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1

Assessment of Pharmacological Treatment of Myocardial Infarction by Phosphorus-31 NMR with Surface Coils  

NASA Astrophysics Data System (ADS)

Phosphorus-31 nuclear magnetic resonance (NMR) measurements with small surface coils have been used to observe phosphorus metabolism of perfused hearts within localized regions. The method allows for direct, noninvasive, sequential assessment of the altered regional metabolism resulting from myocardial infarction and its response to drug treatment, which cannot be observed by conventional techniques.

Nunnally, Ray L.; Bottomley, Paul A.

1981-01-01

2

QUANTIFICATION OF MYO-INOSITOL HEXAKISPHOSPHATE IN ALKALINE SOIL EXTRACTS BY SOLUTION PHOSPHORUS 31 NMR SPECTROSCOPY AND SPECTRAL DECONVULTION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Inositol phosphates are the dominant class of organic phosphorus (P) compounds in most soils, but are poorly understood because they are not easily identified in soil extracts. This study reports a relatively simple technique using solution phosphorus 31 NMR spectroscopy and spectral deconvolution ...

3

Evaluation of Bone Mineral Density Using Three-Dimensional Solid State Phosphorus31 NMR Projection Imaging  

Microsoft Academic Search

.   A solid state magnetic resonance imaging technique is used to measure true three-dimensional mineral density of synthetic\\u000a hydroxyapatite phantoms and specimens of bone ex vivo. The phosphorus-31 free induction decay at 2.0 T magnetic field strength is sampled following application of a short, hard\\u000a radiofrequency excitation pulse in the presence of a fixed amplitude magnetic field gradient. Multiple gradient

Y. Wu; J. L. Ackerman; D. A. Chesler; J. Li; R. M. Neer; J. Wang; M. J. Glimcher

1998-01-01

4

Synthesis and characterization of polyphosphazene copolymers using phosphorus-31 NMR spectroscopy  

SciTech Connect

It was observed that competitive nucleophilic addition processes may be observed by {sup 31}P NMR spectroscopy. Methoxyethoxyethanol (MEE) and p-methoxyphenol readily substitute for chlorineonto phosphorus and the relative rates are generally comparable to each other. Sterically, the phenol presents is slightly larger than MEE but this does not appear to effect substitution judging by the observed PN(OAr){sub 2} NMR signal. These processes are still being studied.

Stewart, F.F.; Peterson, E.S.; Stone, M.L. [Lockheed Martin Idaho Technologies Co., Idaho Falls, ID (United States); Singler, R.E. [Military Academy, West Point, NY (United States). Dept. of Chemistry

1997-01-01

5

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

6

Phosphorus-31 NMR magnetization transfer measurements of metabolic reaction rates in the rat heart and kidney in vivo  

SciTech Connect

This dissertation is concerned with the measurement of the rates of ATP synthesis in the rat kidney and of the creatine kinase catalyzed reaction in the rat heart in situ. Chronically implanted detection coils, employing a balanced matching configuration of capacitors in the tuned circuit, were used to obtain /sup 31/P NMR spectra from heart, kidney, and liver in situ. Gated spectra of heart obtained at systole and diastole and the effects of fructose on kidney and liver were studied. The ability to observe other nuclei using implanted coils is illustrated with /sup 39/K NMR spectra from kidney and muscle. The theoretical considerations of applying magnetization transfer techniques to intact organs are discussed with emphasis on the problems associated with multiple exchange reactions and compartmentation of reactants. Experimental measurements of the ATP synthesis rate (13 ..mu..mol/min/gm tissue) were compared to whole kidney oxygen consumption and Na/sup +/ reabsorption rates to derive ATP/O (0.8 to 1.7) and Na/sup +//ATP (4 to 10) values. The problems associated with ATP synthesis rate measurements in kidney, e.g., the heterogeneity of the inorganic phosphate resonance, are discussed and experiments to overcome these problems proposed.

Koretsky, A.P.

1984-08-01

7

Phosphorus-31 NMR magnetization transfer measurements of metabolic reaction rates in the rat heart and kidney in vivo  

SciTech Connect

/sup 31/P NMR is a unique tool to study bioenergetics in living cells. The application of magnetization transfer techniques to the measurement of steady-state enzyme reaction rates provides a new approach to understanding the regulation of high energy phosphate metabolism. This dissertation is concerned with the measurement of the rates of ATP synthesis in the rat kidney and of the creatine kinase catalyzed reaction in the rat heart in situ. The theoretical considerations of applying magnetization transfer techniques to intact organs are discussed with emphasis on the problems associated with multiple exchange reactions and compartmentation of reactants. Experimental measurements of the ATP synthesis rate were compared to whole kidney oxygen consumption and Na/sup +/ reabsorption rates to derive ATP/O values. The problems associated with ATP synthesis rate measurements in kidney, e.g. the heterogeneity of the inorganic phosphate resonance, are discussed and experiments to overcome these problems proposed. In heart, the forward rate through creatine kinase was measured to be larger than the reverse rate. To account for the difference in forward and reverse rates a model is proposed based on the compartmentation of a small pool of ATP.

Koretsky, A.P.

1984-01-01

8

Sodium transport and phosphorus metabolism in sodium-loaded yeast: simultaneous observation with sodium-23 and phosphorus-31 NMR spectroscopy in vivo.  

PubMed

Simultaneous 23Na and 31P NMR spectra were obtained from a number of yeast suspensions. Prior to NMR spectroscopy, the yeast cells were Na-loaded: this replaced some of the intracellular K+ with Na+. These cells were also somewhat P-deficient in that they had no polyphosphate species visible in the 31P NMR spectrum. In the NMR experiments, the Na-loaded cells were suspended in media which contained inorganic phosphate, very low Na+, and a shift reagent for the Na+ NMR signal. The media differed as to whether dioxygen, glucose, or K+ was present individually or in combinations and as to whether the medium was buffered or not. The NMR spectra revealed that the cells always lost Na+ and gained phosphorus. However, the nature of the Na+ efflux time course and the P metabolism differed depending on the medium. The Na+ efflux usually proceeded linearly until the amount of Na+ extruded roughly equalled the amount of NH4+ and orthophosphate initially present in the medium (external phosphate was added as NH4H2PO4). Thus, we presume this first phase reflects a Na+ for NH4+ exchange. The Na+ efflux then entered a transition phase, either slowing, ceasing, or transiently reversing, before resuming at about the same value as that of the first phase. We presume that this last phase involves the simultaneous extrusion of intracellular anions as reported in the literature. The phosphorus metabolism was much more varied. In the absence of exogenous glucose, the P taken up accumulated first as intracellular inorganic phosphate; otherwise, it accumulated first in the "sugar phosphate" pool. In most cases, at least some of the P left the sugar phosphate pool and entered the polyphosphate reservoir in the vacuole. However, this never happened until the phase probably representing Na+ for NH4+ exchange was completed, and the P in the polyphosphate pool never remained there permanently but always eventually reverted back to the sugar phosphate pool. These changes are interpreted in terms of hierarchical energy demands on the cells under the different conditions. In particular, the energy for the Na+ for NH4+ exchange takes precedence over that required to produce and store polyphosphate. This conclusion is supported by the fact that when the cells are "forced" to exchange K+, as well as NH4+, for Na+ (by the addition of 5 times as much K+ to the NH4+-containing medium), polyphosphates are never significantly formed, and the initial linear Na+ efflux phase persists possibly 6 times as long.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3311159

Höfeler, H; Jensen, D; Pike, M M; Delayre, J L; Cirillo, V P; Springer, C S; Fossel, E T; Balschi, J A

1987-08-11

9

Phosphorus-31 NMR spectroscopy as a probe of models for the molybdenum-phosphate interaction in oxo-type molybdoenzymes and their cofactors  

SciTech Connect

Six mononuclear oxomolybdenum(V) and dioxomolybdenum(VI) complexes containing the hydrotris(3,5-dimethyl-1-pyrazolyl)borate ligand and a catechol- or phenol-based ligand with a pendant phosphate ester have been prepared and characterized by physical methods. Molecular modeling calculations show that the nonbonded Mo{hor ellipsis}P distances are restricted to 4-8 {angstrom}, depending upon the stereochemical constraints of the ligands. {sup 31}P NMR spectra of the Mo(V) complexes exhibit line broadening due to the d{sup 1} Mo(V) center. The observed relaxation times (T{sub 1} and T{sub 2}) are sensitive to the overall structure of the model compounds, and reasonable Mo{hor ellipsis}P distances can be calculated by using the Solomon equation. 32 refs., 1 fig., 1 tab.

Kuesthardt, U. (Univ. of Arizona, Tucson (USA) Universitaet Muenchen, Garching (West Germany)); LaBarre, M.J.; Enemark, J.H. (Univ. of Arizona, Tucson (USA))

1990-08-22

10

Phosphorus-31 NMR spectra of ethidium, quinacrine, and daunomycin complexes with poly(adenylic acid)ter dot poly(uridylic acid) RNA duplex and calf thymus DNA  

SciTech Connect

{sup 31}P NMR provides a convenient monitor of the phosphate ester backbone conformational changes upon binding of the intercalating drugs ethidium, quinacrine, and daunomycin to sonicated poly(A){center dot}poly(U) and calf thymus DNA. {sup 31}P chemical shifts can also be used to assess differences in the duplex unwinding angles in the presence of the drug. Thus a new {sup 31}P signal, 1.8-2.2 ppm downfield from the double-stranded helix signals, is observed in the ethidium ion-poly(A){center dot}poly(U) complex. This signal arises from phosphates which are in perturbed environments due to intercalation of the drug. This is in keeping with the hypothesis that the P-O ester torsional angle in phosphates linking the intercalated base pairs is more trans-like. Similar though smaller deshielding of the {sup 31}P signals is observed in sonicated poly(A){center dot}poly(U)-quinacrine complexes as well as in the daunomycin complexes. The effect of added ethidium ion, quinacrine, and daunomycin on the {sup 31}P spectra of sonicated calf thymus DNA is consistent with Wilson and Jones' (1982) earlier study. In these drug-DNA complexes the drug produces a gradual downfield shift in the DNA {sup 31}P signal without the appearance of a separate downfield peak. These differences are attributed to differences in the rate of chemical exchange of the drug between free and bound duplex states. The previous correlation of {sup 31}P chemical shift with drug duplex unwinding angle is confirmed for both the RNA and DNA duplexes.

Gorenstein, D.G.; Lai, K. (Purdue Univ., West Lafayette, IN (USA))

1989-04-04

11

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

12

Phosphorus31 magnetic resonance spectroscopy of the human liver  

Microsoft Academic Search

During the last decade, progresses in the field of nuclear magnetic resonance spectroscopy (MRS), have allowed metabolic studies of complex biological systems. Since the coming out of whole body magnets, clinical applications are possible; they utilize magnetic field gradients coupled with selective pulse sequences. The main nuclei which can be observed in vivo are the proton, the phosphorus-31 (31P) and

Marc Biran; Gerard Raffard; Pascal Kien; Paul CanioniI

1992-01-01

13

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

14

Detection of phosphorus species in sediments of artificial landscape lakes in China by fractionation and phosphorus-31 nuclear magnetic resonance spectroscopy.  

PubMed

Phosphorus (P) pollution in the sediments of seven artificial landscape lakes was studied via fractionation and phosphorus-31 nuclear magnetic resonance ((31)P NMR) spectroscopy. The lake sediments accumulated significant amounts of P from supplementation with reclaimed water and from runoff from the golf course lawns. The differences in total sediment P among lakes were correlated to the varied pollution extent from the lawns. One striking feature of the artificial lake sediments was the insufficiency of NaOH-extracted Al, which plays an important role in avoiding internal P release during anoxia. Another characteristic was the dominance of orthophosphate in the NaOH-EDTA extractants of the sediments, due to the heavy external P pollution. Phytate, considered prevalent in many soils and lake sediments, as well as polyphosphates and phosphonates which have appeared in some natural lake sediments, was not detected. The rank order of present biogenic P species was monoester-P>DNA-P>pyrophosphate>lipid-P. PMID:18804318

Liu, Jinyong; Wang, Hui; Yang, Haijun; Ma, Yanjun; Cai, Ouchen

2008-09-18

15

Phosphorus-31 NMR Studies of Cell Wall-Associated Calcium-Phosphates in Ulva lactuca.  

PubMed

Phosphate concentrations in the range 0.1 to 2.0 millimolar induced the formation of extracellular amorphous calcium-phosphates in the cell wall of the marine macro algae Ulva lactuca when they were cultivated in light in seawater at 20 degrees C. A broad resonance representing these compounds as well as resonances for extracellular orthophosphate and polyphosphates could be followed by (31)P-nuclear magnetic resonance spectroscopy. The presence of the calcium-phosphate made the cells brittle and it inhibited the growth of the macro algae and caused mortality within 1 week. The formation of the calcium-phosphates was influenced by the external phosphate concentration, the extracellular pH and the nature and concentration of the external nitrogen source. Furthermore, no formation of these compounds was observed when Ulva lactuca was cultivated in the dark, at low temperatures (5 degrees C) or in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The complex could be removed through washes with ethylenediaminetetraacetate; this treatment did not alter the intracellular pH or the orthophosphate and polyphosphate pools and it restored growth. PMID:16666741

Weich, R G; Lundberg, P; Vogel, H J; Jensén, P

1989-05-01

16

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

17

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

2012-03-19

18

A Sex-Specific Metabolite Identified in a Marine Invertebrate Utilizing Phosphorus-31 Nuclear Magnetic Resonance  

PubMed Central

Hormone level differences are generally accepted as the primary cause for sexual dimorphism in animal and human development. Levels of low molecular weight metabolites also differ between men and women in circulating amino acids, lipids and carbohydrates and within brain tissue. While investigating the metabolism of blue crab tissues using Phosphorus-31 Nuclear Magnetic Resonance, we discovered that only the male blue crab (Callinectes sapidus) contained a phosphorus compound with a chemical shift well separated from the expected phosphate compounds. Spectra obtained from male gills were readily differentiated from female gill spectra. Analysis from six years of data from male and female crabs documented that the sex-specificity of this metabolite was normal for this species. Microscopic analysis of male and female gills found no differences in their gill anatomy or the presence of parasites or bacteria that might produce this phosphorus compound. Analysis of a rare gynandromorph blue crab (laterally, half male and half female) proved that this sex-specificity was an intrinsic biochemical process and was not caused by any variations in the diet or habitat of male versus female crabs. The existence of a sex-specific metabolite is a previously unrecognized, but potentially significant biochemical phenomenon. An entire enzyme system has been synthesized and activated only in one sex. Unless blue crabs are a unique species, sex-specific metabolites are likely to be present in other animals. Would the presence or absence of a sex-specific metabolite affect an animal's development, anatomy and biochemistry?

Kleps, Robert A.; Myers, Terrell C.; Lipcius, Romuald N.; Henderson, Thomas O.

2007-01-01

19

Proton and carbon lanthanide-induced shifts in aqueous alanine. Evidence for structural changes along the lanthanide series  

Microsoft Academic Search

Proton and carbon lanthanide-induced shifts are reported for aqueous alanine at pH 3. A comparison of the measured shifts with theoretical values provides evidence for changes in the coordination behavior of alanine between Tb\\/sup 3 +\\/ and DY\\/sup 3 +\\/. An apparent stability constant (K⁠= 0.7 +- 0.1 M⁻¹) was measured for eight lanthanide ions and found insensitive to

A. Dean Sherry; E. Pascual

1977-01-01

20

Phosphorus-31 MRI of bones using quadratic echo line-narrowing  

NASA Astrophysics Data System (ADS)

There is a great need to probe the internal composition of bone on the sub-0.1 mm length scale, both to study normal features and to look for signs of disease. Despite the obvious importance of the mineral fraction to the biomechanical properties of skeletal tissue, few non-destructive techniques are available to evaluate changes in its chemical structure and functional microarchitecture on the interior of bones. MRI would be an excellent candidate, but bone is a particularly challenging tissue to study given the relatively low water density and wider linewidths of its solid components. Recent fundamental research in quantum computing gave rise to a new NMR pulse sequence - the quadratic echo - that can be used to narrow the broad NMR spectrum of solids. This offers a new route to do high spatial resolution, 3D ^31P MRI of bone that complements conventional MRI and x-ray based techniques to study bone physiology and structure. We have used our pulse sequence to do 3D ^31P MRI of ex vivo bones with a spatial resolution of (sub-450 ?m)^3, limited only by the specifications of a conventional 4 Tesla liquid-state MRI system. We will describe our plans to push this technique towards the factor of 1000 increase in spatial resolution imposed by fundamental limits.

Frey, Merideth; Barrett, Sean; Insogna, Karl; Vanhouten, Joshua

2012-02-01

21

Transport and phosphorylation of choline in higher plant cells. Phosphorus-31 nuclear magnetic resonance studies  

SciTech Connect

When sycamore cells were suspended in basal medium containing choline, the latter was taken up by the cells very rapidly. A facilitated diffusion system appertained at low concentrations of choline and exhibited Michaelis-Menten kinetics. At higher choline concentrations simple diffusion appeared to be the principal mode of uptake. Addition of choline to the perfusate of compressed sycamore cells monitored by /sup 31/P NMR spectroscopy resulted in a dramatic accumulation of P-choline in the cytoplasmic compartment containing choline kinase and not in the vacuole. The total accumulation of P-choline over a 10-h period exhibited Michaelis-Menten kinetics. During this period, in the absence of Pi in the perfusion medium there was a marked depletion of glucose-6-P, and the cytoplasmic Pi resonance disappeared almost completely. When a threshold of cytoplasmic Pi was attained, the phosphorylation of choline was sustained by the continuous release of Pi from the vacuole although at a much lower rate. However, when 100 microM inorganic phosphate was present in the perfusion medium, externally added Pi was preferentially used to sustain P-choline synthesis. It is clear, therefore, that cytosolic choline kinase associated with a carrier-mediated transport system for choline uptake appeared as effective systems for continuously trapping cytoplasmic Pi including vacuolar Pi entering the cytoplasm.

Bligny, R.; Foray, M.F.; Roby, C.; Douce, R.

1989-03-25

22

Phosphorus-31 nuclear magnetic resonance spectroscopy of human retinoblastoma cells: correlation with metabolic indices.  

PubMed

The 31P nuclear magnetic resonance spectrum of cultured human Y-79 retinoblastoma cells was obtained at 121 MHz on intact cells trapped in agarose threads. The spectrum was dominated by monoester peaks, which varied in relative concentration from preparation to preparation. Resonances from phosphocreatine, phosphodiesters and diphosphodiesters also exhibited variability relative to ATP. The main monoester was identified as phosphorylcholine by 31P-NMR of perchloric acid extracts. It was determined that the changes in monoester concentration correlated with feeding pattern. Phosphorus spectra of cells 1, 2 and 3 days post feeding showed a 40% decrease in the relative concentration of phosphorylcholine concentration over the 3 day period. Phosphocreatine, phosphodiesters and diphosphodiesters increased relative to ATP during the same period. Growth curve experiments and oxygen consumption measurements indicated that the decrease in phosphorylcholine correlated with a decrease in cellular growth and oxygen consumption. We conclude that monoester concentration may be a useful indicator of nutritional status in these cells and possibly in intact tumors. PMID:3401510

Miceli, M V; Kan, L S; Newsome, D A

1988-07-29

23

Positron emission tomography of fluorine-18-deoxyglucose and image-guided phosphorus-31 magnetic resonance spectroscopy in brain tumors  

SciTech Connect

Positron emission tomography (PET) of 2(18F)-fluoro-2-deoxy-D-glucose (FDG) and volume-selective phosphorus-31 magnetic resonance spectroscopy (31P-MRS) are methods used to assess the energy metabolism of the brain. Both methods were studied with respect to their contribution to differential diagnosis in 23 patients with various brain tumors. The various neuroectodermal tumors differed with respect to their metabolic rate for glucose (MRGL). Benign and malignant tumors could be better differentiated by using tumor metabolism relative to contralateral brain and by evaluating heterogeneities in tumors. Low-grade gliomas usually showed normal 31P-MR spectra; high-grade gliomas were characterized by reduced and often split phosphodiester peaks and alkaline pH. Meningiomas, which had variable MRGL, typically showed extremely low phosphocreatine levels, reduced phosphodiesters, and alkaline pH. We concluded that FDG-PET and 31P-MRS examine different aspects of tumor metabolism. Therefore, both can contribute independently and complementarily to the differential diagnosis of brain tumors.

Heiss, W.D.; Heindel, W.; Herholz, K.; Rudolf, J.; Bunke, J.; Jeske, J.; Friedmann, G. (Universitaet zu Koeln (Germany, F.R.))

1990-03-01

24

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

25

Relationship between myocardial metabolites and contractile abnormalities during graded regional ischemia. Phosphorus-31 nuclear magnetic resonance studies of porcine myocardium in vivo.  

PubMed Central

The mechanisms responsible for changes in myocardial contractility during regional ischemia are unknown. Since changes in high-energy phosphates during ischemia are sensitive to reductions in myocardial blood flow, it was hypothesized that myocardial function under steady-state conditions of graded regional ischemia is closely related to changes in myocardial high-energy phosphates. Therefore, phosphorus-31 nuclear magnetic resonance spectroscopy was employed in an in vivo porcine model of graded coronary stenosis. Simultaneous measurements of regional subendocardial blood flow, high-energy phosphates, pH, and myocardial segment shortening were made during various degrees of regional ischemia in which subendocardial blood flow was reduced by 16-94%. During mild reductions in myocardial blood flow (subendocardial blood flow = 83% of nonischemic myocardium), only the ratio of phosphocreatine to inorganic phosphate (PCr/Pi), Pi, and [H+] were significantly changed from control. PCr, ATP, and PCr/ATP were not significantly reduced from control with mild reductions in blood flow. Changes in myocardial segment shortening were most closely associated with changes in PCr/Pi (r = 0.94). Pi and [H+] were negatively correlated with segment shortening (r = -0.64 and -0.58, respectively) and increased over twofold when blood flow was reduced by 62%. Thus, these data demonstrate that PCr/Pi is sensitive to reductions in myocardial blood flow and closely correlates with changes in myocardial function. These data are also consistent with a role for Pi or H+ as inhibitors of myocardial contractility during ischemia. Images

Schaefer, S; Schwartz, G G; Gober, J R; Wong, A K; Camacho, S A; Massie, B; Weiner, M W

1990-01-01

26

Phosphorus forms and chemistry in the soil profile under long-term conservation tillage: a phosphorus-31 nuclear magnetic resonance study.  

PubMed

In many regions, conservation tillage has replaced conventional tilling practices to reduce soil erosion, improve water conservation, and increase soil organic matter. However, tillage can have marked effects on soil properties, specifically nutrient redistribution or stratification in the soil profile. The objective of this research was to examine soil phosphorus (P) forms and concentrations in a long-term study comparing conservation tillage (direct drilling, "No Till") and conventional tillage (moldboard plowing to 20 cm depth, "Till") established on a fine sandy loam (Orthic Humo-Ferric Podzol) in Prince Edward Island, Canada. No significant differences in total carbon (C), total nitrogen (N), total P, or total organic P concentrations were detected between the tillage systems at any depth in the 0- to 60-cm depth range analyzed. However, analysis with phosphorus-31 nuclear magnetic resonance spectroscopy showed differences in P forms in the plow layer. In particular, the concentration of orthophosphate was significantly higher under No Till than Till at 5 to 10 cm, but the reverse was true at 10 to 20 cm. Mehlich 3-extractable P was also significantly higher in No Till at 5 to 10 cm and significantly higher in Till at 20 to 30 cm. This P stratification appears to be caused by a lack of mixing of applied fertilizer in No Till because the same trends were observed for pH and Mehlich 3-extractable Ca (significantly higher in the Till treatment at 20 to 30 cm), reflecting mixing of applied lime. The P saturation ratio was significantly higher under No Till at 0 to 5 cm and exceeded the recommended limits, suggesting that P stratification under No Till had increased the potential for P loss in runoff from these sites. PMID:21043270

Cade-Menun, Barbara J; Carter, Martin R; James, Dean C; Liu, Corey W

27

Enantiomeric differentiation of acyclic terpenes by 13C NMR spectroscopy using a chiral lanthanide shift reagent.  

PubMed

The 13C NMR behaviour of ten acyclic terpene alcohols was examined in the presence of a chiral lanthanide shift reagent (CLSR). For each alcohol, we measured the lanthanide-induced shift (LIS) on the signals of the carbons and the splitting of some signals, which allowed the enantiomeric differentiation. As expected, the LIS decreased with the number of bonds between the binding function and the considered carbon. The enantiomeric splitting is observed for several signals in the spectrum of each compound. The influence of the hindrance of the binding function (primary, secondary or tertiary alcohol) and that of the stereochemistry of the double bonds is discussed. PMID:15593244

Blanc, Marie-Cécile; Bradesi, Pascale; Casanova, Joseph

2005-02-01

28

Comparison of Phosphorus Forms in Wet and Dried Animal Manures by Solution Phosphorus-31 Nuclear Magnetic Resonance Spectroscopy and Enzymatic Hydrolysis  

Technology Transfer Automated Retrieval System (TEKTRAN)

Both enzymatic hydrolysis and solution 31P nuclear magnetic resonance (NMR) spectroscopy have been used to characterize P compounds in animal manures. However, no comparison of the two methods has been reported in the literature. In this study, we compared P compounds in dairy and poultry manures i...

29

A novel technique for the pre-concentration and extraction of inositol hexakisphosphate from soil extracts with determination by phosphorus-31 nuclear magnetic resonance.  

PubMed

Inositol hexakisphosphate (IP6) is often the dominant form of soil organic phosphorus (P), but is rarely investigated because of the analytical difficulties encountered in its extraction, separation, and detection in environmental samples. In particular, recent advances in the study of soil organic P with 31P nuclear magnetic resonance (NMR) have been of limited use for the study of IP6, because the technique does not discriminate between IP6 and other forms of P. This was addressed by developing a novel analytical procedure using the retentive properties of gel-filtration gels for IP6, which allows the combined selective extraction and pre-concentration of IP6 from soil extracts with determination by 31P NMR. While the technique is still in the developmental stage, the results demonstrate that the gel does not interfere with 31P NMR analysis and retains IP6 to concentrations well above those required to give clear spectral signals. The technique has considerable potential for application to the study of IP6 in soil extracts and water samples and, with development, could help to answer fundamental questions regarding the dynamics of organic P in the environment. PMID:11931435

Turner, Benjamin L; McKelvie, Ian D

30

Caution needed in pretreatment of sediments for refining phosphorus-31 nuclear magnetic resonance analysis: results from a comprehensive assessment of pretreatment with ethylenediaminetetraacetic acid.  

PubMed

Pretreatment with chemicals such as ethylenediaminetetraacetic acid (EDTA) is often used to improve the analysis of sediment P with solution P-31 nuclear magnetic resonance spectroscopy (35P-NMR), but there is a lack of a comprehensive assessment of the methodology. In this study, the effects of EDTA pretreatment on sediment P extracted using a mixture of 0.25 mol L(-1) NaOH and 50 mmol L(-1) EDTA (NaOH-EDTA) were examined with 45 different sediments. The results showed that EDTA pre-extraction decreased the amount of P extracted by NaOH-EDTA when the concentration ratio of sediment Ca to the sum of sediment Fe and Al [Ca/(Fe+Al), on a wt/vol basis] was lower than 0.4. An increase in total extracted P, coupled with substantial increases in total extracted paramagnetic ions such as Fe and Mn, was observed for another group of sediments with Ca/(Fe+Al) > 0.5, possibly due to the matrix effect. Analysis of 16 representative sediments with 31P-NMR showed that orthophosphate diesters were substantially removed by EDTA pre-extraction for sediments with Ca/ (Fe+Al) between 0.4 and 0.7, reflecting a high risk posed by this pretreatment. Phosphorus diversity and concentration of individual P compounds were markedly improved for sediments with Ca/(Fe+Al) > 0.7, suggesting that EDTA pretreatment was particularly useful for 31P-NMR analysis of calcareous sediments. The present study showed that sediment properties played an important role in determining pretreatment effects. Caution is advised when applying pretreatment methods to different sediments. PMID:21043272

Ding, ShiMing; Bai, Xiuling; Fan, Chengxin; Zhang, Lu

31

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

32

Studies on drug-DNA complexes, adriamycin-d-(TGATCA)(2) and 4'-epiadriamycin-d-(CGATCG)(2), by phosphorus-31 nuclear magnetic resonance spectroscopy.  

PubMed

The complexes of adriamycin-d-(TGATCA)(2) and 4'-epiadriamycin-d-(CGATCG)(2) are studied by one- and two-dimensional (31)P nuclear magnetic resonance spectroscopy (NMR) at 500 MHz in the temperature range 275-328 K and as a function of drug to DNA ratio (0.0-2.0). The binding of drug to DNA is clearly evident in (31)P-(31)P exchange NOESY spectra that shows two sets of resonances in slow chemical exchange. The phosphate resonances at the intercalating steps, T1pG2/C1pG2 and C5pA6/C5pG6, shift downfield up to 1.7 ppm and that at the adjacent step shift downfield up to 0.7 ppm, whereas the central phosphate A3pT4 is relatively unaffected. The variations of chemical shift with drug to DNA ratio and temperature as well as linewidths are different in each of the two complexes. These observations reflect change in population of B(I)/B(II) conformation, stretching of backbone torsional angle zeta, and distortions in O-P-O bond angles that occur on binding of drug to DNA. To the best of our knowledge, there are no solution studies on 4'-epiadriamycin, a better tolerated drug, and binding of daunomycin or its analogue to d-(TGATCA)(2) hexamer sequence. The studies report the use of (31)P NMR as a tool to differentiate various complexes. The specific differences may well be the reasons that are responsible for different antitumor action of these drugs due to different binding ability and distortions in DNA. PMID:19170249

Agrawal, Prashansa; Govil, Girjesh; Barthwal, Ritu

2009-05-01

33

Comparative carbon-13, nitrogen-15, and phosphorus-31 nuclear magnetic resonance study on the flavodoxins from Clostridium MP, Megasphaera elsdenii, and Azotobacter vinelandii  

SciTech Connect

The flavodoxins from Megasphaera elsdenii, Clostridium MP, and Azotobacter vinelandii were studied by /sup 13/C, /sup 15/N, and /sup 31/P NMR techniques by using various selectivity enriched oxidized riboflavin 5'-phosphate (FMN) derivatives. It is shown that the ..pi.. electron distribution in protein-bound flavin differs from that of free flavin and depends also on the apoflavoprotein used. In the oxidized state Clostridium MP and M. elsdenii flavodoxins are very similar with respect to specific hydrogen bond interaction between FMN and the apoprotein and the electronic structure of flavin. A vinelandii flavodoxin differs from these flavodoxins in both respects, but it also differs from Desulfovibrio vulgaris flavodoxin. The similarities between A. vinelandii and D. vulgaris flavodoxins are greater than the similarities with the other two flavodoxins. The differences in the ..pi.. electron distribution in the FMN of reduced flavodoxins from A. vinelandii and D. vulgaris are even greater, but the hydrogen bond patterns between the reduced flavins and the apoflavodoxins are very similar. In the reduced state all flavodoxins studied contain an ionized prosthetic group and the isoalloxazine ring is in a planar conformation. The results are compared with existing three-dimensional data and discussed with respect to the various possible mesomeric structures in protein-bound FMN. The results are discussed in light of the proposed hypothesis that specific hydrogen bonding to the protein-bound flavin determines the specific biological activity of a particular flavoprotein.

Vervoort, J.; Mueller, F.; Mayhew, S.G.; van den Berg, W.A.M.; Moonen, C.T.W.; Bacher, A.

1986-11-04

34

Inverse 31P ? 1H NMR cross-polarization in hydrated nanocrystalline calcium hydroxyapatite  

NASA Astrophysics Data System (ADS)

Hydrated nanocrystalline calcium hydroxyapatite was studied using unconventional solid-state NMR technique with cross-polarization from phosphorus-31 to protons (31P ? 1H CP) under magic-angle spinning (MAS). Two peaks were detected: at 0.0 ppm from structural hydroxyl groups and at 5.4 ppm from water. Their intensities were monitored as a function of the contact time. It was found that there were two types of water adsorbed on the crystal surface: typical strongly bound water and distinct, more mobile water associated with a particular 31P environment capable of fast spin-lattice relaxation in the rotating frame. Relative contents of protons in various material compartments were estimated.

Kolmas, Joanna; Kolodziejski, Waclaw

2012-12-01

35

Kinetics of 1H --> 31P NMR cross-polarization in bone apatite and its mineral standards.  

PubMed

Kinetics of NMR cross-polarization (CP) from protons to phosphorus-31 nuclei was studied in the following samples: mineral of whole human bone, apatite prepared from bone, natural brushite, synthetic hydroxyapatite (hydrated and calcined), and synthetic carbonatoapatite of type B with 9 wt% of CO(3) (2-). In order to avoid an effect of magic angle spinning on CP and relaxation, the experiments were carried out on static samples. Parameters of the CP kinetics were discussed for trabecular and cortical bone tissue from adult subjects in comparison to the synthetic mineral standards. It was found that carbonatoapatite shows similar CP behavior to the bone mineral. Both materials undergo two-component CP kinetics. The fast-relaxing classical component is from the surface of apatite crystals and the slow-relaxing nonclassical component comes from the crystal interior. The components have been unambiguously assigned using inverse CP from phosphorus-31 to protons. The study provides information on a structured water layer, which covers crystal surface of carbonato- and bone apatite. The layer encompasses ca 40% of apatite phosphorus and its thickness is more than ca 2 nm. PMID:18306247

Kaflak, Agnieszka; Kolodziejski, Waclaw

2008-04-01

36

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

37

Enantiomeric differentiation of oxygenated p-menthane derivatives by 13C NMR using Yb(hfc)3.  

PubMed

The (13)C NMR behaviour of 21 p-menthanic terpene bearing an oxygenated function (alcohol, ketone, acetate) was examined in the presence of a chiral lanthanide shift reagent (Yb(hfc)(3)). For each monocyclic compound, we measured the lanthanide-induced shift (LIS) on the signals of the carbons and the splitting of signals allowing the enantiomeric differentiation. Some general features were found about their LIS behaviour: experimental data establishing distinct patterns for carvomenthone-like compounds and menthone-like compounds. The enantiomeric splitting was observed for the majority of signals in the spectrum of each compound. In the case of alcohols and acetates, the influence of the relative stereochemistry (cis vs trans) of isopropyl(ene) and the binding function was discussed. PMID:18828150

Lanfranchi, Don Antoine; Blanc, Marie-Cécile; Vellutini, Muriel; Bradesi, Pascale; Casanova, Joseph; Tomi, Félix

2008-12-01

38

NMR imaging  

SciTech Connect

Since hydrogen is the most abundant element in all living organisms, proton NMR lends itself well as a method of investigation in biology and medicine. NMR imaging has some special advantages as a diagnostic tool: no ionizing radiation is used, it is noninvasive; it provides a safer means of imaging than the use of x-rays, gamma rays, positrons, or heavy ions. In contrast with ultrasound, the radiation penetrates the bony structures without attenuation. In additional to morphological information, NMR imaging provides additional diagnostic insights through relaxation parameters, which are not available from other imaging methods. In the decade since the first primitive NMR images were obtained, the quality of images now obtained approaches those from CT x-ray scanners. Prototype instruments are being constructed for clinical evaluation and the first whole-body scanners are beginning to appear on the market at costs comparable to CT scanners. Primary differences in equipment for conventional NMR and NMR imaging are the much larger aperture magnets that are required for the examination of human subjects and the addition of coils to generate field gradients and facilities for manipulating the gradients. Early results from clinical trials in many parts of the world are encouraging, and in a few years, the usefuleness of this modality of medical imaging to the medical profession in diagnosis and treatment of disease will be defined. 10 figures.

Andrew, E.R.

1983-04-01

39

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

2013-04-15

40

Freezing point depression of water in phospholipid membranes: a solid-state NMR study.  

