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1

Picoliter H-1 NMR Spectroscopy  

SciTech Connect

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

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

2002-02-01

2

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

3

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

4

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

5

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

6

"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

7

Ultrahigh-resolution NMR spectroscopy.  

PubMed

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

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

2014-07-01

8

H 1 NMR analysis of nuclear relaxation mechanisms in Pd–H and Pd–Ag–H alloys  

Microsoft Academic Search

Crystalline Pd1?xAgx–Hy (x=0–0.35) alloys were studied as model systems representing a chemically disordered system for hydrogen-storage materials. Extensive H1 relaxation rate (R1, R1? and R2) measurements were carried out in a wide temperature range of 2.4–400?K. Palladium–silver alloys of silver concentration as high as 35?at.% were studied by NMR spectroscopy for the first time. The relaxation mechanisms magnetic dipolar relaxation

M. Bokor; P. Bánki; G. Lasanda; K. Tompa

2005-01-01

9

Evaluation of shift agents for potential application to Na and H-1 NMR imaging  

SciTech Connect

The development and use of paramagnetic NMR contrast agents for NMR imaging application has been actively pursued in recent years. The two major types of agents investigated have been the metal ion chelates (e.g. Gd-DTPA) and the organic free radicals such as the nitroxides. Both of these types of agents fall in the class of contrast agents which effect the T/sub 1/ of nuclei such as H-1. The relaxation contrast agents can cause 50-100% enhancement of the H-1 signal in NMR imaging. A potential advantage of shift agents versus relaxation agents in NMR imaging applications is the very high contrast achievable using shift agents. In this work the spectroscopic evaluation of EDTA, DTPA and TTHA chelates of Thulium (Tm) and Dysprosium (Dy) was undertaken to determine their potential as sodium and proton NMR shift agents. The Dy chelates were found to induce downfield shifts in the Na-23 and H-1 NMR signals while the Tm analogs caused either downfield or upfield shifts depending upon the ligand used. In all cases the Dy complexes induced greater shifts than Tm as expected form the larger magnetic moment of Dy/sup +3/ versus Tm/sup +3/. The magnitude of shift for Na-23 was generally greater than for H-1 an the degree of Na-23 shift showed a pH dependency in the pH range of 2-7 of the metal complex solution. These effects are consistent with an enhanced NMR shift caused by electrostatic interactions of the positively charged Na-23 and negatively charged lanthanide complexes. The application of shift agents to contrast enhancement in H-1 NMR imaging of a phantom is demonstrated.

Carpenter, A.P. Jr.; Wolshin, E.M.; Srinivasan, P.R.; Fossel, E.T.

1985-05-01

10

Hyperpolarized (131)Xe NMR spectroscopy.  

PubMed

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

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

2011-01-01

11

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

12

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

13

H-1 NMR study of ternary ammonia-alkali metal-graphite intercalation compounds  

NASA Technical Reports Server (NTRS)

For the first-stage ternary ammonia-alkali metal-graphite intercalation compounds M(NH3)(x)C24(x of about 4, M = K, Rb, Cs), three sets of triplet H-1 NMR spectral lines have been observed at various temperatures and orientations due to the H-1 - H-1 and N-14 - H-1 dipolar interactions. The structures of these compounds have been inferred as mobile (liquid-like) intercalant layers of planar M(NH3)4 ions in between the carbon layers. For the intercalated ammonia molecules, the potential barrier is about 0.2 eV and the molecular geometry is very close to the free NH3 in gas phase.

Tsang, T.; Fronko, R. M.; Resing, H. A.; Qian, X. W.; Solin, S. A.

1987-01-01

14

NMR spectroscopy of peptides and proteins  

Microsoft Academic Search

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

Mark G. Hinds; Raymond S. Norton

1997-01-01

15

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...

16

Contactless NMR spectroscopy on a chip.  

PubMed

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

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

2012-04-17

17

Effects and mechanisms of acetyl-L-cysteine in rats with chronic mountain sickness with H1-NMR metabolomics methods  

PubMed Central

Background We established a rat model of chronic mountain sickness using acetyl-L-cysteine. Then we studied the effects and mechanisms of acetyl-L-cysteine (Da) in rats with chronic mountain sickness using nuclear magnetic resonance (H1-NMR) metabolomics methods. Material/Methods Using NMR spectroscopy combined with pattern recognition and orthogonal partial least squares discriminant analysis, we analyzed the impact of Da on blood metabolism in rats with chronic mountain sickness by determining different metabolites and changes in metabolic network in the blood of rats with mountain sickness after the intragastric administration of different doses of Da suspension. Results Increased levels of amino acids (valine, tyrosine, 1-methyl-histidine, leucine, phenylalanine, and methionine) were detected in the blood of rats in the chronic mountain sickness group, yet significantly decreased levels were detected in control rats. At the same time, ?-glucose and ?-glucose levels were markedly elevated in the blood of rats in the model group but decreased in the chronic mountain sickness group, which indicated a statistically significant difference compared with the chronic altitude sickness model group (P<0.05). Conclusions Da has a significant impact on the metabolism of rats with chronic mountain sickness. Da may act on the disturbed glucose metabolism and amino acid metabolism in rats triggered by chronic mountain sickness, resulting in the treatment and prevention of this disease.

Maimaitiyiming, Dilinuer; Aikemu, Ainiwaer; Kamilijiang, Mayila; Salamu, Adila; Zhang, Xiangyang

2014-01-01

18

Drug solubilization mechanism of ?-glucosyl stevia by NMR spectroscopy.  

PubMed

We investigated the drug solubilization mechanism of ?-glucosyl stevia (Stevia-G) which was synthesized from stevia (rebaudioside-A) by transglycosylation. (1)H and (13)C NMR peaks of Stevia-G in water were assigned by two-dimensional (2D) NMR experiments including (1)H-(1)H correlation, (1)H-(13)C heteronuclear multiple bond correlation, and (1)H-(13)C heteronuclear multiple quantum coherence spectroscopies. The (1)H and (13)C peaks clearly showed the incorporation of two glucose units into rebaudioside-A to produce Stevia-G, supported by steviol glycoside and glucosyl residue assays. The concentration-dependent chemical shifts of Stevia-G protons correlated well with a mass-action law model, indicating the self-association of Stevia-G molecules in water. The critical micelle concentration (CMC) was 12.0 mg/mL at 37°C. The aggregation number was 2 below the CMC and 12 above the CMC. Dynamic light scattering and 2D (1)H-(1)H nuclear Overhauser effect spectroscopy (NOESY) NMR experiments demonstrated that Stevia-G self-associated into micelles of a few nanometers in size with a core-shell structure, containing a kaurane diterpenoid-based hydrophobic core and a glucose-based shell. 2D (1)H-(1)H NOESY NMR measurements also revealed that a poorly water-soluble drug, naringenin, was incorporated into the hydrophobic core of the Stevia-G micelle. The Stevia-G self-assembly behavior and micellar drug inclusion capacity can achieve significant enhancement in drug solubility. PMID:24508331

Zhang, Junying; Higashi, Kenjirou; Ueda, Keisuke; Kadota, Kazunori; Tozuka, Yuichi; Limwikrant, Waree; Yamamoto, Keiji; Moribe, Kunikazu

2014-04-25

19

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

20

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

21

Dynamic nuclear polarization surface enhanced NMR spectroscopy.  

PubMed

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

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

2013-09-17

22

Ensemble quantum computing by NMR spectroscopy  

PubMed Central

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

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

1997-01-01

23

Direct chiral discrimination in NMR spectroscopy  

NASA Astrophysics Data System (ADS)

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

Buckingham, A. D.; Fischer, P.

2006-05-01

24

Quantitative NMR spectroscopy--applications in drug analysis.  

PubMed

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

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

2005-08-10

25

4'-C-[(4-Trifluoromethyl-1H-1,2,3-triazol-1-yl)methyl]thymidine as a Sensitive (19)F NMR Sensor for the Detection of Oligonucleotide Secondary Structures.  

PubMed

4'-C-[(4-Trifluoromethyl-1H-1,2,3-triazol-1-yl)methyl]thymidine was synthesized and incorporated as a phosphoramidite into oligonucleotide sequences. Its applicability as a sensor for the (19)F NMR spectroscopic detection of DNA and RNA secondary structures was demonstrated. On DNA, the (19)F NMR measurements were focused on monitoring of duplex-triplex conversion, for which this fluorine-labeled 2'-deoxynucleoside proved to be a powerful sensor. This sensor seemingly favors DNA, but its behavior in the RNA environment also turned out to be informative. As a demonstration, invasion of a 2'-O-methyl oligoribonucleotide into an RNA hairpin model (HIV-1 TAR) was monitored by (19)F NMR spectroscopy. According to the thermal denaturation studies by UV spectroscopy, the effect of the 4'-C-(4-trifluoromethyl-1H-1,2,3-triazol-1-yl)methyl moiety on the stability of these DNA and RNA models was marginal. PMID:24678774

Granqvist, Lotta; Virta, Pasi

2014-04-18

26

NMR spectroscopy on domain dynamics in biomacromolecules.  

PubMed

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

Shapiro, Yury E

2013-08-01

27

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

28

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.

29

Broadband Multiple-Quantum NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

30

PENDANT 13C NMR Spectroscopy Applied to CHn Groups  

NASA Astrophysics Data System (ADS)

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

Gençten, Azmi; Šaka, Irfan; Gümüš, Sedat

2006-05-01

31

Principles and Demonstrations of Quantum Information Processing by NMR Spectroscopy  

Microsoft Academic Search

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

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

2000-01-01

32

NMR Spectroscopy of Experimentally Shocked Silicate Minerals  

Microsoft Academic Search

Magic-angle spinning nuclear magnetic resonance (MAS NMR) techniques were used to analyze experimentally shocked quartz and feldspar powders. ²⁚Si NMR spectra were determined for quartz and labradorite feldspar and ²⁡Al and ²³Na spectra for labradorite. Both minerals were shocked to 7.5, 16.4, and 22 GPA using the Sandia Momma Bear'' recovery fixtures. The MAS NMR results for quartz are in

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

1991-01-01

33

Mapping functional interaction sites of human prune C-terminal domain by NMR spectroscopy in human cell lysates.  

PubMed

Get well prune: The C-terminal third domain of h-prune is largely unfolded and involved in relevant protein-protein interactions, particularly with Nm23-H1 (see figure), GSK-3? and gelsolin. This study shows that protein functions mediated by protein-protein interactions can be accurately followed in cell lysates by using fast NMR spectroscopy, which could be easily used for a very efficient NMR drug-discovery strategy. PMID:23939913

Diana, Donatella; Smaldone, Giovanni; De Antonellis, Pasquale; Pirone, Luciano; Carotenuto, MariaNeve; Alonzi, Alessandro; Di Gaetano, Sonia; Zollo, Massimo; Pedone, Emilia M; Fattorusso, Roberto

2013-09-01

34

Fragment-Based Drug Discovery Using NMR Spectroscopy  

PubMed Central

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

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

2013-01-01

35

Fragment-based drug discovery using NMR spectroscopy.  

PubMed

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

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

2013-06-01

36

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

37

NMR spectroscopy of experimentally shocked silicate minerals.  

National Technical Information Service (NTIS)

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

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

1991-01-01

38

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

39

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

40

Solid-State NMR Spectroscopy for the Physical Chemistry Laboratory  

ERIC Educational Resources Information Center

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

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

2013-01-01

41

Magnesium silicate dissolution investigated by S1-29 MAS, H-1 Si-29 CPMAS, Mg-25 QCPMG, and H-1 Mg-25 CP QCPMG NMR  

SciTech Connect

Olivine-(Mg,Fe){sub 2}SiO{sub 4}-has been the subject of frequent investigation in the earth sciences because of its simple structure and rapid dissolution kinetics. Several studies have observed a preferential release of the divalent cation with respect to silicon during weathering under acidic conditions, which has been correlated to the formation of a silicon-rich leached layer. While leached layer formation has been inferred through the changing solution chemistry, a thorough spectroscopic investigation of olivine reacted under acidic conditions has not been conducted. The pure magnesium end member of the olivine series (forsterite-Mg2SiO4) was chosen for detailed investigations in this study because paramagnetic iron hinders NMR investigations by providing an extra mode of relaxation for neighboring nuclei, causing lineshapes to become significantly broadened and unobservable in the NMR spectrum. For reacting forsterite, spectroscopic interrogations using nuclear magnetic resonance (NMR) can elucidate the changing magnesium coordination and bonding environment. In this study, we combine analysis of the changing solution chemistry with advanced NMR techniques ({sup 29}Si MAS, {sup 1}H-{sup 29}Si CP MAS, {sup 25}Mg QCPMG, and {sup 1}H-{sup 25}Mg CP QCPMG NMR) to probe leached layer formation and secondary phase precipitation during the dissolution of forsterite at 150 C.

Davis, M C [Oak Ridge National Laboratory (ORNL); Brouwer, Piet W [ORNL; Wesolowski, David J [ORNL; Anovitz, Lawrence {Larry} M [ORNL

2009-07-01

42

Study of stretched polypropylene fibres by 1H pulsed and CW NMR spectroscopy.  

PubMed

A set of stretched isotactic polypropylene fibres prepared with the draw ratio lambda=4 at four different stretching temperatures was investigated by H1 pulsed relaxation NMR methods and CW NMR spectroscopy. We have studied the influence of the stretching temperature and draw ratio upon the changes of structure and molecular mobility. Some information on the influence of these conditions was obtained from CW NMR measurements by means of the temperature dependences of second moment M(2) and decomposition of NMR spectra into elementary components corresponding to the chains with different mobility. H1 CW NMR spectra were measured at two (14.1 and 10.5 MHz) Larmor frequencies in the temperature range 200-420 K. An analysis of the experimental data shows that the stretching of the fibres at different temperature results in a change of molecular mobility. Spin-lattice relaxation times in laboratory (T(1)) and rotating (T(1rho)) frames were also measured on the set of the fibres in the temperature range 239-423 K at 30 MHz Larmor frequency employing a home made pulse spectrometer. In the rotating frame spin-lattice relaxation time measurements in the temperature range above 278 K three relaxation times T(1rho) have been observed. The minima of the temperature dependences of the observed relaxation times reflect an alpha-relaxation process in crystalline regions and beta-relaxation process related to a double glass transition in the non-crystalline regions of the studied fibres. PMID:19857943

Sevcovic, L; Mucha, L'

2009-11-01

43

NMR Spectroscopy: Processing Strategies (by Peter Bigler)  

NASA Astrophysics Data System (ADS)

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

Mills, Nancy S.

1998-06-01

44

Membrane Protein Structure and Dynamics from NMR Spectroscopy  

PubMed Central

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

Hong, Mei; Zhang, Yuan; Hu, Fanghao

2014-01-01

45

Exposing the Moving Parts of Proteins with NMR Spectroscopy  

PubMed Central

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

Peng, J.W.

2012-01-01

46

NMR spectroscopy of experimentally shocked silicate minerals  

SciTech Connect

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

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

1991-01-01

47

Two-dimensional NMR spectroscopy. Applications for chemists and biochemists  

SciTech Connect

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

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

1987-01-01

48

NMR Spectroscopy and Pediatric Brain Tumors  

Microsoft Academic Search

Proton nuclear magnetic resonance spectroscopy ( 1 H-NMRS) is a noninvasive in vivo technique that utilizes conventional MR imaging hardware to obtain biochemical information from a discrete volume of tissue after suppres- sion of the water signal. MR spectroscopy coupled with conventional MR imaging allows correlation of structural changes with biochemical processes in tissues by measur- ing specific metabolites present

KATHERINE E. WARREN

2004-01-01

49

High-resolution NMR spectroscopy under the fume hood.  

PubMed

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

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

2011-08-01

50

NMR spectroscopy for determination of cationic polymer concentrations  

Microsoft Academic Search

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

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

2002-01-01

51

Studies of the Photodegradation of Spruce Lignin by Nmr Spectroscopy  

Microsoft Academic Search

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

Rainer Sjöholm; Bjarne Holmbom; Nina Akerback

1992-01-01

52

MULTIVARIATE CURVE RESOLUTION OF NMR SPECTROSCOPY METABONOMIC DATA  

EPA Science Inventory

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

53

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

54

Double Quantum Filtered NMR Spectroscopy and Imaging  

NASA Astrophysics Data System (ADS)

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

Navon, Gil

2007-03-01

55

NMR spectroscopic and computational study of conformational isomerism in substituted 2-aryl-3H-1-benzazepines: toward isolable atropisomeric benzazepine enantiomers.  

PubMed

Certain 2-aryl-3H-1-benzazepines are conformationally mobile on the NMR time scale. Variable-temperature NMR experiments bolstered by calculations indicate that alkylation of the azepine ring will slow the interconversion of conformational enantiomers markedly. DFT studies show that, while the substitution patterns of the aryl groups at C2 and C4 do not exert large effects on the rate of enantiomerization, alkylation at C5 slows it appreciably. Alkylation at C3 slows enantiomerization even more, possibly to the extent that isolation of atropisomers might be attempted. PMID:23848431

Ramig, Keith; Greer, Edyta M; Szalda, David J; Karimi, Sasan; Ko, Allen; Boulos, Laura; Gu, Jiansan; Dvorkin, Nathan; Bhramdat, Hema; Subramaniam, Gopal

2013-08-16

56

Mobile sensor for high resolution NMR spectroscopy and imaging  

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

57

Recombinant locust apolipophorin III: characterization and NMR spectroscopy  

Microsoft Academic Search

Apolipophorin III (apoLp-III) from the locust Locusta migratoria is an exchangeable apolipoprotein that reversibly binds to lipoproteins. During lipid binding the protein has been proposed to undergo a major conformational change. To study the mechanism of lipid binding we have cloned and expressed recombinant protein in bacteria, permitting stable isotope enrichment for heteronuclear NMR spectroscopy and site-directed mutagenesis. The cDNA

Paul M. M. Weers; Jianjun Wang; Dick J. Van der Horst; Cyril M. Kay; Brian D. Sykes; Robert O. Ryan

1998-01-01

58

NMR spectroscopy around filling factor three  

NASA Astrophysics Data System (ADS)

We probe the spin signatures of a two-dimensional electron system, confined to a GaAs quantum well, around filling factor three (?˜3) using resistively detected nuclear magnetic resonance (RDNMR) spectroscopy at milliKelvin temperatures. Whereas the existence of spin textures, known as skyrmions, around filling factor one is well established, an understanding of the spin degrees of freedom for odd-integer states in higher Landau levels remains elusive. It is believed that for skyrmions to exist at ?˜3, the Zeeman energy needs to be smaller than in the case of ?˜1 [1]. We measured the spin-lattice relaxation time, T1, which is sensitive to these spin textures as they trigger a rapid nuclear spin relaxation. Our T1 measurements around ?= 3 at 5 T find a small spin-lattice relaxation rate, suggesting the absence of skyrmions. In addition, our Knight shift measurements corroborate this interpretation. Furthermore, we report striking anomalies in the RDNMR spectral line shape and discuss their origin in conjunction with our findings. * [1]N. R. Cooper, Phys. Rev. B 55, R1934 (1997).

Rhone, Trevor David; Tiemann, Lars; Muraki, Koji

2013-03-01

59

Automated amino acid side-chain NMR assignment of proteins using 13 C- and 15 N-resolved 3D [ 1 H, 1 H]-NOESY  

Microsoft Academic Search

ASCAN is a new algorithm for automatic sequence-specific NMR assignment of amino acid side-chains in proteins, which uses\\u000a as input the primary structure of the protein, chemical shift lists of 1HN, 15N, 13C?, 13C? and possibly 1H? from the previous polypeptide backbone assignment, and one or several 3D 13C- or 15N-resolved [1H,1H]-NOESY spectra. ASCAN has also been laid out for

Francesco Fiorito; Torsten Herrmann; Fred F. Damberger; Kurt Wüthrich

2008-01-01

60

Chirality in gold nanoclusters probed by NMR spectroscopy.  

PubMed

We report the analysis of chirality in atomically precise gold nanoclusters by nuclear magnetic resonance (NMR) spectroscopic probing of the surface ligands. The Au(38)(SR)(24) and Au(25)(SR)(18) (where, R = CH(2)CH(2)Ph) are used as representative models for chiral and nonchiral nanoclusters, respectively. Interestingly, different (1)H signals for the two germinal protons in each CH(2) of the ligands on the chiral Au(38)(SR)(24) nanocluster were observed, so-called diastereotopicity. For ?-CH(2) (closest to the chiral metal core), a chemical shift difference of up to ~0.8 ppm was observed. As for the nonchiral Au(25)(SCH(2)CH(2)Ph)(18)(-)TOA(+) nanocluster, no diastereotopicity was detected (i.e., no chemical shift difference for the two protons in the CH(2)), confirming the Au(25) core being nonchiral. These two typical examples demonstrate that NMR spectroscopy can be a useful tool for investigating chirality in Au nanoclusters. Since the diastereotopicity induced on the methylene protons by chiral nanoclusters is independent of the enantiomeric composition of the chiral particles, NMR can probe the chirality of the nanoclusters even in the case of a racemic mixture, while circular dichroism spectroscopy is not useful for racemic mixtures. PMID:21981416

Qian, Huifeng; Zhu, Manzhou; Gayathri, Chakicherla; Gil, Roberto R; Jin, Rongchao

2011-11-22

61

Simulation of selective pulse techniques for localized NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The results of a computer simulation investigation delineating the limits of resolution, sensitivity, and accuracy of the depth- resolved suface-coil spectroscopy (DRESS), volume-selective excitation (VSE), and image-selected in vivo spectroscopy (ISIS) methods for achieving spatially localized NMR spectroscopy are presented. A computer program, which numerically solves the Bloch equations for variable input parameters, is used to simulate the spatial localization afforded by each technique. Because the numerical solution of the Bloch equations describes the behavior of the bulk magnetization with great precision, the simulations provide an objective and realistic means of evaluating the performance of the individual localization schemes and reveal nuances and limitations not discussed in the original experimental papers. The results of this computer simulation study should encourage the optimization of localization methodology for use in specific applications.

Garwood, Michael; Schleich, Thomas; Robin Bendall, M.

62

Magnesium silicate dissolution investigated by Si-29 MAS, H-1-Si-29 CPMAS, Mg-25 QCPMG NMR.  

SciTech Connect

Olivine-(Mg,Fe){sub 2}SiO{sub 4}-has been the subject of frequent investigation in the earth sciences because of its simple structure and rapid dissolution kinetics. Several studies have observed a preferential release of the divalent cation with respect to silicon during weathering under acidic conditions, which has been correlated to the formation of a silicon-rich leached layer. While leached layer formation has been inferred through the changing solution chemistry, a thorough spectroscopic investigation of olivine reacted under acidic conditions has not been conducted. The pure magnesium end member of the olivine series (forsterite-Mg{sub 2}SiO{sub 4}) was chosen for detailed investigations in this study because paramagnetic iron hinders NMR investigations by providing an extra mode of relaxation for neighboring nuclei, causing lineshapes to become significantly broadened and unobservable in the NMR spectrum. For reacting forsterite, spectroscopic interrogations using nuclear magnetic resonance (NMR) can elucidate the changing magnesium coordination and bonding environment. In this study, we combine analysis of the changing solution chemistry with advanced NMR techniques ({sup 29}Si MAS, {sup 1}H-{sup 29}Si CP MAS, {sup 25}Mg QCPMG, and {sup 1}H-{sup 25}Mg CP QCPMG NMR) to probe leached layer formation and secondary phase precipitation during the dissolution of forsterite at 150 C.

Davis, M C [Oak Ridge National Laboratory (ORNL); Wesolowski, David J [ORNL

2009-09-01

63

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 Ĺ 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 Ĺ away from the paramagnetic center. In this Account, we discuss MAS NMR structural studies of nitroxide and EDTA-Cu(2+) labeled variants of a model 56 amino acid globular protein, B1 immunoglobulin-binding domain of protein G (GB1), in the microcrystalline solid phase. We used a set of six EDTA-Cu(2+)-tagged GB1 mutants to rapidly determine the global protein fold in a de novo fashion. Remarkably, these studies required quantitative measurements of only approximately four or five backbone amide (15)N longitudinal paramagnetic relaxation enhancements per residue, in the complete absence of the usual internuclear distance restraints. Importantly, this paramagnetic solid-state NMR methodology is general and can be directly applied to larger proteins and protein complexes for which a significant fraction of the signals can be assigned in standard 2D and 3D MAS NMR chemical shift correlation spectra. PMID:23464364

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

2013-09-17

64

Quantitative analysis of hydrogen peroxide by 1H NMR spectroscopy.  

PubMed

A technique utilizing 1H NMR spectroscopy has been developed to measure the concentration of hydrogen peroxide from 10(-3) to 10 M. Hydrogen peroxide produces a peak at around 10-11 ppm, depending upon the interaction between solvent molecules and hydrogen peroxide molecules. The intensity of this peak can be monitored once every 30 s, enabling the measurement of changes in hydrogen peroxide concentration as a function of time. 1H NMR has several advantages over other techniques: (1) applicability to a broad range of solvents, (2) ability to quantify hydrogen peroxide rapidly, and (3) ability to follow reactions forming and/or consuming hydrogen peroxide as a function of time. As an example, this analytical technique has been used to measure the concentration of hydrogen peroxide as a function of time in a study of hydrogen peroxide decomposition catalyzed by iron(III) tetrakispentafluorophenyl porphyrin. PMID:15756600

Stephenson, Ned A; Bell, Alexis T

2005-03-01

65

Preparation, GIAO NMR Calculations and Acidic Properties of Some Novel 4,5-dihydro-1H-1,2,4-triazol-5-one Derivatives with Their Antioxidant Activities  

PubMed Central

Six novel 3-alkyl(aryl)-4-(p-nitrobenzoylamino)-4,5-dihydro-1H-1,2,4-triazol-5- ones (2a-f) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H- 1,2,4-triazol-5-ones (1a-f) with p-nitrobenzoyl chloride and characterized by elemental analyses and IR, 1H-NMR, 13C-NMR and UV spectral data. The newly synthesized compounds 2 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as acetone, isopropyl alcohol, tert-butyl alcohol and N,N-dimethylformamide, and the half-neutralization potential values and the corresponding pKa values were determined for all cases. Thus, the effects of solvents and molecular structure upon acidity were investigated. In addition, isotropic 1H and 13C nuclear magnetic shielding constants of compounds 2 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound has been optimized using the 6-311G basis set. Theoretical values were compared to the experimental data. Furthermore, these new compounds and five recently reported 3-alkyl-4-(2-furoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3a–c,e,f) were screened for their antioxidant activities.

Yuksek, Haydar; Alkan, Muzaffer; Cakmak, Ismail; Ocak, Zafer; Bahceci, Sule; Calapoglu, Mustafa; Elmastas, Mahfuz; Kolomuc, Ali; Aksu, Havva

2008-01-01

66

Identification of metabolites in human hepatic bile using 800 MHz 1H NMR spectroscopy, HPLC-NMR/MS and UPLC-MS.  

PubMed

The first application of high field NMR spectroscopy (800 MHz for (1)H observation) to human hepatic bile (as opposed to gall bladder bile) is reported. The bile sample used for detailed investigation was from a donor liver with mild fat infiltration, collected during organ retrieval prior to transplantation. In addition, to focus on the detection of bile acids in particular, a bile extract was analysed by 800 MHz (1)H NMR spectroscopy, HPLC-NMR/MS and UPLC-MS. In the whole bile sample, 40 compounds have been assigned with the aid of two-dimensional (1)H-(1)H TOCSY and (1)H-(13)C HSQC spectra. These include phosphatidylcholine, 14 amino acids, 10 organic acids, 4 carbohydrates and polyols (glucose, glucuronate, glycerol and myo-inositol), choline, phosphocholine, betaine, trimethylamine-N-oxide and other small molecules. An initial NMR-based assessment of the concentration range of some key metabolites has been made. Some observed chemical shifts differ from expected database values, probably due to a difference in bulk diamagnetic susceptibility. The NMR spectra of the whole extract gave identification of the major bile acids (cholic, deoxycholic and chenodeoxycholic), but the glycine and taurine conjugates of a given bile acid could not be distinguished. However, this was achieved by HPLC-NMR/MS, which enabled the separation and identification of ten conjugated bile acids with relative abundances varying from approximately 0.1% (taurolithocholic acid) to 34.0% (glycocholic acid), of which, only the five most abundant acids could be detected by NMR, including the isomers glycodeoxycholic acid and glycochenodeoxycholic acid, which are difficult to distinguish by conventional LC-MS analysis. In a separate experiment, the use of UPLC-MS allowed the detection and identification of 13 bile acids. This work has shown the complementary potential of NMR spectroscopy, MS and hyphenated NMR/MS for elucidating the complex metabolic profile of human hepatic bile. This will be useful baseline information in ongoing studies of liver excretory function and organ transplantation. PMID:19156264

Duarte, Iola F; Legido-Quigley, Cristina; Parker, David A; Swann, Jonathan R; Spraul, Manfred; Braumann, Ulrich; Gil, Ana M; Holmes, Elaine; Nicholson, Jeremy K; Murphy, Gerard M; Vilca-Melendez, Hector; Heaton, Nigel; Lindon, John C

2009-02-01

67

Complex mixture analysis of organic compounds in green coffee bean extract by two-dimensional NMR spectroscopy.  

PubMed

A complex mixture analysis by one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy was carried out for the first time for the identification and quantification of organic compounds in green coffee bean extract (GCBE). A combination of (1)H-(1)H DQF-COSY, (1)H-(13)C HSQC, and (1)H-(13)C CT-HMBC two-dimensional sequences was used, and 16 compounds were identified. In particular, three isomers of caffeoylquinic acid were identified in the complex mixture without any separation. In addition, GCBE components were quantified by the integration of carbon signals by use of a relaxation reagent and an inverse-gated decoupling method without a nuclear Overhauser effect. This NMR methodology provides detailed information about the kinds and amounts of GCBE components, and in our study, the chemical makeup of GCBE was clarified by the NMR results. PMID:20818806

Wei, Feifei; Furihata, Kazuo; Hu, Fangyu; Miyakawa, Takuya; Tanokura, Masaru

2010-11-01

68

Stimulated Anti-Echo Selection in Spatially Localized NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

Spectral localization using the stimulated-echo acquisition mode (STEAM) is one of the most popular methods in volume-localized in vivoNMR spectroscopy. The localized volume signal is generated via stimulated echoes from spins excited by three 90° RF pulses, and the conventional STEAM sequence detects the stimulated-echo signal. From an analysis of the STEAM pulse sequence using the coherence transfer pathway formalism, stimulated anti-echoes are also formed by the same pulse sequence, which constitute the other half of the localized signal in the STEAM experiment. A new scheme of pulsed field gradients for the selection of stimulated anti-echoes was proposed, and localized spectroscopy in the stimulated anti-echo selection mode was achieved on a phantom and from in vivorat brain.

Zhu, Jian-Ming; Smith, Ian C. P.

1999-01-01

69

Report on neptunium speciation by NMR and optical spectroscopies  

SciTech Connect

Hydrolysis and carbonate complexation reactions were examined for NpO{sub 2}{sup 2+} and NpO{sub 2}{sup +} ions by a variety of techniques including potentiometric titration, UV-Vis-NIR and NMR spectroscopy. The equilibrium constant for the reaction 3NpO{sub 2}(CO{sub 3}){sub 3}{sup 4{minus}} + 3H{sup +} {rightleftharpoons} (NpO{sub 2}){sub 3}(CO{sub 3}){sub 6}{sup 6{minus}} + 3HCO{sub 3}{sup {minus}} was determined to be logK = 19.7 ({plus_minus} 0.8) (I = 2.5 m). {sup 17}O NMR spectroscopy of NpO{sub 2}{sup n+} ions (n = 1,2) reveals a readily observable {sup 17}O resonance for n = 2, but not for n = 1. The first hydrolysis constant for NpO{sub 2}{sup +} was studied as a function of temperature, and the functional form for the temperature-dependent equilibrium constant for the reaction written as NpO{sub 2}{sup +} + H{sub 2}O {rightleftharpoons} NpO{sub 2}OH + H{sup +} was found to be logK = 2.28 {minus} 3780/T, where T is in {degree}K. Finally, the temperature dependence of neptunium(V) carbonate complexation constants was studied. For the first carbonate complexation constant, the appropriate functional form was found to be log{beta}{sub 01} = 1.47 + 786/T.

Tait, C.D.; Palmer, P.D.; Ekberg, S.A.; Clark, D.L.

1995-11-01

70

Galactose oxidase models: insights from 19F NMR spectroscopy.  

PubMed

(19)F labelled tripodal ligands that possess a N(3)O donor set (one phenol, one tertiary amine and either two pyridines or one pyridine and one quinoline) have been synthesized. The fluorine is incorporated either at the phenol O-donor (HL(F) and HL(CF3)) or at the quinoline N-donor (HLq(OMe) and HLq(NO2)). The copper(ii)-phenol complexes (2H)(2+), (1H)(2+), (3H)(2+) and (4H)(2+) as well as the corresponding copper(ii)-phenolate complexes have been characterized. X-Ray diffraction reveals an increase in the oxygen-copper bond distance of more than 0.4 A upon protonation of the phenolate moiety of (4)(+). Protonation is accompanied by an axial to equatorial isomerization of the quinoline group. DFT calculations show that stretching of the Cu-O(phenol) bond, pi-stacking interactions and rotation of the pyridine are key steps in this isomerization process. Protonation, and thus changes in the oxygen-copper bond distance induce either a decrease ((1H)(2+), (2H)(2+)) or an increase ((3H)(2+) and (4H)(2+)) in the copper-fluorine distance that could be monitored by (19)F NMR. In the former case, a broadening of the (19)F NMR signal is observed, whereas a sharpening is observed in the latter case. Temperature dependent (19)F NMR measurements on equimolar mixtures of the phenol and phenolate complexes of (3)(+) and (4)(+) reveal rate constants for proton transfer and/or isomerization of 3000 +/- 100 s(-1) and 2900 +/- 100 s(-1), respectively, at the coalescence temperature. This temperature was found to be strongly affected by the phenol para-substituent as it is 226 K and ca. 330 K for (3)(+) and (4)(+), respectively. A phenoxyl radical species ((3 )(2+)) could be generated and characterized for the first time by (19)F NMR spectroscopy. PMID:19156277

Michel, Fabien; Hamman, Sylvain; Philouze, Christian; Del Valle, Carlos Perez; Saint-Aman, Eric; Thomas, Fabrice

2009-02-01

71

Structure of a Conserved Retroviral RNA Packaging Element by NMR Spectroscopy and Cryo-Electron Tomography  

PubMed Central

The 5?-untranslated regions (5?-UTRs) of all gammaretroviruses contain a conserved “double hairpin motif” (?CD) that is required for genome packaging. Both hairpins (SL-C and SL-D) contain GACG tetraloops that, in isolated RNAs, are capable of forming “kissing” interactions stabilized by two intermolecular G-C base pairs. We have determined the three-dimensional structure of the double hairpin from the Moloney Murine Leukemia Virus (MoMuLV) ([?CD]2, 132-nucleotides, 42.8 kDaltons) using a 2H-edited NMR spectroscopy-based approach. This approach enabled the detection of 1H-1H dipolar interactions that were not observed in previous studies of isolated SL-C and SL-D hairpin RNAs using traditional 1H-1H correlated and 1H-13C-edited NMR methods. The hairpins participate in intermolecular cross-kissing interactions (SL-C to SL-D’ and SLC’ to SL-D), and stack in an end-to-end manner (SL-C to SL-D and SL-C’ to SL-D’) that gives rise to an elongated overall shape (ca. 95 Ĺ by 45 Ĺ by 25 Ĺ). The global structure was confirmed by cryo-electron tomography (cryo-ET), making [?CD]2 simultaneously the smallest RNA to be structurally characterized to date by cryo-ET and among the largest to be determined by NMR. Our findings suggest that, in addition to promoting dimerization, [?CD]2 functions as a scaffold that helps initiate virus assembly by exposing a cluster of conserved UCUG elements for binding to the cognate nucleocapsid domains of assembling viral Gag proteins.

Miyazaki, Yasuyuki; Irobalieva, Rossitza N.; Tolbert, Blanton; Smalls-Mantey, Adjoa; Iyalla, Kilali; Loeliger, Kelsey; D'Souza, Victoria; Khant, Htet; Schmid, Michael F.; Garcia, Eric; Telesnitsky, Alice; Chiu, Wah; Summers, Michael F.

2010-01-01

72

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

Microsoft Academic Search

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

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

2007-01-01

73

In vivo two-dimensional NMR correlation spectroscopy  

NASA Astrophysics Data System (ADS)

The poor resolution of in-vivo one- dimensional nuclear magnetic resonance spectroscopy (NMR) has limited its clinical potential. Currently, only the large singlet methyl resonances arising from N-acetyl aspartate (NAA), choline, and creatine are quantitated in a clinical setting. Other metabolites such as myo- inositol, glutamine, glutamate, lactate, and ?- amino butyric acid (GABA) are of clinical interest but quantitation is difficult due to the overlapping resonances and limited spectral resolution. To improve the spectral resolution and distinguish between overlapping resonances, a series of two- dimensional chemical shift correlation spectroscopy experiments were developed for a 1.5 Tesla clinical imaging magnet. Two-dimensional methods are attractive for in vivo spectroscopy due to their ability to unravel overlapping resonances with the second dimension, simplifying the interpretation and quantitation of low field NMR spectra. Two-dimensional experiments acquired with mix-mode line shape negate the advantages of the second dimension. For this reason, a new experiment, REVOLT, was developed to achieve absorptive mode line shape in both dimensions. Absorptive mode experiments were compared to mixed mode experiments with respect to sensitivity, resolution, and water suppression. Detailed theoretical and experimental calculations of the optimum spin lock and radio frequency power deposition were performed. Two-dimensional spectra were acquired from human bone marrow and human brain tissue. The human brain tissue spectra clearly reveal correlations among the coupled spins of NAA, glutamine, glutamate, lactate, GABA, aspartate and myo-inositol obtained from a single experiment of 23 minutes from a volume of 59 mL. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Kraft, Robert A.

1999-10-01

74

Ultraviolet Imaging Spectroscopy of Comet Lee (C/1999 H1) with HST/STIS  

NASA Astrophysics Data System (ADS)

Comet Lee (C/1999 H1) provided the first opportunity to observe a moderately active comet near 1 AU in the ultraviolet with the Space Telescope Imaging Spectrograph (STIS), installed on the Hubble Space Telescope (HST) in February 1997. Observations were made pre-perihelion on 1999 June 7 at heliocentric and geocentric distances of 0.97 AU and 1.21 AU, respectively, shortly before the comet entered the HST solar avoidance zone. Long-slit spectra were obtained over the range 1150--3200 Angstroms with a spatial resolution along the slit of 0.''05, which translates to 44 km projected at the comet. The strongest emissions are due to OH, CS and continuum, but the low dust/gas ratio implied by the relative brightness of OH to continuum enables the detection of S_2 and C_2. This is only the third comet (the other two being IRAS-Araki-Alcock and Hyakutake) in which S_2 is positively identified. Atomic oxygen, carbon and sulfur are also detected (in addition to the strong hydrogen Lyman-alpha ) and sensitive upper limits are obtained for CO and CO_2. The spatial profiles of CS and the continuum are time-varying and symmetric about the nucleus, while those of the OH bands display significant asymmetry. A lifetime of CS_2, the presumed parent of CS, of roughly 1000 seconds is derived from modeling the CS spatial profile away from the nucleus. Production rates of the observed species are derived and will be compared with those obtained from ground-based optical, infrared and radio observations.

Feldman, P. D.; Weaver, H. A.; A'Hearn, M. F.; Festou, M. C.; McPhate, J. B.; Tozzi, G.-P.

1999-09-01

75

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

Microsoft Academic Search

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

David A. Snyder; Fengli Zhang; Rafael Brüschweiler

2007-01-01

76

'Shim pulses' for NMR spectroscopy in inhomogeneous magneticfields  

SciTech Connect

NMR spectroscopy conveys information about chemical structure through ppm-scale shifts of the resonance frequency depending on the chemical environment. In order to observe these small shifts, magnets with highly homogeneous magnetic field B{sub 0} are used. The high cost and large size of these magnets are a consequence of the requirement for high homogeneity. In this contribution we introduce a new method for recording high-resolution NMR spectra from samples in inhomogeneous B{sub 0}, opening up the possibility of exploiting magnets of lower homogeneity and cost. Instead of using the traditional B{sub 0} ''shim coils'', adiabatic radiofrequency (RF) pulse sequences and modulated B{sub 0} gradients generated by coils in the probe are used to produce ''shim pulses''. A great deal of work has been devoted to finding methods for retrieving chemical shift information even when B{sub 0} is inhomogeneous. One class of methods relies on zero- or multiple quantum coherences which evolve independently of B{sub 0}. These methods are inherently two-dimensional and the high-resolution information is obtained indirectly. In order to minimize experimental time it is desirable to acquire a high-resolution spectrum directly just as for traditional NMR in homogeneous fields. A further advantage with direct acquisition is that modification of already existing multidimensional NMR techniques is facilitated. A fundamentally different approach utilizes inhomogeneity of the RF magnetic field to periodically refocus the phase dispersion from the inhomogeneous B{sub 0}. With this technique a high-resolution spectrum can indeed be acquired in a single shot. The main drawback is the requirement for spatial matching between the RF and B{sub 0} inhomogeneities. Based on this latter technique we propose the use of ''shim pulses'', i.e. modulated, spatially constant, B{sub 0} gradient pulses together with spatially homogeneous adiabatic frequency sweeps to induce non-linear phase shifts in three dimensions. An intuitive understanding of the approach can be obtained from the following: An adiabatic full passage applied to transverse magnetization effectively rotates the magnetization in the transverse plane with an amount that depends on the frequency offset. In homogeneous B{sub 0} this gives rise to a ''phase roll'' across the NMR spectrum. If the adiabatic full passage is applied in the presence of a constant B{sub 0} gradient, a phase shift approximately linear in space will be the result. A second adiabatic passage reverses this phase shift and the adiabatic double passage constitutes effectively a 360{sup o} pulse. However, if the amplitude of the B{sub 0} gradient is changing during the adiabatic passages, phase shifts, which are non-linear in space, can be achieved. With a proper choice of the RF and gradient modulation functions, the phase dispersion from the inhomogeneous B{sub 0} can be canceled. Application of a shim pulse between each detected point in the time-domain NMR signal yields an NMR spectrum free from the broadening caused by the B{sub 0} inhomogeneity.

Topgaard, Daniel; Martin, Rachel W.; Sakellariou, Dimitris; Meriles, Carlos; Pines, Alexander

2004-05-19

77

Heteronuclear Double-Quantum MAS NMR Spectroscopy in Dipolar Solids  

NASA Astrophysics Data System (ADS)

A new pulse sequence for high-resolution solid-state heteronuclear double-quantum MAS NMR spectroscopy of dipolar-coupled spin- {1}/{2} nuclei is introduced. It is based on the five-pulse sequence known from solution-state NMR, which is here applied synchronously to both spin species. The heteronuclear double-quantum (HeDQ) spinning-sideband patterns produced by this experiment are shown to be sensitive to the heteronuclear distance, as well as the relative orientations of the chemical-shift and dipolar tensors. In particular, it is shown that the HeDQ patterns exhibit an enhanced sensitivity to the chemical shielding tensors as compared with the single-quantum spinning-sideband patterns. The detection of HeDQ patterns via the I and S spins is discussed. The isolated 13C- 1H spin pair in deuterated ammonium formate with 13C in natural abundance was chosen as a model system, and the perturbing influence of dipolar couplings to surrounding protons on the 13C- 1H DQ coherence is discussed. The pulse sequence can also be used as a heteronuclear double-quantum filter, hence providing information about heteronuclear couplings, and thus allowing the differentiation of quaternary and CH n bonded carbons. The elucidation of 13C- 1H dipolar proximities is presented for a sample of bisphenol A polycarbonate with 13C in natural abundance, recorded with a broadband version of the synchronized five-pulse sequence.

Saalwächter, Kay; Graf, Robert; Demco, Dan E.; Spiess, Hans W.

1999-08-01

78

Protein Motions and Folding Investigated by NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

NMR spin relaxation spectroscopy is a powerful experimental approach for globally characterizing conformational dynamics of proteins in solution. Laboratory frame relaxation measurements are sensitive to overall rotational diffusion and internal motions on picosecond-nanosecond time scales, while rotating frame relaxation measurements are sensitive to chemical exchange processes on microsecond-millisecond time scales. The former approach is illustrated by ^15N laboratory-frame relaxation experiments as a function of temperature for the helical subdomain HP36 of the F-actin-binding headpiece domain of chicken villin. The data are analyzed using the model-free formalism to characterize order parameters and effective correlation times for intramolecular motions of individual ^15N sites. The latter approach is illustrated by ^13C Carr-Purcell-Meiboom-Gill relaxation measurements for the de novo designed ?_2D protein and by ^15N rotating-frame relaxation measurements for the peripheral subunit-binding domain (PSBD) from the dihydrolopoamide acetyltransferase component of the pyruvate dehydrogenase multienzyme complex from Bacillus stearothermophilus. These experiments are used to determine the folding and unfolding kinetic rate constants for the two proteins. The results for HP36, ?_2D, and PSBD illustrate the capability of current NMR methods for characterizing dynamic processes on multiple time scales in proteins.

Palmer, Arthur

2002-03-01

79

Structure determination of bioactive galloyl derivatives by NMR spectroscopy.  

PubMed

The investigation of the chemical constituents of Symplocos racemosa Roxb led to the isolation of two new glycosides, symcomoside A (1) and symcomoside B (2), together with one known glycoside, tortoside C (3), which is reported for the first time from this plant. The structures of the new compounds were determined by 1D and 2D homonuclear and heteronuclear NMR spectroscopy, from chemical evidence and by comparison with published data for closely related compounds. Symcomoside B (2) showed potent inhibitory activity against alpha-glucosidase in a concentration-dependent fashion with an IC50 value of 0.733 +/- 0.033 mM whereas symcomoside A (1) showed very weak inhibitory activity against alpha-glucosidase (9.90% in 0.70 mM). PMID:15772993

Ahmad, Viqar Uddin; Zubair, Muhammad; Athar Abbasi, Muhammad; Abid Rashid, Muhammad; Rasool, Nasir; Nahar Khan, Shamsun; Iqbal Choudhary, M; Kousar, Farzana

2005-06-01

80

Regularized Partial Least Squares with an Application to NMR Spectroscopy  

PubMed Central

High-dimensional data common in genomics, proteomics, and chemometrics often contains complicated correlation structures. Recently, partial least squares (PLS) and Sparse PLS methods have gained attention in these areas as dimension reduction techniques in the context of supervised data analysis. We introduce a framework for Regularized PLS by solving a relaxation of the SIMPLS optimization problem with penalties on the PLS loadings vectors. Our approach enjoys many advantages including flexibility, general penalties, easy interpretation of results, and fast computation in high-dimensional settings. We also outline extensions of our methods leading to novel methods for non-negative PLS and generalized PLS, an adoption of PLS for structured data. We demonstrate the utility of our methods through simulations and a case study on proton Nuclear Magnetic Resonance (NMR) spectroscopy data.

Allen, Genevera I.; Peterson, Christine; Vannucci, Marina; Maletic-Savatic, Mirjana

2014-01-01

81

Carbohydrate dynamics at a micellar surface: GD1a headgroup transformations revealed by NMR spectroscopy.  

PubMed Central

The conformational dynamics of the carbohydrate headgroup of ganglioside GD1a, NeuAc alpha 2-->3Gal beta 1-->3GalNAc beta 1-->4[NeuAc alpha 2-->3]Gal beta 1-->4Glc beta 1-->1Cer, anchored in a perdeuterated dodecylphosphocholine micelle in aqueous solution, were probed by high resolution NMR spectroscopy. The observed 1H/1H NOE interactions revealed conformational averaging of the terminal NeuAc alpha 2-->3Gal and Gal beta 1-->3GalNAc glycosidic linkages. The pronounced flexibility of this trisaccharide moiety was substantiated further by two-dimensional proton-detected 13C T1, T1 rho and 1H/13C NOE measurements. The anchoring effect of the micelle allowed the detection of conformational fluctuations of the headgroup on the time scale of a few hundred picoseconds. NMR experiments performed on the GD1a/DPC micelles in H2O at low temperatures permitted the observation of hydroxyl proton resonances, contributing valuable conformational information.

Poppe, L; van Halbeek, H; Acquotti, D; Sonnino, S

1994-01-01

82

Detection of Taurine in Biological Tissues by 33S NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

The potential of 33S NMR spectroscopy for biochemical investigations on taurine (2-aminoethanesulfonic acid) is explored. It is demonstrated that 33S NMR spectroscopy allows the selective and unequivocal identification of taurine in biological samples. 33S NMR spectra of homogenated and intact tissues are reported for the first time, together with the spectrum of a living mollusc. Emphasis is placed on the importance of choosing appropriate signal processing methods to improve the quality of the 33S NMR spectra of biological tissues.

Musio, Roberta; Sciacovelli, Oronzo

2001-12-01

83

Improving the resolution in proton-detected through-space heteronuclear multiple quantum correlation NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Connectivities and proximities between protons and low-gamma nuclei can be probed in solid-state NMR spectroscopy using two-dimensional (2D) proton-detected heteronuclear correlation, through Heteronuclear Multiple Quantum Correlation (HMQC) pulse sequence. The indirect detection via protons dramatically enhances the sensitivity. However, the spectra are often broadened along the indirect F1 dimension by the decay of heteronuclear multiple-quantum coherences under the strong 1H-1H dipolar couplings. This work presents a systematic comparison of the performances of various decoupling schemes during the indirect t1 evolution period of dipolar-mediated HMQC (D-HMQC) experiment. We demonstrate that 1H-1H dipolar decoupling sequences during t1, such as symmetry-based schemes, phase-modulated Lee-Goldburg (PMLG) and Decoupling Using Mind-Boggling Optimization (DUMBO), provide better resolution than continuous wave 1H irradiation. We also report that high resolution requires the preservation of 1H isotropic chemical shifts during the decoupling sequences. When observing indirectly broad spectra presenting numerous spinning sidebands, the D-HMQC sequence must be fully rotor-synchronized owing to the rotor-synchronized indirect sampling and dipolar recoupling sequence employed. In this case, we propose a solution to reduce artefact sidebands caused by the modulation of window delays before and after the decoupling application during the t1 period. Moreover, we show that 1H-1H dipolar decoupling sequence using Smooth Amplitude Modulation (SAM) minimizes the t1-noise. The performances of the various decoupling schemes are assessed via numerical simulations and compared to 2D 1H-{13C} D-HMQC experiments on [U-13C]-L-histidine?HCl?H2O at various magnetic fields and Magic Angle spinning (MAS) frequencies. Great resolution and sensitivity enhancements resulting from decoupling during t1 period enable the detection of heteronuclear correlation between aliphatic protons and ammonium 14N sites in L-histidine?HCl?H2O.

