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1

NMR-correlated high-field electron paramagnetic resonance spectroscopy  

NASA Astrophysics Data System (ADS)

A high-field electron paramagnetic resonance method is introduced for determining the relative orientation of the g and hyperfine tensors in disordered systems by correlation of NMR frequencies to the electron spin resonance fields. Simple and characteristic correlation patterns are obtained that are only moderately influenced by the violation of the high-field approximation for the nuclear spin. A pulse sequence based on electron-electron double resonance and spectral hole burning is applied to overcome the limitations of excitation bandwidth and deadtime. Experiments on the nitroxide spin probe TEMPOL in a polymer matrix reveal a small but significant non-coincidence of the two principal axes systems.

Jeschke, Gunnar; Spiess, Hans Wolfgang

1998-08-01

2

Quantitative {sup 29}Si MAS NMR spectroscopy of cement and silica fume containing paramagnetic impurities  

SciTech Connect

The low natural abundance and the long spin lattice relaxation time of {sup 29}Si lead to long measurement times and/or low signal-to-noise ratios using {sup 29}Si magic angle spinning NMR spectroscopy. By contrast, samples containing paramagnetic iron ions have much shorter relaxation times, making measurements up to seven times more efficient, but at the same time making quantitative analysis unreliable. To solve the problem, the spin-lattice relaxation times of ordinary Portland cement (opc) and silica fume with and without iron content has been determined with inversion recovery experiments. The effect of varying the spectrum repetition time on the quantitative analysis is demonstrated for mixtures of opc with silica fume. For opc and silica fume with iron impurities repetition times as short as 5 s has permitted accurate quantitative analysis of the silicates present in these materials.

Hilbig, H. [Center of Building Materials (CBM), Technische Universitaet Muenchen, Baumbachstr. 7, D-81245 Munich (Germany)]. E-mail: hilbig@cbm.bv.tum.de; Koehler, F.H. [Department Chemie, Technische Universitaet Muenchen, D-85747 Garching (Germany); Schiessl, P. [Center of Building Materials (CBM), Technische Universitaet Muenchen, Baumbachstr. 7, D-81245 Munich (Germany)

2006-02-15

3

The IR-¹?N-HSQC-AP experiment: a new tool for NMR spectroscopy of paramagnetic molecules.  

PubMed

A crucial factor for the understanding of structure-function relationships in metalloproteins is the identification of NMR signals from residues surrounding the metal cofactor. When the latter is paramagnetic, the NMR information in the proximity of the metal center may be scarce, because fast nuclear relaxation quenches signal intensity and coherence transfer efficiency. To identify residues at a short distance from a paramagnetic center, we developed a modified version of the ¹?N-HSQC experiment where (1) an inversion recovery filter is added prior to HSQC, (2) the INEPT period has been optimized according to fast relaxation of interested spins, (3) the inverse INEPT has been eliminated and signals acquired as antiphase doublets. The experiment has been successfully tested on a human [Fe?S?] protein which is involved in the biogenesis of iron-sulfur proteins. Thirteen HN resonances, unobserved with conventional HSQC experiments, could be identified. The structural arrangement of the protein scaffold in the proximity of the Fe/S cluster is fundamental to comprehend the molecular processes responsible for the transfer of Fe/S groups in the iron-sulfur protein assembly machineries. PMID:24414179

Ciofi-Baffoni, Simone; Gallo, Angelo; Muzzioli, Riccardo; Piccioli, Mario

2014-02-01

4

ELECTRON PARAMAGNETIC RESONANCE SPECTROSCOPY  

E-print Network

CHAPTER 3 ELECTRON PARAMAGNETIC RESONANCE SPECTROSCOPY 1 Sergei A. Dikanov and 2 Antony R. Crofts 1 for the investigation of unpaired electron spins. Two terms are used in the literature: electron paramagnetic resonance (EPR) and electron spin resonance (ESR). We will use the first term in this chapter. During the sixty

Crofts, Antony R.

5

Solid-state NMR crystallography through paramagnetic restraints.  

PubMed

Pseudocontact shifts (PCSs) measured by solid-state NMR spectroscopy (SS-NMR) on microcrystalline powders of a paramagnetic metalloprotein permit NMR crystallography. Along with other restraints for SS-NMR experiments, the protein molecular structure as well as the correct crystal packing are obtained. PMID:22393876

Luchinat, Claudio; Parigi, Giacomo; Ravera, Enrico; Rinaldelli, Mauro

2012-03-21

6

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

7

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

PubMed Central

Biomacromolecules that are challenging for the usual structural techniques can be studied with atomic resolution by solid-state nuclear magnetic resonance. However, the paucity of >5 Å distance restraints, 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 analogs 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 ~10-20 Å distances 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 Å. PMID:22522262

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

2012-01-01

8

High-resolution paramagnetically enhanced solid-state NMR spectroscopy of membrane proteins at fast magic angle spinning.  

PubMed

Magic angle spinning nuclear magnetic resonance (MAS NMR) is well suited for the study of membrane proteins in membrane mimetic and native membrane environments. These experiments often suffer from low sensitivity, due in part to the long recycle delays required for magnetization and probe recovery, as well as detection of low gamma nuclei. In ultrafast MAS experiments sensitivity can be enhanced through the use of low power sequences combined with paramagnetically enhanced relaxation times to reduce recycle delays, as well as proton detected experiments. In this work we investigate the sensitivity of (13)C and (1)H detected experiments applied to 27 kDa membrane proteins reconstituted in lipids and packed in small 1.3 mm MAS NMR rotors. We demonstrate that spin diffusion is sufficient to uniformly distribute paramagnetic relaxation enhancement provided by either covalently bound or dissolved CuEDTA over 7TM alpha helical membrane proteins. Using paramagnetic enhancement and low power decoupling in carbon detected experiments we can recycle experiments ~13 times faster than under traditional conditions. However, due to the small sample volume the overall sensitivity per unit time is still lower than that seen in the 3.2 mm probe. Proton detected experiments, however, showed increased efficiency and it was found that the 1.3 mm probe could achieve sensitivity comparable to that of the 3.2 mm in a given amount of time. This is an attractive prospect for samples of limited quantity, as this allows for a reduction in the amount of protein that needs to be produced without the necessity for increased experimental time. PMID:24338448

Ward, Meaghan E; Wang, Shenlin; Krishnamurthy, Sridevi; Hutchins, Howard; Fey, Michael; Brown, Leonid S; Ladizhansky, Vladimir

2014-01-01

9

2D NMR of paramagnetic metalloenzymes: Cyanide-inhibited horseradish peroxidase  

Microsoft Academic Search

Summary Two-dimensional (2D) proton NMR correlation spectroscopy, COSY, and nuclear Overhauser spectroscopy, NOESY, have been used to explore the applicability of these methods for the moderately large (42 KDa), paramagnetic cyanide-inhibited derivative of horseradish peroxidase, HRP-CN. The target resonances are those in the active site of HRP-CN which experience substantial hyperfine shifts and paramagnetic relaxation. The magnitude COSY experiment was

Jeffrey S. de Ropp; Liping P. Yu; Gerd N. La Mar

1991-01-01

10

Spin-transfer pathways in paramagnetic lithium transition-metal phosphates from combined broadband isotropic solid-state MAS NMR spectroscopy and DFT calculations.  

PubMed

Substituted lithium transition-metal (TM) phosphate LiFe(x)Mn(1-x)PO(4) materials with olivine-type structures are among the most promising next generation lithium ion battery cathodes. However, a complete atomic-level description of the structure of such phases is not yet available. Here, a combined experimental and theoretical approach to the detailed assignment of the (31)P NMR spectra of the LiFe(x)Mn(1-x)PO(4) (x = 0, 0.25, 0.5, 0.75, 1) pure and mixed TM phosphates is developed and applied. Key to the present work is the development of a new NMR experiment enabling the characterization of complex paramagnetic materials via the complete separation of the individual isotropic chemical shifts, along with solid-state hybrid DFT calculations providing the separate hyperfine contributions of all distinct Mn-O-P and Fe-O-P bond pathways. The NMR experiment, referred to as aMAT, makes use of short high-powered adiabatic pulses (SHAPs), which can achieve 100% inversion over a range of isotropic shifts on the order of 1 MHz and with anisotropies greater than 100 kHz. In addition to complete spectral assignments of the mixed phases, the present study provides a detailed insight into the differences in electronic structure driving the variations in hyperfine parameters across the range of materials. A simple model delimiting the effects of distortions due to Mn/Fe substitution is also proposed and applied. The combined approach has clear future applications to TM-bearing battery cathode phases in particular and for the understanding of complex paramagnetic phases in general. PMID:23004936

Clément, Raphaële J; Pell, Andrew J; Middlemiss, Derek S; Strobridge, Fiona C; Miller, Joel K; Whittingham, M Stanley; Emsley, Lyndon; Grey, Clare P; Pintacuda, Guido

2012-10-17

11

Effects of strong paramagnetic interactions on solid-state deuterium NMR spectra  

NASA Astrophysics Data System (ADS)

The method for analyzing the 2H NMR spectrum affected by strong paramagnetic interaction is discussed. The 2H NMR spectral simulation including the effects of paramagnetic shift and paramagnetic spin-spin relaxation was performed for several molecular motions. The contribution of distant paramagnetic ions to the paramagnetic shift and the effect of anisotropic spin-spin relaxation on the lineshape of the 2H NMR spectrum were investigated by the spectral simulation. The temperature variation of 2H NMR spectrum of [Mn(H 2O) 6][SiF 6] observed by the Exorcycled quadrupole-echo sequence was well reproduced using the proposed method.

Mizuno, Motohiro; Itakura, Naohisa; Endo, Kazunaka

2005-12-01

12

Free-Electron Laser-Powered Electron Paramagnetic Resonance Spectroscopy  

E-print Network

Electron paramagnetic resonance (EPR) spectroscopy interrogates unpaired electron spins in solids and liquids to reveal local structure and dynamics; for example, EPR has elucidated parts of the structure of protein complexes that have resisted all other techniques in structural biology. EPR can also probe the interplay of light and electricity in organic solar cells and light-emitting diodes, and the origin of decoherence in condensed matter, which is of fundamental importance to the development of quantum information processors. Like nuclear magnetic resonance (NMR), EPR spectroscopy becomes more powerful at high magnetic fields and frequencies, and with excitation by coherent pulses rather than continuous waves. However, the difficulty of generating sequences of powerful pulses at frequencies above 100 GHz has, until now, confined high-power pulsed EPR to magnetic fields of 3.5 T and below. Here we demonstrate that ~1 kW pulses from a free-electron laser (FEL) can power a pulsed EPR spectrometer at 240 GHz...

Takahashi, S; Edwards, D T; van Tol, J; Ramian, G; Han, S; Sherwin, M S

2012-01-01

13

NMR Spectroscopy - Theory  

NSDL National Science Digital Library

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

Lord, J. R.

2011-06-30

14

Solid-State NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

Due to the development of new techniques and further increase of magnetic field strength available for commercial applications, solid-state NMR spectroscopy became a routine method for the characterization of zeolites. As an important advantage, solid-state NMR spectroscopy allows the investigation of the local structure of nuclei in the solids under study. The specific behavior of zeolites often depends on local effects, such as framework defects, the substitution of framework atoms, guest compounds etc. Therefore, solid-state NMR spectroscopy is a widely applied analytical method for delivering structure data, which are complementary to those of diffraction methods suitable for investigating the long-range order. While early solid-state NMR spectroscopic studies often focused on the characterization of the zeolite framework in the as-synthesized and hydrated state, an increasing number of recent works is dealing with the investigation of the framework of dehydrated and calcined zeolites and of surface sites, i.e., on the determination of their concentration, strength, and accessibility. In all these applications, the advantage of solid-state NMR spectroscopy to be a quantitative method is utilized. The present chapter demonstrates the fundamentals, various techniques, and most important applications of solid-state NMR spectroscopy making this method to an important tool of research in zeolite science.

Hunger, Michael

15

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

16

"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

17

Probing the surface structure of divalent transition metals using surface specific solid-state NMR spectroscopy.  

PubMed

Environmental and geochemical systems containing paramagnetic species could benefit by using nuclear magnetic resonance (NMR) spectroscopy due to the sensitivity of the spectral response to small amounts paramagnetic interactions. In this study, we apply commonly used solid-state NMR spectroscopic methods combined with chemometrics analysis to probe sorption behavior of the paramagnetic cations Cu(2+) and Ni(2+)at the amorphous silica surface. We exploit the unique properties of paramagnets to derive meaningful structural information in these systems at low, environmentally relevant cation surface loadings by comparing the NMR response of sorption samples to paramagnetic free samples. These data suggest that a simple sorption model where the cation sorbs as inner sphere complexes at negatively charged, deprotonated silanol sites is appropriate. These results help constrain sorption models that are used to describe metal fate and transport. PMID:22316095

Mason, Harris E; Harley, Stephen J; Maxwell, Robert S; Carroll, Susan A

2012-03-01

18

New directions in electron paramagnetic resonance spectroscopy on molecular nanomagnets.  

PubMed

Recent developments and results in the area of electron paramagnetic resonance (EPR) in molecular nanomagnetism are reviewed. Emphasis is placed on unconventional measurement methods, such as frequency-domain magnetic resonance spectroscopy, interferometer-based Fourier-transform, terahertz spectroscopy, and terahertz time-domain spectroscopy. In addition, different methods to investigate EPR by monitoring the change in magnetization or magnetic torque in the presence of microwave radiation are discussed. Finally, an overview is given of application of pulse EPR in investigations of molecular nanomagnets. PMID:22076082

van Slageren, J

2012-01-01

19

Open to closed transition in apo maltose-binding protein visualized by paramagnetic NMR  

E-print Network

Open to closed transition in apo maltose-binding protein visualized by paramagnetic NMR Chun Tang,1 of holo (maltotriose-bound) conformation on the agreement between observed and calculated RDCs for apo MBP, assuming only a single conformation represented by the crystal structure of apo MBP. Fig. S1. Agreement

Clore, G. Marius

20

Open-to-closed transition in apo maltose-binding protein observed by paramagnetic NMR  

E-print Network

LETTERS Open-to-closed transition in apo maltose-binding protein observed by paramagnetic NMR Chun and regulation1­5 . Crystal structures have pro- vided a static picture of the apo (usually open) and holo usually closed) states. The general question arises as to whether the apo state exists as a single species

Clore, G. Marius

21

Sensitivity and resolution enhanced solid-state NMR for paramagnetic systems and biomolecules under very fast magic angle spinning.  