PubMed

Lipid-water interaction plays an important role in the properties of lipid bilayers, cryoprotectants, and membrane-associated peptides and proteins. The temperature at which water bound to lipid bilayers freezes is lower than that of free water. Here, we report a solid-state NMR investigation on the freezing point depression of water in phospholipid bilayers in the presence and absence of cholesterol. Deuterium NMR spectra at different temperatures ranging from -75 to + 10 degrees C were obtained from fully (2)H2O-hydrated POPC (1-palmitoyl-2-oleoylphosphatidylcholine) multilamellar vesicles (MLVs), prepared with and without cholesterol, to determine the freezing temperature of water and the effect of cholesterol on the freezing temperature of water in POPC bilayers. Our 2H NMR experiments reveal the motional behavior of unfrozen water molecules in POPC bilayers even at temperatures significantly below 0 degrees C and show that the presence of cholesterol further lowered the freezing temperature of water in POPC bilayers. These results suggest that in the presence of cholesterol the fluidity and dynamics of lipid bilayers can be retained even at very low temperatures as exist in the liquid crystalline phase of the lipid. Therefore, bilayer samples prepared with a cryoprotectant like cholesterol should enable the performance of multidimensional solid-state NMR experiments to investigate the structure, dynamics, and topology of membrane proteins at a very low temperature with enhanced sample stability and possibly a better sensitivity. Phosphorus-31 NMR data suggest that lipid bilayers can be aligned at low temperatures, while 15N NMR experiments demonstrate that such aligned samples can be used to enhance the signal-to-noise ratio of is 15N chemical shift spectra of a 37-residue human antimicrobial peptide, LL-37. PMID:18991419

Lee, Dong-Kuk; Kwon, Byung Soo; Ramamoorthy, Ayyalusamy

2008-12-01

41

Trimethyl phosphite adsorbed on silica: An NMR and infrared study  

SciTech Connect

Infrared spectroscopy and phosphorus-31 magic angle spinning nuclear magnetic resonance spectroscopy have been used to study the adsorption of trimethyl phosphite (TMP) on silica. At 23 C TMP reacts rapidly with surface silanol groups to give SiOCH{sub 3} as a chemisorbed product and liquid dimethyl phospite (DMP). However, formation of DMP ceases when about half of the SiOH groups have been consumed because DMP strongly hydrogen bonds to the remaining silanols thereby inhibiting further reaction between TMP and SiOH. TMP also undergoes isomerization to dimethyl methylphosphonate (DMMP) which is catalyzed by SiOH. As the number of initial silanol groups is decreased (by using higher temperatures of vacuum activation) the quantity of DMP produced decreases whereas that of DMMP increases. A mechanism for formation of DMP and DMMP has been suggested. At 100C isomerization does not occur, all SiOH groups are consumed, and the major product is DMP/SiOCH{sub 3} accompanied by a small quantity of a chemisorbed phosphorus-containing species having the proposed structure (SiO){sub 2}P-H({double bond}O). The latter is stable up to 400C. If TMP is heated with silica from 100 to 400C, in addition to SiOCH{sub 3}, the major new chemisorbed product of the reaction which can be identified by IR and NMR is (SiO){sub 2}P-Me({double bond}O) (Me = CH{sub 3}). The advantages of a combined IR-NMR approach is discussed.

Gay, I.D. (Simon Fraser Univ., Burnaby, British Columbia (Canada)); McFarlan, A.J.; Morrow, B.A. (Univ. of Ottawa, Ontario (Canada))

1991-02-07

42

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

43

The Basics of NMR  

NSDL National Science Digital Library

This resource is an online textbook containing information about Nuclear Magnetic Resonance (NMR). Information inlcudes mathhematics of NMR, spin physics, Spectroscopy, pulse sequences, and NMR hardware. The "Practical Considerations" chapter emphasizes spectroscopic techniques.

Hornak, Joseph

2003-10-10

44

31P-NMR spectroscopy of perifused rat hepatocytes immobilized in agarose threads: application to chemical-induced hepatotoxicity.  

PubMed

A system consisting of isolated rat hepatocytes immobilized in agarose threads continuously perifused with oxygenated Krebs-Henseleit (KH) solution has been found to maintain cell viability with excellent metabolic activity for more than 6 h. The hepatocytes were monitored by phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy at 4.7 Tesla, by measurement of oxygen consumption and by the leakage of lactate dehydrogenase (LD) and alanine aminotransferase (ALT). The data obtained were comparable to those found for an isolated perfused whole liver in vitro. The effects of allyl alcohol (AA), ethanol, and 4-acetaminophenol (AP) were examined. A solution of 225 microM AA perifused for 90 min caused the disappearance of the beta-phosphate resonance of adenosine triphosphate (ATP) in the 31P-NMR spectra, a 7-fold increase in LD leakage and a 70% reduction in oxygen consumption. Ethanol (1.0 M) perifused for 90 min reduced the beta-ATP signal intensity ratio by 20%, the phosphomonoester (PME) signal by 50% and inorganic phosphate (Pi) by 33% (P less than 0.05). AP (10 mM) caused only mild liver-cell damage. The results demonstrate that perifused immobilized hepatocytes can be used as a liver model to assess the effects of a wide range of chemicals and other xenobiotics by NMR spectroscopy. PMID:1610910

Farghali, H; Rossaro, L; Gavaler, J S; Van Thiel, D H; Dowd, S R; Williams, D S; Ho, C

1992-06-01

45

Thermal phase behavior of DMPG bilayers in aqueous dispersions as revealed by 2H- and 31P-NMR.  

PubMed

The synthetic lipid 1,2-dimyristoyl-sn-3-phosphoglycerol (DMPG), when dispersed in water/NaCl exhibits a complex phase behavior caused by its almost unlimited swelling in excess water. Using deuterium ((2)H)- and phosphorus ((31)P)-NMR we have studied the molecular properties of DMPG/water/NaCl dispersions as a function of lipid and NaCl concentration. We have measured the order profile of the hydrophobic part of the lipid bilayer with deuterated DMPG while the orientation of the phosphoglycerol headgroup was deduced from the (31)P NMR chemical shielding anisotropy. At temperatures >30 °C we observe well-resolved (2)H- and (31)P NMR spectra not much different from other liquid crystalline bilayers. From the order profiles it is possible to deduce the average length of the flexible fatty acyl chain. Unusual spectra are obtained in the temperature interval of 20-25 °C, indicating one or several phase transitions. The most dramatic changes are seen at low lipid concentration and low ionic strength. Under these conditions and at 25 °C, the phosphoglycerol headgroup rotates into the hydrocarbon layer and the hydrocarbon chains show larger flexing motions than at higher temperatures. The orientation of the phosphoglycerol headgroup depends on the bilayer surface charge and correlates with the degree of dissociation of DMPG-Na(+). The larger the negative surface charge, the more the headgroup rotates toward the nonpolar region. PMID:21732628

Loew, Caroline; Riske, Karin A; Lamy, M Teresa; Seelig, Joachim

2011-07-20

46

1H and 31P NMR Lipidome of Ethanol-Induced Fatty Liver  

PubMed Central

Background Hepatic steatosis (fatty liver), an early and reversible stage of alcoholic liver disease, is characterized by triglyceride deposition in hepatocytes, that can advance to steatohepatitis, fibrosis, cirrhosis, and ultimately to hepatocellular carcinoma. In the present work, we studied altered plasma and hepatic lipid metabolome (lipidome) to understand the mechanisms and lipid pattern of early stage alcohol induced-fatty liver. Methods Male Fischer 344 rats were fed 5% alcohol in a Lieber-DeCarli diet. Control rats were pair-fed an equivalent amount of maltose-dextrin. After one month, animals were sacrificed and plasma collected. Livers were excised for morphological, immunohistochemical, and biochemical studies. The lipids from plasma and livers were extracted with methyl-tert-butyl ether and analyzed by 750/800 MHz proton nuclear magnetic resonance (1H NMR) and phosphorus (31P) NMR spectroscopy on a 600 MHz spectrometer. The NMR data were then subjected to multivariate statistical analysis. Results Hemotoxylin & Eosin and Oil Red O stained liver sections showed significant fatty infiltration. Immunohistochemical analysis of liver sections from ethanol-fed rats showed no inflammation (absence of CD3 positive cells) or oxidative stress (absence of malondialdehyde reactivity or 4-hydroxynonenal positive straining). Cluster analysis and principal component analysis of 1H NMR data of lipid extracts of both plasma and livers showed a significant difference in the lipid metabolome of ethanol-fed vs. control rats. 31P NMR data of liver lipid extracts showed significant changes in phospholipids similar to 1H NMR data. 1H NMR data of plasma and liver reflected several changes while comparison of 1H NMR and 31P NMR data offered a correlation among the phospholipids. Conclusions Our results show that alcohol consumption alters metabolism of cholesterol, triglycerides and phospholipids that could contribute to the development of fatty liver. These studies also indicate that fatty liver precedes oxidative stress and inflammation. The similarities observed in plasma and liver lipid profiles offer a potential methodology for detecting early stage alcohol-induced fatty liver disease by analyzing the plasma lipid profile.

Fernando, Harshica; Kondraganti, Shakuntala; Bhopale, Kamlesh K.; Volk, David E.; Neerathilingam, Muniasamy; Kaphalia, Bhupendra S.; Luxon, Bruce A.; Boor, Paul J.; Ansari, G. A. Shakeel

2011-01-01

47

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

48

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

49

NMR analysis of biodiesel  

Technology Transfer Automated Retrieval System (TEKTRAN)

Biodiesel is usually analyzed by the various methods called for in standards such as ASTM D6751 and EN 14214. Nuclear magnetic resonance (NMR) is not one of these methods. However, NMR, with 1H-NMR commonly applied, can be useful in a variety of applications related to biodiesel. These include monit...

50

NMR Spectroscopy - Theory  

NSDL National Science Digital Library

This web site begins with a simple quantum description of NMR and proceeds to introduce resonance absorption, relaxation, chemical shifts, and scalar couplings. This site will be useful for advanced undergraduate students needing a description of NMR that is more detailed than that given in most introductory Organic texts.

Lord, J. R.

2011-06-30

51

Lectures on pulsed NMR  

SciTech Connect

These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 55 figs.

Pines, A.

1986-09-01

52

Lectures on pulsed NMR  

SciTech Connect

These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 32 refs., 56 figs.

Pines, A.

1988-08-01

53

Flow measurements by NMR  

Microsoft Academic Search

We review the current status of liquid flow velocity studies by pulsed nuclear magnetic resonance (NMR). NMR is a non-invasive method that is most sensitive to protons, so that, combined with the recently developed imaging capabilities, it is now possible to obtain images of hydrodynamic parameters of interest for most common liquids. Such parameters can include, besides velocity, diffusion coefficient,

A. Caprihan; E. Fukushima

1990-01-01

54

Progressive saturation NMR relaxation  

NASA Astrophysics Data System (ADS)

The NMR spin-lattice relaxation rate, T-11, can be measured precisely by progressive saturation. This efficient technique is useful when T1 is long and the NMR signal is weak. We derive the quasiequilibrium spin response to excitation in the case of a Zeeman spectrum in the presence of quadrupolar interactions. Exact solutions for the recovery of magnetization under the influence of purely magnetic fluctuations for I=12, 32, and 52 are presented. This is the general solution to a problem that has been previously solved only for the I=12 case. An important example for the application of this technique is 17O NMR in cuprate superconductors (I=52). We show comparisons of the theory with the relaxation measured for high-temperature superconducting materials and the NMR-rates measured by this technique across the vortex-broadened spectrum at low temperature.

Mitrovi?, V. F.; Sigmund, E. E.; Halperin, W. P.

2001-07-01

55

NMR assignment of brazilein  

Microsoft Academic Search

The 1H and 13C NMR signals of brazilein from Caesalpinia sappan were assigned by HMBC correlations and the physicochemical data investigated. © 1997 Published by Elsevier Science Ltd. All rights reserved

Seon Kim Dong; Baek Nam-In; Ryang Oh Sei; Young Jung Keun; Seon Lee Im; Lee Hyeong-Kyu

1997-01-01

56

Simultaneous PET and NMR.  

PubMed

There is currently great interest in combining data from different imaging modalities, either by image registration methods that are performed after the data has been acquired or using new devices that can acquire data from two modalities simultaneously, or near simultaneously. In this paper a small prototype NMR-compatible PET scanner capable of acquiring PET images simultaneously with either NMR images or NMR spectra is described. In an associated paper [1], Pamela Garlick describes some investigations of cardiac metabolism that have been made using this system. One of the main challenges in constructing an NMR-compatible PET scanner is that photomultiplier tubes, which are an essential element of nearly all current PET systems, will not function in a high magnetic field. In collaboration with Simon Cherry and the Crump Institute of Biomedical Imaging at UCLA Medical School, a small (5.4 cm diameter) NMR-compatible PET scanner that will operate within the bore of an NMR magnet has been developed. Long optical fibres are used to transport light from the scintillation crystals that form the detector head to photomultiplier tubes situated in a low magnetic field region several metres from the magnet. This system has been used to perform simultaneous PET and NMR spectroscopy measurements with a 9.4T spectroscopy system, and has also been used to obtain simultaneous PET and MR images in several MRI scanners including a 4.7T small bore animal imaging system. Current efforts in the development of this technology are directed at experimental studies on small animals, both because this is less demanding technically and because it is in this area that applications are likely to appear first. However, there is no reason in principle why human PET-MR would not be feasible. Below, work with the prototype system and the next stage in its development are described, and some of the future possibilities and challenges are discussed. PMID:12519736

Marsden, Paul K; Strul, Daniel; Keevil, Stephen F; Williams, Steven C R; Cash, Diana

2002-11-01

57

Trimethyl phosphite adsorbed on silica: An NMR and infrared study  

Microsoft Academic Search

Infrared spectroscopy and phosphorus-31 magic angle spinning nuclear magnetic resonance spectroscopy have been used to study the adsorption of trimethyl phosphite (TMP) on silica. At 23 C TMP reacts rapidly with surface silanol groups to give SiOCHâ as a chemisorbed product and liquid dimethyl phospite (DMP). However, formation of DMP ceases when about half of the SiOH groups have been

Ian D. Gay; A. J. McFarlan; B. A. Morrow

1991-01-01

58

(29)Si NMR in LC-NMR analysis of silicones.  

PubMed

It is demonstrated using a practical example that indirect detection of (29)Si NMR signals is sufficiently sensitive in LC-NMR stop-flow arrangement to analyze mixtures of siloxane polymers. New cryogenic probes with better signal-to-noise ratio will turn this version of LC-NMR into a routine method for analysis of siloxane polymers. PMID:16261506

Blechta, Vratislav; Sýkora, Jan; Hetflejs, Jirí; Sabata, Stanislav; Schraml, Jan

2006-01-01

59

Nuclear Magnetic Resonance (NMR) Guidelines.  

National Technical Information Service (NTIS)

Nuclear Magnetic Resonance (NMR) is a medical diagnostic imaging technique that applies the atomic principles of magnetic spin to visualize and analyze disease states in bodily tissues. NMR differs from the radiological devices in that (a) it does not uti...

R. Halpern

1983-01-01

60

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

61

2D NMR Metabonomic Analysis  

PubMed Central

Motivation Comparative metabolic profiling by nuclear magnetic resonance (NMR) is showing increasing promise for identifying inter-individual differences to drug response. Two dimensional (2D) 1H-13C NMR can reduce spectral overlap, a common problem of 1D 1H NMR. However, the peak alignment tools for 1D NMR spectra are not well suited for 2D NMR. An automated and statistically robust method for aligning 2D NMR peaks is required to enable comparative metabonomic analysis using 2D NMR. Results A novel statistical method was developed to align NMR peaks that represent the same chemical groups across multiple 2D NMR spectra. The degree of local pattern match among peaks in different spectra is assessed using a similarity measure, and a heuristic algorithm maximizes the similarity measure for peaks across the whole spectrum. This peak alignment method was used to align peaks in 2D NMR spectra of endogenous metabolites in liver extracts obtained from four inbred mouse strains in the study of acetaminophen-induced liver toxicity. This automated alignment method was validated by manual examination of the top fifty peaks as ranked by signal intensity. Manual inspection of 1872 peaks in 39 different spectra demonstrated that the automated algorithm correctly aligned 1810 (96.7%) peaks. Availability Algorithm is available upon request. Contact guochun.liao@roche.com

Zheng, Ming; Lu, Peng; Liu, Yanzhou; Pease, Joseph; Usuka, Jonathan; Liao, Guochun; Peltz, Gary

2007-01-01

62

Soils, Pores, and NMR  

NASA Astrophysics Data System (ADS)

Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 < 5 ms. Moreover, the dependence of the relaxation rate on magnetic field strength allows the identification of 2D diffusion at the interfaces as the mechanism which governs the relaxation process (Pohlmeier et al. 2009). T2 relaxation curves are frequently measured for the rapid characterization of soils by means of the CPMG echo train. Basically, they contain the same information about the pore systems like T1 curves, since mostly the overall relaxation is dominated by surface relaxivity and the surface/volume ratio of the pores. However, one must be aware that T2 relaxation is additionally affected by diffusion in internal gradients, and this can be overcome by using sufficiently short echo times and low magnetic fields (Stingaciu et al. 2009). Second, the logic continuation of conventional relaxation measurements is the 2-dimensional experiment, where prior to the final detection of the CPMG echo train an encoding period is applied. This can be T1-encoding by an inversion pulse, or T2 encoding by a sequence of 90 and 180° pulses. During the following evolution time the separately encoded signals can mix and this reveals information about the connectivity of the pore system. Examples are given for T1-T2 correlation of some soil samples (Haber-Pohlmeier et al. 2010). Third, relaxometric information forms the basis of understanding magnetic resonance imaging (MRI) results. The general difficulty of imaging in soils are the inherent fast T2 relaxation times due to i) the small pore sizes, ii) presence of paramagnetic ions in the solid matrix, and iii) diffusion in internal gradients. The last point is important, since echo times can not set shorter than about 1ms for imaging purposes. The way out is either the usage of low fields for imaging in soils or special ultra-short pulse sequences, which do not create echoes. In this presentation we will give examples on conventional imaging of macropore fluxes in soil cores (Haber-Pohlmeier et al. 2010), and the combination with relaxometric imaging, as well as the advantages and drawbacks of low-field and ultra-fast pulse imaging. Also first results on the imaging of soil columns measured by SIP in Project A3 are given. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Waterflow Monitored by Tracer Transport in Natural Porous Media Using MRI." Vadose Zone J.: submitted. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Relaxation in a Natural soil: Comparison of Relaxometric Imaging, T1 - T2 Correlation and Fast-Field Cycling NMR." The Open Magnetic Resonance Journal: in print. Pohlmeier, A., S. Haber-Pohlmeier, et al. (2009). "A Fast Field Cycling NMR Relaxometry Study of Natural Soils." Vadose Zone J. 8: 735-742. Stingaciu, L. R., A. Pohlmeier, et al. (2009). "Characterization of unsaturated porous media by high-field and low-field NMR relaxometry." Water Resources Research 45: W08412

Pohlmeier, Andreas; Haber-Pohlmeier, Sabina; Haber, Agnes; Sucre, Oscar; Stingaciu, Laura; Stapf, Siegfried; Blümich, Bernhard

2010-05-01

63

NMR in biology and medicine  

SciTech Connect

This volume explores the applications of NMR in basic biological research and in clinical diagnosis. The contributors highlight the capabilities of NMR as a tool for studying living organisms at the molecular and cellular levels and detecting abnormalities in various organ systems. Included are solid-state and high-resolution NMR studies of the molecular structure and dynamic interactions of lipids, proteins, and nucleic acids. The latest developments in NMR zeugmatographic imaging and in musculoskeletal and cardiovascular magnetic resonance imaging are detailed. Concluding chapters review the uses of in vivo NMR spectroscopy to study energy metabolism and cellular biochemistry. Emphasis is placed on in vivo NMR spectroscopy studies that elucidate normal metabolic functions and their pathological disturbances.

Chien, S.; Chien, H.

1986-01-01

64

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

65

NMR Studies of Disordered Solids  

NASA Astrophysics Data System (ADS)

In this contribution an introduction to dynamic solid state NMR spectroscopy is presented. The main emphasis is given to dynamic 2H NMR techniques, since these methods - in combination with selectively or partially deuterated compounds - have demonstrated a particular suitability for studying the molecular properties (i.e. order and dynamics) of solid, semisolid materials as well as anisotropic liquids. A general overview about the theoretical background of dynamic NMR spectroscopy is provided in the first part, which also includes the description of the main experimental methods in dynamic 2H NMR spectroscopy. In the second part representative results from model simulations are given, considering various types of motional processes which are frequently discussed in disordered materials. Applications of dynamic 2H NMR techniques during the study of inclusion compounds are shown in the last section.

Villanueva-Garibay, J.; Müller, K.

66

? NMR in zinc metal  

NASA Astrophysics Data System (ADS)

A high-precision observation of NMR in zinc metal at 295 K is reported. The 0953-8984/8/50/051/img2 nuclear quadrupole coupling 0953-8984/8/50/051/img3 and isotropic and axial components of the Knight shift (0953-8984/8/50/051/img4 and 0953-8984/8/50/051/img5) have been determined, as well as the temperature variation of 0953-8984/8/50/051/img6 and 0953-8984/8/50/051/img4 in a 283 K range around 295 K. The large positive value for the temperature coefficient of 0953-8984/8/50/051/img4 is comparable to that of cadmium, and a similar explanation appears likely. At 295 K the following values are obtained: 0953-8984/8/50/051/img9 MHz, 0953-8984/8/50/051/img10 and 0953-8984/8/50/051/img11.

Bastow, T. J.

1996-12-01

67

NMR Studies of Polymer Nanocomposites.  

National Technical Information Service (NTIS)

Methods developed and refined to characterize ion and molecular transport process in disordered media are described. The primary tool is pulsed field gradient NMR. A static field gradient method was developed which makes possible variable pressure diffusi...

S. G. Greenbaum

2001-01-01

68

Optical pumping and xenon NMR.  

National Technical Information Service (NTIS)

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 an...

M. D. Raftery

1991-01-01

69

Compact orthogonal NMR field sensor  

SciTech Connect

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

70

Polarization transfer NMR imaging  

DOEpatents

A nuclear magnetic resonance (NMR) image is obtained with spatial information modulated by chemical information. The modulation is obtained through polarization transfer from a first element representing the desired chemical, or functional, information, which is covalently bonded and spin-spin coupled with a second element effective to provide the imaging data. First and second rf pulses are provided at first and second frequencies for exciting the imaging and functional elements, with imaging gradients applied therebetween to spatially separate the nuclei response for imaging. The second rf pulse is applied at a time after the first pulse which is the inverse of the spin coupling constant to select the transfer element nuclei which are spin coupled to the functional element nuclei for imaging. In a particular application, compounds such as glucose, lactate, or lactose, can be labeled with .sup.13 C and metabolic processes involving the compounds can be imaged with the sensitivity of .sup.1 H and the selectivity of .sup.13 C.

Sillerud, Laurel O. (Los Alamos, NM); van Hulsteyn, David B. (Santa Fe, NM)

1990-01-01

71

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

72

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

73

NMR Relaxation and Petrophysical Properties  

NASA Astrophysics Data System (ADS)

NMR relaxation is routinely used in the field of geosciences to give basic petrophysical properties such as porosity, pore size distribution, saturation etc. In this tutorial, we focus on the pore size distribution deduced from NMR. We recall the basic principle used in the interpretation of the NMR signal and compare the results with other standard petrophysical techniques such as mercury pore size distribution, BET specific surface measurements, thin section visualizations. The NMR pore size distribution is a unique information available on water saturated porous media and can give similar results as MICP in certain situations. The scaling of NMR relaxation time distribution (s) into pore sizes (?m) requires the knowledge of the surface relaxivity (?m/s) and we recommend using specific surface measurements as an independent determination of solid surface areas. With usual surface relaxivities, the NMR technique can explore length-scales starting from nano-meters and ending around 100 ?m. Finally, we will introduce briefly recent techniques sensitive to the pore to pore diffusional exchange, providing new information on the connectivity of the pore network, but showing another possibility of discrepancy in the determination of pore size distribution with standard techniques.

Fleury, Marc

2011-03-01

74

"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

75

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...

76

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

77

NMR Of Small Platinum Particles.  

National Technical Information Service (NTIS)

exp 195 Pt NMR lineshapes as well as relaxation data are presented in three different samples of platinum metal particles (46%, 26%, and 15% dispersion) supported on alumina. The electronic properties of these particles are very much different from that o...

H. T. Stokes H. E. Rhodes P. K . Wang C. P. Slichter J. H. Sinfelt

1980-01-01

78

Nutation NMR Studies of Polyacetylene.  

National Technical Information Service (NTIS)

Using nutation NMR spectroscopy we have been able to determine directly the carbon-carbon bond lengths in polyacetylene. For trans-polyacetylene we find double and single bond lengths of 1.36 and 1.44 angstrons, respectively; the double bond in cis-polyac...

T. C. Clarke R. D. Kendrick C. S. Yannoni

1983-01-01

79

2H NMR Imaging of Strained Elastomers  

Microsoft Academic Search

One of the advantages of NMR imaging is the possibility of using the variety of NMR parameters for contrast formation. In this paper, the quadrupolar interaction of deuterated poly(butadiene) oligomers incorporated into elastic rubber bands was used to generate contrast in2H NMR images of stretched elastomers. The quadrupole splitting of the resonance was exploited to provide a quantitative characterization of

M. Klinkenberg; P. Blümler; B. Blümich

1996-01-01

80

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 a delineating the role of methyl group rotation in the proton NMR relaxation behavior of coals.

Zilm, K.W.

1992-05-27

81

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

82

A Role for NMR in Structural Genomics  

SciTech Connect

The 2nd EMSL Workshop on Structural Genomics was held on July 28th and 29th 2000 at the Environmental Molecular Sciences Laboratory at the Department of Energy?s Pacific Northwest National Laboratory in Richland, WA. The workshop focused on four topics: (1) The role for NMR in structural and functional genomics; (2) The technical challenges NMR faces for structural and functional genomics; (3) The potential need for a national NMR center for structural and functional genomics; and (4) Organization of the NMR community. This report summarizes the workshop proceedings and conclusions reached regarding the role of NMR in the emerging fields of structural and functional genomics.

Kennedy, Michael A.; Montelione, Gaetano; Arrowsmith, Cheryl H.; Markley, John L.

2002-08-01

83

Solution NMR of large molecules and assemblies†  

PubMed Central

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 the past 10 years, advances in NMR and isotope labeling methods have expanded the range of NMR-tractable targets by at least an order of magnitude. Here we briefly describe the methodological advances that allow NMR spectroscopy of large macromolecules and their complexes, and provide a perspective on the wide range of applications of NMR to biochemical problems.

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

2008-01-01

84

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

2013-08-22

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

Advanced NMR technology for bioscience and biotechnology  

SciTech Connect

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). NMR plays critical roles in bioscience and biotechnology in both imaging and structure determination. NMR is limited, however, by the inherent low sensitivity of the NMR experiment and the demands for spectral resolution required to study biomolecules. The authors addressed both of these issues by working on the development of NMR force microscopy for molecular imaging, and high field NMR with isotope labeling to overcome limitations in the size of biomolecules that can be studied using NMR. A novel rf coil design for NMR force microscopy was developed that increases the limits of sensitivity in magnetic resonance detection for imaging, and the authors demonstrated sub-surface spatial imaging capabilities. The authors also made advances in the miniaturization of two critical NMR force microscope components. They completed high field NMR and isotope labeling studies of a muscle protein complex which is responsible for regulating muscle contraction and is too large for study using conventional NMR approaches.

Hammel, P.C.; Hernandez, G.; Trewhella, J.; Unkefer, C.J. [Los Alamos National Lab., NM (US); Boumenthal, D.K. [Univ. of Utah, Salt Lake City, UT (US); Kennedy, M.A. [Pacific Northwest National Lab., Richland, WA (US); Moore, G.J. [Wayne State Univ., Detroit, MI (US)

1998-11-01

87

Determination of NMR interaction parameters from double rotation NMR.  

PubMed

It is shown that the anisotropic NMR parameters for half-integer quadrupolar nuclei can be determined using double rotation (DOR) NMR at a single magnetic field with comparable accuracy to multi-field static and MAS experiments. The (17)O nuclei in isotopically enriched l-alanine and OPPh(3) are used as illustrations. The anisotropic NMR parameters are obtained from spectral simulation of the DOR spinning sideband intensities using a computer program written with the GAMMA spin-simulation libraries. Contributions due to the quadrupolar interaction, chemical shift anisotropy, dipolar coupling and J coupling are included in the simulations. In l-alanine the oxygen chemical shift span is 455 +/- 20 ppm and 350 +/- 20 ppm for the O1 and O2 sites, respectively, and the Euler angles are determined to an accuracy of +/- 5-10 degrees . For cases where effects due to heteronuclear J and dipolar coupling are observed, it is possible to determine the angle between the internuclear vector and the principal axis of the electric field gradient (EFG). Thus, the orientation of the major components of both the EFG and chemical shift tensors (i.e., V(33) and delta(33)) in the molecular frame may be obtained from the relative intensity of the split DOR peaks. For OPPh(3) the principal axis of the (17)O EFG is found to be close to the O-P bond, and the (17)O-(31)P one-bond J coupling ((1)J(OP)=161 +/- 2 Hz) is determined to a much higher accuracy than previously. PMID:17707665

Hung, I; Wong, A; Howes, A P; Anupõld, T; Past, J; Samoson, A; Mo, X; Wu, G; Smith, M E; Brown, S P; Dupree, R

2007-08-03

88

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

89

Observation of NMR noise from solid samples  

PubMed Central

We demonstrate that proton NMR noise signals, i.e. NMR spectra without excitation by radio frequency, can be obtained from solid samples. Experimental results are shown for static and magic-angle spinning conditions. In addition, a tuning procedure based on the probes’ NMR noise characteristics and similar to the one described previously for liquids probes can also be used to optimize signal-to-noise ratios in 1H-MAS experiments.

Schlagnitweit, Judith; Dumez, Jean-Nicolas; Nausner, Martin; Jerschow, Alexej; Elena-Herrmann, Benedicte; Muller, Norbert

2010-01-01

90

Observation of NMR noise from solid samples.  

PubMed

We demonstrate that proton NMR noise signals, i.e. NMR spectra without excitation by radio frequency, can be obtained from solid samples. Experimental results are shown for static and magic-angle spinning conditions. In addition, a tuning procedure based on the probes' NMR noise characteristics and similar to the one described previously for liquids probes can also be used to optimize signal-to-noise ratios in ¹H-MAS experiments. PMID:20850362

Schlagnitweit, Judith; Dumez, Jean-Nicolas; Nausner, Martin; Jerschow, Alexej; Elena-Herrmann, Bénédicte; Müller, Norbert

2010-08-25

91

Phosphorus-31 MRI of cell membranes using quadratic echo line-narrowing  

NASA Astrophysics Data System (ADS)

Soft biological tissues have phosphorus concentrated in the membranes, metabolites, RNA and DNA of cells. This leads to a complicated, multi-peak ^31P nuclear magnetic resonance spectrum (including a broad membrane peak and narrow metabolite peaks), which precludes high-resolution ^31P MRI of soft tissues. This long-standing barrier has been overcome by a novel pulse sequence - the quadratic echo - recently discovered in fundamental quantum computation research. Applying time-dependent gradients in synch with a repeating pulse block enables a new route to high spatial resolution, three-dimensional ^31P MRI of the soft solid components of cells and tissues. This is a functionally different kind of MR image, since conventional ^1H MRI probes the intracellular and extracellular free water, whereas our ^31P MRI signal is dominated by the cell membrane contribution, which in turn depends on the density of mitochondria. The unique aspects of the signal should provide new insights into cellular and tissue function that compliment the information revealed by ^1H MRI. So far, various ex vivo soft tissue samples have been imaged with (sub-mm)^3 voxels. We will describe plans to enhance the spatial resolution in future work, to open a new window into cells.

Barrett, Sean; Frey, Merideth; Madri, Joseph; Michaud, Michael

2012-02-01

92

IDENTIFICATION OF SCYLLO-INOSITOL PHOSPHATES IN SOIL BY SOLUTION PHOSPHORUS-31 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY  

Technology Transfer Automated Retrieval System (TEKTRAN)

A large proportion of the organic P in soils can occur as scyllo-inositol phosphates. These compounds are rarely detected elsewhere in nature and remain poorly understood, partly because conventional procedures for their determination are lengthy and erroneous. We report a straightforward procedur...

93

Enantioselective outer-sphere complexation of lanthanide(III) tris (pyridine-2,6-dicarboxylate) chelates with vitamin B 12 derivatives. An NMR and CD study  

NASA Astrophysics Data System (ADS)

The binding of three corrinoids, cyanocobalarnin (vitamin B 12, CNCbl), aquacobalamin (vitamin B 12a, H 2OCbl +) and dicyanocobinamide ((CN) 2Cbi), collectively denoted by Q, to the ?- and ?-enantiomer of Ln(DPA) 33- complexes (Ln=lanthanide, DPA=2,6-pyridine dicarboxylate) in aqueous solution at room temperature is investigated by NMR and Circular Dichroism (CD) spectroscopy. Tb(DPA) 33- induces shifts of the 1H-NMR resonances of Q. A formula, describing the dipolar interaction between the proton spin and the paramagnetic moment of the lanthanide complex, is fitted to the lanthanide induced shifts, yielding the position of Tb(DPA) 33- and the orientation of its magnetic axis with respect to the corrinoid. The magnitude of the shifts provide the value of Kavg, an average of the association constants of the two diastereomeric complexes {?-Tb(DPA) 33-Q) and {?-Tb(DPA) 33-Q}. We find Kavg=4±0.5 (B 12) and 0.8±0.2 M -1 ((CN) 2Cbi). The value for H 2OCbl + depends strongly on the solution's ionic strength I: Kavg=(7±1)×10 1, 22±5 and 16±7 M -1 at I=0.007, 0.12 and 0.22 M, respectively. The addition of the corrinoids to a (racemic) solution of Nd(DPA) 33-, induces CD in the electronic Nd(III) transitions in the 700-800 nm region (ICD). This Pfeiffer effect is attributed to an excess of ?-Nd(DPA) 33- in the enantioselective, outer-sphere association with the corrinoids. From the magnitude of the ICD as a function of [Q], in conjunction with the (indirectly) determined CD effect of ?-Nd(DPA) 33-, values are determined for K?- K?. We find K?- K?=-24±2 M -1 for H 2OCbl + at pH 6.7 and I=0.12 M and -12±2 M -1 at I=0.22 M; -4.4±0.5 M -1 for CNCbl and -0.9±0.3 M -1 for (CN) 2Cbi. Adopting the view that in the lanthanide series Ln(DPA) 33- chelates are isostructural, the results of the NMR and CD experiments are combined to estimate the enantioselectivity in the binding Eb, defined as ( K?- K?)/2 Kavg. We find Eb=-0.5±0.2 for H 2OCbl +, -0.7±0.2 for CNCbl and -0.7±0.3 for (CN) 2Cbi. On the basis of the NMR data, a molecular structure is proposed for the two diastereomeric {Ln(DPA) 33-Q} complexes. The bonding involves hydrogen bonds between the amide proton on the a and g side chain of the corrinoid and the carboxylate oxygen of two DPA ligands.

Meskers, Stefan C. J.; Dekkers, Harry P. J. M.

1999-08-01

94

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

95

Reaction between trimethyl phosphite and dimethyl acetylenedicarboxylate in the presence of 5,5-dimethylcyclohexane-1,3-dione  

Microsoft Academic Search

Proton, carbon-13, and phosphorus-31 NMR spectroscopy and AM1 SCF MO calculations have been employed to investigate the molecular structure of the demethylated protonated adduct obtained from 1:1:1 addition reaction of the title compounds.

Issa Yavari; Ahmad Khorramabadi-Zad; Parviz Rashidi-Ranjbar; Hossain Fallah-Bagher-Shaidaii

1997-01-01

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

Access to NMR Spectroscopy for Two-Year College Students: The NMR Site at Trinity University  

ERIC Educational Resources Information Center

|Students at two-year colleges and small four-year colleges have often obtained their exposure to NMR spectroscopy through "canned" spectra because the cost of an NMR spectrometer, particularly a high-field spectrometer, is prohibitive in these environments. This article describes the design of a NMR site at Trinity University in which spectral…

Mills, Nancy S.; Shanklin, Michael

2011-01-01

98

Multiplex NMR: A novel methodology for high-throughput NMR analysis  

Microsoft Academic Search

In this thesis, multiplex NMR methodology is described, which has the potential to significantly increase the throughput of NMR measurements. This novel methodology has possible applications in areas where large numbers of samples need to be analyzed. Multiple-coil NMR probes have been constructed to analyze multiple samples simultaneously using parallel detecting microcoils that were incorporated into a single RF circuit.

