional NMR spectra need to be recorded. Its use is suggested for a quick estimate of the rotational correlation time, to monitor sample quality and to determine optimal parameters for complex multidimensional NMR experiments. Practical applications are illustrated with the 110 kDa 7,8-dihydroneopterin aldolase from Staphylococcus aureus, the uniformly 15N-labeled Escherichia coli outer membrane protein X (OmpX) in 60 kDa mixed OmpX/DHPC micelles with approximately 90 molecules of unlabeled 1,2-dihexanoyl- sn-glycero-3-phosphocholine (DHPC), and the 16 kDa pheromone-binding protein from Bombyx mori, which cover a wide range of correlation times.

Lee, Donghan; Hilty, Christian; Wider, Gerhard; Wüthrich, Kurt

2006-01-01

312

Low Cost CE-NMR with Microcoils for Chemical Detection  

SciTech Connect

Understanding speciation in solids and solutions is important for environmental and toxicological purposes. Capillary electrophoresis (CE) is a simple rapid separation technique that can be used to identify species in solution. CE is particularly is well suited for rapid separations of metal containing samples. Direct on-capillary measurement of metal compound speciation can be obtained with nuclear magnetic resonance (NMR). The development of a low-cost microcoil CE-NMR system for in situ characterization of samples of interest is discussed. High precision laser lithography is used to produce copper sputtered microcoils that have comparable resistivity and quality factors to that of hand wound microcoils. A portable NMR system coupled with a CE system has the potential to identify chemical species in aqueous solutions. In addition, transient isotachophoresis can separate and pre-concentrate samples of interest to obtain separate chemical peaks for speciation by online NMR analysis. We are developing separation assays to determine the speciation of chemical complexes in solutions with minimal perturbation to the original sample equilibrium. On-line NMR measurements will be made downstream of the UV detector.

Adams, K; Klunder, G; Demas, V; Malba, V; Bernhardt, A; Evan, L; Harvey, C; Maxwell, R; Herberg, J L

2009-01-08

313

Low Cost CE-NMR with Microcoils for Chemical Detection  

SciTech Connect

Understanding speciation in solids and solutions is important for environmental and toxicological purposes. Capillary electrophoresis (CE) is a simple rapid separation technique that can be used to identify species in solution. CE is particularly is well suited for rapid separations of metal containing samples. Direct on-capillary measurement of metal compound speciation can be obtained with nuclear magnetic resonance (NMR). The development of a low-cost microcoil CE-NMR system for in situ characterization of samples of interest is discussed. High precision laser lithography is used to produce copper sputtered microcoils that have comparable resistivity and quality factors to that of hand wound microcoils. A portable NMR system coupled with a CE system has the potential to identify chemical species in aqueous solutions. In addition, transient isotachophoresis can separate and pre-concentrate samples of interest to obtain separate chemical peaks for speciation by online NMR analysis. We are developing separation assays to determine the speciation of chemical complexes in solutions with minimal perturbation to the original sample equilibrium. On-line NMR measurements will be made downstream of the UV detector.

Adams, K L; Klunder, G; Demas, V; Malba, V; Bernhardt, A; Evan, L; Harvey, C; Maxwell, R; Herberg, J

2008-07-25

314

Evaluation of abdominal aortic aneurysms with NMR imaging  

SciTech Connect

Seven patients (5 male and 2 female, age range from 50 to 88) with angiographic proven abdominal aortic aneurysms were evaluated with NMR imaging (1.5 K gauss system) of the abdomen. Images were obtained in transverse, coronal and saggital planes with three radiofrequency pulse sequences (saturation recovery (SR), inversion recovery (IR), and spin echo (SE)). All of the aneurysms were identified as to site and relative size with NMR images. The lumen in which there was flowing blood was always dark (low intensity), whereas the aneurysmal area which contained presumed clot was brighter (high intensity) on SR images. Although the size, location and relationship to other blood vessels was best demonstrated on aortography, NMR images provided similar information in all cases. NMR images correctly demonstrated thrombus in six cases. The authors conclude that NMR imaging provides a clear delineation of the anatomy of abdominal aortic aneurysms. In addition it can provide information concerning tissue type, i.e., it distinguished clot from moving blood. It may be possible in the future to further characterize atherosclerotic and other pathological changes in vessel architecture by using various pulse sequences and timing parameters to provide in vivo histological typing.

Evancho, A.; Osbakken, M.; Weidner, W.

1984-01-01

315

NMR of a Phospholipid: Modules for Advanced Laboratory Courses  

NASA Astrophysics Data System (ADS)

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.

Gaede, Holly C.; Stark, Ruth E.

2001-09-01

316

Sensitive and robust electrophoretic NMR: instrumentation and experiments.  

PubMed

Although simple as a concept, electrophoretic NMR (eNMR) has so far failed to find wider application. Problems encountered are mainly due to disturbing and partly irreproducible convection-like bulk flow effects from both electro-osmosis and thermal convection. Additionally, bubble formation at the electrodes and rf noise pickup has constrained the typical sample geometry to U-tube-like arrangements with a small filling factor and a low resulting NMR sensitivity. Furthermore, the sign of the electrophoretic mobility cancels out in U-tube geometries. We present here a new electrophoretic sample cell based on a vertically placed conventional NMR sample tube with bubble-suppressing palladium metal as electrode material. A suitable radiofrequency filter design prevents noise pickup by the NMR sample coil from the high-voltage leads which extend into the sensitive sample volume. Hence, the obtained signal-to-noise ratio of this cell is one order of magnitude higher than that of our previous U-tube cells. Permitted by the retention of the sign of the displacement-related signal phase in the new cell design, an experimental approach is described where bulk flow effects by electro-osmosis and/or thermal convection are compensated through parallel monitoring of a reference signal from a non-charged species in the sample. This approach, together with a CPMG-like pulse train scheme provides a superior first-order cancellation of non-electrophoretic bulk flow effects. PMID:18289894

Hallberg, Fredrik; Furó, István; Yushmanov, Pavel V; Stilbs, Peter

2008-05-01

317

Quantification of taurine in energy drinks using (1)H NMR.  

PubMed

The consumption of so called energy drinks is increasing, especially among adolescents. These beverages commonly contain considerable amounts of the amino sulfonic acid taurine, which is related to a magnitude of various physiological effects. The customary method to control the legal limit of taurine in energy drinks is LC-UV/vis with postcolumn derivatization using ninhydrin. In this paper we describe the quantification of taurine in energy drinks by (1)H NMR as an alternative to existing methods of quantification. Variation of pH values revealed the separation of a distinct taurine signal in (1)H NMR spectra, which was applied for integration and quantification. Quantification was performed using external calibration (R(2)>0.9999; linearity verified by Mandel's fitting test with a 95% confidence level) and PULCON. Taurine concentrations in 20 different energy drinks were analyzed by both using (1)H NMR and LC-UV/vis. The deviation between (1)H NMR and LC-UV/vis results was always below the expanded measurement uncertainty of 12.2% for the LC-UV/vis method (95% confidence level) and at worst 10.4%. Due to the high accordance to LC-UV/vis data and adequate recovery rates (ranging between 97.1% and 108.2%), (1)H NMR measurement presents a suitable method to quantify taurine in energy drinks. PMID:24094700

Hohmann, Monika; Felbinger, Christine; Christoph, Norbert; Wachter, Helmut; Wiest, Johannes; Holzgrabe, Ulrike

2014-05-01

318

(15)N chemical shift referencing in solid state NMR.  

PubMed

Solid-state NMR spectroscopy has much advanced during the last decade and provides a multitude of data that can be used for high-resolution structure determination of biomolecules, polymers, inorganic compounds or macromolecules. In some cases the chemical shift referencing has become a limiting factor to the precision of the structure calculations and we have therefore evaluated a number of methods used in proton-decoupled (15)N solid-state NMR spectroscopy. For (13)C solid-state NMR spectroscopy adamantane is generally accepted as an external standard, but to calibrate the (15)N chemical shift scale several standards are in use. As a consequence the published chemical shift values exhibit considerable differences (up to 22ppm). In this paper we report the (15)N chemical shift of several commonly used references compounds in order to allow for comparison and recalibration of published data and future work. We show that (15)NH4Cl in its powdered form (at 39.3ppm with respect to liquid NH3) is a suitable external reference as it produces narrow lines when compared to other reference compounds and at the same time allows for the set-up of cross-polarization NMR experiments. The compound is suitable to calibrate magic angle spinning and static NMR experiments. Finally the temperature variation of (15)NH4Cl chemical shift is reported. PMID:24746715

Bertani, Philippe; Raya, Jésus; Bechinger, Burkhard

2014-01-01

319

NMR structure of the human doppel protein.  

PubMed

The NMR structure of the recombinant human doppel protein, hDpl(24-152), contains a flexibly disordered "tail" comprising residues 24-51, and a globular domain extending from residues 52 to 149 for which a detailed structure was obtained. The globular domain contains four alpha-helices comprising residues 72-80 (alpha1), 101-115 (alpha2(a)), 117-121 (alpha2(b)), and 127-141 (alpha3), and a short two-stranded anti-parallel beta-sheet comprising residues 58-60 (beta1) and 88-90 (beta2). The fold of the hDpl globular domain thus coincides nearly identically with the structure of the murine Dpl protein. There are close similarities with the human prion protein (hPrP) but, similar to the situation with the corresponding murine proteins, hDpl shows marked local differences when compared to hPrP: the beta-sheet is flipped by 180 degrees with respect to the molecular scaffold formed by the four helices, and the beta1-strand is shifted by two residues toward the C terminus. A large solvent-accessible hydrophobic cleft is formed on the protein surface between beta2 and alpha3, which has no counterpart in hPrP. The helix alpha2 of hPrP is replaced by two shorter helices, alpha2(a) and alpha2(b). The helix alpha3 is shortened by more than two turns when compared with alpha3 of hPrP, which is enforced by the positioning of the second disulfide bond in hDpl. The C-terminal peptide segment 144-149 folds back onto the loop connecting beta2 and alpha2. All but four of the 20 conserved residues in the globular domains of hPrP and hDpl appear to have a structural role in maintaining a PrP-type fold. The conservation of R76, E96, N110 and R134 in hDpl, corresponding to R148, E168, N183 and R208 in hPrP suggests that these amino acid residues might have essential roles in the so far unknown functions of PrP and Dpl in healthy organisms. PMID:12595265

Lührs, Thorsten; Riek, Roland; Güntert, Peter; Wüthrich, Kurt

2003-03-01

320

Alternating current circuit theory and pulsed NMR (Nuclear Magnetic Resonance)  

NASA Astrophysics Data System (ADS)

Pulsed NMR, by definition, deals with time varying excitations. These excitations, supplied by resonant circuits which provide a pulse of radiofrequency (frequencies in the megahertz region) power to a resonant circuit containing, among other things, a coil of wire, or inductor, in which a sample under investigation is placed for purposes of the nuclear magnetic resonance experiment. There are therefore two features of the pulse NMR experiment. First is the fact that we have available a source of continuous wave (CW) alternating current at some angular frequency, omega, measured in radians per second. This source is generally supplied by an ultrastable device called a frequency synthesizer. The second feature of the pulsed NMR experiment is that the sample is not continuously irradiated, but a pulse of radiofrequency oscillation is applied to the sample. This report discusses alternating current theory, resonant circuits and the equipment used in this experiment.

Gerstein, B. C.

1987-06-01

321

High-dimensional NMR spectra for structural studies of biomolecules.  

PubMed

Recent developments in the acquisition and processing of NMR data sets facilitate the recording of ultra-high-resolution NMR spectra in a reasonable time. The new experiments allow easy resonance assignment for folded and unfolded proteins, as well as the precise determination of spectral parameters, for example, chemical shifts, NOE contacts, coupling constants or cross-correlated relaxation rates. Owing to exceptional resolution of 4D-6D spectroscopy, detailed studies of biomolecules of unprecedented complexity are now possible. Herein, the principles of acquisition and processing methods are presented. The main applications of high-dimensional NMR experiments, including backbone and side-chain resonance assignment in proteins, as well as heteronuclear edited NOE techniques are reviewed. PMID:23794393

Kazimierczuk, Krzysztof; Stanek, Jan; Zawadzka-Kazimierczuk, Anna; Ko?mi?ski, Wiktor

2013-09-16

322

Multiple chemical-shift-selective NMR imaging using stimulated echoes  

NASA Astrophysics Data System (ADS)

A new technique for chemical-shift-selective (CHESS) NMR imaging is described which enables cross-sectional imaging of positively selected, i.e., frequency-selective excited, resonance lines. The method relies on NMR sequences comprising three 90° rf pulses and detecting a so-called stimulated echo. Stimulated echo acquisition mode (STEAM) imaging has been described in a preceding paper. Here modified pulse and gradient sequences are reported that allow chemical-shift-selective imaging. Basically, image contributions belonging to a chemical component with a certain resonance frequency within an NMR spectrum can be selected by replacing one of the 90° pulses of a STEAM imaging sequence by a frequency-selective pulse. In particular, a "composite" image and an arbitrary number of CHESS images may be acquired simultaneously from the same slice. The extension of the combined CHESS STEAM experiment to multislice imaging is demonstrated.

Haase, Axel; Frahm, Jens

323

Toroid cavity/coil NMR multi-detector  

DOEpatents

An analytical device for rapid, non-invasive nuclear magnetic resonance (NMR) spectroscopy of multiple samples using a single spectrometer is provided. A modified toroid cavity/coil detector (TCD), and methods for conducting the simultaneous acquisition of NMR data for multiple samples including a protocol for testing NMR multi-detectors are provided. One embodiment includes a plurality of LC resonant circuits including spatially separated toroid coil inductors, each toroid coil inductor enveloping its corresponding sample volume, and tuned to resonate at a predefined frequency using a variable capacitor. The toroid coil is formed into a loop, where both ends of the toroid coil are brought into coincidence. Another embodiment includes multiple micro Helmholtz coils arranged on a circular perimeter concentric with a central conductor of the toroid cavity.

Gerald, II, Rex E. (Brookfield, IL); Meadows, Alexander D. (Indianapolis, IN); Gregar, Joseph S. (Naperville, IL); Rathke, Jerome W. (Homer Glen, IL)

2007-09-18

324

17O NMR spectroscopy: intramolecular hydrogen bonding in 7-hydroxyindanones  

NASA Astrophysics Data System (ADS)

Natural abundance 17O NMR chemical shift data for seven substituted indanones including four hydroxyindanones, three fluorenones including two hydroxyfluorenones, and seven 2-methyleneindanones including four hydroxymethyleneindanones, at 75°C in acetonitrile are reported. The hydroxyindanones, the one hydroxyfluorenone and the hydroxymethyleneindanones capable of intramolecular hydrogen bonding exhibit carbonyl 17O NMR signals which are shielded relative to those incapable of intramolecular hydrogen bonding. The intramolecular hydrogen bonding component (?? HB) of the carbonyl 17O NMR chemical shift was determined to be 9.8 ± 1.2 and 10.9 ± 1.4 ppm for the hydroxyindanones and the hydroxymethyleneindanones, respectively. The small ?? HB values for these hydroxyindanones relative to other ketone systems (about 50 ppm) are discussed in terms of molecular mechanics calculated hydrogen bond geometry.

Boykin, David W.; Kumar, Arvind

1993-10-01

325

NMR and protein folding: equilibrium and stopped-flow studies.  

PubMed Central

NMR studies are now unraveling the structure of intermediates of protein folding using hydrogen-deuterium exchange methodologies. These studies provide information about the time dependence of formation of secondary structure. They require the ability to assign specific resonances in the NMR spectra to specific amide protons of a protein followed by experiments involving competition between folding and exchange reactions. Another approach is to use 19F-substituted amino acids to follow changes in side-chain environment upon folding. Current techniques of molecular biology allow assignments of 19F resonances to specific amino acids by site-directed mutagenesis. It is possible to follow changes and to analyze results from 19F spectra in real time using a stopped-flow device incorporated into the NMR spectrometer.

Frieden, C.; Hoeltzli, S. D.; Ropson, I. J.

1993-01-01

326

NMR/MRI with hyperpolarized gas and high Tc SQUID  

DOEpatents

A method and apparatus for the detection of nuclear magnetic resonance (NMR) signals and production of magnetic resonance imaging (MRI) from samples combines the use of hyperpolarized inert gases to enhance the NMR signals from target nuclei in a sample and a high critical temperature (Tc) superconducting quantum interference device (SQUID) to detect the NMR signals. The system operates in static magnetic fields of 3 mT or less (down to 0.1 mT), and at temperatures from liquid nitrogen (77K) to room temperature. Sample size is limited only by the size of the magnetic field coils and not by the detector. The detector is a high Tc SQUID magnetometer designed so that the SQUID detector can be very close to the sample, which can be at room temperature.

Schlenga, Klaus (Eggenstein, DE); de Souza, Ricardo E. (Recife, BR); Wong-Foy, Annjoe (Berkeley, CA); Clarke, John (Berkeley, CA); Pines, Alexander (Berkeley, CA)

2000-01-01

327

NMR imaging of cell phone radiation absorption in brain tissue  

PubMed Central

A method is described for measuring absorbed electromagnetic energy radiated from cell phone antennae into ex vivo brain tissue. NMR images the 3D thermal dynamics inside ex vivo bovine brain tissue and equivalent gel under exposure to power and irradiation time-varying radio frequency (RF) fields. The absorbed RF energy in brain tissue converts into Joule heat and affects the nuclear magnetic shielding and the Larmor precession. The resultant temperature increase is measured by the resonance frequency shift of hydrogen protons in brain tissue. This proposed application of NMR thermometry offers sufficient spatial and temporal resolution to characterize the hot spots from absorbed cell phone radiation in aqueous media and biological tissues. Specific absorption rate measurements averaged over 1 mg and 10 s in the brain tissue cover the total absorption volume. Reference measurements with fiber optic temperature sensors confirm the accuracy of the NMR thermometry.