PubMed

Recent research in fast magic angle spinning (MAS) methods has drastically improved the resolution and sensitivity of NMR spectroscopy of biomolecules and materials in solids. In this Account, we summarize recent and ongoing developments in this area by presenting (13)C and (1)H solid-state NMR (SSNMR) studies on paramagnetic systems and biomolecules under fast MAS from our laboratories. First, we describe how very fast MAS (VFMAS) at the spinning speed of at least 20 kHz allows us to overcome major difficulties in (1)H and (13)C high-resolution SSNMR of paramagnetic systems. As a result, we can enhance both sensitivity and resolution by up to a few orders of magnitude. Using fast recycling (?ms/scan) with short (1)H T1 values, we can perform (1)H SSNMR microanalysis of paramagnetic systems on the microgram scale with greatly improved sensitivity over that observed for diamagnetic systems. Second, we discuss how VFMAS at a spinning speed greater than ?40 kHz can enhance the sensitivity and resolution of (13)C biomolecular SSNMR measurements. Low-power (1)H decoupling schemes under VFMAS offer excellent spectral resolution for (13)C SSNMR by nominal (1)H RF irradiation at ?10 kHz. By combining the VFMAS approach with enhanced (1)H T1 relaxation by paramagnetic doping, we can achieve extremely fast recycling in modern biomolecular SSNMR experiments. Experiments with (13)C-labeled ubiquitin doped with 10 mM Cu-EDTA demonstrate how effectively this new approach, called paramagnetic assisted condensed data collection (PACC), enhances the sensitivity. Lastly, we examine (13)C SSNMR measurements for biomolecules under faster MAS at a higher field. Our preliminary (13)C SSNMR data of A? amyloid fibrils and GB1 microcrystals acquired at (1)H NMR frequencies of 750-800 MHz suggest that the combined use of the PACC approach and ultrahigh fields could allow for routine multidimensional SSNMR analyses of proteins at the 50-200 nmol level. Also, we briefly discuss the prospects for studying bimolecules using (13)C SSNMR under ultrafast MAS at the spinning speed of ?100 kHz. PMID:23889329

Parthasarathy, Sudhakar; Nishiyama, Yusuke; Ishii, Yoshitaka

2013-09-17

22

Sensitivity and Resolution Enhanced Solid-state NMR for Paramagnetic Systems and Biomolecules under Very Fast Magic Angle Spinning  

PubMed Central

CONSPECTUS Recent research in fast magic angle spinning (MAS) methods has drastically improved in the resolution and sensitivity for NMR spectroscopy of biomolecules and materials in solids. In this Account, we summarizes recent and ongoing developments in this area by presenting 13C and 1H solid-state NMR (SSNMR) studies on paramagnetic systems and biomolecules under fast MAS from our laboratories. First, we describe how very fast MAS (VFMAS) at the spinning speed of 20 kHz allows us to overcome major difficulties in 1H and 13C high-resolution SSNMR of paramagnetic systems. As a result, we can enhance both sensitivity and resolution by up to a few orders of magnitude. Using fast recycling (~ms/scan) using short 1H T1 values we can perform 1H SSNMR micro-analysis of paramagnetic systems in the ?g scale with greatly improved sensitivity over that for diamagnetic systems. Second, we discuss how VFMAS at a spinning speed greater than ~40 kHz can enhance the sensitivity and resolution of 13C biomolecular SSNMR measurements. Low-power 1H decoupling schemes under VFMAS offer excellent spectral resolution for 13C SSNMR by nominal 1H RF irradiation at ~10 kHz. By combining the VFMAS approach and enhanced 1H T1 relaxation by paramagnetic doping we can achieve extremely fast recycling in modern biomolecular SSNMR experiments. Experiments for 13C-labeled ubiquitin doped with 10 mM Cu-EDTA demonstrate how effectively this new approach, called paramagnetic assisted condensed data collection (PACC), enhances the sensitivity. Lastly, we examine 13C SSNMR measurements for biomolecules under faster MAS at a higher field. Our preliminary 13C SSNMR data of A? amyloid fibrils and GB1 microcrystals acquired at 1H NMR frequencies of 750-800 MHz suggest that the combined use of the PACC approach and the ultra-high fields could allow for routine multi-dimensional SSNMR analyses of proteins at the 50-200 nmol level. Also, we briefly discuss the prospects for studying bimolecules using 13C SSNMR under ultra fast MAS at the spinning speed of ~100 kHz. PMID:23889329

PARTHASARATHY, SUDHAKAR; NISHIYAMA, YUSUKE; ISHII, YOSHITAKA

2013-01-01

23

Understanding the NMR shifts in paramagnetic transition metal oxides using density functional theory calculations  

NASA Astrophysics Data System (ADS)

The 6,7Li MAS NMR spectra of lithium ions in paramagnetic host materials are extremely sensitive to number and nature of the paramagnetic cations in the Li local environments and large shifts (Fermi contact shifts) are often observed. The work presented in this paper aims to provide a rational basis for the interpretation of the 6,7Li NMR shifts, as a function of the lithium local environment and electronic configuration of the transition metal ions. We focus on the layered rocksalts often found for LiMO2 compounds and on materials that are isostructural with the K2NiF4 structure. In order to understand the spin-density transfer mechanism from the transition metal ion to the lithium nucleus, which gives rise to the hyperfine shifts observed by NMR, we have performed density functional theory (DFT) calculations in the generalized gradient approximation. For each compound, we calculate the spin densities values on the transition metal, oxygen and lithium ions and map the spin density in the M-O-Li plane. Predictions of the calculations are in good agreement with several experimental results. We show that DFT calculations are a useful tool with which to interpret the observed paramagnetic shifts in layered oxides and to understand the major spin-density transfer processes. This information should help us to predict the magnitudes and signs of the Li hyperfine shifts for different Li local environments and t2g vs eg electrons in other compounds.

Carlier, D.; Ménétrier, M.; Grey, C. P.; Delmas, C.; Ceder, G.

2003-05-01

24

Accurate Structure and Dynamics of the Metal-Site of Paramagnetic Metalloproteins from NMR Parameters Using Natural Bond Orbitals  

PubMed Central

A natural bond orbital (NBO) analysis of unpaired electron spin density in metalloproteins is presented, which allows a fast and robust calculation of paramagnetic NMR parameters. Approximately 90% of the unpaired electron spin density occupies metal–ligand NBOs, allowing the majority of the density to be modeled by only a few NBOs that reflect the chemical bonding environment. We show that the paramagnetic relaxation rate of protons can be calculated accurately using only the metal–ligand NBOs and that these rates are in good agreement with corresponding rates measured experimentally. This holds, in particular, for protons of ligand residues where the point-dipole approximation breaks down. To describe the paramagnetic relaxation of heavy nuclei, also the electron spin density in the local orbitals must be taken into account. Geometric distance restraints for 15N can be derived from the paramagnetic relaxation enhancement and the Fermi contact shift when local NBOs are included in the analysis. Thus, the NBO approach allows us to include experimental paramagnetic NMR parameters of 15N nuclei as restraints in a structure optimization protocol. We performed a molecular dynamics simulation and structure determination of oxidized rubredoxin using the experimentally obtained paramagnetic NMR parameters of 15N. The corresponding structures obtained are in good agreement with the crystal structure of rubredoxin. Thus, the NBO approach allows an accurate description of the geometric structure and the dynamics of metalloproteins, when NMR parameters are available of nuclei in the immediate vicinity of the metal-site. PMID:22329704

2012-01-01

25

Solution structure and dynamics of the complex between cytochrome c and cytochrome c peroxidase determined by paramagnetic NMR  

PubMed Central

The physiological complex of yeast cytochrome c peroxidase and iso-1-cytochrome c is a paradigm for biological electron transfer. Using paramagnetic NMR spectroscopy, we have determined the conformation of the protein complex in solution, which is shown to be very similar to that observed in the crystal structure [Pelletier H, Kraut J (1992) Science 258:1748–1755]. Our results support the view that this transient electron transfer complex is dynamic. The solution structure represents the dominant protein–protein orientation, which, according to our estimates, is occupied for >70% of the lifetime of the complex, with the rest of the time spent in the dynamic encounter state. Based on the observed paramagnetic effects, we have delineated the conformational space sampled by the protein molecules during the dynamic part of the interaction, providing experimental support for the theoretical predictions of the classical Brownian dynamics study [Northrup SH, Boles JO, Reynolds JCL (1988) Science 241:67–70]. Our findings corroborate the dynamic behavior of this complex and offer an insight into the mechanism of the protein complex formation in solution. PMID:17146057

Volkov, Alexander N.; Worrall, Jonathan A. R.; Holtzmann, Elodie; Ubbink, Marcellus

2006-01-01

26

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...

27

?-NMR study of isolated 8Li+ in the enhanced paramagnet platinum  

NASA Astrophysics Data System (ADS)

We report ?-detected nuclear magnetic resonance (?-NMR) measurements of 8Li+ implanted into high purity Pt. The frequency of the 8Li ?-NMR resonance and the spin-lattice relaxation rates 1/T1 were measured at temperatures ranging from 3 to 300 K. Remarkably, both the spin-lattice relaxation rate and the Knight shift K depend linearly on temperature T although the bulk susceptibility does not. K is found to scale with the Curie-Weiss dependence of the Pt susceptibility extrapolated to low temperatures. This is attributed to a defect response of the enhanced paramagnetism of Pt, i.e., the presence of the interstitial Li+ locally relieves the tendency for the Curie-Weiss susceptibility to saturate at low T. We propose that the low temperature saturation in ? of Pt may be related to an interband coupling between the s and d bands that is disrupted locally by the presence of the Li+.

Ofer, Oren; Chow, K. H.; Fan, I.; Egilmez, M.; Parolin, T. J.; Hossain, M. D.; Jung, J.; Salman, Z.; Kiefl, R. F.; Levy, C. D. P.; Morris, G. D.; Pearson, M. R.; Saadaoui, H.; Song, Q.; Wang, D.; MacFarlane, W. A.

2012-08-01

28

The effect of paramagnetic manganese cations on 1 H MR spectroscopy of the brain  

E-print Network

The effect of paramagnetic manganese cations on 1 H MR spectroscopy of the brain K. S. Madsen1 properties of divalent manganese cations (Mn2+ ) and their in vivo resemblance to calcium cations (Ca2+ ) has

29

Drastic sensitivity enhancement in 29Si MAS NMR of zeolites and mesoporous silica materials by paramagnetic doping of Cu2+.  

PubMed

The paramagnetic doping of Cu(2+) in both mesoporous silica materials and microporous silicate crystals (zeolites) can be used effectively to enhance the signal intensity of (29)Si solid state magic angle spinning NMR, as a result of shortening of the spin-lattice relaxation time, T1, by the paramagnetic effect, because of the Cu(2+) electronic relaxation time in the range of 10(-8) s. This leads to drastically reduced data-collection times, typically 80-fold shorter than that in mesoporous silica. We found that the estimated range of the paramagnetic effect of Cu(2+) doping in porous silicates was at least 1 nm. PMID:23824320

Inagaki, Satoshi; Kawamura, Izuru; Sasaki, Yukichi; Yoshida, Kaname; Kubota, Yoshihiro; Naito, Akira

2013-08-28

30

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

31

An Introduction to Biological NMR Spectroscopy*  

PubMed Central

NMR spectroscopy is a powerful tool for biologists interested in the structure, dynamics, and interactions of biological macromolecules. This review aims at presenting in an accessible manner the requirements and limitations of this technique. As an introduction, the history of NMR will highlight how the method evolved from physics to chemistry and finally to biology over several decades. We then introduce the NMR spectral parameters used in structural biology, namely the chemical shift, the J-coupling, nuclear Overhauser effects, and residual dipolar couplings. Resonance assignment, the required step for any further NMR study, bears a resemblance to jigsaw puzzle strategy. The NMR spectral parameters are then converted into angle and distances and used as input using restrained molecular dynamics to compute a bundle of structures. When interpreting a NMR-derived structure, the biologist has to judge its quality on the basis of the statistics provided. When the 3D structure is a priori known by other means, the molecular interaction with a partner can be mapped by NMR: information on the binding interface as well as on kinetic and thermodynamic constants can be gathered. NMR is suitable to monitor, over a wide range of frequencies, protein fluctuations that play a crucial role in their biological function. In the last section of this review, intrinsically disordered proteins, which have escaped the attention of classical structural biology, are discussed in the perspective of NMR, one of the rare available techniques able to describe structural ensembles. This Tutorial is part of the International Proteomics Tutorial Programme (IPTP 16 MCP). PMID:23831612

Marion, Dominique

2013-01-01

32

Presentation of Membrane-Anchored Glycosphingolipids Determined from Molecular Dynamics Simulations and NMR Paramagnetic Relaxation Rate Enhancement  

PubMed Central

Challenges for structural characterization of membrane-bound glycosphingolipids include their high internal dynamic motions and their physical proximity to membrane surfaces. Here we demonstrate that NMR paramagnetic relaxation enhancement can be used, alongside independent molecular dynamics simulations and an outer-sphere relaxation model, to quantitatively characterize the presentation (insertion depth and orientation relative to a membrane surface) of ganglioside GM1 in biologically relevant membrane environments. Longitudinal and transverse paramagnetic relaxation enhancement effects were measured for GM1, anchored to phospholipid bicelles, using both water-soluble and membrane-anchored paramagnetic probes, respectively. A method was developed to rapidly calculate paramagnetic relaxation enhancement effects from thousands of structures taken from a simulation of GM1 in a phospholipid bilayer. The combined computational and experimental approach yielded experimentally verified atomic-resolution 3D models of a highly plastic membrane-bound biomolecule. PMID:20058858

DeMarco, Mari L.; Woods, Robert J.; Prestegard, James H.; Tian, Fang

33

Perfluorooctyl bromide has limited membrane solubility and is located at the bilayer center. Locating small molecules in lipid bilayers through paramagnetic enhancements of NMR relaxation.  

PubMed

There is considerable interest in the use of perfluorocarbons as oxygen carriers in clinical settings; however, little is known regarding the molecular interactions made by these apolar compounds with biological membranes or their effect on membrane structure. NMR spectroscopy was used to investigate the interaction of perfluorooctyl bromide (PFOB) with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers. (19)F NMR spectra demonstrate that PFOB partitions into POPC bilayers but that it saturates at a remarkably low membrane concentration of approximately 2 mol %. (19)F chemical shifts indicate that this membrane-bound PFOB experiences a local environment similar in polarity to that of hexane, suggesting that the compound resides within the hydrocarbon core of the lipid bilayer. This hydrocarbon location was refined by measuring paramagnetic enhancements of (19)F nuclear relaxation for membrane-bound PFOB produced by Gd(3+) and O(2). The data clearly localize PFOB to the center of the membrane hydrocarbon and show how paramagnetic enhancements of nuclear relaxation produced by O(2) may be used to localize small molecules within bilayers. (2)H and (31)P NMR experiments demonstrate that PFOB produces no significant changes in either acyl chain or headgroup structure even at saturating membrane concentrations. PMID:12459021

Ellena, Jeffrey F; Obraztsov, Viktor V; Cumbea, Valerie L; Woods, Catherine M; Cafiso, David S

2002-12-01

34

Multidimensional NMR Spectroscopy DOI: 10.1002/anie.200805612  

E-print Network

Multidimensional NMR Spectroscopy DOI: 10.1002/anie.200805612 Single-Scan 2D Hadamard NMR resonance (2D NMR) experiments has been a topic of intense research during the past years.[1] Proposals as compressing the 2D NMR experiment into a single-scan by spatially encoding the indirect-domain interactions.[3

Frydman, Lucio

35

A review of Blind Source Separation in NMR Spectroscopy  

E-print Network

M to �M for classical NMR ). Remarkably, the resolution of 2D NMR spectra is such that even by visA review of Blind Source Separation in NMR Spectroscopy Ichrak Toumi, Stefano Caldarelli iSm2, UMR naturally associated to most NMR experi- ments. Notable exceptions are Pulse Field Gradient and relaxation

36

Ultrafast two-dimensional NMR spectroscopy using constant acquisition gradients  

E-print Network

and on continuously flowing samples, as well as the utilization of 2D NMR to follow dynamic biophysical and metabolicUltrafast two-dimensional NMR spectroscopy using constant acquisition gradients Yoav Shrot NMR spectroscopy plays an important role in the characterization of molecular structure and dynamics

Frydman, Lucio

37

Spatially resolved multidimensional NMR spectroscopy within a single scan  

E-print Network

-dimensional (2D) NMR experiments can in fact provide a weighted spatial distribution of the analyte originating where the potential of spatially resolved ultrafast 2D NMR spectroscopy is brought to bear are presented. All rights reserved. Keywords: Magnetic resonance spectroscopy; 2D 1 H NMR; Spatial localization

Frydman, Lucio

38

Fast multidimensional NMR spectroscopy for sparse spectra.  