Ting Hou

2002-01-01

99

The Corset Effect, Field-Cycling NMR Relaxometry, Transverse NMR Relaxation, Field-Gradient NMR Diffusometry, and Incoherent Neutron Scattering  

Microsoft Academic Search

The corset effect is an experimentally established dynamic confinement phenomenon first observed by field-cycling NMR relaxometry and transverse NMR relaxation in polymer melts in pores with dimensions ranging from a few nanometers up to 0.06 micrometers or even more. The techniques employed are specifically sensitive to rotational fluctuations of polymer segments. It will be shown that neutron scattering and other

Rainer Kimmich; Nail Fatkullin

2010-01-01

100

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

101

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

102

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

103

Solid-State NMR Studies of Bone  

Microsoft Academic Search

Solid-state NMR studies on bone, bone mineral standards and collagen are reviewed. NMR spectroscopy was mostly applied to the bone mineral and confirmed that the structure resembles that of calcium carbonatoapatite of type B. Apatite in bone was found to be deficient in structural hydroxyl groups. Concentration and distribution of hydrogenphosphate and carbonate ions, and of water in apatite crystals

Waclaw Kolodziejski

104

Using Cloud Storage for NMR Data Distribution  

ERIC Educational Resources Information Center

|An approach using Google Groups as method for distributing student-acquired NMR data has been implemented. We describe how to configure NMR spectrometer software so that data is uploaded to a laboratory section specific Google Group, thereby removing bottlenecks associated with printing and processing at the spectrometer workstation. Outside of…

Soulsby, David

2012-01-01

105

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

106

An NMR approach to structural proteomics  

Microsoft Academic Search

The influx of genomic sequence information has led to the concept of structural proteomics, the determination of protein structures on a genome-wide scale. Here we describe an approach to structural proteomics of small proteins using NMR spectroscopy. Over 500 small proteins from several organisms were cloned, expressed, purified, and evaluated by NMR. Although there was variability among proteomes, overall 20%

Adelinda Yee; Xiaoqing Chang; Antonio Pineda-Lucena; Bin Wu; Anthony Semsesi; Brian Le; Theresa A. Ramelot; Gregory M. Lee; Sudeepa Bhattacharyya; Pablo Gutierrez; Aleksej Denisov; Chang-Hun Lee; John R. Cort; Guennadi Kozlov; Jack Liao; Grzegorz Finak; Limin Chen; David Wishart; Weontae Lee; Lawrence P. McIntosh; Kalle Gehring; Michael A. Kennedy; Aled M. Edwards; Cheryl H. Arrowsmith

2002-01-01

107

NMR structural studies of membrane proteins  

Microsoft Academic Search

The three-dimensional structures of membrane proteins are essential for understanding their functions, interactions and architectures. Their requirement for lipids has hampered structure determination by conventional approaches. With optimized samples, it is possible to apply solution NMR methods to small membrane proteins in micelles; however, lipid bilayers are the definitive environment for membrane proteins and this requires solid-state NMR methods. Newly

Francesca M Marassi

1998-01-01

108

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

109

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

110

Inductive shielding of NMR phase noise  

Microsoft Academic Search

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.

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

2002-01-01

111

An NMR Approach to Structural Proteomics  

SciTech Connect

The influx of genomic sequence information has led to the concept of structural proteomics, the determination of protein structures on a genome-wide scale. Here we describe an approach to structural proteomics of small proteins using NMR spectroscopy. Over 500 small proteins from several from several organisms were cloned, expressed , purified and evaluated by NMR . Although there was variability among proteomes, overall 20% of these proteins were found to be readily amendable to NMR structure determination. NMR sample preparation was centralized in on facility , a distributive approach was used for NMR data collection and analysis. Twelve structures are reported here as part of this approach, which allowed us to infer putative functions for several conserved hypothetical proteins.

Yee, Adelinda; Chang, Xiaoqing; Pineda-Lucena, Antonio; Wu, Bin; Semsesi, Anthony; Le , Brian; Ramelot, Theresa A.; Lee, Gregory M.; Bhattacharyya, Sudeepa; Gutierrez, Pablo; Denisov, Aleksej; Lee, Chang-Hun; Cort, John R.; Kozlov, Guennadi; Liao, Jack; Finak, Grzegorz; Chen, Limin; Wishart, David; Lee, Weontae; Mclntosh, Lawrence P.; Gehring, Kalle; Kennedy, Michael A.; Edwards, Aled M.; Arrowsmith, Cheryl H.

2002-02-19

112

Topics in NMR polarization measurement  

NASA Astrophysics Data System (ADS)

Using a precise circuit theoretical treatment of the series Q-meter, analytical expressions are derived for the relationship between the experimental NMR signal and the RF susceptibility on one hand, and their integrals and the polarization on the other. These are used for the ab initio calculation of the signal-to-noise ratio for deuteron targets, which yield a realistic ultimate calibration precision of 0.1% at 1 K. The experimental signal distortions and drift are discussed, which lead to proposed optimized tuning and design rules, improved circuits, and new applications. Among these are the measurement of14 N polarization in irradiated NH3 targets, and the improvement of the temperature scale around 1 K by one order of magnitude.

Niinikoski, T. O.

1995-02-01

113

Electronics and instrumentation for NMR imaging  

SciTech Connect

The development of Nuclear Magnetic Resonance (NMR) imaging has brought together the experimental techniques of NMR spectroscopy and image processing with the consequence that new experimental requirements and apparatus are currently being developed. Examples of these requirements include the large amounts of data which can be generated and the effect on data processing and storage requirements. Also, the increased size of objects under investigation necessitate some major changes in the magnet and R.F. system. A discussion of these specific requirements is presented together with an overview of all components of the NMR imaging system.

Maudsley, A.A.; Hilal, S.K.; Simon, H.E.

1984-08-01

114

Scalar operators in solid-state NMR  

SciTech Connect

Selectivity and resolution of solid-state NMR spectra are determined by dispersion of local magnetic fields originating from relaxation effects and orientation-dependent resonant frequencies of spin nuclei. Theoretically, the orientation-dependent resonant frequencies can be represented by a set of irreducible tensors. Among these tensors, only zero rank tensors (scalar operators) are capable of providing high resolution NMR spectra. This thesis presents a series of new developments in high resolution solid-state NMR concerning the reconstruction of various scalar operators motion in solid C{sub 60} is analyzed.

Sun, Boqin

1991-11-01

115

NMR mechanisms in gel dosimetry  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance was critical to the development of gel dosimetry, as it established the potential for three dimensional dosimetry with chemical dosimeter systems through magnetic resonance imaging [1]. In the last two decades MRI has served as the gold standard for imaging, while NMR relaxometry has played an important role in the development and understanding of the behaviour of new gel dosimetry systems. Therefore, an appreciation of the relaxation mechanisms determining the NMR behaviour of irradiated gel dosimeters is important for a full comprehension of a considerable component of the literature on gel dosimetry. A number of excellent papers have presented this important theory, this brief review will highlight some of the salient points made previously [1-5]. The spin relaxation of gel dosimeters (which determines the dose dependence in most conventional MR imaging) is determined principally by the protons on water molecules in the system. These water protons exist in different environments, or groups (see Figure 1): on bulk water, on water hydrating the chemical species that are being modified under irradiation, and on water hydrating the gel matrix used to spatially stabilize the dosimeter (e.g., gelatin, agarose, etc). The spin relaxation depends on the inherent relaxation rate of each spin group, that is, on the relaxation rate which would be observed for the specific group if it were isolated. Also, the different water environments are not isolated from each other, and the observed relaxation rate also depends on the rate of exchange of magnetization between the groups, and on the fraction of protons in each group. In fact, the water exchanges quickly between the environments, so that relaxation is in what is usually termed the fast exchange regime. In the limit of fast exchange, the relaxation of the water protons is well characterized by a single exponential and hence by a single apparent relaxation rate. In irradiated gel dosimeters this observed rate is a function of the absorbed dose. In this review I will first develop the fast exchange model for the spin lattice relaxation Fricke gel dosimeter system, as this is conceptually the simpler system. Fundamental concepts such as relaxivity (which specifies the ability of some species to enhance the relaxation of water protons) and chemical yield will be presented. The linear dose relationship for Fricke gel dosimeters, and the reduced dose sensitivity of Fricke dosimeters containing chelators, will be explained. The model will then be extended to the spin-spin relaxation of polymer gel systems and the main differences discussed. The reasons for the enhanced dose sensitivy and dynamic range for spin-spin (R2) rather than spin-lattice (R1) relaxation will be presented.

Schreiner, L. J.

2009-05-01

116

Indicator dilution approach to NMR signal-flow curves  

Microsoft Academic Search

An indicator dilution model for the dependence of NMR signal on flow rate is presented. The model explains the enhancement in NMR signal observed at low flow rates and the reduction in NMR signal at high flow rate. It also produces an excellent fit to original NMR flow data, which are also presented.

M. D. Harpen

1985-01-01

117

NMR and optical studies of piezoelectric polymers  

SciTech Connect

Progress is reported in several areas dealing with piezoelectric (electroactive) polymers (mostly vinylidene fluoride, trifluoroethylene, copolymers, PVF[sub 2]) and liquid crystals. Optical studies, neutron scattering, NMR, thermal, theory and modeling were done.

Schmidt, V.H.; Tuthill, G.F.

1993-01-01

118

Single Crystal NMR of High Temperature Superconductors  

Microsoft Academic Search

The author reports Cu NMR studies of the high temperature superconductor YBa_2Cu _3O_{7-delta } (T_{rm c} = 90K) using a 1 mg single crystal. Three types of measurements have been made for both the \\

Charles Holloway Pennington

1989-01-01

119

Zero field NMR and NQR  

SciTech Connect

Methods are described and demonstrated for detecting the coherent evolution of nuclear spin observables in zero magnetic field with the full sensitivity of high field NMR. The principle motivation is to provide a means of obtaining solid state spectra of the magnetic dipole and electric quadrupole interactions of disordered systems without the line broadening associated with random orientation with respect to the applied magnetic field. Comparison is made to previous frequency domain and high field methods. A general density operator formalism is given for the experiments where the evolution period is initiated by a sudden switching to zero field and is terminated by a sudden restoration of the field. Analytical expressions for the signals are given for a variety of simple dipolar and quadrupolar systems and numerical simulations are reported for up to six coupled spin-1/2 nuclei. Experimental results are reported or reviewed for /sup 1/H, /sup 2/D, /sup 7/Li, /sup 13/C, and /sup 27/Al nuclei in a variety of polycrystalline materials. The effects of molecular motion and bodily sample rotation are described. Various extensions of the method are discussed, including demagnetized initial conditions and correlation by two-dimensional Fourier transformation of zero field spectra with themselves or with high field spectra.

Zax, D.B.; Bielecki, A.; Zilm, K.W.; Pines, A.; Weitekamp, D.P.

1985-11-15

120

NMR study of trialuminide intermetallics  

NASA Astrophysics Data System (ADS)

We present a systematic study of the DO22-structure trialuminide intermetallic alloys using 27Al NMR spectroscopy. The quadrupole splittings, Knight shifts, and spin-lattice relaxation times on Al3Ti, Al3V, Al3Nb, and Al3Ta have been identified. Knight-shift tensors were isolated by observation of quadrupole satellite lines and fitting to the central-transition powder patterns. The results are associated with the local electronic density of states for each crystallographic site. Universally small isotropic Knight shifts and long T1's are consistent with low Fermi-surface densities of states indicating the importance of Fermi-surface features for the phase stability of these alloys. Larger anisotropic Knight shifts occurring at aluminum site I indicate strong hybridization at this site, and the electric-field-gradient tensors confirm the strong ab plane bonding configuration. Local-moment magnetism is found in Al3V, yet electrically this material appears very similar to the other DO22 aluminides.

Lue, Chin-Shan; Chepin, Suchitra; Chepin, James; Ross, Joseph H., Jr.

1998-03-01

121

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

122

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

123

Nuclear magnetic dipole moments from NMR spectra  

Microsoft Academic Search

In the procedure applied to extract the magnetic dipole moments of bare nuclei from NMR spectra of molecules the shielding of nuclei by electrons has been often described in a very crude manner. We determine the moments for 13C, 14N, 15N, 17O, 19F, 31P and 33S using more accurate shielding constants. Our gas phase NMR data are next used to

Andrej Antusek; Karol Jackowski; Micha? Jaszu?ski; Wlodzimierz Makulski; Marcin Wilczek

2005-01-01

124

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

125

17O NMR and crystalline hydrates  

Microsoft Academic Search

17O NMR is complementary to 2H NMR for studies of hydrate structure and dynamics in solids, insofar as the quadrupole coupling parameters can be accurately determined. At a Larmor frequency of 34.2 MHz, the effects of a large 17O quadrupole coupling (e2qQh ? 7 MHz) on both the orientational dependence of the central transition resonance frequency and its observation by

Q. W. Zhang; H. M. Zhang; M. G. Usha; R. J. Wittebort

1996-01-01

126

NMR Detection with an Atomic Magnetometer  

Microsoft Academic Search

We demonstrate detection of NMR signals using a noncryogenic atomic magnetometer and describe several novel applications of this technique. A nuclear spin-precession signal from water is detected using a spin-exchange-relaxation-free potassium magnetometer. We also demonstrate detection of less than 1013 129Xe atoms whose NMR signal is enhanced by a factor of 540 due to Fermi-contact interaction with K atoms. The

I. M. Savukov; M. V. Romalis

2005-01-01

127

A microscale protein NMR sample screening pipeline.  

PubMed

As part of efforts to develop improved methods for NMR protein sample preparation and structure determination, the Northeast Structural Genomics Consortium (NESG) has implemented an NMR screening pipeline for protein target selection, construct optimization, and buffer optimization, incorporating efficient microscale NMR screening of proteins using a micro-cryoprobe. The process is feasible because the newest generation probe requires only small amounts of protein, typically 30-200 microg in 8-35 microl volume. Extensive automation has been made possible by the combination of database tools, mechanization of key process steps, and the use of a micro-cryoprobe that gives excellent data while requiring little optimization and manual setup. In this perspective, we describe the overall process used by the NESG for screening NMR samples as part of a sample optimization process, assessing optimal construct design and solution conditions, as well as for determining protein rotational correlation times in order to assess protein oligomerization states. Database infrastructure has been developed to allow for flexible implementation of new screening protocols and harvesting of the resulting output. The NESG micro NMR screening pipeline has also been used for detergent screening of membrane proteins. Descriptions of the individual steps in the NESG NMR sample design, production, and screening pipeline are presented in the format of a standard operating procedure. PMID:19915800

Rossi, Paolo; Swapna, G V T; Huang, Yuanpeng J; Aramini, James M; Anklin, Clemens; Conover, Kenith; Hamilton, Keith; Xiao, Rong; Acton, Thomas B; Ertekin, Asli; Everett, John K; Montelione, Gaetano T

2009-11-14

128

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

129

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

2013-03-07

130

NMR cyberinfrastructure: Web-based virtual file system for managing distributed NMR data  

Microsoft Academic Search

A key aspect of data cyberinfrastructure is the middleware for managing distributed scientific data with services for organizing, publishing and preserving data entities in a collaborative, data sharing environment. In this paper, we describe a virtual web-based file system for managing NMR (Nuclear Magnetic Resonance) data from multiple, distributed NMR spectrometers across the campus of UC San Diego. The environment

Choonhan Youn; Chaitan Baru; Anthony Mrse; Joseph M. O'Connor

2010-01-01

131

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

132

Use of NMR and NMR Prediction Software to Identify Components in Red Bull Energy Drinks  

ERIC Educational Resources Information Center

|A laboratory experiment designed as part of an upper-level undergraduate analytical chemistry course is described. Students investigate two popular soft drinks (Red Bull Energy Drink and sugar-free Red Bull Energy Drink) by NMR spectroscopy. With assistance of modern NMR prediction software they identify and quantify major components in each…

Simpson, Andre J.; Shirzadi, Azadeh; Burrow, Timothy E.; Dicks, Andrew P.; Lefebvre, Brent; Corrin, Tricia

2009-01-01

133

Single crystal NMR of high temperature superconductors  

SciTech Connect

Cu NMR studies of the high temperature superconductor YBa2Cu3O(7-delta) (T sub c = 90 K) using a 1 mg single crystal is reported. Three types of measurements were made for both the plane and chain Cu crystallographic sites and with the static magnetic field placed successively along each of the three crystal axes a, b, and c: nuclear magnetic resonance (NMR) lineshapes, spin-lattice relaxation, and transverse relaxation. From these measurements four NMR tensors are deduced: the magnetic shift tensor, the electric field gradient tensor, the spin-lattice relaxation rate tensor, and the transverse relaxation rate tensor. As a preliminary matter, the symmetries of the magnetic shift and electric field gradient tensors were used to assign the two families of NMR lines to their respective crystallographic sites. From an analysis of the electric field gradient tensors it is shown that both the plane and chain Cu have valences Cu(2+), giving a single hold in the Cu atomic d-shell. The spin-lattice relaxation rate and magnetic shift of the plane and chain Cu were analyzed; included were both analyses in which only normal state data were considered, and in which superconducting state measurements of magnetic shifts were considered as well. These analyses show that the plane Cu atom behaves very nearly as a local moment. The chain Cu is probably also in the local moment limit; however, its NMR properties are largely determined by its interaction with oxygen holes in the chain.

Pennington, C.H.

1989-01-01

134

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

135

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

136

A Bioreactor for In Cell Protein NMR  

PubMed Central

The inside of the cell is a complex environment that is difficult to simulate when studying proteins and other molecules in vitro. We have developed a device and system that provides a controlled environment for Nuclear Magnetic Resonance (NMR) experiments involving living cells. Our device comprises two main parts, an NMR detection region and a circulation system. The flow of medium from the bottom of the device pushes alginate encapsulated cells into the circulation chamber. In the chamber, the exchange of oxygen and nutrients occurs between the media and the encapsulated cells. When the media flow is stopped, the encapsulated cells fall back into the NMR detection region, and spectra can be acquired. We have utilized the bioreactor to study the expression of the natively disordered protein ?-synuclein, inside Escherichia coli cells.

Sharaf, Naima G.; Barnes, Christopher O.; Charlton, Lisa M.; Young, Gregory B.; Pielak, Gary J.

2009-01-01

137

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, fo/Q.

Kodibagkar, Vikram D.; Conradi, Mark S.

2000-05-01

138

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

139

Surface Area Measurements Using Polarized Xenon NMR  

NASA Astrophysics Data System (ADS)

We developed a new NMR technique to measure the surface area of xenon-soluble porous media such as compacted polyethylene granulates (used in filtering, wicking, etc.), packs of polymeric beads (used for molecular fractionation, including radio-immunoassay), and lung tissue. The large chemical shift of the 129Xe NMR frequency enables independent observation and manipulation of both the dissolved and gas phase xenon resonances. The measured short-time rate of xenon interphase exchange depends on the surface area of the interface between the dissolved and gas phases. The porosity and surface area of four porous polymer solids were measured with xenon interphase exchange NMR, in good agreement with independent measurements obtained by confocal microscopy.

Mair, R. W.; Hoffmann, D.; Walsworth, R. L.; Butler, J. P.; Patz, S.; Topulos, G. P.

2000-06-01

140

17O NMR Studies of Zeolites  

NASA Astrophysics Data System (ADS)

Multiple-quantum magic-angle spinning (MQMAS) and double rotation (DOR) techniques were applied in the fields of 17.6 T and 11.7 T to the study the 17O NMR of oxygen-17 enriched zeolites A, LSX and sodalite. In addition, some 29Si and 1H MAS NMR experiments were performed. Zeolites with the ratio Si/Al = 1 were chosen, in order to have an alternating distribution of silicon and aluminum atoms. A linear correlation between the isotropic value of the chemical shift and the Si-O-Al bond angle (taken from X-ray data) could be found for the zeolites A and LSX, but not for sodalites. Hydration of the zeolites causes a downfield 17O NMR chemical shift of about 8 ppm with respect to the dehydrated zeolites. Ion exchange of the hydrated zeolites generates stronger chemical shift effects. The increase of the basicity of the oxygen framework of the zeolite LSX is reflected by a downfield shift of ca. 10 ppm going from the lithium to the cesium form, and the substitution of sodium by thallium in the zeolite A causes a shift of 34 ppm for the O3 site. 17O DOR NMR spectra are superior to 17O 3QMAS NMR spectra, featuring a resolution increase by a factor of two and are about equal with respect to the sensitivity. The residual linewidths of the signals in the 17O DOR and 17O 5QMAS NMR spectra can be explained by a distribution of the Si-O-Al angles in the zeolites.

Freude, Dieter; Loeser, Thomas

141

Comparison of LC-NMR and conventional NMR for structure elucidation in drug metabolism studies.  

PubMed

Liquid chromatography-nuclear magnetic resonance (LC-NMR) has proven to be a useful technique for the structure elucidation of novel metabolites from pharmaceutical compounds. Proponents of LC-NMR tout the advantage of eliminating the step of a separate chromatographic isolation. However, the advantages of directly coupling NMR and HPLC instrumentation must be weighed against compromises in performance made to each technique to achieve a hyphenated system. While significant advances have been made in LC-NMR technology, a strong case can be made that HPLC purification of metabolites followed by conventional tube NMR is equally useful. It is relatively rare that one approach will be successful and the other not. The fundamental consideration is whether there is sufficient chromatographic expertise in the NMR laboratory to adequately design and execute appropriate experiments such that a pure chromatographic peak will be produced in the hyphenated system. Due to speed and sensitivity differences between NMR spectroscopy and mass spectrometry, liquid chromatography/mass spectrometry (LC/MS) continues to be the front-line approach for the structure elucidation of metabolites. PMID:18798699

Walker, Gregory S; O'Connell, Thomas N

2008-10-01

142

Correlations between in vivo tumor weight, oxygen pressure, 31P NMR spectroscopy, hypoxic microenvironment marking by ?-D-iodinated azomycin galactopyranoside (?-D-IAZGP), and radiation sensitivity  

Microsoft Academic Search

Purpose: The purpose of this study is to evaluate the amount of hypoxic fraction in a rodent tumor by means of polarographic oxygen electrode, phosphorus-31 magnetic resonance spectroscopy (31P-MRS), and a newly synthesized hypoxic marker, ?-D-iodinated azomycin galactopyranoside (?-D-IAZGP). We also investigated the radiosensitivity for tumors of different weights.Methods and Materials: Murine mammary carcinoma cells, FM3A, were subcutaneously implanted into

Jun-ichi Saitoh; Hideyuki Sakurai; Yoshiyuki Suzuki; Hiroyuki Muramatsu; Hitoshi Ishikawa; Yoshizumi Kitamoto; Tetsuo Akimoto; Masatoshi Hasegawa; Norio Mitsuhashi; Takashi Nakano

2002-01-01

143

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

144

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

145

Solution NMR study of integral membrane proteins.  

PubMed

Signals between a cell and its environment are often transmitted through membrane proteins; therefore, many membrane proteins, including G protein-coupled receptors (GPCRs) and ion channels, are important drug targets. Structural information about membrane proteins remains limited owing to challenges in protein expression, purification and the selection of membrane-mimicking systems that will retain protein structure and function. This review describes recent advances in solution NMR applied to the structural study of integral membrane proteins. The examples herein demonstrate that solution NMR spectroscopy will play a unique role not only in structural analysis, but also drug discovery of membrane proteins. PMID:21684799

Kang, CongBao; Li, Qingxin

2011-08-01

146

NMR Detection with an Atomic Magnetometer  

NASA Astrophysics Data System (ADS)

We demonstrate detection of NMR signals using a noncryogenic atomic magnetometer and describe several novel applications of this technique. A nuclear spin-precession signal from water is detected using a spin-exchange-relaxation-free potassium magnetometer. We also demonstrate detection of less than 1013 129Xe atoms whose NMR signal is enhanced by a factor of 540 due to Fermi-contact interaction with K atoms. The possibility of using a multichannel atomic magnetometer for fast 3D magnetic resonance imaging is also discussed.

Savukov, I. M.; Romalis, M. V.

2005-03-01

147

NMR detection with an atomic magnetometer.  

PubMed

We demonstrate detection of NMR signals using a noncryogenic atomic magnetometer and describe several novel applications of this technique. A nuclear spin-precession signal from water is detected using a spin-exchange-relaxation-free potassium magnetometer. We also demonstrate detection of less than 10(13) 129Xe atoms whose NMR signal is enhanced by a factor of 540 due to Fermi-contact interaction with K atoms. The possibility of using a multichannel atomic magnetometer for fast 3D magnetic resonance imaging is also discussed. PMID:15903914

Savukov, I M; Romalis, M V

2005-03-29

148

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

149

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

150

Advanced laboratory NMR spectrometer with applications  

NASA Astrophysics Data System (ADS)

A description is given of an inexpensive NMR spectrometer that is suitable for use in an advanced laboratory course. The application of this spectrometer to the measurement of the oil content in corn seeds and the role of polymerization are presented.

Biscegli, Clovis; Panepucci, Horacio; Farach, Horacio A.; Poole, Charles P.

1982-01-01

151

NMR Studies of Metallointercalator-DNA Interactions  

NASA Astrophysics Data System (ADS)

The study of the interaction between inert transition metal complexes and nucleic acids has developed from the early work of Dwyer [1], Lippard [2], Nordén [3] and Barton [4] to the point that it is now a central theme in bio-inorganic chemistry. While there has been considerable interest in metal complexes that bind nucleic acids, the interaction of metallointercalators with DNA and RNA has received the most attention [5, 6]. Square-planar platinum(II) complexes have demonstrated significant anticancer activity [7], and octahedral ruthenium(II) and rhodium(III) complexes have been used as probes of nucleic acid structure and as a means to study electron transfer reactions mediated by the heteroaromatic bases [5, 6]. While a range of techniques is available to study the nucleic acid binding of metal complexes, NMR spectroscopy (particularly 1H NMR) has proven to be the most useful. NMR spectroscopy can provide a detailed, atom level resolution, picture of the metal complex binding, and if the quality of the data is sufficient, a threedimensional structure of the metal complex bound to the oligonucleotide can be determined. The strategies used to assign the 1H NMR spectrum of an oligonucleotide [8-10], the extension of these methods to study the interaction of metal complexes with DNA and the use of molecular modelling will be presented in this chapter.

Buck, Damian P.; Collins, J. Grant

152

NMR Study of Aramid Model Compounds.  

National Technical Information Service (NTIS)

An NMR has been done on benzanilide, terephthalamide, isophthalamide, and their sodium and methylated derivatives. A data base of chemical shift values for aromatic carbons ipso, ortho, meta and para to C6H5CONH- and C6H5NCO-functional groups was generate...

L. J. Mathias M. Yoneyama W. L. Jarrett

1990-01-01

153

NMR measurements in solutions of dialkylimidazolium haloaluminates.  

National Technical Information Service (NTIS)

(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 dela...

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

1992-01-01

154

Protein NMR spectroscopy: Hydrogen bonds under pressure  

NASA Astrophysics Data System (ADS)

Hydrogen bonds play a key role in defining the folding of proteins and the maintenance of their structure. A high-pressure NMR study of ubiquitin now provides unprecedented detail on the temperature and pressure dependence of its hydrogen-bond network.

Nielsen, Gerd; Schwalbe, Harald

2012-09-01

155

Solid-state NMR imaging system  

DOEpatents

An accessory 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, N.; Dieckman, S.L.; Ellingson, W.A.

1990-12-31

156

NMR imaging: its potential clinical impact  

SciTech Connect

Nuclear magnetic resonance, a developing technique for visualizing soft tissue pathology that is inaccessible to any modality utilizing ionizing radiation, seems likely to eventually outdistance CT scanning in clinical usefulness. In the near future, NMR, now in its infancy, should complement CT scanning and be increasingly used in probing hematologic and metabolic processes.

Oldendorf, W.H.

1982-09-01

157

NMR and Mushrooms : imaging post harvest senescence  

Microsoft Academic Search

The objective of the study described in this thesis was to explore the potentials of NMR for the study of water relations in harvested mushrooms ( Agaricus bisporus ). Since harvested mushrooms tend to continue their growth after harvest, their morphogenesis is heavily influenced by the external climatic conditions. Their respirative resources as well as their internal water can not

H. C. W. Donker

1999-01-01

158

Some Exercises in Quantitative NMR Imaging.  

National Technical Information Service (NTIS)

The articles represented in this thesis result from a series of investigations that evaluate the potential of NMR imaging as a quantitative research tool. In the first article the possible use of proton spin-lattice relaxation time T sub 1 in tissue chara...

C. J. G. Bakker

1985-01-01

159

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

160

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

161

Tritiation methods and tritium NMR spectroscopy.  

National Technical Information Service (NTIS)

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)COO...

D. K. Jaiswal H. Morimoto M. Salijoughian P. G. Williams

1991-01-01

162

NMR applications to low porosity carbonate stones  

Microsoft Academic Search

The purpose of this paper is to investigate NMR applications to porous materials widely employed in artistic and historical monuments and largely studied in the Cultural Heritage conservation field. Carrara marble, Candoglia marble and travertine samples were studied and data from relaxation times measurements were compared. Very interesting results from treated samples are reported and explained under the structure related

M Alesiani; S Capuani; B Maraviglia

2003-01-01

163

Development of LC-13C NMR.  

National Technical Information Service (NTIS)

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 flo...

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

1986-01-01

164

Online NMR for monitoring biocatalysed reactions  

Microsoft Academic Search

Monitoring biocatalysed reactions and metabolic pathways using NMR spectroscopy is of growing interest. As a non-invasive analytical method providing simultaneous information about intracellular and extracellular constituents, it is superior to other analytical techniques and has a wide range of applications: kinetics and stoichiometrics of metabolic events, metabolic fluxes and enzyme activities can be detected in situ or after taking a

Hansjörg Weber; Lothar Brecker

2000-01-01

165

Mobile NMR: Measuring Pixels, Images, and Spectra  

NASA Astrophysics Data System (ADS)

The vision of bringing nuclear magnetic resonance out of the lab to the doctor's office, the chemical reactor, or the manufacturing site is becoming reality with the development of mobile NMR. Pioneered for well logging in the oil industry, the concept has been explored for materials testing in a more systematic way since the introduction of the NMR-MOUSE. This is a small, one-sided access NMR sensor which acquires the information of one pixel from a particular spot of a large object. As the sensor explores the stray-fields of a permanent magnet and an rf coil, the magnetic fields are inhomogeneous and the sensitive volume is limited to the region, where both fields are orthogonal and the Larmor frequency lies within the excitation bandwidth. By shaping the magnet and the coil geometries, the shape of the sensitive volume can be tailored to a thin slice or a larger volume a certain distance away from the sensor surface. In the first case, there is a strong field gradient in the depth direction, and in the second case, a homogeneous sweet spot of the field profile is desired. The first case is suitable for measuring high-resolution depth profiles, while the second case is suitable for chemical shift resolved spectroscopy and volume imaging. The basic concepts of open and closed mobile NMR sensors will be discussed along with applications from testing polymer products, cultural heritage, medical tissue, and rock cores.

Bluemich, Bernhard

2007-03-01

166

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

2013-03-21

167

17O NMR investigation of phosphite hydrolysis mechanisms.  

PubMed

The use of solution 17O NMR spectroscopy in verifying the mechanism of trialkyl phosphite hydrolysis is presented. Trimethyl phosphite was reacted with 17O-labeled H2O at different temperatures and two reactant concentrations, with the reaction being monitored by 17O NMR. Kinetic details elucidated from the NMR spectra are also discussed. PMID:18044801

McIntyre, Sarah K; Alam, Todd M

2007-12-01

168

Superoxygenated Water as an Experimental Sample for NMR Relaxometry  

ERIC Educational Resources Information Center

|The increase in NMR relaxation rates as a result of dissolved paramagnetic species on the sample of superoxygenated drinking water is demonstrated. It is concluded that oxygen content in NMR samples is an important issue and can give rise to various problems in the interpretation of both spectroscopic and NMR imaging or relaxation experiments.|

Nestle, Nikolaus; Dakkouri, Marwan; Rauscher, Hubert

2004-01-01

169

Ferromagnetic insulating state in manganites: 55Mn NMR study  

Microsoft Academic Search

55Mn NMR was used to study the ferromagnetic insulating state in four different manganites. In all cases the coexistence of two types of regions possessing different NMR spectra and nuclear-spin dynamics was found. In the ferromagnetic insulating clusters the hopping frequency fhop of the electron holes is slower comparing to the NMR frequency fres and two lines ascribed to 3+

M. M. Savosta; V. I. Kamenev; V. A. Borodin; P. Novák; M. Marysko; J. Hejtmánek; K. Dörr; M. Sahana; A. Shames

2003-01-01

170

The acquisition of multidimensional NMR spectra within a single scan  

Microsoft Academic Search

A scheme enabling the complete sampling of multidimensional NMR domains within a single continuous acquisition is introduced and exemplified. Provided that an analyte's signal is sufficiently strong, the acquisition time of multidimensional NMR experiments can thus be shortened by orders of magnitude. This could enable the characterization of transient events such as proteins folding, 2D NMR experiments on samples being

Lucio Frydman; Tali Scherf; Adonis Lupulescu

2002-01-01

171

Application of the NMR-MOUSE to food emulsions  

NASA Astrophysics Data System (ADS)

The application of the NMR-MObile Universal Surface Explorer (NMR-MOUSE) to study food systems is evaluated using oil-in-water emulsions, and the results are compared to those obtained using a conventional low-field NMR (LF-NMR) instrument. The NMR-MOUSE is a small and portable LF-NMR system with a one-sided magnet layout that is used to replace the conventional magnet and probe on a LF-NMR instrument. The high magnetic field gradients associated with the one-sided MOUSE magnet result in NMR signal decays being dominated by molecular diffusion effects, which makes it possible to discriminate between the NMR signals from oil and water. Different data acquisition parameters as well as different approaches to the analysis of the NMR data from a range of oil-in-water emulsions are evaluated, and it is demonstrated how the concentration of oil and water can be determined from the NMR-MOUSE signals. From these model systems it is concluded that the NMR-MOUSE has good potential for the quantitative analysis of intact food products.

Pedersen, H. T.; Ablett, S.; Martin, D. R.; Mallett, M. J. D.; Engelsen, S. B.

2003-11-01

172

Superoxygenated Water as an Experimental Sample for NMR Relaxometry  

ERIC Educational Resources Information Center

The increase in NMR relaxation rates as a result of dissolved paramagnetic species on the sample of superoxygenated drinking water is demonstrated. It is concluded that oxygen content in NMR samples is an important issue and can give rise to various problems in the interpretation of both spectroscopic and NMR imaging or relaxation experiments.

Nestle, Nikolaus; Dakkouri, Marwan; Rauscher, Hubert

2004-01-01

173

Two dimensional NMR and NMR relaxation studies on coal structure. Final report, September 13, 1994--January 31, 1995  

SciTech Connect

This research program focused on developing new solids nuclear magnetic resonance (NMR) techniques for improved analysis of coal structure. Most work has been concentrated on the development of spectral editing NMR methods for solids.

Zilm, K.W.

1995-10-01

174

High resolution 1H NMR of a lipid cubic phase using a solution NMR probe  

Microsoft Academic Search

The cubic mesophase formed by monoacylglycerols and water is an important medium for the in meso crystallogenesis of membrane proteins. To investigate molecular level lipid and additive interactions within the cubic phase, a method was developed for improving the resolution of 1H NMR spectra when using a conventional solution state NMR probe. Using this approach we obtained well-resolved J-coupling multiplets

E. Boyle-Roden; N. Hoefer; K. K. Dey; P. J. Grandinetti; M. Caffrey

2007-01-01

175

Simultaneous multinuclear NMR studies of brain metabolism  

SciTech Connect

The brain is a complex metabolic system with intricate interactions between the various metabolic pathways to provide the tight regulation necessary to maintain homeostasis. A major problem faced by investigators studying metabolic regulation in vivo, is the inability to noninvasively follow the evolution of changes in metabolite concentrations during imposed metabolic stress. The work described in this thesis develops in vivo NMR spectroscopy into a technique to simultaneously monitor levels of high energy phosphate metabolites, intracellular pH, lactate concentrations and ionic equilibria in a time resolved fashion, and applies this technique to study metabolic regulation in the brain. The basic technique involves frequency interleaved NMR data acquisition, allowing spectra from several nuclei to be acquired in the same time it would take to acquire a spectrum from a single nucleus. In order to permit such frequency time shared use of the NMR spectrometer, it is necessary to develop multiple tuned NMR probes, capable of operating at several different frequencies with high sensitivity. Probes using multiple-pole tuning networks and coupled tank circuits individually or in combination are described. Applications of double (/sup 31/P, /sup 1/H) and triple /sup 23/Na, /sup 1/H, /sup 31/P) nuclear NMR to study metabolic regulation in cat brain models of hypoxic ischemia and global seizure are described. The results are consistent with regulation of oxidative metabolism in the brain in vivo by the phosphorylation ratio, a potent regulator of in vitro mitochondrial function. Measurements of the brain buffering capacity and post isochemic lactate efflux are presented. A close correlation between the transmembrane Na/sup +/ gradient and the energy state is established.