Shen, Ming; Trébosc, J.; Lafon, O.; Pourpoint, F.; Hu, Bingwen; Chen, Qun; Amoureux, J.-P.

2014-08-01

84

Isotope labeling for solution and solid-state NMR spectroscopy of membrane proteins.  

PubMed

In this chapter, we summarize the isotopic labeling strategies used to obtain high-quality solution and solid-state NMR spectra of biological samples, with emphasis on integral membrane proteins (IMPs). While solution NMR is used to study IMPs under fast tumbling conditions, such as in the presence of detergent micelles or isotropic bicelles, solid-state NMR is used to study the structure and orientation of IMPs in lipid vesicles and bilayers. In spite of the tremendous progress in biomolecular NMR spectroscopy, the homogeneity and overall quality of the sample is still a substantial obstacle to overcome. Isotopic labeling is a major avenue to simplify overlapped spectra by either diluting the NMR active nuclei or allowing the resonances to be separated in multiple dimensions. In the following we will discuss isotopic labeling approaches that have been successfully used in the study of IMPs by solution and solid-state NMR spectroscopy. PMID:23076578

Verardi, Raffaello; Traaseth, Nathaniel J; Masterson, Larry R; Vostrikov, Vitaly V; Veglia, Gianluigi

2012-01-01

85

NMR spectroscopy for determination of cationic polymer concentrations.  

PubMed

Organic polyelectrolytes are utilized extensively in wastewater treatment, but their fate after use is poorly understood. Analytical methods used for polymer determination in less complex systems appear to fail in application to wastewater systems, contributing to the lack of knowledge. Thus, the development of 1H NMR spectroscopy is reported here for specifically quantitating certain cationic flocculant polymers in environmental samples. Proton observe frequencies of 250 or 400 MHz proton were used. A copolymer of acrylamide and acryloyloxyethyltrimethylammonium chloride was used, representative of cationic flocculant polymers possessing quaternary ammonium groups with terminal methyls that provide a sharp singlet at a chemical shift of approximately 3.06 ppm. A strong linear relationship was demonstrated between polymer concentration and either height or area of this peak. Recoveries were up to 96% at higher concentrations (250 mg/L), and were greater than when using viscosity or charge titration methods for polymer determination. Lesser recoveries at lower concentrations (70% at 5 mg/L) were attributed to adsorptive losses. The detection limit of this method was determined to be <0.5 mg/L. Use of the method was exemplified by analysis of anaerobically digested sludges for residual polymer following a range of dosages, showing the resulting isotherm. PMID:12108718

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

2002-05-01

86

Communication: Phase incremented echo train acquisition in NMR spectroscopy.  

PubMed

We present an improved and general approach for implementing echo train acquisition (ETA) in magnetic resonance spectroscopy, particularly where the conventional approach of Carr-Purcell-Meiboom-Gill (CPMG) acquisition would produce numerous artifacts. Generally, adding ETA to any N-dimensional experiment creates an N + 1 dimensional experiment, with an additional dimension associated with the echo count, n, or an evolution time that is an integer multiple of the spacing between echo maxima. Here we present a modified approach, called phase incremented echo train acquisition (PIETA), where the phase of the mixing pulse and every other refocusing pulse, ?(P), is incremented as a single variable, creating an additional phase dimension in what becomes an N + 2 dimensional experiment. A Fourier transform with respect to the PIETA phase, ?(P), converts the ?(P) dimension into a ?p dimension where desired signals can be easily separated from undesired coherence transfer pathway signals, thereby avoiding cumbersome or intractable phase cycling schemes where the receiver phase must follow a master equation. This simple modification eliminates numerous artifacts present in NMR experiments employing CPMG acquisition and allows "single-scan" measurements of transverse relaxation and J-couplings. Additionally, unlike CPMG, we show how PIETA can be appended to experiments with phase modulated signals after the mixing pulse. PMID:22697523

Baltisberger, Jay H; Walder, Brennan J; Keeler, Eric G; Kaseman, Derrick C; Sanders, Kevin J; Grandinetti, Philip J

2012-06-01

87

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

SciTech Connect

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

Alam, Todd Michael; McIntyre, Sarah K.

2011-05-01

88

Stereochemistry Determination by Powder X-ray Diffraction Analysis and NMR Spectroscopy Residual Dipolar Couplings  

SciTech Connect

A matter of technique: For a new steroidal lactol, jaborosalactol 24 (1), isolated from Jaborosa parviflora, NMR spectroscopy residual dipolar couplings and powder X-ray diffraction analysis independently gave the same stereochemistry at C23-C26. Conventional NMR spectroscopic techniques, such as NOE and {sup 3}J coupling-constant analysis failed to unambiguously determine this stereochemistry.

Garcia, M.; Pagola, S; Navarro-Vasquez, A; Phillips, D; Gayathri, C; Krakauer, H; Stephens, P; Nicotra, V; Gil, R

2009-01-01

89

Zinc Dialkyldithiophosphate Oxidation by Cumene Hydroperoxide: Kinetic Studies by Raman and P NMR Spectroscopy  

Microsoft Academic Search

The oxidation of zinc dialkyldithiophosphates (ZDDPs) by cumene hydroperoxide in cyclohexane is studied by Raman and P NMR spectroscopy. The reaction proceeds in two main stages: oxidation of ZDDP to basic ZDDP, and oxidation of basic ZDDP to other products. Observation of phosphorus-containing reaction products by the two techniques yields approximate rate coefficients for the two stages. P NMR spectra

J. L. Paddy; N. C. J. Lee; D. N. Waters; W. Trott

1990-01-01

90

Measurement of Solution Viscosity via Diffusion-Ordered NMR Spectroscopy (DOSY)  

ERIC Educational Resources Information Center

Increasingly, the undergraduate chemistry curriculum includes nuclear magnetic resonance (NMR) spectroscopy. Advanced NMR techniques are often taught including two-dimensional gradient-based experiments. An investigation of intermolecular forces including viscosity, by a variety of methods, is often integrated in the undergraduate physical and…

Li, Weibin; Kagan, Gerald; Hopson, Russell; Williard, Paul G.

2011-01-01

91

Isotope labeling methods for studies of excited protein states by relaxation dispersion NMR spectroscopy  

Microsoft Academic Search

The utility of nuclear magnetic resonance (NMR) spectroscopy as a tool for the study of biomolecular structure and dynamics has benefited from the development of facile labeling methods that incorporate NMR active probes at key positions in the molecule. Here we describe a protocol for the labeling of proteins that facilitates their study using a technique that is sensitive to

Patrik Lundström; Pramodh Vallurupalli; D Flemming Hansen; Lewis E Kay

2009-01-01

92

Determination of rank and kerogen type by high resolution NMR spectroscopy  

Microsoft Academic Search

Nuclear magnetic resonance (NMR) spectroscopy is a nondestructive technique for measuring the chemical and structural properties of organic matter. Although used in organic geochemistry for the past 14 years, the technique has continually undergone refinement. Initially, only the aromatic and aliphatic signal areas of the carbon NMR spectrum could be measured. Carboxylic groups as well as oxygen-substituted groups on aromatic

W. W. Dickinson; J. D. Collen; R. H. Newman

1990-01-01

93

Trends in solid-state NMR spectroscopy and their relevance for bioanalytics  

Microsoft Academic Search

Based on continuous methodical advances and developments, solid-state NMR spectroscopy has become a powerful tool for the\\u000a investigation of various materials, including polymers, glasses, zeolites, fullerenes, and many others. During the past decade,\\u000a solid-state NMR spectroscopy also found increasing interest for the study of biomolecules. For example, membrane proteins\\u000a reconstituted into lipid environments such as bilayers or vesicles, protein aggregates

Silvia Paasch; Eike Brunner

2010-01-01

94

Studies of Molecular Dynamics by Solid State Deuterium NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

The rotational dynamics of molecules in a number of solid systems were followed by variable temperature deuterium (^2H), nuclear magnetic resonance (NMR) spectroscopy via changes in the spectral lineshapes and spin-lattice relaxation times (T _1). First the pure solid trimethylamine-borane adduct, (CH_3)_3NBH_3, was studied. For a methyl deuterated sample, T _1 measurements yielded two T_1 minima, 6.9 ms and 4.3 ms corresponding to the slowing of methyl and trimethyl rotation, respectively, with decreasing temperature. Activation energies for methyl and trimethyl rotation, obtained from fitting the T _1 curve as a function of temperature, were 32.8 and 15.0 kJ/mol, respectively; simulations of the spectral lineshapes gave 26.6 and 18.9 kT/mol, respectively. Fitting of the ^2H T_1 curve for the borane deuterated sample gave a BH _3 rotation activation energy of 14.1 kT/mol and a ^2H quadrupolar coupling constant, chi, of 101 kHz. The activation energy for BH_3 rotation obtained from the spectral lineshape simulations gave 12.6 kT/mol. A series of deuterated organic chalcogen cations: (CH_3)_3S^+, (CH_3)_3Se^+ and (CH_3)_3Te^+, were ion exchanged into the cavities of sodium Mordenite LZ-M5 and the dynamics of these guests within the hydrated zeolite were followed by ^2H NMR. All three undergo isotropic motion above about -80 to -90^circC. Below this temperature two superimposed ^2H powder spectra appear; the broad lineshape is consistent with only methyl rotation in a hindered, coordinated site, and the other narrow lineshape is due to both methyl and trimethyl rotation in a less hindered, uncoordinated site. As the temperature is lowered the population of the lower energy coordinated site increases. Relative peak areas yield adsorption enthalpies of 6.7, 7.8 and 10.0 kJ/mol for (CH_3)_3S^+, (CH_3)_3Se^+ and (CH_3)_3Te^+, respectively. The series of methyl deuterated ammonium and phosphonium cations: (CH_3)NH_3^+ , (CH_3)_2NH^+ , (CH_3)_3NH^+ and (CH_3)_4P^+ , were also ion-exchanged into Mordenite. It is shown that these cations also undergo exchange between hindered and unhindered sites. The motion of the cations is strongly influenced by the number of N-H hydrogen bonds available.

Zhao, Baiyi

95

Synthesis, determination of p K a values and GIAO NMR calculations of some new 3-alkyl-4-( p-methoxybenzoylamino)-4,5-dihydro-1 H-1,2,4-triazol-5-ones  

Microsoft Academic Search

3-Alkyl-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) reacted with p-methoxybenzoyl chloride to afford the corresponding 3-alkyl-4-(p-methoxybenzoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3). Five newly synthesized compounds have been characterized by elemental analyses, IR, 1H NMR, 13C NMR and UV spectral data. The newly synthesized compounds 3 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as acetonitrile, isopropyl alcohol, tert-butyl alcohol and N,N-dimethylformamide, and the half-neutralization potential values

Haydar Yüksek; Muzaffer Alkan; ?ule Bahçeci; Ismail Cakmak; Zafer Ocak; Haci Baykara; Ozlem Akta?; Elif A?yel

2008-01-01

96

Applications of high-resolution solid-state NMR spectroscopy in food science.  

PubMed

The principal applications of high-resolution solid-state NMR spectroscopy, in the field of food science, are reviewed, after a short general introduction, mainly focusing on the potential of these investigations, which are, today, routine tools for resolving technological problems. Selected examples of the applications in the field of food science of high-resolution solid-state NMR spectroscopy both in (13)C and in (1)H NMR particularly illustrative of the results obtainable are reported in some detail. PMID:18821771

Bertocchi, Fabio; Paci, Maurizio

2008-10-22

97

Fast automated NMR spectroscopy of short-lived biological samples.  

PubMed

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

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

2012-05-01

98

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

99

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

PubMed

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

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

2003-08-13

100

Study of the complexation of risperidone and 9-hydroxyrisperidone with cyclodextrin hosts using affinity capillary electrophoresis and (1)H NMR spectroscopy.  

PubMed

The complexation of risperidone (Risp) and 9-hydroxyrisperidone (9-OH-Risp), atypical antipsychotics, with seven cyclodextrins (CDs) of pharmaceutical interest (native and hydroxypropylated (HP) alpha-, beta-, gamma-CDs and methyl (Me)-beta-CD) was studied by affinity capillary electrophoresis (ACE) and nuclear magnetic resonance spectroscopy (NMR) for acidic pH 2.5 and physiological pH 7.4. The 1:1 stoichiometry of the complexes was established by (1)H NMR spectroscopy using the continuous variation method developed by Job. The apparent binding constants of the 14 complexes at both pH were determined by ACE through the linear Scott's plots. The NMR spectroscopy investigation of the binding constants was achieved for the two CDs allowing the highest complexation: the beta-CD and Me-beta-CD. Both ACE and NMR spectroscopy studies provide similar conclusions by considering the influence of the 9-hydroxylation, the influence of the CD substitution and the influence of the pH. Moreover, the NMR spectroscopy results have allowed to suppose a pH-dependent inclusion mechanism. A thermodynamic study was then performed by ACE at both pH for the Risp.Me-beta-CD and 9-OH-Risp.Me-beta-CD complexes: the opposite signs of the entropic change (DeltaS degrees <0 at pH 2.5 and DeltaS degrees >0 at pH 7.4) confirms the influence of the pH on the complexation mechanism and the possible difference in the depth of the analyte inclusion in the hydrophobic cavity of the CD. Last, the two-dimensional ROESY (rotating-frame Overhauser spectroscopy) ((1)H-(1)H) and HOESY (heteronuclear Overhauser effect spectroscopy) ((19)F-(1)H) experiments have proved the inclusion of the aromatic part of the Risp and 9-OH-Risp in the hydrophobic CD cavity and lead us to propose a model of complexation. PMID:19013582

Danel, Cécile; Azaroual, Nathalie; Brunel, Albane; Lannoy, Damien; Vermeersch, Gaston; Odou, Pascal; Vaccher, Claude

2008-12-26

101

Fast proton exchange in histidine: measurement of rate constants through indirect detection by NMR spectroscopy.  

PubMed

Owing to its imidazole side chain, histidine participates in various processes such as enzyme catalysis, pH regulation, metal binding, and phosphorylation. The determination of exchange rates of labile protons for such a system is important for understanding its functions. However, these rates are too fast to be measured directly in an aqueous solution by using NMR spectroscopy. We have obtained the exchange rates of the NH3(+) amino protons and the labile NH(?2) and NH(?1) protons of the imidazole ring by indirect detection through nitrogen-15 as a function of temperature (272?KH (1.3

Sehgal, Akansha Ashvani; Duma, Luminita; Bodenhausen, Geoffrey; Pelupessy, Philippe

2014-05-19

102

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

103

Quantitative Determination of Carthamin in Carthamus Red by 1H-NMR Spectroscopy.  

PubMed

Carthamus Red is a food colorant prepared from the petals of Carthamus tinctorius (Asteraceae) whose major pigment is carthamin. Since an authentic carthamin standard is difficult to obtain commercially for the preparation of calibration curves in HPLC assays, we applied (1)H-NMR spectroscopy to the quantitative determination of carthamin in commercial preparations of Carthamus Red. Carthamus Red was repeatedly extracted in methanol and the extract was dissolved in pyridine-d(5) containing hexamethyldisilane (HMD) prior to (1)H-NMR spectroscopic analysis. The carthamin contents were calculated from the ratios of singlet signal intensities at approximately ?: 9.3 derived from H-16 of carthamin to those of the HMD signal at ?: 0. The integral ratios exhibited good repeatability among NMR spectroscopic analyses. Both the intra-day and inter-day assay variations had coefficients of variation of <5%. Based on the coefficient of absorption, the carthamin contents of commercial preparations determined by (1)H-NMR spectroscopy correlated well with those determined by colorimetry, although the latter were always approximately 1.3-fold higher than the former, irrespective of the Carthamus Red preparations. In conclusion, the quantitative (1)H-NMR spectroscopy used in the present study is simple and rapid, requiring no carthamin standard for calibration. After HMD concentration has been corrected using certified reference materials, the carthamin contents determined by (1)H-NMR spectroscopy are System of Units (SI)-traceable. PMID:24436958

Yoshida, Takamitsu; Terasaka, Kazuyoshi; Kato, Setsuko; Bai, Fan; Sugimoto, Naoki; Akiyama, Hiroshi; Yamazaki, Takeshi; Mizukami, Hajime

2013-01-01

104

Applications of toroids in high-pressure NMR spectroscopy  

SciTech Connect

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

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

1995-12-01

105

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

106

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

NASA Astrophysics Data System (ADS)

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

Boykin, David W.; Kumar, Arvind

1993-10-01

107

NMR spectroscopy of RNA duplexes containing pseudouridine in supercooled water.  

PubMed

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

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

2005-07-01

108

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

109

Metabolomic analysis of methyl jasmonate treated Brassica rapa leaves by 2-dimensional NMR spectroscopy  

Microsoft Academic Search

The metabolomic analysis of Brassica rapa leaves treated with methyl jasmonate was performed using 2-dimensional J-resolved NMR spectroscopy combined with multivariate data analysis. The principal component analysis of the J-resolved NMR spectra showed discrimination between control and methyl jasmonate treated plants by principal components 1 and 2. While the level of glucose, sucrose and amino acids showed a decrease after

Yun-Sa Liang; Young Hae Choi; Hye Kyong Kim; Huub J. M. Linthorst; Robert Verpoorte

2006-01-01

110

Mapping the encounter state of a transient protein complex by PRE NMR spectroscopy  

Microsoft Academic Search

Many biomolecular interactions proceed via a short-lived encounter state, consisting of multiple, lowly-populated species\\u000a invisible to most experimental techniques. Recent development of paramagnetic relaxation enhancement (PRE) nuclear magnetic\\u000a resonance (NMR) spectroscopy has allowed to directly visualize such transient intermediates in a number of protein-protein\\u000a and protein-DNA complexes. Here we present an analysis of the recently published PRE NMR data for

Alexander N. Volkov; Marcellus Ubbink; Nico A. J. van Nuland

2010-01-01

111

Quantitating metabolites in protein precipitated serum using NMR spectroscopy.  

PubMed

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

Nagana Gowda, G A; Raftery, Daniel

2014-06-01

112

Variable angle NMR spectroscopy and its application to the measurement of residual chemical shift anisotropy  

NASA Astrophysics Data System (ADS)

The successful measurement of anisotropic NMR parameters like residual dipolar couplings (RDCs), residual quadrupolar couplings (RQCs), or residual chemical shift anisotropy (RCSA) involves the partial alignment of solute molecules in an alignment medium. To avoid any influence of the change of environment from the isotropic to the anisotropic sample, the measurement of both datasets with a single sample is highly desirable. Here, we introduce the scaling of alignment for mechanically stretched polymer gels by varying the angle of the director of alignment relative to the static magnetic field, which we call variable angle NMR spectroscopy (VA-NMR). The technique is closely related to variable angle sample spinning NMR spectroscopy (VASS-NMR) of liquid crystalline samples, but due to the mechanical fixation of the director of alignment no sample spinning is necessary. Also, in contrast to VASS-NMR, VA-NMR works for the full range of sample inclinations between 0° and 90°. Isotropic spectra are obtained at the magic angle. As a demonstration of the approach we measure 13C-RCSA values for strychnine in a stretched PDMS/CDCl 3 gel and show their usefulness for assignment purposes. In this context special care has been taken with respect to the exact calibration of chemical shift data, for which three approaches have been derived and tested.

Kummerlöwe, Grit; Grage, Stephan L.; Thiele, Christina M.; Kuprov, Ilya; Ulrich, Anne S.; Luy, Burkhard

2011-03-01

113

Insights into the metabolic response to traumatic brain injury as revealed by 13C NMR spectroscopy  

PubMed Central

The present review highlights critical issues related to cerebral metabolism following traumatic brain injury (TBI) and the use of 13C labeled substrates and nuclear magnetic resonance (NMR) spectroscopy to study these changes. First we address some pathophysiologic factors contributing to metabolic dysfunction following TBI. We then examine how 13C NMR spectroscopy strategies have been used to investigate energy metabolism, neurotransmission, the intracellular redox state, and neuroglial compartmentation following injury. 13C NMR spectroscopy studies of brain extracts from animal models of TBI have revealed enhanced glycolytic production of lactate, evidence of pentose phosphate pathway (PPP) activation, and alterations in neuronal and astrocyte oxidative metabolism that are dependent on injury severity. Differential incorporation of label into glutamate and glutamine from 13C labeled glucose or acetate also suggest TBI-induced adaptations to the glutamate-glutamine cycle.

Bartnik-Olson, Brenda L.; Harris, Neil G.; Shijo, Katsunori; Sutton, Richard L.

2013-01-01

114

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

115

Ensemble Quantum Computing by Liquid-State NMR Spectroscopy.  

National Technical Information Service (NTIS)

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

T. F. Havel D. G. Cory

2003-01-01

116

Simultaneous Nonlinear Least Squares Fitting Technique For NMR Spectroscopy  

Microsoft Academic Search

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

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

1993-01-01

117

Cryogenic probe 13C NMR spectroscopy of urine for metabonomic studies.  

PubMed

Cryogenic probe technology can significantly compensate for the inherently low sensitivity of natural abundance 13C NMR spectroscopy. This now permits its routine use in NMR spectroscopy of biofluids, such as urine or plasma, with acquisition times that enable a high throughput of samples. Metabonomic studies often generate numerous samples in order to characterize fully the time-dependent biochemical response to stimuli, but until now, they have been largely conducted using 1H NMR spectroscopy because of its high sensitivity and hence efficient data acquisition. Here, we demonstrate that information-rich 13C NMR spectra of rat urine can be obtained using appropriately short acquisition times suitable for biochemical samples when using a cryogenic probe. Furthermore, these data were amenable to automated pattern recognition analysis, which produced a profile of the metabolic response to the model hepatotoxin hydrazine that was consistent with earlier studies. Thus, a new source of detailed and complementary information is available to metabonomics using cryogenic probe 13C NMR spectroscopy. PMID:12236374

Keun, Hector C; Beckonert, Olaf; Griffin, Julian L; Richter, Christian; Moskau, Detlef; Lindon, John C; Nicholson, Jeremy K

2002-09-01

118

Measurement of pH by NMR Spectroscopy in Concentrated Aqueous Fluoride Buffers  

PubMed Central

An NMR spectroscopic technique has been developed to give rapid, accurate pH measurements on tenth-milliliter samples of concentrated acidic aqueous solutions buffered by fluoride ion in the pH 1.5 – 4.5 range. The fluoride 19F chemical shift has been calibrated as a function of pH at 0.1 and 1.0 M concentration by reference to an internal 3-fluoropyridine standard. Subsequent measurements of fluoride buffer pH required no additives and only two NMR spectra in the presence of an external reference standard.

Gerken, James B.

2010-01-01

119

Characterization of the essential oil of Agastache rugosa by NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The composition of essential oil from Agastache rugosa (Fish. et Mey) O.Kuntze was studied by 1H and 13C NMR spectroscopy. Essential oil was isolated from the aerial part of plants growing in the Central Botanical Garden of the NAS of Belarus during flowering and fruiting. The oil chemical composition was found to depend little on the sampling time. It was shown that NMR spectroscopy could be successfully used to both monitor the content of the hepatotoxic substance (pulegone) and characterize the quality and authenticity of essential oils.

Skakovskii, E. D.; Kiselev, W. P.; Tychinskaya, L. Yu.; Schutova, A. G.; Gonsharova, L. W.; Spiridowish, E. W.; Bovdey, N. A.; Kiselev, P. A.; Gaidukevich, O. A.

2010-07-01

120

DSP-based on-line NMR spectroscopy using an anti-Hebbian learning algorithm  

SciTech Connect

This paper describes a nuclear magnetic resonance (NMR) system that uses an adaptive algorithm to carry out real-time NMR spectroscopy. The system employs a digital signal processor (DSP) chip to regulate the transmitted and received signal together with spectral analysis of the received signal to determine free induction decay (FID). To implement such a signal-processing routine for detection of the desired signal, an adaptive line enhancer filter that uses an anti-Hebbian learning algorithm is applied to the FID spectra. The results indicate that the adaptive filter can be a reliable technique for on-line spectroscopy study.

Razazian, K.; Dieckman, S.L.; Raptis, A.C. [Argonne National Lab., IL (United States). Energy Technology Div.; Bobis, J.P. [Argonne National Lab., IL (United States). Energy Technology Div.]|[Northern Illinois Univ., DeKalb, IL (United States)

1995-07-01

121

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

ERIC Educational Resources Information Center

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

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

2012-01-01

122

From Molecular Structure to Global Processes : NMR Spectroscopy in Analytical/Environmental Chemistry  

NASA Astrophysics Data System (ADS)

NMR Spectroscopy is arguably the most powerful tool to elucidate structure and probe molecular interactions. A range of NMR approaches will be introduced with emphasis on addressing and understanding structure and reactivity of soil organic matter at the molecular level. The presentation will be split into three main sections. The first section will look at evidence from advanced NMR based approaches that when considered synergistically describes the major structural components in soil organic matter. Multidimensional NMR spectroscopy (1-3D NMR), automated pattern matching, spectral simulations, diffusion NMR and hybrid-diffusion NMR will be introduced in context of molecular structure. Finally the structural components in soil will be contrasted to those found in aquatic dissolved organic matter. Secondly molecular interactions of natural organic matter will be considered. Advanced structural studies have provided detailed spectral assignments which in turn permit the reactivity of various soil components to be elucidated. Aggregation and self-association of soil and dissolved organic matter will be discussed along with the structural components likely responsible for aggregation/colloid formation. Interactions of soil organic matter with anthropogenic chemicals will also be considered and NMR techniques based on "Saturation Transfer Difference" introduced. These techniques are extremely powerful and can be used to both; describe mechanistically how anthropogenic chemicals sorb to whole soils and identify the structural components (lignin, protein, cellulose, etc..) that are responsible for the binding/sorption in soil. In the last section, the "big questions" and challenges facing the field will be considered along with some novel experimental NMR based approaches that should, in future, assist in providing answers to these questions.

Simpson, A.

2009-04-01

123

Diffusion exchange NMR spectroscopy in inhomogeneous magnetic fields  

NASA Astrophysics Data System (ADS)

Two-dimensional diffusion exchange experiments in the presence of a strong, static magnetic field gradient are presented. The experiments are performed in the stray field of a single sided NMR sensor with a proton Larmor frequency of 11.7 MHz. As a consequence of the strong and static magnetic field gradient the magnetization has contributions from different coherence pathways. In order to select the desired coherence pathways, a suitable phase cycling scheme is introduced. The pulse sequence is applied to study diffusion as well as the molecular exchange properties of organic solvents embedded in a mesoporous matrix consisting of a sieve of zeolites with a pore size of 0.8 nm and grain size of 2 ?m. This pulse sequence extends the possibilities of the study of transport properties in porous media, with satisfying sensitivity in measurement times of a few hours, in a new generation of relatively inexpensive low-field NMR mobile devices.

Neudert, Oliver; Stapf, Siegfried; Mattea, Carlos

2011-02-01

124

New Insights into Glycopeptide Antibiotic Binding to Cell Wall Precursors using SPR and NMR Spectroscopy.  

PubMed

Glycopeptide antibiotics, such as vancomycin and teicoplanin, are used to treat life-threatening infections caused by multidrug-resistant Gram-positive pathogens. They inhibit bacterial cell wall biosynthesis by binding to the D-Ala-D-Ala C-terminus of peptidoglycan precursors. Vancomycin-resistant bacteria replace the dipeptide with the D-Ala-D-Lac depsipeptide, thus reducing the binding affinity of the antibiotics with their molecular targets. Herein, studies of the interaction of teicoplanin, teicoplanin-like A40926, and of their semisynthetic derivatives (mideplanin, MDL63,246, dalbavancin) with peptide analogues of cell-wall precursors by NMR spectroscopy and surface plasmon resonance (SPR) are reported. NMR spectroscopy revealed the existence of two different complexes in solution, when the different glycopeptides interact with Ac2KdAlaDAlaOH. Despite the NMR experimental conditions, which are different from those employed for the SPR measurements, the NMR spectroscopy results parallel those deduced in the chip with respect to the drastic binding difference existing between the D-Ala and the D-Lac terminating analogues, confirming that all these antibiotics share the same primary molecular mechanism of action and resistance. Kinetic analysis of the interaction between the glycopeptide antibiotics and immobilized AcKdAlaDAlaOH by SPR suggest a dimerization process that was not observed by NMR spectroscopy in DMSO solution. Moreover, in SPR, all glycopeptides with a hydrophobic acyl chain present stronger binding with a hydrophobic surface than vancomycin, indicating that additional interactions through the employed surface are involved. In conclusion, SPR provides a tool to differentiate between vancomycin and other glycopeptides, and the calculated binding affinities at the surface seem to be more relevant to in vitro antimicrobial activity than the estimations from NMR spectroscopy analysis. PMID:24805824

Trevińo, Juan; Bayón, Carlos; Ardá, Ana; Marinelli, Flavia; Gandolfi, Raffaella; Molinari, Francesco; Jimenez-Barbero, Jesús; Hernáiz, María J

2014-06-10

125

A comprehensive approach for quantitative lignin characterization by NMR spectroscopy.  

PubMed

A detailed approach for the quantification of different lignin structures in milled wood lignin (MWL) has been suggested using a combination of NMR techniques. 1H-13C heteronuclear multiple quantum coherence and quantitative 13C NMR of nonacetylated and acetylated spruce MWL have been found to have a synergetic effect, resulting in significant progress in the characterization of lignin moieties by NMR. About 80% of side chain moieties, such as different beta-O-4, dibenzodioxocin, phenylcoumaran, pinoresinol, and others, have been identified on the structural level. The presence of appreciable amounts of alpha-O-alkyl and gamma-O-alkyl ethers has been suggested. Although the quantification of various condensed moieties was less precise than for side chain structures, reliable information can be obtained. Comparison of the calculated results with known databases on spruce MWL structure shows that the suggested approach is rather informative and comparable with the information obtained from the combination of various wet chemistry methods. Discrepancies between the results obtained in this study and those previously published are discussed. PMID:15053520

Capanema, Ewellyn A; Balakshin, Mikhail Y; Kadla, John F

2004-04-01

126

Sensitivity enhancement of double quantum NMR spectroscopy by modified CPMG  

NASA Astrophysics Data System (ADS)

A modified Carr-Purcell-Meiboom-Gill (CPMG) sequence for sensitivity enhancement of dipolar coupled homonuclear spin pairs in static solid-state NMR is presented. The modified CPMG block uses the Hahn-solid-Hahn echo as basic element of the CPMG echo train to refocus the homonuclear dipolar coupling and chemical shift anisotropy. The new CPMG sequence is dubbed as Hahn-solid-Hahn Carr-Purcell-Meiboom-Gill (HSHCPMG). We demonstrate a gain in signal to noise ratio of approximately 4.2 using HSHCPMG sequence in double quantum filtered CP experiment for 5%-13C2-15N-glycine. The resulting gain in sensitivity in the spikelet spectrum does not compromise the anisotropic information that is available from static NMR lineshapes. As an example, relative orientation angles of chemical shift anisotropy tensors for the alpha and carbonyl carbons in glycine are determined from the 2D DOQSY experiment recorded with the HSHCPMG block in the acquisition dimension. The resultant relative orientation angles of the two CSA tensors are compared to those obtained from 2D DOQSY experiment acquired without sensitivity enhancement as well as to the data as available from single crystal NMR experiments.

Gowda, Chandrakala M.; Agarwal, Vipin; Kentgens, Arno P. M.

2012-10-01

127

13C NMR spectroscopy of copoly(arylenephthalide) derivatives with diphenyloxide and terphenyl fragments in the main chain.  

PubMed

(1) H and (13) ? NMR spectral assignments have been provided for low-molecular reference monomers, poly(diphenyleneoxidephthalide) and periodic copoly(arylenephthalide) derivatives such as AB, ABB, and ABBB (where A?=?terphenylenephthalide and B?=?diphenyleneoxidephthalide) using (1) H-(1) H COSY, (1) H-(13) C HSQC and HMBC NMR techniques. Distinctive (13) C NMR chemical shifts of a main chain have been observed containing fragments of similar structures and lateral phthalate groups being part of various diads. PMID:23921970

Kraikin, Vladimir A; Fatykhov, Akhnef A; Sakhipova, Il'nara I; Sedova, Elvira A; Egorov, Aleksandr E; Salazkin, Sergey N

2013-10-01

128

High-Resolution NMR Spectroscopy: An Alternative Fast Tool for Qualitative and Quantitative Analysis of Diacylglycerol (DAG) Oil  

Microsoft Academic Search

Multinuclear (1H, 13C, 31P) and multidimensional NMR spectroscopy was employed for the analysis of diacylglycerol (DAG) oil and the quantification\\u000a of its acylglycerols and acyl chains composition. A number of gradient selected two dimensional NMR techniques (TOCSY, HSQC-DEPT,\\u000a HSQC-TOCSY, and HMBC) facilitated the assignment of the complex one dimensional 1H- and 13C-NMR spectra. In several cases, the aforementioned 2D-NMR techniques

Emmanuel Hatzakis; Alexia Agiomyrgianaki; Sarantos Kostidis; Photis Dais

129

Citron and lemon under the lens of HR-MAS NMR spectroscopy.  

PubMed

High Resolution Magic Angle Spinning (HR-MAS) is an NMR technique that can be applied to semi-solid samples. Flavedo, albedo, pulp, seeds, and oil gland content of lemon and citron were studied through HR-MAS NMR spectroscopy, which was used directly on intact tissue specimens without any physicochemical manipulation. HR-MAS NMR proved to be a very suitable technique for detecting terpenes, sugars, organic acids, aminoacids and osmolites. It is valuable in observing changes in sugars, principal organic acids (mainly citric and malic) and ethanol contents of pulp specimens and this strongly point to its use to follow fruit ripening, or commercial assessment of fruit maturity. HR-MAS NMR was also used to derive the molar percentage of fatty acid components of lipids in seeds, which can change depending on the Citrus species and varieties. Finally, this technique was employed to elucidate the metabolic profile of mold flavedo. PMID:23871074

Mucci, Adele; Parenti, Francesca; Righi, Valeria; Schenetti, Luisa

2013-12-01

130

13C NMR spectroscopy for the quantitative determination of compound ratios and polymer end groups.  

PubMed

(13)C NMR spectroscopic integration employing short relaxation delays was evaluated as a quantitative tool to obtain ratios of diastereomers, regioisomers, constitutional isomers, mixtures of unrelated compounds, peptoids, and sugars. The results were compared to established quantitative methods such as (1)H NMR spectroscopic integration, gas chromatography, and high-performance liquid chromatography and were found to be within <3.4% of (1)H NMR spectroscopic values (most examples give results within <2%). Acquisition of the spectra took 2-30 min on as little as 10 mg of sample, proving the general utility of the technique. The simple protocol was extended to include end group analysis of low molecular weight polymers, which afforded results in accordance with (1)H NMR spectroscopy and matrix-assisted laser desorption-ionization time-of-flight spectrometry. PMID:24601654

Otte, Douglas A L; Borchmann, Dorothee E; Lin, Chin; Weck, Marcus; Woerpel, K A

2014-03-21

131

Metabolic fingerprinting of Ephedra species using 1H-NMR spectroscopy and principal component analysis.  

PubMed

The metabolomic analysis of Ephedra species was performed using 1H-NMR spectroscopy and multivariate data analysis. A broad range of metabolites could be detected by 1H-NMR spectroscopy without any chromatographic separation. The principal component analysis used to reduce the huge data set obtained from the 1H-NMR spectra of the plant extracts clearly discriminated three different Ephedra species. The major differences in Ephedra sinica, Ephedra intermedia and Ephedra distachya var. distachya were found to be due to benzoic acid analogues in the aqueous fraction and ephedrine-type alkaloids in the organic fraction. Based on this metabolomic recognition, one of nine commercial Ephedra materials evaluated was shown to be a mixture of Ephedra species. This method will be a useful tool for chemotaxonomic analysis and authentification of Ephedra species including quality control of plant materials. PMID:15635242

Kim, Hye Kyong; Choi, Young Hae; Erkelens, Cornelis; Lefeber, Alfons W M; Verpoorte, Robert

2005-01-01

132

The efficiency of DPPH as a polarising agent for DNP-NMR spectroscopy  

PubMed Central

The free radical 2,2-diphenyl-1-pycrylhydrazyl (DPPH) was tested as a polarising agent for fast dissolution dynamic nuclear polarisation (DNP) NMR spectroscopy. DPPH was found to be reasonably soluble in sulfolane and the optimum concentration for DNP is 20–40 mM depending upon whether short polarisation times or the maximum signal intensity is needed. W-band ESR measurements revealed that the ESR linewidth D of DPPH is intermediate between that of BDPA and 4-oxo-TEMPO. Several thousand-fold NMR signal enhancements in the liquid-state were achieved for 13C, 15N, 89Y, and 109Ag compounds, demonstrating that DPPH can be added to the list of polarising agents for DNP-NMR spectroscopy. Furthermore, the hydrophobic DPPH free radical can be easily filtered out from the dissolution liquid when water is used as the dissolution solvent.

Lumata, Lloyd; Merritt, Matthew; Khemtong, Chalermchai; Ratnakar, S. James; van Tol, Johan; Yu, Lu; Song, Likai

2012-01-01

133

Determination of glyphosate in biological fluids by 1H and 31P NMR spectroscopy.  

PubMed

Identification of glyphosate in four cases of poisoning, using nuclear magnetic resonance spectroscopy of biological fluids is reported. It has been performed by using a combination of 1H and 31P NMR analyses. Characterization of the N-(phosphonomethyl) glycine herbicide was achieved by chemical shift considerations and coupling constant patterns: CH2-(P) presents specific resonance at 3.12 ppm and appears as a doublet with a H-P characteristic coupling constant of 12.3 Hz. Moreover, resonances due to isopropylamine were present, confirming the ingestion of the considered trade formulation. After a calibration step, quantitation was performed by 1H and 31P NMR spectroscopy. The benefit and reliability of NMR investigations of biological fluids are discussed, particularly when the clinical picture is quite confusing. PMID:15240034

Cartigny, B; Azaroual, N; Imbenotte, M; Mathieu, D; Vermeersch, G; Goullé, J P; Lhermitte, M

2004-07-16

134

Slow motion of confined molecules: NMR and broadband dielectric spectroscopy investigations.  

PubMed

Nuclear magnetic resonance (NMR) and broadband dielectric spectroscopy are used to investigate the dynamics of small glass-forming molecules confined to restricted geometries. Ethylene glycol molecules are embedded in the supercages of NaX zeolites. The combined application of NMR and broadband dielectric spectroscopy advances the understanding of the slowing down of the motion near the glass transition temperature of these confined molecules. In combination with nuclear spin relaxation and nuclear magnetic resonance spectroscopy, dielectric relaxation studies on glass forming molecules allow conclusions on the character of the motion. High resolution 1H magic angle spinning (MAS) NMR measurements not only enable a characterisation of the state of the adsorbed molecules via a chemical shift analysis. By means of an analysis of MAS spinning sidebands we may also estimate a correlation time the meaning of which will be discussed in comparison to the results of longitudinal proton spin relaxation measurements. In addition to broadband dielectric spectroscopy slow molecular motions of partially deuterated ethylene glycol adsorbed in NaX are studied by means of 2H NMR line-shape analysis. PMID:18464423

Erdem, Ozlen F; Pampel, André; Michel, Dieter

2008-02-01

135

Structure Determination of Unknown Organic Liquids Using NMR and IR Spectroscopy: A General Chemistry Laboratory  

ERIC Educational Resources Information Center

This experiment introduced general chemistry students to the basic concepts of organic structures and to the power of spectroscopic methods for structure determination. Students employed a combination of IR and NMR spectroscopy to perform de novo structure determination of unknown alcohols, without being provided with a list of possible…

Pavel, John T.; Hyde, Erin C.; Bruch, Martha D.

2012-01-01

136

NMR imaging and spectroscopy of the mammalian central nervous system after heavy ion radiation  

SciTech Connect

NMR imaging, NMR spectroscopic, and histopathologic techniques were used to study the proton relaxation time and related biochemical changes in the central nervous system after helium beam in vivo irradiation of the rodent brain. The spectroscopic observations reported in this dissertation were made possible by development of methods for measuring the NMR parameters of the rodent brain in vivo and in vitro. The methods include (1) depth selective spectroscopy using an optimization of rf pulse energy based on a priori knowledge of N-acetyl aspartate and lipid spectra of the normal brain, (2) phase-encoded proton spectroscopy of the living rodent using a surface coil, and (3) dual aqueous and organic tissue extraction technique for spectroscopy. Radiation induced increases were observed in lipid and p-choline peaks of the proton spectrum, in vivo. Proton NMR spectroscopy measurements on brain extracts (aqueous and organic solvents) were made to observe chemical changes that could not be seen in vivo. Radiation-induced changes were observed in lactate, GABA, glutamate, and p-choline peak areas of the aqueous fraction spectra. In the organic fraction, decreases were observed in peak area ratios of the terminal-methyl peaks, the N-methyl groups of choline, and at a peak at 2.84 ppM (phosphatidyl ethanolamine and phosphatidyl serine resonances) relative to TMS. With histology and Evans blue injections, blood-brain barrier alternations were seen as early as 4 days after irradiation. 83 references, 53 figures.

Richards, T.

1984-09-01

137

High Resolution NMR Spectroscopy of Nanocrystalline Proteins at Ultra-High Magnetic Field  

SciTech Connect

Solid-state NMR (SSNMR) spectroscopy is a powerful tool for studying protein structure and function, uniquely able to address macroscopically disordered proteins. Insights from SSNMR include atomic-resolution structure, site-specific dynamics, metal center chemistry, and orientation of membrane proteins in bilayers.

Sperling, Lindsay J.; Nieuwkoop, Andrew J.; Lipton, Andrew S.; Berthold, Deborah A.; Rienstra, Chad M.

2010-02-01

138

Analysis of Epoxy Resin Formulations by exp 13 C NMR Spectroscopy.  

National Technical Information Service (NTIS)

The chloroform soluble components of several epoxy resin formulations were analyzed by exp 13 C NMR spectroscopy. The technique permits the components of an epoxy resin formulation to be identified on a routine basis with a high degree of confidence. Narm...

R. A. Assink F. T. Gurule

1981-01-01

139

An NMR spectroscopy study of bendaline-albumin interactions.  

PubMed

The complete assignment of the 1H and 13C NMR spectra of bendaline (BNDL) was performed by mono-dimensional and homo- and hetero-correlated two-dimensional NMR experiments. The interaction between bendaline and albumin was also studied by the analysis of the motional parameters spin-lattice relaxation times, allowing the motional state of the BNDL free and bound with albumin to be defined. In absence of albumin the indazolacetic and benzylic moieties are characterized by roughly the same mobility and by positive sigma (cross-relaxation rates) values. In the presence of the macromolecule, the indazolacetic and benzylic moieties and the lysine change their motional behaviour to different extents, as indicated by correlation times. Data obtained in absence and in presence of the protein show that the molecular moiety of the bendaline most involved in the binding with albumin is the fragment H-4 H-5. The binding constant was evaluated at 2.4x10(3)M(-1). PMID:12941290

Delfini, M; Bianchetti, C; Di Cocco, M E; Pescosolido, N; Porcelli, F; Rosa, R; Rugo, G

2003-10-01

140

Solid-state NMR adiabatic TOBSY sequences provide enhanced sensitivity for multidimensional high-resolution magic-angle-spinning 1H MR spectroscopy.  

PubMed

We propose a solid-state NMR method that maximizes the advantages of high-resolution magic-angle-spinning (HRMAS) applied to intact biopsies when compared to more conventional liquid-state NMR approaches. Theoretical treatment, numerical simulations and experimental results on intact human brain biopsies are presented. Experimentally, it is proven that an optimized adiabatic TOBSY (TOtal through Bond correlation SpectroscopY) solid-state NMR pulse sequence for two-dimensional 1H-1H homonuclear scalar-coupling longitudinal isotropic mixing provides a 20%-50% improvement in signal-to-noise ratio relative to its liquid-state analogue TOCSY (TOtal Correlation SpectroscopY). For this purpose we have refined the C9(15)1 symmetry-based 13C TOBSY pulse sequence for 1H MRS use and compared it to MLEV-16 TOCSY sequence. Both sequences were rotor-synchronized and implemented using WURST-8 adiabatic inversion pulses. As discussed theoretically and shown in simulations, the improved magnetization-transfer comes from actively removing residual dipolar couplings from the average Hamiltonian. Importantly, the solid-state NMR techniques are tailored to perform measurements at low temperatures where sample degradation is reduced. This is the first demonstration of such a concept for HRMAS metabolic profiling of disease processes, including cancer, from biopsies requiring reduced sample degradation for further genomic analysis. PMID:18556227

Andronesi, Ovidiu C; Mintzopoulos, Dionyssios; Struppe, Jochem; Black, Peter M; Tzika, A Aria

2008-08-01

141

Hadamard NMR spectroscopy for two-dimensional quantum information processing and parallel search algorithms.  

PubMed

Hadamard spectroscopy has earlier been used to speed-up multi-dimensional NMR experiments. In this work, we speed-up the two-dimensional quantum computing scheme, by using Hadamard spectroscopy in the indirect dimension, resulting in a scheme which is faster and requires the Fourier transformation only in the direct dimension. Two and three qubit quantum gates are implemented with an extra observer qubit. We also use one-dimensional Hadamard spectroscopy for binary information storage by spatial encoding and implementation of a parallel search algorithm. PMID:17011221

Gopinath, T; Kumar, Anil

2006-12-01

142

Mobility and Diffusion-Ordered Two-Dimensional NMR Spectroscopy  

Microsoft Academic Search

Mobility and diffusion-ordered two-dimensional nuclear magnetic resonance spectroscopy experiments have been developed for the analysis of mixtures. In the mobility -ordered experiments, the full range of positive and negative electrophoretic mobilities is displayed in one dimension and chemical shifts are displayed in the other. A concentric cylindrical tube electrophoresis chamber was designed to reduce the effective pathlength for current and

Kevin Freeman Morris

1993-01-01

143

Pushing the Limits of NMR Spectroscopy: In Situ analysis of Organic Matter in Natural Waters  

NASA Astrophysics Data System (ADS)

Dissolved Organic Matter (DOM) is ubiquitous in all natural waters and is known to play important roles in the carbon and nitrogen cycles, the transport and transformation of contaminants and nutrients, and health and biodiversity of aquatic species. Thus there is a great scientific need to further understand the composition, variability and reactivity of dissolved organic matter in the environment. Of all the analytical approaches employed to study DOM, NMR spectroscopy has provided the greatest insights into its general composition. However, conventional NMR studies often require a considerable amount of isolated DOM (mg quantities) and are adversely influenced by high salt and/or metal content which can result from sample concentration. Also there is concern that DOM can be altered during chemical isolation to varying extents and may not be completely representative of the material in its natural state. Here we demonstrate, that while very difficult, it is possible to obtain NMR spectra of Organic Matter in situ for practically all major bodies of water including groundwater, rainwater, seawater, and water from lakes and rivers. In sea water DOM is present at ~1ppm, and thus with a standard 5mm NMR probe (assuming ~300ľL volume inside the coil), only ~300ng of DOM is present. Furthermore, considering that the intensity of the water signal is many orders of magnitude greater than the weak signals from the DOM (itself a heterogeneous mixture) it is clear that such applications challenge the limits of modern NMR spectroscopy.

Simpson, A.; Lam, B.

2009-05-01

144

Urinary metabolic fingerprint of acute intermittent porphyria analyzed by (1)H NMR spectroscopy.  

PubMed

(1)H NMR is a nonbiased technique for the quantification of small molecules that could result in the identification and characterization of potential biomarkers with prognostic value and contribute to better understand pathophysiology of diseases. In this study, we used (1)H NMR spectroscopy to analyze the urinary metabolome of patients with acute intermittent porphyria (AIP), an inherited metabolic disorder of heme biosynthesis in which an accumulation of the heme precursors 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG) promotes sudden neurovisceral attacks, which can be life-threatening. Our objectives were (1) to demonstrate the usefulness of (1)H NMR to identify and quantify ALA and PBG in urines from AIP patients and (2) to identify metabolites that would predict the response to AIP crisis treatment and reflect differential metabolic reprogramming. Our results indicate that (1)H NMR can help to diagnose AIP attacks based on the identification of ALA and PBG. We also show that glycin concentration increases in urines from patients with frequent recurrences at the end of the treatment, after an initial decrease, whereas PBG concentration remains low. Although the reasons for this altered are elusive, these findings indicate that a glycin metabolic reprogramming occurs in AIPr patients and is associated with recurrence. Our results validate the proof of concept of the usefulness of (1)H NMR spectroscopy in clinical chemistry for the diagnosis of acute attack of AIP and identify urinary glycin as a potential marker of recurrence of AIP acute attacks. PMID:24437734

Carichon, Mickael; Pallet, Nicolas; Schmitt, Caroline; Lefebvre, Thibaud; Gouya, Laurent; Talbi, Neila; Deybach, Jean Charles; Beaune, Philippe; Vasos, Paul; Puy, Hervé; Bertho, Gildas

2014-02-18

145

Microcoil high-resolution magic angle spinning NMR spectroscopy.  