PubMed

Multidimensional NMR spectroscopy is widely used for studies of molecular and biomolecular structure. A major disadvantage of multidimensional NMR is the long acquisition time which, regardless of sensitivity considerations, may be needed to obtain the final multidimensional frequency domain coefficients. In this article, a method for under-sampling multidimensional NMR acquisition of sparse spectra is presented. The approach is presented in the case of two-dimensional NMR acquisitions. It relies on prior knowledge about the support in the two-dimensional frequency domain to recover an over-determined system from the under-determined system induced in the linear acquisition model when under-sampled acquisitions are performed. This over-determined system can then be solved with linear least squares. The prior knowledge is obtained efficiently at a low cost from the one-dimensional NMR acquisition, which is generally acquired as a first step in multidimensional NMR. If this one-dimensional acquisition is intrinsically sparse, it is possible to reconstruct the corresponding two-dimensional acquisition from far fewer observations than those imposed by the Nyquist criterion, and subsequently to reduce the acquisition time. Further improvements are obtained by optimizing the sampling procedure for the least-squares reconstruction using the sequential backward selection algorithm. Theoretical and experimental results are given in the case of a traditional acquisition scheme, which demonstrate reliable and fast reconstructions with acceleration factors in the range 3-6. The proposed method outperforms the CS methods (OMP, L1) in terms of the reconstruction performance, implementation and computation time. The approach can be easily extended to higher dimensions and spectroscopic imaging. PMID:24664959

Merhej, Dany; Ratiney, Hélène; Diab, Chaouki; Khalil, Mohamad; Sdika, Michaël; Prost, Rémy

2014-06-01

39

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. PMID:9050830

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

1997-01-01

40

Magnetism, optical absorbance, and 19F NMR spectra of nafion films with self-assembling paramagnetic networks  

SciTech Connect

Magnetization, optical absorbance, and {sup 19}F NMR spectra of Nafion transparent films as received and doped with Mn{sup 2+}, Co{sup 2+}, Fe{sup 2+}, and Fe{sup 3+} ions with and without treatment in 1H-1,2,4-triazole (trz) have been studied. Doping of Nafion with Fe{sup 2+} and Co{sup 2+} and their bridging to nitrogen of triazole yields a hybrid self-assembling paramagnetic system that exhibits interesting magnetic and optical properties. These include spin crossover phenomena between high-spin (HS) and low-spin (LS) states in Nafion-Fe{sup 2+}-trz and Nafion-Co{sup 2+}-trz accompanied by thermochromic effects in the visible range induced by temperature. A large shift of the magnetization curve induced by a magnetic field in the vicinity of the HS {leftrightarrow} LS, {approx}220 K, observed for Nafion-Fe{sup 2+}-trz has a rate of {approx}6 K/kOe, which is about three orders of magnitude larger than that in bulk spin crossover Fe{sup 2+} materials. Selective response of {sup 19}F NMR signals on doping with paramagnetic ions demonstrates that NMR can be used as spatially resolved method to study Nafion film with paramagnetic network. Both chemical shift and width of {sup 19}F NMR signals show that SO groups of Nafion, Fe or Co ions, and nitrogen of triazole are bonded whereas they form a spin crossover system. Based on a model of nanosize cylinders proposed for Nafion [K. Schmidt-Rohr and Q. Chen, Nat Mater (2008), 75], we suggest that paramagnetic ions are located inside these cylinders, forming self-assembling magnetically and optically active nanoscale networks.

Levin, E. M.; Chen, Q.; Bud'ko, S. L.

2012-01-15

41

Optimal control in NMR spectroscopy: Numerical implementation in SIMPSON  

Microsoft Academic Search

We present the implementation of optimal control into the open source simulation package SIMPSON for development and optimization of nuclear magnetic resonance experiments for a wide range of applications, including liquid- and solid-state NMR, magnetic resonance imaging, quantum computation, and combinations between NMR and other spectroscopies. Optimal control enables efficient optimization of NMR experiments in terms of amplitudes, phases, offsets

Zden?k Tošner; Thomas Vosegaard; Cindie Kehlet; Navin Khaneja; Steffen J. Glaser; Niels Chr. Nielsen

2009-01-01

42

Communication Single-scan 2D DOSY NMR spectroscopy  

E-print Network

Communication Single-scan 2D DOSY NMR spectroscopy Yoav Shrot, Lucio Frydman * Department. Introduction Two-dimensional nuclear magnetic resonance (2D NMR) plays a fundamental role in expanding on the principles and applications of the resulting 2D diffusion-shift NMR correlation experiment, have been given

Frydman, Lucio

43

Measurement of electron paramagnetic resonance using terahertz time-domain spectroscopy.  

PubMed

We present a frequency-domain electron spin resonance (ESR) measurement system using terahertz time-domain spectroscopy. A crossed polarizer technique is utilized to increase the sensitivity in detecting weak ESR signals of paramagnets caused by magnetic dipole transitions between magnetic sublevels. We demonstrate the measurements of ESR signal of paramagnetic copper(II) sulfate pentahydrate with uniaxial anisotropy of the g-factor under magnetic fields up to 10 T. The lineshape of the obtained ESR signals agrees well with the theoretical predictions for a powder sample with the uniaxial anisotropy. PMID:22273888

Kozuki, Kohei; Nagashima, Takeshi; Hangyo, Masanori

2011-12-01

44

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

ERIC Educational Resources Information Center

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

Mills, Nancy S.; Shanklin, Michael

2011-01-01

45

Characterization of ?-ray induced paramagnetic centers in bayerite by means of EPR and ENDOR spectroscopies  

Microsoft Academic Search

Four different paramagnetic centers, induced in bayerite samples by irradiation, have been characterized by EPR and ENDOR spectroscopies. Two of them, respectively, of V- and F-types, have been found to be mobile at room temperature and frozen at lower temperature. The first one, with g1= 2.021±0.002, g2=2.010±0.005, and g3=2.005±0.002, is identified with an O? species stemming from the ionization of

Eric G. Derouane; Jacques C. Vedrine

1976-01-01

46

Mobility and relaxation determinations of lithium in lithium aluminate ceramics using solid-state NMR spectroscopy  

SciTech Connect

Lithium aluminate is one of the materials being considered for fusion reactor blankets. When preparing the ceramic, it is important to be able to monitor the microstructures since it is a controlling factor in the rate of tritium release from the blanket. Nuclear magnetic resonance spectroscopy (NMR) has been shown to be a useful tool for the nondestructive analysis of ceramics. Studies detailed in this paper include spectral acquisition, assignment, spin-lattice relaxation time measurements, temperature effects, their correlation to structure, and material purity. The ceramic of interest was lithium aluminate, LiAl{sub 5}O{sub 8}. This material was studied by observation of the NMR active nuclei {sup 6}Li, {sup 7}Li, and {sup 27}Al. For these nuclei, spin-lattice relaxation times (T{sub 1}) were measured and were found to vary considerably, correlating to the presence of paramagnetic impurities within the crystalline lattice. Previous research has shown that the coordination about the aluminum nucleus can be determined using {sup 27}Al NMR spectroscopy. Aluminum-27 NMR spectroscopy was successfully applied, and it provided valuable insight into composition of the ceramic. 20 refs., 4 figs., 3 tabs.

Stewart, F.F.; Peterson, E.S. [Idaho National Engineering Lab., Idaho Falls, ID (United States); Stebbins, J.F. [Stanford Univ., CA (United States)] [and others

1995-02-01

47

Determination of the geometric structure of the metal site in a blue copper protein by paramagnetic NMR  

PubMed Central

The biological function of metalloproteins is closely tied to the geometric and electronic structures of the metal sites. Here, we show that the geometric structure of the metal site of a metalloprotein in solution can be determined from experimentally measured electron-nuclear spin–spin interactions obtained by NMR. Thus, the geometric metal site structure of plastocyanin from Anabaena variabilis was determined by including the paramagnetic relaxation enhancement of protons close to the copper site as restraints in a conventional NMR structure determination, together with the distribution of the unpaired electron onto the ligand atoms. Also, the interproton distances (nuclear Overhauser enhancements) and dihedral angles (scalar nuclear spin–spin couplings) normally used in NMR structure determinations were included as restraints. The structure calculations were carried out with the program x-plor and a module that takes into account the specific characteristics of the paramagnetic restraints. A well defined metal site structure was obtained with the structural characteristics of the blue copper site, including a distorted tetrahedral geometry, a short Cu–Cys S? bond, and a long Cu–Met S? bond. Overall, the agreement of the obtained metal site structure of Anabaena variabilis plastocyanin with those of other plastocyanins obtained by x-ray crystallography confirms the reliability of the approach. PMID:16446449

Hansen, D. Flemming; Led, Jens J.

2006-01-01

48

Approaches to localized NMR spectroscopy in vivo  

SciTech Connect

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

Garwood, M.G.

1985-01-01

49

WebSpectra: 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 13C NMR, DEPT, COSY and IR spectra of various compounds for students to interpret.

50

NMR Analysis of Unknowns: An Introduction to 2D NMR Spectroscopy  

ERIC Educational Resources Information Center

A study combined 1D (one-dimensional) and 2D (two-dimensional) NMR spectroscopy to solve structural organic problems of three unknowns, which include 2-, 3-, and 4-heptanone. Results showed [to the first power]H NMR and [to the thirteenth power]C NMR signal assignments for 2- and 3-heptanone were more challenging than for 4-heptanone owing to the…

Alonso, David E.; Warren, Steven E.

2005-01-01

51

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

52

Solenoidal and planar microcoils for NMR spectroscopy  

Microsoft Academic Search

The extraction of nuclear magnetic resonance (NMR) spectra of samples having smaller and smaller volumes is a real challenge. Reductions of volume are dictated by the difficulties of production of sufficiently large samples or by necessities of miniaturization of the analyzing system. In both cases a careful design of the radiofrequency (RF) coil, ensuring an optimum reception of the NMR

M. Armenean; O. Beuf; L. Renaud; H. Saint-Jalmes

2003-01-01

53

Paramagnetic 13C and 15N NMR analyses of cyanide- (13C15N-) ligated ferric peroxidases: the push effect, not pull effect, modulates the compound I formation rate.  

PubMed

Paramagnetic (13)C and (15)N NMR spectroscopy of heme-bound cyanide ((13)C(15)N) was utilized to quantitatively distinguish the electron donor effect (the push effect) from the proximal histidine and hydrogen-bonding effect (the pull effect) from the distal amino acid residues in cytochrome c peroxidase (CcP), ascorbate peroxidase (APX), lignin peroxidase (LiP), and manganese peroxidase (MnP). Paramagnetic (13)C NMR signals of heme-bound (13)C(15)N of these peroxidases were observed in a wide range, -3501 ppm (CcP), -3563 ppm (APX), -3823 ppm (MnP), and -3826 ppm (LiP), while paramagnetic (15)N NMR signals of those were detected in a narrow range, 574 ppm (ARP), 605 ppm (CcP), 626 ppm (LiP), and 654 ppm (MnP). Detailed analysis, combined with the previous results for horseradish peroxidase and Arthromyces ramosus peroxidase, indicated that the push effect is quite different among these peroxidases while the pull effect is similar. More importantly, a strong correlation between the (13)C NMR shift (the push effect) and the compound I formation rate was observed, indicating that the push effect causes a variation in the compound I formation rate. Comparison of the (13)C and (15)N NMR results of these peroxidases with their crystal structures suggests that the orientation of the proximal imidazole plane to the heme N-Fe-N axis controls the push effect and the compound I formation rate of peroxidase. PMID:19187033

Nonaka, Daisuke; Wariishi, Hiroyuki; Fujii, Hiroshi

2009-02-10

54

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. PMID:14679498

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

2006-01-01

55

Characterisation of ?-tricalcium phosphate-based bone substitute materials by electron paramagnetic resonance spectroscopy  

NASA Astrophysics Data System (ADS)

?-TCP based materials are frequently used as dental implants. Due to their resorption in the body and direct contact with tissues, in order to inactivate bacteria, fungal spores and viruses, they are usually sterilized by ?-irradiation. However, the current literature provides little information about effects of the ?-irradiation on the formation and stability of the free radicals in the bone graft materials during and after sterilization procedure. In this work five different bone graft substitution materials, composed of synthetic beta tricalcium phosphate (?-TCP) and hydroxyapatite (HAP) present in the market were characterized by electron paramagnetic resonance (EPR) spectroscopy, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Paramagnetic species Mn2+, Fe3+, trapped H-atoms and CO2- radicals were detected in the biphasic material (60% HAP, 40% ?-TCP), while in ?-TCP materials only Mn2+ andor trapped hydrogen atoms were detected. EPR analysis revealed the details of the structure of these materials at the atomic level. The results have shown that EPR spectroscopy is a method which can be used to improve the quality control of bone graft materials after syntering, processing and sterilization procedure.

Matkovi?, Ivo; Maltar-Strme?ki, Nadica; Babi?-Ivan?i?, Vesna; Dutour Sikiri?, Maja; Noethig-Laslo, Vesna

2012-10-01

56

High field electron paramagnetic resonance spectroscopy under ultrahigh vacuum conditions—A multipurpose machine to study paramagnetic species on well defined single crystal surfaces  

NASA Astrophysics Data System (ADS)

A new ultrahigh vacuum (UHV) electron paramagnetic resonance (EPR) spectrometer operating at 94 GHz to investigate paramagnetic centers on single crystal surfaces is described. It is particularly designed to study paramagnetic centers on well-defined model catalysts using epitaxial thin oxide films grown on metal single crystals. The EPR setup is based on a commercial Bruker E600 spectrometer, which is adapted to ultrahigh vacuum conditions using a home made Fabry Perot resonator. The key idea of the resonator is to use the planar metal single crystal required to grow the single crystalline oxide films as one of the mirrors of the resonator. EPR spectroscopy is solely sensitive to paramagnetic species, which are typically minority species in such a system. Hence, additional experimental characterization tools are required to allow for a comprehensive investigation of the surface. The apparatus includes a preparation chamber hosting equipment, which is required to prepare supported model catalysts. In addition, surface characterization tools such as low energy electron diffraction (LEED)/Auger spectroscopy, temperature programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS) are available to characterize the surfaces. A second chamber used to perform EPR spectroscopy at 94 GHz has a room temperature scanning tunneling microscope attached to it, which allows for real space structural characterization. The heart of the UHV adaptation of the EPR experiment is the sealing of the Fabry-Perot resonator against atmosphere. To this end it is possible to use a thin sapphire window glued to the backside of the coupling orifice of the Fabry Perot resonator. With the help of a variety of stabilization measures reducing vibrations as well as thermal drift it is possible to accumulate data for a time span, which is for low temperature measurements only limited by the amount of liquid helium. Test measurements show that the system can detect paramagnetic species with a density of approximately 5 × 1011 spins/cm2, which is comparable to the limit obtained for the presently available UHV-EPR spectrometer operating at 10 GHz (X-band). Investigation of electron trapped centers in MgO(001) films shows that the increased resolution offered by the experiments at W-band allows to identify new paramagnetic species, that cannot be differentiated with the currently available methodology.