Gultekin, David H.; Moeller, Lothar

2013-01-01

328

Mobile sensor for high resolution NMR spectroscopy and imaging  

NASA Astrophysics Data System (ADS)

In this work we describe the construction of a mobile NMR tomograph with a highly homogeneous magnetic field. Fast MRI techniques as well as NMR spectroscopy measurements were carried out. The magnet is based on a Halbach array built from identical permanent magnet blocks generating a magnetic field of 0.22 T. To shim the field inhomogeneities inherent to magnet arrays constructed from these materials, a shim strategy based on the use of movable magnet blocks is employed. With this approach a reduction of the line-width from ˜20 kHz to less than 0.1 kHz was achieved, that is by more than two orders of magnitude, in a volume of 21 cm 3. Implementing a RARE sequence, 3D images of different objects placed in this volume were obtained in short experimental times. Moreover, by reducing the sample size to 1 cm 3, sub ppm resolution is obtained in 1H NMR spectra.

Danieli, Ernesto; Mauler, Jörg; Perlo, Juan; Blümich, Bernhard; Casanova, Federico

2009-05-01

329

An on-line NMR technique with a programmable processor  

SciTech Connect

Nuclear magnetic resonance (NMR) spectroscopy is used to determine molecular content of materials, mainly in laboratory measurements. The reduced cost of fast computer processors, together with recent break throughs in digital signal processor technology, has facilitated the on-line use of NMR by allowing modifications of the available technology. This paper describes a system and an algorithm for improving the on-line operations. It is base on the time-domain NMR signal detected by the controller and some prior knowledge of chemical signal patterns. The desired signal can be separated from a composite signal by using an adaptive line enhancer (ALE) filter. This technique would be useful for upgrading process procedures in on-line manufacturing.

Razazian, K.; Dieckman, S.L.; Raptis, A.C. [and others

1995-07-01

330

A fragment separator at LBL for beta-NMR experiment  

SciTech Connect

The Beam 44 fragment separator was built at the Bevalac of LBL for NMR studies of beta emitting nuclei. {sup 37}K, {sup 39}Ca, and {sup 43}Ti fragments originating from {sup 40}Ca and {sup 46}Ti primary beams were separated by the separator for NMR studies on these nuclei. Nuclear spin polarization was created in {sup 39}Ca and {sup 43}Ti using the tilted foil technique (TFT), and the magnetic moment of {sup 43}Ti was deduced. Fragment polarization was measured for {sup 37}K and {sup 39}Ca emitted to finite deflection angles. The Beam 44 fragment separator in combination with a proper polarization technique, such as TFT or fragment polarization, has been very effective for such NMR studies.

Matsuta, K.; Ozawa, A.; Nojiri, Y.; Minamisono, T.; Fukuda, M.; Kitagawa, A.; Ohtsubo, T.; Momota, S.; Fukuda, S.; Matsuo, Y.; Takechi, H.; Minami, I.; Sugimoto, K. [Osaka Univ., Toyonaka, Osaka, (Japan); Tanihata, I. [Riken, Inc., Wako, Saitama (Japan); Omata, K. [Tokyo Univ., Tanashi (Japan). Inst. for Nuclear Study; Shimoura, S. [Univ., of Tokyo, Bunkyo-ku, Tokyo, (Japan); Alonso, J.R.; Krebs, G.F.; Symons, T.J.M. [Lawrence Berkeley Lab., CA (United States)

1992-03-01

331

Advances in solid-state NMR of cellulose.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy is a well-established analytical and enabling technology in biofuel research. Over the past few decades, lignocellulosic biomass and its conversion to supplement or displace non-renewable feedstocks has attracted increasing interest. The application of solid-state NMR spectroscopy has long been seen as an important tool in the study of cellulose and lignocellulose structure, biosynthesis, and deconstruction, especially considering the limited number of effective solvent systems and the significance of plant cell wall three-dimensional microstructure and component interaction to conversion yield and rate profiles. This article reviews common and recent applications of solid-state NMR spectroscopy methods that provide insight into the structural and dynamic processes of cellulose that control bulk properties and biofuel conversion. PMID:24590189

Foston, Marcus

2014-06-01

332

NMR Studies of Quantum Rotors Confined in Zeolite  

NASA Astrophysics Data System (ADS)

We report the results of NMR studies of methane trapped in zeolite at low temperatures. Samples were prepared to contain 1.0±0.2 molecules per ?-sodalite cage of zeolite-13X. The NMR spin-spin and spin-lattice relaxation times were measured for 4< T<95 K to determine the rotational dynamics of the molecules and the dependence on the concentration of the A, T and E-molecular species. The results are discussed relative to recent Monte Carlo calculations that show that the molecules are localized but free to tumble in the large ?-cages at low temperatures. At higher temperatures there is an effective melting of the translational degrees of freedom for the lattice formed by the centers of the supercages. A sharp definitive jump in the NMR spin-spin relaxation is seen at this “melting” transition.

Ji, Yu; Hamida, J. A.; Sullivan, N. S.

2010-02-01

333

MAS NMR and FTIR spectra of framework aluminosilicates  

NASA Astrophysics Data System (ADS)

In the work, the results of 27Al MAS NMR studies carried out for structures of different framework aluminosilicates are presented. The spectra of natural clinoptilolite and its sodium and hydrogen forms were measured. The zeolite spectra were obtained before and after incorporation of heavy metal cations (Pb 2+, Cd 2+, Ni 2+ and Cr 3+) into the zeolite structure. After decomposition of the spectra into component peaks differences caused by ion exchange were observed. Additionally, NMR spectra of kalsilite (framework aluminosilicate, not belonging to zeolite group) and other zeolites (chabazite, heulandite and analcime) were measured. 27Al MAS NMR spectra of all the samples studied were compared with the FTIR spectra measured in the middle infrared region. Based on the results obtained it has been proved that the interpretation of spectra obtained using these two different techniques can give some information concerning changes occurring in various framework aluminosilicate structures.

Mozgawa, W.; Fojud, Z.; Handke, M.; Jurga, S.

2002-09-01

334

The present state of NMR tomography and its future.  

PubMed

The use of nuclear magnetic resonance (NMR) tomography requires close co-operation between radiologists and doctors working in nuclear medicine, so that experience gained in computed tomography and diagnostic function programmes can be exchanged. With regard to the technology of the magnets, the main demand at the moment is for imaging. In this area, special magnetic-field strengths, spools and evaluation procedures should be developed and optimised for the various applications. A list of guidelines must be worked out, and a strategy for the application of NMR tomography within general diagnostic procedures must be drawn up. Further progress will be brought about by developments such as breath and cardiac gating, as well as by the introduction of contrast media. In order to keep the cost of examinations within certain limits, it is necessary that plans are made to install an appropriate number of NMR devices. PMID:3956528

Hundeshagen, H

1986-01-01

335

A RF Preamplifier Design For Low Temperature NMR Experiments.  

NASA Astrophysics Data System (ADS)

It was reported by several research groups that the recently discovered possible supersolid state of solid ^4He has strong correlations with the presence of ^3He impurities and other defects. These observations aroused new interest in the NMR study of solid ^4He doped with ^3He. However, the extremely low concentration of ^3He (less than 100 ppm) and the long nuclear spin lattice relaxation times in the interested regime lead to a challenging task to achieve detectable NMR signals. We present a new design for a low temperature preamplifier working with a crossed-coil NMR probe. This preamplifier reduces the noise temperature to 1 K at a sample temperature as low as 250 mK when it is thermally anchored to the mixing chamber of a dilution refrigerator. With an adapted design, we are able to cool down the sample to about 10 mK and keep the noise temperature well below 4 K.

Kim, Sung Su; Huan, Chao; Phelps, Larry; Xia, Jian-Sheng; Sullivan, Neil; Candela, Donald

2010-03-01

336

NMR spectroscopy of RNA duplexes containing pseudouridine in supercooled water.  

PubMed

We have performed NMR experiments in supercooled water in order to decrease the temperature-dependent exchange of protons in RNA duplexes. NMR spectra of aqueous samples of RNA in bundles of narrow capillaries that were acquired at temperatures as low as -18 degrees C reveal resonances of exchangeable protons not seen at higher temperatures. In particular, we detected the imino protons of terminal base pairs and the imino proton of a non-base-paired pseudouridine in a duplex representing the eukaryotic pre-mRNA branch site helix. Analysis of the temperature dependence of chemical shift changes (thermal coefficients) for imino protons corroborated hydrogen bonding patterns observed in the NMR-derived structural model of the branch site helix. The ability to observe non-base-paired imino protons of RNA is of significant value in structure determination of RNA motifs containing loop and bulge regions. PMID:15987812

Schroeder, Kersten T; Skalicky, Jack J; Greenbaum, Nancy L

2005-07-01

337

NMR structure improvement: A structural bioinformatics & visualization approach  

NASA Astrophysics Data System (ADS)

The overall goal of this project is to enhance the physical accuracy of individual models in macromolecular NMR (Nuclear Magnetic Resonance) structures and the realism of variation within NMR ensembles of models, while improving agreement with the experimental data. A secondary overall goal is to combine synergistically the best aspects of NMR and crystallographic methodologies to better illuminate the underlying joint molecular reality. This is accomplished by using the powerful method of all-atom contact analysis (describing detailed sterics between atoms, including hydrogens); new graphical representations and interactive tools in 3D and virtual reality; and structural bioinformatics approaches to the expanded and enhanced data now available. The resulting better descriptions of macromolecular structure and its dynamic variation enhances the effectiveness of the many biomedical applications that depend on detailed molecular structure, such as mutational analysis, homology modeling, molecular simulations, protein design, and drug design.

Block, Jeremy N.

338

Magnetic state of FeCl3 investigated by NMR  

NASA Astrophysics Data System (ADS)

The spin state of FeCl3 was measured by Nuclear Magnetic Resonance (NMR) as a function of temperature and magnetic field. The sublattice magnetization obtained from the 57Fe NMR spectrum fits well with the theoretical prediction for an antiferromagnet with a magnetic anisotropy field of less than 70 mT in the ab-plane. The field dependence of the 57Fe NMR spectrum shows that a spin rotation plane of helical order starts to align perpendicularly to the external field direction as the field increases from 0 and ends around 4 T with no phase transition. From the spin tilting angle analysis, we obtained the quantitative relation among the exchange coupling constants.

Kang, Byeongki; Kim, Changsoo; Jo, Euna; Kwon, Sangil; Lee, Soonchil

2014-06-01

339

Ligand screening by saturation-transfer difference (STD) NMR spectroscopy.  

SciTech Connect

NMR based methods to screen for high-affinity ligands have become an indispensable tool for designing rationalized drugs, as these offer a combination of good experimental design of the screening process and data interpretation methods, which together provide unprecedented information on the complex nature of protein-ligand interactions. These methods rely on measuring direct changes in the spectral parameters, that are often simpler than the complex experimental procedures used to study structure and dynamics of proteins. The goal of this review article is to provide the basic details of NMR based ligand-screening methods, with particular focus on the saturation transfer difference (STD) experiment. In addition, we provide an overview of other NMR experimental methods and a practical guide on how to go about designing and implementing them.

Krishnan, V V

2005-04-26

340

An analytical methodology for magnetic field control in unilateral NMR.  

PubMed

Traditionally, unilateral NMR systems such as the NMR-MOUSE have used the fringe field between two bar magnets joined with a yoke in a 'U' geometry. This allows NMR signals to be acquired from a sensitive volume displaced from the magnets, permitting large samples to be investigated. The drawback of this approach is that the static field (B0) generated in this configuration is inhomogeneous, and has a large, nonlinear, gradient. As a consequence, the sensitive volume of the instrument is both small and ill defined. Empirical redesign of the permanent magnet array producing the B0 field has yielded instruments with magnetic field topologies acceptable for varying applications. The drawback of current approaches is the lack of formalism in the control of B0. Rather than tailoring the magnet geometry to NMR investigations, measurements must be tailored to the available magnet geometry. In this work, we present a design procedure whereby the size, shape, field strength, homogeneity, and gradients in the sensitive spot of a unilateral NMR sensor can be controlled. Our design uses high permeability pole pieces, shaped according to the contours of an analytical expression, to control B0, allowing unilateral NMR instruments to be designed to generate a controlled static field topology. We discuss the approach in the context of previously published design techniques, and explain the advantages inherent in our strategy as compared to other optimization methods. We detail the design, simulation, and construction of a unilateral magnet array using our approach. It is shown that the fabricated array exhibits a B0 topology consistent with the design. The utility of the design is demonstrated in a sample nondestructive testing application. Our design methodology is general, and defines a class of unilateral permanent magnet arrays in which the strength and shape of B0 within the sensitive volume can be controlled. PMID:15809175

Marble, Andrew E; Mastikhin, Igor V; Colpitts, Bruce G; Balcom, Bruce J

2005-05-01

341

An analytical methodology for magnetic field control in unilateral NMR  

NASA Astrophysics Data System (ADS)

Traditionally, unilateral NMR systems such as the NMR-MOUSE have used the fringe field between two bar magnets joined with a yoke in a 'U' geometry. This allows NMR signals to be acquired from a sensitive volume displaced from the magnets, permitting large samples to be investigated. The drawback of this approach is that the static field ( B0) generated in this configuration is inhomogeneous, and has a large, nonlinear, gradient. As a consequence, the sensitive volume of the instrument is both small and ill defined. Empirical redesign of the permanent magnet array producing the B0 field has yielded instruments with magnetic field topologies acceptable for varying applications. The drawback of current approaches is the lack of formalism in the control of B0. Rather than tailoring the magnet geometry to NMR investigations, measurements must be tailored to the available magnet geometry. In this work, we present a design procedure whereby the size, shape, field strength, homogeneity, and gradients in the sensitive spot of a unilateral NMR sensor can be controlled. Our design uses high permeability pole pieces, shaped according to the contours of an analytical expression, to control B0, allowing unilateral NMR instruments to be designed to generate a controlled static field topology. We discuss the approach in the context of previously published design techniques, and explain the advantages inherent in our strategy as compared to other optimization methods. We detail the design, simulation, and construction of a unilateral magnet array using our approach. It is shown that the fabricated array exhibits a B0 topology consistent with the design. The utility of the design is demonstrated in a sample nondestructive testing application. Our design methodology is general, and defines a class of unilateral permanent magnet arrays in which the strength and shape of B0 within the sensitive volume can be controlled.

Marble, Andrew E.; Mastikhin, Igor V.; Colpitts, Bruce G.; Balcom, Bruce J.

2005-05-01

342

MetAssimulo:Simulation of Realistic NMR Metabolic Profiles  

PubMed Central

Background Probing the complex fusion of genetic and environmental interactions, metabolic profiling (or metabolomics/metabonomics), the study of small molecules involved in metabolic reactions, is a rapidly expanding 'omics' field. A major technique for capturing metabolite data is 1H-NMR spectroscopy and this yields highly complex profiles that require sophisticated statistical analysis methods. However, experimental data is difficult to control and expensive to obtain. Thus data simulation is a productive route to aid algorithm development. Results MetAssimulo is a MATLAB-based package that has been developed to simulate 1H-NMR spectra of complex mixtures such as metabolic profiles. Drawing data from a metabolite standard spectral database in conjunction with concentration information input by the user or constructed automatically from the Human Metabolome Database, MetAssimulo is able to create realistic metabolic profiles containing large numbers of metabolites with a range of user-defined properties. Current features include the simulation of two groups ('case' and 'control') specified by means and standard deviations of concentrations for each metabolite. The software enables addition of spectral noise with a realistic autocorrelation structure at user controllable levels. A crucial feature of the algorithm is its ability to simulate both intra- and inter-metabolite correlations, the analysis of which is fundamental to many techniques in the field. Further, MetAssimulo is able to simulate shifts in NMR peak positions that result from matrix effects such as pH differences which are often observed in metabolic NMR spectra and pose serious challenges for statistical algorithms. Conclusions No other software is currently able to simulate NMR metabolic profiles with such complexity and flexibility. This paper describes the algorithm behind MetAssimulo and demonstrates how it can be used to simulate realistic NMR metabolic profiles with which to develop and test new data analysis techniques. MetAssimulo is freely available for academic use at http://cisbic.bioinformatics.ic.ac.uk/metassimulo/.

2010-01-01

343

Quantitating metabolites in protein precipitated serum using NMR spectroscopy.  