PubMed

We report the construction of a dual-channel microcoil nuclear magnetic resonance probehead allowing magic-angle spinning for mass-limited samples. With coils down to 235 mum inner diameter, this allows high-resolution solid-state NMR spectra to be obtained for amounts of materials of a few nanoliters. This is demonstrated by the carbon-13 spectrum of a tripeptide and a single silk rod, prepared from the silk gland of the Bombyx mori silkworm. Furthermore, the microcoil allows for radio frequency field strengths well beyond current probe technology, aiding in getting the highest possible resolution by efficiently decoupling the observed nuclei from the abundantly present proton nuclei. PMID:16819853

Janssen, Hans; Brinkmann, Andreas; van Eck, Ernst R H; van Bentum, P Jan M; Kentgens, Arno P M

2006-07-12

146

1 GHz NMR spectroscopy: innovation in magnet technology.  

PubMed

The present period is one of rapid development and major extension of the technology for high resolution and solid state NMR spectrometer magnets. Programs which have already been initiated have as their objective proton frequencies of 1 GHz and greater, eventually requiring HTS superconductors. These magnets will contain inner coils containing HTS conductors, surrounded by a set of relatively large coils fabricated with metallic superconductors. These coils represent a major extension of the adiabatically stable magnet technology that has evolved to address the performance issues posed by this type of magnet. The developments which are desirable for these large magnets are identified to include tough epoxy, interface to and thermal performance of external reinforcement, and high strength-high current density metallic superconductor. PMID:9413905

Markiewicz, W D

1997-11-01

147

Application of HR-MAS NMR spectroscopy for studying chemotype variations of Withania somnifera (L.) Dunal.  

PubMed

Withania somnifera (L.) Dunal (Solanaceae), commonly known as Ashwagandha, is one of the most valued Indian medicinal plants with a number of pharmaceutical and nutraceutical applications. Metabolic profiling has been performed by HR-MAS NMR spectroscopy on fresh leaf and root tissue specimens from four chemotypes of W. somnifera. The HR-MAS NMR spectroscopy of lyophilized defatted leaf tissue specimens clearly distinguishes resonances of medicinally important secondary metabolites (withaferin A and withanone) and its distinctive quantitative variability among the chemotypes. A total of 41 metabolites were identified from both the leaf and root tissues of the chemotypes. The presence of methanol in leaf and root tissues of W. somnifera was detected by HR-MAS NMR spectroscopy. Multivariate principal component analysis (PCA) on HR-MAS (1) H NMR spectra of leaves revealed clear variations in primary metabolites among the chemotypes. The results of the present study demonstrated an efficient method, which can be utilized for metabolite profiling of primary and secondary metabolites in medicinally important plants. PMID:21915899

Bharti, S K; Bhatia, Anil; Tewari, S K; Sidhu, O P; Roy, Raja

2011-10-01

148

High-resolution heteronuclear multi-dimensional NMR spectroscopy in magnetic fields with unknown spatial variations.  

PubMed

Heteronuclear NMR spectroscopy is an extremely powerful tool for determining the structures of organic molecules and is of particular significance in the structural analysis of proteins. In order to leverage the method's potential for structural investigations, obtaining high-resolution NMR spectra is essential and this is generally accomplished by using very homogeneous magnetic fields. However, there are several situations where magnetic field distortions and thus line broadening is unavoidable, for example, the samples under investigation may be inherently heterogeneous, and the magnet's homogeneity may be poor. This line broadening can hinder resonance assignment or even render it impossible. We put forth a new class of pulse sequences for obtaining high-resolution heteronuclear spectra in magnetic fields with unknown spatial variations based on distant dipolar field modulations. This strategy's capabilities are demonstrated with the acquisition of high-resolution 2D gHSQC and gHMBC spectra. These sequences' performances are evaluated on the basis of their sensitivities and acquisition efficiencies. Moreover, we show that by encoding and decoding NMR observables spatially, as is done in ultrafast NMR, an extra dimension containing J-coupling information can be obtained without increasing the time necessary to acquire a heteronuclear correlation spectrum. Since the new sequences relax magnetic field homogeneity constraints imposed upon high-resolution NMR, they may be applied in portable NMR sensors and studies of heterogeneous chemical and biological materials. PMID:24607822

Zhang, Zhiyong; Huang, Yuqing; Smith, Pieter E S; Wang, Kaiyu; Cai, Shuhui; Chen, Zhong

2014-05-01

149

High-resolution heteronuclear multi-dimensional NMR spectroscopy in magnetic fields with unknown spatial variations  

NASA Astrophysics Data System (ADS)

Heteronuclear NMR spectroscopy is an extremely powerful tool for determining the structures of organic molecules and is of particular significance in the structural analysis of proteins. In order to leverage the method’s potential for structural investigations, obtaining high-resolution NMR spectra is essential and this is generally accomplished by using very homogeneous magnetic fields. However, there are several situations where magnetic field distortions and thus line broadening is unavoidable, for example, the samples under investigation may be inherently heterogeneous, and the magnet’s homogeneity may be poor. This line broadening can hinder resonance assignment or even render it impossible. We put forth a new class of pulse sequences for obtaining high-resolution heteronuclear spectra in magnetic fields with unknown spatial variations based on distant dipolar field modulations. This strategy’s capabilities are demonstrated with the acquisition of high-resolution 2D gHSQC and gHMBC spectra. These sequences’ performances are evaluated on the basis of their sensitivities and acquisition efficiencies. Moreover, we show that by encoding and decoding NMR observables spatially, as is done in ultrafast NMR, an extra dimension containing J-coupling information can be obtained without increasing the time necessary to acquire a heteronuclear correlation spectrum. Since the new sequences relax magnetic field homogeneity constraints imposed upon high-resolution NMR, they may be applied in portable NMR sensors and studies of heterogeneous chemical and biological materials.

Zhang, Zhiyong; Huang, Yuqing; Smith, Pieter E. S.; Wang, Kaiyu; Cai, Shuhui; Chen, Zhong

2014-05-01

150

Observing selected domains in multi-domain proteins via sortase-mediated ligation and NMR spectroscopy  

PubMed Central

NMR spectroscopy has distinct advantages for providing insight into protein structures, but faces significant resolution challenges as protein size increases. To alleviate such resonance overlap issues, the ability to produce segmentally labeled proteins is beneficial. Here we show that the S. aureus transpeptidase sortase A can be used to catalyze the ligation of two separately expressed domains of the same protein, MecA (B. subtilis). The yield of purified, segmentally labeled MecA protein conjugate is ?40%. The resultant HSQC spectrum obtained from this domain-labeled conjugate demonstrates successful application of sortase A for segmental labeling of multi-domain proteins for solution NMR study.

Refaei, Mary Anne; Combs, Al; Kojetin, Douglas J.; Cavanagh, John; Caperelli, Carol; Rance, Mark; Sapitro, Jennifer

2011-01-01

151

Study by SERS spectroscopy of the adsorption of 1H-1,2,4-triazole-3-thione on silver sols  

NASA Astrophysics Data System (ADS)

Surface enhanced Raman scattering (SERS) spectra of 1H-1,2,4-triazole-3-thione (TAS) adsorbed on silver sols were recorded. From the comparison between the SERS and normal Raman spectra of TAS in aqueous and in NaOH solutions, it can be deduced that the substance adsorbs in the ionized thiolic form (TASA) on the silver surface. From the description of the vibrational normal modes related to the most enhanced bands in the SERS spectra, it can be deduced that the interaction with the silver sol occurs via the lone pairs of the sulphur and of one of the nitrogen atoms and that the orientation of the tetrazole ring is inclined with respect to the metal surface.

Pergolese, Barbara; Bigotto, Adriano

2003-06-01

152

Deuterium NMR spectroscopy of biosynthetically deuterated mammalian tissues  

SciTech Connect

The choline-containing phospholipids of mammalian membranes have been biosynthetically deuterated by raising rats on a diet supplemented with (HOCH2CH2N(CD3)3) Cl or (HOCD2CH2N(CH3)3) Cl . Deuterium NMR spectra have been obtained from excised deuterated brain, sciatic nerve, heart, and lung, from isolated brain myelin and brain microsomes, and from aqueous dispersions of lipid extracts. Measurements of residual quadrupole splittings for excised deuterated neural tissues demonstrate that the orientational order of the choline head group is similar to that observed in model membranes. The spin-lattice relaxation time of the choline head group in deuterated neural tissue is indistinguishable from that observed in model membranes. These results support the proposal that the conformation and motional dynamics of the choline head groups of the bulk choline-containing lipids of neural tissue are similar to those in model membranes. Spectra of biosynthetically deuterated brain myelin and brain microsomes exhibit similar quadrupole splittings. Since these membranes have significantly different protein contents, these results indicate that no strong polar interactions exist between membrane proteins and the choline head groups of choline-containing membrane lipids. Spectra of intact deuterated heart and lung exhibit broad lines and a range of quadrupole splittings.

Curatolo, W.; Jungalwala, F.B.; Sears, B.; Tuck, L.; Neuringer, L.J.

1985-07-30

153

Monitoring bound HA1(H1N1) and HA1(H5N1) on freely suspended graphene over plasmonic platforms with infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Infrared (IR) spectroscopy provides fingerprinting of the energy and orientation of molecular bonds. The IR signals are generally weak and require amplification. Here we present a new plasmonic platform, made of freely suspended graphene, which was coating periodic metal structures. Only monolayer thick films were needed for a fast signal recording. We demonstrated unique IR absorption signals of bound proteins: these were the hemagglutinin area (HA1) of swine influenza (H1N1) and the avian influenza (H5N1) viruses bound to their respective tri-saccharides ligand receptors. The simplicity and sensitivity of such approach may find applications in fast monitoring of binding events.

Banerjee, Amrita; Chakraborty, Sumit; Altan-Bonnet, Nihal; Grebel, Haim

2013-09-01

154

NMR spectroscopy of native and in vitro tissues implicates polyADP ribose in biomineralization.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy is useful to determine molecular structure in tissues grown in vitro only if their fidelity, relative to native tissue, can be established. Here, we use multidimensional NMR spectra of animal and in vitro model tissues as fingerprints of their respective molecular structures, allowing us to compare the intact tissues at atomic length scales. To obtain spectra from animal tissues, we developed a heavy mouse enriched by about 20% in the NMR-active isotopes carbon-13 and nitrogen-15. The resulting spectra allowed us to refine an in vitro model of developing bone and to probe its detailed structure. The identification of an unexpected molecule, poly(adenosine diphosphate ribose), that may be implicated in calcification of the bone matrix, illustrates the analytical power of this approach. PMID:24833391

Chow, W Ying; Rajan, Rakesh; Muller, Karin H; Reid, David G; Skepper, Jeremy N; Wong, Wai Ching; Brooks, Roger A; Green, Maggie; Bihan, Dominique; Farndale, Richard W; Slatter, David A; Shanahan, Catherine M; Duer, Melinda J

2014-05-16

155

Bis(pentamethylcyclopentadienyl)ytterbium: An investigation of weak interactions in solution using multinuclear NMR spectroscopy  

SciTech Connect

NMR spectroscopy is ideal for studying weak interactions (formation enthalpy {le}20 kcal/mol) in solution. The metallocene bis(pentamethylcyclopentadienyl)ytterbium, Cp*{sub 2}Yb, is ideal for this purpose. cis-P{sub 2}PtH{sub 2}complexes (P = phosphine) were used to produce slow-exchange Cp*{sub 2}YbL adducts for NMR study. Reversible formation of (P{sub 2}PtH){sub 2} complexes from cis-P{sub 2}PtH{sub 2} complexes were also studied, followed by interactions of Cp*{sub 2}Yb with phosphines, R{sub 3}PX complexes. A NMR study was done on the interactions of Cp*{sub 2}Yb with H{sub 2}, CH{sub 4}, Xe, CO, silanes, stannanes, C{sub 6}H{sub 6}, and toluene.

Schwartz, D.J.

1995-07-01

156

Dynamic nuclear polarisation enhanced (14)N overtone MAS NMR spectroscopy.  

PubMed

Dynamic nuclear polarisation (DNP) has been used to obtain magic angle spinning (14)N(OT) (nitrogen-14 overtone) solid-state NMR spectra from several model amino acids, with both direct and indirect observation of the (14)N(OT) signal. The crystalline solids were impregnated with biradical solutions of organic liquids that do not dissolve the crystalline phase. The bulk phase was then polarized via(1)H spin diffusion from the highly-polarized surface (1)H nuclei, resulting in (1)H DNP signal enhancements of around two orders of magnitude. Cross polarisation from (1)H nuclei directly to the (14)N overtone transition is demonstrated under magic angle spinning, using a standard pulse sequence with a relatively short contact time (on the order of 100 ?s). This method can be used to acquire (14)N overtone MAS powder patterns that match closely with simulated line shapes, allowing isotropic chemical shifts and quadrupolar parameters to be measured. DNP enhancement also allows the rapid acquisition of 2D (14)N(OT) heteronuclear correlation spectra from natural abundance powder samples. (1)H-(14)N(OT) HETCOR and (13)C-(14)N(OT) HMQC pulse sequences were used to observe all single-bond H-N and C-N correlations in histidine hydrochloride monohydrate, with the spectra obtained in a matter of hours. Due to the high natural abundance of the (14)N isotope (99.6%) and the advantages of observing the overtone transition, these methods provide an attractive route to the observation of C-N correlations from samples at natural isotopic abundance and enable the high resolution measurement of (14)N chemical shifts and quadrupolar interaction parameters. PMID:24847776

Rossini, Aaron J; Emsley, Lyndon; O'Dell, Luke A

2014-06-01

157

In situ solid-state NMR spectroscopy of electrochemical cells: batteries, supercapacitors, and fuel cells.  

PubMed

Electrochemical cells, in the form of batteries (or supercapacitors) and fuel cells, are efficient devices for energy storage and conversion. These devices show considerable promise for use in portable and static devices to power electronics and various modes of transport and to produce and store electricity both locally and on the grid. For example, high power and energy density lithium-ion batteries are being developed for use in hybrid electric vehicles where they improve the efficiency of fuel use and help to reduce greenhouse gas emissions. To gain insight into the chemical reactions involving the multiple components (electrodes, electrolytes, interfaces) in the electrochemical cells and to determine how cells operate and how they fail, researchers ideally should employ techniques that allow real-time characterization of the behavior of the cells under operating conditions. This Account reviews the recent use of in situ solid-state NMR spectroscopy, a technique that probes local structure and dynamics, to study these devices. In situ NMR studies of lithium-ion batteries are performed on the entire battery, by using a coin cell design, a flat sealed plastic bag, or a cylindrical cell. The battery is placed inside the NMR coil, leads are connected to a potentiostat, and the NMR spectra are recorded as a function of state of charge. (7)Li is used for many of these experiments because of its high sensitivity, straightforward spectral interpretation, and relevance to these devices. For example, (7)Li spectroscopy was used to detect intermediates formed during electrochemical cycling such as LixC and LiySiz species in batteries with carbon and silicon anodes, respectively. It was also used to observe and quantify the formation and growth of metallic lithium microstructures, which can cause short circuits and battery failure. This approach can be utilized to identify conditions that promote dendrite formation and whether different electrolytes and additives can help prevent dendrite formation. The in situ method was also applied to monitor (by (11)B NMR) electrochemical double-layer formation in supercapacitors in real time. Though this method is useful, it comes with challenges. The separation of the contributions from the different cell components in the NMR spectra is not trivial because of overlapping resonances. In addition, orientation-dependent NMR interactions, including the spatial- and orientation-dependent bulk magnetic susceptibility (BMS) effects, can lead to resonance broadening. Efforts to understand and mitigate these BMS effects are discussed in this Account. The in situ NMR investigation of fuel cells initially focused on the surface electrochemistry at the electrodes and the electrochemical oxidation of methanol and CO to CO2 on the Pt cathode. On the basis of the (13)C and (195)Pt NMR spectra of the adsorbates and electrodes, CO adsorbed on Pt and other reaction intermediates and complete oxidation products were detected and their mode of binding to the electrodes investigated. Appropriate design and engineering of the NMR hardware has allowed researchers to integrate intact direct methanol fuel cells into NMR probes. Chemical transformations of the circulating methanol could be followed and reaction intermediates could be detected in real time by either (2)H or (13)C NMR spectroscopy. By use of the in situ NMR approach, factors that control fuel cell performance, such as methanol cross over and catalyst performance, were identified. PMID:24041242

Blanc, Frédéric; Leskes, Michal; Grey, Clare P

2013-09-17

158

Determination of 15N chemical shift anisotropy from a membrane bound protein by NMR spectroscopy  

PubMed Central

Chemical shift anisotropy (CSA) tensors are essential in the structural and dynamic studies of proteins using NMR spectroscopy. Results from relaxation studies in biomolecular solution and solid-state NMR experiments on aligned samples are routinely interpreted using well-characterized CSA tensors determined from model compounds. Since CSA tensors, particularly the 15N CSA, highly depend on a number of parameters including secondary structure, electrostatic interaction and the amino acid sequence, there is a need for accurately determined CSA tensors from proteins. In this study we report the backbone amide-15N CSA tensors for a 16.7-kDa membrane-bound and paramagnetic-heme containing protein, rabbit cytochrome b5 (cytb5), determined using the 15N CSA/15N-1H dipolar transverse cross-correlation rates. The mean values of 15N CSA determined for residues in helical, sheet and turn regions are ?187.9, ?166.0, and ?161.1 ppm, respectively, with an overall average value of ?171.7 ppm. While the average CSA value determined from this study is in good agreement with previous solution NMR experiments on small globular proteins, the CSA value determined for residues in helical conformation is slightly larger which may be attributed to the paramagnetic effect from Fe(III) of the heme unit in cytb5. However, like in previous solution NMR studies, the CSA values reported in this study are larger than the values measured from solid-state NMR experiments. We believe that the CSA parameters reported in this study will be useful in determining the structure, dynamics and orientation of proteins, including membrane proteins, using NMR spectroscopy.

Pandey, Manoj Kumar; Vivekanandan, Subramanian; Ahuja, Shivani; Pichumani, Kumar; Im, Sang-Choul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

2012-01-01

159

Exploiting periodic first-principles calculations in NMR spectroscopy of disordered solids.  

PubMed

Much of the information contained within solid-state nuclear magnetic resonance (NMR) spectra remains unexploited because of the challenges in obtaining high-resolution spectra and the difficulty in assigning those spectra. Recent advances that enable researchers to accurately and efficiently determine NMR parameters in periodic systems have revolutionized the application of density functional theory (DFT) calculations in solid-state NMR spectroscopy. These advances are particularly useful for experimentalists. The use of first-principles calculations aids in both the interpretation and assignment of the complex spectral line shapes observed for solids. Furthermore, calculations provide a method for evaluating potential structural models against experimental data for materials with poorly characterized structures. Determining the structure of well-ordered, periodic crystalline solids can be straightforward using methods that exploit Bragg diffraction. However, the deviations from periodicity, such as compositional, positional, or temporal disorder, often produce the physical properties (such as ferroelectricity or ionic conductivity) that may be of commercial interest. With its sensitivity to the atomic-scale environment, NMR provides a potentially useful tool for studying disordered materials, and the combination of experiment with first-principles calculations offers a particularly attractive approach. In this Account, we discuss some of the issues associated with the practical implementation of first-principles calculations of NMR parameters in solids. We then use two key examples to illustrate the structural insights that researchers can obtain when applying such calculations to disordered inorganic materials. First, we describe an investigation of cation disorder in Y2Ti(2-x)Sn(x)O7 pyrochlore ceramics using (89)Y and (119)Sn NMR. Researchers have proposed that these materials could serve as host phases for the encapsulation of lanthanide- and actinide-bearing radioactive waste. In a second example, we discuss how (17)O NMR can be used to probe the dynamic disorder of H in hydroxyl-humite minerals (nMg2SiO4ˇMg(OH)2), and how (19)F NMR can be used to understand F substitution in these systems. The combination of first-principles calculations and multinuclear NMR spectroscopy facilitates the investigation of local structure, disorder, and dynamics in solids. We expect that applications will undoubtedly become more widespread with further advances in computational and experimental methods. Insight into the atomic-scale environment is a crucial first step in understanding the structure-property relationships in solids, and it enables the efficient design of future materials for a range of end uses. PMID:23402741

Ashbrook, Sharon E; Dawson, Daniel M

2013-09-17

160

Application of two-dimensional NMR spectroscopy to metabotyping laboratory Escherichia coli strains.  

PubMed

NMR Spectroscopy has been established as a major tool for identification and quantification of metabolites in a living system. Since the metabolomics era began, one-dimensional NMR spectroscopy has been intensively employed due to its simplicity and quickness. However, it has suffered from an inevitable overlap of signals, thus leading to inaccuracy in identification and quantification of metabolites. Two-dimensional (2D) NMR has emerged as a viable alternative because it can offer higher accuracy in a reasonable amount of time. We employed (1) H,(13) C-HSQC to profile metabolites of six different laboratory E. coli strains. We identified 18 metabolites and observed clustering of six strains according to their metabolites. We compared the metabolites among the strains, and found that a) the strains specialized for protein production were segregated; b) XL1-Blue separated itself from others by accumulating amino acids such as alanine, aspartate, glutamate, methionine, proline, and lysine; c) the strains specialized for cloning purpose were spread out from one another; and d) the strains originating from B strain were characterized by succinate accumulation. This work shows that 2D-NMR can be applied to identify a strain from metabolite analysis, offering a possible alternative to genetic analysis to identify E. coli strains. PMID:24130025

Chae, Young Kee; Kim, Seol Hyun; Nam, Youn-Ki

2013-10-01

161

Recent developments in solid-state NMR spectroscopy of crystalline microporous materials.  

PubMed

Microporous materials, having pores and channels on the same size scale as small to medium molecules, have found many important applications in current technologies, including catalysis, gas separation and drug storage and delivery. Many of their properties and functions are related to their detailed local structure, such as the type and distribution of active sites within the pores, and the specific structures of these active sites. Solid-state NMR spectroscopy has a strong track record of providing the requisite detailed atomic-level insight into the structures of microporous materials, in addition to being able to probe dynamic processes occurring on timescales spanning many orders of magnitude (i.e., from s to ps). In this Perspective, we provide a brief review of some of the basic experimental approaches used in solid-state NMR spectroscopy of microporous materials, and then discuss some more recent advances in this field, particularly those applied to the study of crystalline materials such as zeolites and metal-organic frameworks. These advances include improved software for aiding spectral interpretation, the development of the NMR-crystallography approach to structure determination, new routes for the synthesis of isotopically-labelled materials, methods for the characterisation of host-guest interactions, and methodologies suitable for observing NMR spectra of paramagnetic microporous materials. Finally, we discuss possible future directions, which we believe will have the greatest impact on the field over the coming years. PMID:24675798

Ashbrook, Sharon E; Dawson, Daniel M; Seymour, Valerie R

2014-04-01

162

Exchange rate constants of invisible protons in proteins determined by NMR spectroscopy.  

PubMed

Although labile protons that are exchanging rapidly with those of the solvent cannot be observed directly, their exchange rate constants can be determined by indirect detection of scalar-coupled neighboring nuclei. We have used heteronuclear NMR spectroscopy to measure the exchange rate constants of labile protons in the side chains of lysine and arginine residues in ubiquitin enriched in carbon-13 and nitrogen-15 at neutral pH. Exchange rate constants as fast as 40x10(3) s(-1) were thus measured. These results demonstrate that NMR spectroscopy is a powerful tool for the characterization of lysine NH3(+) and arginine NH groups in proteins at physiologically relevant pH values. PMID:18247446

Segawa, Takuya; Kateb, Fatiha; Duma, Luminita; Bodenhausen, Geoffrey; Pelupessy, Philippe

2008-03-01

163

STRUCTURAL STUDIES OF BIOMATERIALS USING DOUBLE-QUANTUM SOLID-STATE NMR SPECTROSCOPY  

SciTech Connect

Proteins directly control the nucleation and growth of biominerals, but the details of molecular recognition at the protein-biomineral interface remain poorly understood. The elucidation of recognition mechanisms at this interface may provide design principles for advanced materials development in medical and ceramic composites technologies. Here, we describe both the theory and practice of double-quantum solid-stateNMR(ssNMR) structure-determination techniques, as they are used to determine the secondary structures of surface-adsorbed peptides and proteins. In particular, we have used ssNMR dipolar techniques to provide the first high-resolution structural and dynamic characterization of a hydrated biomineralization protein, salivary statherin, adsorbed to its biologically relevant hydroxyapatite (HAP) surface. Here, we also review NMR data on peptides designed to adsorb from aqueous solutions onto highly porous hydrophobic surfaces with specific helical secondary structures. The adsorption or covalent attachment of biological macromolecules onto polymer materials to improve their biocompatibility has been pursued using a variety of approaches, but key to understanding their efficacy is the verification of the structure and dynamics of the immobilized biomolecules using double-quantum ssNMR spectroscopy.

Drobny, Gary P.; Long, J. R.; Karlsson, T.; Shaw, Wendy J.; Popham, Jennifer M.; Oyler, N.; Bower, Paula M.; Stringer, J.; Gregory, D.; Mehta, M.; Stayton, Patrick S.

2004-10-31

164

Structural Studies of Biomaterials Using Double-Quantum Solid-State NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

Proteins directly control the nucleation and growth of biominerals, but the details of molecular recognition at the protein-biomineral interface remain poorly understood. The elucidation of recognition mechanisms at this interface may provide design principles for advanced materials development in medical and ceramic composites technologies. Here, we describe both the theory and practice of double-quantum solid-state NMR (ssNMR) structure-determination techniques, as they are used to determine the secondary structures of surface-adsorbed peptides and proteins. In particular, we have used ssNMR dipolar techniques to provide the first high-resolution structural and dynamic characterization of a hydrated biomineralization protein, salivary statherin, adsorbed to its biologically relevant hydroxyapatite (HAP) surface. Here, we also review NMR data on peptides designed to adsorb from aqueous solutions onto highly porous hydrophobic surfaces with specific helical secondary structures. The adsorption or covalent attachment of biological macromolecules onto polymer materials to improve their biocompatibility has been pursued using a variety of approaches, but key to understanding their efficacy is the verification of the structure and dynamics of the immobilized biomolecules using double-quantum ssNMR spectroscopy.

Drobny, G. P.; Long, J. R.; Karlsson, T.; Shaw, W.; Popham, J.; Oyler, N.; Bower, P.; Stringer, J.; Gregory, D.; Mehta, M.; Stayton, P. S.

2003-10-01

165

An inducible helix-Gly-Gly-helix motif in the N-terminal domain of histone H1e: A CD and NMR study  

Microsoft Academic Search

Knowledge of the structural properties of linker histones is important to the understanding of their role in higher-order chromatin structure and gene regulation. Here we study the conformational properties of the peptide Ac-EKTPVKKKARKAAGGAKRKTSG-NH2 (NE-1) by circular dichroism and 1 H-NMR. This peptide corresponds to the positively charged region of the N-terminal domain, adjacent to the globular domain, of mouse histone

ROGER VILA; IMMA PONTE; M. ANGELES JIMÉNEZ; MANUEL RICO; PEDRO SUAU

2008-01-01

166

Molecular dynamics of ethylene glycol adsorbed in NaX: NMR and broadband dielectric spectroscopy studies  

Microsoft Academic Search

Proton spin relaxation and broadband dielectric spectroscopy are applied to study the dynamics of ethylene glycol adsorbed in NaX, EG\\/NaX. The molecular mobility strongly depends on the pore filling factor which may be controlled by high-resolution 1H MAS NMR measurements. Although EG in bulk shows a Vogel–Fulcher–Tammann type of activation, temperature dependent relaxation rate measurements for the EG\\/NaX systems always

Özlen F. Erdem; Dieter Michel

2006-01-01

167

Investigation of interaction parameters in mixed micelle using pulsed field gradient NMR spectroscopy  

Microsoft Academic Search

Pulsed field gradient NMR spectroscopy was used to determine the partitioning of surfactant between monomeric and micellar forms in a mixed CTAB (hexadecyltetramethylammonium bromide) and Triton X-100 [p-(1,1,3-tetramethylbutyl)polyoxyethylene] system. In addition, potentiometric and surface tension measurements were used to determine the free concentration of ionic surfactant and the critical micelle concentration (CMC) of mixtures of n-alkyltrimethylammonium bromide (CnTAB, n=12, 14,

H. Gharibi; S. Javadian; B. Sohrabi; R. Behjatmanesh

2005-01-01

168

Elucidation of cross relaxation in liquids by two-dimensional N.M.R. spectroscopy  

Microsoft Academic Search

Two-dimensional N.M.R. spectroscopy is applied to the elucidation of cross relaxation pathways in liquids. The theory underlying two dimensional studies of cross relaxation and of transient nuclear Overhauser effects is developed. The influence of the correlation time of the molecular random process is investigated. It is found that in the limit of short correlation times (extreme narrowing limit) weak negative

S. Macura; R. R. Ernst

1980-01-01

169

Intramyocellular lipid concentrations are correlated with insulin sensitivity in humans: a 1H NMR spectroscopy study  

Microsoft Academic Search

Summary   Recent muscle biopsy studies have shown a relation between intramuscular lipid content and insulin resistance. The aim of\\u000a this study was to test this relation in humans by using a novel proton nuclear magnetic resonance (1H NMR) spectroscopy technique, which enables non-invasive and rapid ( ? 45 min) determination of intramyocellular lipid (IMCL)\\u000a content. Normal weight non-diabetic adults (n

M. Krssak; K. Falk Petersen; A. Dresner; L. DiPietro; S. M. Vogel; D. L. Rothman; G. I. Shulman; M. Roden

1999-01-01

170

Stereochemical investigations on the diketopiperazine derivatives of enalapril and lisinopril by NMR spectroscopy  

Microsoft Academic Search

Stereochemical analysis of epimeric diketopiperazine (DKP) derivatives of enalapril and lisinopril has been performed by NMR spectroscopy. The present study focuses on the configurational assignment and conformational characteristics of the epimeric DKPs obtained from cyclization and subsequent base-catalyzed hydrolysis. We report full 1H and 13C assignments as obtained by a concerted use of 1D and 2D methods. The configuration of

Ádám Demeter; Tamás Fodor; János Fischer

1998-01-01

171

Identification of biochemical changes in lactovegetarian urine using 1 H NMR spectroscopy and pattern recognition  

Microsoft Academic Search

A vegetarian diet has been demonstrated to have a profound influence on human metabolism as well as to aid the prevention\\u000a of several chronic diseases relative to an omnivorous diet. However, there have been no systematic metabolomic studies on\\u000a all of the biochemical changes induced in human subjects by long-term vegetarianism. In this study, 1H NMR spectroscopy in combination with

Jingjing Xu; Shuyu Yang; Shuhui Cai; Jiyang Dong; Xuejun Li; Zhong Chen

2010-01-01

172

Optimization of NMR spectroscopy of encapsulated proteins dissolved in low viscosity fluids  

Microsoft Academic Search

Comprehensive application of solution NMR spectroscopy to studies of macromolecules remains fundamentally limited by the molecular\\u000a rotational correlation time. For proteins, molecules larger than 30 kDa require complex experimental methods, such as TROSY\\u000a in conjunction with isotopic labeling schemes that are often expensive and generally reduce the potential information available.\\u000a We have developed the reverse micelle encapsulation strategy as an alternative

Nathaniel V. Nucci; Bryan S. Marques; Sabrina Bédard; Jakob Dogan; John M. Gledhill; Veronica R. Moorman; Ronald W. Peterson; Kathleen G. Valentine; Alison L. Wand; A. Joshua Wand

2011-01-01

173

High Q factor RF planar microcoils for micro-scale NMR spectroscopy  

Microsoft Academic Search

We present the design, fabrication and test of high-Q factor radiofrequency planar microcoils for nuclear magnetic resonance (NMR) spectroscopy in small volume samples. The coils are fabricated on glass wafers using high-aspect ratio SU-8 photoepoxy and copper electroplating. On-wafer electrical characterization shows quality factors up to 40 at 800MHz. A 500?m diameter microcoil with a measured quality factor of 24

C. Massin; G. Boero; F. Vincent; J. Abenhaim; P.-A. Besse; R. S. Popovic

2002-01-01

174

Semiquantitative analysis of thiophenic compounds in light cycle oil (LCO) using 13C NMR spectroscopy  

Microsoft Academic Search

S-methyltetrafluoroborate salts of the thiophenic compounds (CH3-S+:BF4?) present in LCO petroleum fractions were obtained and analyzed by 1H and 13C NMR spectroscopy. The methylation of the samples was carried out using 99.5% 13C enriched methyl iodine, to improve the sensitivity of the technique. The amount of the methylated derivatives was determined by the internal standard method; using dioxane as a

J. C Poveda Jaramillo; D. R Molina Velazco; C Baldrich

2004-01-01

175

In-Vivo NMR Spectroscopy of the Brain at High Fields  

Microsoft Academic Search

Increased magnetic fields in principle provide increased sensitivity and specificity. In vivo, however, the increase in magnetic\\u000a field alone does not automatically result in obvious improvements. Among the factors that are set to impede the improvements\\u000a in sensitivity for in-vivo NMR spectroscopy are the increased challenges in eliminating the macroscopic inhomogeneities caused\\u000a by mainly the air- tissue interface and increased

Rolf Gruetter; Pierre-Gilles Henry; Hongxia Lei; Silvia Mangia; Gülin Öz; Melissa Terpstra; Ivan Tkac

176

Nanotechnology for biomaterials engineering: structural characterization of amphiphilic polymeric nanoparticles by 1H NMR spectroscopy  

Microsoft Academic Search

Nanoparticles composed of diblock poly(d,l-lactide-co-glycolide)-poly(ethylene glycol) (PLGA-PEG) or a branched, multiblock PLA-(PEG)3 were prepared by the single emulsion technique. Results of previous studies of these nanoparticles suggested that their structure is of the core-corona type with a polyester core and an outer PEG coating. In the present study, 1H NMR spectroscopy was utilized to provide direct evidence of the structure

Jeffrey S. Hrkach; Maria Teresa Peracchia; Avi Bomb; noah Lotan; Robert Langer

1997-01-01

177

Quantitative determination of glyphosate in human serum by 1H NMR spectroscopy  

Microsoft Academic Search

The determination and quantification of glyphosate in serum using 1H NMR spectroscopy is reported. This method permitted serum samples to be analysed without derivatization or any other sample pre-treatment, using 3-trimethylsilyl 2,2?,3,3?-tetradeuteropropionic acid (TSP-d4) as a qualitative and quantitative standard. Characterization of the herbicide N-(phosphonomethyl)glycine was performed by analysing chemical shifts and coupling constant patterns. Quantification was performed by relative

Bernard Cartigny; Nathalie Azaroual; Michel Imbenotte; Daniel Mathieu; Erika Parmentier; Gaston Vermeersch; Michel Lhermitte

2008-01-01

178

Analysis of Hydroperoxides in solid Polyethylene by NMR and EPR Spectroscopy  

SciTech Connect

The authors have shown that the hydroperoxide species in {gamma}-irradiated {sup 13}C-polyethylene can be directly observed by {sup 13}C MAS NMR spectroscopy. The experiment was performed without the need for special sample preparation such as chemical derivatization or dissolution. Annealing experiments were employed to study the thermal decomposition of the hydroperoxide species and to measure an activation energy of 98 kJ/mol. EPR spectroscopy suggests that residual polyenyl and alkylperoxy radicals are predominantly trapped in interracial or crystalline regions, while the peroxy radicals observed after UV-photolysis of hydroperoxides are in amorphous regions.

ASSINK,ROGER A.; CELINA,MATHIAS C.; DUNBAR,TIMOTHY D.; ALAM,TODD M.; CLOUGH,ROGER LEE; GILLEN,KENNETH T.

2000-06-12

179

Determination of group composition of tar fractions from pyrolysis of worn-out tires by 1 H NMR spectroscopy  

Microsoft Academic Search

The advantage of IH NMR spectroscopy is the fact that the spectra of the products to be analyzed can be interpreted without first separating them. This makes it considerably simpler and faster to obtain information on the composition of the hydrocarbons under investigation. Both earlier [4, 5] and current [6, 7] integral structure analysis methods consider the entire NMR spectrum

S. S. Belyaeva; Yu. E. Shapiro; V. G. Lebedevskaya; A. B. Kufirin; N. A. Danilov

1991-01-01

180

Orientation of Amphipathic Helical Peptides in Membrane Bilayers Determined by Solid-State NMR Spectroscopy. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Solid-state NMR spectroscopy was used to determine the orientations of two amphipathic helical peptides associated with lipid bilayers. A single spectral parameter provides sufficient orientational information for these peptides, which are known, from oth...

B. Bechinger Y. Kim L. E. Chirlian J. Gesell J. M. Neumann

1991-01-01

181

Methodology of H NMR Spectroscopy of the Human Brain at Very High Magnetic Fields.  

PubMed

An ultrashort-echo-time stimulated echo-acquisition mode (STEAM) pulse sequence with interleaved outer volume suppression and VAPOR (variable power and optimized relaxation delays) water suppression was redesigned and optimized for human applications at 4 and 7 T, taking into account the specific requirements for spectroscopy at high magnetic fields and limitations of currently available hardware. In combination with automatic shimming, automated parameter adjustments and data processing, this method provided a user-friendly tool for routine (1)H nuclear magnetic resonance (NMR) spectroscopy of the human brain at very high magnetic fields. Effects of first- and second-order shimming, single-scan averaging, frequency and phase corrections, and eddy currents were described. LCModel analysis of an in vivo (1)H NMR spectrum measured from the human brain at 7 T allowed reliable quantification of more than fifteen metabolites noninvasively, illustrating the potential of high-field NMR spectroscopy. Examples of spectroscopic studies performed at 4 and 7 T demonstrated the high reproducibility of acquired spectra quality. PMID:20179773

Tká?, I; Gruetter, R

2005-03-01

182

High resolution magic angle spinning (HR-MAS) NMR spectroscopy of human osteoarthritic cartilage  

PubMed Central

Osteoarthritis (OA) is a degenerative disease of the joint and results in changes in the biochemical composition of cartilage. Studies have been undertaken in the past that have used high resolution NMR spectroscopy to study the biochemical composition of porcine, canine and bovine cartilage. In this study high resolution magical angle spinning (HRMAS) NMR spectroscopy at 11.7 T has been used to characterize metabolites and detect differences in the spectral signature of human knee articular cartilage from non-OA healthy cadaver knees and samples acquired from severe OA patients at the time of total knee replacement surgery. A statistically significant difference in the alanine (1.47 ppm), N-acetyl (2.04 ppm), choline (3.25 ppm) and glycine (3.55 ppm) metabolite levels is observed between healthy and OA specimens. The results of the study indicate that a decrease in the intensity of N-acetyl resonance occurs in later stages of OA. A positive correlation of the N-acetyl levels as measured by 1H HR-MAS NMR spectroscopy with the total proteoglycan content in the same cartilage specimens as measured by the GAG assay was observed. This indicates that N-acetyl can serve as an important bio-marker of OA disease progression. A decrease in the alanine concentration in OA may be attributed to the degradation of the collagen framework with disease progression and eventual loss of the degradation products that are transported from cartilage into the synovial cavity.

Shet, Keerthi; Siddiqui, Sarmad M.; Yoshihara, Hikari; Kurhanewicz, John; Ries, Michael; Li, Xiaojuan

2011-01-01

183

PASADENA hyperpolarization of succinic acid for MRI and NMR spectroscopy.  

PubMed

We use the PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) method to achieve 13C polarization of approximately 20% in seconds in 1-13C-succinic-d2 acid. The high-field 13C multiplets are observed as a function of pH, and the line broadening of C1 is pronounced in the region of the pK values. The 2JCH, 3JCH, and 3JHH couplings needed for spin order transfer vary with pH and are best resolved at low pH leading to our use of pH approximately 3 for both the molecular addition of parahydrogen to 1-13C-fumaric acid-d2 and the subsequent transfer of spin order from the nascent protons to C1 of the succinic acid product. The methods described here may generalize to hyperpolarization of other carboxylic acids. The C1 spin-lattice relaxation time at neutral pH and 4.7 T is measured as 27 s in H2O and 56 s in D2O. Together with known rates of succinate uptake in kidneys, this allows an estimate of the prospects for the molecular spectroscopy of metabolism. PMID:18335934

Chekmenev, Eduard Y; Hövener, Jan; Norton, Valerie A; Harris, Kent; Batchelder, Lynne S; Bhattacharya, Pratip; Ross, Brian D; Weitekamp, Daniel P

2008-04-01

184

Sensitivity of 2H NMR spectroscopy to motional models: proteins and highly viscous liquids as examples.  

PubMed

In order to study to what extent mechanisms of molecular motion can be unambiguously revealed by (2)H NMR spectroscopy, (2)H spectra for proteins (chicken villin protein headpiece HP36, selectively methyl-deuterated at leucine-69, C(?) D(3)) and binary systems of high viscosity (benzene-d(6) in tricresyl phosphate) have been carefully analyzed as illustrative examples (the spectra are taken from the literature). In the first case, a model of restricted diffusion mediated by jumps between rotameric orientations has been tested against jump- and free diffusion models which describe rotational motion combined with jump dynamics. It has been found that the set of (2)H spectra of methyl-deuterated at leucine-69 chicken villin protein headpiece HP36 can be consistently explained by different motional models as well as by a gaussian distribution of correlation times assuming isotropic rotation (simple brownian diffusion model). The last finding shows that when the possible distribution of correlation times is not very broad one might not be able to distinguish between heterogeneous and homogenous (but more complex) dynamics by analyzing (2)H lineshapes. For benzene-d(6) in tricresyl phosphate, the dynamics is heterogeneous and it has been demonstrated that a gaussian distribution of correlation times reproduces well the experimental lineshapes, while for a Cole-Davidson distribution the agreement is somewhat worse. For inquires into the sensitivity of quadrupolar NMR spectral analysis (by "quadrupolar NMR spectroscopy we understand NMR spectroscopy of nuclei possessing quadrupole moment), the recently presented theoretical approach [Kruk et al., J. Chem. Phys. 135, 224511 (2011)] has been used as it allows simulating quadrupolar spectra for arbitrary motional conditions by employing the stochastic Liouville equation. PMID:22755589

Kruk, D; Mielczarek, A; Korpala, A; Kozlowski, A; Earle, K A; Moscicki, J

2012-06-28

185

Lithium ion diffusion in Li ?-alumina single crystals measured by pulsed field gradient NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The lithium ion diffusion coefficient of a 93% Li ?-alumina single crystal was measured for the first time using pulsed field gradient (PFG) NMR spectroscopy with two different crystal orientations. The diffusion coefficient was found to be 1.2 × 10-11 m2/s in the direction perpendicular to the c axis at room temperature. The Li ion diffusion coefficient along the c axis direction was found to be very small (6.4 × 10-13 m2/s at 333 K), which suggests that the macroscopic diffusion of the Li ion in the ?-alumina crystal is mainly two-dimensional. The diffusion coefficient for the same sample was also estimated using NMR line narrowing data and impedance measurements. The impedance data show reasonable agreement with PFG-NMR data, while the line narrowing measurements provided a lower value for the diffusion coefficient. Line narrowing measurements also provided a relatively low value for the activation energy and pre-exponential factor. The temperature dependent diffusion coefficient was obtained in the temperature range 297-333 K by PFG-NMR, from which the activation energy for diffusion of the Li ion was estimated. The activation energy obtained by PFG-NMR was smaller than that obtained by impedance measurements, which suggests that thermally activated defect formation energy exists for 93% Li ?-alumina single crystals. The diffusion time dependence of the diffusion coefficient was observed for the Li ion in the 93% Li ?-alumina single crystal by means of PFG-NMR experiments. Motion of Li ion in fractal dimension might be a possible explanation for the observed diffusion time dependence of the diffusion coefficient in the 93% Li ?-alumina system.

Chowdhury, Mohammed Tareque; Takekawa, Reiji; Iwai, Yoshiki; Kuwata, Naoaki; Kawamura, Junichi

2014-03-01

186

Lithium ion diffusion in Li ?-alumina single crystals measured by pulsed field gradient NMR spectroscopy.  

PubMed

The lithium ion diffusion coefficient of a 93% Li ?-alumina single crystal was measured for the first time using pulsed field gradient (PFG) NMR spectroscopy with two different crystal orientations. The diffusion coefficient was found to be 1.2 × 10(-11) m(2)/s in the direction perpendicular to the c axis at room temperature. The Li ion diffusion coefficient along the c axis direction was found to be very small (6.4 × 10(-13) m(2)/s at 333 K), which suggests that the macroscopic diffusion of the Li ion in the ?-alumina crystal is mainly two-dimensional. The diffusion coefficient for the same sample was also estimated using NMR line narrowing data and impedance measurements. The impedance data show reasonable agreement with PFG-NMR data, while the line narrowing measurements provided a lower value for the diffusion coefficient. Line narrowing measurements also provided a relatively low value for the activation energy and pre-exponential factor. The temperature dependent diffusion coefficient was obtained in the temperature range 297-333 K by PFG-NMR, from which the activation energy for diffusion of the Li ion was estimated. The activation energy obtained by PFG-NMR was smaller than that obtained by impedance measurements, which suggests that thermally activated defect formation energy exists for 93% Li ?-alumina single crystals. The diffusion time dependence of the diffusion coefficient was observed for the Li ion in the 93% Li ?-alumina single crystal by means of PFG-NMR experiments. Motion of Li ion in fractal dimension might be a possible explanation for the observed diffusion time dependence of the diffusion coefficient in the 93% Li ?-alumina system. PMID:24697461

Chowdhury, Mohammed Tareque; Takekawa, Reiji; Iwai, Yoshiki; Kuwata, Naoaki; Kawamura, Junichi

2014-03-28

187

State-of-the-Art Direct 13C and Indirect 1H-[13C] NMR Spectroscopy In Vivo  

PubMed Central

Carbon-13 NMR spectroscopy in combination with 13C-labeled substrate infusion is a powerful technique to measure a large number of metabolic fluxes non-invasively in vivo. It has been used to quantify glycogen synthesis rates, establish quantitative relationships between energy metabolism and neurotransmission and evaluate the importance of different substrates. All measurements can, in principle, be performed through direct 13C NMR detection or via indirect 1H-[13C] NMR detection of the protons attached to 13C nuclei. The choice for detection scheme and pulse sequence depends on the magnetic field strength, whereas substrate selection depends on the metabolic pathways that are studied. 13C NMR spectroscopy remains a challenging technique that requires several non-standard hardware modifications, infusion of 13C-labeled substrates and sophisticated processing and metabolic modeling. Here the various aspects of direct 13C and indirect 1H-[13C] NMR are reviewed with the aim of providing a practical guide.

de Graaf, Robin A.; Rothman, Douglas L.; Behar, Kevin L.

2013-01-01

188

Novel monosaccharide fermentation products in Caldicellulosiruptor saccharolyticus identified using NMR spectroscopy  

PubMed Central

Background Caldicellulosiruptor saccharolyticus is a thermophilic, Gram-positive, non-spore forming, strictly anaerobic bacterium of interest in potential industrial applications, including the production of biofuels such as hydrogen or ethanol from lignocellulosic biomass through fermentation. High-resolution, solution-state nuclear magnetic resonance (NMR) spectroscopy is a useful method for the identification and quantification of metabolites that result from growth on different substrates. NMR allows facile resolution of isomeric (identical mass) constituents and does not destroy the sample. Results Profiles of metabolites produced by the thermophilic cellulose-degrading bacterium Caldicellulosiruptor saccharolyticus DSM 8903 strain following growth on different monosaccharides (D-glucose, D-mannose, L-arabinose, D-arabinose, D-xylose, L-fucose, and D-fucose) as carbon sources revealed several unexpected fermentation products, suggesting novel metabolic capacities and unexplored metabolic pathways in this organism. Both 1H and 13C nuclear magnetic resonance (NMR) spectroscopy were used to determine intracellular and extracellular metabolite profiles. One dimensional 1H NMR spectral analysis was performed by curve fitting against spectral libraries provided in the Chenomx software; 2-D homonuclear and heteronuclear NMR experiments were conducted to further reduce uncertainties due to unassigned, overlapping, or poorly-resolved peaks. In addition to expected metabolites such as acetate, lactate, glycerol, and ethanol, several novel fermentation products were identified: ethylene glycol (from growth on D-arabinose), acetoin and 2,3-butanediol (from growth on D-glucose, L-arabinose, and D-xylose), and hydroxyacetone (from growth on D-mannose, L-arabinose, and D-xylose). Production of ethylene glycol from D-arabinose was particularly notable, with around 10% of the substrate carbon converted into this uncommon fermentation product. Conclusions The present research shows that C. saccharolyticus, already of substantial interest due to its capability for biological ethanol and hydrogen production, has further metabolic potential for production of higher molecular weight compounds, such as acetoin and 2,3-butanediol, as well as hydroxyacetone and the uncommon fermentation product ethylene glycol. In addition, application of nuclear magnetic resonance (NMR) spectroscopy facilitates identification of novel metabolites, which is instrumental for production of desirable bioproducts from biomass through microbial fermentation.

2013-01-01

189

Synthesis and Characterisation of Pd(II) Complexes with a Derivative of Aminoazobenzene - Dynamic H-1-NMR Study of Cyclopalladation Reactions in DMF  

SciTech Connect

Three new Pd(II) complexes, i.e. [PdCl{sub 2}L]{sub 2} (A), PdCl{sub 2}L{sub 2} (B) and [Pd({mu}-Cl)(L-H)]{sub 2} (C), each with two diethyl [{alpha}-(4-benzenazoanilino)-2-hydroxybenzyl]phosphonates (L) bound to either one or two palladium atoms, are synthesized and characterized by elemental analysis, by IR, UV-vis and solid-state {sup 13}C-NMR spectra. Complexes B and C are additionally characterized by {sup 1}H-, {sup 13}C- and {sup 31}P-NMR and electrospray mass spectrometry (ESMS) studies using dimethylformamide (DMF) as a solvent. In DMF solution adducts A and B undergo spontaneous rearrangement into the cyclopalladated complex C. Dynamic {sup 1}H-NMR study of this rearrangement as well as of the reactions of L with PdCl{sub 2} and Na{sub 2}PdCl{sub 4} revealed a complex equilibrium in DMF solutions and enabled the formation mechanism of all involved species to be resolved. The complex A is immediately solvolyzed producing two molecules of intermediate M [PdCl{sub 2}(L)(DMF)]. Complex M was also the first intermediate in the reaction of L with PdCl{sub 2}. Once present in concentration above 10{sup -5} mol{sup -3} M dimerizes very fast into chloro-bridged dimer [PdCl({mu}-Cl)(L)]{sub 2} (D) which undergoes cyclopalladation and converts into the complex C. The formation of C from the intermediate D is clearly demonstrated by the concentration dependence of the cyclopalladation reaction which has order greater than one. Chloride ions, released by cyclopalladation, react with D by splitting chloro-bridge and binding to metal atoms to produce byproduct [PdCl{sub 3}(L)]{sup -} (T). The same species T are formed in the reaction of L with Na{sub 2}PdCl{sub 4} whereby a chloride ion is replaced by the ligand L. The complex B undergoes similar, but slower, solvolytic reaction producing M and L while further reaction steps are identical as in the solvolysis of A.