Rocker, J.; Cornu, D.; Kieseritzky, E.; Seiler, A.; Bondarchuk, O.; Hänsel-Ziegler, W.; Risse, T.; Freund, H.-J.

2014-08-01

57

High field electron paramagnetic resonance spectroscopy under ultrahigh vacuum conditions--a multipurpose machine to study paramagnetic species on well defined single crystal surfaces.  

PubMed

A new ultrahigh vacuum (UHV) electron paramagnetic resonance (EPR) spectrometer operating at 94 GHz to investigate paramagnetic centers on single crystal surfaces is described. It is particularly designed to study paramagnetic centers on well-defined model catalysts using epitaxial thin oxide films grown on metal single crystals. The EPR setup is based on a commercial Bruker E600 spectrometer, which is adapted to ultrahigh vacuum conditions using a home made Fabry Perot resonator. The key idea of the resonator is to use the planar metal single crystal required to grow the single crystalline oxide films as one of the mirrors of the resonator. EPR spectroscopy is solely sensitive to paramagnetic species, which are typically minority species in such a system. Hence, additional experimental characterization tools are required to allow for a comprehensive investigation of the surface. The apparatus includes a preparation chamber hosting equipment, which is required to prepare supported model catalysts. In addition, surface characterization tools such as low energy electron diffraction (LEED)/Auger spectroscopy, temperature programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS) are available to characterize the surfaces. A second chamber used to perform EPR spectroscopy at 94 GHz has a room temperature scanning tunneling microscope attached to it, which allows for real space structural characterization. The heart of the UHV adaptation of the EPR experiment is the sealing of the Fabry-Perot resonator against atmosphere. To this end it is possible to use a thin sapphire window glued to the backside of the coupling orifice of the Fabry Perot resonator. With the help of a variety of stabilization measures reducing vibrations as well as thermal drift it is possible to accumulate data for a time span, which is for low temperature measurements only limited by the amount of liquid helium. Test measurements show that the system can detect paramagnetic species with a density of approximately 5 × 10(11) spins/cm(2), which is comparable to the limit obtained for the presently available UHV-EPR spectrometer operating at 10 GHz (X-band). Investigation of electron trapped centers in MgO(001) films shows that the increased resolution offered by the experiments at W-band allows to identify new paramagnetic species, that cannot be differentiated with the currently available methodology. PMID:25173280

Rocker, J; Cornu, D; Kieseritzky, E; Seiler, A; Bondarchuk, O; Hänsel-Ziegler, W; Risse, T; Freund, H-J

2014-08-01

58

{sup 13}C and {sup 31}P NMR study of paramagnetic lanthanide(III) texaphyrins  

SciTech Connect

{sup 13}C NMR was used to study the rare earth complexes, LnTx(NO{sub 3}){sub 2} (Ln = La, Ce, Pr, Nd, Eu, Y; Tx = texaphyrins). The authors present {sup 31}P NMR spectra for rare earth diphenyl phosphonates.

Lisowski, J.; Sessler, J.L.; Mody, T.D. [Univ. of Texas, Austin, TX (United States)

1995-08-16

59

Assignment of heme methyl 1H-NMR resonances of high-spin and low-spin ferric complexes of cytochrome p450cam using one-dimensional and two-dimensional paramagnetic signals enhancement (PASE) magnetization transfer experiments.  

PubMed

An 1H-NMR study of ferric cytochrome P450cam in different paramagnetic states was performed. Assignment of three heme methyl resonances of the isocyanide adduct of cytochrome P450 in the ferric low-spin state was recently performed using electron exchange in the presence of putidaredoxin [Mouro, C., Bondon, A., Jung, C., Hui Bon Hoa, G., De Certaines, J.D., Spencer, R.G.S. & Simonneaux, G. (1999) FEBS Lett. 455, 302-306]. In this study, heme methyl protons of cytochrome P450 in the native high-spin and low-spin states were assigned through one-dimensional and two-dimensional magnetization transfer spectroscopy using the paramagnetic signals enhancement (PASE) method. The order of the methyl proton chemical shifts is inverted between high-spin and low-spin states. The methyl order observed in the ferric low-spin isocyanide complexes is related to the orientation of the cysteinate ligand. PMID:10601869

Mouro, C; Bondon, A; Jung, C; De Certaines, J D; Simonneaux, G

2000-01-01

60

NMR study of thermally activated paramagnetism in metallic low-silica X zeolite filled with sodium atoms  

NASA Astrophysics Data System (ADS)

We report a 23Na and 27Al nuclear magnetic resonance (NMR) investigation of low-silica X (LSX) zeolite with chemical formula Na12Al12Si12O48 (Na12-LSX) loaded with n additional guest sodium atoms. Nan/Na12-LSX exhibits an insulator-to-metal transition around n=11.6, which is accompanied by a significant enhancement of bulk magnetic susceptibility. Paramagnetic moments are in the metallic Na12/Na12-LSX thermally activated with an activation energy of around 0.1 eV. Simultaneously a new shifted component appears in the 23Na NMR, whose large and positive NMR shift scales with bulk magnetic susceptibility. Its spin-lattice relaxation rate 1/T1 is governed by the local-field fluctuations characterized by the same activation energy as obtained from the bulk magnetic susceptibility data. The time scale of these fluctuations is typical for atomic motions, which suggest strong electron-phonon coupling, a hallmark of polaron states. The insulator-to-metal transition in Nan/Na12-LSX is thus discussed within a polaron model.

Igarashi, Mutsuo; Nakano, Takehito; Thi, Pham Tan; Nozue, Yasuo; Goto, Atsushi; Hashi, Kenjiro; Ohki, Shinobu; Shimizu, Tadashi; Krajnc, Andraž; Jegli?, Peter; Ar?on, Denis

2013-02-01

61

Electron paramagnetic resonance spectroscopy in radiation research: Current status and perspectives  

PubMed Central

Exposure to radiation leads to a number of health-related malfunctions. Ionizing radiation is more harmful than non-ionizing radiation, as it causes both direct and indirect effects. Irradiation with ionizing radiation results in free radical-induced oxidative stress. Free radical-mediated oxidative stress has been implicated in a plethora of diseased states, including cancer, arthritis, aging, Parkinson's disease, and so on. Electron Paramagnetic Resonance (EPR) spectroscopy has various applications to measure free radicals, in radiation research. Free radicals disintegrate immediately in aqueous environment. Free radicals can be detected indirectly by the EPR spin trapping technique in which these forms stabilize the radical adduct and produce characteristic EPR spectra for specific radicals. Ionizing radiation-induced free radicals in calcified tissues, for example, teeth, bone, and fingernail, can be detected directly by EPR spectroscopy, due to their extended stability. Various applications of EPR in radiation research studies are discussed in this review. PMID:21814437

Rana, Sudha; Chawla, Raman; Kumar, Raj; Singh, Shefali; Zheleva, Antoaneta; Dimitrova, Yanka; Gadjeva, Veselina; Arora, Rajesh; Sultana, Sarwat; Sharma, Rakesh Kumar

2010-01-01

62

Microfabrication of Helmholtz Coils with Integrated Channels for NMR Spectroscopy  

Microsoft Academic Search

A new technology for the microfabrication of Helmholtz microcoils with integrated SU-8 channels for NMR spectroscopy is presented. These Helmholtz microcoils demonstrate superior NMR performance regarding spin excitation uniformity compared to planar microcoils. The improved spin excitation uniformity opens the way to advanced chemical analysis using complex RF-pulse sequences. The fabricated Helmholtz coils have Q-factor greater than 20 due to

K. Ehrmann; N. Saillen; F. Vincent; C. Massin; P.-A. Besse; R. S. Popovic

2006-01-01

63

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. PMID:22545175

Peng, J.W.

2012-01-01

64

High resolution NMR spectroscopy in the Earth's magnetic field  

NASA Astrophysics Data System (ADS)

High resolution nuclear magnetic resonance (NMR) spectroscopy at high magnetic fields has developed into a most powerful tool for the determination of molecular structures. The dream is a mobile molecular low field NMR scanner which allows the determination of molecular structures. Until to now at low magnetic fields NMR spectroscopy suffers from the low signal to noise ratio (S/N) and from the lack of access to chemical information in terms of chemical shifts and homo-nuclear J-couplings. We demonstrate that chemical analysis of liquids is possible by mobile ultrahigh-resolution ^1H, ^19F and ^129Xe NMR spectroscopy in the Earth's magnetic field. The ^129Xe chemical shift in liquids is determined in the Earth's magnetic field with a precision comparable to that obtained by superconducting magnets. The ^1H and ^19F NMR spectra allow the determination of hetero-nuclear J-coupling constants with an accuracy of a few mHz. Very fine details of the molecular structure which are not observable with conventional superconducting magnets can be discriminated. For molecules where a rare spin such as carbon ^13C is present the high-resolution low-field ^1H NMR spectrum indeed reveal all hetero- and homo-nuclear J-couplings. All these results open the door for the mobile study of molecular structures as well as for the online monitoring of chemical reactions at ultra-low magnetic fields.

Appelt, Stephan

2007-03-01

65

Nanoscale NMR Spectroscopy and Imaging of Multiple Nuclear Species  

E-print Network

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are well-established techniques that provide valuable information in a diverse set of disciplines but are currently limited to macroscopic sample volumes. Here we demonstrate nanoscale NMR spectroscopy and imaging under ambient conditions of samples containing multiple nuclear species, using nitrogen-vacancy (NV) colour centres in diamond as sensors. With single, shallow NV centres in a diamond chip and samples placed on the diamond surface, we perform NMR spectroscopy and one-dimensional MRI on few-nanometre-sized samples containing $^1$H and $^{19}$F nuclei. Alternatively, we employ a high-density NV layer near the surface of a diamond chip to demonstrate wide-field optical NMR spectroscopy of nanoscale samples containing $^1$H, $^{19}$F, and $^{31}$P nuclei, as well as multi-species two-dimensional optical MRI with sub-micron resolution. For all diamond samples exposed to air, we identify a ubiquitous $^1$H NMR signal, consistent with a $\\sim 1$ nm layer of adsorbed hydrocarbons or water on the diamond surface and below any sample placed on the diamond. This work lays the foundation for nanoscale NMR and MRI applications such as studies of single proteins and functional biological imaging with subcellular resolution, as well as characterization of thin films with sub-nanometre resolution.

Stephen J. DeVience; Linh M. Pham; Igor Lovchinsky; Alexander O. Sushkov; Nir Bar-Gill; Chinmay Belthangady; Francesco Casola; Madeleine Corbett; Huiliang Zhang; Mikhail Lukin; Hongkun Park; Amir Yacoby; Ronald L. Walsworth

2014-06-12

66

SEAL by NMR: Glyco-Based Selenium-Labeled Affinity Ligands Detected by NMR Spectroscopy.  

PubMed

We report a method for the screening of interactions between proteins and selenium-labeled carbohydrate ligands. SEAL by NMR is demonstrated with selenoglycosides binding to lectins where the selenium nucleus serves as an NMR-active handle and reports on binding through (77) Se NMR spectroscopy. In terms of overall sensitivity, this nucleus is comparable to (13) C?NMR, while the NMR spectral width is ten times larger, yielding little overlap in (77) Se NMR spectroscopy, even for similar compounds. The studied ligands are singly selenated bioisosteres of methyl glycosides for which straightforward preparation methods are at hand and libraries can readily be generated. The strength of the approach lies in its simplicity, sensitivity to binding events, the tolerance to additives and the possibility of having several ligands in the assay. This study extends the increasing potential of selenium in structure biology and medicinal chemistry. We anticipate that SEAL by NMR will be a beneficial tool for the development of selenium-based bioactive compounds, such as glycomimetic drug candidates. PMID:25196366

Hamark, Christoffer; Landström, Jens; Widmalm, Göran

2014-10-20

67

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

EPA Science Inventory

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

68

Searching for protein binding sites from Molecular Dynamics simulations and paramagnetic fragment-based NMR studies.  

PubMed

Hotspot delineation on protein surfaces represents a fundamental step for targeting protein-protein interfaces. Disruptors of protein-protein interactions can be designed provided that the sterical features of binding pockets, including the transient ones, can be defined. Molecular Dynamics, MD, simulations have been used as a reliable framework for identifying transient pocket openings on the protein surface. Accessible surface area and intramolecular H-bond involvement of protein backbone amides are proposed as descriptors for characterizing binding pocket occurrence and evolution along MD trajectories. TEMPOL induced paramagnetic perturbations on (1)H-(15)N HSQC signals of protein backbone amides have been analyzed as a fragment-based search for surface hotspots, in order to validate MD predicted pockets. This procedure has been applied to CXCL12, a small chemokine responsible for tumor progression and proliferation. From combined analysis of MD data and paramagnetic profiles, two CXCL12 sites suitable for the binding of small molecules were identified. One of these sites is the already well characterized CXCL12 region involved in the binding to CXCR4 receptor. The other one is a transient pocket predicted by Molecular Dynamics simulations, which could not be observed from static analysis of CXCL12 PDB structures. The present results indicate how TEMPOL, instrumental in identifying this transient pocket, can be a powerful tool to delineate minor conformations which can be highly relevant in dynamic discovery of antitumoral drugs. PMID:24373878

Bernini, Andrea; Henrici De Angelis, Lucia; Morandi, Edoardo; Spiga, Ottavia; Santucci, Annalisa; Assfalg, Michael; Molinari, Henriette; Pillozzi, Serena; Arcangeli, Annarosa; Niccolai, Neri

2014-03-01

69

Substrate binding to DNA photolyase studied by electron paramagnetic resonance spectroscopy.  

PubMed Central

Structural changes in Escherichia coli DNA photolyase induced by binding of a (cis,syn)-cyclobutane pyrimidine dimer (CPD) are studied by continuous-wave electron paramagnetic resonance and electron-nuclear double resonance spectroscopies, using the flavin adenine dinucleotide (FAD) cofactor in its neutral radical form as a naturally occurring electron spin probe. The electron paramagnetic resonance/electron-nuclear double resonance spectral changes are consistent with a large distance (> or =0.6 nm) between the CPD lesion and the 7,8-dimethyl isoalloxazine ring of FAD, as was predicted by recent model calculations on photolyase enzyme-substrate complexes. Small shifts of the isotropic proton hyperfine coupling constants within the FAD's isoalloxazine moiety can be understood in terms of the cofactor binding site becoming more nonpolar because of the displacement of water molecules upon CPD docking to the enzyme. Molecular orbital calculations of hyperfine couplings using density functional theory, in conjunction with an isodensity polarized continuum model, are presented to rationalize these shifts in terms of the changed polarity of the medium surrounding the FAD cofactor. PMID:11463661

Weber, S; Richter, G; Schleicher, E; Bacher, A; Mobius, K; Kay, C W

2001-01-01

70

Nanoscale NMR Spectroscopy and Imaging of Multiple Nuclear Species  

E-print Network

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are well-established techniques that provide valuable information in a diverse set of disciplines but are currently limited to macroscopic sample volumes. Here we demonstrate nanoscale NMR spectroscopy and imaging under ambient conditions of samples containing multiple nuclear species, using nitrogen-vacancy (NV) colour centres in diamond as sensors. With single, shallow NV centres in a diamond chip and samples placed on the diamond surface, we perform NMR spectroscopy and one-dimensional MRI on few-nanometre-sized samples containing $^1$H and $^{19}$F nuclei. Alternatively, we employ a high-density NV layer near the surface of a diamond chip to demonstrate wide-field optical NMR spectroscopy of nanoscale samples containing $^1$H, $^{19}$F, and $^{31}$P nuclei, as well as multi-species two-dimensional optical MRI with sub-micron resolution. For all diamond samples exposed to air, we identify a ubiquitous $^1$H NMR signal, consistent with a ...