PubMed

Quantitative NMR-based metabolite profiling is challenged by the deleterious effects of abundant proteins in the intact blood plasma/serum, which underscores the need for alternative approaches. Protein removal by ultrafiltration using low molecular weight cutoff filters thus represents an important step. However, protein precipitation, an alternative and simple approach for protein removal, lacks detailed quantitative assessment for use in NMR based metabolomics. In this study, we have comprehensively evaluated the performance of protein precipitation using methanol, acetonitrile, perchloric acid, and trichloroacetic acid and ultrafiltration approaches using 1D and 2D NMR, based on the identification and absolute quantitation of 44 human blood metabolites, including a few identified for the first time in the NMR spectra of human serum. We also investigated the use of a "smart isotope tag," (15)N-cholamine for further resolution enhancement, which resulted in the detection of a number of additional metabolites. (1)H NMR of both protein precipitated and ultrafiltered serum detected all 44 metabolites with comparable reproducibility (average CV, 3.7% for precipitation; 3.6% for filtration). However, nearly half of the quantified metabolites in ultrafiltered serum exhibited 10-74% lower concentrations; specifically, tryptophan, benzoate, and 2-oxoisocaproate showed much lower concentrations compared to protein precipitated serum. These results indicate that protein precipitation using methanol offers a reliable approach for routine NMR-based metabolomics of human blood serum/plasma and should be considered as an alternative to ultrafiltration. Importantly, protein precipitation, which is commonly used by mass spectrometry (MS), promises avenues for direct comparison and correlation of metabolite data obtained from the two analytical platforms to exploit their combined strength in the metabolomics of blood. PMID:24796490

Nagana Gowda, G A; Raftery, Daniel

2014-06-01

344

Advanced NMR characterization of zeolite catalysts. Final technical report  

SciTech Connect

The effort described in this report involved a joint industry-university program between the Signal Research Center, Inc., and the University of Illinois, designed to advance the state of knowledge of zeolite catalyst characterization technology for application to zeolite catalysts useful in coal liquefaction related processes. The program involved the application of new and improved high resolution solid state nuclear magnetic resonance (NRM) techniques to the characterization of zeolite catalysts and other related microporous materials. The NMR experiments were performed in the state-of-the-art NMR laboratory at the University of Illinois. In this report the first comprehensive investigation of /sup 17/O NMR of A and Y zeolites by means of static, MASS and VASS (variable angle sample spinning) NMR techniques is presented. The determination of the /sup 17/O isotropic chemical shifts, nuclear quadrupole coupling constants and electric field gradient tensor asymmetry parameters provides valuable supplementary information on zeolite structure. As an extension of the /sup 17/O NMR investigation of zeolites, results for gallosilicates and for several aluminophosphate materials have also been obtained. The work presented in this study demonstrates the ability of using /sup 17/O NMR to observe chemical changes in the oxygen environment of zeolites. This has important implications for the study of zeolite based catalysts. Chemical modifications of catalysts, such as framework substitutions or ion exchange which are commonly used to modify zeolite catalyst activity can be directly studied for their effect on the oxygen rich surface of the zeolite. It is also possible that this technique could be used to directly probe the interactions between the zeolite surface and reactant molecules. 29 refs., 14 figs., 7 tabs.

Welsh, L.B.; Oldfield, E.

1986-03-01

345

Structural properties of carbon nanotubes derived from 13C NMR  

NASA Astrophysics Data System (ADS)

We present a detailed experimental and theoretical study on how structural properties of carbon nanotubes can be derived from 13C NMR investigations. Magic angle spinning solid state NMR experiments have been performed on single- and multiwalled carbon nanotubes with diameters in the range from 0.7 to 100 nm and with number of walls from 1 to 90. We provide models on how diameter and the number of nanotube walls influence NMR linewidth and line position. Both models are supported by theoretical calculations. Increasing the diameter D, from the smallest investigated nanotube, which in our study corresponds to the inner nanotube of a double-walled tube to the largest studied diameter, corresponding to large multiwalled nanotubes, leads to a 23.5 ppm diamagnetic shift of the isotropic NMR line position ?. We show that the isotropic line follows the relation ? = 18.3/D + 102.5 ppm, where D is the diameter of the tube and NMR line position ? is relative to tetramethylsilane. The relation asymptotically tends to approach the line position expected in graphene. A characteristic broadening of the line shape is observed with the increasing number of walls. This feature can be rationalized by an isotropic shift distribution originating from different diamagnetic shielding of the encapsulated nanotubes together with a heterogeneity of the samples. Based on our results, NMR is shown to be a nondestructive spectroscopic method that can be used as a complementary method to, for example, transmission electron microscopy to obtain structural information for carbon nanotubes, especially bulk samples.

Abou-Hamad, E.; Babaa, M.-R.; Bouhrara, M.; Kim, Y.; Saih, Y.; Dennler, S.; Mauri, F.; Basset, J.-M.; Goze-Bac, C.; Wågberg, T.

2011-10-01

346

NMR imaging of fluid dynamics in reservoir core.  

PubMed

A medical NMR imaging instrument has been modified to image water and oil in reservoir rocks by the construction of a new receiving coil. Both oil and water inside the core produced readily detectable proton NMR signals, while the rock matrix produced no signal. Because of similar T2 NMR relaxation times, the water was doped with a paramagnetic ion, Mn+2, to reduce its T2 relaxation time. This procedure enhanced the separation between the oil and water phases in the resulting images. Sequential measurements, as water imbibed into one end and oil was expelled from the other end of a core plug, produced a series of images which showed the dynamics of the fluids. For water-wet Berea Sandstone a flood front was readily observed, but some of the oil was apparently left behind in small, isolated pockets which were larger than individual pores. After several additional pore volumes of water flowed through the plug the NMR image indicated a homogeneous distribution of oil. The amount of residual oil, as determined from the ratio of NMR intensities, closely approximated the residual oil saturation of fully flooded Berea samples measured by Dean-Stark extraction. A Berea sandstone core treated to make it partially oil-wet, did not show a definitive flood front, but appeared to channel the water around the perimeter of the core plug. The relative ease with which these images were made indicates that NMR imaging can be a useful technique to follow the dynamics of oil and water through a core plug for a variety of production processes. PMID:3226235

Baldwin, B A; Yamanashi, W S

1988-01-01

347

Advanced NMR characterization of zeolite catalysts. Sixth quarterly report, 1 January 1985-31 March 1985  

SciTech Connect

The program discussed in this report is a two-year two-phase joint UOP-University of Illinois study of the application of improved high resolution solid state nuclear magnetic resonance (NMR) techniques to the characterization of zeolite catalysts. During the first phase of this program very pure, and in some cases isotopically enriched faujasites will be prepared and studied by magic angle sample spinning NMR (MASS NMR) and variable angle sample spinning NMR (VASS NMR) on 500 and 360 MHz (proton frequency) NMR spectrometers. The NMR techniques that will be emphasized are the measurement and analysis of the /sup 17/O NMR properties, /sup 27/Al NMR intensity quantitation, and /sup 27/Al and /sup 29/Si NMR relaxation rates. During the second phase of this program these NMR techniques will be used to study the effects of impurity concentration, dealumination treatments and cation exchange on the NMR properties of faujasites. The initial emphasis of this program during Phase I is on the preparation and measurement of the NMR properties of /sup 17/O enriched Na-Y faujasites. The effort in each phase is broken into four tasks: (1) zeolite preparation; (2) standard zeolite characterization; (3) measurement of zeolite NMR properties; and (4) analysis of NMR data. The main efforts during the sixth three-month period of the program have been in five areas: (1) Manuscript preparation of the /sup 17/O NMR results for faujasites, (2) Synthesis of Ga substituted faujasites, (3) Synthesis of /sup 17/O enriched AlPO-n microporous materials, (4) Preliminary /sup 17/O NMR studies of /sup 17/O enriched AlPO/sub 4/-5, and (5) Preliminary spin-lattice relaxation rate measurements of /sup 17/O enriched zeolites. 8 refs., 1 fig.

Welsh, L.B.

1985-04-01

348

Advanced NMR characterization of zeolite catalysts. Third quarterly report, March 1-May 31, 1984  

SciTech Connect

The program discussed in this report is a two-year two-phase joint UOP-University of Illinois study of the application of improved high resolution solid state nuclear magnetic resonance (NMR) techniques to the characterization of zeolite catalysts. During the first phase of this program very pure, and in some cases isotopically enriched faujasites will be prepared and studied by majic angle sample spinning NMR (MASS NMR) and variable angle sample spinning NMR (VASS NMR) on 500 and 360 MHz (Proton frequency) NMR spectrometers. During the second phase of this program these NMR techniques will be used to study the effects of impurity concentration, dealumination treatments and cation exchange on the NMR properties of faujasites. The initial emphasis of this program during Phase I is on the preparation and measurement of the NMR properties of /sup 17/O enriched Na-Y faujasites. The effort in each phase is broken into four tasks: (1) zeolite preparation. (2) standard zeolite characterization; (3) measurement of zeolite NMR properties; and (4) analysis of NMR data. The main efforts during the third three month period of the program have been the characterization of the /sup 17/O enriched zeolites, particularly X and Y zeolites, by high resolution sample spinning /sup 17/O NMR, and the preparation of additional /sup 17/O enriched zeolites. X and Y zeolites with Si/Al framework ratios from 1.22 to 7.6 have been prepared in either the Na, NH/sub 4/ or Ba form. MASS NMR and VASS NMR as well as static NMR measurements have been made on these materials for /sup 17/O NMR frequencies from 20.4 to 67.8 MHz. Computer simulations of the experimental NMR lineshapes are in progress. Results to date indicate that the observed spectra arise from two different types of oxygen sites, possibly O in Al-O-Si links and chemically bound OH groups. 2 references, 1 figure, 1 table.

Welsh, L.B.

1984-06-01

349

Advanced NMR characterization of zeolite catalysts. Fourth quarterly report, 1 June 1984-31 August 1984  

SciTech Connect

The program discussed in this report is a two-year two-phase joint UOP-University of Illinois study of the application of improved high resolution solid state nuclear magnetic resonance (NMR) techniques to the characterization of zeolite catalysts. During the first phase of this program very pure, and in some cases isotopically enriched faujasites will be prepared and studied by magic angle sample spinning NMR (MASS NMR) and variable angle sample spinning NMR (VASS NMR) on 500 and 360 MHz (Proton frequency) NMR spectrometers. The NMR techniques that will be emphasized are the measurement and analysis of the /sup 17/O NMR properties, /sup 27/Al NMR intensity quantitation, and /sup 27/Al and /sup 29/Si NMR relaxation rates. During the second phase of this program these NMR techniques will be used to study the effects of impurity concentration, dealumination treatments and cation exchange on the NMR properties of faujasites. The initial emphasis of this program during Phase I is on the preparation and measurement of the NMR properties of /sup 17/O enriched Na-Y faujasites. The main efforts during the fourth three-month period of the program continue to be the characterization of the /sup 17/O enriched zeolites, particularly X and Y zeolites, by both static and sample spinning /sup 17/O NMR. The main emphasis has been on obtaining NMR data with both hydrated and calcined samples and simulating the static /sup 17/O NMR line. The complex /sup 17/O NMR spectrum can be simulated by two quadrupolar spectra, one coming from oxygen in a Si-O-Si configuration and one from oxygen in an Al-O-Si configuration. Good simulations have been obtained for zeolite A (only Si-O-Al), dealuminated zeolite Y (mainly Si-O-Si) and zeolite Y with a Si/Al ratio of about 2.8. 1 figure, 1 table.

Welsh, L.B.

1984-09-01

350

NMR probe of metallic states in nanoscale topological insulators.  

PubMed

A 125Te NMR study of bismuth telluride nanoparticles as a function of particle size revealed that the spin-lattice relaxation is enhanced below 33 nm, accompanied by a transition of NMR spectra from the single to the bimodal regime. The satellite peak features a negative Knight shift and higher relaxivity, consistent with core polarization from p-band carriers. Whereas nanocrystals follow a Korringa law in the range 140-420 K, micrometer particles do so only below 200 K. The results reveal increased metallicity of these nanoscale topological insulators in the limit of higher surface-to-volume ratios. PMID:23383927

Koumoulis, Dimitrios; Chasapis, Thomas C; Taylor, Robert E; Lake, Michael P; King, Danny; Jarenwattananon, Nanette N; Fiete, Gregory A; Kanatzidis, Mercouri G; Bouchard, Louis-S

2013-01-11

351

Experimental quantum deletion in an NMR quantum information processor  

NASA Astrophysics Data System (ADS)

We report an NMR experimental realization of a rapid quantum deletion algorithm that deletes marked states in an unsorted database. Unlike classical deletion, where search and deletion are equivalent, quantum deletion can be implemented with only a single query, which achieves exponential speed-up compared to the optimal classical analog. In the experimental realization, the GRAPE algorithm was used to obtain an optimized NMR pulse sequence, and the efficient method of maximum-likelihood has been used to reconstruct the experimental output state.

Long, Yu; Feng, GuanRu; Pearson, Jasong; Long, GuiLu

2014-07-01

352

Experimental quantum deletion in an NMR quantum information processor  

NASA Astrophysics Data System (ADS)

We report an NMR experimental realization of a rapid quantum deletion algorithm that deletes marked states in an unsorted database. Unlike classical deletion, where search and deletion are equivalent, quantum deletion can be implemented with only a single query, which achieves exponential speed-up compared to the optimal classical analog. In the experimental realization, the GRAPE algorithm was used to obtain an optimized NMR pulse sequence, and the efficient method of maximum-likelihood has been used to reconstruct the experimental output state.

Long, Yu; Feng, GuanRu; Pearson, Jasong; Long, GuiLu

2014-05-01

353

Hammett constants and NMR shifts of ?-acyloxy carboxamide derivatives  

NASA Astrophysics Data System (ADS)

Geometrical structures, Hammett constants, 1H and 13C chemical shift values, molecular electrostatic potential maps, and several thermodynamic parameters of ?-acyloxy carboxamide derivatives ( 4a- o) were calculated using HF and DFT/B3LYP methods with 6-31G( d) basis set. The optimized structures were compared with analogous compound. The 1H and 13C NMR shielding tensors were computed with the Gauge-Independent Atomic Orbital (GIAO) method. Comparison of the experimental 1H and 13C NMR chemical shifts of 4a- o molecules with the theoretical data indicates good agreement.

Vessally, Esmail; Edjlali, Ladan; Saber, Maryam; Aryana, Soma

2012-05-01

354

NMR, XRD and IR study on microcrystalline opals  

Microsoft Academic Search

Microcrystalline opal-CT and opal-C were investigated by 29Si MAS NMR and 29Si {1H} cross polarisation MAS NMR spectroscopy, X-ray small angle scattering, X-ray powder diffraction and infrared absorption\\u000a spectroscopy. The results are compared with those for non-crystalline precious opal (opal-AG), non-crystalline hyalite (opal-AN),\\u000a moderately disordered cristobalite and with well ordered low-cristobalite and low-tridymite. Opal-C is confirmed to be strongly\\u000a stacking

H. Graetsch; H. Gies; I. Topalovi?

1994-01-01

355

NMR metabolomics of human blood and urine in disease research.  

PubMed

This paper reviews the main applications of NMR metabolomics of blood and urine in disease research, over the last 5 years. The broad range of disease types addressed attests the increasing interest within the academic and medical communities to explore the recognised potential of metabolomics to (1) provide insight into underlying disease pathogenesis and (2) unveil new metabolic markers for disease diagnosis and follow up. Importantly, most recent studies reveal an increasing awareness of possible limitations and pitfalls of the metabolomics approach, together with efforts for improved study design and statistical validation, which are crucial requisites for the sound development of NMR metabolomics and its progress into the clinical setting. PMID:24854435

Duarte, Iola F; Diaz, Sílvia O; Gil, Ana M

2014-05-01

356

In situ NMR analysis of fluids contained in sedimentary rock  

PubMed

Limitations of resolution and absorption in standard chemical spectroscopic techniques have made it difficult to study fluids in sedimentary rocks. In this paper, we show that a chemical characterization of pore fluids may be obtained in situ by magic angle spinning (MAS) nuclear magnetic resonance (NMR), which is normally used for solid samples. 1H MAS-NMR spectra of water and crude oil in Berea sandstone show sufficient chemical shift resolution for a straightforward determination of the oil/water ratio. Copyright 1998 Academic Press. PMID:9716484

de Swiet TM; Tomaselli; Hurlimann; Pines

1998-08-01

357

Protein structure determination with paramagnetic solid-state NMR spectroscopy.  

PubMed

Many structures of the proteins and protein assemblies that play central roles in fundamental biological processes and disease pathogenesis are not readily accessible via the conventional techniques of single-crystal X-ray diffraction and solution-state nuclear magnetic resonance (NMR). On the other hand, many of these challenging biological systems are suitable targets for atomic-level structural and dynamic analysis by magic-angle spinning (MAS) solid-state NMR spectroscopy, a technique that has far less stringent limitations on the molecular size and crystalline state. Over the past decade, major advances in instrumentation and methodology have prompted rapid growth in the field of biological solid-state NMR. However, despite this progress, one challenge for the elucidation of three-dimensional (3D) protein structures via conventional MAS NMR methods is the relative lack of long-distance data. Specifically, extracting unambiguous interatomic distance restraints larger than ?5 Å from through-space magnetic dipole-dipole couplings among the protein (1)H, (13)C, and (15)N nuclei has proven to be a considerable challenge for researchers. It is possible to circumvent this problem by extending the structural studies to include several analogs of the protein of interest, intentionally modified to contain covalently attached paramagnetic tags at selected sites. In these paramagnetic proteins, the hyperfine couplings between the nuclei and unpaired electrons can manifest themselves in NMR spectra in the form of relaxation enhancements of the nuclear spins that depend on the electron-nucleus distance. These effects can be significant for nuclei located up to ?20 Å away from the paramagnetic center. In this Account, we discuss MAS NMR structural studies of nitroxide and EDTA-Cu(2+) labeled variants of a model 56 amino acid globular protein, B1 immunoglobulin-binding domain of protein G (GB1), in the microcrystalline solid phase. We used a set of six EDTA-Cu(2+)-tagged GB1 mutants to rapidly determine the global protein fold in a de novo fashion. Remarkably, these studies required quantitative measurements of only approximately four or five backbone amide (15)N longitudinal paramagnetic relaxation enhancements per residue, in the complete absence of the usual internuclear distance restraints. Importantly, this paramagnetic solid-state NMR methodology is general and can be directly applied to larger proteins and protein complexes for which a significant fraction of the signals can be assigned in standard 2D and 3D MAS NMR chemical shift correlation spectra. PMID:23464364

Sengupta, Ishita; Nadaud, Philippe S; Jaroniec, Christopher P

2013-09-17

358

Nonuniform sampling and maximum entropy reconstruction in multidimensional NMR.  