Curic, M; Babic, D; Pasa-Tolic, Liljiana; Butkovic, V; Plavec, J; Tusek-Bozic, L

2003-12-01

190

Survey and qualification of internal standards for quantification by 1H NMR spectroscopy.  

PubMed

In quantitative NMR (qNMR) selection of an appropriate internal standard proves to be crucial. In this study, 25 candidate compounds considered to be potent internal standards were investigated with respect to the ability of providing unique signal chemical shifts, purity, solubility, and ease of use. The (1)H chemical shift (delta) values, assignments, multiplicities and number of protons (for each signal), appropriateness (as to be used as internal standards) in four different deuterated solvents (D(2)O, DMSO-d(6), CD(3)OD, CDCl(3)) were studied. Taking into account the properties of these 25 internal standards, the most versatile eight compounds (2,4,6-triiodophenol, 1,3,5-trichloro-2-nitrobenzene, 3,4,5-trichloropyridine, dimethyl terephthalate, 1,4-dinitrobenzene, 2,3,5-triiodobenzoic acid, maleic acid and fumaric acid) were qualified using both differential scanning calorimetry (DSC) and NMR spectroscopy employing highly pure acetanilide as the reference standard. The data from these two methods were compared as well as utilized in the quality assessment of the compounds as internal standards. Finally, the selected internal standards were tested and evaluated in a real case of quantitative NMR analysis of a paracetamol pharmaceutical product. PMID:20207092

Rundlöf, Torgny; Mathiasson, Marie; Bekiroglu, Somer; Hakkarainen, Birgit; Bowden, Tim; Arvidsson, Torbjörn

2010-09-01

191

Probing the surface structure of hydroxyapatite using NMR spectroscopy and first principles calculations.  

PubMed

The surface characteristics of hydroxyapatite (HA) are probed using a combination of NMR spectroscopy and first principles calculations. The NMR spectrum is taken from a bone sample and the first principles calculations are performed using a plane-wave density functional approach within the pseudopotential approximation. The computational work focuses on the (100) and (200) surfaces, which exhibit a representative range of phosphate, hydroxyl and cation bonding geometries. The shielding tensors for the 31P, 1H and 17O nuclei are calculated from the relaxed surface structures using an extension of the projector augmented-wave method. The calculated 31P chemical shifts for the surface slab are found to be significantly different from the bulk crystal and are consistent with the NMR data from bone and also synthetically prepared nanocrystalline samples of HA. Rotational relaxations of the surface phosphate ions and the sub-surface displacement of other nearby ions are identified as causing the main differences. The investigation points to further calculations of other crystallographic surfaces and highlights the potential of using NMR with ab initio modelling to fully describe the surface structure and chemistry of HA, which is essential for understanding its reactivity with the surrounding organic matrix. PMID:18183321

Chappell, Helen; Duer, Melinda; Groom, Nicholas; Pickard, Chris; Bristowe, Paul

2008-01-28

192

Direct (1)H NMR spectroscopy of dissolved organic matter in natural waters.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy arguably provides the greatest insight into the overall chemical composition of dissolved organic matter (DOM). However, in a standard 5 mm NMR probe, a sample of sea water at natural abundance only contains ca. 500-600 ng of organic matter, distributed among the heterogeneous components of DOM. Additionally, the intensity of the water signal, which may be many orders of magnitude greater than the signals from DOM, makes the detection and analysis of DOM at natural abundance extremely demanding. Here, we demonstrate, that although challenging, the application of an improved water suppression technique allows NMR spectra of DOM to be obtained directly (i.e without pre-concentration) for major bodies of water, including rivers, lakes and the ocean. The technique described here provides a compositional overview of an intact sample, permitting researchers to investigate and assess the impact of concentration, isolation and extraction procedures that are employed routinely. Also the technique permits NMR to be performed on 'precious' samples for which traditional isolations are not possible, for example, water from ice cores and pore water, which are key in hydrology and for paleoclimatic reconstruction. PMID:18227951

Lam, Buuan; Simpson, André J

2008-02-01

193

?High Resolution-Magic-Angle Spinning NMR Spectroscopy for Metabolic Phenotyping of Caenorhabditis elegans.  

PubMed

Analysis of model organisms, such as the submillimeter-size Caenorhabditis elegans, plays a central role in understanding biological functions across species and in characterizing phenotypes associated with genetic mutations. In recent years, metabolic phenotyping studies of C. elegans based on (1)H high-resolution magic-angle spinning (HR-MAS) nuclear magnetic resonance (NMR) spectroscopy have relied on the observation of large populations of nematodes, requiring labor-intensive sample preparation that considerably limits high-throughput characterization of C. elegans. In this work, we open new platforms for metabolic phenotyping of C. elegans mutants. We determine rich metabolic profiles (31 metabolites identified) from samples of 12 individuals using a (1)H NMR microprobe featuring high-resolution magic-angle coil spinning (HR-MACS), a simple conversion of a standard HR-MAS probe to ?HR-MAS. In addition, we characterize the metabolic variations between two different strains of C. elegans (wild-type vs slcf-1 mutant). We also acquire a NMR spectrum of a single C. elegans worm at 23.5 T. This study represents the first example of a metabolomic investigation carried out on a small number of submillimeter-size organisms, demonstrating the potential of NMR microtechnologies for metabolomics screening of small model organisms. PMID:24897622

Wong, Alan; Li, Xiaonan; Molin, Laurent; Solari, Florence; Elena-Herrmann, Bénédicte; Sakellariou, Dimitris

2014-06-17

194

Pore-structure determinations of silica aerogels by {sup 129}Xe NMR spectroscopy and imaging.  

SciTech Connect

Silica aerogels represent a new class of open-pore materials with pore dimensions on a scale of tens of nanometers, and are thus classified as mesoporous materials. In this work, we show that the combination of NMR spectroscopy and chemical-shift selective magnetic resonance imaging (MRI) can resolve some of the important aspects of the structure of silica aerogels. The use of xenon as a gaseous probe in combination with spatially resolved NMR techniques is demonstrated to be a powerful, new approach for characterizing the average pore structure and steady-state spatial distributions of xenon atoms in different physicochemical environments. Furthermore, dynamic NMR magnetization transfer experiments and pulsed-field gradient (PFG) measurements have been used to characterize exchange processes and diffusive motion of xenon in samples at equilibrium. In particular, this new NMR approach offers unique information and insights into the nanoscopic pore structure and microscopic morphology of aerogels and the dynamical behavior of occluded adsorbates. MRI provides spatially resolved information on the nature of the flaw regions found in these materials. Pseudo-first-order rate constants for magnetization transfer among the bulk and occluded xenon phases indicate xenon-exchange rate constants on the order of 1 s-1 for specimens having volumes of 0.03 cm3. PFG diffusion measurements show evidence of anisotropic diffusion for xenon occluded within aerogels, with nominal self-diffusivity coefficients on the order of D= 10-3cm2/s.

Gregory, D. M.; Gerald, R. E., II; Botto, R. E.; Chemistry

1998-04-01

195

pKa determination by (1)H NMR spectroscopy - An old methodology revisited.  

PubMed

pKa values of acids and protonated bases have an essential impact on organic synthesis, medicinal chemistry, and material and food sciences. In drug discovery and development, they are of utmost importance for the prediction of pharmacokinetic and pharmacodynamic properties. To date, various methods for the determination of pKa values are available, including UV-spectroscopic, potentiometric, and capillary electrophoretic techniques. An additional option is provided by nuclear magnetic resonance (NMR) spectroscopy. The underlying principle is the alteration of chemical shifts of NMR-active nuclei (e.g., (13)C and (1)H) depending on the protonation state of adjacent acidic or basic sites. When these chemical shifts are plotted against the pH, the inflection point of the resulting sigmoidal curve defines the pKa value. Although pKa determinations by (1)H NMR spectroscopy are reported for numerous cases, the potential of this approach is not yet fully evaluated. We therefore revisited this method with a diverse set of test compounds covering a broad range of pKa values (pKa 0.9-13.8) and made a comparison with four commonly used approaches. The methodology revealed excellent correlations (R(2)=0.99 and 0.97) with electropotentiometric and UV spectroscopic methods. Moreover, the comparison with in silico results (Epik and Marvin) also showed high correlations (R(2)=0.92 and 0.94), further confirming the reliability and utility of this approach. PMID:24462329

Bezençon, Jacqueline; Wittwer, Matthias B; Cutting, Brian; Smieško, Martin; Wagner, Bjoern; Kansy, Manfred; Ernst, Beat

2014-05-01

196

Mapping Inhibitor Binding Modes on an Active Cysteine Protease via NMR Spectroscopy  

PubMed Central

Cruzain is a member of the papain/cathepsin-L family of cysteine proteases, and the major cysteine protease of the protozoan Trypanosoma cruzi, the causative agent of Chagas’ disease. We report an auto-induction methodology that provides soluble-cruzain at high yields (> 30 mg per liter in minimal media). These increased yields provide sufficient quantities of active enzyme for use in NMR-based ligand mapping. Using CD and NMR spectroscopy, we also examined the solution-state structural dynamics of the enzyme in complex with a covalently bound vinyl sulfone inhibitor (K777). We report the backbone amide and side chain carbon chemical shift assignments of cruzain in complex with K777. These resonance assignments were used to identify and map residues located in the substrate binding pocket, including the catalytic Cys25 and His162. Selective 15N-Cys, 15N-His, and 13C-Met labeling was performed to quickly assess cruzain-ligand interactions for a set of eight low molecular weight compounds exhibiting micromolar binding or inhibition. Chemical shift perturbation mapping verifies that six of the eight compounds bind to cruzain at the active site. Three different binding modes were delineated for the compounds, namely covalent, non-covalent, and non-interacting. These results provide examples of how NMR spectroscopy can be used to screen compounds for fast evaluation of enzyme-inhibitor interactions in order to facilitate lead compound identification and subsequent structural studies.

Lee, Gregory M.; Balouch, Eaman; Goetz, David H.; Lazic, Ana; McKerrow, James H.; Craik, Charles S.

2013-01-01

197

Natural-Abundance 43Ca Solid-State NMR Spectroscopy of Bone  

PubMed Central

Structural information about the coordination environment of calcium present in bone is highly valuable in understanding the role of calcium in bone formation, biomineralization, and bone diseases like osteoporosis. While a high-resolution structural study on bone has been considered to be extremely challenging, NMR studies on model compounds and bone minerals have provided valuable insights into the structure of bone. Particularly, the recent demonstration of 43Ca solid-state NMR experiments on model compounds is an important advance in this field. However, application of 43Ca NMR is hampered due to the low natural-abundance and poor sensitivity of 43Ca. In this study, we report the first demonstration of natural-abundance 43Ca magic angle spinning (MAS) NMR experiments on bone, using powdered bovine cortical bone samples. 43Ca NMR spectra of bovine cortical bone are analyzed by comparing to the natural-abundance 43Ca NMR spectra of model compounds including hydroxyapatite and carbonated apatite. While 43Ca NMR spectra of hydroxyapatite and carbonated apatite are very similar, they significantly differ from that of cortical bone. Raman spectroscopy shows that the calcium environment in bone is more similar to carbonated apatite than hydroxyapatite. A close analysis of 43Ca NMR spectra reveals that the chemical shift frequencies of cortical bone and 10% carbonated apatite are similar but the quadrupole coupling constant of cortical bone is larger than that measured for model compounds. In addition, our results suggest that an increase in the carbonate concentration decreases the observed 43Ca chemical shift frequency. A comparison of experimentally obtained 43Ca MAS spectra with simulations reveal a 3:4 mole ratio of Ca-I:Ca-II sites in carbonated apatite and a 2.3:3 mole ratio for hydroxyapatite. 2D triple-quantum 43Ca MAS experiments performed on a mixture of carbonated apatite and the bone protein osteocalcin reveal the presence of protein-bound and free calcium sites, which is in agreement with a model developed from X-ray crystal structure of the protein.

Xu, Jiadi; Zhu, Peizhi; Gan, Zhehong; Sahar, Nadder; Tecklenburg, Mary; Morris, Michael D.; Kohn, David H.; Ramamoorthy, Ayyalusamy

2010-01-01

198

N-15 NMR Spectroscopy as a Method for Comparing the Rates of Imidization of Several Diamines  

NASA Technical Reports Server (NTRS)

The relative rates of the conversion of amide-acid to imide was measured for a series or aromatic diamines that have been identified as potential replacements for 4,4'-methylene dianiline (MDA) in high-temperature polyimides and polymer composites. These rates were compared with the N-15 NMR resonances of the unreacted amines. The initial rates of imidization track with the difference in chemical shift between the amine nitrogens in MDA and those in the subject diamines. This comparison demonstrated that N-15 NMR spectroscopy is appropriate for the rapid screening of candidate diamines to determine their reactivity relative to MDA, and can serve to provide guidance to the process of creating the time-temperature profiles used in processing these materials into polymer matrix composites.

Johnson, J. Christopher; Kuczmarski, Maria A.

2006-01-01

199

Synthesis of beta-O-4-type artificial lignin polymers and their analysis by NMR spectroscopy.  

PubMed

We describe the synthesis and NMR spectroscopic analysis of three artificial lignin polymers containing only the beta-O-4 substructure: syringyl-type homopolymer, p-hydroxyphenyl-type homopolymer and guaiacyl/syringyl-type heteropolymer. Using gel permeation chromatography, the weight-average degree of polymerization (DP(w)) of the three polymers was determined as 19.2, 38.6, and 13.9, respectively. The polymers were prepared based on the synthetic methodology of guaiacyl-type homopolymer, and were fully characterized using (1)H-, (13)C-, and (1)H-(13)C NMR spectroscopy of the acetylated and non-acetylated forms. The spectra of guaiacyl/syringyl-type heteropolymers were in good agreement with those of the beta-O-4 substructure of milled wood lignin obtained from the hardwood of Japanese white birch. PMID:18688492

Kishimoto, Takao; Uraki, Yasumitsu; Ubukata, Makoto

2008-08-21

200

Isotope labeling methods for studies of excited protein states by relaxation dispersion NMR spectroscopy.  

PubMed

The utility of nuclear magnetic resonance (NMR) spectroscopy as a tool for the study of biomolecular structure and dynamics has benefited from the development of facile labeling methods that incorporate NMR active probes at key positions in the molecule. Here we describe a protocol for the labeling of proteins that facilitates their study using a technique that is sensitive to millisecond conformational exchange processes. The samples necessary for an analysis of exchange dynamics are discussed, using the Abp1p SH3 domain from Saccharomyces cerevisiae as an example. For this system, the time frame for production of each sample, including in vitro refolding, is about 80 h. The samples so produced facilitate the measurement of accurate chemical shifts of low populated, invisible conformers that are part of the exchange pathway. The accuracy of the methodology has been established experimentally and the chemical shifts that are obtained provide important restraints in structure calculations of the excited state. PMID:19876024

Lundström, Patrik; Vallurupalli, Pramodh; Hansen, D Flemming; Kay, Lewis E

2009-01-01

201

Low Temperature 65Cu NMR Spectroscopy of the Cu+ Site in Azurin  

PubMed Central

65Cu central-transition NMR spectroscopy of the blue copper protein azurin in the reduced Cu(I) state, conducted at 18.8 Tesla and 10 K, gave a strongly second order quadrupole perturbed spectrum, which yielded a 65Cu quadrupole coupling constant of ą71.2 ą 1 MHz, corresponding to an electric field gradient of ą1.49 atomic units at the copper site, and an asymmetry parameter of approximately 0.2. Quantum chemical calculations employing second order Mřller-Plesset perturbation theory and large basis sets successfully reproduced these experimental results. Sensitivity and relaxation times were quite favorable, suggesting that NMR may be a useful probe of the electronic state of copper sites in proteins.

Lipton, Andrew S.; Heck, Robert W.; de Jong, Wibe A.; Gao, Amy R.; Wu, Xiongjian; Roehrich, Adrienne; Harbison, Gerard S.; Ellis, Paul D.

2009-01-01

202

Natural abundance high-resolution solid state 2 H NMR spectroscopy  

NASA Astrophysics Data System (ADS)

We report for the first time an approach for natural abundance solid state 2H NMR spectroscopy involving magic angle sample spinning (MAS), high-power 1H decoupling (HPPD) and 1H- 2H cross polarization (CP). Taking tetrakis(trimethylsilyl)silane (TTMSS), adamantane, 1-chloroadamantane, hexamethylbenzene (HMB), 2,2-dimethyl-1,3-propanediol (DMPD) and 2-hydroxymethyl-2-methyl-1,3-propanediol (HMPD) as examples, it has been shown that the combination of HPPD and MAS can be applied readily to study rotator phase solids, allowing isotropic peaks arising from chemically inequivalent 2H nuclei to be resolved. For natural abundance samples of TTMSS and chloroadamantane, it has been shown that 2H CP/HPPD/MAS NMR experiments, involving polarization transfer from 1H to 2H, may provide considerable sensitivity enhancement in comparison with single pulse experiments.

Aliev, Abil E.; Harris, Kenneth D. M.; Apperley, David C.

1994-08-01

203

Natural abundance high-resolution solid state 2 H NMR spectroscopy  

NASA Astrophysics Data System (ADS)

We report for the first time an approach for natural abundance solid state 2 H NMR spectroscopy involving magic angle sample spinning (MAS), high-power 1 H decoupling (HPPD) and 1 H- 2 H cross polarization (CP). Taking tetrakis(trimethylsilyl)silane (TTMSS), adamantane, 1-chloroadamantane, hexamethylbenzene (HMB), 2,2-dimethyl-1,3-propanediol (DMPD) and 2-hydroxymethyl-2-methyl-1,3-propanediol (HMPD) as examples, it has been shown that the combination of HPPD and MAS can be applied readily to study rotator phase solids, allowing isotropic peaks arising from chemically inequivalent 2 H nuclei to be resolved. For natural abundance samples of TTMSS and chloroadamantane, it has been shown that 2 H CP/HPPD/MAS NMR experiments, involving polarization transfer from 1 H to 2 H, may provide considerable sensitivity enhancement in comparison with single pulse experiments.

Aliev, Abil E.; Harris, Kenneth D. M.; Apperley, David C.

1994-08-01

204

A dynamic nuclear polarization strategy for multi-dimensional Earth's field NMR spectroscopy.  

PubMed

Dynamic nuclear polarization (DNP) is introduced as a powerful tool for polarization enhancement in multi-dimensional Earth's field NMR spectroscopy. Maximum polarization enhancements, relative to thermal equilibrium in the Earth's magnetic field, are calculated theoretically and compared to the more traditional prepolarization approach for NMR sensitivity enhancement at ultra-low fields. Signal enhancement factors on the order of 3000 are demonstrated experimentally using DNP with a nitroxide free radical, TEMPO, which contains an unpaired electron which is strongly coupled to a neighboring (14)N nucleus via the hyperfine interaction. A high-quality 2D (19)F-(1)H COSY spectrum acquired in the Earth's magnetic field with DNP enhancement is presented and compared to simulation. PMID:18926746

Halse, Meghan E; Callaghan, Paul T

2008-12-01

205

2H-DNP-enhanced 2H-13C solid-state NMR correlation spectroscopy.  

PubMed

Perdeuteration of biological macromolecules for magic angle spinning solid-state NMR spectroscopy can yield high-resolution (2)H-(13)C correlation spectra and the method is therefore of great interest for the structural biology community. Here we demonstrate that the combination of sample deuteration and dynamic nuclear polarization yields resolved (2)H-(13)C correlation spectra with a signal enhancement of epsilon > or = 700 compared to a spectrum recorded with microwaves off and otherwise identical conditions. To our knowledge, this is the first time that (2)H-DNP has been employed to enhance MAS-NMR spectra of a biologically relevant system. The DNP process is studied using several polarizing agents and the technique is applied to obtain (2)H-(13)C correlation spectra of U-[(2)H, (13)C] proline. PMID:20458422

Maly, Thorsten; Andreas, Loren B; Smith, Albert A; Griffin, Robert G

2010-06-14

206

Strategy for the Stereochemical Assignment of Tris-Heteroleptic Ru(II) Complexes by NMR Spectroscopy  

PubMed Central

The relative stereochemistry of tris-heteroleptic ruthenium complexes [Ru(pp)(pp?)(pp?)](PF6)2, where pp = 1,10-phenanthroline-4-carboxamide, pp? = 5,6-dimethyl-1,10-phenanthroline, and pp? = 7,8-dimethyl dipyrido[3,2-a:2?,3?-c]phenazine, was studied using NMR spectroscopy. The 1H and 13C spectra were assigned by using (DQF)-COSY, HSQC, and HMBC experiments for the two diastereomers, each a pair of enantiomers. NOE contacts between the neighboring ligands differentiated the two halves of each symmetrical ligand, thus enabling a full assignment of the NMR signals and an accurate determination of the relative stereochemistry of the complexes. Introduction of an additional chiral center to ligand pp by coupling it with L-lysine caused removal of the enantiomerism. Thus four diastereomers were observed and their relative stereochemistry determined.

Xie, Xiulan; Mulcahy, Seann P.; Meggers, Eric

2009-01-01

207

An instrument control and data analysis program for NMR imaging and spectroscopy  

SciTech Connect

We describe a software environment created to support real-time instrument control and signal acquisition as well as array-processor based signal and image processing in up to five dimensions. The environment is configured for NMR imaging and in vivo spectroscopy. It is designed to provide flexible tools for implementing novel NMR experiments in the research laboratory. Data acquisition and processing operations are programmed in macros which are loaded in assembled from to minimize instruction overhead. Data arrays are dynamically allocated for efficient use of memory and can be mapped directly into disk files. The command set includes primitives for real-time control of data acquisition, scalar arithmetic, string manipulation, branching, a file system and vector operations carried out by an array processor. 6 figs.

Roos, M.S.; Mushlin, R.A.; Veklerov, E.; Port, J.D.; Ladd, C.; Harrison, C.G.

1988-01-01

208

Earle K. Plyler Prize for Molecular Spectroscopy Talk: Coherent Ultrafast Multidimensional Spectroscopy of Molecules; From NMR to X-rays  

NASA Astrophysics Data System (ADS)

Multidimensional spectroscopic techniques which originated with NMR in the 1970s have been extended over the past 15 years to the optical regime. NMR spectroscopists have developed methods for the design of pulse sequences that resolve otherwise congested spectra, enhance selected spectral features and reveal desired dynamical events. The major experimental and computational advances required for extending these ideas to study electronic and vibrational motions on the femtosecond timescale will be surveyed. The response of complex molecules and semiconductor nanostructures to sequences of optical pulses provides snapshots of their structure and dynamical processes. Two-dimensional correlation plots of the signals show characteristic cross-peak patterns which carry information about hydrogen bonding, secondary structure fluctuations of proteins and amyloid fibrils, and coherent and incoherent energy and charge transfer in photosynthetic complexes. Double quantum coherence signals that are induced by correlations among electrons or excitons allow the visualization of correlated wavefunctions. Future extensions to the attosecond regime using xray pulses will be discussed. Since core excitations are highly localized at selected atoms, such signals can monitor the motions of valence electron wavepackets in real space with atomic spatial resolution. Common principles underlying coherent spectroscopy techniques for spins, valence electrons, and core electronic excitations, spanning frequencies from radiowaves, infrared, ultraviolet all the way to hard X-rays will be discussed. [4pt] [1] "Coherent Multidimensional Optical Probes for Electronic Correlations and Exciton Dynamics; from NMR to X-rays", S. Mukamel, D. Abramavicius, L. Yang, W.Zhuang, I.V. Schweigert and D. Voronine. Acct.Chem.Res. Acct.Chem.Res. 42, 553-562 (2009). [0pt] [2] "Coherent Multidimensional Optical Spectroscopy Excitons in Molecular Aggregates; Quasiparticle vs. Supermolecule Perspectives", D. Abramavicius, B. Palmieri, D. Voronine, F. Sanda and S. Mukamel, Chem. Rev. 109, 2350-2408 (2009).

Mukamel, Shaul

2011-03-01

209

Organic carbon and sulphur compounds in wetland soils: insights on structure and transformation processes using Kedge XANES and NMR spectroscopy  

Microsoft Academic Search

X-ray absorption near-edge structure (XANES) and nuclear magnetic resonance (NMR) spectroscopy were used in combination to characterize organic carbon structures in a series of wetland soils in Saskatchewan, and XANES spectroscopy was also used to examine sulphur speciation in the soils. The organic C contents of most of the wetland soils are consistently higher by a factor of two to

Aleksander Jokic; Jeffrey N Cutler; Elena Ponomarenko; Garth van der Kamp; Darwin W Anderson

2003-01-01

210

Detection and characterization of serine and threonine hydroxyl protons in Bacillus circulans xylanase by NMR spectroscopy.  

PubMed

Hydroxyl protons on serine and threonine residues are not well characterized in protein structures determined by both NMR spectroscopy and X-ray crystallography. In the case of NMR spectroscopy, this is in large part because hydroxyl proton signals are usually hidden under crowded regions of (1)H-NMR spectra and remain undetected by conventional heteronuclear correlation approaches that rely on strong one-bond (1)H-(15)N or (1)H-(13)C couplings. However, by filtering against protons directly bonded to (13)C or (15)N nuclei, signals from slowly-exchanging hydroxyls can be observed in the (1)H-NMR spectrum of a uniformly (13)C/(15)N-labeled protein. Here we demonstrate the use of a simple selective labeling scheme in combination with long-range heteronuclear scalar correlation experiments as an easy and relatively inexpensive way to detect and assign these hydroxyl proton signals. Using auxtrophic Escherichia coli strains, we produced Bacillus circulans xylanase (BcX) labeled with (13)C/(15)N-serine or (13)C/(15)N-threonine. Signals from two serine and three threonine hydroxyls in these protein samples were readily observed via (3)JC-OH couplings in long-range (13)C-HSQC spectra. These scalar couplings (~5-7 Hz) were measured in a sample of uniformly (13)C/(15)N-labeled BcX using a quantitative (13)C/(15)N-filtered spin-echo difference experiment. In a similar approach, the threonine and serine hydroxyl hydrogen exchange kinetics were measured using a (13)C/(15)N-filtered CLEANEX-PM pulse sequence. Collectively, these experiments provide insights into the structural and dynamic properties of several serine and threonine hydroxyls within this model protein. PMID:24306180

Brockerman, Jacob A; Okon, Mark; McIntosh, Lawrence P

2014-01-01

211

Micellization in aqueous solution of an ethylene oxide-propylene oxide triblock copolymer, investigated with 1H NMR spectroscopy, pulsed-field gradient NMR, and NMR relaxation.  

PubMed

(1)H nuclear magnetic resonance (NMR) spectroscopy has been applied to study the temperature and concentration-induced micellization of a poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymer, Pluronic P105, in D(2)O solutions in the temperature range from 5 to 45 degrees C and the concentration range from 0.01 to 15% (w/v). The intrinsic probes, the chemical shift, and the half-height width of the PO CH(3) signal are very sensitive to the local environment and can be used to characterize the temperature and concentration-dependent aggregation process. When the temperature approaches the critical micellization temperature or the polymer concentration reaches the critical micellization concentration, the chemical shift of the PO CH(3) signal moves toward lower ppm values and the half-height width of the PO CH(3) signal shows a sudden increase. It indicates that the methyl groups are experiencing a progressively less polar environment and transferring from water to the hydrophobic micellar core. The hydrodynamic radius of the unimers and the micelles are determined as be 1.8 and 5.0 nm by means of pulsed-field gradient spin-echo (PGSE) NMR. They were independent of temperature and concentration. The drastic shortening of spin-lattice relaxation time T(1) for the PO CH(3)/CH(2) protons in the transition region suggested that the PPO blocks are located in a "liquid-like" micellar core, whereas the exponential increase of T(1) for the PEO CH(2) protons implied that the PEO blocks are still keeping in contact with surrounding water. Thermodynamics analysis according to a closed association model shows that the micellization process is entropy-driven and has an endothermic micellization enthalpy. PMID:17482638

Ma, Junhe; Guo, Chen; Tang, Yalin; Xiang, Junfeng; Chen, Shu; Wang, Jing; Liu, Huizhou

2007-08-15

212

High-resolution magic angle spinning NMR spectroscopy of human osteoarthritic cartilage.  

PubMed

Osteoarthritis (OA) is a degenerative disease of the joints and results in changes in the biochemical composition of cartilage. Previous studies have been undertaken that have used high-resolution NMR spectroscopy to study the biochemical composition of porcine, canine and bovine cartilage. In the present study, high-resolution magical angle spinning (HR-MAS) NMR spectroscopy at 11.7 T has been used to characterize metabolites and detect differences in the spectral signature of human knee articular cartilage from non-OA healthy cadaver knees and samples acquired from severe OA patients at the time of total knee replacement surgery. A statistically significant difference in the alanine (1.47 p.p.m.), N-acetyl (2.04 p.p.m.), choline (3.25 p.p.m.) and glycine (3.55 p.p.m.) metabolite levels was observed between healthy and OA specimens. The results of the present study indicate that a decrease in the intensity of N-acetyl resonance occurs in the later stages of OA. A positive correlation of the N-acetyl levels as measured by (1)H HR-MAS NMR spectroscopy with the total proteoglycan content in the same cartilage specimens as measured by the glycosaminoglycan (GAG) assay was observed. This indicates that N-acetyl can serve as an important bio-marker of OA disease progression. A decrease in the alanine concentration in OA may be attributed to the degradation of the collagen framework with disease progression and eventual loss of the degradation products that are transported from cartilage into the synovial cavity. PMID:21850648

Shet, Keerthi; Siddiqui, Sarmad M; Yoshihara, Hikari; Kurhanewicz, John; Ries, Michael; Li, Xiaojuan

2012-04-01

213

Heteronuclear dipolar couplings, total spin coherence, and bilinear rotations in NMR spectroscopy  

SciTech Connect

In Chapter 1 a variety of different introductory topics are presented. The potential complexity of the nuclear magnetic resonsnace (NMR) spectra of molecules dissolved in liquid crystal solvents serves to motivate the development of multiple quantum (MQ) spectroscopy. The basics of MQ NMR are reviewed in Chapter 2. An experimental search procedure for the optimization of MQ pulse sequences is introduced. Chapter 3 discusses the application of MQ NMR techniques to the measurement of dipolar couplings in heteronuclear spin systems. The advantages of MQ methods in such systems are developed and experimental results for partially oriented (1-/sup 13/C) benzene are presented. Several pulse sequences are introduced which employ a two-step excitation of heteronuclear MQ coherence. A new multiple pulse method, involving the simultaneous irradiation of both rare and abundant spin species, is described. The problem of the broadening of MQ transitions due to magnetic field inhomogeneity is considered in Chapter 4. The method of total spin coherence transfer echo spectroscopy (TSCTES) is presented, with experimets on partially oriented acetaldehyde serving to demonstrate this new technique. TSCTES results in MQ spectra which are sensitive to all chemical shifts and spin-spin couplings and which are free of inhomogeneous broadening. In Chapter 5 the spectroscopy of spin systems of several protons and a /sup 13/C nucleus in the isotropic phase is discussed. The usefulness of the heteronuclear bilinear rotation as a calculational tool is illustrated. Compensated bilinear ..pi.. rotations, which are relatively insensitive to timing parameter missets, are presented. A new technique for homonuclear proton decoupling, Bilinear Rotation Decoupling, is described and its success in weakly coupled systems is demonstrated.

Garbow, J.R.

1983-07-01

214

Study of order and dynamics in liquid crystalline materials by carbon-13 and deuterium NMR spectroscopy  

NASA Astrophysics Data System (ADS)

This dissertation investigates the phase structures, molecular structures and diffusion motions in some recently discovered liquid crystals using 1D and 2D carbon-13 and deuterium NMR spectroscopy. Two classes of liquid crystals are involved: chiral rod-like liquid crystals and banana mesogens. Our investigations of these new materials were divided into five main sections. The ordering and structures of banana liquid crystals and chiral rod-like mesogens were extracted from solid-state 13C NMR experiments including Separated-Local-Field study based on Lee-Goldberg Cross-Polarization (LGCP-SLF) and temperature dependent chemical shifts. The principal values of CSA tensor were measured using Separation of Undistorted CSA Powder patterns by Effortless Recoupling (SUPER) experiment. Some ID and 2D pulse experiments were performed for the assignment of carbon peaks, such as Cross-Polarization Polarization-Inversion (CPPI), HECTOR and so on. The soliton-like distortion of the helicoidal structure in the chiral smectic C phase (SmC*) of 8BEF5 liquid crystal was observed by the angular dependent DNMR patterns, and quantitatively interpreted based on Landau theory. The distortion was induced by the NMR magnetic field. The phase structure and interlayer diffusion in anticlinic Sm C* phases (Sm C*A , Sm C*Fi1 and Sm C*Fi2 ) of 10B1M7 liquid crystal were measured using angular dependent DNMR lineshapes and echo intensities. This work represents the first study of ferrielectric smectic phases by means of NMR. Measurements of the interlayer diffusion in synclinic and anticlinic SmC* phases (SmC*, Sm C*Fi1 and Sm C*Fi2 ) of 10B1M7 were carried out using 2H NMR exchange experiments. The phase structures of anticlinic SmC* phases were also determined using the same technique. A 'deformed clock model' was found to be appropriate for these phases. Molecular structures and dynamics were investigated in an exotic B 2 phase of a banana liquid crystal Pbis11BB by means of CP-MAS 13C NMR, MAS 2D 13C NMR exchange and LGCP-SLF (with MAS) experiments. These experiments showed that the molecules have asymmetric conformation in the solid state and carry on much slower motions in solid and liquid states compared to banana molecules in the same homologous series.

Xu, Jiadi

215

Structural studies of racecadotril and its process impurities by NMR and mass spectroscopy.  

PubMed

Three unknown impurities in racecadotril bulk drug at levels below 0.5% were detected by simple reverse phase isocratic high performance liquid chromatography (HPLC). Structures for these impurities were proposed by molecular ion information and their fragmentation pattern obtained by LC-MS and these impurities were confirmed by NMR spectroscopy. The impurities I, II and III were characterized as benzyl 2-methyl carboximido acetate, benzyl 2-phenyl ethyl carboximido acetate, and benzyl 2-(1-benzyl vinyl carboximido) acetate. These structures were further confirmed by co-injecting of synthetic standards of impurities with racecadotril. The mechanism of the formation of these process related impurities is discussed. PMID:17283655

Reddy, K Mallikarjun; Babu, J Moses; Sudhakar, P; Sharma, M S P; Reddy, G Sudershan; Vyas, K

2006-12-01

216

Early stage monitoring of miltefosine induced apoptosis in KB cells by multinuclear NMR spectroscopy.  

PubMed

Synthetic ether lipids, like miltefosine (hexadecylphosphocholine), an alkylphosphocholine, are antineoplastic agents in vitro and in vivo. Their mode of action is mediated via the cell membrane, but the mechanism is still unclear. Miltefosine induces apoptosis in human epithelial KB cells, but slows down only proliferation in rat C6 glioma cells. NMR spectroscopy on lipid extracts reveals increased diacylglycerol and triacyglycerol biosynthesis in KB cells prior to DNA fragmentation indicating a CTP:phosphocholine-cytidylyl-transferase (CT) inhibition by the drug. Although C6 cells were morphologically affected by alterations in phospholipid composition and metabolism by a long term treatment (23 days) with the drug, no persistent diacylglycerol increase is observed. PMID:8694511

Engelmann, J; Henke, J; Willker, W; Kutscher, B; Nössner, G; Engel, J; Leibfritz, D

1996-01-01

217

Analysis of epoxy resin formulations by /sup 13/C NMR spectroscopy  

SciTech Connect

The chloroform soluble components of several epoxy resin formulations were analyzed by /sup 13/C NMR spectroscopy. The technique permits the components of an epoxy resin formulation to be identified on a routine basis with a high degree of confidence. Narmco's 5208 contained MY-720 and EpiRez SU-7 or SU-8. Two versions of Ferro's CE-9000 contained ERL-0510 and EpiRez SU-7 or SU-8. Although the method is semiquantitative, it was able to distinguish between the two versions of Ferro's CE-9000 in which the concentration of ERL-0510 differs by approximately a factor of two.

Assink, R.A.; Gurule, F.T.

1981-02-01

218

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

NASA Astrophysics Data System (ADS)

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

Berns, Anne E.; Conte, Pellegrino

2010-05-01

219

Dynamic processes and chemical composition of Lepidium sativum seeds determined by means of field-cycling NMR relaxometry and NMR spectroscopy.  

PubMed

Proton nuclear magnetic resonance (NMR) techniques, such as field-cycling relaxometry, wide-line NMR spectroscopy, and magic angle spinning NMR spectroscopy, were applied to study the seeds of cress, Lepidium sativum. Field-cycling NMR relaxometry was used for the first time to investigate the properties of the whole molecular system of dry cress seeds. This method not only allowed the dynamics to be studied, but was also successful in the differentiation among the solid (i.e., carbohydrates, proteins, or fats forming a solid form of lipids) and liquid-like (oil compounds) components of the seeds. The (1)H NMR relaxation dispersion of oils was interpreted as a superposition of intramolecular and intermolecular contributions. The intramolecular part was described in terms of a Lorentzian spectral density function, whereas a log-Gaussian distribution of correlation times was applied for the intermolecular dipole-dipole contribution. The models applied led to very good agreement with the experimental data and demonstrate that the contribution of the intermolecular relaxation to the overall relaxation should not be disregarded, especially at low frequencies. A power-law frequency dependence of the proton relaxation dispersion was used for the interpretation of the solid components. From the analysis of the (1)H wide-line NMR spectra of the liquid-like component of hydrated cress seeds, we can conclude that the contribution of oil protons should always be taken into account when evaluating the spin-lattice relaxation times values or measuring the moisture and oil content. The application of (1)H magic angle spinning NMR significantly improves resolution in the liquid-like spectrum of seeds and allows the determination of the chemical composition of cress seeds. PMID:23001307

Rachocki, A; Latanowicz, L; Tritt-Goc, J

2012-12-01

220

Investigation of M(III) chelates by NMR and luminescence spectroscopy  

SciTech Connect

This paper studies the structure of complexes of lanthanides with ethylenediamine-disphosphoric acid (EDDP) and ethylenediaminetetraphosphonic acid (EDTP) in solution with the aid of /sup 1/H NMR spectroscopy and luminescence spectroscopy. It has been shown that complexes of EDDP with different lanthanides have the same structure, which is not dependent on the pH. The structure of the complexes of EDTP with europium, praseodymium, and holmium differs from the structure of the complexes with ytterbium and thulium. The structures of the isolated complexes of lanthanides, calcium, and indium have been studied with the aid of the luminescence and excitation spectra of a europium impurity ion. It has been shown that the structures of the complexes of the lanthanides and indium are similar.

Babushkina, T.A.; Kolin, V.F.; Koreneva, L.G.; Lazukova, L.B.

1986-03-01

221

Structural determination of a key exopolysaccharide in mixed culture aerobic sludge granules using NMR spectroscopy.  

PubMed

Nuclear magnetic resonance (NMR) techniques were used to elucidate the structure of an exopolysaccharide material previously revealed to be important in formation of aerobic granules. The 1D NMR spectral data acquired showed that this gel-forming polysaccharide was a major component of granular EPS, while 1D and 2D NMR spectra showed it consisted of eight sugar residues. These were assigned as ?-galactose, ?-rhamnose, 2-acetoamido-2-deoxy-?-galactopyranuronic acid, ?-mannose, ?-galactose, ?-glucuronate, ?-glucosamine, and N-acetyl ?-galactosamine. With the exception of 2-acetoamido-2-deoxy-?-galactopyranuronic acid, a highly unusual sugar, their presence was confirmed with high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Carbon and proton shifts were assigned for each sugar. Heteronuclear multiple bond correlation (HMBC) and nuclear Overhauser enhancement spectroscopy (NOESY) were used to identify linkage sites between individual sugar residues. This gel-forming exopolysaccharide appeared to be a highly complex single heteropolysaccharide with a repeat sequence of ?-galactose, ?-mannose, ?-glucosamine, N-acetyl-?-galactosamine, and 2-acetoamido-2-deoxy-?-galactopyranuronic acid. It has a disaccharide branch of ?-galactose and ?-glucuronic acid attached to 2-acetoamido-2-deoxy-?-galactopyranuronic acid and an ?-rhamnose branch attached to ?-galactose. PMID:21033741

Seviour, Thomas; Lambert, Lynette K; Pijuan, Maite; Yuan, Zhiguo

2010-12-01

222

Rapid Etiological Classification of Meningitis by NMR Spectroscopy Based on Metabolite Profiles and Host Response  

PubMed Central

Bacterial meningitis is an acute disease with high mortality that is reduced by early treatment. Identification of the causative microorganism by culture is sensitive but slow. Large volumes of cerebrospinal fluid (CSF) are required to maximise sensitivity and establish a provisional diagnosis. We have utilised nuclear magnetic resonance (NMR) spectroscopy to rapidly characterise the biochemical profile of CSF from normal rats and animals with pneumococcal or cryptococcal meningitis. Use of a miniaturised capillary NMR system overcame limitations caused by small CSF volumes and low metabolite concentrations. The analysis of the complex NMR spectroscopic data by a supervised statistical classification strategy included major, minor and unidentified metabolites. Reproducible spectral profiles were generated within less than three minutes, and revealed differences in the relative amounts of glucose, lactate, citrate, amino acid residues, acetate and polyols in the three groups. Contributions from microbial metabolism and inflammatory cells were evident. The computerised statistical classification strategy is based on both major metabolites and minor, partially unidentified metabolites. This data analysis proved highly specific for diagnosis (100% specificity in the final validation set), provided those with visible blood contamination were excluded from analysis; 6–8% of samples were classified as indeterminate. This proof of principle study suggests that a rapid etiologic diagnosis of meningitis is possible without prior culture. The method can be fully automated and avoids delays due to processing and selective identification of specific pathogens that are inherent in DNA-based techniques.

Himmelreich, Uwe; Malik, Richard; Kuhn, Till; Daniel, Heide-Marie; Somorjai, Ray L.; Dolenko, Brion; Sorrell, Tania C.

2009-01-01

223

Functional group analysis in coal and on coal surfaces by NMR spectroscopy  

SciTech Connect

An accurate knowledge of the oxygen-bearing labile hydrogen functional groups (e.g., carboxylic acids, phenols and alcohols) in coal is required for today's increasingly sophisticated coal cleaning and beneficiation processes. Phospholanes (compounds having the general structure -POCH{sub 2}CH{sub 2}O (1)) are being investigated as reagents for the tagging of liable hydrogen functional groups in coal materials with the NMR-active {sup 31}P nucleus. Of twelve such reagents investigated so far, 2 (2-chloro-1,3-dioxaphospholane, ClPOCH{sub 2}CH{sub 2}O) and 8 (2-chloro-1,3-dithiaphospholane, ClPSCH{sub 2}CH{sub 2}S) have been found to be useful in identifying and quantitating, by {sup 31}P NMR spectroscopy, labile hydrogen functional groups in an Illinois No. 6 coal condensate. Reagent 2 has also been used to quantitate moisture in pyridine extracts of Argonne Premium Coal Samples. Preliminary {sup 119}Sn NMR spectroscopic results on model compounds with the new reagent CF{sub 3}C(O)NHSnMe{sub 3} (N-trimethylstannyltrifluoroacetamide, 14) suggest that labile hydrogen functional groups in coal materials may be more precisely identified with 14 than with phospholanes. 14 refs., 2 figs., 2 tabs.

Verkade, J.G.

1990-01-01

224

Biological effects and physical safety aspects of NMR imaging and in vivo spectroscopy  

SciTech Connect

An assessment is made of the biological effects and physical hazards of static and time-varying fields associated with the NMR devices that are being used for clinical imaging and in vivo spectroscopy. A summary is given of the current state of knowledge concerning the mechanisms of interaction and the bioeffects of these fields. Additional topics that are discussed include: (1) physical effects on pacemakers and metallic implants such as aneurysm clips, (2) human health studies related to the effects of exposure to nonionizing electromagnetic radiation, and (3) extant guidelines for limiting exposure of patients and medical personnel to the fields produced by NMR devices. On the basis of information available at the present time, it is concluded that the fields associated with the current generation of NMR devices do not pose a significant health risk in themselves. However, rigorous guidelines must be followed to avoid the physical interaction of these fields with metallic implants and medical electronic devices. 476 refs., 5 figs., 2 tabs.

Tenforde, T.S.; Budinger, T.F.

1985-08-01

225

Sensitivity and resolution enhancement in solid-state NMR spectroscopy of bicelles  

NASA Astrophysics Data System (ADS)

Magnetically aligned bicelles are becoming attractive model membranes to investigate the structure, dynamics, geometry, and interaction of membrane-associated peptides and proteins using solution- and solid-state NMR experiments. Recent studies have shown that bicelles are more suitable than mechanically aligned bilayers for multidimensional solid-state NMR experiments. In this work, we describe experimental aspects of the natural abundance 13C and 14N NMR spectroscopy of DMPC/DHPC bicelles. In particular, approaches to enhance the sensitivity and resolution and to quantify radio-frequency heating effects are presented. Sensitivity of 13C detection using single pulse excitation, conventional cross-polarization (CP), ramp-CP, and NOE techniques are compared. Our results suggest that the proton decoupling efficiency of the FLOPSY pulse sequence is better than that of continuous wave decoupling, TPPM, SPINAL, and WALTZ sequences. A simple method of monitoring the water proton chemical shift is demonstrated for the measurement of sample temperature and calibration of the radio-frequency-induced heating in the sample. The possibility of using 14N experiments on bicelles is also discussed.

Dvinskikh, Sergey V.; Yamamoto, Kazutoshi; Dürr, Ulrich H. N.; Ramamoorthy, Ayyalusamy

2007-02-01

226

Synthesis and structural study of benzamarones by X-ray and NMR spectroscopy  

NASA Astrophysics Data System (ADS)

In this work only one diastereomer of benzamarone (1,2,3,4,5-pentaphenylpentan-1,5-dione) 1 was isolated from tandem condensation/addition reaction between deoxybenzoin and benzaldehyde in alkaline medium and by Michael addition of deoxybenzoin to ( E)-2-phenylchalcone. Compound 1 was investigated by single crystal X-ray diffraction: C 35H 28O 2, Mr = 480.57, triclinic system, space group P1 with unit cell parameters a = 11.489(2), b = 11.669(2), c = 11.855(2) Ĺ, ? = 104.31(4), ? = 116.91(3), ? = 98.96(3)°, V = 1305.6(4) Ĺ 3, Z = 2, T = 25(2) °C, ?calc = 1.222 gr/cm 3, ? = 0.074 mm -1. This study allowed us to assign the configuration 2R,4R/2S,4S corresponding to the diastereomer racemate C ( Fig. 1) due to the fact that the crystal structure exhibits two independent molecules in the unit cell. Data obtained using NMR spectroscopy [1D and 2D NMR] are agreement with those obtained by X-ray diffraction. By comparison of NMR data, the configuration corresponding to the diastereomer racemate C was assigned to other substituted benzamarones synthesized by us, which present two and three stereocenters in their structure.

Mufato, Jorge D.; Vega, Daniel R.; Aguirre, José M.; de la Faba, Diego J.; Lantańo, Beatriz

2011-02-01

227

Quantitative evaluation of noncovalent interactions between glyphosate and dissolved humic substances by NMR spectroscopy.  

PubMed

Interactions of glyphosate (N-phosphonomethylglycine) herbicide (GLY) with soluble fulvic acids (FAs) and humic acids (HAs) at pH 5.2 and 7 were studied by (1)H and (31)P NMR spectroscopy. Increasing concentrations of soluble humic matter determined broadening and chemical shift drifts of proton and phosphorus GLY signals, thereby indicating the occurrence of weak interactions between GLY and humic superstructures. Binding was larger for FAs and pH 5.2 than for HAs and pH 7, thus suggesting formation of hydrogen bonds between GLY carboxyl and phosphonate groups and protonated oxygen functions in humic matter. Changes in relaxation and correlation times of (1)H and (31)P signals and saturation transfer difference NMR experiments confirmed the noncovalent nature of GLY-humic interactions. Diffusion-ordered NMR spectra allowed calculation of the glyphosate fraction bound to humic superstructures and association constants (K(a)) and Gibbs free energies of transfer for GLY-humic complex formation at both pH values. These values showed that noncovalent interactions occurred most effectively with FAs and at pH 5.2. Our findings indicated that glyphosate may spontaneously and significantly bind to soluble humic matter by noncovalent interactions at slightly acidic pH and, thus, potentially pollute natural water bodies by moving through soil profiles in complexes with dissolved humus. PMID:22591574

Mazzei, Pierluigi; Piccolo, Alessandro

2012-06-01

228

Unraveling the structure and function of G protein-coupled receptors through NMR spectroscopy  

PubMed Central

G protein-coupled receptors (GPCRs) are a large superfamily of signaling proteins expressed on the plasma membrane. They are involved in a wide range of physiological processes and, therefore, are exploited as drug targets in a multitude of therapeutic areas. In this extent, knowledge of structural and functional properties of GPCRs may greatly facilitate rational design of modulator compounds. Solution and solid-state nuclear magnetic resonance (NMR) spectroscopy represents a powerful method to gather atomistic insights into protein structure and dynamics. In spite of the difficulties inherent the solution of the structure of membrane proteins through NMR, these methods have been successfully applied, sometimes in combination with molecular modeling, to the determination of the structure of GPCR fragments, the mapping of receptor-ligand interactions, and the study of the conformational changes associated with the activation of the receptors. In this review, we provide a summary of the NMR contributions to the study of the structure and function of GPCRs, also in light of the published crystal structures.

Tikhonova, Irina G.; Costanzi, Stefano

2009-01-01

229

Interaction of the replication terminator protein of Bacillus subtilis with DNA probed by NMR spectroscopy.  