DeVience, Stephen J; Lovchinsky, Igor; Sushkov, Alexander O; Bar-Gill, Nir; Belthangady, Chinmay; Casola, Francesco; Corbett, Madeleine; Zhang, Huiliang; Lukin, Mikhail; Park, Hongkun; Yacoby, Amir; Walsworth, Ronald L

2014-01-01

71

Development of implantable detection microcoils for minimally invasive NMR spectroscopy  

Microsoft Academic Search

In this paper, we describe an implantable solenoidal microcoil of 200?m in diameter for nuclear magnetic resonance spectroscopy (NMR spectroscopy). This microcoil is used as receiving coil only during experiments. A simulation of the electromagnetic properties of this microcoil is proposed and compared to the experimental measurement. 1H spectra of 0.33cm3 sample of a deionised water or of a lipid

L. Berry; L. Renaud; P. Kleimann; P. Morin; M. Armenean; H. Saint-Jalmes

2001-01-01

72

Scalable NMR spectroscopy with semiconductor chips Dongwan Haa  

E-print Network

-Qiao Songb , and Donhee Hama,1 a School of Engineering and Applied Sciences, Harvard University, Cambridge magnets, whose high and uniform magnetic fields lead to the fine spectral resolution necessary make the benefits of NMR spectroscopy more broadly available and en- able new applications. Bulky

Ham, Donhee

73

8Li+ Knight Shift and Resonance in the Enhanced Paramagnet Platinum Studied by ?NMR  

NASA Astrophysics Data System (ADS)

We report the behavior of 8Li+ implanted into Platinum foil as revealed by ?-detected Nuclear Magnetic Resonance (?-NMR). At an applied field of 4.1 T, a single resonance is observed, which is attributed to Li in an octahedral interstitial site. The temperature dependence of the Knight shift for this resonance is monitored at temperatures ranging from 4 to 300 K. Over this range the Knight shift is found to be linearily dependent on the temperature.

Ofer, Oren; Chow, K. H.; Fan, I.; Egilmez, M.; Parolin, T. J.; Hossain, M. D.; Jung, J.; Salman, Z.; Kiefl, R. F.; Levy, C. D. P.; Morris, G. D.; Pearson, M. R.; Saadaoui, H.; Song, Q.; Wang, D.; MacFarlane, W. A.

74

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

75

Interaction of local anesthetics with lipid bilayers investigated by ¹H MAS NMR spectroscopy.  

PubMed

The membrane location of the local anesthetics (LA) lidocaine, dibucaine, tetracaine, and procaine hydrochloride as well as their influence on phospholipid bilayers were studied by ³¹P and ¹H magic-angle spinning (MAS) NMR spectroscopy. The ³¹P NMR spectra of the LA/lipid preparations confirmed that the overall bilayer structure of the membrane remained preserved. The relation between the molecular structure of the LAs and their membrane localization and orientation was investigated quantitatively using induced chemical shifts, nuclear Overhauser enhancement spectroscopy, and paramagnetic relaxation rates. All three methods revealed an average location of the aromatic rings of all LAs in the lipid-water interface of the membrane, with small differences between the individual LAs depending on their molecular properties. While lidocaine is placed in the upper chain/glycerol region of the membrane, for dibucaine and procaine the maximum of the distribution are slightly shifted into the glycerol region. Finally for tetracaine the aromatic ring is placed closest to the aqueous phase in the glycerol/headgroup region of the membrane. The hydrophobic side chains of the LA molecules dibucaine and tetracaine were located deeper in the membrane and showed an orientation towards the hydrocarbon core. In contrast the side chains of lidocaine and procaine are oriented towards the aqueous phase. PMID:22842001

Weizenmann, Nicole; Huster, Daniel; Scheidt, Holger A

2012-12-01

76

Diffusion of Paramagnetically Labeled Proteins in Cartilage: Enhancement of the 1-D NMR Imaging Technique  

NASA Astrophysics Data System (ADS)

Quantifying the diffusive transport of large molecules in avascular cartilage tissue is important both for planning potential pharamacological treatments and for gaining insight into the molecular-scale structure of cartilage. In this work, the diffusion coefficients of gadolinium-DTPA and Gd-labeled versions of four proteins—lysozyme, trypsinogen, ovalbumin, and bovine serum albumin (BSA) with molecular weights of 14,300, 24,000, 45,000, and 67,000, respectively—have been measured in healthy and degraded calf cartilage. The experimental technique relies on the effect of the paramagnetic on the relaxation properties of the surrounding water, combined with the time course of a 1-dimensional spatial profile of the water signal in the cartilage sample. The enhanced technique presented here does not require a prior measurement of the relaxivity of the paramagnetic compound in the sample of interest. The data are expressed as the ratio of the diffusion coefficient of a compound in cartilage to its diffusion coefficient in water. For healthy cartilage, this ratio was 0.34 ± 0.07 for Gd-DTPA, the smallest compound, and fell to 0.3 ± 0.1 for Gd-lysozyme, 0.08 ± 0.04 for Gd-trypsinogen, and 0.07 ± 0.04 for Gd-ovalbumin. Gd-BSA did not appear to enter healthy cartilage tissue beyond a surface layer. After the cartilage had been degraded by 24-h trypsinization, these ratios were 0.60 ± 0.03 for Gd-DTPA, 0.40 ± 0.08 for Gd-lysozyme, 0.42 ± 0.09 for Gd-trypsinogen, 0.16 ± 0.14 for Gd-ovalbumin, and 0.11 ± 0.05 for Gd-BSA. Thus, degradation of the cartilage led to increases in the diffusion coefficient of up to fivefold for the Gd-labeled proteins. These basic transport parameters yield insights on the nature of pore sizes and chemical-matrix interactions in the cartilage tissue and may prove diagnostically useful for identifying the degree and nature of damage to cartilage.

Foy, Brent D.; Blake, Joseph

2001-01-01

77

Ultrafast 2D NMR: An Emerging Tool in Analytical Spectroscopy  

NASA Astrophysics Data System (ADS)

Two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy is widely used in chemical and biochemical analyses. Multidimensional NMR is also witnessing increased use in quantitative and metabolic screening applications. Conventional 2D NMR experiments, however, are affected by inherently long acquisition durations, arising from their need to sample the frequencies involved along their indirect domains in an incremented, scan-by-scan nature. A decade ago, a so-called ultrafast (UF) approach was proposed, capable of delivering arbitrary 2D NMR spectra involving any kind of homo- or heteronuclear correlation, in a single scan. During the intervening years, the performance of this subsecond 2D NMR methodology has been greatly improved, and UF 2D NMR is rapidly becoming a powerful analytical tool experiencing an expanded scope of applications. This review summarizes the principles and main developments that have contributed to the success of this approach and focuses on applications that have been recently demonstrated in various areas of analytical chemistry—from the real-time monitoring of chemical and biochemical processes, to extensions in hyphenated techniques and in quantitative applications.

Giraudeau, Patrick; Frydman, Lucio

2014-06-01

78

A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces  

PubMed Central

A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is either surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 ?M of Mg2+ doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 ? coaxial input. Agreement between simulated and experimental results is shown. PMID:25362434

Sidabras, Jason W.; Varanasi, Shiv K.; Mett, Richard R.; Swarts, Steven G.; Swartz, Harold M.; Hyde, James S.

2014-01-01

79

A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces.  

PubMed

A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is either surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 ?M of Mg(2+) doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 ? coaxial input. Agreement between simulated and experimental results is shown. PMID:25362434

Sidabras, Jason W; Varanasi, Shiv K; Mett, Richard R; Swarts, Steven G; Swartz, Harold M; Hyde, James S

2014-10-01

80

A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces  

NASA Astrophysics Data System (ADS)

A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is either surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 ?M of Mg2+ doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 ? coaxial input. Agreement between simulated and experimental results is shown.

Sidabras, Jason W.; Varanasi, Shiv K.; Mett, Richard R.; Swarts, Steven G.; Swartz, Harold M.; Hyde, James S.

2014-10-01

81

Characterization of the Iron-Sulfur Clusters in Xanthine Dehydrogenase Using Electron Paramagnetic Resonance Spectroscopy and Magnetic Coupling Interactions  

SciTech Connect

Xanthine dehydrogenase is a metalloenzyme that is present in numerous eukaryotic and prokaryotic organisms. It contains molybdenum, two different iron-sulfur clusters, and flavin. While the structures of both iron-sulfur clusters were known, it was unclear as to which structure was in which location. Electron paramagnetic resonance spectroscopy probes the paramagnetic qualities of molecules or ions. With this technology we wished to understand which EPR spectrum was associated with which iron-sulfur cluster by looking at magnetic coupling between the paramagnetic Mo(V) oxidation state and the reduced iron-sulfur clusters. We then assigned the clusters to their corresponding locations. The spin-spin interactions observed between Mo(V) and Fe-S I in xanthine dehydrogenase at low temperature show that Fe-S I is the closer site in contrast to Fe-S II.

Scott, J. Robert

2004-02-04

82

Characterization of amorphous material in shocked quartz by NMR spectroscopy  

SciTech Connect

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

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

1993-08-01

83

Solution structure of ?-conotoxin MVIIA using 2D NMR spectroscopy  

Microsoft Academic Search

The solution structure of ?-conotoxin MVIIA (SNX-111), a peptide toxin from the fish hunting cone snail Conus magus and a high-affinity blocker of N-type calcium channels, was determined by 2D NMR spectroscopy. The backbones of the best 44 structures match with an average pairwise RMSD of 0.59 angstroms. The structures contain a short segment of triple-stranded ?-sheet involving residues 6–8,

Vladimir J. Basus; Laszlo Nadasdi; J. Ramachandran; George P. Miljanich

1995-01-01

84

From metabolic to metabolomic NMR spectroscopy of apoptotic cells  

Microsoft Academic Search

Over the past 10–15 years, nuclear magnetic resonance (NMR) spectroscopy has been employed to study metabolic events accompanying\\u000a programmed cell death (apoptosis). The early studies were characterized by experiments focusing on specific metabolic parameters\\u000a obtained by analyzing a limited number of biochemical compounds, e.g. selected metabolic species involved in the Krebs cycle,\\u000a in energy metabolism, in phospholipid synthesis and degradation, or

Norbert W. Lutz

2005-01-01

85

Relaxation-Assisted Separation of Chemical Sites in NMR Spectroscopy of Static Solids  

E-print Network

. The principles and limitations of the 2D NMR approach resulting from these considerations are discussedRelaxation-Assisted Separation of Chemical Sites in NMR Spectroscopy of Static Solids Adonis sites in the NMR spectroscopy of powdered or disordered samples. This proposal is motivated

Frydman, Lucio

86

Quadrupolar and Chemical Shift Tensors Characterized by 2D Multiple-Quantum NMR Spectroscopy  

E-print Network

Quadrupolar and Chemical Shift Tensors Characterized by 2D Multiple-Quantum NMR Spectroscopy Ales The present work discusses a new 2D NMR method for char- acterizing the principal values and relative; multiple-quantum spectroscopy; 2D NMR correlations. 1. INTRODUCTION Quadrupolar nuclei with half

Frydman, Lucio

87

SYLLABUS for CH 841 and CH 841L Chemical Applications of NMR Spectroscopy  

E-print Network

. The second dimension (2D NMR): Quantum- mechanical approach; coherence transfer; phase cycling and coherenceSYLLABUS for CH 841 and CH 841L Fall 2009 Chemical Applications of NMR Spectroscopy Catalog Description: Basic concepts of NMR spectroscopy with application to organic, inorganic, physical

Stuart, Steven J.

88

Binding of manganese(II) to a tertiary stabilized hammerhead ribozyme as studied by electron paramagnetic resonance spectroscopy  

Microsoft Academic Search

Electron paramagnetic resonance (EPR) spectroscopy is used to study the binding of MnII ions to a tertiary stabilized hammer- head ribozyme (tsHHRz) and to compare it with the binding to the minimal hammerhead ribozyme (mHHRz). Continuous wave EPR measurements show that the tsHHRz possesses a single high-affinity MnII binding site with a KD of ?10 nM at an NaCl concentration

NATALIA KISSELEVA; ANASTASIA KHVOROVA; ERIC WESTHOF; OLAV SCHIEMANN

2005-01-01

89

Characterization of gamma-ray induced paramagnetic centers in bayerite by means of EPR and ENDOR spectroscopies  

Microsoft Academic Search

Four different paramagnetic centers, induced in bayerite samples by irradiation, have been characterized by EPR and ENDOR spectroscopies. Two of them, respectively, of V- and F-types, have been found to be mobile at room temperature and frozen at lower temperature. The first one, with g1= 2.021+\\/-0.002, g2=2.010+\\/-0.005, and g3=2.005+\\/-0.002, is identified with an O- species stemming from the ionization of

Eric G. Derouane; Jacques C. Vedrine

1976-01-01

90

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.

91

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

92

Characterization of iron, manganese, and copper synthetic hydroxyapatites by electron paramagnetic resonance spectroscopy.  

PubMed

The incorporation of micronutrients (e.g., Fe, Mn, Cu) into synthetic hydroxyapatite (SHA) is proposed for slow release of these nutrients to crops in NASA's Advanced Life Support (ALS) program for long-duration space missions. Separate Fe3+ (Fe-SHA), Mn2+ (Mn-SHA), and Cu2+ (Cu-SHA) containing SHA materials were synthesized by a precipitation method. Electron paramagnetic resonance (EPR) spectroscopy was used to determine the location of Fe3+, Mn2+, and Cu2+ ions in the SHA structure and to identify other Fe(3+)-, Mn(2+)-, and Cu(2+)-containing phases that formed during precipitation. The EPR parameters for Fe3+ (g=4.20 and 8.93) and for Mn2+ (g=2.01, A=9.4 mT, D=39.0 mT and E=10.5 mT) indicated that Fe3+ and Mn2+ possessed rhombic ion crystal fields within the SHA structure. The Cu2+ EPR parameters (g(z)=2.488, A(z)=5.2 mT) indicated that Cu2+ was coordinated to more than six oxygens. The rhombic environments of Fe3+ and Mn2+ along with the unique Cu2+ environment suggested that these metals substituted for the 7 or 9 coordinate Ca2+ in SHA. The EPR analyses also detected poorly crystalline metal oxyhydroxides or metal-phosphates associated with SHA. The Fe-, Mn-, and Cu-SHA materials are potential slow release sources of Fe, Mn, and Cu for ALS and terrestrial cropping systems. PMID:12817564

Sutter, B; Wasowicz, T; Howard, T; Hossner, L R; Ming, D W

2002-01-01

93

Quantum-chemical analysis of paramagnetic 13C NMR shifts of iron-bound cyanide ions in heme-protein environments  

NASA Astrophysics Data System (ADS)

Paramagnetic 13C NMR chemical shifts of iron-bound cyanide ions located in biological environments such as heme-proteins are significantly sensitive to the environments. These chemical shifts are due to negative spin density at 13C induced by the open-shell iron center. In order to examine the environments effects on the electronic states around heme parts, ab initio calculations were performed for model systems of heme-proteins. The proximal residues in proteinparts of cytochrome c, hemoglobin, myoglobin and horseradish peroxidase were included in the model systems with the common active site (cyanide imidazole porphyrinato iron(III)) to take account of the environments effects. The calculated paramagnetic shifts of model systems reproduce the experimental trend of corresponding heme-proteins. It is found that the effects of proximal residues on the electronic states of the heme-parts are significant for these hemeproteins. In this abstract we focused on the calculations and analysis of cytochrome c.