PubMed

NMR spectroscopy is one of the most powerful and versatile analytic tools available to chemists. The discrete Fourier transform (DFT) played a seminal role in the development of modern NMR, including the multidimensional methods that are essential for characterizing complex biomolecules. However, it suffers from well-known limitations: chiefly the difficulty in obtaining high-resolution spectral estimates from short data records. Because the time required to perform an experiment is proportional to the number of data samples, this problem imposes a sampling burden for multidimensional NMR experiments. At high magnetic field, where spectral dispersion is greatest, the problem becomes particularly acute. Consequently multidimensional NMR experiments that rely on the DFT must either sacrifice resolution in order to be completed in reasonable time or use inordinate amounts of time to achieve the potential resolution afforded by high-field magnets. Maximum entropy (MaxEnt) reconstruction is a non-Fourier method of spectrum analysis that can provide high-resolution spectral estimates from short data records. It can also be used with nonuniformly sampled data sets. Since resolution is substantially determined by the largest evolution time sampled, nonuniform sampling enables high resolution while avoiding the need to uniformly sample at large numbers of evolution times. The Nyquist sampling theorem does not apply to nonuniformly sampled data, and artifacts that occur with the use of nonuniform sampling can be viewed as frequency-aliased signals. Strategies for suppressing nonuniform sampling artifacts include the careful design of the sampling scheme and special methods for computing the spectrum. Researchers now routinely report that they can complete an N-dimensional NMR experiment 3(N-1) times faster (a 3D experiment in one ninth of the time). As a result, high-resolution three- and four-dimensional experiments that were prohibitively time consuming are now practical. Conversely, tailored sampling in the indirect dimensions has led to improved sensitivity. Further advances in nonuniform sampling strategies could enable further reductions in sampling requirements for high resolution NMR spectra, and the combination of these strategies with robust non-Fourier methods of spectrum analysis (such as MaxEnt) represent a profound change in the way researchers conduct multidimensional experiments. The potential benefits will enable more advanced applications of multidimensional NMR spectroscopy to study biological macromolecules, metabolomics, natural products, dynamic systems, and other areas where resolution, sensitivity, or experiment time are limiting. Just as the development of multidimensional NMR methods presaged multidimensional methods in other areas of spectroscopy, we anticipate that nonuniform sampling approaches will find applications in other forms of spectroscopy. PMID:24400700

Hoch, Jeffrey C; Maciejewski, Mark W; Mobli, Mehdi; Schuyler, Adam D; Stern, Alan S

2014-02-18

359

Assigning the NMR Spectrum of Glycidol: An Advanced Organic Chemistry Exercise  

ERIC Educational Resources Information Center

Various one- and two-dimensional NMR experiments have been found to be extremely useful for assigning the proton and carbon NMR spectra of glycidol. The technique provides extremely valuable information aiding in the complete assignment of the peaks.

Helms, Eric; Arpaia, Nicholas; Widener, Melissa

2007-01-01

360

COMPREHENSIVE PROGRESS REPORT FOR FOURIER TRANSFORM NMR (NUCLEAR MAGNETIC RESONANCE) OF METALS OF ENVIRONMENTAL SIGNIFICANCE  

EPA Science Inventory

Interactions of the metals cadmium and selenium with various biologically important substrates were studied by nuclear magnetic resonance (NMR) spectroscopy. Cadmium-113 NMR was used for a critical examination of three metalloproteins: concanavalin A, bovine superoxide dismutase ...

361

NMR methods for structural studies of large monomeric and multimeric proteins.  

PubMed

NMR structural studies of large monomeric and multimeric proteins face distinct challenges. In large monomeric proteins, the common occurrence of frequency degeneracies between residues impedes unambiguous assignment of NMR signals. To overcome this barrier, nonuniform sampling (NUS) is used to measure spectra with optimal resolution within reasonable time, new correlation maps resolve previous impasses in assignment strategies, and novel selective methyl labeling schemes provide additional structural probes without cluttering NMR spectra. These advances push the limits of NMR studies of large monomeric proteins. Large multimeric and multidomain proteins are studied by NMR when individual components can also be studied by NMR and have known structures. The structural properties of large assemblies are obtained by identifying binding surfaces, by orienting domains, and employing limited distance constraints. Segmental labeling and the combination of NMR with other methods have helped popularize NMR studies of such systems. PMID:23850141

Frueh, Dominique P; Goodrich, Andrew C; Mishra, Subrata H; Nichols, Scott R

2013-10-01

362

De-noising methods for NMR logging echo signals based on wavelet transform  

NASA Astrophysics Data System (ADS)

The signal-to-noise ratio (SNR) of the echo signals in nuclear magnetic resonance (NMR) is one of the most important factors that affect the effective application of NMR logging. Wavelet transform can be used to remove the noise and improve the SNR of echo signals in NMR logging. This paper uses three de-noising methods to treat the NMR echo signals: modulus maxima, spatial correlation and wavelet threshold based on wavelet transform. The effects of the three methods in the noise reduction of NMR echo signals were compared by numerical simulation, core experiment and NMR logging data. The results show that while these three methods can all effectively improve the SNR of NMR echo signals and the NMR T2 inversion results, the most effective among them is the wavelet threshold method, which can obtain a higher SNR and provides more accurate formation porosity.

Xie, Ranhong; Wu, Youbin; Liu, Kang; Liu, Mi; Xiao, Lizhi

2014-06-01

363

Covariance NMR in higher dimensions: application to 4D NOESY spectroscopy of proteins  

Microsoft Academic Search

Elucidation of high-resolution protein structures by NMR spectroscopy requires a large number of distance constraints that\\u000a are derived from nuclear Overhauser effects between protons (NOEs). Due to the high level of spectral overlap encountered\\u000a in 2D NMR spectra of proteins, the measurement of high quality distance constraints requires higher dimensional NMR experiments.\\u000a Although four-dimensional Fourier transform (FT) NMR experiments can

David A. Snyder; Fengli Zhang; Rafael Brüschweiler

2007-01-01

364

LC-NMR Technique in the Analysis of Phytosterols in Natural Extracts  

PubMed Central

The ability of LC-NMR to detect simultaneously free and conjugated phytosterols in natural extracts was tested. The advantages and disadvantages of a gradient HPLC-NMR method were compared to the fast composition screening using SEC-NMR method. Fractions of free and conjugated phytosterols were isolated and analyzed by isocratic HPLC-NMR methods. The results of qualitative and quantitative analyses were in a good agreement with the literature data.

Hornik, Stepan; Sajfrtova, Marie; Sykora, Jan; Brezinova, Anna; Wimmer, Zdenek

2013-01-01

365

Broadband SQUID NMR with Room-Temperature Samples  

Microsoft Academic Search

Superconducting quantum interference devices (SQUIDs) are the most sensitive detectors of magnetic fields. We have used an untuned broadband SQUID detector to detect transverse nuclear magnetic-resonance signals from samples of mineral oil, salt water, and animal tissue at room temperature. Proton NMR signals have been detected from about 20 to 450 kHz. We have also detected fluorine, sodium, and possibly

S. Kumar; B. D. Thorson; W. F. Avrin

1995-01-01

366

Towards a NMR implementation of a quantum lattice gas algorithm  

Microsoft Academic Search

Recent theoretical results suggest that an array of quantum information processors communicating via classical channels can be used to solve fluid dynamics problems. Quantum lattice-gas algorithms (QLGA) running on such architectures have been shown to solve the diffusion equation and the nonlinear Burgers equations. In this report, we describe progress towards an ensemble nuclear magnetic resonance (NMR) implementation of a

Marco A. Pravia; Zhiying Chen; Jeffrey Yepez; David G. Cory

2002-01-01

367

Extended hopane derivatives in sediments - Identification by H-1 NMR  

NASA Technical Reports Server (NTRS)

Sedimentary C32 hopanoic acid, one of the most abundant in nature and of probable bacterial origin, has been isolated for the first time as a single component and characterized by H-1 NMR. The 17 alpha H, 21 beta H configuration of the C31 alkane has been similarly confirmed.

Taylor, J.; Wardroper, A. M. K.; Maxwell, J. R.

1980-01-01

368

An NMR Study of the Protolysis Kinetics of Glycine.  

National Technical Information Service (NTIS)

The exchange of protons between the amino group of glycine and aqueous solvent was investigated by means of its effect upon the proton high resolution n.m.r. spectrum of the methylene group. The mean lifetime between exchanges of protons in the NH3(+) gro...

M. Sheinblatt H. S. Gutowsky

1964-01-01

369

Amplification of Xenon NMR and MRI by remote detection  

SciTech Connect

A novel technique is proposed in which a nuclear magneticresonance (NMR) spectrum or magnetic resonance image (MRI) is encoded andstored as spin polarization and is then moved to a different physicallocation to be detected. Remote detection allows the separateoptimization of the encoding and detection steps, permitting theindependent choice of experimental conditions, and excitation anddetection methodologies. In the first experimental demonstration of thistechnique, we show that NMR signal can be amplified by taking diluted129Xe from a porous sample placed inside a large encoding coil, andconcentrating it into a smaller detection coil. In general, the study ofNMR active molecules at low concentration that have low physical fillingfactor is facilitated by remote detection. In the second experiment, MRIinformation encoded in a very low field magnet (4-7mT) is transferred toa high field magnet (4.2 T) in order to be detected under optimizedconditions. Furthermore, remote detection allows the utilization ofultra-sensitive optical or superconducting detection techniques, whichbroadens the horizon of NMR experimentation.

Moule, Adam J.; Spence, Megan M.; Han, Song-I.; Seeley, JulietteA.; Pierce, Kimberly L.; Saxena, Sunil; Pines, Alexander

2003-03-31

370

Application of NMR shock barometer to naturally shocked minerals  

SciTech Connect

The shock-loading of natural materials by an impact, such as a comet or meteorite, can result in the formation of modified and altered phases in the target rock. In order to characterize the resulting material and to evaluate the extent of shock modification, the authors have used nuclear magnetic resonance (NMR) spectroscopy to examine several natural and experimentally shocked minerals. NMR spectroscopy is used to characterize the formation of high pressure silica polymorphs and amorphous material associated with the shocked Coconino Sandstone from Meteor Crater, Arizona. Five samples of the sandstone were obtained from several locations at the crater to represent a range of shock conditions associated with the hypervelocity impact of a 30 meter-diameter meteorite. The NMR spectra for these powdered materials exhibit peaks assigned to quartz, coesite, stishovite, and glass. A new resonance, identified as a densified form of amorphous silica with silicon in tetrahedra with one hydroxyl group, is observed for two of the moderately shocked samples. Experimental shock-loading of dry and water-saturated Coconino Sandstone powders provides shock-metamorphosed material that exhibit broadening of NMR resonances with increasing shock pressure, but no evidence of the new dense silica phase.

Cygan, R.T.; Boslough, M.B.

1994-07-01

371

NMR spectroscopy for determination of cationic polymer concentrations  

Microsoft Academic Search

Organic polyelectrolytes are utilized extensively in wastewater treatment, but their fate after use is poorly understood. Analytical methods used for polymer determination in less complex systems appear to fail in application to wastewater systems, contributing to the lack of knowledge. Thus, the development of 1H NMR spectroscopy is reported here for specifically quantitating certain cationic flocculant polymers in environmental samples.

Lin-Li Chang; Martha D Bruch; Nancy J Griskowitz; Steven K Dentel

2002-01-01

372

A decade in prostate cancer: from NMR to metabolomics  

Microsoft Academic Search

Over the past 30 years, continuous progress in the application of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance spectroscopic imaging (MRSI) to the detection, diagnosis and characterization of human prostate cancer has turned what began as scientific curiosity into a useful clinical option. In vivo MRSI technology has been integrated into the daily care of prostate cancer patients, and

Elita M. DeFeo; Chin-Lee Wu; W. Scott McDougal; Leo L. Cheng

2011-01-01

373

Pseudo-capsule assemblies characterized by 19F NMR techniques.  

PubMed

The formation of capsule-like dynamic assemblies which do not rely on attractions between host subunits was achieved via specific interactions with fluorinated guests. Characterization of these three component assemblies was accomplished by applications of (19)F NMR spectroscopy. PMID:19199607

Lledó, Agustí; Restorp, Per; Rebek, Julius

2009-02-25

374

13C-NMR study of cresyl benzoates  

NASA Astrophysics Data System (ADS)

The proton-decoupled 13C FT—NMR spectra of para-, meta- and ortho-cresyl benzoates have been recorded and the observed signals have been assigned following the substituent additivity rule. The important features of diagnostic value of these spectra are discussed.

Srivastava, S. P.; Bhatnagar, A. K.; Joshi, G. C.

375

Self-diffusion NMR imaging using stimulated echoes  

NASA Astrophysics Data System (ADS)

NMR imaging of molecular self-diffusion is demonstrated for the first time using stimulated-echo (STE) NMR signals. Stimulated-echo acquisition-mode (STEAM) imaging has been described in a preceding paper. It is based on a 90°- t1-90°- t2-90°- t3 rf excitation sequence and relies on the detection of the STE signal appearing at t3 = t1. By incorporating a pair of pulsed magnetic field gradients into the first and third intervals of the STEAM sequence, the effect of molecular self-diffusion on NMR images may be qualitatively demonstrated. A variation of the strength of the gradient pulses and/or the diffusion time, i.e., the length of the second interval, yields a series of diffusion weighted images which allows the calculation of a synthetical image solely displaying the self-diffusion coefficient. Experimental results on 1H NMR images of phantoms are presented which clearly demonstrate the potential of diffusion imaging as a new tool in medical diagnosis as well as for nonmedical applications.

Merboldt, Klaus-Dietmar; Hanicke, Wolfgang; Frahm, Jens

376

NMR imaging of spin-lattice relaxation using stimulated echoes  

NASA Astrophysics Data System (ADS)

A new NMR imaging technique is presented which allows a detailed determination of the spin-lattice relaxation behavior. Both the spatial resolution and the measuring time are the same as for a conventional NMR image. The experiment yields a series of cross-sectional images with intensities declining according to the T1 relaxation curve. The technique is based on the principles of stimulated-echo acquisition-mode (STEAM) imaging which have been described in a preceding paper. For T1 imaging the final 90° rf pulse of the basic three-pulse STEAM imaging sequence is split into a variable number of small-angle rf pulses. Each of these pulses should read out the same amount of the longitudinal magnetization which has been prepared by the two leading 90° pulses. They give rise to a series of stimulated echoes with a T1 weighting which depends on the length of the interval between the second 90° pulse and the readout pulse. STEAM T1, imaging is characterized by an extremely low rf power deposition and, therefore, will be suitable for high-field NMR imaging. The method is easily extended to multislice measurements as well as to chemical-shift-selective (CHESS) T1 imaging. 1H NMR images have been obtained at 100 MHz using a 2.3 T magnet with a bore of 40 cm.

Haase, Axel; Frahm, Jens

377

Solid-State NMR Spectroscopy for the Physical Chemistry Laboratory  

ERIC Educational Resources Information Center

Solid-state nuclear magnetic resonance (NMR) spectroscopy finds growing application to inorganic and organic materials, biological samples, polymers, proteins, and cellular membranes. However, this technique is often neither included in laboratory curricula nor typically covered in undergraduate courses. On the other hand, spectroscopy and…

Kinnun, Jacob J.; Leftin, Avigdor; Brown, Michael F.

2013-01-01

378

NMR solution structure of the human prion protein  

Microsoft Academic Search

The NMR structures of the recombinant human prion protein, hPrP(23-230), and two C-terminal fragments, hPrP(90-230) and hPrP(121-230), include a globular domain extending from residues 125-228, for which a detailed structure was obtained, and an N-terminal flexibly disordered \\

Ralph Zahn; Aizhuo Liu; Thorsten Lührs; Roland Riek; Christine von Schroetter; Francisco López García; Martin Billeter; Luigi Calzolai; Gerhard Wider; Kurt Wüthrich

2000-01-01

379

Flexibility of ZIF-8 materials studied using 129Xe NMR.  

PubMed

Structural changes in a porous hybrid inorganic-organic ZIF-8 compound have been explored using hyperpolarized (129)Xe NMR of adsorbed xenon at various temperatures. Upon xenon adsorption at low temperature, the organic linkers undergo a reorientation leading to a stepwise increase in xenon adsorption and in chemical shift. PMID:23862180

Springuel-Huet, Marie-Anne; Nossov, Andrei; Guenneau, Flavien; Gédéon, Antoine

2013-08-28

380

NMR-based metabonomic study of transgenic maize  

Microsoft Academic Search

The aim of this research was to verify the possibility of identifying and classifying maize seeds obtained from transgenic plants, in different classes according to the modification, on the basis of the concerted variation in metabolite levels detected by NMR spectra. It was possible to recognise the discriminant metabolites of transgenic samples as well as to classify non-a priori defined

Cesare Manetti; Cristiano Bianchetti; Mariano Bizzarri; Lorena Casciani; Cecilia Castro; Giuseppe D’Ascenzo; Maurizio Delfini; Maria Enrica Di Cocco; Aldo Laganà; Alfredo Miccheli; Mario Motto; Filippo Conti

2004-01-01

381

Solid-state NMR of flavins and flavoproteins.  