PubMed

Termination of DNA replication in Bacillus subtilis involves the polar arrest of replication forks by a specific complex formed between the dimeric 29 kDa replication terminator protein (RTP) and DNA terminator sites. We have used NMR spectroscopy to probe the changes in 1H-15N correlation spectra of a 15N-labelled RTP.C110S mutant upon the addition of a 21 base pair symmetrical DNA binding site. Assignment of the 1H-15N correlations was achieved using a suite of triple resonance NMR experiments with 15N,13C,70% 2H enriched protein recorded at 800 MHz and using TROSY pulse sequences. Perturbations to 1H-15N spectra revealed that the N-termini, alpha3-helices and several loops are affected by the binding interaction. An analysis of this data in light of the crystallographically determined apo- and DNA-bound forms of RTP.C110S revealed that the NMR spectral perturbations correlate more closely to protein structural changes upon complex formation rather than to interactions at the protein-DNA interface. PMID:16061201

Hastings, Adam F; Otting, Gottfried; Folmer, Rutger H A; Duggin, Iain G; Wake, R Gerry; Wilce, Matthew C J; Wilce, Jacqueline A

2005-09-23

230

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

USGS Publications Warehouse

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

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

1987-01-01

231

60 MHz 1H NMR spectroscopy for the analysis of edible oils?  

PubMed Central

We report the first results from a new 60 MHz 1H nuclear magnetic resonance (NMR) bench-top spectrometer, Pulsar, in a study simulating the adulteration of olive oil with hazelnut oil. There were qualitative differences between spectra from the two oil types. A single internal ratio of two isolated groups of peaks could detect hazelnut oil in olive oil at the level of ?13%w/w, whereas a whole-spectrum chemometric approach brought the limit of detection down to 11.2%w/w for a set of independent test samples. The Pulsar’s performance was compared to that of Fourier transform infrared (FTIR) spectroscopy. The Pulsar delivered comparable sensitivity and improved specificity, making it a superior screening tool. We also mapped NMR onto FTIR spectra using a correlation-matrix approach. Interpretation of this heat-map combined with the established annotations of the NMR spectra suggested a hitherto undocumented feature in the IR spectrum at ?1130 cm?1, attributable to a double-bond vibration.

Parker, T.; Limer, E.; Watson, A.D.; Defernez, M.; Williamson, D.; Kemsley, E. Kate

2014-01-01

232

Interaction of a goose-type lysozyme with chitin oligosaccharides as determined by NMR spectroscopy.  

PubMed

The interaction between a goose-type lysozyme from ostrich egg white (OEL) and chitin oligosaccharides [(GlcNAc)(n) (n = 2, 4 and 6)] was studied by nuclear magnetic resonance (NMR) spectroscopy. A stable isotope-labelled OEL was produced in Pichia pastoris, and backbone resonance assignments for the wild-type and an inactive mutant (E73A OEL) were achieved using modern multi-dimensional NMR techniques. NMR titration was performed with (GlcNAc)(n) for mapping the interaction sites of the individual oligosaccharides based on the shifts in the two-dimensional heteronuclear single quantum correlation (HSQC) resonances. In wild-type OEL, the interaction sites for (GlcNAc)(n) were basically similar to those determined by X-ray crystallography. In E73A OEL, however, the interaction sites were spread more widely over the substrate-binding cleft than expected, due to the multiple modes of binding. The association constant for E73A OEL and (GlcNAc)(6) calculated from the shifts in the Asp97 resonance (7.2 × 10(3) M(-1)) was comparable with that obtained by isothermal titration calorimetry (5.3 × 10(3) M(-1)). The interaction was enthalpy-driven as judged from the thermodynamic parameters (?H = -6.1 kcal/mol and T?S = -1.0 kcal/mol). This study provided novel insights into the oligosaccharide binding mechanism and the catalytic residues of the enzymes belonging to family GH-23. PMID:21859795

Shinya, Shoko; Ohnuma, Takayuki; Kawamura, Shunsuke; Torikata, Takao; Nishimura, Shigenori; Katoh, Etsuko; Fukamizo, Tamo

2011-11-01

233

Examining weak protein-protein interactions in start codon recognition via NMR spectroscopy.  

PubMed

Weak protein-protein interactions are critical in numerous biological processes. Unfortunately, they are difficult to characterize due to the high concentrations required for the production and detection of the complex population. The inherent sensitivity of NMR spectroscopy to the chemical environment makes it an excellent tool to tackle this problem. NMR permits the exploration of interactions over a range of affinities, yielding essential insights into dynamic biological processes. The conversion of messanger RNA to protein is one such process that requires the coordinated association of many low-affinity proteins. During start codon recognition, eukaryotic initiation factors assemble into high-order complexes that bind messanger RNA and bring it to the ribosome for decoding. Many of the structures of the eukaryotic initiation factors have been determined; however, little is known regarding the weak binary complexes formed and their structure-function mechanisms. Herein, we use start codon recognition as a model system to review the relevant NMR methods for the characterization of weak interactions and the development of small molecule inhibitors. PMID:24393460

Luna, Rafael E; Akabayov, Sabine R; Ziarek, Joshua J; Wagner, Gerhard

2014-04-01

234

Sensitivity and Resolution Enhancement in Solid-State NMR Spectroscopy of Bicelles  

PubMed Central

Magnetically aligned bicelles are becoming attractive model membranes to investigate the structure, dynamics, geometry, and interaction of membrane-associated peptides and proteins using solution- and solid-state NMR experiments. Recent studies have shown that bicelles are more suitable than mechanically aligned bilayers for multidimensional solid-state NMR experiments. In this work, we describe experimental aspects of the natural abundance 13C and 14N NMR spectroscopy of DMPC/DHPC bicelles. In particular, approaches to enhance the sensitivity and resolution and to quantify radio frequency heating effects are presented. Sensitivity of 13C detection using single pulse excitation, conventional cross-polarization (CP), ramp-CP, and NOE techniques are compared. Our results suggest that the proton decoupling efficiency of the FLOPSY pulse sequence is better than that of continuous wave decoupling, TPPM, SPINAL and WALTZ sequences. A simple method of monitoring the water proton chemical shift is demonstrated for the measurement of sample temperature and calibration of the radio-frequency-induced heating in the sample. The possibility of using 14N experiments on bicelles is also discussed.

Dvinskikh, Sergey V.; Yamamoto, Kazutoshi; Durr, Ulrich H. N.; Ramamoorthy, Ayyalusamy

2007-01-01

235

Metabolomic Characterization of Ovarian Epithelial Carcinomas by HRMAS-NMR Spectroscopy  

PubMed Central

Objectives. The objectives of the present study are to determine if a metabolomic study by HRMAS-NMR can (i) discriminate between different histological types of epithelial ovarian carcinomas and healthy ovarian tissue, (ii) generate statistical models capable of classifying borderline tumors and (iii) establish a potential relationship with patient's survival or response to chemotherapy. Methods. 36 human epithelial ovarian tumor biopsies and 3 healthy ovarian tissues were studied using 1H HRMAS NMR spectroscopy and multivariate statistical analysis. Results. The results presented in this study demonstrate that the three histological types of epithelial ovarian carcinomas present an effective metabolic pattern difference. Furthermore, a metabolic signature specific of serous (N-acetyl-aspartate) and mucinous (N-acetyl-lysine) carcinomas was found. The statistical models generated in this study are able to predict borderline tumors characterized by an intermediate metabolic pattern similar to the normal ovarian tissue. Finally and importantly, the statistical model of serous carcinomas provided good predictions of both patient's survival rates and the patient's response to chemotherapy. Conclusions. Despite the small number of samples used in this study, the results indicate that metabolomic analysis of intact tissues by HRMAS-NMR is a promising technique which might be applicable to the therapeutic management of patients.

Ben Sellem, D.; Elbayed, K.; Neuville, A.; Moussallieh, F.-M.; Lang-Averous, G.; Piotto, M.; Bellocq, J.-P.; Namer, I. J.

2011-01-01

236

Spectroscopy  

NSDL National Science Digital Library

This site describes the theory and practice of IR and NMR spectroscopy for classroom and laboratory instruction. Although it is written for a course at the University of Colorado, Boulder, this site is appropriate for anyone doing analytical measurements with infrared or NMR.

2011-08-05

237

Carnosine as molecular probe for sensitive detection of Cu(II) ions using localized 1H NMR spectroscopy  

Microsoft Academic Search

Complex formation of carnosine (Csn) with Cu(II) is suspected to be of significant biochemical importance and can be detected by NMR via ion-induced paramagnetic relaxation of Csn signals. Here, we present quantification of the sensitivity achieved with localized 1H NMR spectroscopy at physiological pH and high ligand-to-metal ratios. While characterizing the highly effective relaxation transfer onto a huge Csn pool

Leif Schröder; Christian H. J. Schmitz; Peter Bachert

2008-01-01

238

A simple method for determining protic end-groups of synthetic polymers by 1H NMR spectroscopy  

Microsoft Academic Search

A simple method for the determination of protic end-groups (–XH) in synthetic polymers involves in situ derivatization with trichloroacetyl isocyanate (TAI) in an NMR tube and observation of the imidic hydrogens of the derivatized products [–X–C(O)–NH–COCCl3] by 1H NMR spectroscopy. In this paper, we report that the method is effective for the quantitative determination of hydroxy, primary amino and carboxy

Almar Postma; Thomas P. Davis; A. Richard Donovan; Guoxin Li; Graeme Moad; Roger Mulder; Michael S. O'Shea

2006-01-01

239

Confirming the 3D Solution Structure of a Short Double-Stranded DNA Sequence Using NMR Spectroscopy  

ERIC Educational Resources Information Center

2D [superscript 1]H NOESY NMR spectroscopy is routinely used to give information on the closeness of hydrogen atoms through space. This work is based on a 2D [superscript 1]H NOESY NMR spectrum of a 12 base-pair DNA duplex. This 6-h laboratory workshop aims to provide advanced-level chemistry students with a basic, yet solid, understanding of how…

Ruhayel, Rasha A.; Berners-Price, Susan J.

2010-01-01

240

Multicomponent analysis of radiolytic products in human body fluids using high field proton nuclear magnetic resonance (NMR) spectroscopy  

Microsoft Academic Search

High field proton Hahn spin-echo nuclear magnetic resonance (NMR) spectroscopy has been employed to investigate radiolytic damage to biomolecules present in intact human body fluids. gamma-Radiolysis of healthy or rheumatoid human serum (5.00 kGy) in the presence of atmospheric O2 gave rise to reproducible elevations in the concentration of NMR-detectable acetate which are predominantly ascribable to the prior oxidation of

Martin C. Grootveld; Herman Herz; Rachel Haywood; Geoffrey E. Hawkes; Declan Naughton; Anusha Perera; Jacky Knappitt; David R. Blake; Andrew W. D. Claxson

1994-01-01

241

Solid-state 13C NMR spectroscopy studies of xylans in the cell wall of Palmaria palmata (L. Kuntze, Rhodophyta)  

Microsoft Academic Search

The chemical structure and interactions of the cell wall polysaccharides from the red edible seaweed Palmaria palmata were studied by liquid-like magic-angle-spinning (MAS) and cross-polarization MAS (CPMAS) solid-state 13C NMR spectroscopy. The liquid-like MAS and CPMAS 13C NMR spectra of the rehydrated algal powder revealed the presence of ?-(1?4)\\/?-(1?3)-linked d-xylan with chemical shifts close to those observed in the solution

Marc Lahaye; Corinne Rondeau-Mouro; Estelle Deniaud; Alain Buléon

2003-01-01

242

Studies on the MxiH protein in T3SS needles using DNP-enhanced ssNMR spectroscopy.  

PubMed

Bacterial T3SS needles formed by the protein MxiH are studied using DNP-enhanced ssNMR spectroscopy at 14.1 T (600 MHz). This technique provides spectra of good resolution, allowing us to draw conclusions about the protein dynamics. With the obtained signal enhancement, samples of limited quantity now get within reach of ssNMR studies. PMID:24282046

Fricke, Pascal; Demers, Jean-Philippe; Becker, Stefan; Lange, Adam

2014-01-13

243

Spectroscopy  

NSDL National Science Digital Library

This page is a set of concept test questions about organic chemistry spectroscopy. There are ten questions about topics including trans isomer and NMR spectra, C-X vibration, wavenumber absorption, and carbon signals.

2008-03-11

244

Postharvest ripening study of sweet lime (Citrus limettioides) in situ by volume-localized NMR spectroscopy.  

PubMed

Spatially resolved NMR--especially volume-localized spectroscopy (VLS)is useful in various fields including clinical diagnosis, process monitoring, etc. VLS carries high significance because of its ability to identify molecular species and hence track molecular events. This paper reports the application of VLS at 200 MHz to study the postharvest ripening of sweet lime ( Citrus limettioides ) in situ, including a comparative study of normal and acetylene-mediated ripening. Localization to a cubic voxel of 64 microL was achieved with point-resolved spectroscopy (PRESS). Glucose, sucrose, fructose, and citric acid are found to be among the main constituents in the fruit. In the natural process, the sugar to acid ratio increases with ripening. Ethanol generation is seen to occur at a faster rate in acetylene-mediated ripening. Whereas NMR imaging experiments including parametric imaging (e.g., T(1) or T(2) maps) may be employed for "macro" monitoring of processes such as these, this work demonstrates that the molecular imprint of the process may be tracked noninvasively by VLS. PMID:19161255

Banerjee, Abhishek; George, Christy; Bharathwaj, Sathyamoorthy; Chandrakumar, Narayanan

2009-02-25

245

Broad identification of bacterial type in urinary tract infection using (1)h NMR spectroscopy.  

PubMed

To address the shortcomings of urine culture for the rapid identification of urinary tract infection (UTI), we applied (1)H-nuclear magnetic resonance (NMR) spectroscopy as a surrogate method for fast screening of microorganisms. Study includes 682 urine samples from suspected UTI patients, 50 healthy volunteers, and commercially available standard strains of gram negative bacilli (GNB) (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Enterobacter, Acinetobacter, Proteus mirabilis, Citrobacter frundii) and gram positive cocci (GPC) (Enterococcus faecalis, Streptococcus group B, Staphylococcus saprophyticus). Acetate, lactate, ethanol, succinate, creatinine, trimethylamine (TMA), citrate, trimethylamin-N-oxide, glycine, urea, and hippurate were measured by (1)H NMR spectroscopy. All urine specimens were evaluated with culture method. Multivariate discriminant function analysis (DFA) reveals that acetate, lactate, succinate, and formate were able to differentiate, with high accuracy (99.5%), healthy controls from UTI patients. This statistical analysis was also able to classify GNB to GPC infected urine samples with high accuracy (96%). This technique appears to be a promising, rapid, and noninvasive approach to probing GNB and GPC infected urine specimens with its distinguishing metabolic profile. The determination of infection will be very important for rapidly and efficiently measuring the efficacy of a tailored treatment, leading to prompt and appropriate care of UTI patients. PMID:22292465

Gupta, Ashish; Dwivedi, Mayank; Mahdi, Abbas Ali; Khetrapal, Chunni Lal; Bhandari, Mahendra

2012-03-01

246

High-resolution two-dimensional j-resolved NMR spectroscopy for biological systems.  

PubMed

NMR spectroscopy is a principal tool in metabolomic studies and can, in theory, yield atom-level information critical for understanding biological systems. Nevertheless, NMR investigations on biological tissues generally have to contend with field inhomogeneities originating from variations in macroscopic magnetic susceptibility; these field inhomogeneities broaden spectral lines and thereby obscure metabolite signals. The congestion in one-dimensional NMR spectra of biological tissues often leads to ambiguities in metabolite identification and quantification. We propose an NMR approach based on intermolecular double-quantum coherences to recover high-resolution two-dimensional (2D) J-resolved spectra from inhomogeneous magnetic fields, such as those created by susceptibility variations in intact biological tissues. The proposed method makes it possible to acquire high-resolution 2D J-resolved spectra on intact biological samples without recourse to time-consuming shimming procedures or the use of specialized hardware, such as magic-angle-spinning probes. Separation of chemical shifts and J couplings along two distinct dimensions is achieved, which reduces spectral crowding and increases metabolite specificity. Moreover, the apparent J coupling constants observed are magnified by a factor of 3, facilitating the accurate measurement of small J couplings, which is useful in metabolic analyses. Dramatically improved spectral resolution is demonstrated in our applications of the technique on pig brain tissues. The resulting spectra contain a wealth of chemical shift and J-coupling information that is invaluable for metabolite analyses. A spatially localized experiment applied on an intact fish (Crossocheilus siamensis) reveals the promise of the proposed method in in vivo metabolite studies. Moreover, the proposed method makes few demands on spectrometer hardware and therefore constitutes a convenient and effective manner for metabonomics study of biological systems. PMID:24806938

Huang, Yuqing; Cai, Shuhui; Zhang, Zhiyong; Chen, Zhong

2014-05-01

247

Dissolution DNP-NMR spectroscopy using galvinoxyl as a polarizing agent  

PubMed Central

The goal of this work was to test feasibility of using galvinoxyl (2,6-di-tert-butyl-?-(3,5- di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene)-p-tolyloxy) as a polarizing agent for dissolution dynamic nuclear polarization (DNP) NMR spectroscopy. We have found that galvinoxyl is reasonably soluble in ethyl acetate, chloroform, or acetone and the solutions formed good glasses when mixed together or with other solvents such as dimethyl sulfoxide. W-band electron spin resonance (ESR) measurements revealed that galvinoxyl has an ESR linewidth D intermediate between that of carbon-centered free radical trityl OX063 and the nitroxide-based 4-oxo-TEMPO, thus the DNP with galvinoxyl for nuclei with low gyromagnetic ratio ? such as 13C and 15N is expected to proceed predominantly via the thermal mixing process. The optimum radical concentration that would afford the highest 13C nuclear polarization (approximately 6% for [1-13C]ethyl acetate) at 3.35 T and 1.4 K was found to be around 40 mM. After dissolution, large liquid-state NMR enhancements were achieved for a number of 13C and 15N compounds with long spin-lattice relaxation time T1. In addition, the hydrophobic galvinoxyl free radical can be easily filtered out from the dissolution liquid when water is used as the solvent. These results indicate that galvinoxyl can be considered as an easily available free radical polarizing agent for routine dissolution DNP-NMR spectroscopy.

Lumata, Lloyd L.; Merritt, Matthew E.; Malloy, Craig R.; Sherry, A. Dean; van Tol, Johan; Song, Likai; Kovacs, Zoltan

2012-01-01

248

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

249

The effect of polysialic acid on molecular dynamics of model membranes studied by 31P NMR spectroscopy.  

PubMed

The paper reports the results of our study on the dynamics of model phospholipid membranes studied by 31P NMR spectroscopy. The 31P NMR spectra of multilamellar vesicles in temperatures below the main phase transition of PC are reported. The 31P NMR spectra revealed changes caused by an increase of the membrane fluidity when polysialic acid (polySia) was applied as a modifying agent. The presence of polySia in the external environment of the phospholipid vesicles changes the motional freedom in the region of phosphate group of lipids. Increase of polysialic acid concentration changes structural properties of a membrane by increasing its fluidity. PMID:14698401

Timoszyk, Anna; Gdaniec, Zofia; Latanowicz, Lidia

2004-01-01

250

Single-Crystalline cooperite (PtS): Crystal-Chemical characterization, ESR spectroscopy, and {sup 195}Pt NMR spectroscopy  

SciTech Connect

Single-crystalline cooperite (PtS) with a nearly stoichiometric composition was characterized in detail by X-ray diffraction, electron-probe X-ray microanalysis, and high-resolution scanning electron microscopy. For the first time it was demonstrated that {sup 195}Pt static and MAS NMR spectroscopy can be used for studying natural platinum minerals. The {sup 195}Pt chemical-shift tensor of cooperite was found to be consistent with the axial symmetry and is characterized by the following principal values: {delta}{sub xx} = -5920 ppm, {delta}{sub yy} = -3734 ppm, {delta}{sub zz} = +4023 ppm, and {delta}{sub iso} = -1850 ppm. According to the ESR data, the samples of cooperite contain copper(II), which is adsorbed on the surface during the layer-by-layer crystal growth and is not involved in the crystal lattice.

Rozhdestvina, V. I., E-mail: veronika@ascnet.ru; Ivanov, A. V.; Zaremba, M. A. [Far East Division, Russian Academy of Sciences, Institute of Geology and Nature Management (Russian Federation); Antsutkin, O. N.; Forsling, W. [Lulea University of Technology (Sweden)

2008-05-15

251

Application of 29Si NMR spectroscopy to study of alkaline aqueous and alcoholic tetraoctylammonium (TOA) silicate solutions  

NASA Astrophysics Data System (ADS)

29Si NMR spectroscopy is a powerful tool for studying the silicate species existing in aqueous and non-aqueous solutions. In the present work, 29Si NMR spectroscopy is used to characterize the species present in alkaline alcoholic solutions of silicates. Tetraoctylammonium (TOA) hydroxide is used as a template. The effects of polymerization/depolymerization of silicate anions on alkaline alcoholic solutions are investigated using different alcohols (methanol, 1-propanol, 1,3-propane-diol, and glycerin) by 29Si NMR spectroscopy. The esterification of monomeric silicate, Si(OH) 4, in the presence of different alcohols is also studied. Esterification of Si(OH) 4 depends on the alkyl chain as well as the number of hydroxyl groups present in the alcohol.

Goudarzi, Nasser; Arab Chamjangali, M.; Bagherian, G.

2010-10-01

252

Probing RNA dynamics via longitudinal exchange and CPMG relaxation dispersion NMR spectroscopy using a sensitive 13C-methyl label  

PubMed Central

The refolding kinetics of bistable RNA sequences were studied in unperturbed equilibrium via 13C exchange NMR spectroscopy. For this purpose a straightforward labeling technique was elaborated using a 2?-13C-methoxy uridine modification, which was prepared by a two-step synthesis and introduced into RNA using standard protocols. Using 13C longitudinal exchange NMR spectroscopy the refolding kinetics of a 20?nt bistable RNA were characterized at temperatures between 298 and 310?K, yielding the enthalpy and entropy differences between the conformers at equilibrium and the activation energy of the refolding process. The kinetics of a more stable 32?nt bistable RNA could be analyzed by the same approach at elevated temperatures, i.e. at 314 and 316?K. Finally, the dynamics of a multi-stable RNA able to fold into two hairpin- and a pseudo-knotted conformation was studied by 13C relaxation dispersion NMR spectroscopy.

Kloiber, Karin; Spitzer, Romana; Tollinger, Martin; Konrat, Robert; Kreutz, Christoph

2011-01-01

253

Synthesis and Resolution of the Atropisomeric 1,1'-Bi-2-Naphthol: An Experiment in Organic Synthesis and 2-D NMR Spectroscopy  

ERIC Educational Resources Information Center

NMR spectroscopy is presented. It is seen that the experiment regarding the synthesis and resolution of 1,1'-Bi-2-naphtol presents a good experiment for teaching organic synthesis and NMR spectroscopy and provides a strategy for obtaining enantiopure compounds from achiral starting materials.

Mak, Kendrew K. W.

2004-01-01

254

Elucidation of meso- and microporosity in soil components with 129-Xe NMR spectroscopy of adsorbed xenon  

NASA Astrophysics Data System (ADS)

Soil meso- and micropores (2-50 nm and <2 nm) are usually studied with the use of common adsorption methods. As a complementary technique, 129-Xe NMR spectroscopy of adsorbed xenon was only recently suggested for the use in soil science. In this present study, we applied both conventional, i.e. thermally polarised (TP), and hyperpolarised (HP) 129-Xe NMR for elucidating pore environments of a series of samples representing porous soil constituents. Aluminium (hydr)oxides, Al2O3 and AlOOH, both pure and subjected to the sorption of dissolved organic matter (DOM) were chosen as model mineral systems. Charcoals were used for understanding adsorption behaviour of xenon within organic polymeric structures formed by thermally altered bio-macromolecules. Natural soil particle size fractions were obtained from a non-allophanic Andosol and from Arenosol, i.e. soils containing charred residues and also characterised by a high content of Al oxides (case of the Andosol). DOM sorption on the studied Al oxides occurred inhomogeneously as it was inferred from the existence of the "empty" pores and the pores coated with OM. The latter were evidenced by the different Xe adsorption enthalpies estimated from the temperature dependences of the chemical shift. The increased sensitivity of the HP 129-Xe NMR allowed us detecting micropores in the charcoals, where the N2 adsorption method underestimated porosity due to the restricted diffusion of N2 at 77 K. The observed differences between the HP and TP 129-Xe patterns were explained by the slow diffusion of xenon within an interconnected but highly constricted pore system of the charcoals. The estimated width of those constricted pore openings was of the order of one or two diameters of the Xe atom. Similar "bottle neck" effects may also exist in the natural soil particle size fractions, as it was inferred from the increased pore access for Xe adsorption performed at elevated pressures (2-4 bar). The unusually large 129-Xe shifts (up to 170 ppm) detected for the for the H2O2-treated clay fractions of the Andosol (Bw horizon) coincided with their large specific surface areas(up to 220 m2/g) and were attributed to the pores formed by agglomerates of the nano-sized Al - humus complexes with contribution from the charred residues. Micropores found in the Arenosol fractions were attributed to the charred residues. Briefly, 129-Xe NMR spectroscopy shows its potential for studying soil meso- and micropores due to: i) higher sensitivity for probing micropores within polymeric organic structures, e.g. charcoals, as compared to the N2 adsorption; ii) possibility to use elevated pressures of the adsorbate for increasing the pore accessibility; iii) evaluating not only the pore size range but also adsorption enthalpies that reflect the nature of Xe - pore surface interactions. On the other hand, a combination of the HP- and TP 129-Xe NMR was shown to be helpful for modelling the pore structures of solids, since relaxation phenomena determining appearance of the HP 129-Xe NMR patterns also relate to the pore attainability.

Filimonova, Svetlana; Nossov, Andrey; Knicker, Heike; Kögel-Knabner, Ingrid

2010-05-01

255

Organic solute changes with acidification in Lake Skjervatjern as shown by 1H-NMR spectroscopy  

USGS Publications Warehouse

1H-NMR spectroscopy has been found to be a useful tool to establish possible real differences and trends between all natural organic solute fractions (fulvic acids, humic acids, and XAD-4 acids) after acid-rain additions to the Lake Skjervatjern watershed. The proton NMR technique used in this study determined the spectral distribution of nonexchangeable protons among four peaks (aliphatic protons; aliphatic protons on carbon ?? or attached to electronegative groups; protons on carbons attached to O or N heteroatoms; and aromatic protons). Differences of 10% or more in the respective peak areas were considered to represent a real difference. After one year of acidification, fulvic acids decreased 13% (relative) in Peak 3 protons on carbon attached to N and O heteratoms and exhibited a decrease in aromatic protons between 27% and 31%. Humic acids also exhibited an 11% relative decrease in aromatic protons as a result of acidification. After one year of acidification, real changes were shown in three of the four proton assignments in XAD-4 acids. Peak 1 aliphatic protons increased by 14% (relative), Peak 3 protons on carbons attached to O and N heteroatoms decreased by 13% (relative), and aromatic protons (Peak 4) decreased by 35% (relative). Upon acidification, there was a trend in all solutes for aromatic protons to decrease and aliphatic protons to increase. The natural variation in organic solutes as shown in the Control Side B of the lake from 1990 to 1991 is perhaps a small limitation to the same data interpretations of acid rain changes at the Lake Skjervatjern site, but the proton NMR technique shows great promise as an independent scientific tool to detect and support other chemical techniques in establishing organic solute changes with different treatments (i.e., additions of acid rain).

Malcolm, R. L.; Hayes, T.

1994-01-01

256

Characterization of filter extractables by proton NMR spectroscopy: studies on intact filters with process buffers.  

PubMed

Studies were conducted to characterize potential extractables from sterilizing grade filters. The focus of this report is the 0.22 micron Durapore (hydrophilic modified PVDF) filter which is used throughout our recovery processes. The objectives of this study are (1) to identify potential filter extractables from the hydrophilic PVDF filters; (2) to show that NMR spectroscopy may be used to detect filter extractables in the presence of product and excipients; and (3) to establish levels of filter extractables obtained by extraction with a variety of buffers. The data show that the primary source of filter extractables is the hydrophilic modification of the PVDF membrane surface. Extractables from the modified hydrophilic PVDF filter include propylene glycol (PG) and soluble oligomers of the hydroxypropyl acrylate and cross-linker. Propylene glycol, arising from the hydrolysis of the hydroxypropyl acrylate, appears to be the primary extractable in buffers above pH 11. Since the 1H-NMR method can easily detect the methyl proton signals of PG, an NMR assay was developed to detect PG in the presence of buffer excipients and final product. Propylene glycol can be used as a marker for the extractables from Durapore hydrophilic PVDF filters. Although numerous buffers were used to generate extractables from the PVDF filter, significant extractables (PG and soluble oligomers) were found only in high pH extraction buffers. As a result of this finding, only a limited number of new buffers or new PVDF filters will require testing for future validation studies. Process validation studies have shown that neither PG nor soluble oligomers are at levels that impact the quality or safety of the product. PMID:11605250

Kao, Y H; Bender, J; Hagewiesche, A; Wong, P; Huang, Y; Vanderlaan, M

2001-01-01

257

Optimization of designed armadillo repeat proteins by molecular dynamics simulations and NMR spectroscopy  

PubMed Central

A multidisciplinary approach based on molecular dynamics (MD) simulations using homology models, NMR spectroscopy, and a variety of biophysical techniques was used to efficiently improve the thermodynamic stability of armadillo repeat proteins (ArmRPs). ArmRPs can form the basis of modular peptide recognition and the ArmRP version on which synthetic libraries are based must be as stable as possible. The 42-residue internal Arm repeats had been designed previously using a sequence-consensus method. Heteronuclear NMR revealed unfavorable interactions present at neutral but absent at high pH. Two lysines per repeat were involved in repulsive interactions, and stability was increased by mutating both to glutamine. Five point mutations in the capping repeats were suggested by the analysis of positional fluctuations and configurational entropy along multiple MD simulations. The most stabilizing single C-cap mutation Q240L was inferred from explicit solvent MD simulations, in which water penetrated the ArmRP. All mutants were characterized by temperature- and denaturant-unfolding studies and the improved mutants were established as monomeric species with cooperative folding and increased stability against heat and denaturant. Importantly, the mutations tested resulted in a cumulative decrease of flexibility of the folded state in silico and a cumulative increase of thermodynamic stability in vitro. The final construct has a melting temperature of about 85°C, 14.5° higher than the starting sequence. This work indicates that in silico studies in combination with heteronuclear NMR and other biophysical tools may provide a basis for successfully selecting mutations that rapidly improve biophysical properties of the target proteins.

Alfarano, Pietro; Varadamsetty, Gautham; Ewald, Christina; Parmeggiani, Fabio; Pellarin, Riccardo; Zerbe, Oliver; Pluckthun, Andreas; Caflisch, Amedeo

2012-01-01

258

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

259

Impurity profiling of carbocisteine by HPLC-CAD, qNMR and UV/vis spectroscopy.  

PubMed

For the impurity profiling of the mucolytic and anti-inflammatory drug carbocisteine a high performance liquid chromatographic (HPLC) method using corona charged aerosol detection (CAD) was developed and fully validated following the ICH guideline Q2(R1). The response was linear (R(2)>0.995) over a small concentration range (0.05-0.25 or 0.10-0.60% respectively) and a detection limit of at least 0.03% was registered. The separation was achieved on a mixed mode column combining hydrophobic C18 and strong cation exchange retention mechanisms using a mass spectrometer compatible volatile mobile phase consisting of trifluoroacetic acid 10mM and acetonitrile 12% (V/V). Impurities, not assessable by HPLC-CAD such as the volatile chloroacetic acid and the unstable cysteine, were determined by quantitative NMR (qNMR) with maleic acid as internal standard and UV/vis spectroscopy after reaction with Ellman's reagent, respectively. Six batches of three different manufacturers were tested by means of those methods. The purity varied from below 99.0 to higher than 99.8 per cent. The major impurities of all batches were the starting material cystine and N,S-dicarboxymethylcysteine being a synthesis by-product. PMID:24637049

Wahl, Oliver; Holzgrabe, Ulrike

2014-07-01

260

Time-domain Bayesian detection and estimation of noisy damped sinusoidal signals applied to NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The problem of model detection and parameter estimation for noisy signals arises in different areas of science and engineering including audio processing, seismology, electrical engineering, and NMR spectroscopy. We have adopted the Bayesian modeling framework to jointly detect and estimate signal resonances. This considers a model of the time-domain complex free induction decay (FID) signal as a sum of exponentially damped sinusoidal components. The number of model components and component parameters are considered unknown random variables to be estimated. A Reversible Jump Markov Chain Monte Carlo technique is used to draw samples from the joint posterior distribution on the subspaces of different dimensions. The proposed algorithm has been tested on synthetic data, the 1H NMR FID of a standard of L-glutamic acid and a blood plasma sample. The detection and estimation performance is compared with Akaike information criterion (AIC), minimum description length (MDL) and the matrix pencil method. The results show the Bayesian algorithm superior in performance especially in difficult cases of detecting low-amplitude and strongly overlapping resonances in noisy signals.

Rubtsov, Denis V.; Griffin, Julian L.

2007-10-01

261

Microstructure determination of 2-hydroxy ethyl methacrylate and methyl acrylate copolymers by NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Copolymers of 2-Hydroxy ethyl methacrylate and methyl acrylate (H/M) of different compositions were synthesized by free radical bulk polymerization using azobisisobutyronitrile (AIBN) as an initiator under nitrogen atmosphere. The copolymers compositions were calculated from 1H NMR spectra. The reactivity ratios for H/M copolymers obtained from a linear Kelen-Tudos method (KT) and nonlinear error-in-variables method (EVM) are rH = 3.31 ą 0.08, rM = 0.23 ą 0.00 and rH = 3.32, rM = 0.23, respectively. The complete spectral assignment of methine, methylene, methyl and carbonyl carbon regions in terms of compositional and configurational sequences of H/M copolymers was done with the help of 13C{ 1H} NMR, distortionless enhancement by polarization transfer (DEPT), two-dimensional heteronuclear single quantum coherence (HSQC) along with total correlated spectroscopy (TOCSY). Further, the assignments of carbonyl region were made with the help of heteronuclear multiple bond coherence (HMBC) spectrum.

Brar, A. S.; Hooda, Sunita; Goyal, Ashok Kumar

2007-02-01

262

Relaxation Dispersion NMR Spectroscopy as a Tool for Detailed Studies of Protein Folding  

PubMed Central

Characterization of the mechanisms by which proteins fold into their native conformations is important not only for protein structure prediction and design but also because protein misfolding intermediates may play critical roles in fibril formation that are commonplace in neurodegenerative disorders. In practice, the study of folding pathways is complicated by the fact that for the most part intermediates are low-populated and short-lived so that biophysical studies are difficult. Due to recent methodological advances, relaxation dispersion NMR spectroscopy has emerged as a particularly powerful tool to obtain high-resolution structural information about protein folding events on the millisecond timescale. Applications of the methodology to study the folding of SH3 domains have shown that folding proceeds via previously undetected on-pathway intermediates, sometimes stabilized by nonnative long-range interactions. The relaxation dispersion approach provides a detailed kinetic and thermodynamic description of the folding process as well as the promise of obtaining an atomic level structural description of intermediate states. We review the concerted application of a variety of recently developed NMR relaxation dispersion experiments to obtain a “high-resolution” picture of the folding pathway of the A39V/N53P/V55L Fyn SH3 domain.

Neudecker, Philipp; Lundstrom, Patrik; Kay, Lewis E.

2009-01-01

263

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

USGS Publications Warehouse

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

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

1989-01-01

264

The dynamic complex of cytochrome c6 and cytochrome f studied with paramagnetic NMR spectroscopy.  

PubMed

The rapid transfer of electrons in the photosynthetic redox chain is achieved by the formation of short-lived complexes of cytochrome b6f with the electron transfer proteins plastocyanin and cytochrome c6. A balance must exist between fast intermolecular electron transfer and rapid dissociation, which requires the formation of a complex that has limited specificity. The interaction of the soluble fragment of cytochrome f and cytochrome c6 from the cyanobacterium Nostoc sp. PCC 7119 was studied using NMR spectroscopy and X-ray diffraction. The crystal structures of wild type, M58H and M58C cytochrome c6 were determined. The M58C variant is an excellent low potential mimic of the wild type protein and was used in chemical shift perturbation and paramagnetic relaxation NMR experiments to characterize the complex with cytochrome f. The interaction is highly dynamic and can be described as a pure encounter complex, with no dominant stereospecific complex. Ensemble docking calculations and Monte-Carlo simulations suggest a model in which charge-charge interactions pre-orient cytochrome c6 with its haem edge toward cytochrome f to form an ensemble of orientations with extensive contacts between the hydrophobic patches on both cytochromes, bringing the two haem groups sufficiently close to allow for rapid electron transfer. This model of complex formation allows for a gradual increase and decrease of the hydrophobic interactions during association and dissociation, thus avoiding a high transition state barrier that would slow down the dissociation process. PMID:24685428

Díaz-Moreno, Irene; Hulsker, Rinske; Skubak, Pavol; Foerster, Johannes M; Cavazzini, Davide; Finiguerra, Michelina G; Díaz-Quintana, Antonio; Moreno-Beltrán, Blas; Rossi, Gian-Luigi; Ullmann, G Matthias; Pannu, Navraj S; De la Rosa, Miguel A; Ubbink, Marcellus

2014-08-01

265

XRD, TEM, IR, Raman and NMR Spectroscopy of In Situ Crystallization of Lithium Disilicate Glass  

NASA Technical Reports Server (NTRS)

The structure of a Li2O-2SiO2 (LS2) glass was investigated as a function of pressure and temperature up to 6 GPa and 750 C respectively, using XRD, TEM, IR, Raman and NMR spectroscopy. Glass densified at 6 GPa has an average Si-O-Si bond angle approx.7deg lower than that found in glass processed at 4.5 GPa. At 4.5 GPa, lithium disilicate crystallizes from the glass, while at 6 GPa a new high pressure form of lithium metasilicate crystallizes. The new phase, while having lithium metasilicate crystal symmetry, contains at least 4 different Si sites. NMR results for 6 GPa sample indicate the presence of Q4 species with (Q(sup 4))Si-O-Si(Q(sup 4)) bond angles of approx.157deg. This is the first reported occurrence of Q(sup 4) species with such large bond angles in alumina free alkali silicate glass. No five- or six- coordinated Si are found.

Fuss, T.; Mogus-Milankovic, A.; Ray, C. S.; Lesher, C. E.; Youngman, R.; Day, D. E.

2006-01-01

266

?z/?: A transverse relaxation optimized spectroscopy NMR experiment measuring longitudinal relaxation interference  

NASA Astrophysics Data System (ADS)

NMR spin relaxation experiments provide a powerful tool for the measurement of global and local biomolecular rotational dynamics at subnanosecond time scales. Technical limitations restrict most spin relaxation studies to biomolecules weighing less than 10 kDa, considerably smaller than the average protein molecular weight of 30 kDa. In particular, experiments measuring ?z, the longitudinal 1HN-15N dipole-dipole (DD)/15N chemical shift anisotropy (CSA) cross-correlated relaxation rate, are among those least suitable for use with larger biosystems. This is unfortunate because these experiments yield valuable insight into the variability of the 15N CSA tensor over the polypeptide backbone, and this knowledge is critical to the correct interpretation of most 15N-NMR backbone relaxation experiments, including R2 and R1. In order to remedy this situation, we present a new 1HN-15N transverse relaxation optimized spectroscopy experiment measuring ?z suitable for applications with larger proteins (up to at least 30 kDa). The presented experiment also yields ?, the site-specific rate of longitudinal 1HN-1H' DD cross relaxation. We describe the ?z/? experiment's performance in protonated human ubiquitin at 30.0 °C and in protonated calcium-saturated calmodulin/peptide complex at 20.0 °C, and demonstrate preliminary experimental results for a deuterated E. coli DnaK ATPase domain construct at 34 °C.

Weaver, Daniel S.; Zuiderweg, Erik R. P.

2008-04-01

267

1,3-Alternate calix[4]arene nitronyl nitroxide tetraradical and diradical: synthesis, X-ray crystallography, paramagnetic NMR spectroscopy, EPR spectroscopy, and magnetic studies  

PubMed Central

Calix[4]arenes constrained to 1,3-alternate conformation and functionalized at the upper rim with four and two nitronyl nitroxides have been synthesized, and characterized by X-ray crystallography, magnetic resonance (EPR and 1H NMR) spectroscopy, and magnetic studies. Such calix[4]arene tetraradicals and diradicals provide scaffolds for through-bond and through-space intramolecular exchange couplings.

Rajca, Andrzej; Pink, Maren; Mukherjee, Sumit; Rajca, Suchada; Das, Kausik

2009-01-01

268

Coupled effect of salt and pH on proteins probed with NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The coupled effect of ionic strength (50-400 mM) and pH (2-8) on ionization and conformation equilibria of lysozyme was studied using NMR spectroscopy. Observed changes in pKa values of the ionizable groups were found to originate from perturbations in the geometry of hydrogen bonds rather than screening of electric fields. Moreover, at the ionic strengths used here, salt-induced local conformational changes had a dominant effect on chemical shifts measured on 1HN and 15N amide nuclei. Accurate modeling of these localized perturbations in structure-based energy calculations is a necessary prerequisite on the way to complete understanding of any salt-induced processes in proteins.

Kukic, Predrag; O'Meara, Fergal; Hewage, Chandralal; Erik Nielsen, Jens

2013-07-01

269

Response of melanoma tumor phospholipid metabolism to chloroethyle nitrosourea: a high resolution proton NMR spectroscopy study.  

PubMed

Phospholipid metabolism is tightly involved in tumor growth regulation and tumor cell survival. The response of phospholipid metabolism to chloroethyle nitrosourea treatment is investigated in a murine B16 melanoma model. Measurements of phospholipid derivatives are performed on intact tumor tissue samples using one- and two-dimensional proton NMR spectroscopy. During the tumor growth inhibition phase under treatment, tumors overexpress phosphocholine, phosphoethanolamine, glycerophosphocholine and glycerophosphoethanolamine, whereas phosphatidylcholine and phosphatidylethanolamine levels are maintained to control levels. During re-growth, which remained quantitatively much below control growth, chloroethyle nitrosourea-treated melanoma tumors overexpress phosphocholine and phosphoethanolamine only. In treated melanoma, phosphatidylcholine levels show an inverse relationship with tumor growth rates. In conclusion, chloroethyle nitrosourea-treated melanoma tumors maintain their phosphatidylcholine levels and exhibit transformed phospholipid metabolism phenotype, by mechanisms that could participate in tumor cell survival. PMID:14567189

Morvan, Daniel; Demidem, Aďcha; Madelmont, Jean-Claude

2003-07-01

270

Stereostructure of luminamicin, an anaerobic antibiotic, via molecular dynamics, NMR spectroscopy, and the modified Mosher method.  

PubMed

The absolute stereostructure of luminamicin, an anaerobic antibiotic, has been determined by using conformational analysis via high-temperature molecular dynamics, NMR spectroscopy, and the modified Mosher method. It was found that luminamicin has the S, S, R, R, R, R, S, S, S, R, and S configurations at C2, C4, C7, C9, C10, C11, C12, C13, C16, C28, and C29, respectively. This configuration is the same as that found in nodusmicin, which has a chemical structure quite similar to luminamicin. The structure of luminamicin consists of three different rings, i.e., a decalin ring, a 10-membered macrolactone ring, and a 14-membered macrolactone ring. The resulting three-dimensional structure of luminamicin shows an interesting feature in that the maleic anhydride functionality in conjugation with the enol ether group of the 14-membered macrolactone is nearly perpendicular to the plane of the other two rings. PMID:16344486

Gouda, Hiroaki; Sunazuka, Toshiaki; Ui, Hideaki; Handa, Masaki; Sakoh, Yusuke; Iwai, Yuzuru; Hirono, Shuichi; Omura, Satoshi

2005-12-20

271

Stereostructure of luminamicin, an anaerobic antibiotic, via molecular dynamics, NMR spectroscopy, and the modified Mosher method  

PubMed Central

The absolute stereostructure of luminamicin, an anaerobic antibiotic, has been determined by using conformational analysis via high-temperature molecular dynamics, NMR spectroscopy, and the modified Mosher method. It was found that luminamicin has the S, S, R, R, R, R, S, S, S, R, and S configurations at C2, C4, C7, C9, C10, C11, C12, C13, C16, C28, and C29, respectively. This configuration is the same as that found in nodusmicin, which has a chemical structure quite similar to luminamicin. The structure of luminamicin consists of three different rings, i.e., a decalin ring, a 10-membered macrolactone ring, and a 14-membered macrolactone ring. The resulting three-dimensional structure of luminamicin shows an interesting feature in that the maleic anhydride functionality in conjugation with the enol ether group of the 14-membered macrolactone is nearly perpendicular to the plane of the other two rings.

Gouda, Hiroaki; Sunazuka, Toshiaki; Ui, Hideaki; Handa, Masaki; Sakoh, Yusuke; Iwai, Yuzuru; Hirono, Shuichi; Omura, Satoshi

2005-01-01

272

Solid-state NMR spectroscopy provides atomic-level insights into the dehydration of cartilage.  

PubMed

An atomic-level insight into the functioning of articular cartilage would be useful to develop prevention strategies and therapies for joint diseases such as osteoarthritis. However, the composition and structure of cartilage and their relationship to its unique mechanical properties are quite complex and pose tremendous challenges to most biophysical techniques. In this study, we present an investigation of the structure and dynamics of polymeric molecules of articular cartilage using time-resolved solid-state NMR spectroscopy during dehydration. Full-thickness cartilage explants were used in magic-angle spinning experiments to monitor the structural changes of rigid and mobile carbons. Our results reveal that the dehydration reduced the mobility of collagen amino acid residues and carbon sugar ring structures in glycosaminoglycans but had no effect on the trans-Xaa-Pro conformation. Equally interestingly, our results demonstrate that the dehydration effects are reversible, and the molecular structure and mobility are restored upon rehydration. PMID:21786810

Xu, Jiadi; Zhu, Peizhi; Morris, Michael D; Ramamoorthy, Ayyalusamy

2011-08-25

273

Solid-State NMR Spectroscopy Provides Atomic-level Insights Into the Dehydration of Cartilage  

PubMed Central

An atomic-level insight into the functioning of articular cartilage would be useful to develop prevention strategies and therapies for joint diseases such as osteoarthritis. However, the composition and structure of cartilage, and their relationship to its unique mechanical properties are quite complex and pose tremendous challenges to most biophysical techniques. In this study, we present an investigation of the structure and dynamics of polymeric molecules of articular cartilage using time-resolved solid-state NMR spectroscopy during dehydration. Full-thickness cartilage explants were used in magic-angle spinning experiments to monitor the structural changes of rigid and mobile carbons. Our results reveal that the dehydration reduced the mobility of collagen amino acid residues and carbon sugar ring structures in glycosaminoglycans but had no effect on the trans-Xaa-Pro conformation. Equally interestingly, our results demonstrate that the dehydration effects are reversible, and the molecular structure and mobility are restored upon rehydration.

Xu, Jiadi; Zhu, Peizhi; Morris, Michael D.; Ramamoorthy, Ayyalusamy

2011-01-01

274

Crystallization of the Bacillus subtilis RTP-DNA complex prepared using NMR spectroscopy.  

PubMed

The replication terminator protein (RTP)-DNA complex of Bacillus subtilis is responsible for the arrest of DNA replication at terminator sites in the B. subtilis chromosome. The crystallization and preliminary diffraction data analysis for the complex of an (15)N-labelled mutant form of RTP and a symmetrical form of its DNA-binding site is reported. NMR spectroscopy was used to assess the stoichiometry of complex formation, with the sample containing the most homogeneous solution of complex giving rise to diffracting crystals. Synchrotron-radiation data to 2.5 A were collected from a crystal of space group P3(2)21, unit-cell parameters a = b = 44.780, c = 395.582 A, containing an RTP dimer within the asymmetric unit. PMID:11223520

Vivian, J P; Wilce, J A; Hastings, A F; Wilce, M C

2001-03-01

275

Reverse micelles in integral membrane protein structural biology by solution NMR spectroscopy  

PubMed Central

SUMMARY Integral membrane proteins remain a significant challenge to structural studies by solution NMR spectroscopy. This is due not only to spectral complexity but also because the effects of slow molecular reorientation are exacerbated by the need to solublize the protein in aqueous detergent micelles. These assemblies can be quite large and require deuteration for use of the TROSY effect. In principle, another approach is to employ reverse micelle encapsulation to solublize the protein in a low viscosity solvent where the rapid tumbling of the resulting particle allows use of standard triple resonance methods. The preparation of such samples of membrane proteins is difficult. Using a 54 kDa construct of the homotetrameric potassium channel KcsA we demonstrate a strategy that employs a hybrid surfactant to transfer the protein to the reverse micelle system.

Kielec, Joseph M.; Valentine, Kathleen G.; Babu, Charles R.; Wand, A. Joshua

2009-01-01

276

Narrowing of the exciton lines using WAHUHA method of solid state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

A method for allocating of two thermodynamic reservoirs which are not related to each other in high density exciton gas in semiconductors using the Schwinger representation for the projection operators of the effective spin (pseudospin) of the excitons is proposed. It is shown that the method of narrowing the NMR resonance lines in solids under the influence of a sequence of four electromagnetic pulses of the WAHUHA type can be applied for the line narrowing of the recombination emission and absorption of light by excitons in optical spectroscopy. We found out that, in contrast to the averaging to zero of the magnetic dipole-dipole interaction between nuclei, the exciton-exciton interaction is averaged only partially. This analysis for the excitons can be extended to other quasiparticles of boson type, i.e. biexcitons, polaritons and magnons, in solids.

Geru, I. I.

2011-10-01

277

Single-Quantum Coherence Filter for Strongly Coupled Spin Systems for Localized 1H NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

A pulse sequence for localized in vivo1H NMR spectroscopy is presented, which selectively filters single-quantum coherence built up by strongly coupled spin systems. Uncoupled and weakly coupled spin systems do not contribute to the signal output. Analytical calculations using a product operator description of the strongly coupled AB spin system as well as in vitro tests demonstrate that the proposed filter produces a signal output for a strongly coupled AB spin system, whereas the resonances of a weakly coupled AX spin system and of uncoupled spins are widely suppressed. As a potential application, the detection of the strongly coupled AA'BB' spin system of taurine at 1.5 T is discussed.