Yamaki, Daisuke; Hada, Masahiko

2012-12-01

94

4f-4f hypersensitivity in the absorption spectra and NMR studies on paramagnetic lanthanide chloride complexes with 1,10-phenanthroline in non-aqueous solutions.  

PubMed

The optical absorption and NMR studies of trivalent lanthanide chloride complexes with 1,10-phenanthroline (phen) are presented and discussed. The 1H NMR spectra of the complexes of La, Pr, Nd, Eu and Yb have been studied in methanol-d(4). The resonances of phen in the NMR spectra of the paramagnetic complexes have been shifted to lower as well as higher fields, which is a manifestation of dipolar interaction. The H (2) protons of the heterocyclic amine display broad resonances. The degree of broadening in Pr, Nd, and Yb complexes follows the order Pr < Nd < Yb. The inter- and intra-molecular shift ratios show that the paramagnetic shift is predominantly due to dipolar interaction. The electronic spectra of Pr, Nd, Ho and Er complexes have been investigated in methanol, pyridine, DMSO and DMF, which reveal that the hypersensitive transitions exhibit larger variation in oscillator strength values and band shapes. The change in the coordination geometry of the complexes and relative basicity of ligand are found responsible for oscillator strength and band shape variation. The interelectronic repulsion and covalency parameters show covalent nature of bonding between the metal and the ligand. PMID:12633723

Hussain, H A; Iftikhar, K

2003-03-15

95

Measurement of free radicals using electron paramagnetic resonance spectroscopy during open aorto-iliac arterial reconstruction.  

PubMed

Background Aortic cross-clamping during abdominal aortic aneurysm (AAA) open repair leads to development of ischemia-reperfusion injury. Electron paramagnetic resonance spectroscopy (EPR) spin-trapping is a valuable method of direct measurement of free radicals. The objective of the study was to evaluate the results of EPR as a direct method of free radical measurement and degree of inflammatory response in open operative treatment of patients with AAA and aorto-iliac occlusive disease (AIOD). Material and Methods The study was performed on a group of 32 patients with AAA and 25 patients with AIOD scheduled for open repair. Peripheral venous blood for EPR spectroscopy and for SOD, GPx, ox-LDL, Il-6, TNF-alfa, CRP, and HO-1 were harvested. Selected parameters were established accordingly to specified EPR and immunohistochemical methods and analyzed between groups by Mann-Whitney U test and Wilcoxon matched-pairs signed-ranks test with Bonferroni correction. Results Free radicals level was correlated with the time of the aortic cross-clamping after the reperfusion of he first and second leg in AAA (r=0.7; r=0.47). ox-LDL in AAA decreased 5 min after reperfusion of the first leg (32.99 U/L, range: 14.09-77.12) and 5 min after reperfusion of the second leg (26.75 U/L, range: 11.56-82.12) and 24 h after the operation (25.85 U/L, range: 14.29-49.70). HO-1concentration increased to above the level before intervention 24 h after surgery. The activities of GPx and SOD decreased 5 min after the first-leg reperfusion in AAA. Twenty-four hours after surgery, inflammatory markers increased in AAA to CRP was 14.76 ml/l (0.23-38.55), IL-6 was 141.22 pg/ml (84.3-591.03), TNF-alfa was 6.82 pg/ml (1.76-80.01) and AIOD: CRP was 18.44 mg/l (2.56-33.14), IL-6: 184.1 pg/ml (128.46-448.03), TNF-alfa was 7.74 pg/ml (1.74-74.74). Conclusions EPR spin-trapping demonstrates temporarily elevated level of free radicals in early phase of reperfusion, leading to decrease antioxidants in AAA. Elevated free radical levels decreased 24 h after surgery due to various endogenous antioxidants and therapies. PMID:25429420

Majewski, Wac?aw; Krzyminiewski, Ryszard; Stanisi?, Micha?; Iskra, Maria; Krasi?ski, Zbigniew; Nowak, Marek; Dobosz, Bernadeta

2014-01-01

96

Ultrafast 2D NMR Spectroscopy Using Sinusoidal Gradients: Principles and Ex Vivo Brain Investigations  

E-print Network

Ultrafast 2D NMR Spectroscopy Using Sinusoidal Gradients: Principles and Ex Vivo Brain ultrafast acquisitions of 2D NMR spectra with suitable spectral widths on a microimaging probe (for both Wiley-Liss, Inc. Key words: ultrafast 2D NMR; magnetic resonance spectros- copy; brain metabolites; 2D

Frydman, Lucio

97

Single-scan 2D NMR spectroscopy on a 25 T bitter magnet Boaz Shapira a  

E-print Network

Single-scan 2D NMR spectroscopy on a 25 T bitter magnet Boaz Shapira a , Kiran Shetty b , William W Abstract 2D NMR relies on monitoring systematic changes in the phases incurred by spin coherences for 2D NMR acquisitions. It is here shown with a series of homo- and hetero-nuclear examples

Frydman, Lucio

98

Relaxation-Optimized NMR Spectroscopy of Methylene Groups in Proteins and Nucleic Acids  

E-print Network

can be incorporated in many of today's most common 2D and 3D NMR experiments. As an example, we showRelaxation-Optimized NMR Spectroscopy of Methylene Groups in Proteins and Nucleic Acids Emeric acids is of the methylene type. Their detailed study, however, in terms of structure and dynamics by NMR

Clore, G. Marius

99

Real-Time Monitoring of Chemical Transformations by Ultrafast 2D NMR Spectroscopy  

E-print Network

Real-Time Monitoring of Chemical Transformations by Ultrafast 2D NMR Spectroscopy Maayan Gal, Mor: An approach enabling the acquisition of 2D nuclear magnetic resonance (NMR) spectra within a single scan has of these measurements involved acquiring a train of 2D 1 H-15 N HSQC NMR spectra separated by ca. 4 s; following

Frydman, Lucio

100

Ultrafast 2D NMR spectroscopy using a continuous spatial encoding of the spin interactions  

Microsoft Academic Search

A new protocol for acquiring multidimensional NMR spectra within a single scan is introduced and illustrated. The approach relies on applying a pair of frequency-chirped excitation and storage pulses in combination with echoing magnetic field gradients, in order to impart the kind of linear spatial encoding of the NMR interactions that is required by ultrafast 2D NMR spectroscopy. It is

Yoav Shrot; Boaz Shapira; Lucio Frydman

2004-01-01

101

Symmetric spatial encoding in ultrafast 2D NMR spectroscopy Boaz Shapira, Yoav Shrot, Lucio Frydman *  

E-print Network

Symmetric spatial encoding in ultrafast 2D NMR spectroscopy Boaz Shapira, Yoav Shrot, Lucio Frydman with a series of amplitude-modulated homo- and hetero-nuclear 2D ultrafast NMR examples. Ã? 2005 Elsevier Inc. All rights reserved. Keywords: Ultrafast 2D NMR; Spatial encoding; Double-frequency-sweep irradiation

Frydman, Lucio

102

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

103

Studying the Structure and Dynamics of Biomolecules by Using Soluble Paramagnetic Probes  

PubMed Central

Characterisation of the structure and dynamics of large biomolecules and biomolecular complexes by NMR spectroscopy is hampered by increasing overlap and severe broadening of NMR signals. As a consequence, the number of available NMR spectroscopy data is often sparse and new approaches to provide complementary NMR spectroscopy data are needed. Paramagnetic relaxation enhancements (PREs) obtained from inert and soluble paramagnetic probes (solvent PREs) provide detailed quantitative information about the solvent accessibility of NMR-active nuclei. Solvent PREs can be easily measured without modification of the biomolecule; are sensitive to molecular structure and dynamics; and are therefore becoming increasingly powerful for the study of biomolecules, such as proteins, nucleic acids, ligands and their complexes in solution. In this Minireview, we give an overview of the available solvent PRE probes and discuss their applications for structural and dynamic characterisation of biomolecules and biomolecular complexes. PMID:23836693

Hocking, Henry G; Zangger, Klaus; Madl, Tobias

2013-01-01

104

Peak width issues with generalised 2D correlation NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Two-dimensional spectral correlation analysis is shown to be sensitive to fluctuations in spectral peak width as a function of perturbation variable. This is particularly significant where peak width fluctuations are of similar order of magnitude as the peak width values themselves and where changes in peak width are not random but are, for example, proportional to intensity. In such cases these trends appear in the asynchronous matrix as false peaks that serve to interfere with interpretation of the data. Complex, narrow band spectra such as provided by 1H NMR spectroscopy are demonstrated to be prone to such interference. 2D correlation analysis was applied to a series of NMR spectra corresponding to a commercial wine fermentation, in which the samples collected over a period of several days exhibit dramatic changes in concentration of minor and major components. The interference due to changing peak width effects is eliminated by synthesizing the recorded spectra using a constant peak width value prior to performing 2D correlation analysis.

Kirwan, Gemma M.; Adams, Michael J.

2008-12-01

105

Structure of outer membrane protein G by solution NMR spectroscopy  

PubMed Central

The bacterial outer membrane protein G (OmpG), a monomeric pH-gated porin, was overexpressed in Escherichia coli and refolded in ?-octyl glucoside micelles. After transfer into dodecylphosphocholine micelles, the solution structure of OmpG was determined by solution NMR spectroscopy at pH 6.3. Complete backbone assignments were obtained for 234 of 280 residues based on CA, CB, and CO connection pathways determined from a series of TROSY-based 3D experiments at 800 MHz. The global fold of the 14-stranded ?-barrel was determined based on 133 long-range NOEs observed between neighboring strands and local chemical shift and NOE information. The structure of the barrel is very similar to previous crystal structures, but the loops of the solution structure are quite flexible. PMID:17911261

Liang, Binyong; Tamm, Lukas K.

2007-01-01

106

Optical and electron paramagnetic resonance spectroscopies of diffusion-doped Co2+:ZnSe  

NASA Astrophysics Data System (ADS)

The efficacy of diffusing cobalt into window-grade polycrystalline ZnSe during high-temperature anneals has been studied. Absorption, photoluminescence (PL), time-resolved PL, and electron paramagnetic resonance (EPR) were used to characterize samples with cobalt concentrations ranging from 1017 to 1019 cm-3. Absorption and PL were used to monitor the optical properties of Co2+ impurities, as well as detect Ni2+ and Fe2+ ions due to unintentional contamination. The temperature dependence of the 3 ?m emission due to Co2+ ions was measured and lifetimes were determined. EPR was used to monitor the paramagnetic charge states (Co2+, Ni3+, and Fe3+) of the transition-metal ions in our samples. The effects of nickel and iron impurities on the Co2+ infrared emission intensity and lifetime are discussed.

Luo, Ming; Garces, N. Y.; Giles, N. C.; Roy, Utpal N.; Cui, Yunlong; Burger, Arnold

2006-04-01

107

Virgin olive oil: Free radical production studied with spin-trapping electron paramagnetic resonance spectroscopy  

Microsoft Academic Search

Spin trapping using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) has been used to detect and distinguish free radicals in samples of Greek extra virgin olive oils. A number\\u000a of the samples examined immediately after the addition of the spin trap showed a spontaneous complex electron paramagnetic\\u000a resonance (EPR) signal. The majority of DMPO-radical adducts formed (80–90%) represented peroxyl and alkoxyl radical adducts.\\u000a Similar

D. Skoutas; D. Haralabopoulos; S. Avramiotis; T. G. Sotiroudis; A. Xenakis

2001-01-01

108

Structural investigations on betacyanin pigments by LC NMR and 2D NMR spectroscopy  

Microsoft Academic Search

Four betacyanin pigments were analysed by LC NMR and subjected to extensive NMR characterisation after isolation. Previously, low pH values were applied for NMR investigations of betalains resulting in rapid degradation of the purified substances thus preventing extensive NMR studies. Consequently, up to now only one single 13C NMR spectrum of a betalain pigment, namely that of neobetanin (=14,15-dehydrobetanin), was

Florian C Stintzing; Jürgen Conrad; Iris Klaiber; Uwe Beifuss; Reinhold Carle

2004-01-01

109

Structural Characterization of Proteins with an Attached ATCUN Motif by Paramagnetic Relaxation Enhancement NMR Spectroscopy  

E-print Network

,1e and a number of protocols have been developed to incorporate the information derived from the use.-L.; Donaire, A.; Zhou, Z. H.; Adams, M. W. W.; La Mar, G. N. Biochemistry 1996, 35, 11319-11328. (b) Gillespie

Skrynnikov, Nikolai

110

Detection of a tetranuclear iron-sulfur center in fumarate reductase from Escherichia coli by electron paramagnetic resonance spectroscopy.  

PubMed

Soluble fumarate reductase and fumarate reductase complex from Escherichia coli have been investigated by electron paramagnetic resonance spectroscopy. Both succinate- and dithionite-reduced samples show signals associated with a [2Fe-2S]1+ cluster that account maximally for slightly more than one spin/molecule. In addition, at temperatures below 20 K, dithionite-reduced samples exhibit broad and complex features, to high and low field of the [2Fe-2S]1+ signal, that are attributable to a spin coupled [4Fe-4S]1+ cluster. Preliminary attempts to quantify the signals indicate that the [4Fe-4S] cluster is present in an approximate 1:1 stoichiometry with the [2Fe-2S] cluster. The observed enhancement of the spin relaxation of the [2Fe-2S]1+ cluster on dithionite reduction is attributed to spin-spin interaction between the S = 1/2, reduced tetranuclear and binuclear clusters. PMID:2996525

Johnson, M K; Morningstar, J E; Cecchini, G; Ackrell, B A

1985-09-16

111

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

112

Direct detection of discharge products in lithium-oxygen batteries by solid-state NMR spectroscopy.  

PubMed

A closer look: Solid-state (7) Li and (17) O NMR spectroscopy is a valuable tool in the characterization of products formed in the lithium-oxygen battery, a necessary step in the development of a viable cell. Since lithium peroxide, the desired discharge product, has a unique (17) O NMR signature, it can be clearly identified. PMID:22786802

Leskes, Michal; Drewett, Nicholas E; Hardwick, Laurence J; Bruce, Peter G; Goward, Gillian R; Grey, Clare P

2012-08-20

113

Mobility and Diffusion-Ordered Two-Dimensional NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

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 to provide unidirectional flow for ions of interest. Techniques based upon the reverse precession method were also implemented to recover the signs of the mobilities and improved resolution in the mobility dimension was obtained by replacing Fourier transformation of truncated data sets with a linear prediction analysis. In the diffusion-ordered two-dimensional NMR experiments, the conventional chemical shift spectrum is resolved in one dimension and spectra of diffusion rates or molecular radii are resolved in the other. Diffusion dependent pulsed field gradient NMR data sets were inverted by means of the computer programs SPLMOD or DISCRETE, when discrete diffusion coefficients were present, and CONTIN when continuous distributions were present. Since the inversion is ill -conditioned, it was necessary to introduce additional information to limit the range of the solutions. In addition to prior knowledge of the decay kernels and non-negativity of amplitudes and damping constants, a set of rejection criteria was constructed for the discrete analysis case that took into account physical limits on diffusion coefficients, experimentally accessible values, and variations in effective decay kernels resulting from instrumental non-linearities. Examples of analyses of simulated data and experimental data for mixtures are presented as well as two-dimensional spectra generated by CONTIN for polydisperse polymer samples. Also, resolution in the diffusion dimension was increased by performing experiments on hydrophobic molecules in the presence of surfactant micelles. Finally, the diffusion-ordered experiment was used to study the polymer induced breakdown of micelles consisting of cetyltrimethylammonium bromide and sodium salicylate. Addition of the polymer poly(vinyl methyl ether) resulted in an increase in the micelle diffusion coefficient and at high polymer concentrations and elevated temperatures the polymer and micelle were observed to diffuse at the same rate.