PubMed

Why apply solid-state NMR (SSNMR) to flavins and flavoproteins? NMR provides information on an atom-specific basis about chemical functionality, structure, proximity to other groups, and dynamics of the system. Thus, it has become indispensable to the study of chemicals, materials, catalysts, and biomolecules. It is no surprise then that NMR has a great deal to offer in the study of flavins and flavoenzymes. In general, their catalytic or electron-transfer activity resides essentially in the flavin, a molecule eminently accessible by NMR. However, the specific reactivity displayed depends on a host of subtle interactions whereby the protein biases and reshapes the flavin's propensities to activate it for one reaction while suppressing other aspects of this cofactor's prodigious repertoire (Massey et al., J Biol Chem 244:3999-4006, 1969; Müller, Z Naturforsch 27B:1023-1026, 1972; Joosten and van Berkel, Curr Opin Struct Biol 11:195-202, 2007). Thus, we are fascinated to learn about how the flavin cofactor of one enzyme is, and is not, like the flavin cofactor of another. In what follows, we describe how the capabilities of SSNMR can help and are beginning to bear fruit in this exciting endeavor. PMID:24764096

Miller, Anne-Frances

2014-01-01

382

Multinuclear NMR studies of gaseous and liquid sevoflurane  

NASA Astrophysics Data System (ADS)

For the first time, a small amount of sevoflurane ((CF 3) 2CHOCH 2F) in carbon dioxide and xenon as the gaseous solvents has been studied using 19F and 1H NMR spectra. Density-dependent 19F and 1H nuclear magnetic shielding was observed when the pressure of each solvent was increased. After extrapolation of the results to the zero-density limit it was possible to determine the appropriate shielding constants free from intermolecular interactions, ?0(F) and ?0(H). Similar procedure has also been applied for the investigation of fluorine-proton spin-spin couplings and the 2J 0(FH) and 3J 0(FH) constants of an isolated (CF 3) 2CHOCH 2F molecule were also obtained. Additionally, high-resolution 1H, 13C, 17O and 19F NMR spectra of pure liquid sevoflurane were also recorded and all the 1H- 13C, 1H- 19F and 19F- 13C spin-spin coupling constants and NMR chemical shifts were measured. It is shown that the experimental NMR parameters are suitable for comparison with the results of recent quantum-chemical calculations.

Maci?ga, E.; Makulski, W.; Jackowski, K.; Blicharska, B.

2006-03-01

383

Natural abundance 17O NMR study of ?-substituted methyl acetates  

NASA Astrophysics Data System (ADS)

Natural abundance 17O NMR chemical shift data for 10 substituted methyl acetates and 7 analogs, recorded in acetonitrile at 75°C, are reported. Variation in the carbonyl and single-bond oxygen signal are observed for formal ?-substitution and do not correlate with inductive effects. The data appear to be consistent with ? effects for analogous systems.

Boykin, D. W.; Subramanian, T. S.; Baumstark, A. L.

1989-01-01

384

Adiabatic single scan two-dimensional NMR spectrocopy.  

PubMed

New excitation schemes, based on the use adiabatic pulses, for single scan two-dimensional NMR experiments (Frydman et al., Proc. Nat. Acad. Sci. 2002, 99, 15 858-15 862) are introduced. The advantages are discussed. Applications in homo- and heteronuclear experiments are presented. PMID:14519020

Pelupessy, Philippe

2003-10-01

385

13C-NMR data of daphnane diterpenoids.  

PubMed

Daphnane diterpenoids are mainly distributed in Thymelaeaceae and Euphorbiaceae and have various bioactivities. About 100 daphnane diterpenoids have been isolated from natural plants. In this review, we systematically summarize the (13)C-NMR data of daphnane diterpenoids isolated from natural plants over the past several decades and briefly discussed their biological activities and basic structural-activity relationship. PMID:23813597

Wang, Hong-Bing; Liu, Li-Ping; Wang, Xiao-Yang

2013-09-01

386

Phase transitions in ocular tissue — NMR and temperature measurements  

Microsoft Academic Search

The human cornea, sclera and lens is studied by nuclear magnetic resonance (NMR) measurements and temperature curves. The bound water fractions of these tissues have been determined as 3% in the cornea, 20% in the sclera and 17% in the lens. In contrast to other investigations we found freezing intervals near ?1° C.

T. Seiler; N. Miiller-Stolzenburg; J. Wollensak

1983-01-01

387

Metabolic phenotyping of genetically modified mice: An NMR metabonomic approach  

Microsoft Academic Search

Monocyte chemoattractant protein-1 (MCP-1) plays a relevant role in macrophage migration but recent findings suggest an additional role in lipid and glucose metabolism. We report the use of 1H NMR spectroscopy as a useful complementary method to assess the metabolic function of this gene in a comparative strategy. This metabonomic analysis was rapid, simple, quantitative and reproducible, and revealed a

Anna Rull; Maria Vinaixa; Miguel Ángel Rodríguez; Raúl Beltrán; Jesús Brezmes; Nicolau Cañellas; Xavier Correig; Jorge Joven

2009-01-01

388

Studies of the Photodegradation of Spruce Lignin by Nmr Spectroscopy  

Microsoft Academic Search

The light-induced degradation of lignin was studied using spruce MWL impregnated on handsheets prepared from cotton linters. The sheets were irradiated with simulated sunlight and the lignin was extracted. Solutions of untreated and irradiated lignin were studied by H and C NMR spectroscopy. The results showed that ?- and ?- ether and ?-? bond cleavage were the main reactions. The

Rainer Sjöholm; Bjarne Holmbom; Nina Akerback

1992-01-01

389

A Networked NMR Spectrometer: Configuring a Shared Instrument  

ERIC Educational Resources Information Center

A model for a shared nuclear magnetic resonance spectroscopy (NMR) facility between a private university and two local community colleges is presented. The discussion of the components required for the shared facility, modes of data distribution, and overall effect on the curriculum is presented.

Alonso, David; Mutch, G. William; Wong, Peter; Warren, Steven; Barot, Bal; Kosinski, Jan; Sinton, Mark

2005-01-01

390

Study of molecular interactions with 13C DNP-NMR.  

PubMed

NMR spectroscopy is an established, versatile technique for the detection of molecular interactions, even when these interactions are weak. Signal enhancement by several orders of magnitude through dynamic nuclear polarization alleviates several practical limitations of NMR-based interaction studies. This enhanced non-equilibrium polarization contributes sensitivity for the detection of molecular interactions in a single NMR transient. We show that direct (13)C NMR ligand binding studies at natural isotopic abundance of (13)C gets feasible in this way. Resultant screens are easy to interpret and can be performed at (13)C concentrations below muM. In addition to such ligand-detected studies of molecular interaction, ligand binding can be assessed and quantified with enzymatic assays that employ hyperpolarized substrates at varying enzyme inhibitor concentrations. The physical labeling of nuclear spins by hyperpolarization thus provides the opportunity to devise fast novel in vitro experiments with low material requirement and without the need for synthetic modifications of target or ligands. PMID:20022775

Lerche, Mathilde H; Meier, Sebastian; Jensen, Pernille R; Baumann, Herbert; Petersen, Bent O; Karlsson, Magnus; Duus, Jens Ø; Ardenkjaer-Larsen, Jan H

2010-03-01

391

Amplification of xenon NMR and MRI by remote detection  

PubMed Central

A technique is proposed in which an NMR spectrum or MRI is encoded and stored as spin polarization and is then moved to a different physical location to be detected. Remote detection allows the separate optimization of the encoding and detection steps, permitting the independent choice of experimental conditions and excitation and detection methodologies. In the initial experimental demonstration of this technique, we show that taking dilute 129Xe from a porous sample placed inside a large encoding coil and concentrating it into a smaller detection coil can amplify NMR signal. In general, the study of NMR active molecules at low concentration that have low physical filling factor is facilitated by remote detection. In the second experimental demonstration, MRI information encoded in a very low-field magnet (4–7 mT) is transferred to a high-field magnet (4.2 T) to be detected under optimized conditions. Furthermore, remote detection allows the utilization of ultrasensitive optical or superconducting quantum interference device detection techniques, which broadens the horizon of NMR experimentation.

Moule, Adam J.; Spence, Megan M.; Han, Song-I; Seeley, Juliette A.; Pierce, Kimberly L.; Saxena, Sunil; Pines, Alexander

2003-01-01

392

NMR spectroscopic determination of paths of natural hydrocarbon processing  

Microsoft Academic Search

A promising technique for the analysis of structures of groups of compounds present in natural hydrocarbons is NME spectroscopy. This technique is firmly making its way into studies of oils from new fields [1-3]. The structural parameters obtained by NMR spectroscopy provide a fairly comprehensive qualitative idea of the structural organization of various fragments of molecules and the possibility of

D. F. Kushnarev; T. V. Afonina; A. A. Ageenko; L. G. Treneva

1990-01-01

393

Discovering High-Affinity Ligands for Proteins: SAR by NMR  

NSDL National Science Digital Library

A nuclear magnetic resonance (NMR)-based method is described in which small organic molecules that bind to proximal subsites of a protein are identified, optimized, and linked together to produce high-affinity ligands. The method reduces the amount of chemical synthesis and time required for the discovery of high-affinity ligands and appears particularly useful in target-directed drug research.

Suzanne B. Shuker (Abbott Laboratories;); Philip J Hajduk (Abbott Laboratories;); Robert Meadows (Abbott Laboratories;); Stephen Fesik (Abbott Laboratories;)

1996-11-29

394

NMR Studies of Diffusion in Glassy and Crystalline Lithium Borates.  

National Technical Information Service (NTIS)

The 7Li NMR spectra from several lithium borate glasses were examined as a function of temperature and found to narrow abruptly with increasing temperature in the range of temperatures from 250 to 475K. The observed narrowing is a manifestation of the phe...

S. G. Bishop P. J. Bray

1967-01-01

395

NMR of thin layers using a meanderline surface coil  

DOEpatents

A miniature meanderline sensor coil which extends the capabilities of nuclear magnetic resonance (NMR) to provide analysis of thin planar samples and surface layer geometries. The sensor coil allows standard NMR techniques to be used to examine thin planar (or curved) layers, extending NMRs utility to many problems of modern interest. This technique can be used to examine contact layers, non-destructively depth profile into films, or image multiple layers in a 3-dimensional sense. It lends itself to high resolution NMR techniques of magic angle spinning and thus can be used to examine the bonding and electronic structure in layered materials or to observe the chemistry associated with aging coatings. Coupling this sensor coil technology with an arrangement of small magnets will produce a penetrator probe for remote in-situ chemical analysis of groundwater or contaminant sediments. Alternatively, the sensor coil can be further miniaturized to provide sub-micron depth resolution within thin films or to orthoscopically examine living tissue. This thin-layer NMR technique using a stationary meanderline coil in a series-resonant circuit has been demonstrated and it has been determined that the flat meanderline geometry has about he same detection sensitivity as a solenoidal coil, but is specifically tailored to examine planar material layers, while avoiding signals from the bulk.

Cowgill, Donald F. (San Ramon, CA)

2001-01-01

396

NMR excitation and relaxation in a ``single domain'' spin glass  

Microsoft Academic Search

Zero field NMR measurements of the spin lattice relaxation time T1 on copper satellite nuclei in a frozen CuMn ``single domain'' spin glass show that the longitudinal nuclear magnetization recovery is not purely exponential. Three possible causes for the observed nonexponentiality have been considered: The distribution of enhancement factors, the differences in neighbourhood experienced by the satellite nuclei and a

E. Tönsing; H. Jung; C. Tempelmann; H. Brömer

1991-01-01

397

Modeling 21Ne NMR parameters for carbon nanosystems.  

PubMed

The potential of nuclear magnetic resonance (NMR) technique in probing the structure of porous systems including carbon nanostructures filled with inert gases is analysed theoretically using accurate calculations of neon ((21) Ne) nuclear magnetic shieldings. The CBS estimates of (21) Ne NMR parameters were performed for single atom, its dimer and neon interacting with acetylene, ethylene and 1,3-cyclopentadiene. Several levels of theory including restricted Hartree-Fock (RHF), Møller-Plesset perturbation theory to the second order (MP2), density functional theory (DFT) with van Voorhis and Scuseria's t-dependent gradient-corrected correlation functional (VSXC), coupled cluster with single and doubles excitations (CCSD), with single, doubles and triples included in a perturbative way (CCSD(T)) and single, doubles and tripes excitations (CCSDT) combined with polarization-consistent aug-pcS-n series of basis sets were employed. The impact of neon confinement inside selected fullerene cages used as an NMR probe was studied at the RHF/pcS-2 level of theory. A sensitivity of neon probe to the proximity of multiple CC bonds in C2 H2 , C2 H4 , C5 H6 and inside C28 , C30 , C32 , C34 and C60 fullerenes was predicted from (21) Ne NMR parameters' changes. Copyright © 2013 John Wiley & Sons, Ltd. PMID:23970499

Kupka, Teobald; Nieradka, Marzena; Kaminský, Jakub; Stobi?ski, Leszek

2013-10-01

398

Cation Hydration Constants by Proton NMR: A Physical Chemistry Experiment.  

ERIC Educational Resources Information Center

Studies the polarization effect on water by cations and anions. Describes an experiment to illustrate the polarization effect of sodium, lithium, calcium, and strontium ions on the water molecule in the hydration spheres of the ions. Analysis is performed by proton NMR. (MVL)

Smith, Robert L.; And Others

1988-01-01

399

MULTIVARIATE CURVE RESOLUTION OF NMR SPECTROSCOPY METABONOMIC DATA  

EPA Science Inventory

Sandia National Laboratories is working with the EPA to evaluate and develop mathematical tools for analysis of the collected NMR spectroscopy data. Initially, we have focused on the use of Multivariate Curve Resolution (MCR) also known as molecular factor analysis (MFA), a tech...

400

Polar Fourier transforms of radially sampled NMR data  

Microsoft Academic Search

Radial sampling of the NMR time domain has recently been introduced to speed up data collection significantly. Here, we show that radially sampled data can be processed directly using Fourier transforms in polar coordinates. We present a comprehensive theoretical analysis of the discrete polar Fourier transform, and derive the consequences of its application to radially sampled data using linear response

Brian E. Coggins; Pei Zhou

2006-01-01

401

ECG gated NMR-CT for cardiovascular diseases  

SciTech Connect

The authors have been applying ECG gated NMR-CT to mainly patients with myocardial infarction (MI), and hypertrophic cardiomyopathy (HCM). Thirteen patients with MI, 8 with HCM and 5 without any heart diseases were studied by ECG gated NMR imaging (spin-echo technique, TR: depends on patient heart rate, TE: 35 and 70 msec.) with 0.35 T superconducting magnet. On NMR images (MRI), the authors examined the wall thickness, wall motion and T/sub 2/ relaxation time in the area of diseased myocardium. The lesions of old MI were depicted as the area of thin wall and T/sub 2/ relaxation time of those lesions were similar to the area of non-infarcted myocardium. The lesions of recent MI (up to 3.5 months from the recent attack) were shown as the same wall thickness as the non-infarcted myocardium and the area of prolonged T/sub 2/ relaxation time compared with that of non-infarcted myocardium. MRI demonstrated diffusely thick myocardium in all patients with HCM. T/sub 2/ relaxation time of the areas of HCM was almost the same as that of normal myocardium, and it's difference among each ventricular wall in patients with HCM was not statistically significant. The authors conclude that ECG gated NMR-CT offers 3-D morphological information of the heart without any contrast material nor radioisotopes. ECG gated MRI provides the useful informations to diagnose MI, especially in the differential diagnosis between old and recent MI.

Nishikawa, J.; Ohtake, T.; Machida, K.; Iio, M.; Yoshimoto, N.; Sugimoto, T.

1985-05-01

402

Pulsed zero field NMR of solids and liquid crystals  

SciTech Connect

This work describes the development and applications to solids and liquid crystals of zero field nuclear magnetic resonance (NMR) experiments with pulsed dc magnetic fields. Zero field NMR experiments are one approach for obtaining high resolution spectra of amorphous and polycrystalline materials which normally (in high field) display broad featureless spectra. The behavior of the spin system can be coherently manipulated and probed in zero field with dc magnetic field pulses which are employed in a similar manner to radiofrequency pulses in high field NMR experiments. Nematic phases of liquid crystalline systems are studied in order to observe the effects of the removal of an applied magnetic field on sample alignment and molecular order parameters. In nematic phases with positive and negative magnetic susceptibility anisotropies, a comparison between the forms of the spin interactions in high and low fields is made. High resolution zero field NMR spectra of unaligned smectic samples are also obtained and reflect the symmetry of the liquid crystalline environment. These experiments are a sensitive measure of the motionally induced asymmetry in biaxial phases. Homonuclear and heteronuclear solute spin systems are compared in the nematic and smectic phases. Nonaxially symmetric dipolar couplings are reported for several systems. The effects of residual fields in the presence of a non-zero asymmetry parameter are discussed theoretically and presented experimentally. Computer programs for simulations of these and other experimental results are also reported. 179 refs., 75 figs.

Thayer, A.M.