Trabesinger, Andreas H.; Mueller, D. Christoph; Boesiger, Peter

2000-08-01

278

Molecular dynamics of ethylene glycol adsorbed in NaX: NMR and broadband dielectric spectroscopy studies  

NASA Astrophysics Data System (ADS)

Proton spin relaxation and broadband dielectric spectroscopy are applied to study the dynamics of ethylene glycol adsorbed in NaX, EG/NaX. The molecular mobility strongly depends on the pore filling factor which may be controlled by high-resolution 1H MAS NMR measurements. Although EG in bulk shows a Vogel-Fulcher-Tammann type of activation, temperature dependent relaxation rate measurements for the EG/NaX systems always follow an Arrhenius plot, independent of the loading degree. There is no hint to a glass-forming behaviour of EG/NaX which could be understood in terms of the strong influence of surface-molecule interactions playing a dominant role compared to the molecule-molecule interactions.

Erdem, Özlen F.; Michel, Dieter

2006-02-01

279

Quantitative determination of glyphosate in human serum by 1H NMR spectroscopy.  

PubMed

The determination and quantification of glyphosate in serum using (1)H NMR spectroscopy is reported. This method permitted serum samples to be analysed without derivatization or any other sample pre-treatment, using 3-trimethylsilyl 2,2',3,3'-tetradeuteropropionic acid (TSP-d(4)) as a qualitative and quantitative standard. Characterization of the herbicide N-(phosphonomethyl)glycine was performed by analysing chemical shifts and coupling constant patterns. Quantification was performed by relative integration of CH(2)-P protons to the TSP-d(4) resonance peak. The method was tested for repeatability (n=5) and yielded coefficients of variation of 1% and 3%, respectively: detection and quantification limits were also determined and were 0.03 and 0.1mmol/L, respectively. The method was applied to the quantification of glyphosate in a case of acute poisoning. PMID:18371753

Cartigny, Bernard; Azaroual, Nathalie; Imbenotte, Michel; Mathieu, Daniel; Parmentier, Erika; Vermeersch, Gaston; Lhermitte, Michel

2008-01-15

280

Nondestructive size determination of thiol-stabilized gold nanoclusters in solution by diffusion ordered NMR spectroscopy.  

PubMed

Diffusion ordered NMR spectroscopy (DOSY) was used as an analytical tool to estimate the size of thiol-stabilized gold nanoclusters in solution, namely, phenylethanethiol (PET) stabilized Au25(PET)18, Au38(PET)24, and Au144(PET)60. This was achieved by determining the diffusion coefficient and hydrodynamic radius from solution samples that were confirmed to be monodispersed by electrospray ionization mass spectrometry. The average cluster diameters obtained by this technique were estimated to be 1.7, 2.2, and 3.1 nm for the Au25(PET)18, Au38(PET)24, and Au144(PET)60 nanoclusters, respectively, which were shown to agree well with the average diameters of the corresponding single crystal or theoretical structures reported in the literature. Consequently, the DOSY technique is demonstrated to be a potentially valuable nondestructive tool for characterization of nanoparticle mixtures and verifying the purity of product solutions. PMID:23506040

Salorinne, Kirsi; Lahtinen, Tanja; Koivisto, Jaakko; Kalenius, Elina; Nissinen, Maija; Pettersson, Mika; Häkkinen, Hannu

2013-04-01

281

Conformational analysis of an anti-androgenic, (E,E)-8-hydroxygermacrene B, using NOESY and dynamic NMR spectroscopy.  

PubMed

(E,E)-8-Hydroxygermacrene B was prepared by ketone reduction of germacrone, a naturally occurring compound from Curcuma aeruginosa Roxb. with NaBH4 at low temperature (4°C). This compound showed remarkable in vitro anti-androgenic activity (IC50 0.15ą0.022mM) applicable to male baldness treatments. NMR analysis at -50°C indicated that there were four conformational isomers of (E,E)-8-hydroxygermacrene B in a ratio of 48:40:8:4. The major conformers were assigned by (1)H NMR and 2D-NOESY NMR spectroscopy as having methyl groups at C-10 and C-4 in up-down (UD) orientations (48% predominance) and UU (40%). (1)H NMR spectra implied another two minor conformers with these methyls having DU (8%) and DD (4%) orientations. PMID:24951332

Srivilai, Jukkarin; Khorana, Nantaka; Waranuch, Neti; Suphrom, Nungruthai; Ingkaninan, Kornkanok

2014-08-01

282

Comparison of pulsed field gradient NMR and holographic relaxation spectroscopy in the study of diffusion of photochromic molecules  

NASA Astrophysics Data System (ADS)

Pulsed field gradient NMR (PFG-NMR) and holographic relaxation spectroscopy (HRS) have been compared in a study of tracer diffusion rates for the photochromic molecules azobenzene and aminoazobenzene in acetone and 1,4-dioxane. These techniques are applicable to exactly the same range of diffusion rates but can provide complementary information. The cis and trans forms of azobenzene can be distinguished in the NMR experiment, and the tracer diffusion coefficient for the cis form is found to be 5% lower than for the trans form. In the HRS experiment a single diffusion coefficient is determined from the rate of decay of the laser-induced concentration pattern of cis azobenzene. Results obtained by the two methods agree, and the magnitudes of the errors are similar. In general HRS is a much more sensitive method, but only NMR permits the diffusing species to be identified.

Lever, Lisa S.; Bradley, Michael S.; Johnson, Charles S.

283

Aliphatic chain length by isotropic mixing (ALCHIM): determining composition of complex lipid samples by (1)H NMR spectroscopy.  

PubMed

Quantifying the amounts and types of lipids present in mixtures is important in fields as diverse as medicine, food science, and biochemistry. Nuclear magnetic resonance (NMR) spectroscopy can quantify the total amounts of saturated and unsaturated fatty acids in mixtures, but identifying the length of saturated fatty acid or the position of unsaturation by NMR is a daunting challenge. We have developed an NMR technique, aliphatic chain length by isotropic mixing, to address this problem. Using a selective total correlation spectroscopy technique to excite and transfer magnetization from a resolved resonance, we demonstrate that the time dependence of this transfer to another resolved site depends linearly on the number of aliphatic carbons separating the two sites. This technique is applied to complex natural mixtures allowing the identification and quantification of the constituent fatty acids. The method has been applied to whole adipocytes demonstrating that it will be of great use in studies of whole tissues. PMID:24831341

Sachleben, Joseph R; Yi, Ruiyang; Volden, Paul A; Conzen, Suzanne D

2014-07-01

284

Orientational order of two fluoro- and isothiocyanate-substituted nematogens by combination of 13C NMR spectroscopy and DFT calculations.  

PubMed

Orientational order properties of two nematogens containing a fluoro- and isothiocyanate-substituted biphenyl moiety have been investigated by means of (13)C NMR spectroscopy. (13)C NMR spectra acquired on static samples under high-power (1)H-decoupling allowed both (13)C chemical shift anisotropies and (13)C-(19)F couplings to be measured. These data were used to determine the local principal order parameter and biaxiality for the different rigid fragments of the molecules. To this aim, advanced DFT methods for the calculation of geometrical parameters and chemical shift tensors were used. The orientational order parameters obtained by NMR have been critically compared with those obtained by dielectric spectroscopy. Trends of order parameters with temperature have been analyzed in terms of both mean field theory and the empirical Haller equation. PMID:24605890

Calucci, Lucia; Carignani, Elisa; Geppi, Marco; Macchi, Sara; Mennucci, Benedetta; Urban, Stanislaw

2014-03-27

285

NMR and IR Spectroscopy for the Structural Characterization of Edible Fats and Oils: An Instrumental Analysis Laboratory  

ERIC Educational Resources Information Center

This article describes an upper-level instrumental laboratory for undergraduates that explores the complementary nature of IR and NMR spectroscopy for analysis of several edible fats and oils that are structurally similar but differ in physical properties and health implications. Five different fats and oils are analyzed for average chain length,…

Crowther, Molly W.

2008-01-01

286

Chemical characteristics of dissolved organic matter during composting of different organic wastes assessed by 13C CPMAS NMR spectroscopy  

Microsoft Academic Search

This research aimed at assessing the chemical changes occurring in DOM extracted from different composting substrates by means of 13C CPMAS NMR spectroscopy. During composting a reduction of carbohydrates and an increase of aromatic, phenolic, carboxylic and carbonylic C were observed. The highest increase in alkyl C and the lowest increase in aromatic C were explained by the presence of

P. Caricasole; M. R. Provenzano; P. G. Hatcher; N. Senesi

2010-01-01

287

1D- and 2D-NMR spectroscopy studies of the polysaccharide gum from Spondias purpurea var. lutea  

Microsoft Academic Search

Spondias purpurea var. lutea (Anacardiaceae) trees located in Venezuela, South America, produce a clear gum very soluble in water. The polysaccharide, from this gum, contains galactosyl, arabinosyl, xylosyl, rhamnosyl and uronic acid residues. Degraded gums A and B were prepared by mild acid hydrolysis and Smith degradation, respectively. Application of 1D- and 2D-NMR spectroscopy to the original gum and its

Omaira Gutiérrez de G; Maritza Mart??nez; Lilian Sanabria; Gladys León de Pinto; J. Manuel Igartuburu

2005-01-01

288

Porosity of pillared clays studied by hyperpolarized 129Xe NMR spectroscopy and Xe adsorption isotherms.  

PubMed

The influence of the layer charge on the microstructure was studied for a series of three hybrid pillared interlayered clays based on the organic dication Me(2)DABCO(2+) and charge reduced synthetic fluorohectorites. To get a detailed picture of the local arrangements within the interlayer space, multinuclear solid-state NMR spectroscopy was performed in conjunction with high-resolution (129)Xe MAS NMR, temperature-dependent wide-line 1D and 2D (129)Xe NMR, and Ar/Ar(l) and Xe/Xe(l) physisorption measurements. The resulting layer charge (x) for the three samples are 0.48, 0.44, and 0.39 per formula unit (pfu). The samples exhibit BET equivalent surfaces between 150 and 220 m(2)/g and pore volumes which increase from 0.06 to 0.11 cm(3)/g while the layer charge reduces. 1D and 2D (1)H, (13)C, (19)F, and (29)Si MAS data reveal that the postsynthetic charge reduction induces regions with higher defect concentrations within the silicate layers. Although the pillars tend to avoid these defect-rich regions, a homogeneous and regular spacing of the Me(2)DABCO(2+) pillars is established. Both the Ar/Ar(l) physisorption and (129)Xe NMR measurements reveal comparable pore dimensions. The trend of the temperature-dependent wide-line (129)Xe spectra as well as the exchange in the EXSY spectra is typical for a narrow 2D pore system. (129)Xe high-resolution experiments allow for a detailed description of the microstructure. For x = 0.48 a bimodal distribution with pore diameters between 5.9 and 6.4 Ĺ is observed. Reducing the layer charge leads to a more homogeneous pore structure with a mean diameter of 6.6 Ĺ (x = 0.39). The adsorption enthalpies ?H(ads) determined from the temperature-dependent (129)Xe chemical shift data fit well to the ones derived from the Xe/Xe(l) physisorption measurements in the high-pressure limit while the magnitude of ?H(ads) in the low-pressure limit is significantly larger. Thus, the (129)Xe data are influenced by adsorbate-adsorbent as well as adsorbate-adsorbate interactions. PMID:23240993

Keenan, Caroline D; Herling, Markus M; Siegel, Renée; Petzold, Nikolaus; Bowers, Clifford R; Rössler, Ernst A; Breu, Josef; Senker, Jürgen

2013-01-15

289

NMR spectroscopy study of freshwater humic material in light of supramolecular assembly.  

PubMed

The structural similarity-dissimilarity of several humic-type derivatives, separated from a strongly colored freshwater sample by different sorbing solid techniques, tangential-flow ultrafiltration (UF), and large-scale preparative high-performance size-exclusion chromatography (HPSEC), were in detail studied with one-dimensional liquid 1H and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy, especially in light of the native humic-type dissolved organic matter (DOM-HM). The results support the applicability of functional cross-linked poly(vinylpyrrolidone) (PVP) or diethylaminoethyl-cellulose (DEAE) sorbents in concentrating representative integrated wholes of aquatic humic-type material along with a conventional nonionic XAD-8/DAX-8 (polymethyl methacrylates) technique. Apart from the fact that the acidification of the original humic water before a separation procedure seems not to be so destructive to the original structural composition of the DOM-HM as expected, the refinement of aquatic humic solutes, independent of the selected sorbing solid technique, will cause structural changes in the separated humic complexes in comparison with the situation predominating in the original starting material. Tangential-flow ultrafiltration (UF) proved an overpowering reliability to concentrate the aquatic DOM-HM. Most fundamental is the combined outcome of different HPSEC experiments and determined structural functionalities which indicate that almost all original DOM-HM solutes are aggregated mixtures consisting of structurally similar associations possessing various molecular size ranges, which can be separated from their integrated whole as nearly homogeneous and uniform species. This finding permits a reasonable starting point to go on working with more advanced multidimensional NMR techniques in resolving the uncertainty about supramolecular assembly of dissolved humic material. The tested conformity between the obtained molecular NMR descriptors and the corresponding previously collected FT-IR parameters was acceptable thus speaking for the fact that the less sensitive FT-IR spectroscopy can also provide valuable information on the structural and functional properties of heterogeneous humic-type mixtures. PMID:16124285

Peuravuori, Juhani

2005-08-01

290

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

PubMed

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

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

2013-10-18

291

Determination of astaxanthin and astaxanthin esters in the microalgae Haematococcus pluvialis by LC-(APCI)MS and characterization of predominant carotenoid isomers by NMR spectroscopy.  

PubMed

The oily product ZANTHIN consists of natural astaxanthin, which is manufactured from the microalgae Haematococcus pluvialis by supercritical CO(2) extraction. An HPLC method was developed to separate all of the components of the complex astaxanthin extract using a C(30) column. The separation resulted in different isomers of astaxanthin accompanied by two other carotenoids. The main component consisted of astaxanthin singly esterified with several different fatty acids. C18:3, C18:2, C18:1 and C16:0 were identified as the most commonly occurring fatty acids. Doubly esterified astaxanthin was also found, although in lower concentrations compared to singly esterified astaxanthin. After performing a detailed fatty acid analysis by GC-MS, the peaks from the extract were assigned via HPLC-MS. A trans to cis transmutation of the all-trans compound was performed by thermal treatment in order to obtain an enrichment of cis isomers as the basis for unambiguous identification via NMR experiments. The all-trans as well as the 9- and 13-cis isomers of astaxanthin were characterized in detail by UV/Vis, (1)H, and (1)H,(1)H COSY NMR spectroscopy. PMID:19466394

Holtin, Karsten; Kuehnle, Maximilian; Rehbein, Jens; Schuler, Paul; Nicholson, Graeme; Albert, Klaus

2009-11-01

292

Distinguishing Polymorphs of the Semiconducting Pigment Copper Phthalocyanine by Solid-state NMR and Raman Spectroscopy  

PubMed Central

Cu(II)(phthalocyanine) (CuPc) is broadly utilized as an archetypal molecular semiconductor and is the most widely used blue printing pigment. CuPc crystallizes in six different forms; the chemical and physical properties are substantially modulated by its molecular packing among these polymorphs. Despite the growing importance of this system, spectroscopic identification of different polymorphs for CuPc has posed difficulties. This study presents the first example of spectroscopic distinction of ?- and ?-forms of CuPc, the most widely used polymorphs, by solid-state NMR (SSNMR) and Raman spectroscopy. 13C high-resolution SSNMR spectra of ?- and ?-CuPc using very-fast magic angle spinning (VFMAS) at 20 kHz show that hyperfine shifts sensitively reflect polymorphs of CuPc. The experimental results were confirmed by ab initio chemical shift calculations. 13C and 1H SSNMR relaxation times of ?- and ?-CuPc under VFMAS also showed marked differences, presumably because of the difference in electronic spin correlation times in the two forms. Raman spectroscopy also provided another reliable method of differentiation between the two polymorphs.

Shaibat, Medhat A.; Casabianca, Leah B.; Siberio-Perez, Diana Y.; Matzger, Adam J; Ishii, Yoshitaka

2010-01-01

293

Molecular-level characterization of probucol nanocrystal in water by in situ solid-state NMR spectroscopy.  

PubMed

The molecular state of colloidal probucol nanoparticles with additives was evaluated by (13)C in situ solid-state NMR spectroscopy. The nanoparticles were obtained by dispersing a ternary co-ground mixture of probucol/polyvinylpyrrolidon (PVP)/sodium dodecyl sulfate (SDS) in water. Their mean particle size was found to be approximately 150 nm by dynamic light scattering and cryogenic-scanning electron microscopy measurements. The results of the (13)C in situ solid-state NMR spectroscopy showed that probucol existed in the crystalline state (form I) in water. (13)C liquid-state NMR results indicated that PVP and SDS interacted with probucol in water. Their broad signals suggested that the surface interaction of the probucol nanocrystal with PVP and SDS stabilized the suspension. In addition, a freeze-dried sample of the suspension was studied by (13)C solid-state NMR and powder X-ray diffraction experiments, which confirmed the presence of the probucol nanocrystals. The combination of the in situ solid-state, solid-state, and liquid-state NMR measurement results provided molecular-level insights about the role of intermolecular interactions in the design of nanoformulations. PMID:22138607

Zhang, Junying; Higashi, Kenjirou; Limwikrant, Waree; Moribe, Kunikazu; Yamamoto, Keiji

2012-02-28

294

Improvements in localized proton NMR spectroscopy of human brain. Water suppression, short echo times, and 1 ml resolution  

NASA Astrophysics Data System (ADS)

Considerable technical improvements are reported for localized proton NMR spectroscopy using stimulated echoes. When compared to previous results, proton NMR spectra of the human brain are now obtainable (i) with in vivo water suppression factors of ?1000, (ii) with only minor T2 losses and negligible distortions due to J modulation at short echo times of 10-20 ms, and (iii) from volumes of interest as small as 1-8 ml within measuring times of 1-10 min. As a consequence, the detection of cerebral metabolites is greatly facilitated. This particularly applies to the assignment of those resonances (e.g., glutamate, taurine, inositols) that suffer from strong spin-spin coupling at the field strengths commonly in use for NMR in man. Studies of regional metabolite differences, tissue heterogeneity, and focal lesions in patients benefit from the increased spatial resolution and a concomitant reduction of partial volume effects. Localized proton NMR spectroscopy was performed on young healthy volunteers. Experiments were carried out on a 2.0 T whole-body MRI/MRS system using the standard headcoil for both imaging and spectroscopy.

Frahm, J.; Michaelis, T.; Merboldt, K. D.; Bruhn, H.; Gyngell, M. L.; Hänicke, W.

295

Milk identification of different species: 13C-NMR spectroscopy of triacylglycerols from cows and buffaloes' milks.  

PubMed

Triacylglycerols from cows and buffaloes' milk fat were investigated by 13C nuclear magnetic resonance (NMR) spectroscopy. By the addition of pure triacylglycerols standards, we identified the resonances of both milk fats, and the peaks were used for qualitative and quantitative analysis of acyl groups. Multivariate analysis treatment of triacylglycerols distribution and composition parameters enabled us to identify milk. This study shows that NMR can safely be used to quantitate milk fatty acid content, providing unique information for milk identification of different animal species. PMID:11104260

Andreotti, G; Trivellone, E; Lamanna, R; Di Luccia, A; Motta, A

2000-11-01

296

Characterization of Cu Mordenite deNOx Catalysts at Variable Si/Al Ratios, by NMR, TPD and Optical Spectroscopy  

NASA Astrophysics Data System (ADS)

Cu mordenite is an effective catalyst for nitrogen oxide removal (deNOx), which is readily produced from H mordenite at various silica-to-alumina (Si/Al) ratios by ion exchange. We have characterized a set of H and Cu mordenite catalysts prepared from material originally supplied by the TOSOH Corp. (Japan), using NMR, TPD and optical Diffuse Reflectance Spectroscopy. The nuclei observed in NMR were Silicon-29, Aluminum-27 and protons. Resulst show strong effects of Si/Al ratio, upon both framework and extra-framework structures of the mordenites. Information about the state of the Cu ion in the catalysts will be reviewed.

Marzke, Robert F.; Petranovskii, Vitalii P.; Bogdanchikova, Nina E.

2002-03-01

297

Application of parahydrogen induced polarization techniques in NMR spectroscopy and imaging.  

PubMed

Magnetic resonance provides a versatile platform that allows scientists to examine many different types of phenomena. However, the sensitivity of both NMR spectroscopy and MRI is low because the detected signal strength depends on the population difference that exists between the probed nuclear spin states in a magnetic field. This population difference increases with the strength of the interacting magnetic field and decreases with measurement temperature. In contrast, hyperpolarization methods that chemically introduce parahydrogen (a spin isomer of hydrogen with antiparallel spins that form a singlet) based on the traditional parahydrogen induced polarization (PHIP) approach tackle this sensitivity problem with dramatic results. In recent years, the potential of this method for MRI has been recognized, and its impact on medical diagnosis is starting to be realized. In this Account, we describe the use of parahydrogen to hyperpolarize a suitable substrate. This process normally involves the introduction of a molecule of parahydrogen into a target to create large population differences between nuclear spin states. The reaction of parahydrogen breaks the original magnetic symmetry and overcomes the selection rules that prevent both NMR observation and parahydrogen/orthohydrogen interconversion, yielding access to the normally invisible hyperpolarization associated with parahydrogen. Therefore the NMR or MRI measurement delivers a marked increase in the detected signal strength over the normal Boltzmann-population derived result. Consequently, measurements can be made which would otherwise be impossible. This approach was pioneered by Weitekamp, Bargon, and Eisenberg, in the late 1980s. Since 1993, we have used this technique in York to study reaction mechanisms and to characterize normally invisible inorganic species. We also describe signal amplification by reversible exchange (SABRE), an alternative route to sensitize molecules without directly incorporating a molecule of parahydrogen. This approach widens the applicability of PHIP methods and the range of materials that can be hyperpolarized. In this Account we describe our parahydrogen studies in York over the last 20 years and place them in a wider context. We describe the characterization of organometallic reaction intermediates including those involved in catalytic reactions, either with or without hydride ligands. The collection of spectroscopic and kinetic data with rapid inverse detection methods has proved to be particularly informative. We can see enhanced signals for the organic products of catalytic reactions that are linked directly to the catalytic intermediates that form them. This method can therefore prove unequivocally that a specific metal complex is involved in a catalytic cycle, thus pinpointing the true route to catalysis. Studies where a pure nuclear spin state is detected show that it is possible to detect all of the analyte molecules present in a sample using NMR. In addition, we describe methods that achieve the selective detection of these enhanced signals, when set against a strong NMR background such as that of water. PMID:22452702

Duckett, Simon B; Mewis, Ryan E

2012-08-21

298

Binding of phenol and differently halogenated phenols to dissolved humic matter as measured by NMR spectroscopy.  

PubMed

1H- and 19F-NMR measurements of spin-lattice (T1) and spin-spin (T2) relaxationtimes and diffusion ordered spectroscopy (DOSY) were applied to investigate the association of nonsubstituted (phenol (P)) and halogen-substituted (2,4-dichlorophenol (DCP); 2,4,6-trichlorophenol (TCP), and 2,4,6-trifluorophenol (TFP) phenols with a dissolved humic acid (HA). T1 and T2 values for both 1H and 19F in phenols decreased with enhancing HA concentration, indicating reduction in molecular mobility due to formation of noncovalent interactions. Moreover, correlation times (tau c) for different hydrogen and fluorine atoms in phenols showed that anisotropic mobility turned into isotropic motion with HA additions. Changes in relaxation times suggested that DCP and TCP were more extensively bound to HA than P and TFP. This was confirmed by diffusion measurements which showed full association of DCP and TCP to a less amount of HA than that required for entire complexation of P and TFP. Calculated values of binding constants (Ka) reflected the overall NMR behavior, being significantly larger for DCP- and TCP-HA (10.04 +/- 1.32 and 4.47 +/- 0.35 M(-1), respectively) than for P- and TFP-HA complexes (0.57 +/- 0.03 and 0.28 +/- 0.01 M(-1), respectively). Binding increased with decreasing solution pH, thus indicating a dependence on the fraction of protonated form (alpha) of phenols in solution. However, it was found that the hydrophobicity conferred to phenols by chlorine atoms on aromatic rings is a stronger drive than alpha for the phenols repartition within the HA hydrophobic domains. PMID:19708369

Smejkalová, Daniela; Spaccini, Riccardo; Fontaine, Barbara; Piccolo, Alessandro

2009-07-15

299

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

300

Intracellular free calcium concentration measured with /sup 19/F NMR spectroscopy in intact ferret hearts  

SciTech Connect

Changes in the intracellular free Ca/sup 2 +/ concentration, (Ca/sup 2 +/)/sub i/, mediate excitation-contraction coupling in the heart and contribute to cellular injury during ischemia and reperfusion. To study these processes directly, the authors measured (Ca/sup 2 +/)/sub i/ in perfused ferret (Mustela putorius furo) hearts using /sup 19/F NMR spectroscopy to detect the 5,5'-difluoro derivative of the Ca/sup 2 +/ chelator, 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). To load cells, hearts were perfused with the acetoxymethyl ester derivative of 5,5'-F/sub 2/-BAPTA. They measured /sup 19/F NMR spectra and left ventricular pressure simultaneously,at rest and during pacing at various external Ca concentrations ((Ca)/sub 0/). Although contractile force was attenuated by the Ca/sup 2 +/ buffering properties of 5,5'-F/sup 2/-BAPTA, the decrease in pressure could be overcome by raising (Ca)/sub 0/. The mean value of 104 nM for (Ca/sup 2 +/)/sub i/ at rest in the perfused heart agrees well with previous measurements in isolated ventricular muscle. During pacing at 0.6-4 Hz, time-averaged (Ca/sup 2 +/)/sub i/ increased; the effect of pacing was augmented by increasing (Ca)/sub 0/. (Ca/sup 2 +/)/sub i/ more than tripled during 10-20 min of global ischemia, and returned toward control levels upon reperfusion. This approach promises to be particularly useful in investigating the physiology of intact hearts and the pathophysiology of alterations in the coronary circulation

Marban, E.; Kitakaze, M.; Kusuoka, H.; Porterfield, J.K.; Yue, D.T.; Chacko, V.P.

1987-08-01

301

Higher order amyloid fibril structure by MAS NMR and DNP spectroscopy.  

PubMed

Protein magic angle spinning (MAS) NMR spectroscopy has generated structural models of several amyloid fibril systems, thus providing valuable information regarding the forces and interactions that confer the extraordinary stability of the amyloid architecture. Despite these advances, however, obtaining atomic resolution information describing the higher levels of structural organization within the fibrils remains a significant challenge. Here, we detail MAS NMR experiments and sample labeling schemes designed specifically to probe such higher order amyloid structure, and we have applied them to the fibrils formed by an eleven-residue segment of the amyloidogenic protein transthyretin (TTR(105-115)). These experiments have allowed us to define unambiguously not only the arrangement of the peptide ?-strands into ?-sheets but also the ?-sheet interfaces within each protofilament, and in addition to identify the nature of the protofilament-to-protofilament contacts that lead to the formation of the complete fibril. Our efforts have resulted in 111 quantitative distance and torsion angle restraints (10 per residue) that describe the various levels of structure organization. The experiments benefited extensively from the use of dynamic nuclear polarization (DNP), which in some cases allowed us to shorten the data acquisition time from days to hours and to improve significantly the signal-to-noise ratios of the spectra. The ?-sheet interface and protofilament interactions identified here revealed local variations in the structure that result in multiple peaks for the exposed N- and C-termini of the peptide and in inhomogeneous line-broadening for the residues buried within the interior of the fibrils. PMID:24304221

Debelouchina, Galia T; Bayro, Marvin J; Fitzpatrick, Anthony W; Ladizhansky, Vladimir; Colvin, Michael T; Caporini, Marc A; Jaroniec, Christopher P; Bajaj, Vikram S; Rosay, Melanie; Macphee, Cait E; Vendruscolo, Michele; Maas, Werner E; Dobson, Christopher M; Griffin, Robert G

2013-12-26

302

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

PubMed Central

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

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

2013-01-01

303

Structural models of activated ?-alumina surfaces revisited: Thermodynamics, NMR and IR spectroscopies from ab initio calculations  

NASA Astrophysics Data System (ADS)

The activation of highly catalytic ?-alumina surfaces by thermal treatment and the description of the related chemical processes at atomic scale is a topical issue. According to a recent study [J. Am. Chem. Soc. 134 (2012) 14430], the enhanced reactivity of ?-alumina has been associated to tri-coordinated aluminum sites which supposedly are exposed exclusively on the (1 1 0) surfaces of this oxide. In this work, we explore this possibility by modeling the (1 0 0) and (1 1 0) terminations using Krokidis et al. [J. Phys. Chem. B 105 (2001) 5121] bulk structure and performing an extensive search of the most stable hydrated surface models at conditions consistent with experiment. Among the 156 structures analyzed, we identify several "metastable" models for the (1 1 0) surface with a considerable probability of containing the AlIII centers at OH coverages of 9.0 and 6.0 OH/nm2. We then test the reactivity of these sites through their Lewis acidity by simulating the CO adsorbtion on the surface and our results confirm the high reactivity of AlIII centers. Based on the Gibbs free energy of the explored structures, we carry on a thermodynamical analysis at varying hydroxylation degrees and pretreatment temperatures and simulate the experimental volcano-type behavior reported in [J. Am. Chem. Soc. 134 (2012) 14430] and predict the optimum pretreatment temperature as 700 °C, in very good agreement with experimental findings. We further use infrared and solid state MAS NMR spectroscopies and reproduce the 1H MAS NMR spectra under high vacuum conditions (10-5 Torr). The strong resemblance of spectra to the experimental ones in the literature [J. Phys. Chem. C 116 (2012) 834] validate further the structural models we have generated in this study.

Ferreira, Ary R.; Küçükbenli, Emine; de Gironcoli, Stefano; Souza, Wladmir F.; Chiaro, Sandra Shirley X.; Konstantinova, Elena; Leităo, Alexandre A.

2013-09-01

304

Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State 2H NMR Spectroscopy  

PubMed Central

Sphingomyelin is a lipid that is abundant in the nervous systems of mammals, where it is associated with putative microdomains in cellular membranes and undergoes alterations due to aging or neurodegeneration. We investigated the effect of varying the concentration of cholesterol in binary and ternary mixtures with N-palmitoylsphingomyelin (PSM) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using deuterium nuclear magnetic resonance (2H NMR) spectroscopy in both macroscopically aligned and unoriented multilamellar dispersions. In our experiments, we used PSM and POPC perdeuterated on the N-acyl and sn-1 acyl chains, respectively. By measuring solid-state 2H NMR spectra of the two lipids separately in mixtures with the same compositions as a function of cholesterol mole fraction and temperature, we obtained clear evidence for the coexistence of two liquid-crystalline domains in distinct regions of the phase diagram. According to our analysis of the first moments M1 and the observed 2H NMR spectra, one of the domains appears to be a liquid-ordered phase. We applied a mean-torque potential model as an additional tool to calculate the average hydrocarbon thickness, the area per lipid, and structural parameters such as chain extension and thermal expansion coefficient in order to further define the two coexisting phases. Our data imply that phase separation takes place in raftlike ternary PSM/POPC/cholesterol mixtures over a broad temperature range but vanishes at cholesterol concentrations equal to or greater than a mole fraction of 0.33. Cholesterol interacts preferentially with sphingomyelin only at smaller mole fractions, above which a homogeneous liquid-ordered phase is present. The reasons for these phase separation phenomena seem to be differences in the effects of cholesterol on the configurational order of the palmitoyl chains in PSM-d31 and POPC-d31 and a difference in the affinity of cholesterol for sphingomyelin observed at low temperatures. Hydrophobic matching explains the occurrence of raftlike domains in cellular membranes at intermediate cholesterol concentrations but not saturating amounts of cholesterol.

Bartels, Tim; Lankalapalli, Ravi S.; Bittman, Robert; Beyer, Klaus; Brown, Michael F.

2009-01-01

305

Raftlike mixtures of sphingomyelin and cholesterol investigated by solid-state 2H NMR spectroscopy.  

PubMed

Sphingomyelin is a lipid that is abundant in the nervous systems of mammals, where it is associated with putative microdomains in cellular membranes and undergoes alterations due to aging or neurodegeneration. We investigated the effect of varying the concentration of cholesterol in binary and ternary mixtures with N-palmitoylsphingomyelin (PSM) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using deuterium nuclear magnetic resonance ((2)H NMR) spectroscopy in both macroscopically aligned and unoriented multilamellar dispersions. In our experiments, we used PSM and POPC perdeuterated on the N-acyl and sn-1 acyl chains, respectively. By measuring solid-state (2)H NMR spectra of the two lipids separately in mixtures with the same compositions as a function of cholesterol mole fraction and temperature, we obtained clear evidence for the coexistence of two liquid-crystalline domains in distinct regions of the phase diagram. According to our analysis of the first moments M1 and the observed (2)H NMR spectra, one of the domains appears to be a liquid-ordered phase. We applied a mean-torque potential model as an additional tool to calculate the average hydrocarbon thickness, the area per lipid, and structural parameters such as chain extension and thermal expansion coefficient in order to further define the two coexisting phases. Our data imply that phase separation takes place in raftlike ternary PSM/POPC/cholesterol mixtures over a broad temperature range but vanishes at cholesterol concentrations equal to or greater than a mole fraction of 0.33. Cholesterol interacts preferentially with sphingomyelin only at smaller mole fractions, above which a homogeneous liquid-ordered phase is present. The reasons for these phase separation phenomena seem to be differences in the effects of cholesterol on the configurational order of the palmitoyl chains in PSM-d31 and POPC-d31 and a difference in the affinity of cholesterol for sphingomyelin observed at low temperatures. Hydrophobic matching explains the occurrence of raftlike domains in cellular membranes at intermediate cholesterol concentrations but not saturating amounts of cholesterol. PMID:18839945

Bartels, Tim; Lankalapalli, Ravi S; Bittman, Robert; Beyer, Klaus; Brown, Michael F

2008-11-01

306

Soil meso- and microporosity studied by 129Xe nmr spectroscopy of adsorbed xenon  

NASA Astrophysics Data System (ADS)

The pore structure of soil significantly affects its density and the transport of water, air, nutrients and pollutants through the soil. Micropores (< 2 nm) play a special role in sorption processes, since most of the soil surface area is located in such pores. Meso- and macropores (2 - 50 nm and >50 nm, respectively) act as a transport system, the former pores provide an access to micropores. Despite of significant progress in evaluating soil porosity by the use of electron microscopy, mercury intrusion porosimetry and standard adsorption methods, many aspects still need further examination. In the present contribution, 129Xe NMR spectroscopy of adsorbed xenon was applied for the first time for the characterisation of soil meso- and microporosity. Soils with different texture were studied. The impact of organic matter on the porosity of the mineral phase was analysed. Also, we examined the influence of paramagnetic soil constituents on the 129Xe resonance parameters. The study of the model system, Ca-montmorillonite, demonstrated that quantitative information about pore sizes in soil related materials can be provided, if the impact of paramagnetic species is avoided. In natural soils, the pores within the mineral phase can be analysed for relatively large particles (>20-50 ľm), where the 129Xe resonance parameters are not affected by xenon exchange between intra- and interparticle void spaces. In contrast, for the clay-sized fractions the combined internal - external pore system is probed. The presence of micropores (< 2 nm) can always be inferred from the observed 129Xe downfield shifts increasing with xenon pressure. In contrast, spectral lines close to the xenon gas line position suggest adsorption in large interparticle pores. In the studied soils (Luvisol, Gleysol and Podzol) no micropores within the mineral phase available for xenon adsorption were found. The possible reason is that such pores are occupied by small molecules of the soil organic matter. When xenon exchange between different adsorption zones (e.g., pores of differing size) was slow on an NMR time scale, separate signals were distinguished, each characterising xenon behaviour in the respective adsorption zone. Variable extent of accessibility of mesopores within the mineral phase of the various soils has been revealed. In Podzol it was shown to be higher than in other soils studied. A model for the possible mutual location of organic matter and iron species in natural soils is suggested. Complementary studies using standard adsorption methods were performed and they showed a good coincidence with the 129Xe NMR results.

Filimonova, S.; Knicker, H.; Häusler, W.; Kögel-Knabner, I.

2003-04-01

307

Bond covalency in perovskite oxynitrides ATaO2N (A = Ca, Sr, Ba) studied by 14N NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Local geometry and bond ionicity around the nitride ions in simple perovskite oxynitrides ATaO2N (A = Ca, Sr, Ba) have been investigated by solid-state magic-angle spinning (MAS) NMR spectroscopy. From all three compounds, fairly sharp 14N NMR peaks were observed, suggestive of the symmetric coordination environment of nitride ions. The 14N chemical shifts of ATaO2N, ? = 269-272 ppm relative to NH4Cl (? = 0 ppm), are correlated to the bond ionicity, based on the N-Ta bond distances and Ta-N-Ta bond angles determined from the Rietveld refinement of neutron diffraction patterns. The 1H NMR measured for BaTaO2N presented a peak corresponding to H2O, implying that the polycrystalline surface of present oxynitride phases is covered by hydroxide terminals.

Kim, Young-Il; Paik, Younkee

2012-05-01

308

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

NASA Astrophysics Data System (ADS)

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

Kumar, Arvind; Boykin, David W.

1993-07-01

309

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

PubMed Central

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

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

2009-01-01

310

Investigation of Local Structures in Layered Niobates by Solid-state NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

Research on ion-exchangeable layered niobates has attracted great attention due to their unique structures and corresponding variations in properties and applications, such as ion conductors, solid acids, and water splitting catalysts. Families of layered niobates include double-layered or triple-layered Dion-Jacobson type perovskites (ALaNb2O7, A = Cs, Rb, K, H; AM2Nb3O10, A = Rb, K, H; M = Sr, Ca), layered niobates with both edge and corner sharing of NbO6 octahedra (KNb3O8, HNb3O6, Nb 6O17 and H4Nb6O17) and many others. Lately, more developments in the layered niobates through a variety of topochemical manipulations have been achieved. The topochemical reactions include ion exchange, exfoliation, substitution, and etc. As a result, many new materials have been successfully prepared, for example, solid solutions (ALa2NbTi2O10, ACaLaNb2TiO 10 and ACa2Nb3-xTaxO10, etc.), nanosheets (HNb3O8, H4Nb6O17, HLaNb2O7, HCa2Nb3O10, etc., to intercalate with organic molecules such as tetrabutylammonium hydroxide or n-butylamines), and nanoscrolls (from H2K2Nb 6O17). While these structural modifications often induce improvements in properties, the fundamental mechanisms of improvements in properties upon the modifications, especially local structural arrangements are poorly understood, which is often limited by structural characterizations. Particularly, the characterizations of the exfoliated nanosheets can be difficult by conventional X-ray diffraction (XRD) method due to disordered structures. Alternatively, solid-state nuclear magnetic resonance (NMR) spectroscopy is a useful tool to study local structures in solids. The structural information can be extracted by examining intrinsic interactions, such as quadrupolar, chemical shielding, and dipolar interactions, which are all associated with local environments surrounding a specific nucleus, 1H or 93Nb in layered niobates. The ultimate goal of this dissertation is to understand the relationships between local structures of layered niobates and their chemical or physical properties, and provide insights into further modifications and improvements. The primary objectives of this work are summarized below: I. Synthesis of series of layered niobates (ALaNb2O7 , A = Cs, Rb, K; KNb3O8; K4Nb 6O17; RbLa2NbTi2O10 and RbCaLaNb2TiO10) by microwave heating or cation exchange methods, their protonated forms by acid exchange (HLaNb2O 7, H3ONb3O8 and HNb3O 8, H4Nb8O17, HLa2NbTi 2O10 and HCaLaNb2TiO10), and three nanosheet niobates by exfoliation (HNb3O8, H4Nb 6O17 and HLaNb2O7 nanosheets). II. Structural characterizations of all niobates by powder XRD and solid-state NMR spectroscopy. Powder XRD is used to determine lattice constants and long-range structural ordering. Solid-state NMR is used to determine the electric field gradient parameters, chemical shift anisotropy parameters and dipolar coupling constants. Solid-state NMR techniques include 93Nb MQMAS, wide-line VOCS echo and WURST-echo; 1H{93Nb} CP, TRAPDOR, S-RESPDOR and iS-RESPDOR experiments. III. Understanding the trends of changes in NMR parameters with respect to cation exchange, exfoliation and compositional alteration, and correlation of the NMR parameters with local environments and possible structural rearrangements. IV. Identification of proton locations in the acid-exchanged niobates and surface acidity for the exfoliated nanosheets, based on 1H chemical shifts and dipolar coupling information from CP, S-RESPDOR and iS-RESPDOR experiments.

Liu, Ting

311

Indirectly detected chemical shift correlation NMR spectroscopy in solids under fast magic angle spinning  

SciTech Connect

The development of fast magic angle spinning (MAS) opened up an opportunity for the indirect detection of insensitive low-{gamma} nuclei (e.g., {sup 13}C and {sup 15}N) via the sensitive high-{gamma} nuclei (e.g., {sup 1}H and {sup 19}F) in solid-state NMR, with advanced sensitivity and resolution. In this thesis, new methodology utilizing fast MAS is presented, including through-bond indirectly detected heteronuclear correlation (HETCOR) spectroscopy, which is assisted by multiple RF pulse sequences for {sup 1}H-{sup 1}H homonuclear decoupling. Also presented is a simple new strategy for optimization of {sup 1}H-{sup 1}H homonuclear decoupling. As applications, various classes of materials, such as catalytic nanoscale materials, biomolecules, and organic complexes, are studied by combining indirect detection and other one-dimensional (1D) and two-dimensional (2D) NMR techniques. Indirectly detected through-bond HETCOR spectroscopy utilizing refocused INEPT (INEPTR) mixing was developed under fast MAS (Chapter 2). The time performance of this approach in {sup 1}H detected 2D {sup 1}H{l_brace}{sup 13}C{r_brace} spectra was significantly improved, by a factor of almost 10, compared to the traditional {sup 13}C detected experiments, as demonstrated by measuring naturally abundant organic-inorganic mesoporous hybrid materials. The through-bond scheme was demonstrated as a new analytical tool, which provides complementary structural information in solid-state systems in addition to through-space correlation. To further benefit the sensitivity of the INEPT transfer in rigid solids, the combined rotation and multiple-pulse spectroscopy (CRAMPS) was implemented for homonuclear {sup 1}H decoupling under fast MAS (Chapter 3). Several decoupling schemes (PMLG5{sub m}{sup {bar x}}, PMLG5{sub mm}{sup {bar x}x} and SAM3) were analyzed to maximize the performance of through-bond transfer based on decoupling efficiency as well as scaling factors. Indirect detection with assistance of PMLG{sub m}{sup {bar x}} during INEPTR transfer proved to offer the highest sensitivity gains of 3-10. In addition, the CRAMPS sequence was applied under fast MAS to increase the {sup 1}H resolution during t{sub 1} evolution in the traditional, {sup 13}C detected HETCOR scheme. Two naturally abundant solids, tripeptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (f-MLF-OH) and brown coal, with well ordered and highly disordered structures, respectively, are studied to confirm the capabilities of these techniques. Concomitantly, a simple optimization of {sup 1}H homonuclear dipolar decoupling at MAS rates exceeding 10 kHz was developed (Chapter 4). The fine-tuned decoupling efficiency can be obtained by minimizing the signal loss due to transverse relaxation in a simple spin-echo experiment, using directly the sample of interest. The excellent agreement between observed decoupling pattern and earlier theoretical predictions confirmed the utility of this strategy. The properties of naturally abundant surface-bound fluorocarbon groups in mesoporous silica nanoparticles (MSNs) were investigated by the above-mentioned multidimensional solid-state NMR experiments and theoretical modeling (Chapter 5). Two conformations of (pentafluorophenyl)propyl groups (abbreviated as PFP) were determined as PFP-prone and PFP-upright, whose aromatic rings are located above the siloxane bridges and in roughly upright position, respectively. Several 1D and 2D NMR techniques were implemented in the characterizations, including indirectly detected {sup 1}H{l_brace}{sup 13}C{r_brace} and {sup 19}F{l_brace}{sup 13}C{r_brace} 2D HETCOR, Carr-Purcell-Meiboom-Gill (CPMG) assisted {sup 29}Si direct polarization and {sup 29}Si{sup 19}F 2D experiments, 2D double-quantum (DQ) {sup 19}F MAS NMR spectra and spin-echo measurements. Furthermore, conformational details of two types of PFP were confirmed by theoretical calculation, operated by Dr. Takeshi Kobayashi. Finally, the arrangement of two surfactants, cetyltrimetylammoium bromide (CTAB) and cetylpyridinium bromide (CPB), mixed inside th

Mao, Kanmi

2011-08-15

312

Selectively Labeling the Heterologous Protein in Escherichia coli for NMR Studies: A Strategy to Speed Up NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance is an important tool for high-resolution structural studies of proteins. It demands high protein concentration and high purity; however, the expression of proteins at high levels often leads to protein aggregation and the protein purification step can correspond to a high percentage of the overall time in the structural determination process. In the present article we show that the step of sample optimization can be simplified by selective labeling the heterologous protein expressed in Escherichia coli by the use of rifampicin. Yeast thioredoxin and a coix transcription factor Opaque 2 leucine zipper (LZ) were used to show the effectiveness of the protocol. The 1H/ 15N heteronuclear correlation two-dimensional NMR spectrum (HMQC) of the selective 15N-labeled thioredoxin without any purification is remarkably similar to the spectrum of the purified protein. The method has high yields and a good 1H/ 15N HMQC spectrum can be obtained with 50 ml of M9 growth medium. Opaque 2 LZ, a difficult protein due to the lower expression level and high hydrophobicity, was also probed. The 15N-edited spectrum of Opaque 2 LZ showed only the resonances of the protein of heterologous expression (Opaque 2 LZ) while the 1H spectrum shows several other resonances from other proteins of the cell lysate. The demand for a fast methodology for structural determination is increasing with the advent of genome/proteome projects. Selective labeling the heterologous protein can speed up NMR structural studies as well as NMR-based drug screening. This methodology is especially effective for difficult proteins such as hydrophobic transcription factors, membrane proteins, and others.

Almeida, F. C. L.; Amorim, G. C.; Moreau, V. H.; Sousa, V. O.; Creazola, A. T.; Américo, T. A.; Pais, A. P. N.; Leite, A.; Netto, L. E. S.; Giordano, R. J.; Valente, A. P.

2001-01-01

313

Characterisation of commercially available linear alkylbenzenesulfonates by LC-SPE-NMR\\/MS (liquid chromatography-solid phase extraction-nuclear magnetic resonance spectroscopy-mass spectroscopy)  

Microsoft Academic Search

Commercially available linear alkylbenzenesulfonates (LASs) are a mixture of various homologues and isomers, leading to 20 major species. In this work we investigated the commercial product by liquid chromatography-solid phase extraction-nuclear magnetic resonance spectroscopy-mass spectrometry (LC-SPE-NMR\\/MS). The commercial product was separated into 17 fractions by liquid chromatography (LC). After chromatographic separation, 5% of the flow was split to a mass

S. Schmidt; C. Piechotta; M. Godejohann; T. Win; I. Nehls; C. Mügge

2010-01-01

314

The degradation of zinc dialkyldithiophosphate additives in fully formulated engine oil as studied by P-31 NMR spectroscopy  

SciTech Connect

Two fully-formulated engine oils containing zinc dialkyldithiophosphate (ZDDP) were tested at different oil temperature regimes during long distance, high speed field tests (15000 km and 145 {plus_minus} 10 km/hr). P-31 NMR spectroscopy was used to characterize the ZDDPs and the degradation products formed during the field tests. It was found that basic ZDDP degradation products were thiophosphates and phosphates, and the thiophosphates could be further oxidized to form phosphates when the oil temperature was high. The dependence of the ZDDP degradation pathway with oil temperature is discussed. The amount of ZDDP in the used oil was related to the viscosity increase of that oil, which increased dramatically when the ZDDP was exhausted. In the fresh oil, ZDDP formed some sort of complex, but the complexed ZDDP was released during the field test as observed by P-31 NMR spectroscopy. 20 refs., 11 figs., 4 tabs.

Pu Peng; Shan-Zhen Hong; Wan-Zhen Lu [SINOPEC, Beijing (China)

1994-03-01

315

Cherry tomatoes metabolic profile determined by (1)H-High Resolution-NMR spectroscopy as influenced by growing season.  

PubMed

The content of the most valuable metabolites present in the lipophilic fraction of Protected Geographical Indication cherry tomatoes produced in Pachino (Italy) was observed for 2 cultivated varieties, i.e. cv. Naomi and cv. Shiren, over a period of 3years in order to observe variations due to relevant climatic parameters, e.g. solar radiation and average temperature, characterising different seasons. (1)H-NMR spectroscopy was applied and spectral data were processed by means of Principal Component Analysis (PCA). We found that the metabolic profile was different for the two considered cultivated varieties and they were differently affected by climatic conditions. Major metabolites influenced by cropping period were ?-tocopherol and the unsaturated lipid fraction in Naomi cherry tomatoes, and chlorophylls and phospholipids in Shiren variety, respectively. These results furnished useful information on seasonal dynamics of such important nutritional metabolites contained in tomatoes, confirming also NMR spectroscopy as powerful tool to define a complete metabolic profiling. PMID:24874378

Masetti, Olimpia; Ciampa, Alessandra; Nisini, Luigi; Valentini, Massimiliano; Sequi, Paolo; Dell'Abate, Maria Teresa

2014-11-01

316

Structural studies on the oligomers from the polysaccharide of Gracilaria textorii (Rhodophyta) using ?-agarase and13C-NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The 60% ethanolic extract from Gracilaria textorii (Rhodophyta) was degraded with ?-agarase, and certain charged (sulfated) and neutral oligosaccharides were separated by using DEAE Sephadex A25 and Bio- gel P6, P2 chromatographic techniques. Some of the charged oligomers were verified to be neoagarotetraose-63-sulfate (DP2), neoagarohexaose-63, 65-disulfate (DP3) and neoagarooctaose-63, 65, 67-trisulfate (DP4) by using13C- and1H-NMR spectroscopy. One neutral oligomer was assumed to be a mixture of methylated neoagarotetraoses (DP2) by1H-NMR spectroscopy. These oligomers assigned by their chemical shifts may be used as the model compounds for the structural investigation of the agar-type sulfated polysaccharides using the ?-agarase degradation method.