Schnall, M.D.

1986-01-01

176

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

PubMed

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. PMID:18374613

Takeda, Kazuyuki

2008-02-29

177

NMR reveals novel mechanisms of protein activity regulation  

PubMed Central

NMR spectroscopy is one of the most powerful tools for the characterization of biomolecular systems. A unique aspect of NMR is its capacity to provide an integrated insight into both the structure and intrinsic dynamics of biomolecules. In addition, NMR can provide site-resolved information about the conformation entropy of binding, as well as about energetically excited conformational states. Recent advances have enabled the application of NMR for the characterization of supramolecular systems. A summary of mechanisms underpinning protein activity regulation revealed by the application of NMR spectroscopy in a number of biological systems studied in the lab is provided.

Kalodimos, Charalampos G

2011-01-01

178

[Solid-state NMR spectroscopy and its pharmaceutical use].  

PubMed

Liquid-state NMR spectroscopy has become an essential analytical tool in almost all fields of chemical research. However, the scope of NMR spectroscopy is not confined to the analysis of fluids. The progress in the investigation of solid samples is remarkably fast and solid-state NMR has developed to a high performance method. The majority of drug substances and products manufactured in the pharmaceutical industry are formulated in solid state, their analysis gains the increasing potential of solid-state NMR spectroscopy. The aim of this work is to survey the basics of solid-state NMR and to highlight some pharmaceutical applications focusing on polymorphism. PMID:20443364

Marosi, Attila; Szalay, Zsófia; Demeter, Adám

2010-01-01

179

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

180

Hyphenated HPLC-NMR and its applications in drug discovery.  

PubMed

Hyphenated HPLC-NMR is a fast growing technology, allowing rapid and detailed structural characterization of unknown mixtures. The technical aspects of the technology are reviewed on the basis of system configuration, operation, solvent suppression, HPLC and NMR optimization, and detection. The combined use of HPLC-NMR and HPLC-MS is also described and discussed. Various applications of HPLC-NMR and integrated HPLC-NMR-MS in drug discovery, especially in the separation and structure elucidation of drug impurities, reaction mixtures, degradation products, in vitro and in vivo metabolites, and combinatorial library samples, are illustrated. PMID:11002280

Peng, S X

2000-10-01

181

NMR CHARACTERIZATIONS OF PROPERTIES OF HETEROGENEOUS MEDIA  

SciTech Connect

A critical and long-standing need within the petroleum industry is the specification of suitable petrophysical properties for mathematical simulation of fluid flow in petroleum reservoirs (i.e., reservoir characterization). The development of accurate reservoir characterizations is extremely challenging. Property variations may be described on many scales, and the information available from measurements reflect different scales. In fact, experiments on laboratory core samples, well-log data, well-test data, and reservoir-production data all represent information potentially valuable to reservoir characterization, yet they all reflect information about spatial variations of properties at different scales. Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) provide enormous potential for developing new descriptions and understandings of heterogeneous media. NMR has the rare capability to probe permeable media non-invasively, with spatial resolution, and it provides unique information about molecular motions and interactions that are sensitive to morphology. NMR well-logging provides the best opportunity ever to resolve permeability distributions within petroleum reservoirs. We develop MRI methods to determine, for the first time, spatially resolved distributions of porosity and permeability within permeable media samples that approach the intrinsic scale: the finest resolution of these macroscopic properties possible. To our knowledge, this is the first time that the permeability is actually resolved at a scale smaller than the sample. In order to do this, we have developed a robust method to determine of relaxation distributions from NMR experiments and a novel implementation and analysis of MRI experiments to determine the amount of fluid corresponding to imaging regions, which are in turn used to determine porosity and saturation distributions. We have developed a novel MRI experiment to determine velocity distributions within flowing experiments, and developed methodology using that data to determine spatially resolved permeability distributions. We investigate the use of intrinsic properties for developing improved correlations for predicting permeability from NMR well-logging data and for obtaining more accurate estimates of multiphase flow properties--the relative permeability and capillary pressure--from displacement experiments. We demonstrate the use of MRI measurements of saturation and relaxation for prediction wetting-phase relative permeability for unstable experiments. Finally, we developed an improved method for determining surface relaxivity with NMR experiments, which can provide better descriptions of permeable media microstructures and improved correlations for permeability predictions.

C.T. Philip Chang; Changho Choi; Jeromy T. Hollenshead; Rudi Michalak; Jack Phan; Ramon Saavedra; John C. Slattery; Jinsoo Uh; Randi Valestrand; A. Ted Watson; Song Xue

2005-01-01

182

Applications of NMR to transport in random systems  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance is a powerful, non-invasive technique for studying transport in dense three-dimensional systems. We review NMR experiments on transport in random systems like fluid-filled porous media. Two classes of experiment have been carried out, magnetic resonance imaging (MRI) and pulsed-field gradient NMR (PFG-NMR). The MRI technique provides real-space images, while the PFG-NMR technique provides distributions of displacements averaged over the sample. We focus on applications of PFG-NMR to fluid motions in random porous media from our laboratory and elsewhere. When the fluid is convecting, PFG-NMR experiments yield information such as local and nonlocal dispersion coefficients. This technique is sensitive to very slow flows (~cm/day), relevant to geophysical applications. The emerging field of NMR applications to granular flows is briefly reviewed and preliminary PFG data for a vertically shaken granular system are presented.

Candela, D.; Ding, A.; Yang, X.

2000-04-01

183

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.

184

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

185

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

186

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

187

Single crystal NMR of high temperature superconductors  

Microsoft Academic Search

Cu NMR studies of the high temperature superconductor YBa2Cu3O(7-delta) (T sub c = 90 K) using a 1 mg single crystal is reported. Three types of measurements were made for both the plane and chain Cu crystallographic sites and with the static magnetic field placed successively along each of the three crystal axes a, b, and c: nuclear magnetic resonance

Charles Holloway Pennington

1989-01-01

188

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

189

Deuteron NMR relaxation rates in cerium deuterides  

Microsoft Academic Search

Nuclear magnetic resonance (NMR) measurements of the 2H spin-lattice and transverse relaxation rates, T-11 and T-12, have been made in a series of cerium deuterides, CeDx. Results are reported for 2.01<=x<=2.90 and temperatures 77 <=T<=573 K. Spin-lattice relaxation rates for 2H are compared to published rates for 1H and they are found to be in substantial agreement when 1H rates

A. Raizman; D. Zamir; R. M. Cotts

1985-01-01

190

Protein complexes studied by NMR spectroscopy  

Microsoft Academic Search

Recent advances in NMR methods now allow protein complexes to be studied in great detail in a wide range of solution conditions. Isotope-enrichment strategies, resonance-assignment approaches and structural-determination methods have evolved to the point where almost any type of complex involving proteins of reasonable size may be studied in a straigthforward way. A variety of isotope editing and filtering strategies

A Joshua Wand; S Walter Englander

1996-01-01

191

Origin of NMR shielding in fluorides  

NASA Astrophysics Data System (ADS)

In this work, we analyze in detail the relation between electronic structure and fluorine nuclear magnetic resonance (NMR) shielding in a series of solid state alkali fluorides (LiF, NaF, KF, RbF, and CsF). For that purpose, we use solid-state NMR calculations implemented in the density functional theory full potential wien2k code (APW+lo). Both measurements and calculations show that the NMR shielding varies across the series by approximately 200 ppm. We focus our discussion on an explanation of the origin of the observed trend, and we show that the variation is mainly determined by contributions from “semicore” metal-p and valence F-p bands. More specifically, the trend in fluorine shielding can be related to the small but significant change in the hybridization of these states. A second important ingredient determining the value of the shielding is the presence and position of metal-d states in the unoccupied part of the Kohn-Sham bands. Although the present analysis has been demonstrated for the 19F nucleus in alkali fluorides, the main results are more general and can explain similar trends observed in other solids and for other nuclei.

Laskowski, Robert; Blaha, Peter

2012-06-01

192

NMR Landscapes for Chemical Shift Prediction.  

PubMed

The ability to reliably predict NMR chemical shifts plays an important role in elucidating the structure of organic molecules. Additionally, an intriguing question is how the multitude of variable factors (structural, electronic, and environmental) correlate with the actual electromagnetic shielding effect that determines the chemical shift value. This work presents NMRscape as a new tool for understanding these correlations by constructing the landscape that describes the relationship between the chemical shift value and the moieties bonded to a molecular scaffold. The scaffold may be as small as a single atom probed by NMR or a larger molecular framework containing the probed atom. NMRscape operates with only a list of the chemical moieties bonded to the scaffold, without utilizing any potentially biasing chemometric descriptors. The corresponding chemical shift landscape is constructed based on fundamental physical principles, which makes NMRscape a credible chemical shift prediction and analysis tool. As an illustration, we demonstrate that NMRscape can predict (13)C chemical shifts with an accuracy exceeding the substituent chemical shift (SCS) increment, hierarchical organization of spherical environments (HOSE), and neural networks (NN), methods for three distinct families of molecules sharing a common scaffold structure with moieties placed at two variable sites. The constructed NMR landscapes confirmed known empirical rules relating chemical shift values to the variation of chemical moieties on a scaffold, as well as uncovered hitherto hidden relationships. The practical importance of NMRscape is discussed. PMID:22900681

Moore, Katharine W; Li, Richard; Pelczer, Istvan; Rabitz, Herschel

2012-08-29

193

Evaluation of the cardiovascular system using NMR.  

PubMed

The current status and suggestions of the future potential for nuclear magnetic resonance imaging of the cardiovascular system are described. With many of the potential applications, there is overlap with existing methods. For example, imaging of the left ventricle can be accomplished with either echocardiography or radionuclide techniques with adequate evaluation of the left ventricular function. At current costs these conventional techniques may provide a more cost-effective approach for morphologic and functional assessment of the cardiovascular system. For this type of imaging, the advantages of NMR include its excellent resolution, the inherent tissue contrast, the sensitivity to blood motion, the 3-dimensional measure, and the lack of ionizing radiation. Because of these, NMR could provide an important adjunct for evaluation of the cardiovascular system. However for NMR to achieve its full promise as a cardiovascular imaging technique, some of its unique potentials need to be developed. These include: the ability to reliably image at least the proximal coronary arteries, the ability to delineate regional myocardial blood flow distribution, the ability to evaluate regional metabolic activity such as high-energy phosphate metabolites, and the ability to characterize myocardial disease using proton T1 and T2 alterations. PMID:2424388

Reeves, R C; Evanochko, W T; Pohost, G M

1985-12-01

194

Nonclassical correlation in NMR quadrupolar systems  

SciTech Connect

The existence of quantum correlation (as revealed by quantum discord), other than entanglement and its role in quantum-information processing (QIP), is a current subject for discussion. In particular, it has been suggested that this nonclassical correlation may provide computational speedup for some quantum algorithms. In this regard, bulk nuclear magnetic resonance (NMR) has been successfully used as a test bench for many QIP implementations, although it has also been continuously criticized for not presenting entanglement in most of the systems used so far. In this paper, we report a theoretical and experimental study on the dynamics of quantum and classical correlations in an NMR quadrupolar system. We present a method for computing the correlations from experimental NMR deviation-density matrices and show that, given the action of the nuclear-spin environment, the relaxation produces a monotonic time decay in the correlations. Although the experimental realizations were performed in a specific quadrupolar system, the main results presented here can be applied to whichever system uses a deviation-density matrix formalism.

Soares-Pinto, D. O.; Auccaise, R.; Azevedo, E. R. de; Bonagamba, T. J. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Post Office Box 369, 13560-970 Sao Carlos, Sao Paulo (Brazil); Celeri, L. C.; Maziero, J.; Serra, R. M. [Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, R. Santa Adelia 166, 09210-170 Santo Andre, Sao Paulo (Brazil); Fanchini, F. F. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, Post Office Box 6165, 13083-970 Campinas, Sao Paulo (Brazil)

2010-06-15

195

NMR studies of protein structure and dynamics  

NASA Astrophysics Data System (ADS)

Recent advances in solution NMR spectroscopy have significantly extended the spectrum of problems that can now be addressed with this technology. In particular, studies of proteins with molecular weights on the order of 100 kDa are now possible at a level of detail that was previously reserved for much smaller systems. An example of the sort of information that is now accessible is provided in a study of malate synthase G, a 723 residue enzyme that has been a focal point of research efforts in my laboratory. Details of the labeling schemes that have been employed and optimal experiments for extraction of structural and dynamics information on this protein are described. NMR studies of protein dynamics, in principle, give insight into the relation between motion and function. A description of deuterium-based spin relaxation methods for the investigation of side chain dynamics is provided. Examples where millisecond (ms) time scale dynamics play an important role and where relaxation dispersion NMR spectroscopy has been particularly informative, including applications involving the membrane enzyme PagP and mutants of the Fyn SH3 domain that fold on a ms time scale, are presented.

Kay, Lewis E.

2005-04-01

196

NMR studies of protein structure and dynamics  

NASA Astrophysics Data System (ADS)

Recent advances in solution NMR spectroscopy have significantly extended the spectrum of problems that can now be addressed with this technology. In particular, studies of proteins with molecular weights on the order of 100 kDa are now possible at a level of detail that was previously reserved for much smaller systems. An example of the sort of information that is now accessible is provided in a study of malate synthase G, a 723 residue enzyme that has been a focal point of research efforts in my laboratory. Details of the labeling schemes that have been employed and optimal experiments for extraction of structural and dynamics information on this protein are described. NMR studies of protein dynamics, in principle, give insight into the relation between motion and function. A description of deuterium-based spin relaxation methods for the investigation of side chain dynamics is provided. Examples where millisecond (ms) time scale dynamics play an important role and where relaxation dispersion NMR spectroscopy has been particularly informative, including applications involving the membrane enzyme PagP and mutants of the Fyn SH3 domain that fold on a ms time scale, are presented.

Kay, Lewis E.

2011-12-01

197

NMR Studies of Alkali Fulleride Superconductors  

NASA Astrophysics Data System (ADS)

There has been much debate over the mechanism of superconductivity in the alkali fulleride superconductors A_3C_{60} (A = alkali metal). Some researchers think an exotic pairing mechanism, possibly involving an electronic interaction, is manifest in A_3C_{60 } where others believe that the more prosaic phonon-mediated interaction proposed in the theory of Bardeen, Cooper, and Schrieffer (the BCS theory) is appropriate. Also, if the framework of the BCS theory is indeed proper, there is the issue of identifying the relevant modes of the pairing phonons: either the intermolecular or intramolecular modes. This thesis explores these questions with the use of nuclear magnetic resonance (NMR). We find that the body of NMR data on A_3C_{60} are consistent within the weak coupling limit of BCS theory with a BCS gap parameter less than or equal to 2.0k_{B}T_{c} , suggesting that the intramolecular phonons are responsible for electron pairing in the superconducting state of A_3C_{60} . In addition, we use NMR to probe the normal state of A_3C_{60} and find that the electronic properties of A_3C_{60} are that of a normal metal with electron-electron interactions having minor importance.

Stenger, Victor Andrew

198

The Studies of 13C NMR Chemical Shifts and Induced Lanthanide Shift Reagent Cis-trans Isomerization of N-Cinamylidene-hexyl, t-butyl and Substituted Aryl-Amines  

Microsoft Academic Search

The Carbon-13 chemical shifts of N-Cinamylidenehexyl, t-butyl and sixteen substituted aryl amines were analysed. The lanthanide induced carbon-13 chemical shifts of the cis and trans of four N-cinamylidene substituted anilines were analysed. The spectra N-cinamylidene hexylamine showed only the trans form. The cis\\/trans ratio of N-cinamylidene aryl amines increased as the LSR concentration increased.

Jasim M. A. Al-Rawi; Layla M. N. Saleem

1991-01-01

199

Protein Structure Determination Using Protein Threading and Sparse NMR Data  

SciTech Connect

It is well known that the NMR method for protein structure determination applies to small proteins and that its effectiveness decreases very rapidly as the molecular weight increases beyond about 30 kD. We have recently developed a method for protein structure determination that can fully utilize partial NMR data as calculation constraints. The core of the method is a threading algorithm that guarantees to find a globally optimal alignment between a query sequence and a template structure, under distance constraints specified by NMR/NOE data. Our preliminary tests have demonstrated that a small number of NMR/NOE distance restraints can significantly improve threading performance in both fold recognition and threading-alignment accuracy, and can possibly extend threading's scope of applicability from structural homologs to structural analogs. An accurate backbone structure generated by NMR-constrained threading can then provide a significant amount of structural information, equivalent to that provided by the NMR method with many NMR/NOE restraints; and hence can greatly reduce the amount of NMR data typically required for accurate structure determination. Our preliminary study suggests that a small number of NMR/NOE restraints may suffice to determine adequately the all-atom structure when those restraints are incorporated in a procedure combining threading, modeling of loops and sidechains, and molecular dynamics simulation. Potentially, this new technique can expand NMR's capability to larger proteins.

Crawford, O.H.; Einstein, J.R.; Xu, D.; Xu, Y.

1999-11-14

200

Multiplexed NMR: An Automated CapNMR Dual-Sample Probe  

PubMed Central

A new generation of micro-scale, nuclear magnetic resonance (CapNMR™) probe technology employs two independent detection elements to accommodate two samples simultaneously. Each detection element in the Dual-Sample CapNMR Probe (DSP) delivers the same spectral resolution and S/N as in a CapNMR probe configured to accommodate one sample at a time. A high degree of electrical isolation allows the DSP to be used in a variety of data acquisition modes. Both samples are shimmed simultaneously to achieve high spectral resolution for simultaneous data acquisition, or alternatively, a flowcell-specific shim set is readily called via spectrometer subroutines to enable acquisition from one sample while the other is being loaded. An automation system accommodates loading of two samples via dual injection ports on an autosampler and two completely independent flowpaths leading to dedicated flowcells in the DSP probe.

Norcross, James A.; Milling, Craig T.; Olson, Dean L.; Xu, Duanxiang; Audrieth, Anthony; Albrecht, Robert; Ruan, Ke; Likos, John; Jones, Claude; Peck, Timothy L.

2010-01-01

201

Pore morphology of porous polymer particles probed by NMR relaxometry and NMR cryoporometry.  

PubMed

The pore size distribution (PSD) and pore connectivity (PC) within porous polymer particles are probed by combining NMR cryoporometry and NMR relaxometry (spin-spin relaxation). With water as a probe molecule, the constant K in the so-called Gibbs-Thompson equation and the surface relaxivity (rho2) were determined to be K = (420 +/- 50) KA and rho2 = (0.44 +/- 0.01) x 10(-6) ms(-1), respectively. Also, the thickness of the interface layer was estimated to be of the order of one monolayer of water molecules. A detailed analysis of the complete set of NMR data enabled the morphology or pore structure to be probed, and is thoroughly discussed in the text. PMID:16375427

Hansen, Eddy W; Fonnum, Geir; Weng, Ellen

2005-12-29

202

Anisotropy in Tendon Investigated in Vivo by a Portable NMR Scanner, the NMR-MOUSE  

NASA Astrophysics Data System (ADS)

Ordered tissue like tendon is known to exhibit the magic-angle phenomenon in magnetic resonance investigations. Due to the anisotropic structure the transverse relaxation time T2 depends on the orientation of the tendon in the magnetic field. In medical imaging, relaxation measurements of tendon orientation are restricted by the size of the object and the space available in the magnet. For humans, tendon orientation can only be varied within small limits. As a consequence, the magic-angle phenomenon may lead to a misjudgement of tendon condition. It is demonstrated that the NMR-MOUSE (mobile universal surface explorer), a hand-held NMR sensor, can be employed to investigate the anisotropy of T2 in Achilles tendon in vivo. The NMR-MOUSE provides a convenient tool for analyzing the correlation of T2 and the physical condition of tendon.

Haken, R.; Blümich, B.

2000-06-01

203

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

204

A 19F NMR Study of Enzyme Activity  

Microsoft Academic Search

This basic enzyme activity laboratory experiment demonstrates how 19F NMR can be used in biochemical studies and presents the advantages of 19F NMR over 1H NMR for studies of this nature. N-Trifluoroacetylglycine was selected as a commercially available model fluorine-tagged substrate that readily undergoes acylase I-catalyzed hydrolysis to produce trifluoroacetic acid and glycine. Progress of the reaction was monitored by

Keith E. Peterman; Kevin Lentz; Jeffery Duncan

1998-01-01

205

Diffusional Properties of Methanogenic Granular Sludge: 1H NMR Characterization  

Microsoft Academic Search

The diffusive properties of anaerobic methanogenic and sulfidogenic aggregates present in wastewater treatment bioreactors were studied using diffusion analysis by relaxation time-separated pulsed-field gradient nuclear magnetic resonance (NMR) spectroscopy and NMR imaging. NMR spectroscopy measurements were performed at 22°C with 10 ml of granular sludge at a magnetic field strength of 0.5 T (20 MHz resonance frequency for protons). Self-diffusion

Piet N. L. Lens; Rakel Gastesi; Frank Vergeldt; Adriaan C. van Aelst; Antonio G. Pisabarro; Henk Van As

2003-01-01

206

APSY-NMR with proteins: practical aspects and backbone assignment  

Microsoft Academic Search

Automated projection spectroscopy (APSY) is an NMR technique for the recording of discrete sets of projection spectra from\\u000a higher-dimensional NMR experiments, with automatic identification of the multidimensional chemical shift correlations by the\\u000a dedicated algorithm GAPRO. This paper presents technical details for optimizing the set-up and the analysis of APSY-NMR experiments\\u000a with proteins. Since experience so far indicates that the sensitivity

Sebastian Hiller; Gerhard Wider; Kurt Wüthrich

2008-01-01

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

(19)F NMR: a valuable tool for studying biological events.  

PubMed

With the spectacular advancement of NMR techniques and the flourishing of fluorine chemistry allowing the synthesis of various fluorinated molecules, (19)F NMR represents a compelling option for studying myriad biological events ranging from the structure and function of biomolecules, enzymatic mechanisms, and metabolic pathways, through to drug screening and discovery as well as medical imaging. In this tutorial review, we aim to provide readers with a brief overview of the recent applications of (19)F NMR in various areas relating to biological and biomedical research, together with a brief introduction of specific hardware improvements permitting the practical implementation of (19)F NMR. PMID:23864138

Chen, Han; Viel, Stéphane; Ziarelli, Fabio; Peng, Ling

2013-09-23

209

Probing spatial distribution of alignment by deuterium NMR imaging.  

PubMed

Deuterium NMR imaging was used to evaluate the spatial distribution of the degree of alignment in different types of alignment media by monitoring the deuterium quadrupolar splitting using spatially resolved NMR techniques in conventional liquid state NMR instruments. These images allow the unambiguous distinction of magnetic field and alignment inhomogeneities present in partially aligned samples, revealing the underlying reasons for linebroadening within an alignment medium that cannot be explained by the sole analysis of 1D (2)H NMR spectra. For example, alignment inhomogeneities due to broken gels or the presence of concentration gradients in liquid crystalline solutions are clearly detected by the imaging methods proposed in this work. PMID:23559417

Trigo-Mouriño, Pablo; Merle, Christian; Koos, Martin R M; Luy, Burkhard; Gil, Roberto R

2013-04-04

210

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

Microsoft Academic Search

Sediment characteristics influence the distribution and bioavailability of phosphorus (P) in rivers and lakes. The objectives\\u000a of this study were to identify P compounds in sediments collected from 15 sites along the Bronx River to get insights on nutrient\\u000a transport for management of highly variable and modified ecosystems such as the Bronx River. The nuclear magnetic resonance\\u000a spectra showed that

Jingyu Wang; Hari K. Pant

2010-01-01

211

Transport, Compartmentation, and Metabolism of Homoserine in Higher Plant Cells . Carbon13- and Phosphorus31Nuclear Magnetic Resonance Studies  

Microsoft Academic Search

The transport, compartmentation, and metabolism of homoserine was characterized in two strains of meristematic higher plant cells, the dicotyledonous sycamore (Acer pseudoplatanus) and the mono- cotyledonous weed Echinochloa colonum. Homoserine is an inter- mediate in the synthesis of the aspartate-derived amino acids me- thionine, threonine (Thr), and isoleucine. Using 13C-nuclear magnetic resonance, we showed that homoserine actively entered the cells

Serge Aubert; Gilles Curien; Richard Bligny; Elisabeth Gout; Roland Douce

1998-01-01

212

Measurement of intracellular pH and deoxyhemoglobin concentration in deoxygenated erythrocytes by phosphorus-31 nuclear magnetic resonance.  

PubMed

Deoxygenation of erythrocytes produced marked changes in their 31P nuclear magnetic resonance spectra in the superconducting spectrometer. Most significantly, all intracellular and extracellular phosphates underwent downfield shifts. In fully deoxygenated blood the extracellular phosphates showed downfield shifts that were dependent upon packed cell volume, when added pyrophosphate was used as a measure of extracellular chemical shift behavior. This effect on extracellular signals was attributed to the paramagnetic contribution of deoxyhemoglobin to the "bulk" magnetic susceptibility of the red cell suspension. Line broadening was observed in deoxygenated whole cell systems but not in hemolysates, as a result of paramagnetic susceptibility gradients across the cell membrane. The degree of downfield shift upon deoxygenation was of different magnitude for each intracellular phosphate [2-P of 2,3-diphosphoglycerate (2,3-DPG) greater than 3-P of 2,3-DPG greater than inorganic phosphate greater than ATP phosphates], independent of packed cell volume but dependent on the degree of deoxygenation of hemoglobin. When deoxygenation shift effects in adult cells were compared to those of cord blood cells containing 70% fetal hemoglobin, it was found that 45% of the 2,3-DPG shift effects were attributable to binding of that compound to hemoglobin. By use of a nonphysiologic phosphate analogue, methylphosphonate, as an internal reference, it was found that an increase in pH of deoxy cells contributed to the downfield shift of inorganic phosphate. In hemolysates, the methylphosphonate - inorganic phosphate chemical shift difference was found to be pH dependent, with a sensitivity of (-) 0.39 pH unit/ppm, independent of the hemoglobin oxygenation state. PMID:6509033

Labotka, R J

1984-11-01

213

Real-time holographic reconstruction of NMR images in Fresnel transform imaging technique  

Microsoft Academic Search

A method of real-time holographic reconstruction of Nuclear Magnetic Resonance (NMR) images by making a hologram directly from the NMR signal is described. Since the signal obtained in the NMR Fresnel transform technique is given by an equation similar to that of the Fresnel diffraction equation in light, holographic reconstruction of NMR images is possible by recording the NMR signal

Satoshi ITO; Yoshifumi YAMADA; Yoshitsugu KAMIMURA

1997-01-01

214

MULTIPLE-QUANTUM NMR IN SOLIDS  

SciTech Connect

Time domain multiple-quantum (MQ) nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for spectral simplification and for providing new information on molecular dynamics. In this thesis, applications of MQ NMR are presented and show distinctly the advantages of this method over the conventional single-quantum NMR. Chapter 1 introduces the spin Hamiltonians, the density matrix formalism and some basic concepts of MQ NMR spectroscopy. In chapter 2, {sup 14}N double-quantum coherence is observed with high sensitivity in isotropic solution, using only the magnetization of bound protons. Spin echoes are used to obtain the homogeneous double-quantum spectrum and to suppress a large H{sub 2}O solvent signal. Chapter 3 resolves the main difficulty in observing high MQ transitions in solids. Due to the profusion of spin transitions in a solid, individual lines are unresolved. Excitation and detection of high quantum transitions by normal schemes are thus difficult. To ensure that overlapping lines add constructively and thereby to enhance sensitivity, time-reversal pulse sequences are used to generate all lines in phase. Up to 22-quantum {sup 1}H absorption in solid adamantane is observed. A time dependence study shows an increase in spin correlations as the excitation time increased. In chapter 4, a statistical theory of MQ second moments is developed for coupled spins of spin I = 1/2. The model reveals that the ratio of the average dipolar coupling to the rms value largely determines the dependence of second moments on the number of quanta. The results of this model are checked against computer-calculated and experimental second moments, and show good agreement. A simple scheme is proposed in chapter 5 for sensitivity improvement in a MQ experiment. The scheme involves acquiring all of the signal energy available in the detection period by applying pulsed spinlocking and sampling between pulses. Using this technique on polycrystalline adamantane, a large increase in sensitivity is observed. Correlation of motion of two interacting methyl groups is the subject of chapter 6. This system serves as a model for the study of hindered internal motion. Because the spin system is small and the motions are well-defined, the calculations involved are tractable. Group theory appropriate for nonrigid molecules is used to treat the change in the Hamiltonian as the methyl groups transit from correlated to uncorrelated motion. Results show that the four-quantum order alone is sufficient to distinguish between the two motions.

Yen, Y-S.

1982-11-01

215

Applications of (7)Li NMR in biomedicine.  

PubMed

The applications of (7)Li NMR spectroscopy and imaging in biology and experimental medicine have been progressing steadily. The interest derives primarily from the clinical use of Li salts to treat mania and manic-depressive illness. One area of investigation is ionic transport across the cellular membrane and compartmentation, so as to elucidate the mechanism(s) of therapeutic action and toxicity in clinical practice. The second is the development of a noninvasive, in vivo analytical tool to measure brain Li concentrations in humans, both as an adjunct to treatment and as a mechanistic probe. Here we review progress to date in this area. PMID:10722969

Komoroski, R A

2000-02-01

216

NMR observation of Tau in Xenopus oocytes  

NASA Astrophysics Data System (ADS)

The observation by NMR spectroscopy of microinjected 15N-labelled proteins into Xenopus laevis oocytes might open the way to link structural and cellular biology. We show here that embedding the oocytes into a 20% Ficoll solution maintains their structural integrity over extended periods of time, allowing for the detection of nearly physiological protein concentrations. We use these novel conditions to study the neuronal Tau protein inside the oocytes. Spectral reproducibility and careful comparison of the spectra of Tau before and after cell homogenization is presented. When injecting Tau protein into immature oocytes, we show that both its microtubule association and different phosphorylation events can be detected.

Bodart, Jean-François; Wieruszeski, Jean-Michel; Amniai, Laziza; Leroy, Arnaud; Landrieu, Isabelle; Rousseau-Lescuyer, Arlette; Vilain, Jean-Pierre; Lippens, Guy

2008-06-01

217

CARON - Average RMSD of NMR structure ensembles  

PubMed Central

The NMR protein structures are often deposited in the Protein Data Bank as ensembles of models that agree with the experimental restraints. Information about stereochemical variability and the molecular flexibility can be obtained by systematic comparison of all models. Here we describe CARON, a software that allows the computation of the root-mean-square-distances between equivalent atoms and residues in all models and introduces these values into the occupancy and the B-factor fields of PDB-formatted files. This tool allows the user to both get a quantitative estimation of the conformational homogeneity of the models and to exploit this information in common computer graphics programs.

Sikic, Kresimir; Carugo, Oliviero

2009-01-01

218

NMR measurements in SSC dipole D00001  

SciTech Connect

The first 16.5 m long SSC dipole magnet (D00001) had its field intensity measured as a function of position with a custom made NMR magnetometer. A short description of the probe is presented. The data obtained (most of it near 2 T spaced apart by one inch) shows an average transfer function of 1.02830 T/KA with position dependent values deviating from the average by up to .00130 T/KA revealing contruction inhomogeneities that were measured with a sensitivity of 25 ppM.

Kuchnir, M.; Schmidt, E.E.; Hanft, R.W.; Strait, J.B.

1986-09-12

219

Influence of non-bonded parameters on the quality of NMR structures: A new force field for NMR structure calculation  

Microsoft Academic Search

The effects of different non-bonded parameters of force fields for NMR structure calculation on the quality of the resulting NMR solution structures were investigated using Interleukin 4 as a model system. NMR structure ensembles were calculated with an ab initio protocol using torsion angle dynamics. The calculations were repeated with five different non-bonded energy functions and parameters. The resulting ensembles were

J. P. Linge; M. Nilges

1999-01-01

220

The application of LC-NMR and LC-SPE-NMR to compositional studies of natural organic matter.  

PubMed

Non-living natural organic matter (NOM) is ubiquitous in the oceans, atmosphere, sediments, and soils, and represents the most abundant organic carbon reserves on earth. However, a large proportion is considered to be "molecularly uncharacterized" because the inherent complexity of NOM is problematic when applying conventional analytical techniques. This manuscript presents initial applications of LC-NMR (1H) and LC-SPE-NMR (1H) to the studies of NOM isolated from water and soil. LC-NMR is applied to dissolved natural organic matter (DNOM) collected from freshwater environments, and both LC-NMR and LC-SPE-NMR are applied to an alkaline soil extract. The polar and complex nature of the DNOM samples limits conventional reversed phase separation, which can be partially overcome with the use of an ion pair reagent, although such an approach further complicates the NMR detection. LC-SPE-NMR of the soil alkaline extract was encouraging, and specific components in the mixture could be assigned. This work demonstrates that it is both possible to separate and concentrate specific components in NOM such that NMR detection is possible. As NMR information will be critical in unraveling the novel and/or complex structures in NOM this represents a key analytical hurdle in this area. PMID:15565221

Simpson, Andre J; Tseng, Li-Hong; Simpson, Myrna J; Spraul, Manfred; Braumann, Ulrich; Kingery, William L; Kelleher, Brian P; Hayes, Michael H B

2004-10-15

221

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

PubMed

In this study, the hyphenation of LC-SPE-NMR-MS at 500 MHz 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 the SPE cartridge to the NMR flow probe using deuterated acetonitrile for initial NMR investigation, the fraction was revovered by flushing the sample out of the NMR probe head with nitrogen gas. On the recovered fraction, high resolution FT-ICR-MS measurements were conducted, giving exact mass information about the unknown metabolite. In addition, a cryogenic NMR micro probe head was used to enhance the sensitivity of the NMR measurement by a factor of 5 in order to run 2D experiments for structural elucidation of the unknown metabolite. The combination of both MS and NMR results, led unequivocally to the elucidation of the structure as the ether glucuronide of 3-methoxyparacetamol. PMID:15595667

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

2004-11-26

222

NMR-based diffusion pore imaging.  

PubMed

Nuclear magnetic resonance (NMR) diffusion experiments offer a unique opportunity to study boundaries restricting the diffusion process. In a recent Letter [Phys. Rev. Lett. 107, 048102 (2011)], we introduced the idea and concept that such diffusion experiments can be interpreted as NMR imaging experiments. Consequently, images of closed pores, in which the spins diffuse, can be acquired. In the work presented here, an in-depth description of the diffusion pore imaging technique is provided. Image artifacts due to gradient profiles of finite duration, field inhomogeneities, and surface relaxation are considered. Gradients of finite duration lead to image blurring and edge enhancement artifacts. Field inhomogeneities have benign effects on diffusion pore images, and surface relaxation can lead to a shrinkage and shift of the pore image. The relation between boundary structure and the imaginary part of the diffusion weighted signal is analyzed, and it is shown that information on pore coherence can be obtained without the need to measure the phase of the diffusion weighted signal. Moreover, it is shown that quite arbitrary gradient profiles can be used for diffusion pore imaging. The matrices required for numerical calculations are stated and provided as supplemental material. PMID:23005784

Laun, Frederik Bernd; Kuder, Tristan Anselm; Wetscherek, Andreas; Stieltjes, Bram; Semmler, Wolfhard

2012-08-07

223

NMR-based diffusion pore imaging  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) diffusion experiments offer a unique opportunity to study boundaries restricting the diffusion process. In a recent Letter [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.048102 107, 048102 (2011)], we introduced the idea and concept that such diffusion experiments can be interpreted as NMR imaging experiments. Consequently, images of closed pores, in which the spins diffuse, can be acquired. In the work presented here, an in-depth description of the diffusion pore imaging technique is provided. Image artifacts due to gradient profiles of finite duration, field inhomogeneities, and surface relaxation are considered. Gradients of finite duration lead to image blurring and edge enhancement artifacts. Field inhomogeneities have benign effects on diffusion pore images, and surface relaxation can lead to a shrinkage and shift of the pore image. The relation between boundary structure and the imaginary part of the diffusion weighted signal is analyzed, and it is shown that information on pore coherence can be obtained without the need to measure the phase of the diffusion weighted signal. Moreover, it is shown that quite arbitrary gradient profiles can be used for diffusion pore imaging. The matrices required for numerical calculations are stated and provided as supplemental material.