1987-02-01

403

Structural NMR of Protein Oligomers using Hybrid Methods  

PubMed Central

Solving structures of native oligomeric protein complexes using traditional high resolution NMR techniques remains challenging. However, increased utilization of computational platforms, and integration of information from less traditional NMR techniques with data from other complementary biophysical methods, promises to extend the boundary of NMR-applicable targets. This article reviews several of the techniques capable of providing less traditional and complementary structural information. In particular, the use of orientational constraints coming from residual dipolar couplings and residual chemical shift anisotropy offsets are shown to simplify the construction of models for oligomeric complexes, especially in cases of weak homo-dimers. Combining this orientational information with interaction site information supplied by computation, chemical shift perturbation, paramagnetic surface perturbation, cross-saturation and mass spectrometry allows high resolution models of the complexes to be constructed with relative ease. Non-NMR techniques, such as mass spectrometry, EPR and small angle X-ray scattering, are also expected to play increasingly important roles by offering alternative methods of probing the overall shape of the complex. Computational platforms capable of integrating information from multiple sources in the modeling process are also discussed in the article. And finally a new, detailed example on the determination of a chemokine tetramer structure will be used to illustrate how a non-traditional approach to oligomeric structure determination works in practice.

Wang, Xu; Lee, Hsiau-Wei; Liu, Yizhou; Prestegard, James H.

2010-01-01

404

Novel Dodecaarylporphyrins: Synthesis and Variable Temperature NMR Studies  

SciTech Connect

An investigation of the synthesis of novel dodecaarylporphyrins using the Suzuki coupling reaction of arylboronic acids with octabromotetraarylporphyrins is reported. Studies of the dynamic properties of these new porphyrins using variable temperature (VT) 1H NMR spectroscopy and molecular mechanics provide interesting insights into their dynamic properties, including the first determination of {beta} aryl rotation in a porphyrin system.

Cancilla, Mark; Lebrilla, Carlito; Ma, Jian-Guo; Medforth, Craig J.; Muzzi, Cinzia M.; Shelnutt, John A.; Smith, Kevin M.; Voss, Lisa

1999-05-05

405

20 Application of LC-NMR in pharmaceutical analysis  

Microsoft Academic Search

Hyphenated analytical techniques such as LC-MS, which combines liquid chromatography and mass spectrometry, are well-developed laboratory tools now widely used in the pharmaceutical industry. However, in most cases MS alone is insufficient for complete structural elucidation of unknown compounds. Traditionally nuclear magnetic resonance (NMR) experiments are performed on more or less pure samples, in which the signals of a single

Mieng-Hua Wann

2005-01-01

406

Quantitative evaluation of porous media wettability using NMR relaxometry.  

PubMed

We propose a new method to determine wettability indices from NMR relaxometry. The new method uses the sensitivity of low field NMR relaxometry to the fluid distribution in oil-water saturated porous media. The model is based on the existence of a surface relaxivity for both oil and water, allowing the determination of the amount of surface wetted either by oil or by water. The proposed NMR wettability index requires the measurement of relaxation time distribution at four different saturation states. At the irreducible water saturation, we determine the dominant relaxation time of oil in the presence of a small amount of water, and at the oil residual saturation, we determine the dominant relaxation time of water in the presence of a small amount of oil. At 100% water and 100% oil saturation, we determine the surface relaxivity ratio. The interaction of oil with the surface is also evidenced by the comparison of the spin-lattice (T1) and spin-locking (T1rho) relaxation times. The new NMR index agrees with standard wettability measurements based on drainage-imbibition capillary pressure curves (USBM test) in the range [-0.3-1]. PMID:12850740

Fleury, M; Deflandre, F

2003-01-01

407

An NMR Protonation Study of Metal Diethylenetriaminepentaacetic Acid Complexes.  

ERIC Educational Resources Information Center

This experiment is suitable for an integrated laboratory course for senior chemistry majors. It introduces the student to a study of the relative basicity of different proton accepting sites. It serves as an opportunity to learn about nmr techniques and could extend to infrared, as well. (BB)

Letkeman, Peter

1979-01-01

408

Numerical simulation of NQR/NMR: Applications in quantum computing.  

PubMed

A numerical simulation program able to simulate nuclear quadrupole resonance (NQR) as well as nuclear magnetic resonance (NMR) experiments is presented, written using the Mathematica package, aiming especially applications in quantum computing. The program makes use of the interaction picture to compute the effect of the relevant nuclear spin interactions, without any assumption about the relative size of each interaction. This makes the program flexible and versatile, being useful in a wide range of experimental situations, going from NQR (at zero or under small applied magnetic field) to high-field NMR experiments. Some conditions specifically required for quantum computing applications are implemented in the program, such as the possibility of use of elliptically polarized radiofrequency and the inclusion of first- and second-order terms in the average Hamiltonian expansion. A number of examples dealing with simple NQR and quadrupole-perturbed NMR experiments are presented, along with the proposal of experiments to create quantum pseudopure states and logic gates using NQR. The program and the various application examples are freely available through the link http://www.profanderson.net/files/nmr_nqr.php. PMID:21324720

Possa, Denimar; Gaudio, Anderson C; Freitas, Jair C C

2011-04-01

409

Ensemble Quantum Computing by Liquid-State NMR Spectroscopy.  

National Technical Information Service (NTIS)

We propose to use NMR as a testbed to develop general methods for solving computational problems on EQC's, to study the fundamental physics and computer science of these machines, and to learn how to make optimal use of the trade-offs that their unique ca...

T. F. Havel D. G. Cory

2003-01-01

410

An alternative tuning approach to enhance NMR signals  

Microsoft Academic Search

By using spin-noise type measurement we show that the resonance frequency of the reception circuit of classical NMR spectrometers does not match the Larmor frequency even if, in emission, the electronic circuit is perfectly tuned at the Larmor frequency and matches the amplifier impedance. We also show that this spin-noise method can be used to ensure a match between the

Denis J.-Y. Marion; Hervé Desvaux

2008-01-01

411

Noise figure characterization of preamplifiers at NMR frequencies  

NASA Astrophysics Data System (ADS)

A method for characterizing the noise figure of preamplifiers at NMR frequencies is presented. The noise figure of preamplifiers as used for NMR and MRI detection varies with source impedance and with the operating frequency. Therefore, to characterize a preamplifier's noise behavior, it is necessary to perform noise measurements at the targeted frequency while varying the source impedance with high accuracy. At high radiofrequencies, such impedance variation is typically achieved with transmission-line tuners, which however are not available for the relatively low range of typical NMR frequencies. To solve this issue, this work describes an alternative approach that relies on lumped-element circuits for impedance manipulation. It is shown that, using a fixed-impedance noise source and suitable ENR correction, this approach permits noise figure characterization for NMR and MRI purposes. The method is demonstrated for two preamplifiers, a generic BF998 MOSFET module and an MRI-dedicated, integrated preamplifier, which were both studied at 128 MHz, i.e., at the Larmor frequency of protons at 3 Tesla. Variations in noise figure of 0.01 dB or less over repeated measurements reflect high precision even for small noise figures in the order of 0.4 dB. For validation, large sets of measured noise figure values are shown to be consistent with the general noise-parameter model of linear two-ports. Finally, the measured noise characteristics of the superior preamplifier are illustrated by SNR measurements in MRI data.

Nordmeyer-Massner, J. A.; De Zanche, N.; Pruessmann, K. P.

2011-05-01

412

Amplification of xenon NMR and MRI by remote detection  

NASA Astrophysics Data System (ADS)

A technique is proposed in which an NMR spectrum or MRI is encoded and stored as spin polarization and is then moved to a different physical location to be detected. Remote detection allows the separate optimization of the encoding and detection steps, permitting the independent choice of experimental conditions and excitation and detection methodologies. In the initial experimental demonstration of this technique, we show that taking dilute 129Xe from a porous sample placed inside a large encoding coil and concentrating it into a smaller detection coil can amplify NMR signal. In general, the study of NMR active molecules at low concentration that have low physical filling factor is facilitated by remote detection. In the second experimental demonstration, MRI information encoded in a very low-field magnet (4-7 mT) is transferred to a high-field magnet (4.2 T) to be detected under optimized conditions. Furthermore, remote detection allows the utilization of ultrasensitive optical or superconducting quantum interference device detection techniques, which broadens the horizon of NMR experimentation.

Moulé, Adam J.; Spence, Megan M.; Han, Song-I.; Seeley, Juliette A.; Pierce, Kimberly L.; Saxena, Sunil; Pines, Alexander

2003-08-01

413

Nondestructive NMR technique for moisture determination in radioactive materials.  

SciTech Connect

This progress report focuses on experimental and computational studies used to evaluate nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) for detecting, quantifying, and monitoring hydrogen and other magnetically active nuclei ({sup 3}H, {sup 3}He, {sup 239}Pu, {sup 241}Pu) in Spent nuclear fuels and packaging materials. The detection of moisture by using a toroid cavity NMR imager has been demonstrated in SiO{sub 2} and UO{sub 2} systems. The total moisture was quantified by means of {sup 1}H NMR detection of H{sub 2}O with a sensitivity of 100 ppm. In addition, an MRI technique that was used to determine the moisture distribution also enabled investigators to discriminate between bulk and stationary water sorbed on the particles. This imaging feature is unavailable in any other nondestructive assay (NDA) technique. Following the initial success of this program, the NMR detector volume was scaled up from the original design by a factor of 2000. The capacity of this detector exceeds the size specified by DOE-STD-3013-96.

Aumeier, S.; Gerald, R.E. II; Growney, E.; Nunez, L.; Kaminski, M.

1998-12-04

414

Simultaneous Nonlinear Least Squares Fitting Technique For NMR Spectroscopy  

Microsoft Academic Search

A new iterative nonlinear least squares fitting technique is developed to fit the NMR free induction decay (FlD) signals in the time domain. The new technique makes it possible fitting all the parameters, e.g., frequencies, decay factors, amplitudes and phases, simultaneously. The corresponding initial values are obtained by linear prediction singular value decomposition (LPSVD)[ 11, which is a completely automatic

Wen Ge; H. K. Lee; O. Nalcioglu

1993-01-01

415

Contaminations of herbal products determined by NMR fingerprint  

Microsoft Academic Search

The utilisation of NMR fingerprinting is proposed as a rapid, available and reliable method to determine the contamination of herbal products. The presence of nimesulide has been reported recently as the contaminant of P.C. 28 Plus, a product based on herbal drugs marketed by the Italian company Cosval. The presence of the substance, as well as its relevant concentration (5%),

Marcello Nicoletti; Valentina Petitto

2010-01-01

416

The inherent accuracy of 1H NMR spectroscopy to quantify plasma lipoproteins is subclass dependent  

Microsoft Academic Search

Proton NMR spectroscopy as a means to quantify lipoprotein subclasses has received wide clinical interest. The experimental part is a fast routine procedure that contrasts favourably to other lipoprotein measurement protocols. The difficulties in using 1H NMR, however, are in uncovering the subclass specific information from the overlapping data. The NMR-based quantification has been evaluated only in relation to biochemical

Mika Ala-Korpela; Niko Lankinen; Aino Salminen; Teemu Suna; Pasi Soininen; Reino Laatikainen; Petri Ingman; Matti Jauhiainen; Marja-Riitta Taskinen; Károly Héberger; Kimmo Kaski

2007-01-01

417

13C NMR as a general tool for the assignment of absolute configuration.  

PubMed

(13)C NMR, alone or in combination with (1)H NMR, allows the assignment of the absolute configuration of chiral alcohols, amines, carboxylic acids, thiols, cyanohydrins, sec,sec-diols and sec,sec-aminoalcohols, derivatized with appropriate chiral auxiliaries. This extends the assignment possibilities of NMR to fully deuterated and to nonproton containing compounds. PMID:20886140

Louzao, Iria; Seco, José Manuel; Quiñoá, Emilio; Riguera, Ricardo

2010-11-14

418

1 H-NMR on Super-Ionic Conductor TI 3 H(SO 4 ) 2  

Microsoft Academic Search

We have studied the proton dynamics on Tl 3 H(SO 4 ) 2 from the measurements of 1 H-NMR absorption lines. It was found that the NMR line width j H at room temperature becomes about 20 times narrower than that at 77 K and that the NMR absorption line at room temperature shows the mixture functional form of the

Yasumitsu Matsuo; Keisuke Takahashi; Seiichiro Ikehata

2002-01-01

419

SQUID-detected NMR and MRI in microtesla magnetic fields  

NASA Astrophysics Data System (ADS)

A low transition temperature do Superconducting QUantum Interference Device (low-Tc do SQUID) was used to perform liquid-state nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) experiments in magnetic fields from microtesla to tens of microtesla, corresponding to proton Larmor frequencies from tens of Hz to kHz. The spins were polarized in a magnetic field of the order of millitesla. Upon turnoff of the polarizing field, precession was induced in the much weaker measurement field. Because the SQUID magnetometer was operated with an untuned, superconducting, input circuit, the integrated intensity of the NMR lines was independent of the strength of the measurement field. On the other hand, the NMR linewidth scaled linearly with the measurement field strength. Narrowing of the NMR signal bandwidth through reduction of the strength of the measurement field led to an enhancement of both spectral resolution and signal-to-noise ratio (SNR). A novel cryogenic insert was constructed to allow SQUID measurement of NMR signals from room temperature samples with high filling factor. From samples with volume of a few milliliters and thermal polarization of order 10 -8, SNR of a few tens were achieved in a single shot. Heteronuclear scalar couplings were resolved in 1H-31P and 1H-13C systems. Furthermore, the frequency-independent sensitivity of the untuned SQUID magnetometer allowed simultaneous detection of NMR signals from nuclei with different magnetogyric ratios. A system based on a low-Tc SQUID gradiometer was used to acquire MRIs from distilled water and mineral oil phantoms in microtesla fields. The bandwidth-narrowing technique was exploited to enhance spatial resolution for a fixed strength of the encoding gradients. With magnetic field gradients of the order of tens of microtesla per meter, images with spatial resolution of a millimeter were achieved. The techniques described in this thesis could readily be adapted for use with multichannel SQUID systems designed for biomagnetic measurements at low frequency, and represent a first step toward the development of low cost, portable NMR and MRI scanners based on untuned SQUID magnetometers.

McDermott, Robert Francis

420

Two Phase Flow Measurements by Nuclear Magnetic Resonance (NMR)  

SciTech Connect

In concentrated suspensions, there is a tendency for the solid phase to migrate from regions of high shear rate to regions of low shear (Leighton & Acrivos, 1987). In the early years that our effort was funded by the DOE Division of Basic Energy Science, quantitative measurement of this process in neutrally buoyant suspensions was a major focus (Abbott, et al., 1991; Altobelli, et al., 1991). Much of this work was used to improve multi-phase numerical models at Sandia National Laboratories. Later, our collaborators at Sandia and the University of New Mexico incorporated body forces into their numerical models of suspension flow (Rao, Mondy, Sun, et al., 2002). We developed experiments that allow us to study flows driven by buoyancy, to characterize these flows in well-known and useful engineering terms (Altobelli and Mondy, 2002) and to begin to explore the less well-understood area of flows with multiple solid phases (Beyea, Altobelli, et al., 2003). We also studied flows that combine the effects of shear and buoyancy, and flows of suspensions made from non-Newtonian liquids (Rao, Mondy, Baer, et al, 2002). We were able to demonstrate the usefulness of proton NMR imaging of liquid phase concentration and velocity and produced quantitative data not obtainable by other methods. Fluids flowing through porous solids are important in geophysics and in chemical processing. NMR techniques have been widely used to study liquid flow in porous media. We pioneered the extension of these studies to gas flows (Koptyug, et al, 2000, 2000, 2001, 2002). This extension allows us to investigate a wider range of Peclet numbers, and to gather data on problems of interest in catalysis. We devised two kinds of NMR experiments for three-phase systems. Both experiments employ two NMR visible phases and one phase that gives no NMR signal. The earlier method depends on the two visible phases differing in a NMR relaxation property. The second method (Beyea, Altobelli, et al., 2003) uses two different nuclei, protons and 19F. It also uses two different types of NMR image formation, a conventional spin-echo and a single-point method. The single-point method is notable for being useful for imaging materials which are much more rigid than can usually be studied by NMR imaging. We use it to image “low density” polyethylene (LDPE) plastic in this application. We have reduced the imaging time for this three-phase imaging method to less than 10 s per pair of profiles by using new hardware. Directly measuring the solid LDPE signal was a novel feature for multi-phase flow studies. We also used thermally polarized gas NMR (as opposed to hyper-polarized gas) which produces low signal to noise ratios because gas densities are on the order of 1000 times smaller than liquid densities. However since we used multi-atom molecules that have short T1's and operated at elevated pressures we could overcome some of the losses. Thermally polarized gases have advantages over hyperpolarized gases in the ease of preparation, and in maintaining a well-defined polarization. In these studies (Codd and Altobelli, 2003), we used stimulated echo sequences to successfully obtain propagators of gas in bead packs out to observation times of 300 ms. Zarraga, et al. (2000) used laser-sheet profilometry to investigate normal stress differences in concentrated suspensions. Recently we developed an NMR imaging analog for comparison with numerical work that is being performed by Rekha Rao at Sandia National Laboratories (Rao, Mondy, Sun, et al, 2002). A neutrally buoyant suspension of 100 mm PMMA spheres in a Newtonian liquid was sheared in a vertical Couette apparatus inside the magnet. The outer cylinder rotates and the inner cylinder is fixed. At these low rotation rates, the free-surface of the Newtonian liquid shows no measurable deformation, but the suspension clearly shows its non-Newtonian character.