Ji, Minghou; Lahaye, M.; Yaphe, W.

1990-06-01

317

Protein fold determined by paramagnetic magic-angle spinning solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Biomacromolecules that are challenging for the usual structural techniques can be studied with atomic resolution by solid-state NMR spectroscopy. However, the paucity of distance restraints >5 Ĺ, traditionally derived from measurements of magnetic dipole-dipole couplings between protein nuclei, is a major bottleneck that hampers such structure elucidation efforts. Here, we describe a general approach that enables the rapid determination of global protein fold in the solid phase via measurements of nuclear paramagnetic relaxation enhancements (PREs) in several analogues of the protein of interest containing covalently attached paramagnetic tags, without the use of conventional internuclear distance restraints. The method is demonstrated using six cysteine-EDTA-Cu2+ mutants of the 56-residue B1 immunoglobulin-binding domain of protein G, for which ~230 longitudinal backbone 15N PREs corresponding to distances of ~10-20 Ĺ were obtained. The mean protein fold determined in this manner agrees with the X-ray structure with a backbone atom root-mean-square deviation of 1.8 Ĺ.

Sengupta, Ishita; Nadaud, Philippe S.; Helmus, Jonathan J.; Schwieters, Charles D.; Jaroniec, Christopher P.

2012-05-01

318

Analysis of Ascarosides from Caenorhabditis elegans Using Mass Spectrometry and NMR Spectroscopy  

PubMed Central

The nematode Caenorhabditis elegans secretes a family of water-soluble small molecules, known as the ascarosides, into its environment and uses these ascarosides in chemical communication. The ascarosides are derivatives of the 3,6-dideoxysugar ascarylose, modified with different fatty acid-derived side chains. C. elegans uses specific ascarosides, which are together known as the dauer pheromone, to trigger entry into the stress-resistant dauer larval stage. In addition, C. elegans uses specific ascarosides to control certain behaviors, including mating attraction, aggregation, and avoidance. Although in general the concentration of the ascarosides in the environment increases with population density, C. elegans can vary the types and amounts of ascarosides that it secretes depending on the culture conditions under which it has been grown and its developmental history. Here, we describe how to grow high-density worm cultures and the bacterial food for those cultures, as well as how to extract the culture medium to generate a crude pheromone extract. Then, we discuss how to analyze the types and amounts of ascarosides in that extract using mass spectrometry and NMR spectroscopy.

Zhang, Xinxing; Noguez, Jaime H.; Zhou, Yue; Butcher, Rebecca A.

2014-01-01

319

Molecular areas of phospholipids as determined by 2H NMR spectroscopy. Comparison of phosphatidylethanolamines and phosphatidylcholines.  

PubMed Central

The role of lipid diversity in biomembranes is one of the major unsolved problems in biochemistry. One parameter of possible importance is the mean cross-sectional area occupied per lipid molecule, which may be related to formation of nonbilayer structures and membrane protein function. We have used 2H NMR spectroscopy to compare the properties of 1,2-diperdeuteriopalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE-d62) and 1,2-diperdeuteriopalmitoyl-sn-glycero-3-phosphocholine (DPPC-d62) in the L alpha phase. We find that DPPE has greater segmental order than DPPC, and that this increase in order is related to the smaller area per acyl chain found for DPPE. Values of the mean cross-sectional chain area are calculated using a simple diamond lattice model for the acyl chain configurational statistics, together with dilatometry data. The results obtained for the mean area per molecule are comparable with those from low angle x-ray diffraction studies.

Thurmond, R L; Dodd, S W; Brown, M F

1991-01-01

320

Conformational studies of a novel cationic glycolipid, glyceroplasmalopsychosine, from bovine brain by NMR spectroscopy.  

PubMed

A novel glycosphingolipid containing a long chain aldehyde conjugated to galactose and glycerol, Gro1(3)-O-CH((CH(2))(n)CH(3))-O-6Galbeta-sphingosine (glyceroplasmalopsychosine) has been studied by NMR spectroscopy (Hikita et al. J. Biol. Chem. 2001, 276, 23084-23091). We further report here on the conformation showing the galactose and the glycerol at the end of two parallel hydrophobic chains, i.e. the sphingosine and the fatty aldehyde. This is proposed based on the interproton distances derived from ROESY experiments and 3 J (H,H) coupling constants. The absence of any intraresidual NOEs between protons in the glycerol residue suggested that the C-C-2 and C-C-3 bonds in the glycerol may be rotating freely, supporting the proposed conformation in which the unique terminal glycerol is in an environment with a minimal steric hindrance. The present study proposes a conformation of glyceroplasmalopsychosine greatly different from the two conventional plasmalopsychosines possessing a fatty aldehyde chain oriented in an opposite direction to the sphingosine. PMID:12423957

Iida-Tanaka, Naoko; Hikita, Toshiyuki; Hakomori, Sen-itiroh; Ishizuka, Ineo

2002-10-11

321

Revealing the metabonomic variation of rosemary extracts using 1H NMR spectroscopy and multivariate data analysis.  

PubMed

The molecular compositions of rosemary ( Rosmarinus officinalis L.) extracts and their dependence on extraction solvents, seasons, and drying processes were systematically characterized using NMR spectroscopy and multivariate data analysis. The results showed that the rosemary metabonome was dominated by 33 metabolites including sugars, amino acids, organic acids, polyphenolic acids, and diterpenes, among which quinate, cis-4-glucosyloxycinnamic acid, and 3,4,5-trimethoxyphenylmethanol were found in rosemary for the first time. Compared with water extracts, the 50% aqueous methanol extracts contained higher levels of sucrose, succinate, fumarate, malonate, shikimate, and phenolic acids, but lower levels of fructose, glucose, citrate, and quinate. Chloroform/methanol was an excellent solvent for selective extraction of diterpenes. From February to August, the levels of rosmarinate and quinate increased, whereas the sucrose level decreased. The sun-dried samples contained higher concentrations of rosmarinate, sucrose, and some amino acids but lower concentrations of glucose, fructose, malate, succinate, lactate, and quinate than freeze-dried ones. These findings will fill the gap in the understanding of rosemary composition and its variations. PMID:18800806

Xiao, Chaoni; Dai, Hui; Liu, Hongbing; Wang, Yulan; Tang, Huiru

2008-11-12

322

Detection of Anisotropy in Cartilage Using 2H Double-Quantum-Filtered NMR-Spectroscopy  

NASA Astrophysics Data System (ADS)

Double-quantum-filtered (DQF) NMR spectroscopy of I = 1 spin systems is a diagnostic tool for the detection of anisotropy in macroscopically disordered systems. For deuterium, this method reveals the presence of a residual quadrupolar interaction for D 2O in bovine nasal cartilage. This tissue is not macroscopically ordered and the quadrupolar splitting is not resolved. Fitting the calculated spectral lineshapes to the experimental results was possible only when a distribution of the residual quadrupolar interaction, omega(q), was assumed. The series of DQF lineshapes obtained for different creation times in the DQF experiment could be fitted using a single set of three parameters: the average residual quadrupolar interaction overline? q/2? = 110 Hz, its standard deviation ?? q/2? = 73 Hz, and the transverse relaxation rate of 63 s -1. Separate deuterium DQF measurements for the constituents of the cartilage, collagen, and chondroitin sulfate indicated that the DQF spectra of cartilage are the result of anisotropic motion of D 2O due to binding to the fibrous collagen in the tissue.

Sharf, Y.; Eliav, U.; Shinar, H.; Navon, G.

323

Near constant loss regime in fast ionic conductors analyzed by impedance and NMR spectroscopies.  

PubMed

Universal dielectric response (UDR) and nearly constant loss (NCL) dispersive regimes have been investigated in fast ion conductors with perovskite and NASICON structure by using NMR and impedance spectroscopy (IS). In this study, the electrical behavior of La0.5Li0.5TiO3 (LLTO-05) perovskite and Li1.2Ti1.8Al0.2(PO4)3 (LTAP0-02) NASICON compounds was investigated. In both systems a three-dimensional network of conduction paths is present. In the Li-rich LLTO-05 sample, lithium and La are randomly distributed on A-sites of perovskites, but in LTAP0-02 Li and cation vacancies are preferentially disposed at M1 and M2 sites. In perovskite compounds, local motions produced inside unit cells are responsible for the large "near constant loss" regime detected at low temperatures, however, in the case of NASICON compounds, local motions not participating in long-range charge transport were not detected. In both analyzed systems long-range correlated motions are responsible for dc-conductivity values of ceramic grains near 10(-3) S cm(-1) at room temperature, indicating that low-temperature local motions, producing large NCL contribution, are not required to achieve the highest ionic conductivities. PMID:24944081

Bucheli, Wilmer; Arbi, Kamel; Sanz, Jesús; Nuzhnyy, Dmitry; Kamba, Stanislav; Várez, Alejandro; Jimenez, Ricardo

2014-08-01

324

Diffusion in Model Networks as Studied by NMR and Fluorescence Correlation Spectroscopy  

PubMed Central

We have studied the diffusion of small solvent molecules (octane) and larger hydrophobic dye probes in octane-swollen poly(dimethyl siloxane) linear-chain solutions and end-linked model networks, using pulsed-gradient nuclear magnetic resonance (NMR) and fluorescence correlation spectroscopy (FCS), respectively, focusing on diffusion in the bulk polymer up to the equilibrium degree of swelling of the networks, that is, 4.8 at most. The combination of these results allows for new conclusions on the feasibility of different theories describing probe diffusion in concentrated polymer systems. While octane diffusion shows no cross-link dependence, the larger dyes are increasingly restricted by fixed chemical meshes. The simple Fujita free-volume theory proved most feasible to describe probe diffusion in linear long-chain solutions with realistic parameters, while better fits were obtained assuming a stretched exponential dependence on concentration. Importantly, we have analyzed the cross-link specific effect on probe diffusion independently of any specific model by comparing the best-fit interpolation of the solution data with the diffusion in the networks. The most reasonable description is obtained by assuming that the cross-link effect is additive in the effective friction coefficient of the probes. The concentration dependences as well as the data compared at the equilibrium degrees of swelling indicate that swelling heterogeneities and diffusant shape have a substantial influence on small-molecule diffusion in networks.

2009-01-01

325

Molecular areas of phospholipids as determined by 2H NMR spectroscopy. Comparison of phosphatidylethanolamines and phosphatidylcholines  

SciTech Connect

The role of lipid diversity in biomembranes is one of the major unsolved problems in biochemistry. One parameter of possible importance is the mean cross-sectional area occupied per lipid molecule, which may be related to formation of nonbilayer structures and membrane protein function. We have used {sup 2}H NMR spectroscopy to compare the properties of 1,2-diperdeuteriopalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE-d62) and 1,2-diperdeuteriopalmitoyl-sn-glycero-3-phosphocholine (DPPC-d62) in the L alpha phase. We find that DPPE has greater segmental order than DPPC, and that this increase in order is related to the smaller area per acyl chain found for DPPE. Values of the mean cross-sectional chain area are calculated using a simple diamond lattice model for the acyl chain configurational statistics, together with dilatometry data. The results obtained for the mean area per molecule are comparable with those from low angle x-ray diffraction studies.

Thurmond, R.L.; Dodd, S.W.; Brown, M.F. (Univ. of Arizona, Tucson (USA))

1991-01-01

326

On the role of NMR spectroscopy for characterization of antimicrobial peptides.  

PubMed

Antimicrobial peptides (AMPs) provide a primordial source of immunity, conferring upon eukaryotic cells resistance against bacteria, protozoa, and viruses. Despite a few examples of anionic peptides, AMPs are usually relatively short positively charged polypeptides, consisting of a dozen to about a hundred amino acids, and exhibiting amphipathic character. Despite significant differences in their primary and secondary structures, all AMPs discovered to date share the ability to interact with cellular membranes, thereby affecting bilayer stability, disrupting membrane organization, and/or forming well-defined pores. AMPs selectively target infectious agents without being susceptible to any of the common pathways by which these acquire resistance, thereby making AMPs prime candidates to provide therapeutic alternatives to conventional drugs. However, the mechanisms of AMP actions are still a matter of intense debate. The structure-function paradigm suggests that a better understanding of how AMPs elicit their biological functions could result from atomic resolution studies of peptide-lipid interactions. In contrast, more strict thermodynamic views preclude any roles for three-dimensional structures. Indeed, the design of selective AMPs based solely on structural parameters has been challenging. In this chapter, we will focus on selected AMPs for which studies on the corresponding AMP-lipid interactions have helped reach an understanding of how AMP effects are mediated. We will emphasize the roles of both liquid- and solid-state NMR spectroscopy for elucidating the mechanisms of action of AMPs. PMID:23975777

Porcelli, Fernando; Ramamoorthy, Ayyalusamy; Barany, George; Veglia, Gianluigi

2013-01-01

327

Conformational studies of neurohypophyseal hormones analogues with glycoconjugates by NMR spectroscopy.  

PubMed

Two glycosylated peptides have been studied using NMR spectroscopy supported by molecular modeling. Peptide I is an oxytocin (OT) analogue in which glutamine 4 was replaced by serine with attached ?-d-mannose through the oxygen ? atom, whereas peptide II is a lysine-vasopressin (LVP) analogue with lysine 8 side chain modified by the attachment of glucuronic acid through an amide bond. Both peptides exhibit very weak uterotonic effect and are less susceptible to proteolytic degradation than the mother hormones. Additionally, peptide II reveals very weak pressor and antidiuretic activities. Our results have shown that the conformational preferences of glycosylated analogues are highly similar to those of their respective mother hormones. OT glycosylated analogue (I) exhibits a 3,4 ?-turn characteristic of OT-like peptides, and vasopressin-glycosylated analogue (II) exhibits??-turns typical of vasopressin-like peptides. Therefore, the lack of binding of the glycosylated analogues to the receptors can be attributed to a steric interference between the carbohydrate moieties and the receptors. We also consider this to be the reason of the very low activity of the analyzed glycopeptides. We expect that results from these studies will be helpful in designing new OT-like and vasopressin-like drugs. PMID:24644276

Lubecka, Emilia A; Sikorska, Emilia; Marcinkowska, Alina; Ciarkowski, Jerzy

2014-06-01

328

Metabolic changes during cellular senescence investigated by proton NMR-spectroscopy.  

PubMed

Cellular senescence is of growing interest due to its role in tumour suppression and its contribution to organismic ageing. This cellular state can be reached by replicative loss of telomeres or certain stresses in cell culture and is characterized by the termination of cell division; however, the cells remain metabolically active. To identify metabolites that are characteristic for senescent cells, extracts of human embryonic lung fibroblast (WI-38 cell line) have been investigated with NMR spectroscopy. Three different types of senescence have been characterized: replicative senescence, DNA damage-induced senescence (etoposide treatment) and oncogene-induced senescence (hyperactive RAF kinase). The metabolite pattern allows (I) discrimination of senescent and control cells and (II) discrimination of the three senescence types. Senescent cells show an increased ratio of glycerophosphocholine to phosphocholine independent from the type of senescence. The increase in glycerophosphocholine implicates a key role of phospholipid metabolism in cellular senescence. The observed changes in the choline metabolism are diametrically opposite to the well-known changes in choline metabolism of tumour cells. As tumours responding to chemotherapeutic agents show a "glycerophosphocholine-to-phosphocholine switch" i.e. an increase in glycerophosphocholine, our metabolic data suggests that these malignant cells enter a senescent state emphasizing the role of senescence in tumour suppression. PMID:23416267

Gey, Claudia; Seeger, Karsten

2013-03-01

329

NMR Spectroscopy of Macrophages Loaded with Native, Oxidized or Enzymatically Degraded Lipoproteins  

PubMed Central

Oxidized and enzymatically modified low-density lipoproteins (oxLDL and eLDL) play a key role in early stages of atherogenesis. Their uptake by recruited macrophages leads to endolysosomal phospholipidosis or foam cell formation, respectively, each of which is preceded by highly differential lipid restructuring processes. We applied 1H-NMR spectroscopy (NMRS) to elucidate these structural rearrangements both in consequence of lipoprotein modifications and following phagocytosis. Being specifically sensitive to the mobile lipid subset, NMRS of oxLDL and eLDL revealed a partial and total immobilization of lipids, respectively. NMRS of intact macrophages showed a sixfold increase in mobile lipids in case of loading with eLDL but no significant changes for oxLDL or native LDL. This finding reflected the disparate lipid storage in lipid droplets and in multilamellar endolysosomal clusters when loaded with either eLDL or oxLDL, respectively. Moreover, a significant shift of the degree of saturation towards mainly polyunsaturated fatty acid chains was found for the mobile lipid pool in eLDL-loaded macrophages. Additional analyses of lipid extracts by NMRS and mass spectrometry (MS) reflected these changes in lipid content and in fatty acid composition only partially. In summary, in-cell NMRS represents a unique lipidomics tool to investigate structural changes within the mobile lipid pool following atherogenic triggers that can be not detected by the analysis of lipid extracts by MS or NMRS.

Ramm Sander, Paul; Peer, Markus; Grandl, Margot; Bogdahn, Ulrich; Schmitz, Gerd; Kalbitzer, Hans Robert

2013-01-01

330

NMR spectroscopy of macrophages loaded with native, oxidized or enzymatically degraded lipoproteins.  

PubMed

Oxidized and enzymatically modified low-density lipoproteins (oxLDL and eLDL) play a key role in early stages of atherogenesis. Their uptake by recruited macrophages leads to endolysosomal phospholipidosis or foam cell formation, respectively, each of which is preceded by highly differential lipid restructuring processes. We applied (1)H-NMR spectroscopy (NMRS) to elucidate these structural rearrangements both in consequence of lipoprotein modifications and following phagocytosis. Being specifically sensitive to the mobile lipid subset, NMRS of oxLDL and eLDL revealed a partial and total immobilization of lipids, respectively. NMRS of intact macrophages showed a sixfold increase in mobile lipids in case of loading with eLDL but no significant changes for oxLDL or native LDL. This finding reflected the disparate lipid storage in lipid droplets and in multilamellar endolysosomal clusters when loaded with either eLDL or oxLDL, respectively. Moreover, a significant shift of the degree of saturation towards mainly polyunsaturated fatty acid chains was found for the mobile lipid pool in eLDL-loaded macrophages. Additional analyses of lipid extracts by NMRS and mass spectrometry (MS) reflected these changes in lipid content and in fatty acid composition only partially. In summary, in-cell NMRS represents a unique lipidomics tool to investigate structural changes within the mobile lipid pool following atherogenic triggers that can be not detected by the analysis of lipid extracts by MS or NMRS. PMID:23457556

Ramm Sander, Paul; Peer, Markus; Grandl, Margot; Bogdahn, Ulrich; Schmitz, Gerd; Kalbitzer, Hans Robert

2013-01-01

331

Amino acid conservation and interactions in rhodopsin: probing receptor activation by NMR spectroscopy.  

PubMed

Rhodopsin is a classical two-state G protein-coupled receptor (GPCR). In the dark, its 11-cis retinal chromophore serves as an inverse agonist to lock the receptor in an inactive state. Retinal-protein and protein-protein interactions have evolved to reduce the basal activity of the receptor in order to achieve low dark noise in the visual system. In contrast, absorption of light triggers rapid isomerization of the retinal, which drives the conversion of the receptor to a fully active conformation. Several specific protein-protein interactions have evolved that maintain the lifetime of the active state in order to increase the sensitivity of this receptor for dim-light vision in vertebrates. In this article, we review the molecular interactions that stabilize rhodopsin in the dark-state and describe the use of solid-state NMR spectroscopy for probing the structural changes that occur upon light-activation. Amino acid conservation provides a guide for those interactions that are common in the class A GPCRs as well as those that are unique to the visual system. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks. PMID:24183693

Pope, Andreyah; Eilers, Markus; Reeves, Philip J; Smith, Steven O

2014-05-01

332

Single-Step analysis of individual conjugated bile acids in human bile using 1 H NMR spectroscopy  

Microsoft Academic Search

1H and 13C NMR spectra of intact human bile were assigned using one-dimensional (1H and 13C) and two-dimensional (1H-1H and 1H-13C) experiments. Individual conjugated bile acids—glycocholic acid, glycodeoxycholic acid, glycochenodeoxycholic acid, taurocholic\\u000a acid, taurodeoxycholic acid, and taurochenodeoxycholic acid—were identified. The bile acids were quantified accurately and\\u000a individually in a single step by using distinct and characteristic amide signals. Making use

G. A. Nagana Gowda; Omkar B. Ijare; B. S. Somashekar; Ajay Sharma; V. K. Kapoor; C. L. Khetrapal

2006-01-01

333

Metabolic analysis of elicited cell suspension cultures of Cannabis sativa L. by 1 H-NMR spectroscopy  

Microsoft Academic Search

Cannabis sativa L. plants produce a diverse array of secondary metabolites. Cannabis cell cultures were treated with jasmonic acid (JA) and\\u000a pectin as elicitors to evaluate their effect on metabolism from two cell lines using NMR spectroscopy and multivariate data\\u000a analysis. According to principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA), the chloroform\\u000a extract of the pectin-treated cultures

Jaroslav Pe?; Isvett Josefina Flores-Sanchez; Young Hae Choi; Robert Verpoorte

2010-01-01

334

Determination of the time course of an enzymatic reaction by 1H NMR spectroscopy: hydroxynitrile lyase catalysed transhydrocyanation  

NASA Astrophysics Data System (ADS)

The time course of the enzyme catalysed transhydrocyanation of benzaldehyde to give ( S)-mandelonitrile was investigated using a hydroxynitrile lyase from Hevea brasiliensis as catalyst and acetone cyanohydrin as cyanide donor. Employing special techniques it was possible to apply 1H NMR spectroscopy in aqueous medium to monitor the concentration changes of all substrates and products. By this technique strong evidence for inhibition of the enzyme at higher substrate concentrations was obtained.

Hickel, A.; Gradnig, G.; Griengl, H.; Schall, M.; Sterk, H.

1996-01-01

335

Organophosphates in agrogray soils with periodic water logging according to the data of 31 P NMR spectroscopy  

Microsoft Academic Search

The composition of organic phosphorus compounds was studied using the 31P NMR spectroscopy method in agrogray soils with periodic water logging. The phosphorus content was determined by the specific\\u000a difference between the hydrological and the redox regimes of these soils. The phosphorus of the organic compounds in the agrogray\\u000a soils with contrasting water regimes is composed mostly of phosphoric monoesters

I. V. Kovalev; N. O. Kovaleva

2011-01-01

336

Solid state NMR spectroscopy investigation of the molecular structure of epoxy based materials cured in different conditions  

NASA Astrophysics Data System (ADS)

In this work two epoxy resin model systems, whose monomers are typically used in structural composites, were thermally cured in different cure conditions in order to obtain different cross-linking densities. Their molecular structures were investigated through solid state NMR spectroscopy in order to correlate them to the cure process conditions used and the results were discussed in the light of the dynamical mechanical thermal analysis (DMTA) performed.

Alessi, S.; Spinella, A.; Caponetti, E.; Sabatino, Maria Antonietta; Spadaro, G.

2012-07-01

337

Determination of full 13C isotopomer distributions for metabolic flux analysis using heteronuclear spin echo difference NMR spectroscopy  

Microsoft Academic Search

13C-isotopomer labeling experiments play an increasingly important role in the analysis of intracellular metabolic fluxes for genetic engineering purposes. 13C NMR spectroscopy is a key technique in the experimental determination of isotopomer distributions. However, only subsets of isotopomers can be quantitated using this technique due to redundancies in the scalar coupling patterns and due to invisibility of the 12C isotope

Albert A de Graaf; Matthias Mahle; Michael Möllney; Wolfgang Wiechert; Peter Stahmann; Hermann Sahm

2000-01-01

338

CP\\/MAS [sup 89]Y NMR spectroscopy: A facile method for characterizing yttrium-containing solids  

Microsoft Academic Search

Solid state CP\\/MAS [sup 89]Y NMR spectroscopy, which had previously been limited to air stable materials containing solvated water, has been extended to a series of air sensitive yttrium complexes with a chemical shift range of over 1,000 ppm. The results of this study demonstrate that [sup 89]Y CP\\/MAS spectra can be easily obtained on a broad range of complexes

Jiejun Wu; T. J. Boyle; J. L. Shreeve; J. W. Ziller; W. J. Evans

1993-01-01

339

Structural investigations of tungsten silver phosphate glasses by solid state NMR, vibrational and X-ray absorption near edge spectroscopies  

Microsoft Academic Search

Glasses were prepared in the pseudo-binary system (1?x)AgPO3–xWO3 (0?×?0.6mol%). The structural evolution of the vitreous network was studied as a function of composition by thermal analysis, Fourier Transform Infrared spectroscopy (FTIR), Raman scattering, high resolution 31P solid state NMR and XANES at the W-L1 absorption edge. For compositions with x ranging from 0 to 0.5 a pronounced increase in the

Silvia H. Santagneli; Gaël Poirier; Matthias T. Rinke; Sidney J. L. Ribeiro; Younes Messaddeq; Hellmut Eckert

2011-01-01

340

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

Microsoft Academic Search

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

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

1992-01-01

341

Flow-Through Lipid Nanotube Arrays for Structure-Function Studies of Membrane Proteins by Solid-State NMR Spectroscopy  

Microsoft Academic Search

A novel method for studying membrane proteins in a native lipid bilayer environment by solid-state NMR spectroscopy is described and tested. Anodic aluminum oxide (AAO) substrates with flow-through 175nm wide and 60-?m-long nanopores were employed to form macroscopically aligned peptide-containing lipid bilayers that are fluid and highly hydrated. We demonstrate that the surfaces of both leaflets of such bilayers are

Eduard Y. Chekmenev; Peter L. Gor’kov; Timothy A. Cross; Ali M. Alaouie; Alex I. Smirnov

2006-01-01

342

1H\\/ 15N Heteronuclear NMR Spectroscopy Shows Four Dynamic Domains for Phospholamban Reconstituted in Dodecylphosphocholine Micelles  

Microsoft Academic Search

We report the backbone dynamics of monomeric phospholamban in dodecylphosphocholine micelles using 1H\\/15N heteronuclear NMR spectroscopy. Phospholamban is a 52-amino acid membrane protein that regulates Ca-ATPase in cardiac muscle. Phospholamban comprises three structural domains: a transmembrane domain from residues 22 to 52, a connecting loop from 17 to 21, and a cytoplasmic domain from 1 to 16 that is organized

Emily E. Metcalfe; Jamillah Zamoon; David D. Thomas; Gianluigi Veglia

2004-01-01

343

Homogeneous hydrogenation of norbornadiene with parahydrogen and phosphonic ester phosphine rhodium complexes studied by in situ nmr spectroscopy  

Microsoft Academic Search

1) Homogeneous hydrogenation of norbornadiene with enriched parahydrogen (p-H2) and phosphonic ester phosphine rhodium complexes is detected using in situ NMR spectroscopy The obtained polarization spectra remain unchanged during the catalysis in thf-d8 as a solvent but change with time when the hydrogenation is executed in acetone-d6. 2) The observed phenomenon is attributed to a change of the phase correlation

A Weigt; K WOELK; J BARGON

1995-01-01

344

1H NMR spectroscopy reveals that mouse Hsp25 has a flexible C-terminal extension of 18 amino acids  

Microsoft Academic Search

The small heat-shock proteins (Hsps) exist as large aggregates and function by interacting and stabilising non-native proteins in a chaperone-like manner. Two-dimensional 1H NMR spectroscopy of mouse Hsp25 reveals that the last 18 amino acids have great flexibility with motion that is essentially independent of the domain core of the protein. The lens protein, ?-crystallin, is homologous to Hsp25 and

John A. Carver; Gennaro Esposito; Gabriele Schwedersky; Matthias Gaestel

1995-01-01

345

Complexation of daunomycin with a DNA oligomer in the presence of an aromatic vitamin (B 2) determined by NMR spectroscopy  

Microsoft Academic Search

The effect of simultaneous binding of the anthracycline antibiotic Daunomycin (DAU) and the Vitamin B2 derivative, Flavin-mononucleotide (FMN), with the DNA oligomer, d(TGCA)2, in solution has been investigated quantitatively by 1Í-NMR spectroscopy (500 MHz). The equilibrium reaction constants and the thermodynamical parameters (?H, ?S) of the hetero-association FMN-DAU and complexation of FMN with d(TGCA)2 have been determined by analysis of

M. P. Evstigneev; Yu. V. Mykhina; D. B. Davies

2005-01-01

346

Electronic Structure, Chemical Bonding, and Solid-State NMR Spectroscopy of the Digallides of Ca, Sr, and Ba  

Microsoft Academic Search

Combined application of 69,71 Ga NMR spectroscopy and quan- tum mechanical calculations reveals the chemical bonding in the digallides of Ca, Sr, and Ba. An analysis of the electron localization function (ELF) shows honeycomb-like 63 nets of the Ga atoms as the most prominent struc- tural features in SrGa2 and BaGa2 .F or CaGa2 a description of a 3+1-coordi- nated

Frank Haarmann; Katrin Koch; Daniel Grner; Walter Schnelle; Oliver Pecher; Raul Cardoso-Gil; Horst Borrmann; Helge Rosner; Yuri Grin

2009-01-01

347

Phosphinoamino complexes of copper(I) and silver(I): a combined NMR and IR spectroscopy, and electrospray ionization and fast atom bombardment mass spectrometry analysis  

Microsoft Academic Search

Bidentate ‘PN’ and tetradentate ‘P2N2’ ligands from stable silver(1) complexes, which were characterized by NMR and IR spectroscopy. Conductivity measurements indicate an ionic nature of the compounds in solution. A thorough mass spectrometric study (electrospray ionization and fast atom bombardment) of these complexes and the corresponding Cu(1) analogues supports the NMR and IR structural information.

Laura Crociani; Roberto Anacardio; Pietro Traldi; Benedetto Corain

1998-01-01

348

COVALENT BINDING OF REDUCED METABOLITES OF [15N3] TNT TO SOIL ORGANIC MATTER DURING A BIOREMEDIATION PROCESS ANALYZED BY 15N NMR SPECTROSCOPY. (R826646)  

EPA Science Inventory

Evidence is presented for the covalent binding of biologically reduced metabolites of 2,4,6-15N3-trinitrotoluene (TNT) to different soil fractions (humic acids, fulvic acids, and humin) using liquid 15N NMR spectroscopy. A silylation p...

349

Human in vivo cardiac phosphorus NMR spectroscopy at 3.0 Tesla  

NASA Astrophysics Data System (ADS)

One of the newest methods with great potential for use in clinical diagnosis of heart disease is human, cardiac, phosphorus NMR spectroscopy (cardiac p 31 MRS). Cardiac p31 MRS is able to provide quantitative, non-invasive, functional information about the myocardial energy metabolites such as pH, phosphocreatine (PCr), and adenosinetriphosphate (ATP). In addition to the use of cardiac p3l MRS for other types of cardiac problems, studies have shown that the ratio of PCr/ATP and pH are sensitive and specific markers of ischemia at the myocardial level. In human studies, typically performed at 1.5 Tesla, PCr/ATP has been relatively easy to measure but often requires long scan times to provide adequate signal-to-noise (SNR). In addition, pH which relies on identification of inorganic phosphate (Pi), has rarely been obtained. Significant improvement in the quality of cardiac p31 MRS was achieved through the use of the General Electric SIGNATM 3.0 Tesla whole body magnet, improved coil designs and optimized pulse sequences. Phantom and human studies performed on many types of imaging and spectroscopy sequences, identified breathhold gradient-echo imaging and oblique DRESS p31 spectroscopy as the best compromises between SNR, flexibility and quality localization. Both single-turn and quadrature 10-cm diameter, p31 radiofrequency coils, were tested with the quadrature coil providing greater SNR, but at a greater depth to avoid skeletal muscle contamination. Cardiac p31 MRS obtained in just 6 to 8 minutes, gated, showed both improved SNR and discernment of Pi allowing for pH measurement. A handgrip, in-magnet exerciser was designed, created and tested at 1.5 and 3.0 Tesla on volunteers and patients. In ischemic patients, this exercise was adequate to cause a repeated drop in PCr/ATP and pH with approximately eight minutes of isometric exercise at 30% maximum effort. As expected from literature, this exercise did not cause a drop in PCr/ATP for reference volunteers.

Bruner, Angela Properzio

350

High sensitivity 1H-NMR spectroscopy of homeopathic remedies made in water  

PubMed Central

Background The efficacy of homeopathy is controversial. Homeopathic remedies are made via iterated shaking and dilution, in ethanol or in water, from a starting substance. Remedies of potency 12 C or higher are ultra-dilute (UD), i.e. contain zero molecules of the starting material. Various hypotheses have been advanced to explain how a UD remedy might be different from unprepared solvent. One such hypothesis posits that a remedy contains stable clusters, i.e. localized regions where one or more hydrogen bonds remain fixed on a long time scale. High sensitivity proton nuclear magnetic resonance spectroscopy has not previously been used to look for evidence of differences between UD remedies and controls. Methods Homeopathic remedies made in water were studied via high sensitivity proton nuclear magnetic resonance spectroscopy. A total of 57 remedy samples representing six starting materials and spanning a variety of potencies from 6 C to 10 M were tested along with 46 controls. Results By presaturating on the water peak, signals could be reliably detected that represented H-containing species at concentrations as low as 5 ?M. There were 35 positions where a discrete signal was seen in one or more of the 103 spectra, which should theoretically have been absent from the spectrum of pure water. Of these 35, fifteen were identified as machine-generated artifacts, eight were identified as trace levels of organic contaminants, and twelve were unexplained. Of the unexplained signals, six were seen in just one spectrum each. None of the artifacts or unexplained signals occurred more frequently in remedies than in controls, using a p < .05 cutoff. Some commercially prepared samples were found to contain traces of one or more of these small organic molecules: ethanol, acetate, formate, methanol, and acetone. Conclusion No discrete signals suggesting a difference between remedies and controls were seen, via high sensitivity 1H-NMR spectroscopy. The results failed to support a hypothesis that remedies made in water contain long-lived non-dynamic alterations of the H-bonding pattern of the solvent.

Anick, David J

2004-01-01

351

SIMPSON: A General Simulation Program for Solid-State NMR Spectroscopy  

Microsoft Academic Search

A computer program for fast and accurate numerical simulation of solid-state NMR experiments is described. The program is designed to emulate a NMR spectrometer by letting the user specify high-level NMR concepts such as spin systems, nuclear spin interactions, RF irradiation, free precession, phase cycling, coherence-order filtering, and implicit\\/explicit acquisition. These elements are implemented using the Tcl scripting language to

Mads Bak; Jimmy T. Rasmussen; Niels Chr Nielsen

2000-01-01

352

Exploring abiotic stress on asynchronous protein metabolism in single kernels of wheat studied by NMR spectroscopy and chemometrics.  

PubMed

Extreme climate events are being recognized as important factors in the effects on crop growth and yield. Increased climatic variability leads to more frequent extreme conditions which may result in crops being exposed to more than one extreme event within a growing season. The aim of this study was to examine the implications of different drought treatments on the protein fractions in grains of winter wheat using (1)H nuclear magnetic resonance spectroscopy followed by chemometric analysis. Triticum aestivum L. cv. Vinjett was studied in a semi-field experiment and subjected to drought episodes either at terminal spikelet, during grain-filling or at both stages. Principal component trajectories of the total protein content and the protein fractions of flour as well as the (1)H NMR spectra of single wheat kernels, wheat flour, and wheat methanol extracts were analysed to elucidate the metabolic development during grain-filling. The results from both the (1)H NMR spectra of methanol extracts and the (1)H HR-MAS NMR of single kernels showed that a single drought event during the generative stage had as strong an influence on protein metabolism as two consecutive events of drought. By contrast, a drought event at the vegetative growth stage had little effect on the parameters investigated. For the first time, (1)H HR-MAS NMR spectra of grains taken during grain-filling were analysed by an advanced multiway model. In addition to the results from the chemical protein analysis and the (1)H HR-MAS NMR spectra of single kernels indicating that protein metabolism is influenced by multiple drought events, the (1)H NMR spectra of the methanol extracts of flour from mature grains revealed that the amount of fumaric acid is particularly sensitive to water deficits. PMID:19213725

Winning, H; Viereck, N; Wollenweber, B; Larsen, F H; Jacobsen, S; Sřndergaard, I; Engelsen, S B

2009-01-01

353

Synthesis of silver(I) complexes of thiones and their characterization by 13C, 15N and 107Ag NMR spectroscopy  

Microsoft Academic Search

Silver(I) complexes of thiones (L), [LAgNO3] and [AgL2]NO3 have been prepared and characterized by elemental analysis, IR and NMR (1H, 13C, 15N and 107Ag) spectroscopy. An upfield shift in the C?S resonance of thiones in 13C NMR and downfield shifts in N?H resonances in 1H and 15N NMR are consistent with the sulfur coordination to silver(I). In 107Ag NMR, the

Anvarhusein A Isab; Saeed Ahmad; Mohammed Arab

2002-01-01

354

Investigation of interaction parameters in mixed micelle using pulsed field gradient NMR spectroscopy.  

PubMed

Pulsed field gradient NMR spectroscopy was used to determine the partitioning of surfactant between monomeric and micellar forms in a mixed CTAB (hexadecyltetramethylammonium bromide) and Triton X-100 [p-(1,1,3-tetramethylbutyl)polyoxyethylene] system. In addition, potentiometric and surface tension measurements were used to determine the free concentration of ionic surfactant and the critical micelle concentration (CMC) of mixtures of n-alkyltrimethylammonium bromide (C(n)TAB, n=12, 14, 16, 18) and Triton X-100. Regular solution theory cannot describe the behavior of the activity coefficient and the excess Gibbs free energy of mixtures of ionic and nonionic surfactants. To overcome these shortcomings, we developed a new model that combines Van Laar expressions and the theory of nonrandom mixing in mixed micelles. The Van Laar expressions contain an additional parameter, rho, which reflects differences in the size of the components of the mixture. Nonrandom mixing theory was introduced to describe nonrandom mixing in mixed micelles. This effect was modeled by a packing parameter, P*. The proposed model provided a good description of the behavior of binary surfactant mixtures. The results indicated that head group size and packing constraints are important contributors to nonideal surfactant behavior. In addition, the results showed that as the chain length of the C(n)TAB molecule in C(n)TAB/Triton X-100 mixtures was increased, the head group size parameter remained constant, but the interaction and packing parameters increased. Increase of the temperature caused an increase in the interaction parameter beta and a decrease in the packing parameter (P*). PMID:15797433

Gharibi, H; Javadian, S; Sohrabi, B; Behjatmanesh, R

2005-05-01

355

Free amino acid turnover in methanogens measured by 15N NMR spectroscopy.  

PubMed

Turnover of the nitrogen moiety from free amino acid pools in two thermophilic methanogens, Methanobacterium thermautotrophicum delta H and Methanococcus thermolithotrophicus SN1, has been monitored with 15N NMR spectroscopy. In cells growing exponentially on 15NH4Cl, glutamate was the major soluble 15N-labeled species in both organisms. When the Mb. thermoautotrophicum cells were harvested, washed, and resuspended into medium containing 14NH4Cl, the resonance for [15N]glutamate decreased with a half-life of 0.5 h. This is considerably faster than the turnover rate for the carbon side chain of glutamate (7 h) obtained when a 13CO2 pulse followed by a 12CO2 chase was incorporated into the 15N/14N-labeling experiment. Such behavior is consistent with recycling of the glutamate carbon skeleton via alpha-ketoglutarate after transamination reactions remove the 15N for biosynthesis of other amino acids, nucleic acids, etc. When the cells were in stationary phase, 15N turnover was considerably slower indicating that transaminase activity had also decreased. Mc. thermolithotrophicus has a much more fragile cell wall and easily lyses. To avoid cell loss in the 15N/14N experiment, 15NH+4 growth followed by 14NH4+ dilution was used. In this organism the glutamate-labeled nitrogen turns over quite rapidly (t1/2 approximately 9 min), at a rate comparable to that for the carbon skeleton (t1/2 approximately 10 min). Beta-Glutamate, the second major carbon and nitrogen pool in this organism, turns over its 15N label very slowly. Therefore, this beta-amino acid does not appear to serve as a nitrogen donor in Mc. thermolithotrophicus. PMID:2211697

Roberts, M F; Choi, B S; Robertson, D E; Lesage, S

1990-10-25

356

Phosphorus speciation in a eutrophic lake by (31)P NMR spectroscopy.  

PubMed

For eutrophic lakes, patterns of phosphorus (P) measured by standard methods are well documented but provide little information about the components comprising standard operational definitions. Dissolved P (DP) and particulate P (PP) represents important but rarely characterized nutrient pools. Samples from Lake Mendota, Wisconsin, USA were characterized using 31-phosphorus nuclear magnetic resonance spectroscopy ((31)P NMR) during the open water season of 2011 in this unmatched temporal study of aquatic P dynamics. A suite of organic and inorganic P forms was detected in both dissolved and particulate fractions: orthophosphate, orthophosphate monoesters, orthophosphate diesters, pyrophosphate, polyphosphate, and phosphonates. Through time, phytoplankton biomass, temperature, dissolved oxygen, and water clarity were correlated with changes in the relative proportion of P fractions. Particulate P can be used as a proxy for phytoplankton-bound P, and in this study, a high proportion of polyphosphate within particulate samples suggested P should not be a limiting factor for the dominant primary producers, cyanobacteria. Hypolimnetic particulate P samples were more variable in composition than surface samples, potentially due to varying production and transport of sinking particles. Surface dissolved samples contained less P than particulate samples, and were typically dominated by orthophosphate, but also contained monoester, diester, polyphosphate, pyrophosphate, and phosphonate. Hydrologic inflows to the lake contained more orthophosphate and orthophosphate monoesters than in-lake samples, indicating transformation of P from inflowing waters. This time series explores trends of a highly regulated nutrient in the context of other water quality metrics (chlorophyll, mixing regime, and clarity), and gives insight on the variability of the structure and occurrence of P-containing compounds in light of the phosphorus-limited paradigm. PMID:24956605

Read, Emily K; Ivancic, Monika; Hanson, Paul; Cade-Menun, Barbara J; McMahon, Katherine D

2014-10-01

357

Organic Spectroscopy Laboratory: Utilizing IR and NMR in the Identification of an Unknown Substance  

ERIC Educational Resources Information Center

A laboratory experiment that emphasizes the interpretation of both infrared (IR) and nuclear magnetic resonance (NMR) spectra in the elucidation of the structure of an unknown compound was developed. The method helps students determine [to the first power]H- and [to the thirteenth power]C-NMR spectra from the structures of compounds and to…

Glagovich, Neil M.; Shine, Timothy D.

2005-01-01

358

Probing the association of fluorobenzene with dissolved organic matter using NMR spectroscopy  

Microsoft Academic Search

We dissolved and fractionated the commercially available Aldrich humic acid (AHA) into less than 1000 and less than 8000 atomic mass unit (amu) fractions and used 1H NMR to analyze the chemical forms of dissolved organic matter (DOM) of these two AHA fractions in D2O. The range of linewidths of the signals observed in the 1H NMR spectra of the

Zeina R. Hinedi; Andrew C. Chang; Daniel B. Borchardt

1997-01-01

359

Enantiomeric analysis using natural abundance deuterium 3D NMR spectroscopy in polypeptide chiral oriented media  

NASA Astrophysics Data System (ADS)

The use of natural abundance deuterium (NAD) three-dimensional (3D) NMR experiment in chiral liquid crystals (CLC) is reported and discussed. This homonuclear autocorrelation 3D experiment allows assigning deuterium signals of weakly aligned molecules at natural isotopic abundance. It provides an efficient strategy for identifying the spectral enantio-discriminations on NAD spectra. We demonstrate that NAD 3D NMR is feasible within reasonable experimental times (14 h) using the 3D Quadrupole Double-Quantum NMR sequence [O. Lafon, P. Lesot, Chem. Phys. Lett. 404 (2005) 90] and a 14.1 T NMR spectrometer equipped with a selective 5 mm deuterium NMR cryoprobe. The analytical potentialities of this technique are illustrated in the case of (ą)-but-2-yn-1-ol dissolved in poly-?-benzyl- L-glutamate/CHCl 3 mesophase.

Lesot, Philippe; Lafon, Olivier

2008-06-01

360

Dissolution mechanism of crystalline cellulose in H3PO4 as assessed by high-field NMR spectroscopy and fast field cycling NMR relaxometry.  

PubMed

Many processes have been proposed to produce glucose as a substrate for bacterial fermentation to obtain bioethanol. Among others, cellulose degradation appears as the most convenient way to achieve reliable amounts of glucose units. In fact, cellulose is the most widespread biopolymer, and it is considered also as a renewable resource. Due to extended intra- and interchain hydrogen bonds that provide a very efficient packing structure, however, cellulose is also a very stable polymer, the degradation of which is not easily achievable. In the past decade, researchers enhanced cellulose reactivity by increasing its solubility in many solvents, among which concentrated phosphoric acid (H(3)PO(4)) played the major role because of its low volatility and nontoxicity. In the present study, the solubilization mechanism of crystalline cellulose in H(3)PO(4) has been elucidated by using high- and low-field NMR spectroscopy. In particular, high-field NMR spectra showed formation of direct bonding between phosphoric acid and dissolved cellulose. On the other hand, molecular dynamics studies by low-field NMR with a fast field cycling (FFC) setup revealed two different H(3)PO(4) relaxing components. The first component, described by the fastest longitudinal relaxation rate (R(1)), was assigned to the H(3)PO(4) molecules bound to the biopolymer. Conversely, the second component, characterized by the slowest R(1), was attributed to the bulk solvent. The understanding of cellulose dissolution in H(3)PO(4) represents a very important issue because comprehension of chemical mechanisms is fundamental for process ameliorations to produce bioenergy from biomasses. PMID:19769370

Conte, Pellegrino; Maccotta, Antonella; De Pasquale, Claudio; Bubici, Salvatore; Alonzo, Giuseppe

2009-10-14

361

Analyzing the adsorption of blood plasma components by means of fullerene-containing silica gels and NMR spectroscopy in solids  

NASA Astrophysics Data System (ADS)

The results from studying the adsorption of blood plasma components (e.g., protein, triglycerides, cholesterol, and lipoproteins of low and high density) using silica gels modified with fullerene molecules (in the form of C60 or the hydroxylated form of C60(OH) x ) and subjected to hydration (or, alternatively, dehydration) are presented. The conditions for preparing adsorbents that allow us to control the adsorption capacity of silica gel and the selectivity of adsorption toward the components of blood plasma, are revealed. The nature and strength of the interactions of the introduced components (fullerene molecules and water) with functional groups on the silica surface are studied by means of solid state NMR spectroscopy (NMR-SS). Conclusions regarding the nature of the centers that control adsorption are drawn on the basis of NMR-SS spectra in combination with direct measurements of adsorption. The interaction of the oxygen of the hydroxyl group of silica gel with fullerene, leading to the formation of electron-donor complexes of C60-H, C60-OH, or C60-OSi type, is demonstrated by the observed changes in the NMR-SS spectra of silica gels in the presence of fullerene.

Melenevskaya, E. Yu.; Mokeev, M. V.; Nasonova, K. V.; Podosenova, N. G.; Sharonova, L. V.; Gribanov, A. V.

2012-10-01

362

Adducts of nitrogenous ligands with rhodium(II) tetracarboxylates and tetraformamidinate: NMR spectroscopy and density functional theory calculations.  

PubMed

Complexation of tetrakis(?2-N,N'-diphenylformamidinato-N,N')-di-rhodium(II) with ligands containing nitrile, isonitrile, amine, hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups has been studied in liquid and solid phases using (1)H, (13)C and (15)N NMR, (13)C and (15)N cross polarisation-magic angle spinning NMR, and absorption spectroscopy in the visible range. The complexation was monitored using various NMR physicochemical parameters, such as chemical shifts, longitudinal relaxation times T1 , and NOE enhancements. Rhodium(II) tetraformamidinate selectively bonded only unbranched amine (propan-1-amine), pentanenitrile, and (1-isocyanoethyl)benzene. No complexation occurred in the case of ligands having hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups, and more expanded amine molecules such as butan-2-amine and 1-azabicyclo[2.2.2]octane. Such features were opposite to those observed in rhodium(II) tetracarboxylates, forming adducts with all kind of ligands. Special attention was focused on the analysis of ?? parameters, defined as a chemical shift difference between signal in adduct and corresponding signal in free ligand. In the case of (1)H NMR, ?? values were either negative in adducts of rhodium(II) tetraformamidinate or positive in adducts of rhodium(II) tetracarboxylates. Experimental findings were supported by density functional theory molecular modelling and gauge independent atomic orbitals chemical shift calculations. The calculation of chemical shifts combined with scaling procedure allowed to reproduce qualitatively ?? parameters. PMID:24327228

Cmoch, Piotr; G?aszczka, Rafa?; Ja?wi?ski, Jaros?aw; Kamie?ski, Bohdan; Senkara, El?bieta

2014-03-01

363

Simultaneous determination of phenolic compounds and triterpenic acids in oregano growing wild in Greece by 31P NMR spectroscopy.  

PubMed

(31)P nuclear magnetic resonance (NMR) spectroscopy was used to detect and quantify simultaneously a large number of phenolic compounds and the two triterpenic acids, ursolic acid and oleanolic acid, extracted from two oregano species Origanum onites and Origanum vulgare ssp. Hirtum using two different organic solvents ethanol and ethyl acetate. This analytical method is based on the derivatization of the hydroxyl and carboxyl groups of these compounds with the phosphorous reagent 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxa phospholane and the identification of the phosphitylated compounds on the basis of the (31)P chemical shifts. Unambiguous assignment of the (31)P NMR chemical shifts of the dihydroxy- and polyhydroxy-phenols in oregano species as well as those of the triterpenic acids was achieved upon comparison with the chemical shifts of model compounds assigned by using two-dimensional NMR techniques. Furthermore, the integration of the appropriate signals of the hydroxyl derivatives in the corresponding (31)P NMR spectra and the use of the phosphitylated cyclohexanol as an internal standard allowed the quantification of these compounds. The validity of this technique for quantitative measurements was thoroughly examined. PMID:23001915

Agiomyrgianaki, Alexia; Dais, Photis

2012-11-01

364

Practical aspects of Lee-Goldburg based CRAMPS techniques for high-resolution 1H NMR spectroscopy in solids: implementation and applications.  