Laun, Frederik Bernd; Kuder, Tristan Anselm; Wetscherek, Andreas; Stieltjes, Bram; Semmler, Wolfhard

2012-08-01

224

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

2013-05-15

225

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

226

Algorithmic cooling and scalable NMR quantum computers  

NASA Astrophysics Data System (ADS)

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

2002-03-01

227

Dynamic NMR microscopy of chromatographic columns  

SciTech Connect

Pulsed magnetic field gradients encoded a discrete spatial and temporal motion of the molecules of a fluid percolating through the packed bed of a dynamic radial compression column for liquid chromatography. Two packing materials of porous, chemically bonded C18 silica were used; large irregularly shaped particles (55--105 {micro}m) and small spherical particles (6 {micro}m). By combining pulsed field gradient NMR and NMR imaging the distribution of the fluid dynamic displacement probability was determined quantitatively at each point of the static image space. The local axial dispersion coefficient, fluid velocity, and external porosity of the bed were also estimated. The resolution achieved was 250 {micro}m {times} 250 {micro}m {times} 2,500 {micro}m per voxel, corresponding to a 250 {micro}m {times} 250 {micro}m pixel in a 2.5-mm-thick slice. Irregularly shaped particles showed slight external porosity heterogeneities over the column cross section, causing a dramatic loss of performance. Spherically shaped particles offered a nearly planar distribution of the transport characteristics across the packed bed, making radial compression of the bed enhance the performance.

Tallarek, U.; Bayer, E. [Univ. of Tuebingen (Germany). Inst. of Organic Chemistry; Dusschoten, D. van; Scheenen, T.; Van As, H. [Wageningen Agricultural Univ. (Netherlands). Dept. of Molecular Physics]|[Wageningen NMR Center (Netherlands); Guiochon, G. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry]|[Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.; Neue, U.D. [Waters Corp., Milford, MA (United States)

1998-09-01

228

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

229

Methods for spatial localization in NMR  

SciTech Connect

Several unique coil configurations were developed that have applications in nuclear magnetic resonance. These include a number of designs appropriate for use as rf surface coils, and two configurations developed as NMR magnets. The magnetic field profiles were calculated for each of these designs, from which field strength and homogeneity information were obtained. The rf coil configurations modelled include the opposed loop, opposed half loop, bicycle wheel, opposed bicycle wheel, and semi-toroid. The opposed loop design was studied in detail in terms of the theoretical spatial sensitivity and selectivity it offers. A number of NMR experiments were performed to test the validity of these theoretical calculations. This configuration produces a field that is substantially reduced near the coil itself, compared with the field produced by a single loop surface coil, but that rises to a maximum along the coil axis yielding a somewhat homogeneous region that may be used to achieve a degree of spatial localization. Several comparison schemes are used to evaluate the relative advantages and disadvantages of both the single loop and the opposed loop coil. The opposed coil concept also has been applied to the design of magnets. The results of calculations on the homogeneity and field strength possible with an opposed solenoid magnet are presented.

Rath, A.R.

1985-01-01

230

CHARACTERIZATION OF METABOLITES IN SMALL FISH BIOFLUIDS AND TISSUES BY NMR SPECTROSCOPY  

EPA Science Inventory

Nuclear magnetic resonance (NMR) spectroscopy has been utilized for assessing ecotoxicity in small fish models by means of metabolomics. Two fundamental challenges of NMR-based metabolomics are the detection limit and characterization of metabolites (or NMR resonance assignments...

231

Absolute configuration of amino alcohols by 1H-NMR.  

PubMed

A general NMR spectroscopy protocol for determination of absolute configuration of 1,2-amino alcohols, that allows differentiation of the four possible stereoisomers by analysis of the 1H NMR spectra of their bis-MPA derivatives, is described. PMID:16358061

Leiro, Victoria; Freire, Félix; Quiñoá, Emilio; Riguera, Ricardo

2005-10-06

232

Functional groups identified by solid state 13C NMR spectroscopy  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

233

NMR Experiments on Topological Defects in (3)He Superfluids.  

National Technical Information Service (NTIS)

Contents: Introduction (Superfluids 3He-A and 3He-B, Rotating superfluid 3He); Experimental techniques using NMR (NMR in 3He); Topological objects in 3He-A (Vortices, Solitons, Vortex Sheet); Nucleation of Vortex lines in 3He-B (Vortex formation during ac...

V. Ruutu

1996-01-01

234

Force-Detection NMR Sensor in CMOS-MEMS.  

National Technical Information Service (NTIS)

Nuclear Magnetic Resonance (NMR) on micro-liter samples using the Force Detection NMR (FDNMR) method will enable mobile and embedded detection of many elements without a multi-tesla superconducting magnet. This report presents a FDNMR sensor which has the...

K. M. Frederick

2003-01-01

235

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

236

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

237

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

238

Nuclear magnetic resonance (NMR) studies of homeopathic solutions  

Microsoft Academic Search

The efficacy of homeopathy is controversial. Nuclear magnetic resonance (NMR) has been used to study homeopathic solutions, showing provocative results. We examined the reproducibility of one of the allegedly positive studies.1H NMR spectra were recorded for Sulphur D4, diluted and succussed up to D30 (called potentization) at two different frequencies (300 and 500 MHz). The Sulphur solution had been potentiated

S Aabel; S Fossheim; F Rise

2001-01-01

239

{sup 17}O NMR investigations of oxidative degradation in polymers  

SciTech Connect

We have initiated studies using both solution and solid state magic angle spinning {sup 17}O NMR for a series of oxidatively aged polymers. This short note reports the solution {sup 17}O NMR for oxidatively degraded polypropylene, ethylene-propylene-diene, polyisoprene, and nitrile rubber. Enriched O{sub 2} is used during the accelerated aging. 3 figs, 7 refs.

Alam, T.M.; Celina, M.; Assink, R.A.; Gillen, K.T.; Clough, R.L.

1996-12-31

240

Investigation of zeolites by solid state quadrapole NMR.  

National Technical Information Service (NTIS)

The subject of this thesis is the NMR investigation of zeolites. The nature and properties of zeolites are discussed. Some of the basic priniples of NMR techniques on quadrupole nuclei are presented. A special technique, namely a two-dimensional nutation ...

R. Janssen

1990-01-01

241

"Perfecting" WATERGATE: clean proton NMR spectra from aqueous solution.  

PubMed

A simple modification of the WATERGATE solvent suppression method greatly improves the quality of (1)H NMR spectra obtainable from samples in H(2)O. The new method allows (1)H signals to be measured even when close in chemical shift to the signal of water, as for example in the NMR spectra of carbohydrates. PMID:23192194

Adams, Ralph W; Holroyd, Chloe M; Aguilar, Juan A; Nilsson, Mathias; Morris, Gareth A

2012-11-28

242

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

243

HPLC-SPE-NMR in pharmaceutical development: capabilities and applications.  

PubMed

High-performance liquid chromatography-solid phase extraction-NMR spectroscopy (HPLC-SPE-NMR) has recently become commercially available and has been evaluated with regard to its applicability in a pharmaceutical environment. The addition of an automated SPE unit to an HPLC-NMR system for peak trapping results in an improved NMR signal-to-noise ratio (S/N) and also has other practical advantages. The trapping efficiency is shown to depend on compound polarity and is highest for compounds eluting late on reversed-phase HPLC systems. Multiple peak trapping further increases the S/N, again with the best results for less polar compounds. For polar compounds, multiple peak trapping resulted in no S/N gain as the amount of material retained on the SPE cartridge was equivalent to that from a single injection. When compared with conventional HPLC-NMR, a S/N gain of up to five-fold could be achieved for some compounds in a single trapping step. A major advantage of the technique is the independence of the chromatographic step from the NMR step, resulting in greater versatility than conventional HPLC-NMR in the HPLC solvents and NMR solvents that can be used. Practical applications from both drug metabolite and drug impurity identification are presented. PMID:16049946

Sandvoss, Martin; Bardsley, Ben; Beck, Tony L; Lee-Smith, Emma; North, Stephanie E; Moore, Peter J; Edwards, Andrew J; Smith, Richard J

2005-09-01

244

NOESY on neurotoxins: NMR and conformational assignments of picrotoxins.  

PubMed

Nuclear Overhauser effect spectroscopy (NOESY) gave full assignments of the 1H-NMR spectra of the picrotoxane neurotoxins tutin, hyenanchin, picrotoxinin and picrotin, as well as the solution conformations of these compounds, consistent with molecular modelling. Fully assigned 13C-NMR data are reported. PMID:11704965

Perry, N B; Aiyaz, M; Kerr, D S; Lake, R J; Leach, M T

245

Tritium isotope effects on carbon-13 NMR chemical shifts  

SciTech Connect

Deuterium isotope effects on carbon-13 NMR chemical shifts can be useful in making spectral assignments, and they are also interesting in their own right. The authors report here the first determination of tritium isotope effects on carbon-13 NMR spectra. 11 references, 2 tables.

Arrowsmith, C.H.; Baitzer, L.; Kresge, A.J.; Powell, M.F.; Tang, Y.S.

1986-03-19

246

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

247

NMR-Metabolic Methodology in the Study of GM Foods  

Technology Transfer Automated Retrieval System (TEKTRAN)

The 1H NMR methodology used in the study of genetically modified (GM) foodstuff is discussed. The study of transgenic lettuce (Lactuca sativa cv "Luxor") over-expressing the KNAT1 gene from Arabidopsis is presented as a novel study-case. The 1H NMR metabolic profiling was carried out. Twenty-two wat...

248

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

249

NMR of Redox Proteins of Plants, Yeasts and Photosynthetic Bacteria  

Microsoft Academic Search

NMR spectroscopy has evolved dramatically over the past 15 years, establishing a new, reliable methodology for studying biomacromolecules at atomic resolution. The three-dimensional structure and dynamics of a biomolecule or a biomolecular complex is only one of the main types of information available using NMR. The spectral assignment to the specific nuclei of a biostructure is a very precise reflection

Xavier Trivelli; Sandrine Bouillac; Pascale Tsan; Isabelle Krimm; Jean-Marc Lancelin

2004-01-01

250

CISA: Combined NMR Resonance Connectivity Information Determination and Sequential Assignment  

Microsoft Academic Search

A nearly complete sequential resonance assignment is a key factor leading to successful protein structure determination via NMR spectroscopy. Assuming the availability of a set of NMR spectral peak lists, most of the existing assignment algorithms first use the differences between chemical shift values for common nuclei across multiple spectra to provide the evidence that some pairs of peaks should

Xiang Wan; Guohui Lin

2007-01-01

251

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

252

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

253

Fast multidimensional NMR: radial sampling of evolution space  

NASA Astrophysics Data System (ADS)

Multidimensional NMR spectroscopy can be speeded up by limited radial sampling of the time-domain evolution data. The resulting frequency-domain projections are used to reconstruct the full NMR spectrum. New algorithms are proposed to suppress back-projection artifacts while retaining optimum sensitivity. The method is illustrated by experiments on the 900 MHz HNCO spectrum of a protein, HasA.

Kup?e, Eriks; Freeman, Ray

2005-04-01

254

Synthesis and NMR elucidation of novel pentacycloundecane-based peptides.  

PubMed

The synthesis and NMR elucidation of two novel pentacycloundecane (PCU)-based peptides are reported. The PCU cage amino acids were synthesised as racemates and the incorporation of the cage amino acid with (S)-natural amino acids produced diastereomeric peptides. The diastereomeric 'cage' peptides were separated using preparative HPLC and the NMR elucidation of these PCU containing peptides are reported for the first time. The (1)H and (13)C NMR spectra showed series of overlapping signals of the cage skeleton and that of the peptide, making it extremely difficult to resolve the structure using one-dimensional NMR techniques only. The use of two-dimensional NMR techniques proved to be a highly effective tool in overcoming this problem. PMID:20474021

Altaib, Mohamed S; Arvidsson, Per I; Govender, Thavendran; Maguire, Glenn E M; Makatini, Maya; Onajole, Oluseye K; Kruger, Hendrik G

2010-06-01

255

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

256

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

257

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

258

NMR study of cell wall structure changes  

SciTech Connect

Xylans in hardwoods and grasses are extensively acetylated. This study attempts to isolate and quantify the effect that these acetyl esters have in the resistance of plant cell wall polysaccharides to cellulolytic enzymes. First, the in vitro deacetylation using mild aqueous hydroxylamine followed by characterization and enzyme digestion gives direct evidence that these acetyl groups play an important role in cell wall's resistance. /sup 13/C CP/MAS NMR proves to be an invaluable tool in the solid state characterization of biomass samples. Xylans from oat spelts were re-acetylated to various degrees. These acetylated xylans were then used as substates in enzymatic digestions. The results concur with the in vitro work.

Dale, B.E. (Texas A and M Univ., College Station, TX (USA)); Schroeder, H.A.; Mitchell, D.J. (C.S.U., Ft. Collins, CO (US)); Grohmann, K. (SERI, Golden, CO (US))

1988-01-01

259

Force field refinement from NMR scalar couplings  

NASA Astrophysics Data System (ADS)

NMR observables contain valuable information about the protein dynamics sampling a high-dimensional potential energy surface. Depending on the observable, the dynamics is sensitive to different time-windows. Scalar coupling constants J reflect the pico- to nanosecond motions associated with the intermolecular hydrogen bond network. Including an explicit H-bond in the molecular mechanics with proton transfer (MMPT) potential allows us to reproduce experimentally determined J couplings to within 0.02 Hz at best for ubiquitin and protein G. This is based on taking account of the chemically changing environment by grouping the H-bonds into up to seven classes. However, grouping them into two classes already reduces the RMSD between computed and observed J couplings by almost 50%. Thus, using ensemble-averaged data with two classes of H-bonds leads to substantially improved scalar couplings from simulations with accurate force fields.

Huang, Jing; Meuwly, Markus

2012-03-01

260

Para-hydrogen perspectives in hyperpolarized NMR  

NASA Astrophysics Data System (ADS)

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.

Glöggler, Stefan; Colell, Johannes; Appelt, Stephan

2013-10-01

261

Velocity imaging by ex situ NMR  

NASA Astrophysics Data System (ADS)

A pulsed field gradient stimulated spin-echo NMR sequence is combined with imaging methods to spatially resolve velocity distributions and to measure 2D velocity maps ex situ. The implementation of these techniques in open sensors provides a powerful non-invasive tool to measure molecular displacement in a large number of applications inaccessible to conventional closed magnets. The method is implemented on an open tomograph that provides 3D spatial localization by combining slice selection in the presence of a uniform static magnetic field gradient along the depth direction with pulsed field gradients along the two lateral directions. Different pipe geometries are used to demonstrate that the sequence performs well even in the extremely inhomogeneous B0 and B1 fields of these sensors.

Perlo, J.; Casanova, F.; Blümich, B.

2005-04-01

262

NMR studies of molecules in liquid crystals and graphite. [NMR (nuclear magnetic resonance)  

SciTech Connect

NMR is a rich source of information about molecular structure in condensed phases. A particularly good example of this is magnetic dipole couplings between protons on partially-oriented molecules. These couplings are very sensitive to the distance between the coupled protons and to the orientation of their internuclear vector with respect to the applied magnetic field. This spatial dependence gives proton dipole couplings the potential to be excellent probes of molecular conformation and orientation. This potential is usually not realized, since couplings between protons on molecules which undergo rapid conformational changes are averaged over all molecular motions which occur. The couplings can provide detailed constraints on the time-averaged conformation of a molecule that can be used as a rigorous test of models for molecular interactions. NMR experiments to measure proton dipole couplings were performed on a series of n-alkanes (n-hexane through n-decane) dissolved in nematic liquid crystals. Computer modeling of the experimental NMR spectra was done using several different models for intermolecular interactions in these systems. The model of Photinos, et al. was best in describing the intermolecular interactions in these systems and can provide a statistical picture of the conformation and orientation of the alkane molecules in their partially-oriented environment. Order parameters and conformation distributions for the alkanes can be calculated from the modeling. The alkanes are found to have conformational distributions very much like those found in liquid alkanes. Proton NMR spectra of tetrahydrofuran (THF) intercalated in two graphite intercalation compounds were also measured. Computer simulations of these spectra provide a picture of THF in the constrained environments between the graphene layers where the THF is oriented at a particular angle, can translate and rotate freely, but does not appear to pseudorotate.

Rosen, M.E.

1992-01-01

263

Continuous-wave NMR imaging of solids.  

PubMed

Current pulsed nuclear magnetic resonance methods of imaging samples such as solids with short spin-spin relaxation times are restricted to use with T2 values longer than approximately 10 microseconds. In the present study a method of imaging ultra-short T2 samples using continuous- wave, swept-field NMR is presented that, in principle, will be able to overcome this restriction. The technique is identical to that used in continuous-wave electron paramagnetic resonance imaging of paramagnetic species and involves irradiating the sample continuously with a radiofrequency excitation in the presence of a strong stationary magnetic field gradient. When the main magnetic field is swept over a suitable range, the variation of the NMR absorption signal with applied magnetic field yields a one-dimensional projection of the object under study along the gradient direction. Two- or three-dimensional image data sets may be reconstructed from projections that are obtained by applying the gradient in different directions. Signal-to-noise ratio can be improved by modulating the magnetic field and employing a lock-in amplifier to recover signal variations at the audio modulation frequency. Preliminary experiments were performed using a 7 Tesla magnet and a 300 MHz continuous-wave radiofrequency bridge with lock-in detection. The apparatus is described and the results of pilot experiments that employed vulcanized rubber samples are presented. The ability of the technique to detect short T2 samples was demonstrated by the presence of a background signal from the Perspex former of the birdcage resonator used for signal reception. PMID:8774005

Lurie, D J; McCallum, S J; Hutchison, J M; Alecci, M

1996-03-01

264

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

265

NMR at cryogenic temperatures: A {sup 13}C NMR study of ferrocene  

SciTech Connect

A new cryogenic apparatus is described that can be used to obtain NMR spectra at temperatures down to 8--10 K. The static solid {sup 13}C NMR spectrum of ferrocene is recorded at that temperature. Spectra recorded at higher temperatures show that ferrocene is still freely rotating about its 5-fold symmetry axis on the {sup 13}C NMR time scale at 45--50 K. A comparison of the principal values of the {sup 13}C chemical-shift tensor obtained from the room- and low-temperature spectra of ferrocene indicates that the lowest frequency chemical shift principal component, {delta}{sub 33}, is tilted off this symmetry axis by approximately 12{degree}. Quantum chemical calculations of the chemical-shift tensor, completed on structures of ferrocene from the literature as well as on optimized structures with the cyclopentadienyl rings locked in both the staggered and eclipsed arrangements, predict the angle between the {delta}{sub 33} direction and the rotation axis to be between 11 and 15{degree}, depending upon the geometry used in the calculation. The calculations also predict the sign of the angular perturbation, information not obtained from the experiment. An explanation of this angular change in the {delta}{sub 33} direction is provided by the composition of the molecular orbitals.

Orendt, A.M.; Facelli, J.C.; Jiang, Y.J.; Grant, D.M. [Univ. of Utah, Salt Lake City, UT (United States)

1998-09-24

266

ImatraNMR: Novel software for batch integration and analysis of quantitative NMR spectra  

NASA Astrophysics Data System (ADS)

Quantitative NMR spectroscopy is a useful and important tool for analysis of various mixtures. Recently, in addition of traditional quantitative 1D 1H and 13C NMR methods, a variety of pulse sequences aimed for quantitative or semiquantitative analysis have been developed. To obtain actual usable results from quantitative spectra, they must be processed and analyzed with suitable software. Currently, there are many processing packages available from spectrometer manufacturers and third party developers, and most of them are capable of analyzing and integration of quantitative spectra. However, they are mainly aimed for processing single or few spectra, and are slow and difficult to use when large numbers of spectra and signals are being analyzed, even when using pre-saved integration areas or custom scripting features. In this article, we present a novel software, ImatraNMR, designed for batch analysis of quantitative spectra. In addition to capability of analyzing large number of spectra, it provides results in text and CSV formats, allowing further data-analysis using spreadsheet programs or general analysis programs, such as Matlab. The software is written with Java, and thus it should run in any platform capable of providing Java Runtime Environment version 1.6 or newer, however, currently it has only been tested with Windows and Linux (Ubuntu 10.04). The software is free for non-commercial use, and is provided with source code upon request.

Mäkelä, A. V.; Heikkilä, O.; Kilpeläinen, I.; Heikkinen, S.

2011-08-01

267

Interactions between cations and peat organic matter monitored with NMR wideline, static and FFC NMR relaxometry  

NASA Astrophysics Data System (ADS)

The molecular size of humic substances is still under debate and is believed to range up to several hundred thousands Dalton, although a number of recent studies suggest much lower molecular weights. Nowadays an increasing number of authors suggest a model of molecular aggregates. One explanation why results on the molecular mass of humic materials are contradictory, may be that individual OM molecules are linked via intermolecular interactions, by bridges of water molecules or by cations bridging cation exchange sites (Schaumann, 2006a, b). Properties of such cross-linked systems can be similar to macromolecular systems revealing covalent cross-links. In this context, multivalent cations play an important ecological role, serving as reversible cross-linking agent. Formation and disruption of such cation bridges may close or open sorption sites in soil organic matter. Although cross-linking by multivalent cations has been proposed in many studies, the cross-linking effect has not yet been demonstrated on the molecular scale. The objective of this study was to investigate the interactions between cations and peat organic matter using NMR wideline techniques as well as static and fast field cycling (FFC) NMR relaxometry. Peat treated with solutions containing either Na+, Ca2+ or Al3+ was investigated in air-dried state for longitudinal relaxation times (T1) and NMR wideline characteristics. T1 distributions were separated into two Gaussian functions which were interpreted to represent two proton populations belonging to two environments of differing mobility. The relaxation rates (R1 = T1-1) in the cation treated samples spread over a range of 87-123 s-1 (R1a: fast component) and 32-42 s-1 (R1b: slow component). The rates in all treatments are significantly different from each other. and decrease in the order conditioned sample > desalinated sample > Na-treated sample. The treatment with multivalent cations affects R1a and R1b in different ways and needs more detailed explanation. Wideline proton NMR spectra can be used to quantify proton containing material, mainly water, based on their mobility. Spectra were decomposed into a Gaussian and Lorentzian line and changes to mobility after heat treatment indicate the water binding strength. In this study, differences in the various NMR parameters on the cation treatments will be presented and discussed with respect to the crosslinking hypothesis.

Schaumann, Gabriele E.; Conte, Pellegrino; Jäger, Alexander; Alonzo, Giuseppe; Bertmer, Marko

2010-05-01

268

Benchmarking NMR experiments: A relational database of protein pulse sequences  

NASA Astrophysics Data System (ADS)

Systematic benchmarking of multi-dimensional protein NMR experiments is a critical prerequisite for optimal allocation of NMR resources for structural analysis of challenging proteins, e.g. large proteins with limited solubility or proteins prone to aggregation. We propose a set of benchmarking parameters for essential protein NMR experiments organized into a lightweight (single XML file) relational database (RDB), which includes all the necessary auxiliaries (waveforms, decoupling sequences, calibration tables, setup algorithms and an RDB management system). The database is interfaced to the Spinach library (http://spindynamics.org), which enables accurate simulation and benchmarking of NMR experiments on large spin systems. A key feature is the ability to use a single user-specified spin system to simulate the majority of deposited solution state NMR experiments, thus providing the (hitherto unavailable) unified framework for pulse sequence evaluation. This development enables predicting relative sensitivity of deposited implementations of NMR experiments, thus providing a basis for comparison, optimization and, eventually, automation of NMR analysis. The benchmarking is demonstrated with two proteins, of 170 amino acids I domain of ?X?2 Integrin and 440 amino acids NS3 helicase.

Senthamarai, Russell R. P.; Kuprov, Ilya; Pervushin, Konstantin

2010-03-01

269

Mössbauer and NMR study of novel Tin(IV)-lactames  

NASA Astrophysics Data System (ADS)

N-tributylstannylated 2-pyrrolidinone was reacted with tributyltin triflate in different molar ratios and the complex formation monitored using 1H-NMR, 13C-NMR and 119Sn Mössbauer spectroscopy. Comparing the carbon NMR and tin Mössbauer results, a reaction scheme is suggested for the complexation which assumes the formation of a simultaneously O- and N-tributylstannylated pyrrolidinone cation. The formation of the only O-stannylated pyrrolidinone is also assumed to account for the non-constant Mössbauer parameters of the two tin environments in the distannylated pyrrolidinone cation when the ratio of tributyltin triflate is increased in the reaction.

Kuzmann, Erno; Szalay, Roland; Homonnay, Zoltan; Nagy, Sandor

2012-03-01

270

TOPICAL REVIEW: Hyperpolarized xenon in NMR and MRI  

NASA Astrophysics Data System (ADS)

Hyperpolarized gases have found a steadily increasing range of applications in nuclear magnetic resonance (NMR) and NMR imaging (MRI). They can be regarded as a new class of MR contrast agent or as a way of greatly enhancing the temporal resolution of the measurement of processes relevant to areas as diverse as materials science and biomedicine. We concentrate on the properties and applications of hyperpolarized xenon. This review discusses the physics of producing hyperpolarization, the NMR-relevant properties of 129Xe, specific MRI methods for hyperpolarized gases, applications of xenon to biology and medicine, polarization transfer to other nuclear species and low-field imaging.

Oros, Ana-Maria; Shah, N. Jon

2004-10-01

271

NMR Diffraction and Spatial Statistics of Stationary Systems  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) spatial imaging data may be acquired, processed, and interpreted in ways that provide information directly analogous to diffraction experiments, with length scales determined by gradient strengths rather than radiation wavelengths. This approach, originally considered by Mansfield nearly two decades ago, provides access to autocorrelations of sample density that statistically characterize small-scale density variations. These NMR "Patterson functions" can be acquired orders of magnitude more rapidly than comparably resolved NMR images and are suitable for spatial characterization of small features in bulk samples, such as morphology in structural materials. Unlike hindered diffusion approaches, neither mobility, penetrants, nor transport time are required for examining granularity and porosity.

Barrall, G. A.; Frydman, L.; Chingas, G. C.

1992-02-01

272

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

273

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

274

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

275

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

276

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

277

Characterisation of triacetone triperoxide (TATP) conformers using LC-NMR.  

PubMed

Previous studies [1,2] have reported the existence of two conformers of TATP. This study demonstrates the ability of LC-NMR to separate and characterise the individual conformers. The NMR data is consistent with the proposed structures for the two conformers. Re-equilibration can be followed by NMR and the kinetics of the process studied. Over the past decade the use of the explosive TATP in terrorist devices has increased. Therefore, the ability to analyse and characterise this material has assumed greater importance. PMID:21605825

Haroune, Nicolas; Crowson, Andrew; Campbell, Bill

2010-10-16

278

NMR studies of metallic tin confined within porous matrices  

SciTech Connect

{sup 119}Sn NMR studies were carried out for metallic tin confined within synthetic opal and porous glass. Tin was embedded into nanoporous matrices in the melted state under pressure. The Knight shift for liquid confined tin was found to decrease with decreasing pore size. Correlations between NMR line shapes, Knight shift, and pore filling were observed. The melting and freezing phase transitions of tin under confinement were studied through temperature dependences of NMR signals upon warming and cooling. Melting of tin within the opal matrix agreed well with the liquid skin model suggested for small isolated particles. The influence of the pore filling on the melting process was shown.

Charnaya, E. V. [Department of Physics, National Cheng Kung University, Tainan, 70101 Taiwan (China); Institute of Physics, St. Petersburg State University, St. Petersburg, Petrodvorets 198504 (Russian Federation); Tien, Cheng; Lee, M. K. [Department of Physics, National Cheng Kung University, Tainan, 70101 Taiwan (China); Kumzerov, Yu. A. [A. F. Ioffe Physico-Technical Institute, RAS, St. Petersburg 194021 (Russian Federation)

2007-04-01

279

Biodegradation pathway of mesotrione: complementarities of NMR, LC-NMR and LC-MS for qualitative and quantitative metabolic profiling.  

PubMed

Enhanced knowledge of pesticide transformation products formed in the environment could lead to both accurate estimates of the overall effects of these compounds on environmental ecosystems and human health and improved removal processes. These compounds can present chemical and environmental behaviours completely different from the starting active ingredient. The difficulty lies on their identification or/and their quantification due to the lack of analytical reference standards. In this context, ex situ Nuclear Magnetic Resonance (NMR) and Liquid Chromatography-NMR (LC-NMR) were used as complementary tools to LC-Mass Spectrometry (MS) to define the metabolic pathway of mesotrione, an emergent herbicide, by the bacterial strain Bacillus sp. 3B6. The complementarities of ex situ and LC-NMR allowed us to unambiguously identify six metabolites whereas the structures of only four metabolites were suggested by LC-MS. The presence of a new metabolic pathway was evidenced by NMR. These results demonstrate that NMR and LC-NMR spectroscopy provided unambiguous structural information for xenobiotic metabolic profiling, even at moderate magnetic field and allowed direct absolute quantification despite the lack of commercial or synthetic standards, required for LC-MS techniques. PMID:20692682

Durand, Stéphanie; Sancelme, Martine; Besse-Hoggan, Pascale; Combourieu, Bruno

2010-08-07

280

Proton NMR spectroscopy of human blood plasma and red blood cells  

SciTech Connect

The purpose of this article is to review some of the NMR techniques used to measure /sup 1/H NMR spectra of human plasma and red blood cells. The /sup 1/H NMR spectroscopy of plasma and red blood cells of interest because reported studies indicate that information relevant to biochemical and clinical applications can be obtained by /sup 1/H NMR.

Rabenstein, D.L.; Millis, K.K.; Strauss, E.J.

1988-12-15

281

NMR Studies of Low-Gamma Nuclei in Solids  

SciTech Connect

Over the past five years we have devoted considerable time to solid-state NMR investigaitons of nuclei, which are traditionally known as "difficult" because of their small magnetic moments. These include quadrupolar nuclei such as 35Cl, 53 Cr, 91Zr, 95Mo, 99Ru, 131 Xe, as well as spin-1/2 nuclei such as 109Ag. While NMR studies of such isotopes remain challenging, the use of moderate to high magnetic field strengths together with a variety of enhancement techniques is leading to many interesting applications. In this talk some of our successes in studying these isotopes will be presented. For example, we will present preliminary results of 131Xe NMR studies of solid sodium perxenate, as well as 109Ag NMR studies of silver dialkylphosphites. Our experience using population enhancement techniques that utilize hyperbolic secant pulses will also be discussed.

Wasylishen, Roderick E.; Forgeron, Michelle A.; Siegel, Renee; Nakashima, Thomas T.; Chen, Fu; Ooms, Kristopher J.; Feindel, Kirk W.

2006-07-24

282

Guidelines for the Introduction of Nuclear Magnetic Resonance (NMR) Technology.  

National Technical Information Service (NTIS)

In August 1983 the CAHSA Governing Body appointed the High Technology Committee to plan for the rational introduction of high medical technology in HSA 1, with the immediate task of examining Nuclear Magnetic Resonance (NMR) and determining guidelines for...

1983-01-01

283

Improved baseline in 29Si NMR spectra of water glasses.  

PubMed

It is shown by experiments that replacing one-pulse sequence by RIDE (ring down elimination) pulse sequence may dramatically improve the baseline of (29)Si NMR spectra and eliminate the signal from the probe. PMID:23640747

Schraml, Jan; Sandor, Peter; Korec, Stefan; Krump, Martin; Foller, Bronislav

2013-05-03

284

Solid phase coal liquefaction by mild hydrogenation. Solid NMR studies.  

National Technical Information Service (NTIS)

High resolution NMR of coal during hydrogenation is studied. Aromaticity of 4 coals is determined by carbon 13 nuclear magnetic resonance. Aromaticity increases with hydrogenation and coal rank. Products obtained are distilled and tar, the distillation re...

A. P. Legrand H. Sfihi M. F. Guinton S. Pregermain D. Carson

1985-01-01

285

Teaching 1H NMR Spectrometry Using Computer Modeling.  

ERIC Educational Resources Information Center

Molecular modeling by computer is used to display stereochemistry, molecular orbitals, structure of transition states, and progress of reactions. Describes new ideas for teaching 1H NMR spectroscopy using computer modeling. (Contains 12 references.) (ASK)

Habata, Yoichi; Akabori, Sadatoshi

2001-01-01

286

NMR spectroscopic examination of shocked sandstone from Meteor Crater, Arizona.  

National Technical Information Service (NTIS)

Solid state silicon-29 nuclear magnetic resonance (NMR) spectroscopy has been used to characterize the formation of high pressure silica polymorphs and amorphous material associated with the shocked Coconino Sandstone from Meteor Crater, Arizona. Five sam...

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

1993-01-01

287

Fluid-Rock Characterization and Interactions in NMR Well Logging.  

National Technical Information Service (NTIS)

The objective is to characterize the fluid properties and fluid-rock interactions that are needed for formation evaluation by nuclear magnetic resonance (NMR) well logging. This project is a partnership between Professor George J. Hirasaki at Rice Univers...

G. J. Hirasaki K. K. Mohanty

2002-01-01

288

The Study of Mechanisms of Superconductivity by NMR Relaxation  

NASA Astrophysics Data System (ADS)

This chapter describes the use of NMR to study superconductivity. The focus is on the use of NMR measurements of spin-lattice relaxation (T 1) to provide insight into the possible mechanisms which give rise to superconductivity. The chapter begins with a review of NMR T 1 in the normal state of metals, followed by an explanation of how, according to the theory of Bardeen, Cooper, and Schrieffer (BCS), the situation is modified when the metal becomes superconducting. These ideas are then applied in a discussion of several recent superconducting systems. Data presented for alkali fullerenes show that the fullerides are conventional BCS superconductors, while data for cuprate superconductors suggest a much different type of superconducting pairing. The authors conclude with a discussion of some organic materials that exhibit superconductivity or, with slight modification in structure, antiferromagnetism. In the studies of the antiferromagnetism, it is found that NMR can detect the electron spin-spin interaction discovered by Dzialoshinskii and Moriya.

Smith, Dylan F.; Slichter, Charles P.

289

Detection of low-populated reaction intermediates with hyperpolarized NMR.  

PubMed

Hyperpolarized (13)C NMR spectroscopy can provide the sensitivity and spectral resolution to detect, identify and quantify low-populated reaction intermediates, thus yielding direct chemical information on reaction mechanisms in real-time assays. PMID:20448982

Jensen, Pernille R; Meier, Sebastian; Ardenkjaer-Larsen, Jan H; Duus, Jens Ø; Karlsson, Magnus; Lerche, Mathilde H

2009-07-20

290

Metabolic pathway visualization in living yeast by DNP-NMR.  

PubMed

Central carbon metabolism of living Saccharomyces cerevisiae is visualized by DNP-NMR. Experiments are conducted as real time assays that detect metabolic bottlenecks, pathway use, reversibility of reactions and reaction mechanisms in vivo with subsecond time resolution. PMID:21720636

Meier, Sebastian; Karlsson, Magnus; Jensen, Pernille R; Lerche, Mathilde H; Duus, Jens Ø

2011-07-01

291

Mixing and matching detergents for membrane protein NMR structure determination.  

PubMed

One major obstacle to membrane protein structure determination is the selection of a detergent micelle that mimics the native lipid bilayer. Currently, detergents are selected by exhaustive screening because the effects of protein-detergent interactions on protein structure are poorly understood. In this study, the structure and dynamics of an integral membrane protein in different detergents is investigated by nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy and small-angle X-ray scattering (SAXS). The results suggest that matching of the micelle dimensions to the protein's hydrophobic surface avoids exchange processes that reduce the completeness of the NMR observations. Based on these dimensions, several mixed micelles were designed that improved the completeness of NMR observations. These findings provide a basis for the rational design of mixed micelles that may advance membrane protein structure determination by NMR. PMID:19425578

Columbus, Linda; Lipfert, Jan; Jambunathan, Kalyani; Fox, Daniel A; Sim, Adelene Y L; Doniach, Sebastian; Lesley, Scott A

2009-06-01

292

Mixing and Matching Detergents for Membrane Protein NMR Structure Determination  

PubMed Central

One major obstacle to membrane protein structure determination is the selection of a detergent micelle that mimics the native lipid bilayer. Currently, detergents are selected by exhaustive screening because the effects of protein-detergent interactions on protein structure are poorly understood. In this study, the structure and dynamics of an integral membrane protein in different detergents is investigated by nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy, and small angle X-ray scattering (SAXS). The results suggest that matching of the micelle dimensions to the protein’s hydrophobic surface avoids exchange processes that reduce the completeness of the NMR observations. Based on these dimensions, several mixed micelles were designed that improved the completeness of NMR observations. These findings provide a basis for the rational design of mixed micelles that may advance membrane protein structure determination by NMR.

Columbus, Linda; Lipfert, Jan; Jambunathan, Kalyani; Fox, Daniel A.; Sim, Adelene Y. L.; Doniach, Sebastian; Lesley, Scott A.