Altobelli, Stephen A; Fukushima, Eiichi

2006-08-14

421

19F-NMR Studies of ?-Synuclein Conformation and Fibrillation†  

PubMed Central

Fibrils of the intrinsically-disordered protein ?-synuclein are hallmarks of Parkinson's disease. The fluorescent dye thioflavin T is often used to characterize fibrillation, but this assay may not provide quantitative information about structure and mechanism. To gain such information, we incorporated the 19F-labeled amino acid, 3-fluorotyrosine, into recombinant human ?-synuclein at its endogenous tyrosine residues. Tyrosine 39 is in the positively-charged N-terminal region of this 140-residue protein. The other three, tyrosines, 125, 133, and 136, are near the C-terminus. 19F-nuclear magnetic resonance spectroscopy was used to study several properties of labeled ?-synuclein, including its conformation; conformational changes induced by urea, spermine, and sodium dodecyl sulfate (SDS); its interaction with SDS micelles; and the kinetics of fibril formation. The results show that the tyrosines are in disordered regions but that there is some structure near position 39 that is disrupted by urea. SDS binding alters the conformation near position 39, but the C-terminal tyrosines are disordered under all conditions. The NMR data also indicate that SDS-micelle bound ?-synuclein and the free protein exchange on the 10-ms time scale. Studies of fibrillation show the utility of 19F-labeled NMR. The data indicate that fibrillation is not accompanied by the formation of large quantities of low molecular-weight intermediates. Although dye-binding and 19F NMR data show that 1-mM SDS and 1-mM spermine accelerate aggregation compared to buffer alone, only the NMR data indicate that the species formed in SDS are smaller than those formed in buffer or buffer plus spermine. We conclude that 19F NMR spectroscopy is useful for obtaining residue-level, quantitative information about the structure, binding, and aggregation of ?-synuclein.

Li, Conggang; Lutz, Evan A.; Slade, Kristin M.; Ruf, Rebecca A.S.; Wang, Gui-Fang; Pielak, Gary J.

2009-01-01

422

Toxic actions of dinoseb in medaka ( Oryzias latipes) embryos as determined by in vivo 31P NMR, HPLC-UV and 1H NMR metabolomics  

Microsoft Academic Search

Changes in metabolism of Japanese medaka (Oryzias latipes) embryos exposed to dinoseb (2-sec-butyl-4,6-dinitrophenol), a substituted dinitrophenol herbicide, were determined by in vivo 31P NMR, high-pressure liquid chromatography (HPLC)-UV, and 1H NMR metabolomics. ATP and phosphocreatine (PCr) metabolism were characterized within intact embryos by in vivo 31P NMR; concentrations of ATP, GTP, ADP, GDP, AMP and PCr were determined by HPLC-UV;

Mark R. Viant; Christopher A. Pincetich; David E. Hinton; Ronald S. Tjeerdema

2006-01-01

423

Development of an NMR interface microchip "MICCS" for direct detection of reaction products and intermediates of micro-syntheses using a "MICCS-NMR".  

PubMed

The development of an NMR interface microchip and its applications to the real-time monitoring of chemical reactions are described. The microchip device was named "MICCS" (MIcro Channeled Cell for Synthesis monitoring), and the method using it was named "MICCS-NMR". MICCS was inserted into a 5 mm Phi NMR sample tube. Thus standard solution NMR probes without any modifications can be used in MICCS-NMR measurements. A gap between MICCS and the sample tube was filled with a deuterated solvent for an NMR lock. The reaction temperature and reaction time in MICCS can be easily changed by adjusting the temperature of the NMR probe and changing the flow rates, respectively. The effectiveness of the MICCS-NMR was verified in the real-time monitoring of the Wittig reaction. Preliminary data on the direct detection of intermediates of the Grignard reaction is also reported. Besides real-time monitoring of chemical reactions, MICCS-NMR would be useful as a qualitative detection method for microchip-based synthesis. PMID:17420541

Takahashi, Yutaka; Nakakoshi, Masamichi; Sakurai, Satoshi; Akiyama, Yoshitake; Suematsu, Hiroto; Utsumi, Hiroaki; Kitamori, Takehiko

2007-04-01

424

Natural abundance 17O NMR study of 2- and 4-substituted benzoyl chlorides  

NASA Astrophysics Data System (ADS)

Natural abundance 17O NMR chemical shift data for 17 ortho and para benzoyl chlorides recorded in acetonitrile at 75°C are reported. 17O NMR data for the para substituted benzoyl chlorides are correlated with 17O NMR data for similarly substituted acetophenones and methyl benzoates. The 17O NMR signals for ortho isomers are downfield ( ca 30 ppm) from their para isomers; the downfield shifts are consistent with torsion angle change. The 17O NMR data for the para isomers gave good correlations with ? + constants and with dual substituent parameters (DSP).

Boykin, David W.

425

17O NMR spectroscopy of substituted methyleneindanones: relationship between chemical shift and oxygen atom electron density  

NASA Astrophysics Data System (ADS)

17O NMR spectroscopic data for eigth ?-substituted methyleneindanones obtained at natural abundance in acetonitrile at 75°C are reported. 17O NMR data for ten para-substituted E-benzalindanones, enriched with 17O, were recorded in acetonitrile at 75°C. The 17O NMR data for the E-benzalindanones gave good correlations with sigma plus values, with literature carbonyl IR stretching frequencies, and with literature 17O NMR carbonyl data of chalcones and 5-aryl-2,3-furandiones. The carbonyl oxygen atom electron density (AM1) gave good correlation with the carbonyl 17O NMR chemical shift of both ?-substituted methyleneindanones and the E-benzalindanones.

Kumar, Arvind; Boykin, David W.

1993-07-01

426

Conformational Analysis of (+)-Germacrene A by Variable Temperature NMR and NOE Spectroscopy  

PubMed Central

(+)-Germacrene A, an important intermediate in sesquiterpene biosynthesis, was isolated in pure form from a genetically engineered yeast and was characterized by chromatographic properties (TLC, GC), MS, optical rotation, UV, IR, 1H NMR and 13C NMR data. Variable-temperature 500 MHz 1H NMR spectra in CDCl3 showed that this flexible cyclodecadiene ring exists as three NMR-distinguishable conformational isomers in a ratio of about 5:3:2 at or below ordinary probe temperature (25° C). The conformer structures were assigned by 1H NMR data comparisons, NOE experiments, and vicinal couplings as follows: 1a (52%, UU), 1b (29% UD), and 1c (19%, DU).

Faraldos, Juan A.; Wu, Shuiqin; Chappell, Joe

2009-01-01

427

Microscale simulations of NMR relaxation in porous media  

NASA Astrophysics Data System (ADS)

In petrophysical applications of nuclear magnetic resonance (NMR), the measured relaxation signals originate from the fluid filled pore space. Hence, in rocks or sediments the water content directly corresponds to the initial amplitude of the recorded NMR relaxation signals. The relaxation rate (longitudinal/transversal decay time T1, T2) is sensitive to pore sizes and physiochemical properties of rock-fluid interfaces (surface relaxivity), as well as the concentration of paramagnetic ions in the fluid phases (bulk relaxivity). In the subproject A2 of the TR32 we aim at improving the basic understanding of these processes at the pore scale and thereby advancing the interpretation of NMR data by reducing the application of restrictive approximated interpretation schemes, e.g. for deriving pore size distributions, connectivity or permeability. In this respect we numerically simulate NMR relaxation data at the micro sale to study the impact of physical and hydrological parameters such as internal field gradients or pore connectivities on NMR signals. Joint numerical simulations of the NMR relaxation behavior (Bloch equations) in the presence of internal gradients (Ampere's law) and fluid flow (Navier-Stokes) on a pore scale dimension have been implemented in a finite element (FE) model using Comsol Multiphysics. Processes governing the time and spatial behavior of the nuclear magnetization density in a porous medium are diffusion and surface interactions at the rock-fluid interface. Based on Fick's law of diffusive motion Brownstein and Tarr (1979) introduced differential equations that describe the relaxation behavior of the Spin magnetization in single isolated pores and derived analytical solutions for simple geometries, i.e. spherical, cylindrical and planar. However, by numerically solving these equations in a general way using a FE algorithm this approach can be applied to study and simulate coupled complex pore systems, e.g. derived from computer tomography (CT). In this respect substantial coupling effects in typical porous rocks can be observed at pore sizes about <1 ?m, e.g. encountered in tight gas reservoir formations. Internal magnetic field gradients in rocks arise due to susceptibility contrasts in pore fluid and rock matrix and depend on the magnetic field strength (Larmor frequency). To model the increased relaxation rate observed in CPMG measurements due to diffusive motion in a magnetic (internal) gradient field the simulations are coupled with calculations of spatial distribution of field gradients within the simulated fluid-matrix system according to Ampere's law. Contrary to common assumptions of a constant ratio between T1 and T2 in petrophysical NMR the CPMG simulations in the presence of internal gradients show a significant increase of T1/T2 ratios with decreasing pore sizes. This implies a shift of derived signal contributions to smaller pore sizes, e.g. <1 ?m, from T2 NMR experiments, and thus an underestimation of derived permeabilities. ?m These simulations will also be compiled for multi-phase systems, e.g. water-air-oil, to study basic correlations between NMR and hydrological parameters of partially saturated rocks. This study was conducted within the framework of the Transregional Collaborative Research Centre 32, funded by the German Research Foundation (DFG).

Mohnke, Oliver; Klitzsch, Norbert

2010-05-01

428

Microscale simulations of NMR relaxation in porous media  

NASA Astrophysics Data System (ADS)

In petrophysical applications of nuclear magnetic resonance (NMR), the measured relaxation signals originate from the fluid filled pore space. Hence, in rocks or sediments the water content directly corresponds to the initial amplitude of the recorded NMR relaxation signals. The relaxation rate (longitudinal/transversal decay time T1, T2) is sensitive to pore sizes and physiochemical properties of rock-fluid interfaces (surface relaxivity), as well as the concentration of paramagnetic ions in the fluid phases (bulk relaxivity). We aim at improving the basic understanding of these processes at the pore scale and thereby advancing the interpretation of NMR data by reducing the application of restrictive approximated interpretation schemes, e.g. for deriving pore size distributions, connectivity or permeability. In this respect we numerically simulate NMR relaxation data at the micro sale to study the impact of physical and hydrological parameters such as internal field gradients or pore connectivities on NMR signals. Joint numerical simulations of the NMR relaxation behavior (Bloch equations) in the presence of internal gradients (Ampere’s law) and fluid flow (Navier-Stokes) on a pore scale dimension have been implemented in a finite element (FE) model using Comsol Multiphysics. Processes governing the time and spatial behavior of the nuclear magnetization density in a porous medium are diffusion and surface interactions at the rock-fluid interface. Based on Fick's law of diffusive motion Brownstein and Tarr (1979) introduced differential equations that describe the relaxation behavior of the Spin magnetization in single isolated pores and derived analytical solutions for simple geometries, i.e. spherical, cylindrical and planar. However, by numerically solving these equations in a general way using a FE algorithm this approach can be applied to study and simulate coupled complex pore systems, e.g. derived from computer tomography (CT). In this respect substantial coupling effects in typical porous rocks can be observed at pore sizes about <1 ?m, e.g. encountered in tight gas reservoir formations. Internal magnetic field gradients in rocks arise due to susceptibility contrasts in pore fluid and rock matrix and depend on the magnetic field strength (Larmor frequency). To model the increased relaxation rate observed in CPMG measurements due to diffusive motion in a magnetic (internal) gradient field the simulations are coupled with calculations of spatial distribution of field gradients within the simulated fluid-matrix system according to Ampere's law. Contrary to common assumptions of a constant ratio between T1 and T2 in petrophysical NMR the CPMG simulations in the presence of internal gradients show a significant increase of T1/T2 ratios with decreasing pore sizes. This implies a shift of derived signal contributions to smaller pore sizes, e.g. <1 ?m, from T2 NMR experiments, and thus an underestimation of derived permeabilities. ?m These simulations will also be compiled for multi-phase systems, e.g. water-air-oil, to study basic correlations between NMR and hydrological parameters of partially saturated rocks. This study was conducted within the framework of the Transregional Collaborative Research Centre 32, funded by the German Research Foundation (DFG).

Mohnke, O.; Klitzsch, N.; Clauser, C.

2009-12-01

429

NMR studies of osmoregulation in methanogenic archaebacteria. [NMR (nuclear magnetic resonance)  

SciTech Connect

Methanogens are strict anaerobic archaebacteria whose metabolism centers around the reduction of CO[sub 2] to CH[sub 4]. Their environments are often extreme (high temperatures, high salt, few nutrients, etc.) and they may have evolved unique ways to handle these stresses. It is proposed that methanogenic archaebacteria respond to osmotic stress by accumulating a series of organic solutes. In two strains of marine methanogens, Methanogenium cariaci and Methanococcus thermolithotrophicus, four key organic solutes are observed: L-[alpha]-glutamate, [beta]-glutamate, N[sup e]-acetyl-[beta]-lysine, and glycine betaine. The first three of these are synthesized de novo; glycine betaine is transported into the Mg. cariaci cells from the medium. In the absence of betaine, Mg. cariaci synthesizes N[sup e]-acetyl-[beta]-lysine as the dominant osmolyte. Mc. thermolithotrophicus also synthesizes N[sup e]-acetyl-[beta]-lysine but only at salt concentrations greater than 1 M. In Mc. thermolithotrophicus intracellular potassium ion concentrations, determined by [sup 39]K NMR spectroscopy, are balanced by the total concentration of anionic amino acid species, [alpha]-glutamate and [beta]-glutamate. Turnover of the organic solutes has been monitored using [sup 13]C-pulse/[sup 12]C-chase, and [sup 15]N-pulse/[sup 14]N-chase experiments. The [beta]-amino acids exhibit slower turnover rates compared to L-[alpha]-glutamate or aspartate, consistent with their role as compatible solutes. Biosynthetic information for the [beta]-amino acids was provided by [sup 13]C-label incorporation and steady state labeling experiments. [beta]-glutamate shows a lag in [sup 13]C uptake from [sup 13]CO[sub 2], indicative of its biosynthesis from a precursor not in equilibrium with the soluble L-[alpha]-glutamate pool, probably a macromolecule. A novel biosynthetic pathway is proposed for N[sup e]-acetyl-[beta]-lysine from the diaminopimelate pathway.

Robertson, D.E.

1991-01-01

430

Borotungstate polyoxometalates: multinuclear NMR structural characterization and conversions in solutions.  

PubMed

The unique heteropolyanion [H(3)BW(13)O(46)](8-) (BW(13)), previously suggested on the basis of indirect evidence, and protonated lacunary heteropolyanion [HBW(11)O(39)](8-) (BW(11)) have been identified in aqueous solutions at pH 5-7.5 from NMR spectra. The pattern of tungsten-tungsten connectivities based on the analysis of the (2)J(W-O-W) coupling satellites in the (183)W NMR spectrum of BW(11), containing six peaks of relative intensities ?2:2:2:1:2:2, indicates that the latter is the ? isomer. The (17)O NMR spectrum confirms the protonated state of the polyanion with the proton delocalized on two out of four terminal O atoms surrounding the tungsten vacancy. The (183)W NMR spectrum of BW(13) contains seven peaks of relative intensities ?2:1:2:2:2:2:2 with additional large couplings due to the connectivity between BW(11) and [W(2)O(7)](2-) fragments. According to the (17)O NMR spectrum, two protons of [BW(13)O(46)H(3)](8-) are delocalized on the two terminal trans O atoms of the dimeric fragment while the third one is linked to its bridging O atom. The conversions of BW(11) and BW(13) in solution were followed by using (183)W NMR spectra at a "fingerprint" level. In the pH range from ?7.5 to 6, BW(11) transforms to BW(13), transforming further to [BW(12)O(40)](5-) (BW(12)) and [B(3)W(39)O(132)H(n)](n-21) (B(3)W(39)) in different ratios. Conversion of BW(13) to BW(12) proceeds through an intermediate complex of suggested composition [BW(11)O(39)·WO(2)](7-). At high acidity (pH ? 0), B(3)W(39) gradually decomposes into tungstic acid, BW(12) and H(3)BO(3). Polyanion BW(12) persists in the pH range ?0-7.5. PMID:21526755

Maksimovskaya, Raisa I; Maksimov, Gennadii M

2011-06-01

431

In vivo effects of photosynthesis inhibitors in Synechococcus as determined by /sup 31/P NMR spectroscopy  

SciTech Connect

Phosphorus-31 nuclear magnetic resonance spectra were obtained from darkened cells of the unicellular cyanobacterium Synechococcus sp. Resonance peaks were assigned to intracellular pools of sugar-phosphates, inorganic phosphate (P/sub i/), nucleotides, and polyphosphate. An internal pH of 7.2 was estimated from the chemical shift of the P/sub i/ resonance. Cells were then illuminated at 1600 ..mu..E m/sup -2/ s/sup -1/ photosynthetically active radiation by a fiber optic cable immersed in the cell sample. Spectra obtained after approximately 15 min of illumination showed an increase in nucleotide pools and an increase in the cytoplasmic pH to 7.6. In the presence of 0.3 mM dinitrophenol (DNP), an uncoupler of phosphorylation, spectra of illuminated cells showed an immediate decline in nucleotide pools while sugar-phosphate levels remained constant. Addition of the photosystem II (PS II) electron-transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) (7.2 ..mu..M) did not affect nucleotide levels in the cells during the time course of the experiment (15-30 min). However, an abrupt rise in the resonance in the sugar-phosphate region was noted. Spectra of DCMU-treated cells extracts indicated that one metabolite was principally responsible for the change in pool size. The metabolite was identified as 3-phosphoglyceric acid. Spectra of illuminated cells were also obtained in the presence of the natural herbicide cyanobacterin. Unlike results obtained with DNP or DCMU, spectra of cyanobacterin-treated cells showed no major changes in nucleotide or sugar-phosphate resonances. A slow decline in cytoplasmic pH was seen in the presence of cyanobacterin, indicating that the natural product affects the proton pumping mechanism in PS II.