PubMed

Elucidating the local environment of the hydrogen atoms is an important problem in materials science. Because (1)H spectra in solid-state nuclear magnetic resonance (NMR) suffer from low resolution due to homogeneous broadening, even under magic-angle spinning (MAS), information of chemical interest may only be obtained using certain high-resolution (1)H MAS techniques. (1)H Lee-Goldburg (LG) CRAMPS (Combined Rotation And Multiple-Pulse Spectroscopy) methods are particularly well suited for studying inorganic-organic hybrid materials, rich in (1)H nuclei. However, setting up CRAMPS experiments is time-consuming and not entirely trivial, facts that have discouraged their widespread use by materials scientists. To change this status quo, here we describe and discuss some important aspects of the experimental implementation of CRAMPS techniques based on LG decoupling schemes, such as FSLG (Frequency Switched), and windowed and windowless PMLG (Phase Modulated). In particular, we discuss the influence on the quality of the (1)H NMR spectra of the different parameters at play, for example LG (Lee-Goldburg) pulses, radio-frequency (rf) phase, frequency switching, and pulse imperfections, using glycine and adamantane as model compounds. The efficiency and robustness of the different LG-decoupling schemes is then illustrated on the following materials: organo-phosphorus ligand, N-(phosphonomethyl)iminodiacetic acid [H(4)pmida] [I], and inorganic-organic hybrid materials (C(4)H(12)N(2))[Ge(2)(pmida)(2)OH(2)] x 4H(2)O [II] and (C(2)H(5)NH(3))[Ti(H(1.5)PO(4))(PO(4))](2) x H(2)O [III]. PMID:18703365

Coelho, Cristina; Rocha, Joăo; Madhu, P K; Mafra, Luís

2008-10-01

365

Metabolic discrimination of rhizoma coptidis from different species using 1H NMR spectroscopy and principal component analysis.  

PubMed

Rhizoma coptidis, a broadly used medicinal plant, originates from the dried rhizomes of three species in Chinese pharmacopoeia, namely, Coptis chinensis Franch, Coptis deltoidea C. Y. Cheng et Hsiao, and Coptis teeta Wall. In this study, a novel approach using (1)H NMR spectroscopy combined with multivariate analysis was introduced to differentiate the three species and identify potential metabolic markers for better controlling the quality of rhizoma coptidis. A broad range of metabolites including alkaloids, sugars, organic acids, amino acids, and fatty acids present in rhizoma coptidis were detected by means of (1)H NMR spectroscopy. Principal component analysis (PCA) of the (1)H NMR data set showed a clear separation between all samples by PC1 and PC3, and some metabolites that could be responsible for the discrimination of the three species were identified. An analysis of variance (ANOVA) was performed to statistically verify the significance of differences in metabolite levels between species. By combining PCA and ANOVA, significantly higher contents of palmatine, coptisine, epiberberine, columbamine, and fatty acids together with lower contents of jateorrhizine were found in Coptis chinensis, whereas Coptis deltoidea and Coptis teetA showed the highest levels of sucrose and chlorogenic acid, respectively. This study indicates that metabolites of rhizoma coptidis vary with the species and the proposed method is suitable for metabolic fingerprinting analysis to check the genuine origin of rhizoma coptidis. PMID:22314415

Fan, Gang; Tao, Ling-hui; Yue, Qing-hong; Kuang, Ting-ting; Tang, Ce; Yang, Yong-dong; Luo, Wei-zao; Zhou, Xiang-dong; Zhang, Yi

2012-04-01

366

In vivo1H NMR spectroscopy of the human brain at 9.4 T: Initial results  

NASA Astrophysics Data System (ADS)

In vivo proton NMR spectroscopy allows non-invasive detection and quantification of a wide range of biochemical compounds in the brain. Higher field strength is generally considered advantageous for spectroscopy due to increased signal-to-noise and increased spectral dispersion. So far 1H NMR spectra have been reported in the human brain up to 7 T. In this study we show that excellent quality short echo time STEAM and LASER 1H NMR spectra can be measured in the human brain at 9.4 T. The information content of the human brain spectra appears very similar to that measured in the past decade in rodent brains at the same field strength, in spite of broader linewidth in human brain. Compared to lower fields, the T1 relaxation times of metabolites were slightly longer while T2 relaxation values of metabolites were shorter (<100 ms) at 9.4 T. The linewidth of the total creatine (tCr) resonance at 3.03 ppm increased linearly with magnetic field (1.35 Hz/T from 1.5 T to 9.4 T), with a minimum achievable tCr linewidth of around 12.5 Hz at 9.4 T. At very high field, B0 microsusceptibility effects are the main contributor to the minimum achievable linewidth.

Deelchand, Dinesh Kumar; Moortele, Pierre-François Van de; Adriany, Gregor; Iltis, Isabelle; Andersen, Peter; Strupp, John P.; Thomas Vaughan, J.; U?urbil, Kâmil; Henry, Pierre-Gilles

2010-09-01

367

Dynamics of guest molecules in PHTP inclusion compounds as probed by solid-state NMR and fluorescence spectroscopy.  

PubMed

Partially deuterated 1,4-distyrylbenzene () is included into the pseudohexagonal nanochannels of perhydrotriphenylene (PHTP). The overall and intramolecular mobility of is investigated over a wide temperature range by (13)C, (2)H NMR as well as fluorescence spectroscopy. Simulations of the (2)H NMR spectral shapes reveal an overall wobble motion of in the channels with an amplitude of about 4 degrees at T = 220 K and 10 degrees at T = 410 K. Above T = 320 K the wobble motion is superimposed by localized 180 degrees flips of the terminal phenyl rings with a frequency of 10(6) Hz at T = 340 K. The activation energies of both types of motions are around 40 kJ mol(-1) which imply a strong sterical hindrance by the surrounding PHTP channels. The experimental vibrational structure of the fluorescence excitation spectra of is analyzed in terms of small amplitude ring torsional motions, which provide information about the spatial constraints on by the surrounding PHTP host matrix. Combining the results from NMR and fluorescence spectroscopy as well as of time-dependent density functional calculations yields the complete potential surfaces of the phenyl ring torsions. These results, which suggest that intramolecular mobility of is only reduced but not completely suppressed by the matrix, are corroborated by MD simulations. Unrealistically high potential barriers for phenyl ring flips are obtained from MD simulations using rigid PHTP matrices which demonstrate the importance of large amplitude motions of the PHTP host lattice for the mobility of the guest molecules. PMID:19562129

Srinivasan, G; Villanueva-Garibay, J A; Müller, K; Oelkrug, D; Milian Medina, B; Beljonne, D; Cornil, J; Wykes, M; Viani, L; Gierschner, J; Martinez-Alvarez, R; Jazdzyk, M; Hanack, M; Egelhaaf, H-J

2009-07-01

368

Solid-state 13C NMR spectroscopy studies of xylans in the cell wall of Palmaria palmata (L. Kuntze, Rhodophyta).  

PubMed

The chemical structure and interactions of the cell wall polysaccharides from the red edible seaweed Palmaria palmata were studied by liquid-like magic-angle-spinning (MAS) and cross-polarization MAS (CPMAS) solid-state 13C NMR spectroscopy. The liquid-like MAS and CPMAS 13C NMR spectra of the rehydrated algal powder revealed the presence of beta-(1-->4)/beta-(1-->3)-linked D-xylan with chemical shifts close to those observed in the solution 13C NMR spectrum of the polysaccharide. Observation of mix-linked xylan in the liquid-like MAS 13C NMR spectrum indicated that part of this cell wall polysaccharide is loosely held in the alga. The CPMAS NMR spectrum of the dry algal powder alcohol insoluble residue (AIR) showed broad peaks most of which corresponded to the mix-linked xylan. Hydration of AIR induced a marked increase in the signal resolution also in the CPMAS NMR spectra together with a shift of the C-3 and C-4 signals of the (1-->3)- and (1-->4)-linked xylose, respectively. Such modifications were present in the spectrum of hydrated (1-->3)-linked xylan from the green seaweed Caulerpa taxifolia and absent in that of (1-->4)-linked xylan from P. palmata. This result emphasizes the important role of (1-->3) linkages on the mix-linked xylan hydration-induced conformational rearrangement. The mix-linked xylan signals were observed in the CPMAS NMR spectrum of hydrated residues obtained after extensive extractions by NaOH or strong chaotropic solutions indicating strong hydrogen bonds or covalent linkages. T(1 rho) relaxations were measured close or above 10 ms for the mix-linked xylan in the dry and hydrated state in AIR and indicated that the overall xylan chains likely remain rigid. Rehydration of the mix-linked xylan lead to a decrease in the motion of protons bounded to the C-1 and C-4 carbons of the (1-->4)-linked xylose supporting the re-organization of the xylan chains under hydration involving junction-zones held by hydrogen bonds between adjacent (1-->4)-linked xylose blocks. The CPMAS NMR spectrum of both dry and rehydrated residues obtained after NaOH and HCl extractions demonstrated the presence of cellulose and (1-->4)-linked xylans. The structures of the different polysaccharides are discussed in relation to their interactions and putative functions on the cell wall mechanical properties in P. palmata. PMID:12860427

Lahaye, Marc; Rondeau-Mouro, Corinne; Deniaud, Estelle; Buléon, Alain

2003-07-22

369

Assessing the fate and transformation of plant residues in the terrestrial environment using HR-MAS NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Plant litter decomposition plays a fundamental role in carbon and nitrogen cycles, provides key nutrients to the soil environment and represents a potentially large positive feedback to atmospheric CO 2. However, the full details of decomposition pathways and products are unknown. Here we present the first application of HR-MAS NMR spectroscopy on 13C and 15N labeled plant materials, and apply this approach in a preliminary study to monitor the environmental degradation of the pine and wheatgrass residues over time. In HR-MAS, is it possible to acquire very high resolution NMR data of plant biomass, and apply the vast array of multidimensional experiments available in conventional solution-state NMR. High levels of isotopic enrichment combined with HR-MAS significantly enhance the detection limits, and provide a wealth of information that is unattainable by any other method. Diffusion edited HR-MAS NMR data reveal the rapid loss of carbohydrate structures, while two-dimensional (2-D) HR-MAS NMR spectra demonstrate the relatively fast loss of both hydrolysable and condensed tannin structures from all plant tissues studied. Aromatic (partially lignin) and aliphatic components (waxes, cuticles) tend to persist, along with a small fraction of carbohydrate, and become highly functionalized over time. While one-dimensional (1-D) 13C HR-MAS NMR spectra of fresh plant tissue reflect compositional differences between pine and grass, these differences become negligible after decomposition suggesting that recalcitrant carbon may be similar despite the plant source. Two-dimensional 1H- 15N HR-MAS NMR analysis of the pine residue suggests that nitrogen from specific peptides is either selectively preserved or used for the synthesis of what appears to be novel structures. The amount of relevant data generated from plant components in situ using HR-MAS NMR is highly encouraging, and demonstrates that complete assignment will yield unprecedented structural knowledge of plant cell components, and provide a powerful tool with which to assess carbon sequestration and transformation in the environment.

Kelleher, Brian P.; Simpson, Myrna J.; Simpson, Andre J.

2006-08-01

370

Analysing the effects of frozen storage and processing on the metabolite profile of raw mullet roes using šH NMR spectroscopy.  

PubMed

(1)H NMR spectroscopy was used to investigate changes in the low molecular weight metabolic profile of raw mullet (Mugil spp.) roes during frozen storage and upon processing. NMR data were analysed by Principal Component Analyses (PCA). In the model constructed using frozen roes, no statistical significant metabolic modifications were observed in the first six months of storage, while choline derivatives, dimethylamine, lactate, and most of the free amino acids were identified as changing with statistical significance (p<0.05) in response to frozen storage time of twelve months. The PCA model comparing the metabolic profiles of roes before and after processing showed that the major modifications occurring upon manufacturing were the increase of the choline derivative compounds, uracil, and free amino acids, and a large decrease of taurine, glucose, lactate, and creatine/phosphocreatine. All of the above mentioned modifications reflect the occurrence of chemical/biochemical reactions arising from degradation processes such as lipolysis and proteolysis. PMID:24767028

Piras, Cristina; Scano, Paola; Locci, Emanuela; Sanna, Roberta; Marincola, Flaminia Cesare

2014-09-15

371

Si-29 NMR spectroscopy of naturally-shocked quartz from Meteor Crater, Arizona: Correlation to Kieffer's classification scheme  

NASA Technical Reports Server (NTRS)

We have applied solid state Si-29 nuclear magnetic resonance (NMR) spectroscopy to five naturally-shocked Coconino Sandstone samples from Meteor Crater, Arizona, with the goal of examining possible correlations between NMR spectral characteristics and shock level. This work follows our observation of a strong correlation between the width of a Si-29 resonance and peak shock pressure for experimentally shocked quartz powders. The peak width increase is due to the shock-induced formation of amorphous silica, which increases as a function of shock pressure over the range that we studied (7.5 to 22 GPa). The Coconino Sandstone spectra are in excellent agreement with the classification scheme of Kieffer in terms of presence and approximate abundances of quartz, coesite, stishovite, and glass. We also observe a new resonance in two moderately shocked samples that we have tentatively identified with silicon in tetrahedra with one hydroxyl group in a densified form of amorphous silica.

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

1993-01-01

372

Structure and ionic interactions of organic-inorganic composite polymer electrolytes studied by solid-state NMR and Raman spectroscopy.  

PubMed

Solid-state NMR studies of composite polymer electrolytes are reported. The materials consist of polyethylene oxide and an organic inorganic composite, together with a lithium salt, and are candidates for electrolytes in solid-state lithium ion batteries. Silicon and aluminum MAS and multiple quantum MAS are used to characterize the network character of the organic-inorganic composite, and spin diffusion measurements are used to determine the nanostructure of the polymer/composite blending. Multiple quantum spin counting is used to measure the ion aggregation. The NMR results are supported by Raman spectra, calorimetry, and impedance spectroscopy. From these experiments it is concluded that the composite suppresses polymer crystallization without suppressing its local mobility, and also suppresses the tendency for the ions to aggregate. This polymer composite thus appears very promising for application in lithium ion batteries. PMID:12469813

Joo, Chan Gyu; Bronstein, Lyudmila M; Karlinsey, Robert L; Zwanziger, Josef W

2002-01-01

373

Application of temperature-programmed oxidation, multinuclear MAS NMR and DRIFT spectroscopy to the surface characterization of modified silica nanoparticles  

NASA Astrophysics Data System (ADS)

Grafting of organosilane-functionalized substances onto the surface of nano-sized silica particles was studied by temperature-programmed oxidation (TPO), solid-state 13C and 29Si MAS NMR and DRIFT spectroscopy. By using 29Si MAS NMR quantitative data on the proportions of the various grafted structures, grafting yields and the reactivity of the geminal and free silanols towards the coupling agent were obtained. For 3-(trimethoxysilyl)propylmethacrylate as coupling agent and maleic acid as catalyst, the TPO weight loss of about 24 wt.% revealed a hypothetical coverage of about 5.5 graft/nm 2. Compared to the surface concentration of 2-3-OH groups per nm 2, this value can be only explained by grafting precondensed silane molecules onto nano-sized silica, assuming a core shell principle.

Bauer, F.; Freyer, A.; Ernst, H.; Gläsel, H.-J.; Mehnert, R.

2001-07-01

374

Investigating fatty acids inserted into magnetically aligned phospholipid bilayers using EPR and solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

This is the first time 2H solid-state NMR spectroscopy and spin-labeled EPR spectroscopy have been utilized to probe the structural orientation and dynamics of a stearic acid incorporated into magnetically aligned phospholipid bilayers or bicelles. The data gleaned from the two different techniques provide a more complete description of the bilayer membrane system. Both methods provided similar qualitative information on the phospholipid bilayer, high order, and low motion for the hydrocarbon segment close to the carboxyl groups of the stearic acid and less order and more rapid motion at the end towards the terminal methyl groups. However, the segmental order parameters differed markedly due to the different orientations that the nitroxide and C-D bond axes transform with the various stearic acid acyl chain conformations, and because of the difference in dynamic sensitivity between NMR and EPR over the timescales examined. 5-, 7-, 12-, and 16-doxylstearic acids spin-labels were used in the EPR experiments and stearic acid-d 35 was used in the solid-state NMR experiments. The influence of the addition of cholesterol and the variation of temperature on the fatty acid hydrocarbon chain ordering in the DMPC/DHPC phospholipid bilayers was also studied. Cholesterol increased the degree of ordering of the hydrocarbon chains. Conversely, as the temperature of the magnetically aligned phospholipid bilayers increased, the order parameters decreased due to the higher random motion of the acyl chain of the stearic acid. The results indicate that magnetically aligned phospholipid bilayers are an excellent model membrane system and can be used for both NMR and EPR studies.

Nusair, Nisreen A.; Tiburu, Elvis K.; Dave, Paresh C.; Lorigan, Gary A.

2004-06-01

375

Cationic complexation with dissolved organic matter: Insights from molecular dynamics computer simulations and NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Dissolved organic matter (DOM) is ubiquitous in soil and surface water and plays many important geochemical and environmental roles acting as a proton donor/acceptor and pH buffer and interacting with metal ions, minerals and organic species to form water-soluble and water-insoluble complexes of widely differing chemical and biological stabilities. There are strong correlations among the concentration of DOM and the speciation, solubility and toxicity of many trace metals in soil and water due to metal-DOM interaction. DOM can also significantly negatively affect the performance of nanofiltration and reverse osmosis membranes used industrially for water purification and desalination, being one of the major causes of a so-called `membrane bio- fouling'. The molecular scale mechanisms and dynamics of the DOM interactions with metals and membranes are, however, quite poorly understood. Methods of computational molecular modeling, combined with element- specific nuclear magnetic resonance (NMR) spectroscopy, can serve as highly effective tools to probe and quantify on a fundamental molecular level the DOM interactions with metal cations in aqueous solutions, and to develop predictive models of the molecular mechanisms responsible for the metal-DOM complexation in the environment. This paper presents the results of molecular dynamics (MD) computer simulations of the interaction of DOM with dissolved Na+, Cs+, Mg2+, and Ca2+. Na+ forms only very weak outer-sphere complexes with DOM. These results and the results of other recent molecular modeling efforts (e.g., Sutton et al., Environmental Toxicology and Chemistry, 24, 1902-1911, 2005), clearly indicate that both the structural and dynamic aspects of the cation-DOM complexation follow a simple trend in terms of the charge/size ratio for the ions. Due to the competition between ion hydration in bulk aqueous solution and adsorption of these cations by the negatively charged DOM functional groups (primarily carboxylate), larger ions of the same charge (Cs+ vs Na+, or Ca2+ vs Mg2+) have a stronger tendency for DOM association. However, for ions of approximately the same size, higher charge results in a stronger association with DOM. Thus, in contrast to Mg2+, Ca2+ forms strong inner-sphere complexes with DOM carboxylate groups, whereas the association of Na+ with DOM is even weaker than the outer-sphere metal- DOM complexing observed for Cs+. Taken together, these results support the idea of supramolecular, Ca- mediated DOM aggregation in aqueous environment. Cation-DOM binding occurs principally with carboxylate groups, and to a lesser extent with phenolic and other R-OH groups. The contributions of other DOM functional groups are minimal. The diffusional mobility of DOM-bound cations can decrease from ~20% (DOM- Na+ outer-sphere complex) to ~2000% (DOM-Ca2+ inner-sphere complex) compared with neat aqueous solutions (without DOM). The MD simulation results are in good agreement with NMR spectroscopic measurements for Cs-DOM solutions. The case of Cs+ complexation is particularly interesting, because Cs+ readily occurs as inner-sphere complexes on the surfaces of silica gel and many common soil minerals, including illite, kaolinite, and boehmite. The weaker interaction with DOM may be due to the occurence of relatively isolated carboxylic and phenolic groups on the DOM compared to densely packed structural oxygens and hydroxyl groups on the mineral surfaces.

Kalinichev, A. G.; Xu, X.; Kirkpatrick, R.

2006-12-01

376

Method for accurate measurements of nuclear-spin optical rotation for applications in correlated optical-NMR spectroscopy.  

PubMed

The nuclear-spin optical rotation (NSOR) effect recently attracted much attention due to potential applications in combined optical-NMR spectroscopy and imaging. Currently, the main problem with applications of NSOR is low SNR and accuracy of measurements. In this work we demonstrate a new method for data acquisition and analysis based on a low-power laser and an emphasis on software based processing. This method significantly reduces cost and is suitable for application in most NMR spectroscopy laboratories for exploration of the NSOR effect. Despite the use of low laser power, SNR can be substantially improved with fairly simple strategies including the use of short wavelength and a multi-pass optical cell with in-flow pre-polarization in a 7 T magnet. Under these conditions, we observed that NSOR signal can be detected in less than 1 min and discuss strategies for further improvement of signal. With higher SNR than previously reported, NSOR constants can be extracted with improved accuracy. On the example of water, we obtained measurements at a level of accuracy of 5%. We include a detailed theoretical analysis of the geometrical factors of the experiment, which is required for accurate quantification of NSOR. This discussion is particularly important for relatively short detection cells, which will be necessary to use in spectroscopy or imaging applications that impose geometrical constraints. PMID:23685716

Savukov, I M; Chen, H-Y; Karaulanov, T; Hilty, C

2013-07-01

377

NMR spectroscopy applied to the Cultural Heritage: a preliminary study on ancient wood characterisation  

NASA Astrophysics Data System (ADS)

High and low resolution solid state NMR methods have been applied to characterise a few samples of ancient wood. In an ancient larch wood sample, by applying 1H low resolution NMR methods as a function of the temperature, the average pore size and its distribution have been determined. In addition, high resolution NMR techniques have allowed addressing of the question of the proximity of water pools to cellulose and lignin. In particular, a model can be hypothesized in which water pools are surrounded by thin layers of amorphous cellulose and/or lignin while the crystalline domains of cellulose surround the layers of amorphous cellulose. Preliminary results obtained using a fully non invasive and portable NMR unilateral relaxometer, the Eureka-Mouse10 (EM10), are reported. This instrumentation is shown to be perfectly suitable for characterizing degradation in ancient wood samples.

Viel, S.; Capitani, D.; Proietti, N.; Ziarelli, F.; Segre, A. L.

378

Heteronuclear Dipolar Couplings, Total Spin Coherence, and Bilinear Rotations in NMR Spectroscopy.  

National Technical Information Service (NTIS)

In Chapter 1 a variety of different introductory topics are presented. The potential complexity of the nuclear magnetic resonsnace (NMR) spectra of molecules dissolved in liquid crystal solvents serves to motivate the development of multiple quantum (MQ) ...

J. R. Garbow

1983-01-01

379

Nuclear Magnetic Resonance Spectroscopy Applications: Proton NMR In Biological Objects Subjected To Magic Angle Spinning  

SciTech Connect

Proton NMR in Biological Objects Submitted to Magic Angle Spinning, In Encyclopedia of Analytical Science, Second Edition (Paul J. Worsfold, Alan Townshend and Colin F. Poole, eds.), Elsevier, Oxford 6:333-342. Published January 1, 2005. Proposal Number 10896.

Wind, Robert A.; Hu, Jian Zhi

2005-01-01

380

Probing the liquid behavior in La-based metallic glasses using NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The nature of liquid structure and its temperature and/or pressure dependent behavior is currently an active area of scientific investigation. Temperature dependent ^27Al nuclear magnetic resonance (NMR) experiments were carried out above the liquid temperature in La-based metallic glasses. The strong coexistence of two liquid states was observed in addition to nonlinear liquid behavior. NMR results also provide thermodynamic insight for the structural changes observed.

Sandor, Magdalena; Xu, Wei; Ke, Hai-Bo; Xi, Xue-Kui; Wu, Yue; Wang, Wei-Hua

2012-02-01

381

H NMR and Optical Spectroscopy Study of the Radiodosimetric Properties of the Pira Gel  

Microsoft Academic Search

The radiation-response of the Fricke-doped protein-polymer gel (PIRA) was studied by H NMR, as well as with spectrophotometric and fluorescence methods. In this gel, the ionizing radiation induces an increase in the NMR longitudinal relaxation rate, R1, of protons. It was observed that: I) the main mechanism responsible for the increase in R1 was the oxidation of ferrous to ferric

G. Zebrowska; Cz. Lewa; J. de Certaines

2001-01-01

382

Compounds of L(+)-ascorbic acid with dimethylthallium(III), dimethyltin(IV), and dibutyltin(IV): Synthesis, solid-state spectroscopy (CP\\/MAS 13C NMR and IR), and multi-NMR behavior in aqueous solution  

Microsoft Academic Search

Reaction of L(+)-ascorbic acid (H2Asc) with TlMe2OOCCH3, SnMe2O, and SnBu2Cl2 (in this last case, in the presence of Et3N) afforded [TlMe2(HAsc)]ˇ12C3H8O, [SnMe2(Asc)], and [SnBu2(Asc)], respectively. The new compounds were studied in the solid state by CP\\/MAS 13C NMR and IR spectroscopy, and in aqueous solution by 1H, 13C, 205Tl, and 119Sn NMR spectroscopy. The thallium compound behaves as a salt.

José S. Casas; María V. Castańo; María S. García-Tasende; Teresa Pérez-Alvarez; Agustín Sánchez; José Sordo

1996-01-01

383

27Al and 29Si NMR spectroscopy of MgSiO3 perovskite: mechanisms of Al and Fe incorporation  

NASA Astrophysics Data System (ADS)

The boundary between the Earth's upper and lower mantle is generally attributed to the decomposition of (Mg,Fe)2SiO4 ringwoodite into ferropericlase and perovskite-structured (Mg,Fe)SiO3, hereafter perovskite. Concomitant with this phase change is the more gradual disappearance of a separate Al-bearing phase (majoritic garnet) and dissolution of Al into perovskite. The mechanism of Al incorporation is strongly affected by the presence of Fe due to the co-substitution of Al3+ and Fe3+ for Si4+ and Mg2+, respectively. However, questions about specific substitution mechanisms, site occupancy, and long- and short-range ordering of Fe and Al are still not fully understood. These are questions that NMR is particularly suited to address. We are applying Mossbauer, and 27Al and 29Si MAS-NMR spectroscopy to a series of Al- and Fe-bearing MgSiO3 perovskites of nominal composition Mg1-xFexSi1-xAlxO3 (x = 0.01, 0.025, 0.05). These were synthesized in a multi-anvil cell press at 26 GPa and 1900°C from either glassy starting material or Fe-bearing, aluminous pyroxene synthesized at 8-10 GPa and 1200°C. 29Si spectra show the presence of only a narrow perovskite peak at -191.7 ppm and a broad peak at -81 ppm from an amorphous phase likely formed when crushing the multi-anvil run products. 27Al spectra contain one narrow peak at 6.4 ppm and one broad peak at -14.6 ppm, matching those seen in previous NMR studies of aluminous perovskite and corresponding to Al3+ substituting for Si4+ and Mg2+ respectively. The ratio of observable Al3+ in Si4+ vs. that in Mg2+ sites ranges from 5.5 to 6.3 when the signal to noise of the -14.6 ppm peak is sufficient for quantitation. NMR spectra of materials containing paramagnetic species (i.e. Fe2+ or Fe3+) are often complicated and difficult to interpret due to line broadening, signal loss, "contact" shifts, etc. However, with an understanding of paramagnetic interactions in NMR spectroscopy, valuable information can be gained about some Fe-bearing geological materials. For the pyroxene starting materials used here, NMR signal loss increases linearly with increasing Fe content, an expected result given the likely uncoupled substitution of Fe2+ and Al3+ in these materials. However, 27Al signal loss for the perovskite samples is non-linear with a nearly constant value going from Fe/(Fe + Mg) = 0.01 to 0.025 indicating strong ordering of Fe3+ and Al3+ onto adjacent crystallographic sites. Complete signal loss at Fe/(Fe + Mg) = 0.05 suggests the upper limit of Fe2+ and Fe3+ concentration at which useful NMR data can be obtained for this system. The results of this study are a start to a better understanding of the mechanism of solution of Fe and Al in perovskite and continued work on this problem could provide valuable information on this important lower mantle phase. In addition, this study has potential to give us more general insights into paramagnetic interactions in NMR spectroscopy of geological materials.

Palke, A.; Stebbins, J. F.; Frost, D. J.; McCammon, C. A.

2011-12-01

384

Chemical characteristics of dissolved organic matter during composting of different organic wastes assessed by (13)C CPMAS NMR spectroscopy.  

PubMed

This research aimed at assessing the chemical changes occurring in DOM extracted from different composting substrates by means of (13)C CPMAS NMR spectroscopy. During composting a reduction of carbohydrates and an increase of aromatic, phenolic, carboxylic and carbonylic C were observed. The highest increase in alkyl C and the lowest increase in aromatic C were explained by the presence of hardly degradable pine needles in the substrate, whereas the highest reduction in carbohydrates and the highest increase of the alkyl C/O-alkyl C ratio were attributed to the presence of highly degradable materials such as spent yeast from beer production. PMID:20594836

Caricasole, P; Provenzano, M R; Hatcher, P G; Senesi, N

2010-11-01

385

1H NMR and electronic absorption spectroscopy of paramagnetic water-soluble Meso-tetraarylsubstituted cationic and anionic metalloporphyrins  

Microsoft Academic Search

The ionization, ?-oxo-dimerization and axial ligation equilibria of free bases, iron(III) and manganese(III) derivatives of meso-tetrakis(p-sulfonatophenyl)porphyrin (TPPS4) and meso-tetrakis(4-N-methyl-pyridiniumyl)porphyrin (TMPyP) in aqueous solution are studied by 1H NMR and electronic absorption spectroscopy. At physiological pH, Fe(III) complexes of TMPYP and TPPS4 exist predominantly as dimers and may undergo transition to low spin species upon binding to biomolecules, whereas Mn(III) complexes

Victor E. Yushmanov; Hidetake Imasato; Tania T. Tominaga; Marcel Tabak

1996-01-01

386

Solid state 13C NMR and FT-IR spectroscopy of the cocoon silk of two common spiders  

NASA Astrophysics Data System (ADS)

The structure of the silk from cocoons of two common spiders, Araneus diadematus (family Araneidae) and Achaearanea tepidariorum (family Theridiidae) was investigated by means of 13C solid state NMR and FT-IR spectroscopies. The combined use of these two techniques allowed us to highlight differences in the two samples. The cocoon silk of Achaearanea tepidariorum is essentially constituted by helical and ?-sheet structures, whereas that of Araneus diadematus shows a more complex structure, containing also ?-strands and ?-turns. Moreover, the former silk is essentially crystalline while the latter contains more mobile domains. The structural differences of the two cocoon silks are ascribed to the different habitat of the two species.

Bramanti, Emilia; Catalano, Donata; Forte, Claudia; Giovanneschi, Mario; Masetti, Massimo; Veracini, Carlo Alberto

2005-11-01

387

Structural and dynamical studies of molecular and network forming chalcogenide glasses and supercooled liquids with NMR and Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The techniques of Nuclear Magnetic Resonance (NMR) and Raman spectroscopy have been employed to study structure and dynamics in Ge-Se, Ge/As-Te, and As-S binary and complex Ge-As-Te and P-As-S ternary chalcogenide glasses. Structural studies were conducted on Ge-Se glasses and on binary Ge/As-Te and ternary Ge-As-Te systems. The structure of the GexSe100-x glass series, with 5?x?33, is investigated with 77Se Magic Angle Spinning (MAS) NMR and then compared with three different proposed structural models. For the binary Ge-Te and As-Te and ternary Ge-As-Te glass systems the structure is studied using Raman spectroscopy and correlated with physical properties such as molar volume, viscosity, optical band gap and thermophysical properties. Studies on glass transition dynamics were conducted on systems with a range of structural features including an As4S3 inorganic molecular glass former, an As-P-S system where molecules are bonded to the As-S network, and network glasses in the Ge-Se system. Timescales of the rotational dynamics of As4S3 cage molecules in the molecular As-sulfide glass and supercooled liquid show remarkably large decoupling from the timescales of viscous flow and shear relaxation at temperatures below and near Tg (312K). Next, the dynamic behavior of a (As 2S3)90(P2S5)10 glass, which is proposed to consist of As2P2S8 molecular structures which are connected to an As-S network, is investigated with 31P NMR. The rotational dynamics of selenium chains in network forming GexSe100-x glasses and supercooled liquids with 5?x?23 are investigated with variable temperature 77Se NMR spectroscopy to determine the relationship between rigidity percolation and dynamic behavior. The timescale of the motion of the Se atoms is observed to be nearly identical for x?17 and ?2.36. However, for the x=20 and 23 compositions where ?2.4, above the rigidity percolation threshold, the timescale slows down abruptly. Finally, the Ge20Se 80 glass and supercooled liquid have been the focus of a variable temperature Raman spectroscopy study to investigate the vibrational mode softening behavior and the importance of vibrational entropy in glass transition.

Gjersing, Erica Lee

388

Probing transient conformational States of proteins by solid-state r1? relaxation-dispersion NMR spectroscopy.  

PubMed

The function of proteins depends on their ability to sample a variety of states differing in structure and free energy. Deciphering how the various thermally accessible conformations are connected, and understanding their structures and relative energies is crucial in rationalizing protein function. Many biomolecular reactions take place within microseconds to milliseconds, and this timescale is therefore of central functional importance. Here we show that R1? relaxation dispersion experiments in magic-angle-spinning solid-state NMR spectroscopy make it possible to investigate the thermodynamics and kinetics of such exchange process, and gain insight into structural features of short-lived states. PMID:24644028

Ma, Peixiang; Haller, Jens D; Zajakala, Jérémy; Macek, Pavel; Sivertsen, Astrid C; Willbold, Dieter; Boisbouvier, Jérôme; Schanda, Paul

2014-04-22

389

Application of static microcoils and WURST pulses for solid-state ultra-wideline NMR spectroscopy of quadrupolar nuclei  

NASA Astrophysics Data System (ADS)

The uses of microcoils and WURST pulses for acquiring ultra-wideline (UW) NMR spectra of half-integer quadrupolar nuclei are explored. Using large rf field strengths or frequency-swept pulses, UW spectra (breadth > 300 kHz) can be acquired without changing the transmitter frequency. The efficiency of UWNMR spectroscopy improves for both microcoil and WURST pulse experiments compared to rectangular-pulse experiments using a 4.0 mm coil. Microcoils are also used to acquire UW spectra of an unreceptive nucleus ( 91Zr) and a spectrum comprised of both central and satellite transitions ( 59Co).

Tang, Joel A.; O'Dell, Luke A.; Aguiar, Pedro M.; Lucier, Bryan E. G.; Sakellariou, Dimitris; Schurko, Robert W.

2008-12-01

390

Vibrational spectroscopy investigation using ab initio and DFT vibrational analysis of 7-chloro-2-methylamino-5-phenyl-3H-1,4-benzodiazepine-4-oxide.  

PubMed

The FT-IR and FT-Raman spectrum of 7-chloro-2-methylamino-5-phenyl-3H-1, 4-benzodiazepine-4-oxide (7CMP4BO) has been recorded in the region 4000-400 and 4000-100 cm(-1) respectively. The optimized geometry, Thermodynamic properties, NBO, Molecular Electrostatic Potentials, PES, frequency and intensity of the vibrational bands of 7CMP4BO were obtained by the ab initio HF and density functional theory (DFT), B3LYP/6-31G (d,p) basis set. The molecule orbital contributions were studied by using the total (TDOS), partial (PDOS), and overlap population (OPDOS) density of states. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated potential energy distribution (PED). The linear polarizability (?) and the first order hyperpolarizability (?) values of the investigated molecule have been computed using DFT quantum mechanical calculations. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically calculated values. PMID:23732619

Prasath, M; Muthu, S; Arun Balaji, R

2013-09-01

391

Vibrational spectroscopy investigation using ab initio and DFT vibrational analysis of 7-chloro-2-methylamino-5-phenyl-3H-1,4-benzodiazepine-4-oxide  

NASA Astrophysics Data System (ADS)

The FT-IR and FT-Raman spectrum of 7-chloro-2-methylamino-5-phenyl-3H-1, 4-benzodiazepine-4-oxide (7CMP4BO) has been recorded in the region 4000-400 and 4000-100 cm-1 respectively. The optimized geometry, Thermodynamic properties, NBO, Molecular Electrostatic Potentials, PES, frequency and intensity of the vibrational bands of 7CMP4BO were obtained by the ab initio HF and density functional theory (DFT), B3LYP/6-31G (d,p) basis set. The molecule orbital contributions were studied by using the total (TDOS), partial (PDOS), and overlap population (OPDOS) density of states. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated potential energy distribution (PED). The linear polarizability (?) and the first order hyperpolarizability (?) values of the investigated molecule have been computed using DFT quantum mechanical calculations. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically calculated values.

Prasath, M.; Muthu, S.; Arun Balaji, R.

2013-09-01

392

Complete assignment of the 500 MHz 1H-NMR spectra of bleomycin A2 in H2O and D sub 2 O solution by means of two-dimensional NMR spectroscopy  

SciTech Connect

1H-NMR spectra of bleomycin A2 recorded at 500 MHz in D{sub 2}O and H{sub 2}O at 24{degrees}C and 3{degrees}C were investigated. Resonances of the individual spin systems were identified by using two-dimensional correlation spectroscopy (COSY), two-dimensional spin echo correlated spectroscopy (SECSY) and by the application of two-dimensional Nuclear Overhauser Effect spectroscopy (NOESY). Employment of these techniques allowed the assignment of 113 exchangeable and 59 non-exchangeable protons in the 1H NMR spectrum of bleomycin A2. By means of 2D NOE spectroscopy also interresidual connectivities could be observed. Comparison of the NOESY spectra at 3{degrees}C and 24{degrees}C suggest that at low temperatures the central party of the bleomycin A2 molecule tends to adopt an extended conformation.

Haasnoot, C.A.; Pandit, U.K.; Kruk, C.; Hilbers, C.W. (Univ. of Nijmegen (Netherlands))

1984-10-01

393

Structure of a protein determined by solid-state magic-angle-spinning NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The determination of a representative set of protein structures is a chief aim in structural genomics. Solid-state NMR may have a crucial role in structural investigations of those proteins that do not easily form crystals or are not accessible to solution NMR, such as amyloid systems or membrane proteins. Here we present a protein structure determined by solid-state magic-angle-spinning (MAS) NMR. Almost complete 13C and 15N resonance assignments for a micro-crystalline preparation of the ?-spectrin Src-homology 3 (SH3) domain formed the basis for the extraction of a set of distance restraints. These restraints were derived from proton-driven spin diffusion (PDSD) spectra of biosynthetically site-directed, labelled samples obtained from bacteria grown using [1,3-13C]glycerol or [2-13C]glycerol as carbon sources. This allowed the observation of long-range distance correlations up to ~7Ĺ. The calculated global fold of the ?-spectrin SH3 domain is based on 286 inter-residue 13C-13C and six 15N-15N restraints, all self-consistently obtained by solid-state MAS NMR. This MAS NMR procedure should be widely applicable to small membrane proteins that can be expressed in bacteria.

Castellani, Federica; van Rossum, Barth; Diehl, Annette; Schubert, Mario; Rehbein, Kristina; Oschkinat, Hartmut

2002-11-01

394

Phytotoxicity, not nitrogen immobilization, explains plant litter inhibitory effects: evidence from solid-state 13C NMR spectroscopy.  

PubMed

Litter decomposition provides nutrients that sustain ecosystem productivity, but litter may also hamper root proliferation. The objectives of this work were to assess the inhibitory effect of litter decomposition on seedling growth and root proliferation; to study the role of nutrient immobilization and phytotoxicity; and to characterize decomposing litter by (13)C NMR spectroscopy. A litter-bag experiment was carried out for 180 d with 16 litter types. Litter inhibitory effects were assessed by two bioassays: seed germination and root proliferation bioassays. Activated carbon (C) and nutrient solutions were used to evaluate the effects of phytotoxic factors and nutrient immobilization. An inhibitory effect was found for all species in the early phase of decomposition, followed by a decrease over time. The addition of activated C to litter removed this inhibition. No evidence of nutrient immobilization was found in the analysis of nitrogen dynamics. NMR revealed consistent chemical changes during decomposition, with a decrease in O-alkyl and an increase in alkyl and methoxyl C. Significant correlations were found among inhibitory effects, the litter decay rate and indices derived from NMR. The results show that it is possible to predict litter inhibitory effects across a range of litter types on the basis of their chemical composition. PMID:21574999

Bonanomi, Giuliano; Incerti, Guido; Barile, Elisa; Capodilupo, Manuela; Antignani, Vincenzo; Mingo, Antonio; Lanzotti, Virginia; Scala, Felice; Mazzoleni, Stefano

2011-09-01

395

In situ temperature jump high-frequency dynamic nuclear polarization experiments: enhanced sensitivity in liquid-state NMR spectroscopy.  

PubMed

We describe an experiment, in situ temperature jump dynamic nuclear polarization (TJ-DNP), that is demonstrated to enhance sensitivity in liquid-state NMR experiments of low-gamma spins--13C, 15N, etc. The approach consists of polarizing a sample at low temperature using high-frequency (140 GHz) microwaves and a biradical polarizing agent and then melting it rapidly with a pulse of 10.6 microm infrared radiation, followed by observation of the NMR signal in the presence of decoupling. In the absence of polarization losses due to relaxation, the enhancement should be epsilon+ = epsilon(T(obs)/T(mu)(wave)), where epsilon+ is the observed enhancement, epsilon is the enhancement obtained at the temperature where the polarization process occurs, and T(mu)(wave) and T(obs) are the polarization and observation temperatures, respectively. In a single experimental cycle, we observe room-temperature enhancements, epsilon(dagger), of 13C signals in the range 120-400 when using a 140 GHz gyrotron microwave source, T(mu)(wave) = 90 K, and T(obs) = 300 K. In addition, we demonstrate that the experiment can be recycled to perform signal averaging that is customary in contemporary NMR spectroscopy. Presently, the experiment is applicable to samples that can be repeatedly frozen and thawed. TJ-DNP could also serve as the initial polarization step in experiments designed for rapid acquisition of multidimensional spectra. PMID:16848479

Joo, Chan-Gyu; Hu, Kan-Nian; Bryant, Jeffrey A; Griffin, Robert G

2006-07-26

396

Natural Abundance 43Ca NMR Spectroscopy of Tobermorite and Jennite: Model Compounds for C–S–H  

SciTech Connect

There are few effective methods for characterizing the molecular scale structural environments of Ca21 in hydrated cements, which has limited our ability to understand the structure of, for example, Ca–silicate hydrate (C–S–H). 43Ca nuclear magnetic resonance (NMR) spectroscopy has long been considered too insensitive to provide useful data in this regard, but 43Ca magic angle spinning (MAS) NMR spectra reported here for synthetic tobermorite and jennite with naturally abundant levels of 43Ca demonstrate that this is a viable approach.We show that spectra with useful signal/noise ratios can be obtained in a reasonable acquisition period (B2 days) using an H0 field strength of 21.1 T, 5 mm rotors spinning at a frequency of 5 kHz, and a double frequency sweep preparatory pulse sequence. Tobermorite and jennite produce relatively broad resonances due to their complex structures and structural disorder, however, the chemical shift differences between six-coordinate 43Ca in jennite and seven-coordinate 43Ca in 11A ° tobermorite are large enough that the signals are entirely resolved at this field. These data suggest that signal from ideal tobermorite-like and jennite-like sites in cement C–S–H can most likely be distinguished by 43Ca NMR and that this method will be a powerful approach for studying cement-based ceramic materials in the coming decade.

Bowers, Geoffrey M.; Kirkpatrick, Robert J.

2009-02-13

397

Natural Abundance 43Ca NMR Spectroscopy of Tobermorite and Jennite: Model Compounds for C–S–H  

SciTech Connect

There are few effective methods for characterizing the molecular scale structural environments of Ca2? in hydrated cements, which has limited our ability to understand the structure of, for example, Ca–silicate hydrate (C–S–H). 43Ca nuclear magnetic resonance (NMR) spectroscopy has long been considered too insensitive to provide useful data in this regard, but 43Ca magic angle spinning (MAS) NMR spectra reported here for synthetic tobermorite and jennite with naturally abundant levels of 43Ca demonstrate that this is a viable approach.We show that spectra with useful signal/noise ratios can be obtained in a reasonable acquisition period (~2 days) using an H? field strength of 21.1 T, 5 mm rotors spinning at a frequency of 5 kHz, and a double frequency sweep preparatory pulse sequence. Tobermorite and jennite produce relatively broad resonances due to their complex structures and structural disorder, however, the chemical shift differences between six-coordinate 43Ca in jennite and seven-coordinate 43Ca in 11? tobermorite are large enough that the signals are entirely resolved at this field. These data suggest that signal from ideal tobermorite-like and jennite-like sites in cement C–S–H can most likely be distinguished by 43Ca NMR and that this method will be a powerful approach for studying cement-based ceramic materials in the coming decade.

Bowers, Geoffrey M.; Kirkpatrick, Robert J.

2009-02-13

398

Investigation of Atropisomerism in ortho-Substituted Tetraphenylporphyrins: An Experimental Module Involving Synthesis, Chromatography, and NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

An experimental module suitable for advanced undergraduates is described. This module begins with the synthesis of tetra(o-tolyl)porphyrin (T(o-Tol)P), which exists as a statistical distribution of atropisomers due to hindered rotation about the porphine-phenyl bonds. The six types of nonequivalent methyl protons in the four atropisomers (4,0; 3,1; cis 2,2; and trans 2,2) give rise to six methyl peaks in the proton NMR spectrum of T(o-Tol)P. Due to slight differences in the migration rates of the four atropisomers, samples of T(o-Tol)P which are enriched and depleted in certain atropisomers can be obtained chromatographically. NMR spectra of these samples are recorded, and an examination of the changes in relative intensities of the six methyl peaks leads to positive peak assignments. The farthest upfield methyl peak is attributed to the 4,0 isomer (in which all four methyl groups are cofacial), which has the fastest migration rate on silica gel. It is shown that as the number of cofacial methyl neighbors for a particular methyl group decreases, the chemical shift of the methyl protons increases. This experiment leads to a greater understanding of chromatography and NMR spectroscopy in addition to introducing students to porphyrin synthesis and the concepts of atropisomerism and statistical distributions.

Freitag Beeston, Ruth; Stitzel, Shannon E.; Rhea, Mitchell A.

1997-12-01

399

Structure and alignment of the membrane-associated antimicrobial peptide arenicin by oriented solid-state NMR spectroscopy.  

PubMed

The antimicrobial arenicin peptides are cationic amphipathic sequences that strongly interact with membranes. Through a cystine ring closure a cyclic ?-sheet structure is formed in aqueous solution, which persists when interacting with model membranes. In order to investigate the conformation, interactions, dynamics, and topology of their bilayer-associated states, arenicin 1 and 2 were prepared by chemical solid-phase peptide synthesis or by bacterial overexpression, labeled selectively or uniformly with (15)N, reconstituted into oriented membranes, and investigated by proton-decoupled (31)P and (15)N solid-state NMR spectroscopy. Whereas the (31)P NMR spectra indicate that the peptide induces orientational disorder at the level of the phospholipid head groups, the (15)N chemical shift spectra agree well with a regular ?-sheet conformation such as the one observed in micellar environments. In contrast, the data do not fit the twisted ?-sheet structure found in aqueous buffer. Furthermore, the chemical shift distribution is indicative of considerable conformational and/or topological heterogeneity when at the same time the (15)N NMR spectra exclude alignments of the peptide where the ?-sheet lies side ways on the membrane surface. The ensemble of experimental constraints, the amphipathic character of the peptide, and in particular the distribution of the six arginine residues are in agreement with a boatlike dimer structure, similar or related to the one observed in micellar solution, that floats on the membrane surface with the possibility to oligomerize into higher order structures and/or to insert in a transmembrane fashion. PMID:21456583

Salnikov, Evgeniy S; Aisenbrey, Christopher; Balandin, Sergey V; Zhmak, Maxim N; Ovchinnikova, Tatiana V; Bechinger, Burkhard

2011-05-10

400

Synthesis, Characterization, and 1H and 71Ga MAS NMR Spectroscopy of a Novel Mg/Ga Double Layered Hydroxide  

NASA Astrophysics Data System (ADS)

A new brucite-like layered Mg/Ga double hydroxide (LDH) of composition [Mg 0.174Ga 0.256(OH) 2](CO 3) 0.134ˇ mH 2O was synthesized by coprecipitation at pH 10. The hydroxide and the mixed oxides resulting from its thermal decomposition at 523, 823 and 1073 K were characterized by X-ray diffraction, diffuse reflectance infrared spectroscopy, high-resolution solid-state nuclear magnetic resonance (MAS NMR), and thermogravimetric analysis. The surface properties of the solid (specific surface) and its basicity were also determined. The Mg/Ga LDH was found to be stable up to 523K and to decompose into a mixture of periclase MgO and amorphous Ga 2O 3at 823 K. Its changes with temperature were monitored by using 1H and 71Ga MAS NMR; 1H MAS NMR spectra revealed the loss of interlayer OH groups supporting the brucite-like structure on calcination at 823K.

Aramendía, María. Angeles; Borau, Victor; Jiménez, César; Marinas, José Maria; Romero, Francisco José; Ruiz, José Rafael

1997-06-01

401

The hydrogen-bonded 2-pyridone dimer model system. 1. Combined NMR and FT-IR spectroscopy study.  

PubMed

2-Pyridone (PD), converting to 2-hydroxypyridine (HP) through a lactam-lactim isomerization mechanism, can form three different cyclic dimers by hydrogen bond formation: (PD)(2), (PD-HP), and (HP)(2). We investigate the complexation chemistry of pyridone in dichloromethane-d(2) using a combined NMR and Fourier transform infrared (FT-IR) approach. Temperature-dependent (1)H NMR spectra indicate that at low temperatures (<200 K) pyridone in solution predominantly exists as a cyclic (PD)(2) dimer, in exchange with PD monomers. At higher temperatures a proton exchange mechanism sets in, leading to a collapse of the doublet of (15)N labeled 2-pyridone. Linear FT-IR spectra indicate the existenc