2009-01-01

293

Mixing and Matching Detergents for Membrane Protein NMR Structure Determination  

SciTech Connect

One major obstacle to membrane protein structure determination is the selection of a detergent micelle that mimics the native lipid bilayer. Currently, detergents are selected by exhaustive screening because the effects of protein-detergent interactions on protein structure are poorly understood. In this study, the structure and dynamics of an integral membrane protein in different detergents is investigated by nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy and small-angle X-ray scattering (SAXS). The results suggest that matching of the micelle dimensions to the protein's hydrophobic surface avoids exchange processes that reduce the completeness of the NMR observations. Based on these dimensions, several mixed micelles were designed that improved the completeness of NMR observations. These findings provide a basis for the rational design of mixed micelles that may advance membrane protein structure determination by NMR.

Columbus, Linda; Lipfert, Jan; Jambunathan, Kalyani; Fox, Daniel A.; Sim, Adelene Y.L.; Doniach, Sebastian; Lesley, Scott A.; (Stanford); (Scripps); (UV)

2009-10-21

294

Applications of NMR spectroscopy to the Study of Zeolite Synthesis.  

National Technical Information Service (NTIS)

NMR spectroscopy is a powerful technique for identifying the structure and concentration of silicate and aluminosilicate anions in gels and solution used for zeolite synthesis. A review is presented of the types of species that have been observed and the ...

A. T. Bell

1989-01-01

295

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

296

Training Program in Breast Cancer Research Using NMR Techniques.  

National Technical Information Service (NTIS)

This is a six year training program in breast cancer research using NMR techniques. This program has supported seven predoctoral students and five postdoctoral students. All the trainees have learned the theory and instrumentation of MRI. They have been a...

P. C. Wang

2006-01-01

297

RPF: a quality assessment tool for protein NMR structures.  

PubMed

We describe the RPF web server, a quality assessment tool for protein NMR structures. The RPF server measures the 'goodness-of-fit' of the 3D structure with NMR chemical shift and unassigned NOESY data, and calculates a discrimination power (DP) score, which estimates the differences between the fits of the query structures and random coil structures to these experimental data. The DP-score is an accuracy predictor of the query structure. The RPF server also maps local structure quality measures onto the 3D structure using an online molecular viewer, and onto the NMR spectra, allowing refinement of the structure and/or NOESY peak list data. The RPF server is available at: http://nmr.cabm.rutgers.edu/rpf. PMID:22570414

Huang, Yuanpeng Janet; Rosato, Antonio; Singh, Gautam; Montelione, Gaetano T

2012-05-08

298

Analysis of cold rolling oils by NMR and IR techniques  

SciTech Connect

A new technology has been developed based on infrared (IR) and nuclear magnetic resonance (NMR) spectroscopic techniques for the quantitation of various components in rolling oils without their prior separation. The IR method makes use of a curve-fitting approach in which the multicomponent mixtures with overlapping bands can be quantified without exhibiting isolated, characteristic frequencies for each component. Prior information about the nature and the type of the components in the mixture is the basic requirement for this method. NMR methodology involves the direct identification and quantitation of various components from their characteristic {sup 1}H, {sup 13}C and {sup 31}P-NMR chemical shift data. Both IR and NMR techniques have been successfully applied to nine component blends and commercial oils. 5 refs., 4 figs., 4 tabs.

Chopra, A.; Sastry, M.I.S.; Kapur, G.S.; Sarpal, A.S. [Indian Oil Corporation Limited, Faridabad (India)] [and others

1996-04-01

299

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

300

Cell signaling, post-translational protein modifications and NMR spectroscopy.  

PubMed

Post-translationally modified proteins make up the majority of the proteome and establish, to a large part, the impressive level of functional diversity in higher, multi-cellular organisms. Most eukaryotic post-translational protein modifications (PTMs) denote reversible, covalent additions of small chemical entities such as phosphate-, acyl-, alkyl- and glycosyl-groups onto selected subsets of modifiable amino acids. In turn, these modifications induce highly specific changes in the chemical environments of individual protein residues, which are readily detected by high-resolution NMR spectroscopy. In the following, we provide a concise compendium of NMR characteristics of the main types of eukaryotic PTMs: serine, threonine, tyrosine and histidine phosphorylation, lysine acetylation, lysine and arginine methylation, and serine, threonine O-glycosylation. We further delineate the previously uncharacterized NMR properties of lysine propionylation, butyrylation, succinylation, malonylation and crotonylation, which, altogether, define an initial reference frame for comprehensive PTM studies by high-resolution NMR spectroscopy. PMID:23011410

Theillet, Francois-Xavier; Smet-Nocca, Caroline; Liokatis, Stamatios; Thongwichian, Rossukon; Kosten, Jonas; Yoon, Mi-Kyung; Kriwacki, Richard W; Landrieu, Isabelle; Lippens, Guy; Selenko, Philipp

2012-09-26

301

NMR on Single Crystals of Potassium Cyanogen Bromide  

NASA Astrophysics Data System (ADS)

Single crystals of K(CN)_{ rm x}/(Br)_{rm 1-x} enriched in ^{15 }N have been studied by ^{15 }N NMR. Because of the anisotropic chemical shift, the NMR frequency spectrum of the orientational glass state reflects the distribution of cyanide orientations. By studying the spectrum at many orientations of each crystal, the orientational probability distribution function P( Omega) has been determined for x = 0.50 and for x = 0.20. The probability function is largest along the (100) directions, intermediate in the (110) directions, and nearly 0 along the (111) directions. The NMR determined P(Omega) is presented graphically and in terms of the Kubic Harmonic functions. The NMR results are in sharp contrast to molecular dynamics calculations but agree with neutron scattering data for x = 0.53.

Walton, Jeffrey Howard

302

RPF: a quality assessment tool for protein NMR structures  

PubMed Central

We describe the RPF web server, a quality assessment tool for protein NMR structures. The RPF server measures the ‘goodness-of-fit’ of the 3D structure with NMR chemical shift and unassigned NOESY data, and calculates a discrimination power (DP) score, which estimates the differences between the fits of the query structures and random coil structures to these experimental data. The DP-score is an accuracy predictor of the query structure. The RPF server also maps local structure quality measures onto the 3D structure using an online molecular viewer, and onto the NMR spectra, allowing refinement of the structure and/or NOESY peak list data. The RPF server is available at: http://nmr.cabm.rutgers.edu/rpf.

Huang, Yuanpeng Janet; Rosato, Antonio; Singh, Gautam; Montelione, Gaetano T.

2012-01-01

303

NMR studies on the conformation of polyflavanoids and their ...  

Treesearch

Science.gov - We Participate ... The polyflavanoids rank second in abundance after lignin as a source of renewable phenolic materials. ... Both NMR instrumentation and computational chemistry software are advancing at a fast pace and ...

304

Approaches to localized NMR spectroscopy in vivo  

SciTech Connect

Nuclear magnetic resonance (NMR) techniques are developed which allow spatially localized spectra to be obtained from living tissue. The localization methods are noninvasive and exploit the enhanced sensitivity afforded by surface coil probes. Techniques are investigated by computer simulation and experimentally verified by the use of phantom samples. The feasibility and utility of the techniques developed in this research are demonstrated by /sup 31/P spatial localization experiments involving various in vivo organs. In the first part of the thesis, two feasible approaches to localized spectroscopy, which were developed by other laboratories are theoretically analyzed by computer simulation. An alternative approach is provided by the rotating frame zeugmatography experiment which affords chemical-shift spectra displayed as a function of penetration distance into the sample. The further modification of the rotating frame experiment is developed, the Fourier series window (FSW) approach, which utilizes various types of window functions to afford localization in one or a few tissue regions of interest with high sensitivity. Theoretical comparisons with depth pulse methods are also included, along with methods to refine adverse off-resonance behavior.

Garwood, M.G.

1985-01-01

305

Silver-109 NMR spectroscopy of inorganic solids.  

PubMed

In this study the (109)Ag NMR spectra of the following solid inorganic silver-containing compounds were investigated: AgNO(3), AgNO(2), Ag(2)SO(4), Ag(2)SO(3), AgCO(3), Ag(3)PO(4), AgCl, AgBr, AgI, AgSO(3)CH(3), silver p-toluenesulfonate, NaAg(CN)(2), KAg(CN)(2), K(3)Ag(CN)(4), Me(4)NAgCl(2), silver diethylthiocarbamate, silver lactate, silver acetate, silver citrate, and bis[(N,N(1)-di-tert-butylformamidinato)silver(I)]. The magic angle spinning (MAS) spectra of all compounds were obtained. In some cases, when protons were available, the (1)H to (109)Ag cross-polarization (CP) technique was used to enhance the signal and shorten the experimental relaxation delay. It was possible to obtain slow MAS (or CP/MAS) or nonspinning spectra for 10 samples, allowing the determination of the principal components of the (109)Ag chemical shift (CS) tensors. The isotropic chemical shifts and the CS tensors are discussed in light of the available crystal structures. The need for an accepted standard for referencing (109)Ag chemical shifts and the use of AgSO(3)CH(3) as a CP setup sample are also discussed. PMID:15332810

Penner, Glenn H; Li, Wenli

2004-09-01

306

NMR Studies of Enzyme Structure and Mechanism  

NASA Astrophysics Data System (ADS)

At least three NMR methodologies pioneered by Al Redfield, have greatly benefited enzymology: (1) the suppression of strong water signals without pre-saturation; (2) sequence specific NH/ND exchange; and (3) dynamic studies of mobile loops of proteins. Water suppression has enabled us to identify unusually short, strong H-bonds at the active sites of five enzymes (three isomerases and two esterases), and to measure their lengths from both the chemical shifts and D/H fractionation factors of the deshielded protons involved (J. Mol. Struct. 615, 163 (2002)). Backbone NH exchange studies were used to detect regions of an NTP pyrophosphohydrolase in which NH groups became selectively protected against exchange on Mg(2+) binding, and further protected on product (NMP) binding, thus locating binding sites as well as conformationally linked remote sites (Biochemistry 42, 10140 (2003)). Dynamic studies were used to elucidate the frequency of motion of a flexible loop of GDP-mannose hydrolase (66,000/sec) containing the catalytic base His-124, from exchange broadening of the side chain NH signals of His-124 in the free enzyme. The binding of Mg(2+) and GDP-mannose lock His-124 in position to deprotonate the entering water and complete the reaction.

Mildvan, Albert

2006-03-01

307

Deuteron NMR relaxation rates in cerium deuterides  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) measurements of the 2H spin-lattice and transverse relaxation rates, T-11 and T-12, have been made in a series of cerium deuterides, CeDx. Results are reported for 2.01<=x<=2.90 and temperatures 77 <=T<=573 K. Spin-lattice relaxation rates for 2H are compared to published rates for 1H and they are found to be in substantial agreement when 1H rates are multiplied by the square of the ratio of gyromagnetic ratios, (?2/?1)2. As in the cerium hydrides, the spin-lattice relaxation rates are dominated by the direct magnetic dipolar interaction between the hydrogen nuclear moments and the cerium electronic moments. No noticeable effects of nuclear quadrupole interactions were observed in the 2H data. Transverse relaxation rates (spin echo) are narrowed as temperature is increased with narrowing temperatures ranging from about 200 to 250 K, depending upon concentration. Spin-lattice relaxation rates of both isotopes of hydrogen are observed to be enhanced in the regime 2.1<=x<=2.55 and 103/T>3.5 K-1. From the data it could not be established whether this enhancement is attributed primarily to increased values of the mean squared magnetic moments of the cerium ions or to an increase in the relaxation time of the cerium moments in this regime.

Raizman, A.; Zamir, D.; Cotts, R. M.

1985-03-01

308

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

2013-07-24

309

NMR shifts for polycyclic aromatic hydrocarbons from first-principles  

Microsoft Academic Search

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

Timo Thonhauser; Davide Ceresoli; Nicola N. Marzari

2009-01-01

310

Quantitative estimates of porous media wettability from proton NMR measurements.  

PubMed

Nuclear magnetic resonance (NMR) relaxation time distributions provide information on the abundance and distribution of two immiscible fluids in the pores of fine-grain chalk samples. A model based on relative shifts of the water-relaxation component as a function of saturation results in a wettability index that is strongly correlated with independent dynamic measurements of wettability. Scales of wetting-phase film thickness for NMR and dynamic measurements explain differences in results between the two methods. PMID:9803903

Howard, J J

311

NMR Imaging in Dentistry: Relaxation and Diffusion Studies  

Microsoft Academic Search

Magnetic resonance imaging has been widely used for medical diagnosis in recent years. The knowledge of the proton spin-lattice relaxation time, T1, represents the basis for NMR imaging. In the present study, we measured T1 in saliva, gingival fluid, gingival blood, and inflamed gingiva by means of a pulsed NMR Fourier-transform spectrometer. From several measurements, we found the following average

U. Skaleri?; J. Dolinšek; J. Stepisnik; P. Cevc; M. Schara

1987-01-01

312

A temperature-jump design for conventional NMR probes  

Microsoft Academic Search

The design and performance of a simple probe insert for temperature-jump experiments in conventional NMR probes is described. The insert uses the output from conventional NMR amplifiers for heating conductive aqueous samples with a rate of 30–80K\\/s for 200W radiofrequency power. The observed dependence of the heating rate on sample conductivity is explained by the dominance of dielectric heating. Factors

Pavel V. Yushmanov; István Furó

2006-01-01

313

Recent progress in NMR\\/MRI in petroleum applications  

Microsoft Academic Search

NMR has become an important technique for characterization of porous materials. In particular, its importance in petroleum exploration has been enhanced by the recent progress in NMR well-logging techniques and instruments. Such advanced techniques are increasing being accepted as a valuable service especially in deep-sea exploration. This paper will outline the recent progress of MR techniques at Schlumberger-Doll Research. Well-logging

Yi-Qiao Song

2007-01-01

314

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

315

19F and 1H NMR spectra of halocarbons.  

PubMed

19F NMR chemical shifts and coupling constants are reported for 215 compounds. For 77 of these compounds, 1H NMR spectral data are also given. Long-range couplings, including 8J(F,F) and 5J(F,H), are reported. The complexity of halocarbon spectra owing to the presence of rotational isomers, asymmetric centers, long-range couplings, and chlorine isotope effects are illustrated, and the methods used for analyzing such complex spectra are briefly discussed. PMID:15137047

Foris, Anthony

2004-06-01

316

Two-dimensional NMR studies of native coenzyme F430  

Microsoft Academic Search

Modern two-dimensional (2D) NMR spectroscopic methods are used to determine signal assignments and structural features of the recently discovered nickel(II)-containing coenzyme F430. This is the first detailed ¹H and ¹³C NMR study of the native form of coenzyme F430. With the use of COSY, HOHAHA, NOESY, and ROESY ¹H-¹H correlated spectroscopies in combination with HMQC and HMBC ¹H-¹³C correlated spectroscopies,

Hoshik Won; Michael F. Summers; Karl D. Olson; Ralph S. Wolfe

1990-01-01

317

Quantitative NMR Analysis of Partially Substituted Biodiesel Glycerols  

SciTech Connect

Phosphitylation of hydroxyl groups in biodiesel samples with 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane followed by 31P-NMR analysis provides a rapid quantitative analytical technique for the determination of substitution patterns on partially esterified glycerols. The unique 31P-NMR chemical shift data was established with a series mono and di-substituted fatty acid esters of glycerol and then utilized to characterize an industrial sample of partially processed biodiesel.

Nagy, M.; Alleman, T. L.; Dyer, T.; Ragauskas, A. J.

2009-01-01

318

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

2012-01-05

319

NMR relaxometry and differential scanning calorimetry during meat cooking  

Microsoft Academic Search

By combining simultaneous nuclear magnetic resonance (NMR) T2 relaxometry and differential scanning calorimetry (DSC) on pork samples heated to nine temperature levels between 25 and 75°C, the present study investigates the relationship between thermal denaturation of meat proteins and heat-induced changes in water characteristics. Principal component analysis (PCA) on the distributed 1H NMR T2 relaxation data revealed that the major

Hanne Christine Bertram; Zhiyun Wu; Frans van den Berg; Henrik J. Andersen

2006-01-01

320

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

321

High-resolution NMR probe for high pressure studies  

Microsoft Academic Search

Specialized design features of high-resolution, high-pressure NMR probe are discussed. A new design of the high-pressure NMR\\u000a probe is presented. The achieved performance characteristics such as high resolution, high sensitivity, large sample volume,\\u000a variable temperature, and wide range of pressures up to 1000 MPa make this instrumentation well suited for studies of biochemical\\u000a systems.

P. Koziol; C. Reiner; J. Jonas

1996-01-01

322

The Xplor-NIH NMR molecular structure determination package  

Microsoft Academic Search

We announce the availability of the Xplor-NIH software package for NMR biomolecular structure determination. This package consists of the pre-existing XPLOR program, along with many NMR-specific extensions developed at the NIH. In addition to many features which have been developed over the last 20 years, the Xplor-NIH package contains an interface with a new programmatic framework written in C++. This

Charles D. Schwieters; John J. Kuszewski; Nico Tjandra; G. Marius Clorec

2003-01-01

323

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

324

Deuterium incorporation in biomass cell wall components by NMR analysis  

SciTech Connect

A commercially available deuterated kale sample was analyzed for deuterium incorporation by ionic liquid solution 2H and 1H 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.

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

2012-01-01

325

NMR analysis of an antiferromagnetic intermetallic rare earth compound  

Microsoft Academic Search

Zero field NMR of 139La probes in antiferromagnetically ordered GdAg was measured using phase-independent linear spin echo detection. Lineshape analysis gives information about the magnetic structure. 139La NMR of a La0.995Gd0.005Ag single crystal in an external field yields hyperfine field contributions from distinct Gd neighbours, especially of the third nearest one. The comparison of both sets of data allows one

U. Goebel; E. Dormann

1979-01-01

326

NMR spectroscopy of rare earth–3d transition metal alloys  

Microsoft Academic Search

Recent nuclear magnetic resonance studies of magnetically ordered rare earth–3d transition metal alloys are reviewed. Selected experimental results for rare earth NMR of RETM2 Laves phases as well as RE2TM14B and interstitially modified RE2TM17Ax (A=N,C,H) materials for permanent magnet applications are surveyed. An analysis of the hyperfine parameters obtained from NMR experiments is presented and their relation to the physical

Czes?aw Kapusta

1998-01-01

327

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

328

Sequentially acquired two-dimensional NMR spectra from hyperpolarized sample  

NASA Astrophysics Data System (ADS)

A scheme capable of acquiring heteronuclear 2D NMR spectra of hyperpolarized sample is described. Hyperpolarization, the preparation of nuclear spins in a polarized state far from thermal equilibrium, can increase the NMR signal by several orders of magnitude. It presents opportunities to apply NMR spectroscopy to dilute samples that would otherwise yield insufficient signal. However, conventional 2D NMR spectroscopy, which is commonly applied for the determination of molecular structure, relies on the recovery of the initial polarization after each transient. For this reason, it cannot be applied directly to a sample that has been hyperpolarized once. With appropriately modified pulse schemes, two-dimensional NMR spectra an however be acquired sequentially by utilizing a small portion of the hyperpolarized signal in every scan, while keeping the remaining polarization for future scans. We present heteronuclear multi-quantum spectra of single hyperpolarized samples using this technique, and discuss different options for distributing the polarization among different scans. This robust method takes full advantage of Fourier NMR to resolve overlapping chemical shifts, and may prove particularly useful for the structural elucidation of compounds in mass-limited samples.

Zeng, Haifeng; Bowen, Sean; Hilty, Christian

2009-08-01

329

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

330

ECG gated NMR-CT for cardiovascular diseases  

SciTech Connect

The authors applied NMR-CT to cardiac study with ECG gated technique to evaluate the left ventricular (LV) function and compared it with cardiovascular nuclear medicine study (NM). The NMR-CT machine has resistive air-core magnet with 0.15 Tesla. The saturation recovery image or inversion recovery image were obtained as 256 x 256 matrix and 15 mm in thickness. The study population was ten patients who were evaluated both by NMR image and by NM performed within one week interval. The heart muscle was able to be visualized without any contrast material nor radioisotopes in inversion recovery images, whereas saturation recovery images failed to separate heart muscle from blood pool. The wall motions of LV in both methods were well correlated except for inferior wall. The values of ejection fraction in NMR image were moderately low, but two modalities showed satisfactory correlation (r=0.85). The region of myocardial infarction was revealed as wall thinning and/or wall motion abnormality. It is still preliminary to draw a conclusion, however, it can be said that in the evaluation of LV function, method by NMR might be of equal value to those of NM. It can be certain that eventually gated NMR-CT will become more effective method for various aspects of cardiovascular evaluation.

Nishikawa, J.; Machida, K.; Iio, M.; Yoshimoto, N.; Sugimoto, T.; Kawaguchi, H.; Mano, H.

1984-01-01

331

Protein folding on the ribosome studied using NMR spectroscopy.  

PubMed

NMR spectroscopy is a powerful tool for the investigation of protein folding and misfolding, providing a characterization of molecular structure, dynamics and exchange processes, across a very wide range of timescales and with near atomic resolution. In recent years NMR methods have also been developed to study protein folding as it might occur within the cell, in a de novo manner, by observing the folding of nascent polypeptides in the process of emerging from the ribosome during synthesis. Despite the 2.3MDa molecular weight of the bacterial 70S ribosome, many nascent polypeptides, and some ribosomal proteins, have sufficient local flexibility that sharp resonances may be observed in solution-state NMR spectra. In providing information on dynamic regions of the structure, NMR spectroscopy is therefore highly complementary to alternative methods such as X-ray crystallography and cryo-electron microscopy, which have successfully characterized the rigid core of the ribosome particle. However, the low working concentrations and limited sample stability associated with ribosome-nascent chain complexes means that such studies still present significant technical challenges to the NMR spectroscopist. This review will discuss the progress that has been made in this area, surveying all NMR studies that have been published to date, and with a particular focus on strategies for improving experimental sensitivity. PMID:24083462

Waudby, Christopher A; Launay, Hélène; Cabrita, Lisa D; Christodoulou, John

2013-07-27

332

High resolution MAS-NMR in combinatorial chemistry.  

PubMed

High-resolution magic angle spinning (hr-MAS) NMR is a powerful tool for characterizing organic reactions on solid support. Because magic angle spinning reduces the line-broadening due to dipolar coupling and variations in bulk magnetic susceptibility, line widths approaching those obtained in solution-phase NMR can be obtained. The magic angle spinning method is amenable for use in conjunction with a variety of NMR-pulse sequences, making it possible to perform full-structure determinations and conformational analysis on compounds attached to a polymer support. Diffusion-weighted MAS-NMR methods such as SPEEDY (Spin-Echo-Enhanced Diffusion-Filtered Spectroscopy) can be used to remove unwanted signals from the solvent, residual reactants, and the polymer support from the MAS-NMR spectrum, leaving only those signals arising from the resin-bound product. This review will present the applications of high-resolution magic angle spinning NMR for use in combinatorial chemistry research. PMID:11288068

Shapiro, M J; Gounarides, J S

333

NMR-spectroscopic analysis of mixtures: from structure to function  

PubMed Central

NMR spectroscopy as a particularly information-rich method offers unique opportunities for improving the structural and functional characterization of metabolomes, which will be essential for advancing the understanding of many biological processes. Whereas traditionally NMR spectroscopy was mostly relegated to the characterization of pure compounds, the last few years have seen a surge of interest in using NMR spectroscopic techniques for characterizing complex metabolite mixtures. Development of new methods was motivated partly by the realization that using NMR for the analysis of metabolite mixtures can help identify otherwise inaccessible small molecules, for example compounds that are prone to chemical decomposition and thus cannot be isolated. Furthermore, comparative metabolomics and statistical analyses of NMR-spectra have proven highly effective at identifying novel and known metabolites that correlate with changes in genotype or phenotype. In this review, we provide an overview of the range of NMR spectroscopic techniques recently developed for characterizing metabolite mixtures, including methods used in discovery-oriented natural product chemistry, in the study of metabolite biosynthesis and function, or for comparative analyses of entire metabolomes.

Forseth, Ry R.; Schroeder, Frank C.

2010-01-01

334

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

335

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

2013-08-14

336

Combining insights from solid-state NMR and first principles calculation: applications to the 19F NMR of octafluoronaphthalene.  

PubMed

Advances in solid-state NMR methodology and computational chemistry are applied to the (19)F NMR of solid octafluoronaphthalene. It is demonstrated experimentally, and confirmed by density functional theory (DFT) calculations, that the spectral resolution in the magic-angle spinning spectrum is limited by the anisotropy of the bulk magnetic susceptibility (ABMS). This leads to the unusual observation that the resolution improves as the sample is diluted. DFT calculations provide assignments of each of the peaks in the (19)F spectrum, but the predictions are close to the limits of accuracy and correlation information from 2-D NMR is invaluable in confirming the assignments. The effects of non-Gaussian lineshapes on the use of 2-D NMR for mapping correlations of spectral frequencies (e.g. due to the ABMS) are also discussed. PMID:17492102

Robbins, Andrew J; Ng, William T K; Jochym, Dominik; Keal, Thomas W; Clark, Stewart J; Tozer, David J; Hodgkinson, Paul

2007-03-27

337

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

NASA Astrophysics Data System (ADS)

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 1H 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.

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

338

Comparison of Fluorescence, 31P NMR, and 7Li NMR Spectroscopic Methods for Investigating Li +\\/Mg 2+ Competition for Biomolecules  

Microsoft Academic Search

The biochemical action of lithium in the treatment of manic-depressive illness is still unknown. One hypothesis is that Li+ competes for Mg2+-binding sites in biomolecules. We report here our studies on metal ion competition by three distinct methods: fluorescence, 31P NMR, and 7Li NMR spectroscopy, using ATP as a model ligand. By fluorescence spectroscopy, we used the dye, furaptra, by

Louis Amari; Brian Layden; Qinfen Rong; Carlos F. G. C. Geraldes; Duarte Mota de Freitas

1999-01-01

339

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

PubMed

31P NMR saturation-transfer techniques have been employed in glucose-grown derepressed yeast to determine unidirectional fluxes in the upper part of the Embden-Meyerhof-Parnas pathway. The experiments were performed during anaerobic and aerobic glycolysis by saturating the ATP gamma resonances and monitoring changes in the phosphomonoester signals from glucose 6-phosphate and fructose 1,6-bis-phosphate. These experiments were supplemented with 13C NMR measurements of glucose utilization rates and 13C NMR label distribution studies. Combined with data obtained previously from radioisotope measurements, these 31P and 13C NMR kinetic studies allowed estimation of the net glycolytic flow in addition to relative flows through phosphofructokinase (PFK) and Fru-1,6-P2ase during anaerobic and aerobic glycolysis. The 31P NMR saturation-transfer results are consistent with previous results obtained from measurements of metabolite levels, radioisotope data, and 13C NMR studies [den Hollander, J.A., Ugurbil, K., Brown, T.R., Bednar, M., Redfield, C., & Shulman, R.G. (1986a) Biochemistry 25, 203-211], providing additional support for in vivo measurement of the flows during glycolysis. PMID:2962638

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

1987-11-17

340

Noninvasive testing of art and cultural heritage by mobile NMR.  

PubMed

Nuclear magnetic resonance (NMR) has many applications in science, medicine, and technology. Conventional instrumentation is large and expensive, however, because superconducting magnets offer maximum sensitivity. Yet NMR devices can also be small and inexpensive if permanent magnets are used, and samples need not be placed within the magnet but can be examined externally in the stray magnetic field. Mobile stray-field NMR is a method of growing interest for nondestructive testing of a diverse range of materials and processes. A well-known stray-field sensor is the commercially available NMR-MOUSE, which is small and can readily be carried to an object to be studied. In this Account, we describe mobile stray-field NMR, with particular attention to its use in analyzing objects of cultural heritage. The most common data recorded are relaxation measurements of (1)H because the proton is the most sensitive NMR nucleus, and relaxation can be measured despite the inhomogeneous magnetic field that typically accompanies a simple magnet design. Through NMR relaxation, the state of matter can be analyzed locally, and the signal amplitude gives the proton density. A variety of stray-field sensors have been designed. Small devices weighing less than a kilogram have a shallow penetration depth of just a few millimeters and a resolution of a few micrometers. Access to greater depths requires larger sensors that may weigh 30 kg or more. The use of these sensors is illustrated by selected examples, including examinations of (i) the stratigraphy of master paintings, (ii) binder aging, (iii) the deterioration of paper, (iv) wood density in master violins, (v) the moisture content and moisture profiles in walls covered with paintings and mosaics, and (vi) the evolution of stone conservation treatments. The NMR data provide unique information to the conservator on the state of the object--including past conservation measures. The use of mobile NMR remains relatively new, expanding from field testing of materials such as roads, bridge decks, soil, and the contents of drilled wells to these more recent studies of objects of cultural heritage. As a young field, noninvasive testing of artworks with stray-field NMR thus offers many opportunities for research innovation and further development. PMID:20345119

Blümich, Bernhard; Casanova, Federico; Perlo, Juan; Presciutti, Federica; Anselmi, Chiara; Doherty, Brenda

2010-06-15

341

GEL-STATE NMR OF BALL-MILLED WHOLE CELL WALLS IN DMSO-d6 USING 2D SOLUTION-STATE NMR SPECTROSCOPY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Plant cell walls were used for obtaining 2D solution-state NMR spectra without actual solubilization or structural modification. Ball-milled whole cell walls were swelled directly in the NMR tube with DMSO-d6 where they formed a gel. There are relatively few gel-state NMR studies. Most have involved...

342

Solid-state NMR characterization of Mowry Formation shales  

SciTech Connect

Solid-state [sup 13]C and [sup 29]Si NMR measurements were carried out on a series of petroleum source rocks from the Mowry Formation of the Powder River Basin in Wyoming. The objectives of this study wereto use CP/MAS [sup 13]C NMR measurements to monitor changes in the carbon structure of the kerogen that result from depth of burial, and to examine the feasibility of [sup 29]Si NMR for studying the thermal alteration of clay minerals during diagenesis. Carbon and silicon NMR measurements were made on a suite of samples covering a present-day depth interval of 3,000 to 11,500 ft.In general, the NMR results endorsed other geochemical analyses that were performed on the source rocks as part of another study to examine pressure compartmentalization in the Mowry Formation. The carbon aromaticity of the kerogen increased with depth of burial, and at depths greater that approximately 10,000 ft the kerogen showed little capacity to generate additional oil because of the small fraction of residual aliphatic carbon. By combining NMR and Rock-Eval measurements, an estimate of the hydrogen budget was obtained. The calculations indicated that approximately 20% of the kerogen was converted to hydrocarbons, and that sufficient hydrogen was liberated from aromatization and condensation reactions to stabilize the generated products. The [sup 29]Si NMR spectra were characterized by a relatively sharp quartz resonance and a broad resonance from the clay minerals. With increasing depth of burial, the clay resonance became broader and shifted slightly downfield. These changes qualitatively support X-ray analysis that shows progressive alteration of illite to smectite with depth of burial.

Miknis, F.P.

1992-04-01

343

Solid-state NMR characterization of Mowry Formation shales  

SciTech Connect

Solid-state {sup 13}C and {sup 29}Si NMR measurements were carried out on a series of petroleum source rocks from the Mowry Formation of the Powder River Basin in Wyoming. The objectives of this study wereto use CP/MAS {sup 13}C NMR measurements to monitor changes in the carbon structure of the kerogen that result from depth of burial, and to examine the feasibility of {sup 29}Si NMR for studying the thermal alteration of clay minerals during diagenesis. Carbon and silicon NMR measurements were made on a suite of samples covering a present-day depth interval of 3,000 to 11,500 ft.In general, the NMR results endorsed other geochemical analyses that were performed on the source rocks as part of another study to examine pressure compartmentalization in the Mowry Formation. The carbon aromaticity of the kerogen increased with depth of burial, and at depths greater that approximately 10,000 ft the kerogen showed little capacity to generate additional oil because of the small fraction of residual aliphatic carbon. By combining NMR and Rock-Eval measurements, an estimate of the hydrogen budget was obtained. The calculations indicated that approximately 20% of the kerogen was converted to hydrocarbons, and that sufficient hydrogen was liberated from aromatization and condensation reactions to stabilize the generated products. The {sup 29}Si NMR spectra were characterized by a relatively sharp quartz resonance and a broad resonance from the clay minerals. With increasing depth of burial, the clay resonance became broader and shifted slightly downfield. These changes qualitatively support X-ray analysis that shows progressive alteration of illite to smectite with depth of burial.

Miknis, F.P.

1992-04-01

344

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

345

Intrauterine fetal brain NMR spectroscopy: 1H and 31P studies in rats  

SciTech Connect

Fetal brain metabolism was investigated in utero noninvasively using multinuclear nuclear magnetic resonance spectroscopy in rats at two representative prenatal stages: early (17-18 days) and late (20-21 days) stages. Phosphorus-31 (31P) spectroscopy revealed that phosphocreatine is significantly lower in the early stage and increases to the level of early neonates by the late prenatal stage. Intracellular pH at the early stage was found to be strikingly high (7.52 +/- 0.21) and decreased to a level similar to that of neonates by the late stage (7.29 +/- 0.07). Phosphomonoester levels at both stages were similar to the values reported for early neonates. Water-suppressed proton (1H) spectroscopy demonstrated a distinctive in vivo fetal brain spectral pattern characterized by low levels of N-acetyl aspartate and high levels of taurine. High-resolution proton spectroscopy and homonuclear chemical-shift correlate spectroscopy of brain perchloric acid extracts confirmed these in vivo findings. In vitro 31P spectroscopy of acidified chloroform methanol extracts showed the characteristic membrane phospholipid profiles of fetal brain. The phosphatidylethanolamine (PE)-to-phosphatidylcholine (PC) ratio (PE/PC) did not show significant changes between the two stages at 0.40 +/- 0.11, a value similar to that of early neonates.

Nakada, T.; Kwee, I.L.; Suzuki, N.; Houkin, K. (Veterans Administration Medical Center, Martinez, CA (USA))

1989-11-01

346

Magic-angle spinning NMR of cold samples.  

PubMed

Magic-angle-spinning solid-state NMR provides site-resolved structural and chemical information about molecules that complements many other physical techniques. Recent technical advances have made it possible to perform magic-angle-spinning NMR experiments at low temperatures, allowing researchers to trap reaction intermediates and to perform site-resolved studies of low-temperature physical phenomena such as quantum rotations, quantum tunneling, ortho-para conversion between spin isomers, and superconductivity. In examining biological molecules, the improved sensitivity provided by cryogenic NMR facilitates the study of protein assembly or membrane proteins. The combination of low-temperatures with dynamic nuclear polarization has the potential to boost sensitivity even further. Many research groups, including ours, have addressed the technical challenges and developed hardware for magic-angle-spinning of samples cooled down to a few tens of degrees Kelvin. In this Account, we briefly describe these hardware developments and review several recent activities of our group which involve low-temperature magic-angle-spinning NMR. Low-temperature operation allows us to trap intermediates that cannot be studied under ambient conditions by NMR because of their short lifetime. We have used low-temperature NMR to study the electronic structure of bathorhodopsin, the primary photoproduct of the light-sensitive membrane protein, rhodopsin. This project used a custom-built NMR probe that allows low-temperature NMR in the presence of illumination (the image shows the illuminated spinner module). We have also used this technique to study the behavior of molecules within a restricted environment. Small-molecule endofullerenes are interesting molecular systems in which molecular rotors are confined to a well-insulated, well-defined, and highly symmetric environment. We discuss how cryogenic solid state NMR can give information on the dynamics of ortho-water confined in a fullerene cage. Molecular motions are often connected with fundamental chemical properties; therefore, an understanding of molecular dynamics can be important in fields ranging from material science to biochemistry. We present the case of ibuprofen sodium salt which exhibits different degrees of conformational freedom in different parts of the same molecule, leading to a range of line broadening and line narrowing phenomena as a function of temperature. PMID:23488538

Concistrè, Maria; Johannessen, Ole G; Carignani, Elisa; Geppi, Marco; Levitt, Malcolm H

2013-03-14

347

Characterization of amorphous material in shocked quartz by NMR spectroscopy  

SciTech Connect

Nuclear magnetic resonance (NMR) analysis of the recovered products from a series of controlled explosive shock-loading experiments on quartz powders was performed to investigate shock-induced amorphization processes. Silicon-29 NMR spectroscopy is an excellent probe of the local bonding environment of silicon in minerals and is capable of detecting and characterizing amorphous and disordered components. NMR spectra obtained for the recovered material exhibit a narrow resonance associated with the shocked crystalline material, and a broad component consistent with an amorphous phase despite the absence of evidence for glass from optical microscopy. The NMR measurements were performed over a range of recycle times from 1 to 3 {times} 10{sup 5} S. Results demonstrate that the magnetization in both the crystalline and amorphous material following power-law behavior as a function of recycle time. The amorphous component dominates the spectra for short NMR recycle times due to its shorter relaxation time relative to the crystalline material. Fractal analysis of the power-law relations suggests a fractal dimension of 2 for the amorphous phase and 3 for the crystalline phase.