Morris, Kevin Freeman

114

Recent advances in protein NMR spectroscopy and their implications in protein therapeutics research.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography are the two main methods for protein three-dimensional structure determination at atomic resolution. According to the protein structures deposited in the Protein Data Bank, X-ray crystallography has become the dominant method for structure determination, particularly for large proteins and complexes. However, with the developments of isotope labeling, increase of magnetic field strength, common use of a cryogenic probe, and ingenious pulse sequence design, the applications of NMR spectroscopy have expanded in biological research, especially in characterizing protein dynamics, sparsely populated transient structures, weak protein interactions, and proteins in living cells at atomic resolution, which is difficult if not impossible by other biophysical methods. Although great advances have been made in protein NMR spectroscopy, its applications in protein therapeutics, which represents the fastest growing segment of the pharmaceutical industry, are still limited. Here we review the recent advances in the use of NMR spectroscopy in studies of large proteins or complexes, posttranslation modifications, weak interactions, and aggregation, and in-cell NMR spectroscopy. The potential applications of NMR spectroscopy in protein therapeutic assays are discussed. PMID:24309626

Wang, Guifang; Zhang, Ze-Ting; Jiang, Bin; Zhang, Xu; Li, Conggang; Liu, Maili

2014-04-01

115

Phosphorus speciation in a eutrophic lake by ³¹P 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

116

On the use of 2D correlation and exchange NMR spectroscopy in organic porous materials.  

PubMed

Two-dimensional (2D) nuclear magnetic resonance (NMR) methods for the investigation of correlation and exchange have been introduced in recent years and have been applied to a range of different systems. Here, we report on the use of 2D NMR diffusion-diffusion correlation spectroscopy for the investigation of diffusion anisotropy in cellular plant tissues and of diffusion-diffusion exchange spectroscopy for the study of the diffusive exchange of dextran in a dispersion of polyelectrolyte multilayer hollow capsules. Furthermore, diffusion-relaxation correlation spectroscopy was applied to both systems. PMID:17466772

Galvosas, Petrik; Qiao, Ying; Schönhoff, Monika; Callaghan, Paul T

2007-05-01

117

Identifying the Constituents of and Transformations in Diatomaceous Earth and Polysiloxane Foams Through the Use of Electron Paramagnetic Resonance Spectroscopy  

NASA Astrophysics Data System (ADS)

The chemical aging of polymeric materials is largely governed by the characteristics of the storage environment. For polysiloxane foams, the diatomaceous earth (DE) filler is a small component of the foam, but it plays a large role in the handling of water in the system. The DE filler can act as either a ``source'' or a ``sink'' for water via both chemical hydroxylation/ dehydroxylation and physical adsorption/ desorption processes, depending on the processing history and storage conditions. We have used electron paramagnetic resonance (EPR) spectroscopy to examine composite foam material as well as the DE filler alone. Intense, broad (400 Gauss) resonances were recorded at room temperature as a function of the microwave power at X-band frequency. The observed spectra have been assigned to the iron oxide compounds goethite, lepidocrocite, hematite, and magnetite based upon the measured EPR spectra of these minerals. As the presence or absence of free H2O and the temperature of processing and storage also affects the interconversion of these various iron oxides, we indicate how this process can be followed by monitoring changes in the EPR spectra.

Blair, Michael; Muenchausen, Ross; Bennett, Bryan; Smith, James; Stephens, Thomas; Cooke, Wayne

2007-03-01

118

Aluminum binding to phosphatidylcholine lipid bilayer membranes: aluminum exchange lifetimes from 31P NMR spectroscopy  

Microsoft Academic Search

Two-dimensional (2D) 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) exchange spectroscopy (EXSY) demonstrated that aluminum binds to the phosphate group of phosphatidylcholine (PC) in multilamellar vesicles at pH 3.2, forming preferentially 2\\/1, in addition to 1\\/1 (PC\\/Al) complexes in slow exchange with one another, and with free PC, on the NMR timescale. Exchange rate constants between these three

Neil MacKinnon; Jay Ridgway; Kevin J. Crowell; Peter M. Macdonald

2006-01-01

119

2D multiquantum MAS-NMR spectroscopy of 27Al in aluminophosphate molecular sieves  

Microsoft Academic Search

Two-dimensional multiquantum MAS-NMR spectroscopy (2D-MQ) has been applied to the discrimination of the different 27Al sites in several aluminophosphate molecular sieves. It is shown that a new quintuple-quantum MAS-NMR method (2D-5Q) gives an extraordinary improved resolution compared to the DOR or DAS technique. The pure-absorption 2D spectra allow the direct determination of the number of different species, the correct determination

C. Fernandez; J. P. Amoureux

1995-01-01

120

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

121

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

SciTech Connect

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

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

1997-01-01

122

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

123

Interaction of phenol with NaX zeolite as studied by 1H MAS NMR, 29Si MAS NMR and 29Si CP MAS NMR spectroscopy  

Microsoft Academic Search

The interaction of phenol with zeolite NaX has been studied by 1H and 29Si MAS and 29Si-CP-MAS NMR spectroscopy. A large displacement of the chemical shift of hydroxyl protons from 1.2 ppm in the crystalline state to about 9 ppm occurs upon H-bonding of phenol to basic oxygen atoms of the zeolite. An enhancement of the 29Si-CP-MAS signal is observed

T Beutel; M.-J Peltre; B. L Su

2001-01-01

124

Quantitative determination of cephalexin in cephradine by NMR spectroscopy.  

PubMed

An NMR method to determine quantitatively the presence of cephalexin in cephradine was developed. The method is applicable to the chemical itself as well as to capsules and oral suspension formulations. The determination is based on the NMR signal arising from the five aromatic protons of the cephalexin molecule. Integration of this signal relative to a signal from cephradine provides the data necessary to determine the percentage of cephalexin present. The precision at the 2% cephalexin levels is +/- 0.18%. The time required to carry out a single analysis is about 10 min, and five analyses can be done in about 0.5 hr. PMID:702311

Warren, R J; Zarembo, J E; Staiger, D B; Post, A

1978-10-01

125

The use of election paramagnetic resonance spectroscopy in early preformulation experiments: the impact of different experimental formulations on the release of a lipophilic spin probe into gastric juice  

Microsoft Academic Search

The lipophilic spin probe TEMPOL-benzoate was dissolved in different experimental formulations, including polyethylene glycol 400 (PEG 400), Miglyol, glycerol monooleate (GMO), and Cremophor RH-40. Samples were measured by electron paramagnetic resonance (EPR) spectroscopy before and after addition to human gastric juice. The distance between the first and the third peak in the EPR spectrum (2aN) was measured to monitor the

Beate Bittner; Hugues Isel; Richard J. Mountfield

2001-01-01

126

Scavenger Capacity of Follicular Fluid, Decidua and Culture Medium with Regard to Assisted Reproduction: An in vitro Study Using Electron Paramagnetic Resonance Spectroscopy  

Microsoft Academic Search

The natural scavenger capacity of follicular fluid of women pre-treated for in vitro fertilization (IVF) embryo transfer, Ham’s F10 nutrient mixture used for oocyte culture and endometrium samples were studied in a hydroxyl free radical generating system, using electron paramagnetic resonance (EPR) spectroscopy. The EPR signals appearing after the addition of samples to the reaction mixture show a diversely decreasing

Attila Török; József Belágyi; Béla Török; Hans-Rudolf Tinneberg; József Bódis

2003-01-01

127

Metabolic differentiations of Pueraria lobata and Pueraria thomsonii using ¹H NMR spectroscopy and multivariate statistical analysis.  

PubMed

Puerariae Radix was a widely used herbal medicine. Pueraria lobata (PL) and Pueraria thomsonii (PT) were the two authorized sources of Puerariae Radix (gegen) in China. In this study, metabolic differentiations between these two species were investigated using NMR spectroscopy followed by principal components analysis (PCA) and partial least squares-discriminant analysis (PLS-DA). The content of puerarin in PL and PT was also determined using quantitative (1)H NMR spectroscopy. Thirteen isoflavones were tentatively identified based on 1D and 2D NMR spectroscopic data in two species. The (1)H NMR spectra of PL and PT were obviously different. PL and PT could also be markedly discriminated from (1)H NMR spectroscopic data by PCA and PLS-DA. For the crude drug resources, isoflavones, in which puerarin is the most important one, were regarded as the reasonable markers for the discrimination of the two species. The contents of puerarin and total isoflavones in PL were quantitated much higher than those in PT. Above all, (1)H NMR spectroscopy, which can provide comprehensive profiles of the metabolites and achieve convenient determinations of puerarin and total isoflavones in a single run, is an efficient means for evaluating the medicinal samples and achieving a better quality control of Puerariae Radix. PMID:23746990

Chen, Yan-Gan; Song, Yue-Lin; Wang, Ying; Yuan, Yun-Fei; Huang, Xiao-Jun; Ye, Wen-Cai; Wang, Yi-Tao; Zhang, Qing-Wen

2014-05-01

128

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. PMID:24109452

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

2013-01-01

129

Structural determination of larger proteins using stable isotope labeling and NMR spectroscopy  

SciTech Connect

The project sought to employ stable isotope labeling and NMR spectroscopy to study protein structures and provide insight into important biochemical problems. A methylotrophic bacterial expression system has been developed for uniform deuterium and carbon-13 labeling of proteins for structural studies. These organisms grow using methanol as the sole source of carbon and energy. Because isotopically labeled methanol is relatively inexpensive, the methylotrophs are ideal for expressing proteins labeled uniformly with deuterium and/or carbon-13. This expression system has been employed to prepare deuterated troponin C. NMR spectroscopy measurements have been made on the inhibitory peptide from troponin I (residues 96--115), both as the free peptide and the peptide complexed with deuterated troponin C. Proton-NMR spectroscopy resonance-signal assignments have been made for the free peptide.

Unkefer, C.; Hernandez, G.; Springer, P.; Trewhella, J. [Los Alamos National Lab., NM (United States); Blumenthal, D. [Univ. of Utah, Salt Lake City, UT (United States); Lidstrom, M. [California Inst. of Tech., Pasadena, CA (United States)

1996-04-01

130

Polydimethylsiloxane: a general matrix for high-performance chromatographic NMR spectroscopy.  

PubMed

The detection and structural characterization of the components of a mixture is a challenging task. Therefore, the development of a facile and general method that enables both the separation and the structural characterization of the components is desired. Diffusion-ordered NMR spectroscopy (DOSY) with the aid of a matrix is a promising tool for this purpose. However, because the currently existing matrices only separate limited components, the application of the DOSY technique is restricted. Herein we introduce a new versatile matrix, poly(dimethylsiloxane), which can fully separate many mixtures of different structural types by liquid-state NMR spectroscopy. With poly(dimethylsiloxane), liquid-state chromatographic NMR spectroscopy could become a general approach for the structural elucidation of mixtures of compounds. PMID:25196825

Huang, Shaohua; Gao, Jun; Wu, Rui; Li, Shengying; Bai, Zhengwu

2014-10-20

131

A study of petroleum alkylcarbazoles using 1H NMR spectroscopy  

Microsoft Academic Search

A precision method for measuring proton chemical shift calculations of methylcarbazoles has been developed. For other abundant substituents the proton chemical shift correlation diagrams are reported. The method makes it possible to identify a number of carbazole structures present in petroleums. General structural regularities of petroleum carbazoles have been defined from 1H NMR data. Methylcarbazole isomers with 1- and 1,8-substituents

M. B. Smirnov; E. B. Frolov

1997-01-01

132

NMR spectroscopy and perfusion of mammalian cells using surface microprobes.  

PubMed

NMR spectra of mammalian cells are taken using surface microprobes that are based on microfabricated planar coils. The surface microprobe resembles a miniaturized Petri dish commonly used in biological research. The diameter of the planar coils is 1 mm. Chinese Hamster Ovaries are immobilized in a uniform layer on the microprobe surface or patterned by an ink-jet printer in the centre of the microcoil, where the rf-field of the planar microcoil is most uniform. The acquired NMR spectra show the prevalent metabolites found in mammalian cells. The volumes of the detected samples range from 25 nL to 1 nL (or 50,000 to 1800 cells). With an extended set-up that provides fluid inlets and outlets to the microprobe, the cells can be perfused within the NMR-magnet while constantly taking NMR spectra. Perfusion of the cells opens the way to increased cell viability for long acquisitions or to analysis of the cells' response to environmental change. PMID:17330170

Ehrmann, Klaus; Pataky, Kristopher; Stettler, Matthieu; Wurm, Florian Maria; Brugger, Jürgen; Besse, Pierre-André; Popovic, Radivoje

2007-03-01

133

Solid-state NMR spectroscopy of Pb-rich apatite.  

PubMed

Pb-containing hydroxylapatite phases synthesized under aqueous conditions were investigated by X-ray diffraction and solid-state nuclear magnetic resonance (NMR) techniques to determine the Pb, Ca distribution. 31P and 1H magic-angle spinning (MAS) NMR results indicate slight shifts of the isotropic chemical shift with increased Ca content and complex lineshapes at compositions with near equal amounts of Ca and Pb. 31P{207Pb} and 1H{207Pb} rotational-echo double resonance (REDOR) results for intermediate compositions show that resolved spectral features cannot be assigned simply in terms of local Ca, Pb configurations or coexisting phases. 207Pb MAS NMR spectra are easily obtained for these materials and contain well-resolved resonances for crystallographically unique A1 and A2 Pb sites. Splitting of the A1 and A2 207Pb resonances for pure hydroxyl-pyromorphite (Pb10(PO4)6(OH)2) compared to natural pyromorphite (Pb5(PO4)3Cl) suggests symmetry reduced from hexagonal. We find that 207Pb{1H} CP/MAS NMR is impractical in Pb-rich hydroxylapatites due to fast 207Pb relaxation. PMID:19821466

Mason, Harris E; Hirner, Joshua J; Xu, Wenqian; Parise, John B; Phillips, Brian L

2009-12-01

134

High Resolution 3D Exchange NMR Spectroscopy and the Mapping of Connectivities between Half-integer Quadrupolar Nuclei  

E-print Network

in the present study but are resolved by MQMAS.8b,c Conventional 2D exchange MAS NMR experiments exhibit exHigh Resolution 3D Exchange NMR Spectroscopy and the Mapping of Connectivities between Half June 8, 2002 The nuclear magnetic resonance (NMR) of spin S > 1/2 nuclei is usually dominated

Frydman, Lucio

135

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

136

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

137

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

138

The Structure of Water in Crystalline Aluminophosphates: Isolated Water and Intermolecular Clusters Probed by Raman Spectroscopy, NMR and Structural Modeling  

E-print Network

Probed by Raman Spectroscopy, NMR and Structural Modeling Peter-Paul Knops-Gerrits,*,, Helge Toufar 14, 1999 Raman spectroscopy, thermo-gravimetry and NMR together with EEM-Monte Carlo calculations is less confined. The Raman vibrations of water in different aluminum phosphates reflects the polarization

Goddard III, William A.