Thoma, W.J.; Gleason, F.K.

1987-05-05

432

Development of a micro flow-through cell for high field NMR spectroscopy.  

SciTech Connect

A highly transportable micro flow-through detection cell for nuclear magnetic resonance (NMR) spectroscopy has been designed, fabricated and tested. This flow-through cell allows for the direct coupling between liquid chromatography (LC) and gel permeation chromatography (GPC) resulting in the possibility of hyphenated LC-NMR and GPC-NMR. The advantage of the present flow cell design is that it is independent and unconnected to the detection probe electronics, is compatible with existing commercial high resolution NMR probes, and as such can be easily implemented at any NMR facility. Two different volumes were fabricated corresponding to between {approx}3.8 and 10 {micro}L detection volume. Examples of the performance of the cell on different NMR instruments, and using different NMR detection probes were demonstrated.

Alam, Todd Michael; McIntyre, Sarah K.

2011-05-01

433

Bioagent detection using miniaturized NMR and nanoparticle amplification : final LDRD report.  

SciTech Connect

This LDRD program was directed towards the development of a portable micro-nuclear magnetic resonance ({micro}-NMR) spectrometer for the detection of bioagents via induced amplification of solvent relaxation based on superparamagnetic nanoparticles. The first component of this research was the fabrication and testing of two different micro-coil ({micro}-coil) platforms: namely a planar spiral NMR {micro}-coil and a cylindrical solenoid NMR {micro}-coil. These fabrication techniques are described along with the testing of the NMR performance for the individual coils. The NMR relaxivity for a series of water soluble FeMn oxide nanoparticles was also determined to explore the influence of the nanoparticle size on the observed NMR relaxation properties. In addition, The use of commercially produced superparamagnetic iron oxide nanoparticles (SPIONs) for amplification via NMR based relaxation mechanisms was also demonstrated, with the lower detection limit in number of SPIONs per nanoliter (nL) being determined.

Clewett, C. F. M.; Adams, David Price; Fan, Hongyou; Williams, John D.; Sillerud, Laurel O.; Alam, Todd Michael; Aldophi, Natalie L. (New Mexico Resonance, Albuquerque, NM); McDowell, Andrew F. (New Mexico Resonance, Albuquerque, NM)

2006-11-01

434

Deriving NMR surface relaxivities, pore size distributions and water retention curves by NMR relaxation experiments on partially de-saturated rocks  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) is a method used over a wide field of geophysical applications to non-destructively determine transport and storage properties of rocks and soils. In NMR relaxometry signal amplitudes correspond directly to the rock's fluid (water, oil) content. On the other hand the NMR relaxation behavior, i.e. the longitudinal (T1) and transverse (T2) NMR relaxation times, can be used to derive pore sizes and permeability as it is linearly linked to the pore's surface-to-volume-ratio and physiochemical properties of the rock-fluid interface by the surface relaxivity ?_s This parameter, however, is dependent on the type and mineral constituents of the investigated rock sample and thus has to be determined and calibrated prior to estimating pore sizes from NMR relaxometry measurements. Frequently used methods to derive surface relaxivity to calibrate NMR pore sizes comprise mercury injection, pulsed field gradients (PFG-NMR) or grain size analysis. This study introduces an alternative approach to jointly estimate NMR surface relaxivity and pore radii distributions using NMR relaxation data obtained from partially de-saturated rocks. In this, inverse modeling is carried on a linked Young Laplace equation for capillary bundles and the Brownstein and Tarr equations. Subsequently, this approach is used to predict water retention curves of the investigated rocks. The method was tested and validated on simulated and laboratory transverse NMR data. Calculated inverse models are generally in a good agreement with results obtained from mercury injection and drainage measurements. Left: Measured and predicted water retention (pF) curves. Center: NMR relaxometry data, fit and error. Right: Mercury injection data (HgPor, dashed line) and jointly derived pore radii distributions and surface relaxivity by joint inverse modelling

Mohnke, O.; Nordlund, C. L.; Klitzsch, N.

2013-12-01

435

Saliva metabolomics by NMR for the evaluation of sport performance.  

PubMed

The paper reports preliminary results of a study in order to verify that saliva is a bio-fluid sensitive to metabolite variations due to stress and fatigue in soccer athletes, and possibly, to identify potential markers of test of performance. Saliva samples of fourteen professional soccer players were collected before and after the stressful physical activity of the level 1 Yo-Yo intermittent recovery test and, also, physiological parameters were evaluated. The NMR spectra of saliva offer a metabolites profiling which was analyzed by Principal Component Analysis as a blind test. The results of NMR pre and post test shows that it was possible to cluster the best and the worst performing athletes and that the role of the actual player may be diagnosed by a different cluster of metabolites profile. Thus saliva can be considered a biofluid metabolically sensitive to the induced physical stress and, in the future, deeper investigated to monitor the performances in athletes. PMID:24176749

Santone, C; Dinallo, V; Paci, M; D'Ottavio, S; Barbato, G; Bernardini, S

2014-01-01

436

The study of macromolecular structure by pulsed NMR  

NASA Astrophysics Data System (ADS)

NMR has been widely used to determine chemical structure. The analysis of many important physical and physico-chemical properties such as molecular weight and mobility, the effect of crosslinking and entanglements and of solvents temperature, the role of crystalline regions and chain flexebility may be achieved very readily and simply these techniques. Once methods of analysis are understood and evaluated, they may serve only for the analysis of radiation effects but also for other forms of chemical treatment, the role of additives, orientation, and understanding and evaluation of important physical aspects, for which many of these polymers are intended. The use of pulsed NMR can also be used to evaluate radiation chemistry under different conditions, and it is expected that this knowledge could be extended to biological and medical systems, where a knowledge of the physical arrangements, mobility, entangled and other molecular properties and especially arrangement can be very important, yet difficult to measure.

Charlesby, Arthur

1995-06-01

437

IR, NMR and dielectric characterization of a novel tetramic acid  

NASA Astrophysics Data System (ADS)

The structure of the N-acetyl-3-hexanoyl tetramic acid has been elucidated by IR and NMR spectroscopy. The IR spectra showed absorption bands for the CO group of the ?-dicarbonyl system CO-CH-CO ?; C(OH)DC-CO as well as for the carbon-carbon double bond thus verifying the proposed structure. The 1H and 13C NMR spectra confirm the existence of enolic "internal" and "external" tautomers. The interconversion of "internal" tautomers seems to be faster than that of the "external" ones. The Thermally Stimulated Depolarization Currents (TSDC) spectrum in the temperature range 10-340 K revealed the presence of two predominant relaxation mechanisms, which are tentatively discussed in terms of the relaxation of tautomeric transformations under the influence of the applied electric field.

Vassilikou-Dova, A.; Kalogeras, I. M.; Petroliagi, M.; Igglessi-Markopoulou, O.; Markopoulos, J.

438

Two approaches to 3D reconstruction in NMR zeugmatography  

SciTech Connect

In nuclear magnetic resonance (NMR) zeugmatography, the primary data pertain to integrals of the unknown nuclear spin density f(x,y,z) over planes instead of lines in R/sup 3/. Two natural approaches to reconstructing f from such data are: (1) By numerical implementation of the inverse Radon transform in three dimensions (the direct approach), and (2) by application, in two successive stages, of existing well-known algorithms for inverting the two-dimensional Radon transform (the two-stage approach). These two approaches are discussed and compared, both from a theoretical standpoint and through computer results obtained with real NMR data. For the cases studied to date the two methods appear to produce qualitatively similar results.

Marr, R B; Chen, C N; Lauterbur, P C

1980-01-01

439

NMR and rotational angles in solution conformation of polypeptides  

NASA Astrophysics Data System (ADS)

Professor San-Ichiro Mizushima and Professor Yonezo Morino's classical contributions provided unique means and firm basis for understanding of conformational states and internal rotation in polypeptide molecules. Now the NMR spectroscopy is the best choice to study molecular conformation, mechanism of action and structure-functional relationships of peptide and proteins in solution under conditions approaching those of their physiological environments. Crucial details of spatial structure and interactions of these molecules in solution are revealed by using proton-proton and carbon-proton vicinal coupling constants, proton nuclear Overhauser effect and spectral perturbation techniques. The results of NMR conformational analysis are presented for valinomycin "bracelet", gramicidin A double helices, honey-bee neurotoxin apamin, scorpion insectotoxins and snake neurotoxins of long and short types.

Bystrov, V. F.

1985-01-01

440

Structure in an extreme environment: NMR at high salt.  

PubMed

Proteins from halophiles have adapted to challenging environmental conditions and require salt for their structure and function. How halophilic proteins adapted to a hypersaline environment is still an intriguing question. It is important to mimic the physiological conditions of the archae extreme halophiles when characterizing their enzymes, including structural characterization. The NMR derived structure of Haloferax volcanii dihydrofolate reductase in 3.5 M NaCl is presented, and represents the first high salt structure calculated using NMR data. Structure calculations show that this protein has a solution structure which is similar to the previously determined crystal structure with a difference at the N terminus of beta3 and the type of beta-turn connection beta7 and beta8. PMID:17656587

Binbuga, Bulent; Boroujerdi, Arezue F B; Young, John K

2007-08-01

441

NMR shifts for polycyclic aromatic hydrocarbons from first-principles  

SciTech Connect

We present first-principles, density-functional theory calculations of the NMR chemical shifts for polycyclic aromatic hydrocarbons, starting with benzene and increasing sizes up to the one- and two-dimensional infinite limits of graphene ribbons and sheets. Our calculations are performed using a combination of the recently developed theory of orbital magnetization in solids, and a novel approach to NMR calculations where chemical shifts are obtained from the derivative of the orbital magnetization with respect to a microscopic, localized magnetic dipole. Using these methods we study on equal footing the 1H and 13C shifts in benzene, pyrene, coronene, in naphthalene, anthracene, naphthacene, and pentacene, and finally in graphene, graphite, and an infinite graphene ribbon. Our results show very good agreement with experiments and allow us to characterize the trends for the chemical shifts as a function of system size.

Thonhauser, Timo; Ceresoli, Davide; Marzari, Nicola N.

2009-09-03

442

The granny and square carbyne knots: Theoretical NMR spectra  

NASA Astrophysics Data System (ADS)

The structure, stability and theoretical 13C NMR spectra of the C 60 carbon clusters of carbyne knot type were studied by the ab initio calculations. The C 60 carbyne six crossings granny and square knots (composite knots) belong to the D 2 and D 2 h point-group of symmetry, respectively, whereas all the six crossings prime-knots exhibit no symmetry. Semiempirical AM1 calculations performed for granny and square knots, formed from 40, 50,… 120 carbon atoms, show that the energy of the granny knot is always slightly lower than that of the square knot. The two mathematical knots are distinguishable only by using a sophisticated topological polynomial while the molecular carbyne granny and square knots seem to be easier differentiable experimentally by using the 13C NMR spectra.

Dobrowolski, Jan Cz.; Mazurek, Aleksandar P.

1999-05-01

443

NMR and rheological study of Aloe barbadensis partially acetylated glucomannan.  

PubMed

The structural and rheological properties of the Aloe extract (AE) and the polysaccharidic fraction (PF) obtained from the leaves pulp of Aloe barbadensis Miller were investigated. Structural analyses carried out by composition, methylation analysis and NMR spectroscopy showed that PF is mainly constituted by a partially acetylated 4-linked ?-d-glucomannan. The acetyl groups are located at C-2, C-2 and C-3, C-3 and/or C-6. The acetylation pattern of this type of polysaccharide was for the first time established using bidimensional NMR analyses. AE and PF aqueous solutions at 25°C showed a non-Newtonian behavior (with pseudoplastic characteristics), however PF showed higher apparent viscosity than AE. Dynamic oscillatory analyses showed that both samples, at the same concentration, behaved as a concentrated solution. PF presented higher values of G' compared with those of AE and this behavior could be consequence of its higher content in partially acetylated glucomannan. PMID:23544569

Campestrini, L H; Silveira, J L M; Duarte, M E R; Koop, H S; Noseda, M D

2013-04-15

444

A NMR guided approach for CsrA-RNA crystallization.  

PubMed

Structure determination of protein-nucleic acid complexes remains a challenging task. Here we present a simple method for generating crystals of a CsrA-nucleic acid complex, guided entirely by results from nuclear magnetic resonances spectroscopy (NMR) spectroscopy. Using a construct that lacks thirteen non-essential C-terminal residues, efficient binding to DNA could be demonstrated. One CsrA dimer interacts with two DNA oligonucleotides, similar to previous findings with RNA. Furthermore, the NMR study of the CsrA-DNA complex was the basis for successfully homing in on conditions that were suitable for obtaining crystals of the CsrA-DNA complex. Our results may be useful for those cases where RNA in protein-nucleic acid complexes may be replaced by DNA. PMID:23359257

Koharudin, Leonardus M I; Boelens, Rolf; Kaptein, Rob; Gronenborn, Angela M

2013-05-01

445

Optimized linear prediction for radial sampled multidimensional NMR experiments  

NASA Astrophysics Data System (ADS)

Radial sampling in multidimensional NMR experiments offers greatly decreased acquisition times while also providing an avenue for increased sensitivity. Digital resolution remains a concern and depends strongly upon the extent of sampling of individual radial angles. Truncated time domain data leads to spurious peaks (artifacts) upon FT and 2D FT. Linear prediction is commonly employed to improve resolution in Cartesian sampled NMR experiments. Here, we adapt the linear prediction method to radial sampling. Significantly more accurate estimates of linear prediction coefficients are obtained by combining quadrature frequency components from the multiple angle spectra. This approach results in significant improvement in both resolution and removal of spurious peaks as compared to traditional linear prediction methods applied to radial sampled data. The 'averaging linear prediction' (ALP) method is demonstrated as a general tool for resolution improvement in multidimensional radial sampled experiments.

Gledhill, John M.; Kasinath, Vignesh; Wand, A. Joshua

2011-09-01

446

Bayesian Weighting of Statistical Potentials in NMR Structure Calculation  

PubMed Central

The use of statistical potentials in NMR structure calculation improves the accuracy of the final structure but also raises issues of double counting and possible bias. Because statistical potentials are averaged over a large set of structures, they may not reflect the preferences of a particular structure or data set. We propose a Bayesian method to incorporate a knowledge-based backbone dihedral angle potential into an NMR structure calculation. To avoid bias exerted through the backbone potential, we adjust its weight by inferring it from the experimental data. We demonstrate that an optimally weighted potential leads to an improvement in the accuracy and quality of the final structure, especially with sparse and noisy data. Our findings suggest that no universally optimal weight exists, and that the weight should be determined based on the experimental data. Other knowledge-based potentials can be incorporated using the same approach.

Mechelke, Martin; Habeck, Michael

2014-01-01

447

NMR spectra of cluster-assembled nanophase metals  

SciTech Connect

Room temperature nuclear magnetic resonance (NMR) lineshapes are presented for cluster-assembled nanophase Cu and Ag with various grain sizes as measured using TEM. Both the {sup 65}Cu and {sup 63}Cu resonances are measured and compared. Both Cu isotopes are subject to Knight shifts and to couplings to the electric field gradients in the sample. The Cu NMR spectra have a strong central response which is broader but with an average Knight shift virtually identical to a large trained Cu sample. Though measureable signals can be seen for over a MHz, there is no evidence of Cu signal intensity centered at the non-Knight shifted (e.g. insulating) frequency. The Ag signals are measured at a much lower frequency and have reduced sensitivity but, since Ag has a nuclear spin of 1/2, the couplings to the electric field gradients are not present. The results are discussed in terms of predictions made using simple structural models.

Suits, B.H. [Michigan Tech. Univ., MI (United States); Siegel, R.W.; Liao, Y.X. [Argonne National Lab., Chicago, IL (United States)

1992-12-01

448

Optimized Linear Prediction for Radial Sampled Multidimensional NMR Experiments  

PubMed Central

Radial sampling in multidimensional NMR experiments offers greatly decreased acquisition times while also providing an avenue for increased sensitivity. Digital resolution remains concern and depends strongly upon the extent of sampling of individual radial angles. Truncated time domain data leads to spurious peaks (artifacts) upon FT and 2D FT. Linear prediction is commonly employed to improve resolution in Cartesian sampled NMR experiments. Here, we adapt the linear prediction method to radial sampling. Significantly more accurate estimates of linear prediction coefficients are obtained by combining quadrature frequency components from the multiple angle spectra. This approach results in significant improvement in both resolution and removal of spurious peaks as compared to traditional linear prediction methods applied to radial sampled data. The ‘averaging linear prediction’ (ALP) method is demonstrated as a general tool for resolution improvement in multidimensional radial sampled experiments.

Gledhill, John M.; Kasinath, Vignesh; Wand, A. Joshua

2011-01-01

449

Toward optimal-resolution NMR of intrinsically disordered proteins  

NASA Astrophysics Data System (ADS)

Proteins, which, in their native conditions, sample a multitude of distinct conformational states characterized by high spatiotemporal heterogeneity, most often termed as intrinsically disordered proteins (IDPs), have become a target of broad interest over the past 15 years. With the growing evidence of their important roles in fundamental cellular processes, there is an urgent need to characterize the conformational behavior of IDPs at the highest possible level. The unique feature of NMR spectroscopy in the context of IDPs is its ability to supply details of their structural and temporal alterations at atomic-level resolution. Here, we briefly review recently proposed NMR-based strategies to characterize transient states populated by IDPs and summarize the latest achievements and future prospects in methodological development. Because low chemical shift dispersion represents the major obstacle encountered when studying IDPs by