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

1993-08-01

348

First Principles NMR Study of Fluorapatite under Pressure  

PubMed Central

NMR is the technique of election to probe the local properties of materials. Herein we present the results of density functional theory (DFT) ab initio calculations of the NMR parameters for fluorapatite (FAp), a calcium orthophosphate mineral belonging to the apatite family, by using the GIPAW method [Pickard and Mauri, 2001]. Understanding the local effects of pressure on apatites is particularly relevant because of their important role in many solid state and biomedical applications. Apatites are open structures, which can undergo complex anisotropic deformations, and the response of NMR can elucidate the microscopic changes induced by an applied pressure. The computed NMR parameters proved to be in good agreement with the available experimental data. The structural evaluation of the material behavior under hydrostatic pressure (from ?5 to +100 kbar) indicated a shrinkage of the diameter of the apatitic channel, and a strong correlation between NMR shielding and pressure, proving the sensitivity of this technique to even small changes in the chemical environment around the nuclei. This theoretical approach allows the exploration of all the different nuclei composing the material, thus providing a very useful guidance in the interpretation of experimental results, particularly valuable for the more challenging nuclei such as 43Ca and 17O.

Pavan, Barbara; Ceresoli, Davide; Tecklenburg, Mary M. J.; Fornari, Marco

2012-01-01

349

NMR study of small molecule adsorption in MOF-74-Mg  

NASA Astrophysics Data System (ADS)

We calculate the carbon nuclear magnetic resonance (NMR) shielding for CO2 and the hydrogen shieldings for both H2 and H2O inside the metal organic framework MOF-74-Mg. Our ab initio calculations are at the density functional theory level using the van der Waals including density functional vdW-DF. The shieldings are obtained while placing the small molecules throughout the structure, including the calculated adsorption site for various loading scenarios. We then explore relationships between loading, rotational and positional characteristics, and the NMR shieldings for each adsorbate. Our NMR calculations show a change in the shielding depending on adsorbate, position, and loading in a range that is experimentally observable. We further provide a simple model for the energy and the NMR shieldings throughout the cavity of the MOF. By providing this mapping of shielding to position and loading for these adsorbates, we argue that NMR probes could be used to provide additional information about the position at which these small molecules bind within the MOF, as well as the loading of the adsorbed molecule.

Lopez, M. G.; Canepa, Pieremanuele; Thonhauser, T.

2013-04-01

350

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

351

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

352

Introducing Hyperpolarized Xenon-131 Directly Detected by NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

Previously, high-field NMR and MRI applications of hyperpolarized (hp) noble gasses focused on the isotopes helium-3 (spin I = 1/2), xenon-129 (spin I = 1/2) [1], and more recently krypton-83 (spin I = 9/2) [2]. In this contribution, hp xenon-131 (spin I = 3/2) was generated by spin-exchange optical pumping and separated from the rubidium vapor for high field NMR detection at 14.1 T field strength. Xenon-131 is of particular interest because of its quadrupolar nature that can be utilized for the study of surfaces [3] and for the investigation of high magnetic field effects on the electronic structure of the noble gas atom [4]. In addition, this isotope is a useful probe for quadrupolar processes during gas transfer and during NMR/MRI detection. Experiments with xenon-131, including multiple quantum filtered NMR spectroscopy [3], provides insights into similar processes present in krypton-83 and its more complicated spin system [5]. [1] D. Raftery Ann. Rep. NMR Spec., 57, 208 (2006). [2] G. Pavlovskaya, et al., Pro. Natl. Acad. Sci. U.S.A. 102, 18275 (2005). [3] T. Meersmann et al., Phys. Rev. Lett. 80, 1398 (1998). [4] T. Meersmann and M. Haake, Phys. Rev. Lett. 81, 1211 (1998). [5] Z. Cleveland, et al., J. Chem. Phys.124, 044312 (2006).

Stupic, Karl; Cleveland, Zackary; Pavlovskaya, Galina; Meersmann, Thomas

2007-03-01

353

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

354

Batch profiling calibration for robust NMR metabonomic data analysis.  

PubMed

Metabonomic studies involve the analysis of large numbers of samples to identify significant changes in the metabolic fingerprints of biological systems, possibly with sufficient statistical power for analysis. While procedures related to sample preparation and spectral data acquisition generally include the use of independent sample batches, these might be sources of systematic variation whose effects should be removed to focus on phenotyping the relevant biological variability. In this work, we describe a grouped-batch profile (GBP) calibration strategy to adjust nuclear magnetic resonance (NMR) metabolomic data-sets for batch effects either introduced during NMR experiments or samples work-up. We show how this method can be applied to data calibration in the context of a large-scale NMR epidemiological study where quality control samples are available. We also illustrate the efficiency of a batch profile correction for NMR metabonomic investigation of cell extracts, where GBP can significantly improve the predictive power of multivariate statistical models for discriminant analysis of the cell infection status. The method is applicable to a broad range of NMR metabolomic/metabonomic cohort studies. PMID:23975089

Fages, Anne; Pontoizeau, Clément; Jobard, Elodie; Lévy, Pierre; Bartosch, Birke; Elena-Herrmann, Bénédicte

2013-08-24

355

Study of cultured fibroblasts in vivo using NMR  

SciTech Connect

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. Signals were detected from cytoplasmic inorganic phosphate (P/sub i/), ATP, NAD, NADH, phosphorylcholine and phosphorylethanolamine. The effect of external glucose on cytoplasmic pools of phosphates was studied. When cells were perfused with glucose-free medium the rate of glycolysis decreased, the amplitudes of the ATP resonances decreased, and the P/sub i/ intensity increased. The quantity of NMR-detectable P/sub i/ produced was significantly greater than the quantity of NMR-detectable ATP which was lost. Experiments with /sup 32/P labeled P/sub i/ showed that as the concentration of glucose in the medium was increase, the amount of phosphate sequestered in the cells increased. We conclude that there is a pool of P/sub i/ which is not detected by high resolution NMR and that the size of this pool increases as the rate of glycolysis increase. Longtitudinal relaxation times of intracellular phosphates in normal, transformed, and primary CEFs were measured. The results demonstrate that relaxation times of phosphates are sensitive to structural and metabolic changes which occur when cells are grown in culture. 59 references. 31 figures.

Karczmar, G.S.

1984-08-01

356

Two-dimensional NMR studies of native coenzyme F430  

SciTech Connect

Modern two-dimensional (2D) NMR spectroscopic methods are used to determine signal assignments and structural features of the recently discovered nickel(II)-containing coenzyme F430. This is the first detailed {sup 1}H and {sup 13}C NMR study of the native form of coenzyme F430. With the use of COSY, HOHAHA, NOESY, and ROESY {sup 1}H-{sup 1}H correlated spectroscopies in combination with HMQC and HMBC {sup 1}H-{sup 13}C correlated spectroscopies, signal assignments were made for all carbon atoms and nonexchangeable protons. The data confirm 16 of the 21 specific {sup 13}C NMR signal assignments made earlier for native F430 by classical 1D NMR methods and provide assignment (or reassignment) of the remaining carbon atoms. The {sup 1}H NMR signal assignments reported here are in good agreement with the partial assignments reported previously for the pentamethyl ester derivative of F430 (F430M) in CD{sub 2}Cl{sub 2} solution. In addition, long-range through-bond {sup 1}H-{sup 13}C connectivities confirm aspects of the F430 structure deduced from studies of F430M by traditional spectroscopic and chemical methods.

Won, Hoshik; Summers, M.F. (Univ. of Maryland, Baltimore (USA)); Olson, K.D.; Wolfe, R.S. (Univ. of Illinois, Urbana (USA))

1990-03-14

357

PFG NMR studies of lysine-silica solutions.  

PubMed

The formation process of silica nanoparticles in lysine-silica mixtures was studied using dynamic light scattering (DLS) and pulsed-field gradient (PFG) NMR measurements. (1)H NMR shows line broadening of the lysine resonances during TEOS hydrolysis/nanoparticle formation. Analysis of the TEOS hydrolysis kinetics show that TEOS hydrolysis is the rate-limiting step in particle formation, and has an activation energy of 20.5 kJ/mol. Transverse relaxation measurements show a corresponding decrease in T(2) with TEOS hydrolysis, indicating a reduction in the lysine mobility due to lysine-silica interactions. PFG NMR results indicate a systemic decrease in the self-diffusion coefficient of lysine as particle formation proceeds. The results obtained can be described using a two-state model wherein lysine is either free in solution or bound to the nanoparticles. Analysis of the PFG data of samples made at various temperatures show that lysine coverage upon complete hydrolysis is between 2.5 and 2.8 mmol lysine/kg solution, and insensitive to the heating temperature. PFG NMR shows a linear increase in the amount of bound lysine with increasing lysine content, indicating an increase in the surface area present, i.e. more and smaller particles, with increased lysine content. The PFG NMR results presented give quantitative insights that indicate that while pH is likely the primary driver for the rate of particle formation and particle size, lysine is critical for stabilization of the nanoparticles. PMID:22789802

Li, Xiang; Shantz, Daniel F

2012-06-15

358

High resolution deuterium NMR studies of bacterial metabolism  

SciTech Connect

High resolution deuterium NMR spectra were obtained from suspensions of five bacterial strains: Escherichia coli, Clostridium perfringens, Klebsiella pneumoniae, Proteus mirabilis, and Staphylococcus aureus. Deuterium-labeled D-glucose at C-1, C-2, and C-6 was used to monitor dynamically anaerobic metabolism. The flux of glucose through the various bacterial metabolic pathways could be determined by following the disappearance of glucose and the appearance of the major end products in the 2H NMR spectrum. The presence of both labeled and unlabeled metabolites could be detected using 1H NMR spectroscopy since the proton resonances in the labeled species are shifted upfield due to an isotopic chemical shift effect. The 1H-1H scalar coupling observed in both the 2H and 1H NMR spectra was used to assign definitively the resonances of labeled species. An increase in the intensity of natural abundance deuterium signal of water can be used to monitor pathways in which a deuteron is lost from the labeled metabolite. The steps in which label loss can occur are outlined, and the influence these processes have on the ability of 2H NMR spectroscopy to monitor metabolism are assessed.

Aguayo, J.B.; Gamcsik, M.P.; Dick, J.D.

1988-12-25

359

NMR studies of fossil fuels. Final technical report  

SciTech Connect

This report has been based on a highly productive research effort involving collaboration between Colorado State University and the former Laramie Energy Technology Center. The CSU-LETC combination played a unique role in bringing NMR (nuclear magnetic resonance) to bear on certain types of fossil fuel problems that were previously not amenable to NMR study, i.e., those involving solid samples (coal, oil shale). The work drew heavily on fundamental solid-state NMR developments that had been previously reported from other laboratories, primarily in the MIT and Monsanto laboratories, and built upon these early developments to adapt and further develop new approaches for solid fossil fuel samples. For purposes of the present summary, work is separated into the following three categories: (1) Fossil Fuel Studies, (2) NMR Technique Development, and (3) NMR Instrumentation Development. Of course, there is a substantial amount of overlap between these categories; nevertheless, for convenience of organization each portion of our work has been placed into only one of these three frameworks for the present purposes. Numerous figures (spectra and plots) and tables summarize the voluminous data that have been generated.

Maciel, G.E.

1984-01-01

360

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

361

Sensitive and robust electrophoretic NMR: Instrumentation and experiments  

NASA Astrophysics Data System (ADS)

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.

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

2008-05-01

362

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

363

Degradation of historical paper: nondestructive analysis by the NMR-MOUSE.  

PubMed

The NMR-MOUSE is a mobile sensor for single-sided NMR inspection of organic materials which takes advantage of the principles of magnetic resonance and inside-out-NMR. Historical books dating from the 17th century were measured at different points by positioning the NMR-MOUSE on the paper. Different degrees of paper degradation can be discriminated from the regularized inverse Laplace transform of the envelope of the acquired echo signals. For the first time the degradation of historical paper was characterized entirely nondestructively by NMR. As a contribution to current preservation efforts, NMR shows great promise for future use in damage assessment of historical documents. PMID:12713971

Blümich, B; Anferova, S; Sharma, S; Segre, A L; Federici, C

2003-04-01

364

The measurement of electrophoretic mobility in surfactant systems using NMR  

NASA Astrophysics Data System (ADS)

A combined nuclear magnetic resonance (NMR) and electrophoresis method (MREP) is used for the measurement of electrophoretic mobility of charged micelles in surfactant systems. A modified NMR spin-echo pulse sequence with pulsed magnetic field gradients is employed to measure the slow flow rates encountered in electrophoresis of observation of phase shifts in the NMR spinecho. Electrophoretic mobility was determined for anionic sodium dodecyl sulphate and cationic cetyl trimethyl ammonium bromide surfactants at various concentrations. Also, measurements were made with added salt, which alters the ionic environment of the micelles. Finally, an attempt was made to study mixed surfactant systems using an extension of the MREP technique which involved Fourier analysis and observation of the phase shifts due to flow in the frequency spectrum.

Coveney, F. M.; Strange, J. H.; Smith, E. G.

365

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

366

Toward contrast-enhanced, optically-detected NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Optical detection of Nuclear Magnetic Resonance (NMR) takes place via a two-step process that relies on the interaction between optical photons and electrons on the one hand, and the hyperfine coupling between electrons and nuclear spins on the other. The latter depends on the material system under consideration while the former is dominated by the difference between the illumination and optical transition wavelengths. Here we use optical Faraday rotation to monitor nuclear spins in real time after resonant radio-frequency excitation at high-magnetic field. Comparison between inductively and optically detected NMR spectra in model sample fluids indicates that each of these mechanisms can lead to alternate forms of spectral contrast. Extension of these findings may find application in solvent suppression protocols, sensitivity-enhanced NMR of metalloproteins, or the characterization of molecular orbitals in diamagnetic systems.

Meriles, Carlos; Pagliero, Daniela

2011-03-01

367

NMR spectroscopy of RNA duplexes containing pseudouridine in supercooled water  

PubMed Central

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°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.

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

2005-01-01

368

Al/Al-oxide nanophase composites: Hardness and NMR Results  

NASA Astrophysics Data System (ADS)

Hardness and high temperature 27-Al NMR measurements of Al/Al-oxide nanophase composites produced by consolidation of nanoscale Al particles which have been passivated by exposure to air are reported. The Al/Al-oxide nanophase composite material produced has a low density, is electrically conducting and has a hardness much larger than that of metallic Al. High temperature NMR measurements show that the Al metal melts at the same temperature in all the samples, including a large-grained Al metal sample, independent of grain size and without a change in shape of the sample. The results here confirm previous thermal measurements which show that the Al metal melts without grain growth in these materials. On the other hand, the temperature for the onset of rapid atomic diffusion, as estimated from NMR line widths, shows a significant sample dependence. Heated samples exhibit a further factor of five increase in hardness and yet remain electrically conducting.

Suits, B. H.; Apte, P.

1998-03-01

369

NMR imaging of cell phone radiation absorption in brain tissue.  

PubMed

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. PMID:23248293

Gultekin, David H; Moeller, Lothar

2012-12-17

370

NMR characteristics in noncentrosymmetric Mo3Al2C  

NASA Astrophysics Data System (ADS)

We present an extensive study of the noncentrosymmetric superconductor Mo3Al2C using 27Al nuclear magnetic resonance (NMR) spectroscopy. The NMR line shapes, Knight shifts, as well as spin-lattice relaxation rates in both superconducting and normal states have been identified. In the superconducting phase, the results of the Knight shift and relaxation rate signify the existence of finite density of states, attributed to the strong antisymmetric spin-orbital coupling effect enhanced by intrinsic defects. In the normal state, peculiar changes such as the broadening of the NMR linewidth and the distinct drop of the Knight shift were discerned across a characteristic temperature of T*?196 K. Moreover, the magnitude of 1/T1T decreases markedly and develops pseudogaplike behavior below T*. We associated these anomalous features with distortions near the Al sites toward a lower symmetric structural environment, leading to the modification of electronic structures around Fermi surfaces.

Kuo, C. N.; Liu, H. F.; Lue, C. S.

2012-02-01

371

NMR-Metabolic Methodology in the Study of GM Foods  

PubMed Central

The 1H-NMR methodology used in the study of genetically modified (GM) foods is discussed. Transgenic lettuce (Lactuca sativa cv "Luxor") over-expressing the ArabidopsisKNAT1 gene is presented as a case study. Twenty-two water-soluble metabolites (amino acids, organic acids, sugars) present in leaves of conventional and GM lettuce were monitored by NMR and quantified at two developmental stages. The NMR spectra did not reveal any difference in metabolite composition between the GM lettuce and the wild type counterpart. Statistical analyses of metabolite variables highlighted metabolism variation as a function of leaf development as well as the transgene. A main effect of the transgene was in altering sugar metabolism.

Sobolev, Anatoly P.; Capitani, Donatella; Giannino, Donato; Nicolodi, Chiara; Testone, Giulio; Santoro, Flavio; Frugis, Giovanna; Iannelli, Maria A.; Mattoo, Autar K.; Brosio, Elvino; Gianferri, Raffaella; D'Amico, Irene; Mannina, Luisa

2010-01-01

372

A bioreactor for in-cell protein NMR  

NASA Astrophysics Data System (ADS)

The inside of the cell is a complex environment that is difficult to simulate when studying proteins and other molecules in vitro. We have developed a device and system that provides a controlled environment for nuclear magnetic resonance (NMR) experiments involving living cells. Our device comprises two main parts, an NMR detection region and a circulation system. The flow of medium from the bottom of the device pushes alginate encapsulated cells into the circulation chamber. In the chamber, the exchange of oxygen and nutrients occurs between the media and the encapsulated cells. When the media flow is stopped, the encapsulated cells fall back into the NMR detection region, and spectra can be acquired. We have utilized the bioreactor to study the expression of the natively disordered protein ?-synuclein, inside Escherichia coli cells.

Sharaf, Naima G.; Barnes, Christopher O.; Charlton, Lisa M.; Young, Gregory B.; Pielak, Gary J.

2010-02-01

373

Formalism for hypercomplex multidimensional NMR employing partial-component subsampling.  

PubMed

Multidimensional NMR spectroscopy typically employs phase-sensitive detection, which results in hypercomplex data (and spectra) when utilized in more than one dimension. Nonuniform sampling approaches have become commonplace in multidimensional NMR, enabling dramatic reductions in experiment time, increases in sensitivity and/or increases in resolution. In order to utilize nonuniform sampling optimally, it is necessary to characterize the relationship between the spectrum of a uniformly sampled data set and the spectrum of a subsampled data set. In this work we construct an algebra of hypercomplex numbers suitable for representing multidimensional NMR data along with partial-component nonuniform sampling (i.e. the hypercomplex components of data points are subsampled). This formalism leads to a modified DFT-Convolution relationship involving a partial-component, hypercomplex point-spread function set. The framework presented here is essential for the continued development and appropriate characterization of partial-component nonuniform sampling. PMID:23246651

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

2012-11-29

374

Automated high-resolution NMR with a sample changer  

SciTech Connect

Within the past two years, it has become possible to obtain high-resolution NMR spectra using automated commercial instrumentation. Software control of all spectrometer functions has reduced most of the tedious manual operations to typing a few computer commands or even making selections from a menu. Addition of an automatic sample changer is the next natural step in improving efficiency and sample throughput; it has a significant (and even unexpected) impact on how NMR laboratories are run and how it is taught. Such an instrument makes even sophisticated experiments routine, so that people with no previous exposure to NMR can run these experiments after a training session of an hour or less. This A/C Interface examines the impact of such instrumentation on both the academic and the industrial laboratory.

Wade, C.G.; Johnson, R.D.; Philson, S.B.; Strouse, J.; McEnroe, F.J.

1989-01-15

375

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

376

A global analysis of NMR distance constraints from the PDB.  

PubMed

Information obtained from Nuclear Magnetic Resonance (NMR) experiments is encoded as a set of constraint lists when calculating three-dimensional structures for a protein. With the amount of constraint data from the world wide Protein Data Bank (wwPDB) that is now available, it is possible to do a global, large-scale analysis using only information from the constraints, without taking the coordinate information into account. This article describes such an analysis of distance constraints from NOE data based on a set of 1834 NMR PDB entries containing 1909 protein chains. In order to best represent the quality and extent of the data that is currently deposited at the wwPDB, only the original data as deposited by the authors was used, and no attempt was made to 'clean up' and further interpret this information. Because the constraint lists provide a single set of data, and not an ensemble of structural solutions, they are easier to analyse and provide a reduced form of structural information that is relevant for NMR analysis only. The online resource resulting from this analysis ( http://www.ebi.ac.uk/msd/srv/docs/NMR/analysis/results/html/comparison.html ) makes it possible to check, for example, how often a particular contact occurs when assigning NOESY spectra, or to find out whether a particular sequence fragment is likely to be difficult to assign. In this respect it formalises information that scientists with experience in spectrum analysis are aware of but cannot necessarily quantify. The analysis described here illustrates the importance of depositing constraints (and all other possible NMR derived information) along with the structure coordinates, as this type of information can greatly assist the NMR community. PMID:17922259

Vranken, Wim

2007-10-09

377

NMR spectroscopy and imaging of macerals in Argonne premium coals  

SciTech Connect

Macerals that have been separated from two high-volatile bituminous coals from the Argonne Premium Coal Sample Program are surveyed using chemical and NMR spectroscopic techniques. Quantitative aspects of the method are discussed. Alkylation using {sup 13}C enriched methyl iodide followed by solid {sup 13}C NMR analysis was used to determine the concentrations of acidic OH and CH sites in these macerals. Also, the first successful application of nuclear magnetic resonance imaging (MRI) for spatially mapping chemically distinct regions within a Utah coal has been demonstrated. 15 refs., 5 figs., 2 tabs.

Botto, R.E.; Choi, C.Y.; Dieckman, S.L.; Gopalsami, N.; Thompson, A.R.; Tsiao, C.J.

1990-01-01

378

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

379

Observation of two N2-isobutyrylguanine tautomers by NMR spectroscopy.  

PubMed

N(2)-isobutyrylguanine was prepared by treatment of guanine with isobutyryl chloride. Two tautomers, 1,7-dihydro-2-(isobutyroyl)amino-6H-purin-6-one and 1,9-dihydro-2-(isobutyroyl)amino-6H-purin-6-one, were identified in almost 1:1 ratio in dichloromethane-dimethyl sulfoxide (1:1?v/v) by NMR spectroscopy. By using the selective-inversion experiments, enthalpy, entropy, and free energy for activation were determined. This work represents the first report of guanine tautomers observed directly by NMR spectroscopy. PMID:23166038

Yang, Lijing; Li, Jia; Simionescu, Razvan; Yan, Hongbin

2012-11-20

380

A comprehensive NMR study of cubic and hexagonal boron nitride.  

PubMed

A variety of techniques and measurements on all NMR accessible nuclei allow one to obtain a complete and precise set of chemical shift and quadrupole coupling parameters for both boron and nitrogen in cubic and hexagonal boron nitride. For hexagonal boron nitride, 11B to 15N cross polarization under magic angle sample spinning conditions is demonstrated at natural isotope abundance. The presented approach for NMR characterization of the crystalline boron nitrides should also be applicable to structurally related composite materials, nanotubes, and amorphous ceramics. PMID:9808290

Jeschke, G; Hoffbauer, W; Jansen, M

1998-08-01

381

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

382

Optical-pumping double-resonance NMR system for semiconductors  

NASA Astrophysics Data System (ADS)

We describe an optical-pumping double-resonance NMR system equipped with a single-coil double-tuning (XY) probe with an optical fiber attachment working in a helium-gas flow cryostat. The system enables simultaneous control of an infrared light and two radio-frequency fields irradiated to a sample, so that solid-state NMR techniques such as spin locking, decoupling, and cross polarization can be invoked under the optical-pumping condition. A nuclear hyperpolarization transfer experiment in optically pumped InP:Fe is presented.

Goto, Atsushi; Ohki, Shinobu; Hashi, Kenjiro; Shimizu, Tadashi

2006-09-01

383

On-cell MAS NMR: physiological clues from living cells.  

PubMed

While structural information on biomolecules is mainly obtained from purified in vitro samples, NMR can also be applied in the context of entire cells or organisms. The present study describes maturation processes in living Salmonella enterica serovar Typhimurium, a prevalent cause for human gastroenteritis. In our physiological study, we follow the composition of the O-antigen on the outer bacterial membrane with high-resolution MAS NMR spectroscopy. We detect and characterize an evolution of the O-antigen composition, in particular of the O-acetylation state of the O-antigen, a factor that can play an important role in vaccine development. PMID:23030432

Zandomeneghi, Giorgia; Ilg, Karin; Aebi, Markus; Meier, Beat H

2012-10-15

384

Quantum Gates Based on Polarization Transfer NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

We first introduce an alternative way to study the insensitive nuclei enhanced by polarization and distortionless enhancement by polarization transfer NMR experiments with the product operator descriptions for weakly coupled I (I=1/2, S=1/2) spin systems as a quantum controlled not gate and a not gate, respectively. In this framework we apply the density matrix operators obtained from the analytical descriptions of the mentioned pulse sequences by using product operator formalism step by step on the NMR spin product states represented in Dirac's notation.

Güleç, A.; Bahçeli, S.

2005-06-01

385

Advanced NMR approaches in the characterization of coal  

SciTech Connect

A considerable effort in this project during the past few months has been focussed on the development of [sup 1]H and [sup 13]C NMR imaging techniques to yield spatially-resolved chemical shift (structure) information on coal. In order to yield the chemical shift information, a solid-state NMR imaging technique must include magic-angle spinning, so rotating gradient capabilities are indicated. A [sup 13]C MAS imaging probe and a [sup 1]H MAS imaging probe and the circuitry necessary for rotating gradients have been designed and constructed. The [sup 1]H system has already produced promising preliminary results, which are briefly described in this report.

Maciel, G.E.

1992-01-01

386

NMR-based structural biology of proteins in supercooled water.  

PubMed

NMR-based structural biology of proteins can be pursued efficiently in supercooled water at temperatures well below the freezing point of water. This enables one to study protein structure, dynamics, hydration and cold denaturation in an unperturbed aqueous solution at very low temperatures. Furthermore, such studies enable one to accurately measure thermodynamic parameters associated with protein cold denaturation. Presently available approaches to acquire NMR data for supercooled aqueous protein solutions are surveyed, new insights obtained from such studies are summarized, and future perspectives are discussed. PMID:21533787

Szyperski, Thomas; Mills, Jeffrey L

2011-05-01

387

Inverse methods in two-dimensional NMR spectral analysis  

NASA Astrophysics Data System (ADS)

Solid-state NMR is a valuable technique for the study of disordered materials. Analysis of such spectra usually involves solution of so-called ill-posed inverse problems. Here we present a strategy for the analysis of two-parameter two-dimensional NMR problems and test it on 2D DECODER and DOQSY experiments. Using Monte Carlo tests, constraints are determined for the resolution and accuracy of the analysis for both experiments. The methods are finally applied to spectra of spider dragline silk, a heterogeneous solid fibrous protein.

van Beek, Jacco D.; Meier, Beat H.; Schäfer, Hartmut

2003-05-01

388

NMR STUDY OF MOLECULAR REFORIENTATION UNDER FIVEFOLD SYMMETRY SOLID PERMETHYLFERROCENE  

SciTech Connect

The ring reorientation in permethylferrocene has been studied using high resolution solid state {sup 13}C NMR. The constraints which symmetry places upon the number and types of motional parameters which may be determined from the NMR spectrum are discussed. From comparison of the experimental lineshapes in the slow reorientation temperatures range with theoretical models for random rotations and symmetry related jumps, it is concluded that the reorientation occurs as jumps between symmetry related orientations with jumps of 2{pi}/5 highly favored over 4{pi}/5. The activation energy derived for the jump process is 13.5 kjoules/mole.

Wemmer, D.E.; Ruben, D.J.; Pines, A.

1980-08-01

389

MAS PFG NMR Studies of Mixtures in Porous Materials  

NASA Astrophysics Data System (ADS)

Pulsed field gradient (PFG) and magic angle spinning (MAS) NMR techniques have been successfully combined for the study of mixture diffusion in porous materials. Using a modular setup of commercially available components, gradient pulses of up to +/-2.6 T/m can be applied coinciding with fast sample rotation at the magic angle. Methods for the proper alignment of all components are presented along with protocols for MAS PFG NMR experiments. Finally, first diffusion measurements of n-hexane and benzene being adsorbed together in the metal-organic framework MOF-5 are presented.

Gratz, Marcel; Hertel, Stefan; Wehring, Markus; Schlayer, Stefan; Stallmach, Frank; Galvosas, Petrik

2011-03-01

390

NMR study of quinolizidine alkaloids: relative configurations, conformations.  

PubMed

Extracts of fruits and leaves of Connarus paniculatus afford six quinolizidine alkaloids which were identified as piptanthine, 18-epipiptanthine, ormosanine, homoormosanine, podopetaline (monohydrochloride) and homopodopetaline on the basis of high-field NMR studies. 1D and 2D NMR experiments provide complete assignments of the (1)H and (13)C spectra. In conjunction with detection of nuclear Overhauser effects (NOESY), these results allow detailed structure characterization including determination of relative configurations for the chiral sites and conformational analysis. Exchange phenomena involving nitrogen inversion were detected. PMID:15706612

Le, Phuong Mai; Martin, Marie-Thérèse; Van Hung, Nguyen; Guénard, Daniel; Sévenet, Thierry; Platzer, Nicole

2005-04-01

391

NMR-Based Encoding and Processing of Alphanumeric Information  

NASA Astrophysics Data System (ADS)

We present here a novel experimental computing device that is based on 1H Nuclear Magnetic Resonance (NMR) readout of chemical information. This chemical encoding system utilizes two measurable parameters of homogeneous mixtures, chemical shift and peak integration, for different applications: 1) text encoding device that is based on spectral representation of a sequence of symbols, 2) encoding of 21-digit binary numbers, each represented by an NMR spectrum, and their algebraic manipulations, such as addition and subtraction, and 3) encoding of 21-digit decimal numbers.

Ratner, Tamar; Reany, Ofer; Keinan, Ehud

392

Symmetry in the design of NMR multiple-pulse sequences  

NASA Astrophysics Data System (ADS)

The symmetry principles of NMR pulse-sequence design are summarized. The discussion is guided by an analogy with tiling schemes in the decorative arts. The symmetry operations for NMR pulse sequences are discussed in terms of excitation field modifiers and temporal modifiers. The quantum operators which describe the effect of these modifiers on the excitation field spin Hamiltonian are provided. The symmetry transformations of spin propagators, and the different types of pulse-sequence elements are discussed. The common types of symmetry expansion are treated using the propagator transformations and the Euler angles for the excitation field propagators. The selection rules associated with symmetrical pulse sequences are discussed using average Hamiltonian theory.

Levitt, Malcolm H.

2008-02-01

393

Fluorinated diaminocyclopentanes as chiral sensitive NMR probes of RNA structure.  

PubMed

The supramolecular chiral recognition between rac-2a and several structured RNA leads to a distinct (19)F NMR signal splitting. The (19)F NMR analysis of the diastereomeric pairs formed upon binding of this racemic probe delivers a topological footprint of the RNA. This phenomenon can be exploited to investigate dynamic events involving structural equilibria, as demonstrated in a melting experiment. This work provides a proof of concept that small fluorinated moderate binders can act as external probes of RNA structures. PMID:20809569

Moumné, Roba; Pasco, Morgane; Prost, Elise; Lecourt, Thomas; Micouin, Laurent; Tisné, Carine

2010-09-29

394

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

2013-03-06

395

Absolute configuration and 1H NMR characterization of rosmaridiphenol diacetate.  

PubMed

The correction of patented structure 1 of rosmaridiphenol, an antioxidant isolated from rosemary, Rosmarinus officinalis, was made recently. The correct structure is proposed as 11,12-dihydroxy-8,11,13-icetexatrien-1-one (2a) based on 2D NMR data. In order to further support the structure, this work reports the single-crystal X-ray analysis, the complete (1)H NMR assignment by full spin-spin simulation, and the absolute configuration of the diacetate 2b derived via vibrational circular dicroism measurements in comparison with density functional theory calculated data. PMID:22424272

Muñoz, Marcelo A; Perez-Hernandez, Nury; Pertino, Mariano W; Schmeda-Hirschmann, Guillermo; Joseph-Nathan, Pedro

2012-03-16

396

Reduced glutathione-resisting ¹?F NMR sensors for detecting HNO.  

PubMed

The (19)F NMR probes for the HNO detection are reported. We synthesized the probe molecules with the paramagnetic Cu(II) complex and fluorine atoms using a cubic silsesquioxane. By using the magnetism changes of the Cu(II) to Cu(I) in the complex by the reduction with HNO, the (19)F NMR signal intensities of the probe increased. Noteworthily, our probes have superior resistance to reduced glutathione which is the major intracellular molecule to maintain the reductive environment and the competitor in the reduction of Cu(II) against HNO. PMID:22789704

Kitamura, Narufumi; Hiraoka, Tatsuhiro; Tanaka, Kazuo; Chujo, Yoshiki

2012-06-15

397

Characterization of Plasma Polymerized Hydrocarbons Using CP-MAS Carbon-13 NMR.  

National Technical Information Service (NTIS)

Plasma polymerized hydrocarbons made from ethane and methane were produced under different reactor conditions and probed by solid-state carbon-13 nuclear magnetic resonance (NMR) with cross-polarization and magic angle sample spinning. NMR experiments pro...

D. L. Cho F. D. Blum H. Yasuda R. J. Gambogi

1991-01-01

398

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 ...

399

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

400

Structures of rhodium complexes containing substituted hydrazines from multinuclear NMR studies  

Microsoft Academic Search

Natural abundance 15N NMR measurements, using the INEPT pulse sequence, have been used in conjunction with 31P NMR studies to elucidate the structures of several rhodium complexes containing monomethyl- and 1,1-dimethyl hydrazine.

Brian T. Heaton; Chacko Jacob; Jeyagowry Ratnam

1995-01-01

401

A comparison of capillary-scale LC-NMR with alternative techniques: spectroscopic and practical considerations.  

PubMed

Experimental and practical details for the use of capillary LC (CapLC)-NMR are reported. The capillary NMR probe has high sensitivity and excellent flow characteristics and we found CapLC-NMR to be best suited to samples that are truly mass limited. CapLC-NMR relies on good capillary-scale chromatography where highly concentrated peaks with a volume closely matched to the NMR flow cell are achievable. Provided that the loading capacity of the capillary column is not limiting, the combination of high sensitivity and high solvent suppression quality makes CapLC-NMR an excellent choice. For many real samples, however, the loading is limiting and we found the combination of LC-SPE-MS-NMR with a cryoprobe enables more material to be purified for NMR analysis, while retaining sensitivity. PMID:16049949

Lewis, Richard J; Bernstein, Michael A; Duncan, Sara J; Sleigh, Chris J

2005-09-01

402

Niobium oxide acidity studied by proton broad-line NMR at 4 K and MAS NMR at room temperature  

Microsoft Academic Search

The quantitative study of the Brønsted acidity of niobic acid (Nb2O5·xH2O) using broad-line1H NMR at 4 K has been performed by interacting niobic acid, pretreated at 573 K under vacuum, with water molecules. The number of oxyprotonated species (H3O+ and H2O...HO species formed, unreacted acidic OH groups or excess H2O molecules) deduced from the simulations of the broad-line1H NMR spectra

Patrice Batamack; Robert Vincent; Jacques Fraissard

1996-01-01

403

A high?resolution solid?state NMR study on nano?structured HZSM?5 zeolite  

Microsoft Academic Search

Variations in the structure and acidity properties of HZSM?5 zeolites with reduction in crystal sizes down to nanoscale (less\\u000a than 100 nm) have been investigated by XRD, TEM and solid?state NMR with a system capable of in situ sample pretreatment.\\u000a As evidenced by a combination of 27Al MAS NMR, 29Si MAS, CP\\/MAS NMR and 1H MAS NMR techniques, the downsize

Weiping Zhang; Xinhe Bao; Xinwen Guo; Xiangsheng Wang

1999-01-01

404

Vibrational, NMR spectral studies of 2-furoic hydrazide by DFT and ab initio HF methods  

NASA Astrophysics Data System (ADS)

The Fourier transform infrared spectra, 1H NMR and 13C NMR spectra of 2-furoic hydrazide have been recorded. Optimized geometry, frequency and intensity of the vibrational bands of 2-furoic hydrazide were obtained by the density functional theory (DFT) and ab initio levels of theory and also 1H NMR, 13C NMR chemical shifts were calculated using 6-31G+(d,p) basis sets. The theoretical values were compared with experimental values.

Vimalraj, V.; Vijayalakshmi, S.; Umayaparvathi, S.; Krishnan, Akhil. R.

2011-02-01

405

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

406

Hydrodynamic shifts in the NMR spectrum of 3B  

NASA Astrophysics Data System (ADS)

We have measured the flow-induced shift in the NMR spectrum of 3B. Above a temperature-independent critical velocity, the absorption line is observed to shift to higher frequencies as the flow is increased, in qualitative agreement with the theory of textural deformation in the presence of flow due to Fetter.

Hutchins, J.; Brewer, D. F.; Kruppa, D.

1985-09-01

407

NMR Studies of Glassy and Crystalline Fast Ion Conductors  

Microsoft Academic Search

The ionic conductivity of fast ion conducting lithium fluoroborate and lithium chloroborate glasses was studied using ('7)Li and ('19)F NMR. Magnetic tagging studies demonstrate that the Li('+) ion is responsible for the high ionic conductivity of these materials. Activation energies were also obtained for this motion, and it is observed that a distribution of activation energies exists in the lithium

David Eric Hintenlang

1985-01-01

408

A new field-tracking NMR magnetometer system  

Microsoft Academic Search

An automatic NMR magnetometer covering the magnetic field range 0.1-3.2 T is described. Instead of continuous tracking of the magnetic field by a conventional feedback loop technique, a new approach to triangular frequency modulation of the marginal oscillator is used in this instrument, ensuring symmetrical frequency deviation about the resonance position. Direct digital display of the magnetic field value is

J. Kubiak; M. Ostafin; G. Kienitz

1979-01-01

409

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

410

The application of NMR techniques to bacterial adhesins.  

PubMed

Extracellular adhesins frequently compose large, highly-ordered structural assemblies that project away from the bacterial surface. These assemblies, known as pili or fimbriae, are rod-like polymeric structures that in some cases can extend up to several micrometers from the cell surface. Because these adhesin structures are critical to bacterial colonization of host cell surfaces, there is an incentive to understand their structure, assembly and mechanism of host cell attachment. Various methods in Nuclear Magnetic Resonance (NMR) spectroscopy have been used to address these topics, yielding structural information at the atomic level. Also, new methods in solid-state NMR spectroscopy have thus far been under-utilized in the study of large adhesin structures and offer a powerful approach to overcoming problems with crystallization to better understand the structures of these complexes. The following is a brief overview of the contributions of NMR to the study of bacterial adhesins with an emphasis on the future potential of solid-state NMR. PMID:21557068

Shewmaker, Frank

2011-01-01

411

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

412

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

413

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

2013-06-27

414

NMR frequency and magnetic dipole moment of 3He nucleus  

Microsoft Academic Search

We present new gas-phase NMR spectra which relate the resonance frequency of 3He nucleus to the resonance frequency of the proton in tetramethylsilane (TMS). We discuss the dependence of 3He resonance frequency on the density of the solvent gas, and we consider in detail the absolute shielding scales of both nuclei. Finally, we analyse the accuracy of the results, using

Karol Jackowski; Micha? Jaszu?ski; Bohdan Kamienski; Marcin Wilczek

2008-01-01

415

Water transfer analysis in pork meat supported by NMR imaging  

Microsoft Academic Search

NMR proton density imaging was used to study isothermal and unidirectional drying of pork semi membranosus muscle samples at temperatures of 12, 16 and 20 °C. An independent calibration of the transversal relaxation time T2 as a function of the moisture content was carried out to convert the signal amplitude into moisture content. Due to spatial heterogeneity in drying, 2D

M. A. Ruiz-Cabrera; P. Gou; L. Foucat; J. P. Renou; J. D. Daudin

2004-01-01

416

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

417

NMR of paramagnetic complexes of radicals with organic ligands  

Microsoft Academic Search

Complex formation between stable amine oxide radicals and organic molecules generates paramagnetic shifts in the NMR spectra of the ligand nuclei and corresponding line broadening in these spectra. Analysis of the paramagnetic shifts yielded the magnitudes and signs of the isotopic hyperfine interaction constants for the protons in the radical complexes with hydroxyl-containing ligands. The equilibrium constants for the complex

N. A. Sysoeva; A. L. Buchachenko

1972-01-01

418

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

2009-12-03

419

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

420

NMR in rotating magnetic fields: Magic angle field spinning  

SciTech Connect

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 the spectral resolution by averaging away rank 2 anisotropic spin interactions thereby producing isotropic-like spectra with resolved chemical shifts and scalar couplings. Andrew proposed that it should be possible to induce similar effects in a static sample if the direction of the magnetic field is varied, e.g., magic-angle rotation of the B0 field (B0-MAS) and this has been recently demonstrated using electromagnetic field rotation. Here we discuss on the possibilities to perform field rotation using alternative hardware, together with spectroscopic methods to recover isotropic resolution even in cases where the field is not rotating at the magic angle. Extension to higher magnetic fields would be beneficial in situations where the physical manipulation of the sample is inconvenient or impossible. Such situations occur often in materials or biomedical samples where ''ex-situ'' NMR spectroscopy and imaging analysis is needed.

Sakellariou, D.; Meriles, C.; Martin, R.; Pines, A.

2004-09-10

421

1H NMR analysis of sporopollenin from Typha Angustifolia  

Microsoft Academic Search

The first analysis of sporopollenin using 1H NMR-techniques revealed the presence of four phenolic compounds in different amounts. The phenolic compounds are tri- or tetrasubstituted. The sporopollenin was isolated and purified from Typha angustifolia by an enzymatic procedure, followed by extraction with organic solvents.

Friedhelm Ahlers; Ina Thom; Jörg Lambert; Rüdiger Kuckuk; Rolf Wiermann

1999-01-01

422

Satellite NMR in Cu Doped with Transition Impurities.  

National Technical Information Service (NTIS)

Measurements were made of the conduction electron spin magnetization density, M/sub sigma/(R vector) near iron group atoms (Sc through Ni) in Cu. M/sub sigma/(R vector) produces an additional effective local field which shifts the NMR frequency of nearby ...

C. P. Slichter

1979-01-01

423

Pulsed gas control for NMR spinner speed adjustment  

Microsoft Academic Search

A system for controlling the spin of an NMR sample is described comprising: means for containing a source of gas, means for translating gas flow into sample spin. The on\\/off gas valve with electrical control means. The valve controls gas flow from the means for containing a source of gas to the means for translating gas flow into sample spin.

Hlavka

1987-01-01

424

NMR Diffusion Diffraction and Diffusion Interference from Cells  

Microsoft Academic Search

Pulsed field gradient spin-echo (PGSE) NMR spectroscopy is the definitive means for measuring translational motion of molecules in free solution and in heterogeneous systems. A unique 'twist' on the method is that in some systems in which diffusion is restricted the PGSE experiment yields information on the geometrical properties of the confining boundaries. When applied to red blood cells (RBCs)

Philip W. Kuchel; Guilhem Pages

2007-01-01

425

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

426

The pressure dependence of molecular dynamics measured by NMR  

NASA Astrophysics Data System (ADS)

NMR techniques have been developed to study methyl group reorientation and hydrogen bond dynamics as a function of hydrostatic pressure. This paper briefly reviews some earlier work and presents new results of the pressure dependence of the reorientation of two distinct methyl groups in methyl ethyl ketone.

McDonald, P. J.; Vijayaraghavan, D.; Debenham, P. M.; Horsewill, A. J.

1994-10-01

427

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

428

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

429

Calculation of NMR lineshapes for Ba-Al-Ge clathrates  

NASA Astrophysics Data System (ADS)

Clathrates consist of Si, Ge, or Sn cages in a crystalline framework, with guest atoms inside the cages. They have gained interest due to thermoelectric properties suitable for potential device application. To understand Al substitutional configurations, we calculated Al NMR line shapes for several structures with compositions Ba8Ge46-x-yAlxy for x=3,8,11,12,16,24; y=2,3; where represents a vacancy. The results were obtained by calculating Electric Field Gradients (EFG) for Al sites of type-I clathrates assuming an ordered superstructure of vacancies and framework occupation. We used ab initio methods in the Generalized Gradient Approximation as implemented by the WIEN2k program, and used the results to simulate NMR lineshapes numerically. These were compared to our previously reported NMR lineshapes. In the case of Ba8Ge31Al123 four Al sites in the superstructure include two sites with small EFG where the vacancy is far away and two sites with large EFG with a vacancy adjacent to Al. Assuming a larger Knight shift for sites next to vacancies, we obtain good agreement with NMR experimental results for reduced-Al Ba8Ge34Al12, while for the Zintl phase Ba8Ge30Al16 we obtain good agreement with no spontaneous vacancies. We infer that Al prefers locations close to vacancies rather than random occupation. This work was supported by Robert A. Welch Foundation (Grant A-1526).

Rodriguez, Sergio; Gou, Weiping; Ross, Joseph

2008-10-01

430

Developments in chlorine detection in concrete using NMR  

NASA Astrophysics Data System (ADS)

Monitoring chloride concentration and transport in concrete structures susceptible to corrosion of embedded steel reinforcement is a challenge as difficult as it is important. An embedded sensor based on nuclear magnetic resonance (NMR) would be a good solution to the problem because it would make a non-destructive atom-specific measurement of the presence and concentration of chloride. The important question is the scale of the device required to detect the chloride. Laboratory experiments to detect chloride in a cement matrix using pulse-NMR were conducted to assess the potential of this application; they provided a basis for projecting the scale of a device that would have a good chance of success. The coils were cm-scale and the magnetic field was 2.35 T. NMR signals were obtained from both aqueous chloride solution and samples of both regular and white portland cement. The experiments demonstrated that the signal-to-noise ratio (SNR) for a cm-scale cement sample volume is so small, even after averaging, that sample volumes much lower than that are unlikely to produce measurable signals at fields of 1 T or below. Thus the potential for realizing an embedded NMR-based sensor including the magnet is low. Parametric studies identify feasible alternative coil diameters and magnetic field strengths for detecting chloride ion concentrations in hardened concrete.

Yun, Andrew H.; Patton, Mark E.; Garrett, James H.; Fedder, Gary K.; Frederick, Kevin M.; Hsu, Jung-Jiin; Lowe, Irving J.; Oppenheim, Irving J.; Sides, Paul J.

2002-06-01

431

Protein Structure Determination Using Protein Threading and Sparse NMR Data.  

National Technical Information Service (NTIS)

It is well known that the NMR method for protein structure determination applies to small proteins and that its effectiveness decreases very rapidly as the molecular weight increases beyond about 30 kD. We have recently developed a method for protein stru...

O. H. Crawford J. R. Einstein D. Xu Y. Xu

1999-01-01

432

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

433

Automated analysis of NMR assignments and structures for proteins  

Microsoft Academic Search

Recent developments in protein NMR technology have provided spectral data that are highly amenable to analysis by advanced computer software systems. Specific data collection strategies, coupled with these computer programs, allow automated analysis of extensive backbone and sidechain resonance assignments and three-dimensional structures for proteins of 50 to 200 amino acids.

Hunter NB Moseley; Gaetano T Montelione

1999-01-01

434

Using NMR to Determine Protein Structure in Solution  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) is a marvelous spectroscopic technique that chemists, physicists, and biochemists routinely employ for their research around the world. This year half of the Nobel Prize for chemistry went to Kurt Wüthrich, who was recognized for the development of NMR-based techniques that lead to the structure determination of biomolecules in solution. In addition to implementing novel pulse sequences and software packages, Wüthrich also applied his methods to several biological systems of key importance to human health. These include the prion protein, which is heavily involved in the spongiform encephalopathy (best known as 'mad cow disease'), which recently caused numerous human deaths, particularly in the UK, due to ingestion of contaminated meat. Transverse relaxation optimized spectroscopy (TROSY) is the most intriguing new NMR method recently developed by Wüthrich and coworkers. This and other closely related pulse sequences promise to play a pivotal role in the extension of NMR to the conformational analysis of very large (up to the megadalton range) macromolecules and macromolecular complexes. More exciting new developments are expected in the near future.

Cavagnero, Silvia

2003-02-01

435

Profiling formulated monoclonal antibodies by (1)h NMR spectroscopy.  

PubMed

Nuclear magnetic resonance (NMR) is arguably the most direct methodology for characterizing the higher-order structure of proteins in solution. Structural characterization of proteins by NMR typically utilizes heteronuclear experiments. However, for formulated monoclonal antibody (mAb) therapeutics, the use of these approaches is not currently tenable due to the requirements of isotope labeling, the large size of the proteins, and the restraints imposed by various formulations. Here, we present a new strategy to characterize formulated mAbs using (1)H NMR. This method, based on the pulsed field gradient stimulated echo (PGSTE) experiment, facilitates the use of (1)H NMR to generate highly resolved spectra of intact mAbs in their formulation buffers. This method of data acquisition, along with postacquisition signal processing, allows the generation of structural and hydrodynamic profiles of antibodies. We demonstrate how variation of the PGSTE pulse sequence parameters allows proton relaxation rates and relative diffusion coefficients to be obtained in a simple fashion. This new methodology can be used as a robust way to compare and characterize mAb therapeutics. PMID:24006877

Poppe, Leszek; Jordan, John B; Lawson, Ken; Jerums, Matthew; Apostol, Izydor; Schnier, Paul D

2013-09-24

436

Study of cultured fibroblasts in vivo using NMR  

SciTech Connect

The goal of this thesis was to study the compartmentation of phosphorylated glycolytic intermediates in intact Chicken Embryo Fibroblasts (CEFs) using /sup 31/P NMR at 109 MHz. Because glycolysis is regulated differently in normal and virally transformed CEFs, NMR experiments were performed on both types of cells. A technique for maintaining functional cells at high densities in an NMR magnet is described. Signals were detected from cytoplasmic inorganic phosphate (P/sub i/), ATP, NAD, NADH, phosphorylcholine and phosphorylethanolamine. The effect of external glucose on cytoplasmic pools of phosphates was studied. However, experiments with /sup 32/P labelled P/sub i/ showed that as the concentration of glucose in the medium was increased, the amount of phosphate sequestered in the cells increased. They conclude that there is a pool of P/sub i/ which is not detected by high resolution of NMR and that the size of this pool increases as the rate of glycolysis increases. These effects were found only in cultured cells; the data for transformed and normal cells were similar. Longitudinal relaxation times of intracellular phosphates in normal, transformed, and primary CEFs were measured.

Karczmar, G.S.

1984-01-01

437

Very Thin Shim Coils for an NMR Probe.  

National Technical Information Service (NTIS)

In a previous report (AERE-R 7849 (1974)) which described the manufacture of a transverse quadrupole shim coil for the Varian HR 220 n.m.r. spectrometer, consideration was given to the design of coils which could be used on earlier models of the instrumen...

C. A. Baker

1975-01-01

438

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

439

Evaluation of Composites Miscibility by Low Field NMR  

Microsoft Academic Search

Solid state nuclear magnetic resonance (NMR) is a powerful technique to analyze polymer composites. The use of proton relaxation data to evaluate the dispersity of the dispersion phase in the composite and its homogeneity are very wide. In this work PVC\\/silica composites were prepared using different ratios to obtain a new material to be used in chromatograph column for separation

Maria Inês B. Tavares; Otávio Ferreira; Mônica Preto; Eduardo Miguez; Igor L. Soares; Edemilson P. da Silva

2007-01-01

440

Modeling (21) Ne 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

2013-08-23

441

Determination of Membrane Protein Structure by Rotational Resonance NMR: Bacteriorhodopsin  

Microsoft Academic Search

Rotationally resonant magnetization exchange, a new nuclear magnetic resonance (NMR) technique for measuring internuclear distances between like spins in solids, was used to determine the distance between the C-8 and C-18 carbons of retinal in two model compounds and in the membrane protein bacteriorhodopsin. Magnetization transfer between inequivalent spins with an isotropic shift separation, delta, is driven by magic angle

F. Creuzet; A. McDermott; R. Gebhard; K. van der Hoef; M. B. Spijker-Assink; J. Herzfeld; J. Lugtenburg; M. H. Levitt; R. G. Griffin

1991-01-01

442

Ancient Roman wall paintings mapped nondestructively by portable NMR.  

PubMed

The stratigraphies of decorated walls in ancient Herculaneum, Italy, were analyzed by single-sided (1)H NMR. A large version of the NMR-MOUSE® with a maximum penetration depth of 25 mm was used to map proton density profiles at different positions of the Mosaic of Neptune and Amphitrite showing considerable differences between different tesserae and the mortar bed at different times of the year. In the House of the Black Room, different mortar layers were observed on painted walls as well as different proton content in different areas due to different moisture levels and different conservation treatments. The proton density profiles of the differently treated areas indicated that one method leads to higher moisture content than the other. Untreated wall paintings from different times were profiled in a recently excavated room at the Villa of the Papyri showing two different types of mortar layer structures which identify two different techniques of preparing the walls for painting. Reflectance Fourier mid-infrared spectroscopy and in situ X-ray fluorescence measurements complemented the NMR measurements and provided additional insight into the identification of organic coatings as well as the nature of the pigments used, respectively. The information acquired nondestructively by NMR is valued for elaborating conservation strategies and for identifying different schools of craftsmen who prepared the mortar supports of the wall paintings. PMID:21713419

Haber, Agnes; Blümich, Bernhard; Souvorova, Daria; Del Federico, Eleonora

2011-06-29

443

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

444

NMR Spectroscopy and Protein Structure Determination: Applications to Drug Discovery and Development  

Microsoft Academic Search

Recent technological advances in NMR methods and instrumentation are having a significant impact in structural biology. These innovations are also impacting pharmaceutical biotechnology as it is now possible to use NMR spectroscopy to rapidly characterize a growing number of prospective protein drugs and protein drug targets. This review provides a general summary of how solution-state NMR can be used to

David Wishart

2005-01-01

445

The Effect of Ergosterol on Dipalmitoylphosphatidylcholine Bilayers: A Deuterium NMR and Calorimetric Study  

Microsoft Academic Search

We have studied the effect of ergosterol, an important component of fungal plasma membranes, on the physical properties of dipalmitoylphosphatidylcholine (DPPC) multibilayers using deuterium nuclear magnetic resonance (2H NMR) and differential scanning calorimetry (DSC). For the 2H NMR experiments the sn-1 chain of DPPC was perdeuterated and NMR spectra were taken as a function of temperature and ergosterol concentration. The

Ya-Wei Hsueh; Kyle Gilbert; C. Trandum; M. Zuckermann; Jenifer Thewalt

2005-01-01

446

/Sup 13/C-NMR Assignment, Structure, and Dynamics of Deoxyoligonucleotides.  

National Technical Information Service (NTIS)

The unique spectral properties of /sup 13/C-NMR for studying nucleic acids and some of the important features of /sup 13/C-NMR in oligonucleotide studies are demostrated. The main difficulty in studying oligonucleotides by /sup 13/C-NMR and recent improve...

N. Zanatta P. N. Borer G. C. Levy

1986-01-01

447

Field Demonstration of Slim-hole Borehole Nuclear Magnetic Resonance (NMR) Logging Tool for Groundwater Investigations  

Microsoft Academic Search

Nuclear magnetic resonance (NMR) methods provide estimates of free and bound water content and hydraulic conductivity, which are critically important for groundwater investigations. Borehole NMR tools have been available and widely used in the oil industry for decades, but only recently have been designed for small diameter boreholes typical of groundwater investigations. Field tests of an 89-mm-diameter borehole NMR logging

D. Walsh; P. Turner; I. Frid; R. Shelby; E. D. Grunewald; E. Magnuson; J. J. Butler; C. D. Johnson; J. C. Cannia; D. A. Woodward; K. H. Williams

2010-01-01

448

Non Destructive Testing of Thermoplastic Composites by NMR Imaging and Localised Spectroscopy  

Microsoft Academic Search

The application of NMR methods to the non-destructive testing of thermoplastic composites is discussed. NMR imaging of the polymer matrix is restricted to the detection of defects in excess of 5 mm using standard instrumentation. Higher resolution can be achieved by imaging the matrix at high temperatures or by more sophisticated NMR procedures with the practical limit of 0.1 mm

Nigel J. Clayden; Peter Jackson

1994-01-01

449

Structure elucidation and complete NMR spectral assignments of new furostanol glycosides from Solanum torvum.  

PubMed

Two new furostanol glycosides, torvosides O (1) and P (2), were isolated from leaves of Solanum torvum. Their structures were completely and unambiguously assigned by one- and two-dimensional NMR techniques ((1)H NMR, (13)C NMR, TOCSY, HSQC, ROESY and HMBC), ESI-MS spectrometry and chemical methods. PMID:19544362

Lu, Yuanyuan; Luo, Jianguang; Kong, Lingyi

2009-09-01

450

In?situ NMR characterization of pyrolysis oil during accelerated aging.  

PubMed

COMING OF AGE: A method for investigating the accelerated aging of biomass pyrolysis oils is reported. The?in situ NMR investigation, done by using quantitative ¹H, ¹³C?NMR and heteronuclear single-quantum correlation (HSQC)-NMR techniques, reveals the chemical structural changes of pyrolysis oil during the aging process, providing insight into the mechanism of aging process. PMID:22888014

Ben, Haoxi; Ragauskas, Arthur J

2012-08-07

451

Visualization of cerebral and vascular abnormalities by NMR imaging. The effects of imaging parameters on contrast  

SciTech Connect

The relationship between data acquisition parameters and contrast in nuclear magnetic resonance (NMR) images was studied. NMR imaging by the pulse echo technique selectively enhanced intracranial abnormalities; imaging by the inversion recovery technique heightened the difference between cerebral gray and white matter. Using a blood flow model, the authors also showed that NMR imaging of flow in major vessels is possible.

Crooks, L.E. (Univ. of California, San Francisco); Mills, C.M.; Davis, P.L.; Brant-Zawadzki, M.; Hoenninger, J.; Arakawa, M.; Watts, J.; Kaufman, L.

1982-09-01

452

Field Experiment Provides Ground Truth for Surface NMR Measurement  

NASA Astrophysics Data System (ADS)

Effective and sustainable long-term management of fresh water resources requires accurate information about the availability of water in groundwater aquifers. Proton Nuclear Magnetic Resonance (NMR) can provide a direct link to the presence of water in the pore space of geological materials through the detection of the nuclear magnetization of the hydrogen nuclei (protons) in the pore water. Of interest for groundwater applications is the measurement of the proton-NMR relaxation time constant, referred to as T2. This parameter is sensitive to the geometry of the water-filled pore space and can be related to the hydraulic conductivity. NMR logging instruments, which have been available since the 1980’s, provide direct measurements of T2 in boreholes. Surface NMR (SNMR) is a non-invasive geophysical method that uses a loop of wire on the surface to probe the NMR properties of groundwater aquifers to a depth of ~100 m, without the need for the drilling of boreholes. SNMR provides reliable measurements of a different NMR time constant referred to as T2*, that is related to, but not necessarily equivalent to, T2. The relationship between T2* and T2 is likely to depend upon the physical environment and the composition of the sampled material. In order to advance the use of SNMR as a non-invasive means of characterizing groundwater aquifers, we must answer the fundamental question: When probing a groundwater aquifer, what information is provided by T2*, the time constant measured with SNMR? Our approach was to conduct a field experiment in Nebraska, in an area underlain by the Quaternary Alluvium and Tertiary Ogallala aquifers. We first used SNMR to obtain a 1D profile of T2* to a depth of ~60 m. We then drilled a well inside the area of the SNMR loop, to a depth of ~150 m, and used the drill cuttings to describe the composition of the geologic material at the site. The borehole was kept open for 2 days to acquire logging NMR T2 measurements over the total depth. Three months later, borehole NMR T2 measurements were repeated with a second instrument; and logging measurements were made of the ambient magnetic field. Comparison of the three measurements of NMR relaxation show that T2* at this site is affected by inhomogeneity in the background magnetic field; this effect is most pronounced in sand and gravel units where dephasing, rather than surface relaxation, dominates the NMR response. When the borehole T2 measurements are transformed to T2*, by incorporating a term to account for this effect, we find good agreement between the two forms of measurement over the investigated depth range. The ability to ground truth the SNMR measurement has advanced our understanding of the time constant measured by SNMR, T2*, and its relationship to pore-scale properties. This is a critical step in developing SNMR as a reliable geophysical method for evaluation of groundwater resources.

Knight, R. J.; Abraham, J. D.; Cannia, J. C.; Dlubac, K. I.; Grau, B.; Grunewald, E. D.; Irons, T.; Song, Y.; Walsh, D.

2010-12-01

453

1H-NMR and 13C-NMR lipid profiles of human renal tissues.  

PubMed

Lipids from human renal tissues are studied by means of (1)H- and (13)C-NMR spectroscopy. The total lipid fractions obtained from healthy kidneys, malignant renal cell carcinomas, and benign oncocytomas are characterized and analyzed to elucidate the main differences between the functional and neoplastic tissues. In all cases the lipid components are well identified. The healthy kidney is characterized by high amounts of triglycerides and the presence of cholesterol in its free form. On the contrary, renal cell carcinomas contain high amounts of cholesterol that are almost completely esterified as oleate, suggesting an intracellular localization of the cholesteryl esters synthesis. Cholesteryl esters are considered markers of renal cell carcinomas, thus supporting recent theories that these compounds play a leading role in cell proliferation. Oncocytomas are particularly rich in phosphatidylcholine and, analogous to the healthy kidney, are completely lacking in cholesteryl esters. Healthy kidneys and oncocytomas appear to have other similarities if compared with renal cell carcinomas: a very high fatty acyl/cholesterol ratio, the presence of dolichols, and a higher grade of unsaturation. The (13)C data suggest a new method for the direct evaluation of the saturated/unsaturated fatty acyl ratio. PMID:12583011

Tugnoli, V; Bottura, G; Fini, G; Reggiani, A; Tinti, A; Trinchero, A; Tosi, M R

2003-01-01

454

Study of correlations in molecular motion by multiple quantum NMR  

SciTech Connect

Nuclear magnetic resonance is a very useful tool for characterizing molecular configurations through the measurement of transition frequencies and dipolar couplings. The measurement of spectral lineshapes, spin-lattice relaxation times, and transverse relaxation times also provide us with valuable information about correlations in molecular motion. The new technique of multiple quantum nuclear magnetic resonance has numerous advantages over the conventional single quantum NMR techniques in obtaining information about static and dynamic interactions of coupled spin systems. In the first two chapters, the theoretical background of spin Hamiltonians and the density matrix formalism of multiple quantum NMR is discussed. The creation and detection of multiple quantum coherence by multiple pulse sequence are discussed. Prototype multiple quantum spectra of oriented benzene are presented. Redfield relaxation theory and the application of multiple quantum NMR to the study of correlations in fluctuations are presented. A specific example of an oriented methyl group relaxed by paramagnetic impurities is studied in detail. The study of possible correlated motion between two coupled methyl groups by multiple quantum NMR is presented. For a six spin system it is shown that the four-quantum spectrum is sensitive to two-body correlations, and serves a ready test of correlated motion. The study of the spin-lattice dynamics of orienting or tunneling methyl groups (CH/sub 3/ and CD/sub 3/) at low temperatures is presented. The anisotropic spin-lattice relaxation of deuterated hexamethylbenzene, caused by the sixfold reorientation of the molecules, is investigated, and the NMR spectrometers and other experimental details are discussed.

Tang, J.H.

1981-11-01

455

Recent progress in NMR/MRI in petroleum applications  

NASA Astrophysics Data System (ADS)

NMR has become an important technique for characterization of porous materials. In particular, its importance in petroleum exploration has been enhanced by the recent progress in NMR well-logging techniques and instruments. Such advanced techniques are increasing being accepted as a valuable service especially in deep-sea exploration. This paper will outline the recent progress of MR techniques at Schlumberger-Doll Research. Well-logging - The second generation NMR well-logging tool and the 2D NMR methods (D-T2, etc) enable measurements at several depths from the well bore allowing a one-dimensional profiling of the fluid. Such data have allowed quantification of fluid invasion during drilling, obtaining the properties of native fluids and identifying oil/gas zones. MRI- Rocks from oil reservoirs are heterogeneous (e.g. large range of pore sizes and porosity variation) due to the complex geological and geochemical histories. The spatial pattern of the heterogeneity has not been well studied. We have developed several NMR techniques to quantify pore length scale previously. In order to predict flow over a large length scale, it is necessary to determine spatial heterogeneity and pore connectivity over the relevant size. We have performed MRI on a series of carbonate rocks and found interesting patterns of the heterogeneity characteristics. Mathematics - It is well known that the Laplace inversion is non-unique and the resulting spectrum can be strongly dependent on the prior constraints, specific algorithm and noise. However, the different spectra can all be solutions consistent with data. It would be useful to have a robust criterion -- independent of algorithms -- to determine the properties of the resulting spectrum. Several methods will be described to examine the statistics of the solutions, uncertainty of the spectrum and its integrals and resolution.

Song, Yi-Qiao

2007-03-01

456

Sb-doped PbTe: An NMR Perspective  

NASA Astrophysics Data System (ADS)

In PbTe, Sb as a dopant can occupy either Pb or Te sites. To understand the effect of Sb on the local charge-carrier concentration in both cases, we have studied high-resolution ^125Te and ^207Pb NMR spectra of Pb1-xSbxTe, PbSbxTe1-x, and n- and p-type PbTe samples. The spectra of Pb0.9975Sb0.0025Te and PbSb0.0025Te0.9975 have distinctly different resonance frequencies due to Knight shifts and chemical shifts produced by Sb at Pb or Te sites. Pb0.9975Sb0.0025Te is n-type while in PbSb0.0025Te0.9975 both n- and p-type are found. NMR spectra and spin-lattice T1 relaxation of ^207Pb nuclei in PbSb0.0025Te0.9975, which are sensitive to the hyperfine interaction between charge carriers and NMR nuclei, reveal at least four components, which reflect electronic inhomogeneity of the sample. The local carrier concentrations estimated from T1 NMR varies from n<3x10^17 to p˜10^19 cm-3. These multiple components help rationalize the complex temperature dependence of the thermopower of PbSb0.0025Te0.9975. However, comparison with Hall and Seebeck effects data indicates that some NMR signals are due to localized electron states, which do not directly contribute to transport.

Levin, E. M.; Schmidt-Rohr, K.; Jaworski, C. M.; Heremans, J. P.

2010-03-01

457

Rapid protein fold determination using unassigned NMR data.  

PubMed

Experimental structure determination by x-ray crystallography and NMR spectroscopy is slow and time-consuming compared with the rate at which new protein sequences are being identified. NMR spectroscopy has the advantage of rapidly providing the structurally relevant information in the form of unassigned chemical shifts (CSs), intensities of NOESY crosspeaks [nuclear Overhauser effects (NOEs)], and residual dipolar couplings (RDCs), but use of these data are limited by the time and effort needed to assign individual resonances to specific atoms. Here, we develop a method for generating low-resolution protein structures by using unassigned NMR data that relies on the de novo protein structure prediction algorithm, rosetta [Simons, K. T., Kooperberg, C., Huang, E. & Baker, D. (1997) J. Mol. Biol. 268, 209-225] and a Monte Carlo procedure that searches for the assignment of resonances to atoms that produces the best fit of the experimental NMR data to a candidate 3D structure. A large ensemble of models is generated from sequence information alone by using rosetta, an optimal assignment is identified for each model, and the models are then ranked based on their fit with the NMR data assuming the identified assignments. The method was tested on nine protein sequences between 56 and 140 amino acids and published CS, NOE, and RDC data. The procedure yielded models with rms deviations between 3 and 6 A, and, in four of the nine cases, the partial assignments obtained by the method could be used to refine the structures to high resolution (0.6-1.8 A) by repeated cycles of structure generation guided by the partial assignments, followed by reassignment using the newly generated models. PMID:14668443

Meiler, Jens; Baker, David

2003-12-10

458

SPE-NMR metabolite sub-profiling of urine.  

PubMed

NMR-based metabolite profiling of urine is a fast and reproducible method for detection of numerous metabolites with diverse chemical properties. However, signal overlap in the (1)H NMR profiles of human urine may hamper quantification and identification of metabolites. Therefore, a new method has been developed using automated solid-phase extraction (SPE) combined with NMR metabolite profiling. SPE-NMR of urine resulted in three fractions with complementary and reproducible sub-profiles. The sub-profile from the wash fraction (100 % water) contained polar metabolites; that from the first eluted fraction (10 % methanol-90 % water) semi-polar metabolites; and that from the second eluted fraction (100 % methanol) aromatic metabolites. The method was validated by analysis of urine samples collected from a crossover human nutritional intervention trial in which healthy volunteers consumed capsules containing a polyphenol-rich mixture of red wine and grape juice extract (WGM), the same polyphenol mixture dissolved in a soy drink (WGM_Soy), or a placebo (PLA), over a period of five days. Consumption of WGM clearly increased urinary excretion of 4-hydroxyhippuric acid, hippuric acid, 3-hydroxyphenylacetic acid, homovanillic acid, and 3-(3-hydroxyphenyl)-3-hydroxypropionic acid. However, there was no difference between the excreted amounts of these metabolites after consumption of WGM or WGM_Soy, indicating that the soy drink is a suitable carrier for WGM polyphenols. Interestingly, WGM_Soy induced a significant increase in excretion of cis-aconitate compared with WGM and PLA, suggesting a higher demand on the tricarboxylic acid cycle. In conclusion, SPE-NMR metabolite sub-profiling is a reliable and improved method for quantification and identification of metabolites in urine to discover dietary effects and markers of phytochemical exposure. PMID:22932811

Jacobs, Doris M; Spiesser, Laura; Garnier, Maxime; de Roo, Niels; van Dorsten, Ferdi; Hollebrands, Boudewijn; van Velzen, Ewoud; Draijer, Richard; van Duynhoven, John

2012-08-31

459

The acidity of niobic acid studied by 1H broad-line NMR at 4 K and H MAS NMR at room temperature: comparison with other solid acids  

Microsoft Academic Search

The acidity of niobium pentoxide calcined at 573 K has been studied by interacting water molecules and the solid acid using 1H broad-line NMR at 4 K and MAS NMR at room temperature. 1H Broad-line NMR in ‘rigid lattice’ conditions allows the determination of the numbers of the oxygen-protonated species (H3O+ and H2O ··· HO species, unreacted OH groups or

Patrice Batamack; Robert Vincent; Jacques Fraissard

1996-01-01

460

LC-NMR identification of a novel taurine-related metabolite observed in 1H NMR-based metabonomics of genetically hypertensive rats  

Microsoft Academic Search

This paper describes the LC-NMR spectroscopic identification of a novel urinary endogenous metabolite responsible for the signals, which were found as major contributors to the separation between genetically hypertensive rats (SHRSP) and normotensive control rats (WKY) in previous NMR-based metabonomic studies. Urine samples from 26-week-old normotensive rats were analyzed by an LC-NMR system equipped with a reversed-phase column having high

Kazuki Akira; Hidemichi Mitome; Misako Imachi; Yasuo Shida; Hiroaki Miyaoka; Takao Hashimoto

2010-01-01

461

Reducing the NMR sample volume using a single organic liquid: increased sensitivity for mass-limited samples with standard NMR probes.  

PubMed

A simple inexpensive protocol for confining an aqueous sample to the active region of a standard NMR probe is examined for high-resolution NMR. The aqueous sample is sandwiched between an inert perfluorinated organic liquid that has been exploited in the design of micro-coil NMR probes. The procedure is demonstrated with 3mm NMR tubes at ambient and elevated temperatures but should be equally applicable to smaller diameter tubes. It is shown that confinement has minimal effects on line shape and provides at least a two fold increase in sensitivity over a conventional sample, for the same mass of solute. PMID:19303797

Jarrell, H C

2009-02-25

462

PR-CALC: A Program for the Reconstruction of NMR Spectra from Projections  

Microsoft Academic Search

Projection-reconstruction NMR (PR-NMR) has attracted growing attention as a method for collecting multidimensional NMR data\\u000a rapidly. The PR-NMR procedure involves measuring lower-dimensional projections of a higher-dimensional spectrum, which are\\u000a then used for the mathematical reconstruction of the full spectrum. We describe here the program PR-CALC, for the reconstruction\\u000a of NMR spectra from projection data. This program