139

Solid-State NMR Investigation of Paramagnetic Nylon-6 Clay Nanocomposites. 1. Crystallinity, Morphology, and the Direct Influence of Fe3+ on Nuclear Spins  

NSDL National Science Digital Library

Several exfoliated nylon-6/clay nanocomposites (NnCâs) were investigated and compared with pure nylon-6 using solid-state NMR, both proton and 13C. NnCâs had nominally 5 mass % clay and were generated both by blending and by in situ polymerization (IsP). Most of the studied NnCâs contained layered, naturally occurring montmorillonite clays having nonstoichiometric amounts of nonexchangeable Mg2+ and Fe3+ ions that substitute into octahedral Al3+ sites along the midplane of the 1-nm-thick clay layers. The Fe3+ ions impart a useful paramagnetism to the clay. Each Mg2+ ion leaves an embedded negative charge that must be neutralized with some cation at the surface of the clay. All clays were initially treated with a cationic so-called organic modifier (OM), often a substituted ammonium ion, which increases the clay layer spacing, attaching ionically to the surface of the clay layers. Clay is found to promote growth of the ç-crystalline phase of nylon-6 for both blended and IsP NnCâs; R-crystallites are characteristic of the pure nylon-6. Stability of the ç-phase to annealing at 214 °C was investigated. Conversion of ç- to R-crystallinity during annealing was minimal, except for an injection-molded IsP NnC, which had been exposed to a temperature of 295 °C during molding. This high processing temperature produced an irreversible change. An attempt was made to understand, at least qualitatively, the nature of the spectral density of magnetic fluctuations associated with the paramagnetic Fe3+ sites in the clay. For this purpose, we looked directly at the influence of Fe3+ on the 13C and proton observables in organically modified clays (OMC). We agree with other investigators that the spectral density of paramagnetic fluctuations at the surface of the clay is determined mainly by spin-exchange interactions between Fe3+ sites; thus, the spectral density can be altered by changing the Fe3+ concentration. Moreover, we find that the spectral density is very wide, having strong contributions all the way from mid-kHz fluctuations to MHz fluctuations near the proton Larmor frequencies. Significant variations in the R/ç ratio were also observed in the injection-molded disk, which reflect either a processing-induced heterogeneity in clay dispersion or a significant variation in cooling history from region to region. Proton spin diffusion and multiple-pulse methods were utilized to compare morphologies for a diamagnetic NnC and nylon-6 with the same thermal histories. Long spacing, crystallinity, and the mobility of the noncrystalline nylon-6 segments are very similar for NnCâs and nylon-6.

Vanderhart, D. L.; Asano, A.; Gilman, J. W.

2001-01-01

140

A CMOS microcoil-associated preamplifier for NMR spectroscopy  

Microsoft Academic Search

For improving sensitivity of nuclear magnetic resonance (NMR) measurements, an in-field preamplifier in a low-cost CMOS process is presented. It is based on a second-generation positive current conveyor (CCII+), with an impedance-matching output stage. The circuit has been designed with optimization of key performances, such as bandwidth, noise, and offset voltage. There have also been precautions taken against potential effect

Tewfik Cherifi; Nacer Abouchi; Guo-Neng Lu; Latifa Bouchet-Fakri; Laurent Quiquerez; B. Sorli; Jean-François Chateaux; M. Pitaval; P. Morin

2005-01-01

141

On-chip integration of high-frequency electron paramagnetic resonance spectroscopy and Hall-effect magnetometry.  

PubMed

A sensor that integrates high-sensitivity micro-Hall effect magnetometry and high-frequency electron paramagnetic resonance spectroscopy capabilities on a single semiconductor chip is presented. The Hall-effect magnetometer (HEM) was fabricated from a two-dimensional electron gas GaAsAlGaAs heterostructure in the form of a cross, with a 50 x 50 microm2 sensing area. A high-frequency microstrip resonator is coupled with two small gaps to a transmission line with a 50 Omega impedance. Different resonator lengths are used to obtain quasi-TEM fundamental resonant modes in the frequency range 10-30 GHz. The resonator is positioned on top of the active area of the HEM, where the magnetic field of the fundamental mode is largest, thus optimizing the conversion of microwave power into magnetic field at the sample position. The two gaps coupling the resonator and transmission lines are engineered differently--the gap to the microwave source is designed to optimize the loaded quality factor of the resonator (Q

Quddusi, H M; Ramsey, C M; Gonzalez-Pons, J C; Henderson, J J; del Barco, E; de Loubens, G; Kent, A D

2008-07-01

142

Solid-State NMR Spectroscopy of Membrane-Associated Myelin Basic Protein—Conformation and Dynamics of an Immunodominant Epitope  

PubMed Central

Myelin basic protein (MBP) maintains the tight multilamellar compaction of the myelin sheath in the central nervous system through peripheral binding of adjacent lipid bilayers of oligodendrocytes. Myelin instability in multiple sclerosis (MS) is associated with the loss of positive charge in MBP as a result of posttranslational enzymatic deimination. A highly-conserved central membrane-binding fragment (murine N81-PVVHFFKNIVTPRTPPP-S99, identical to human N83-S101) represents a primary immunodominant epitope in MS. Previous low-resolution electron paramagnetic resonance measurements on the V83-T92 fragment, with Cys-mutations and spin-labeling that scanned the epitope, were consistent with it being a membrane-associated amphipathic ?-helix. Pseudodeimination at several sites throughout the protein, all distal to the central segment, disrupted the ?-helix at its amino-terminus and exposed it to proteases, representing a potential mechanism in the autoimmune pathogenesis of MS. Here, we have used magic-angle spinning solid-state NMR spectroscopy to characterize more precisely the molecular conformation and dynamics of this central immunodominant epitope of MBP in a lipid milieu, without Cys-substitution. Our solid-state NMR measurements have revealed that the ?-helix present within the immunodominant epitope is shorter than originally modeled, and is independent of the pseudodeimination, highlighting the importance of the local hydrophobic effects in helix formation and stability. The main effect of pseudodeimination is to cause the cytoplasmic exposure of the fragment, potentially making it more accessible to proteolysis. These results are the first, to our knowledge, to provide atomic-level detail of a membrane-anchoring segment of MBP, and direct evidence of decreased MBP-membrane interaction after posttranslational modification. PMID:20713009

Ahmed, Mumdooh A.M.; Bamm, Vladimir V.; Harauz, George; Ladizhansky, Vladimir

2010-01-01

143

Investigation of aluminum complexes in alcoholic tetraoctylammonium (TOA) aluminate solutions using aluminum-27 NMR spectroscopy  

NASA Astrophysics Data System (ADS)

27Al NMR spectroscopy is a powerful tool for investigation of the aluminate species existing in both aqueous and non-aqueous solutions. This method can also be used to determine thermodynamic properties of complexes in solution. In the present work, 27Al NMR spectroscopy was used to characterize species present in the alkaline aqueous and alcoholic aluminate solutions. Tetraoctylammonium hydroxide (TOAOH) was used as the base. In a solution of CH3OH and H2O at a mole ratio of 20:1, it was possible to detect five signals by 27Al NMR spectra, indicating formation of the [Al(OH)4-n(CH3OH)n](n-1)+ (n = 0, 1, 2, 3, and 4) species. 27Al NMR spectroscopy was also used in order to investigate the species present in the ethanolic and propanolic TOA aluminate solutions. The equilibrium constants for the formation of alcoholic aluminate complexes were also determined. Finally, the 27Al NMR spectra of butanolic TOA aluminate solutions were studied.

Goudarzi, Nasser

2013-08-01

144

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

145

Characterizing Covalently Sidewall-Functionalized SWCNTs by using 1H NMR Spectroscopy  

PubMed Central

Unambiguous evidence for covalent sidewall functionalization of single-walled carbon nanotubes (SWCNTs) has been a difficult task, especially for nanomaterials in which slight differences in functionality structure produce significant changes in molecular characteristics. Nuclear magnetic resonance (NMR) spectroscopy provides clear information about the structural skeleton of molecules attached to SWCNTs. In order to establish the generality of proton NMR as an analytical technique for characterizing covalently functionalized SWCNTs, we have obtained and analyzed proton NMR data of SWCNT-substituted benzenes across a variety of para substituents. Trends obtained for differences in proton NMR chemical shifts and the impact of o-, p-, and m-directing effects of electrophilic aromatic substituents on phenyl groups covalently bonded to SWCNTs are discussed. PMID:24009779

Nelson, Donna J.; Kumar, Ravi

2013-01-01

146

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

147

Slow-spinning low-sideband HR-MAS NMR spectroscopy: delicate analysis of biological samples  

NASA Astrophysics Data System (ADS)

High-Resolution Magic-Angle Spinning (HR-MAS) NMR spectroscopy has become an extremely versatile analytical tool to study heterogeneous systems endowed with liquid-like dynamics. Spinning frequencies of several kHz are however required to obtain NMR spectra, devoid of spinning sidebands, with a resolution approaching that of purely isotropic liquid samples. An important limitation of the method is the large centrifugal forces that can damage the structure of the sample. In this communication, we show that optimizing the sample preparation, particularly avoiding air bubbles, and the geometry of the sample chamber of the HR-MAS rotor leads to high-quality low-sideband NMR spectra even at very moderate spinning frequencies, thus allowing the use of well-established solution-state NMR procedures for the characterization of small and highly dynamic molecules in the most fragile samples, such as live cells and intact tissues.

Renault, Marie; Shintu, Laetitia; Piotto, Martial; Caldarelli, Stefano

2013-11-01

148

Slow-spinning low-sideband HR-MAS NMR spectroscopy: delicate analysis of biological samples.  

PubMed

High-Resolution Magic-Angle Spinning (HR-MAS) NMR spectroscopy has become an extremely versatile analytical tool to study heterogeneous systems endowed with liquid-like dynamics. Spinning frequencies of several kHz are however required to obtain NMR spectra, devoid of spinning sidebands, with a resolution approaching that of purely isotropic liquid samples. An important limitation of the method is the large centrifugal forces that can damage the structure of the sample. In this communication, we show that optimizing the sample preparation, particularly avoiding air bubbles, and the geometry of the sample chamber of the HR-MAS rotor leads to high-quality low-sideband NMR spectra even at very moderate spinning frequencies, thus allowing the use of well-established solution-state NMR procedures for the characterization of small and highly dynamic molecules in the most fragile samples, such as live cells and intact tissues. PMID:24284435

Renault, Marie; Shintu, Laetitia; Piotto, Martial; Caldarelli, Stefano

2013-01-01

149

Supramolecular complex formed by DNA oligonucleotide and thiacalix[4]arene. NMR-spectroscopy and molecular docking  

NASA Astrophysics Data System (ADS)

The combination of NMR-spectroscopy and molecular docking was applied to investigate the complexation of thiacalix[4]arene with DNA. We have studied the structure of supramolecular complex formed by palindromic decamer DNA d(GCGTTAACGC)2 and tetrasubstituted at lower rim of p-tert-butyl thiacalix[4]arene in 1,3-alternate conformation. With the help of NMR it is shown that oligonucleotide in solution exists in two states: double-stranded helix (dominant structure in solution) and single-stranded form (minor structure) rolled up in a “hairpin” with equilibrium between them. Both complementary methods, NMR and molecular docking, revealed the formation of molecular complex by thiacalix[4]arene and palindromic decamer DNA. Different possible conformations of the complexes were analyzed by means of molecular docking. We used the experimental constraints in molecular docking to identify the complexes, which were in agreement with the NMR data.

Khairutdinov, Bulat; Ermakova, Elena; Sitnitsky, Aleksandr; Stoikov, Ivan; Zuev, Yuriy

2014-09-01

150

Next-generation heteronuclear decoupling for high-field biomolecular NMR spectroscopy.  

PubMed

Ultra-high-field NMR spectroscopy requires an increased bandwidth for heteronuclear decoupling, especially in biomolecular NMR applications. Composite pulse decoupling cannot provide sufficient bandwidth at practical power levels, and adiabatic pulse decoupling with sufficient bandwidth is compromised by sideband artifacts. A novel low-power, broadband heteronuclear decoupling pulse is presented that generates minimal, ultra-low sidebands. The pulse was derived using optimal control theory and represents a new generation of decoupling pulses free from the constraints of periodic and cyclic sequences. In comparison to currently available state-of-the-art methods this novel pulse provides greatly improved decoupling performance that satisfies the demands of high-field biomolecular NMR spectroscopy. PMID:24623579

Schilling, Franz; Warner, Lisa R; Gershenzon, Naum I; Skinner, Thomas E; Sattler, Michael; Glaser, Steffen J

2014-04-22

151

Probing acid-amide intermolecular hydrogen bonding by NMR spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

Benzene carboxylic acids and benzamide act as their self-complement in molecular recognition to form inter-molecular hydrogen bonded dimers between amide and carboxylic acid groups, which have been investigated by 1H, 13C and 15N NMR spectroscopy. Extensive NMR studies using diffusion ordered spectroscopy (DOSY), variable temperature 1D, 2D NMR, established the formation of heterodimers of benzamide with benzoic acid, salicylic acid and phenyl acetic acid in deuterated chloroform solution. Association constants for the complex formation in the solution state have been determined. The results are ascertained by X-ray diffraction in the solid state. Intermolecular interactions in solution and in solid state were found to be similar. The structural parameters obtained by X-ray diffraction studies are compared with those obtained by DFT calculations.

Chaudhari, Sachin Rama; Suryaprakash, N.

2012-05-01

152

Use of NMR Saturation Transfer Difference Spectroscopy to Study Ligand Binding to Membrane Proteins  

PubMed Central

Detection of weak ligand binding to membrane-spanning proteins, such as receptor proteins at low physiological concentrations, poses serious experimental challenges. Saturation transfer difference nuclear magnetic resonance (STD-NMR) spectroscopy offers an excellent way to surmount these problems. As the name suggests, magnetization transferred from the receptor to its bound ligand is measured by directly observing NMR signals from the ligand itself. Low-power irradiation is applied to a 1H NMR spectral region containing protein signals but no ligand signals. This irradiation spreads quickly throughout the membrane protein by the process of spin diffusion and saturates all protein 1H NMR signals. 1H NMR signals from a ligand bound transiently to the membrane protein become saturated and, upon dissociation, serve to decrease the intensity of the 1H NMR signals measured from the pool of free ligand. The experiment is repeated with the irradiation pulse placed outside the spectral region of protein and ligand, a condition that does not lead to saturation transfer to the ligand. The two resulting spectra are subtracted to yield the difference spectrum. As an illustration of the methodology, we review here STD-NMR experiments designed to investigate binding of ligands to the human sweet taste receptor, a member of the large family of G-protein-coupled receptors. Sweetener molecules bind to the sweet receptor with low affinity but high specificity and lead to a variety of physiological responses. PMID:22976022

Venkitakrishnan, Rani Parvathy; Benard, Outhiriaradjou; Max, Marianna; Markley, John L.

2013-01-01

153

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

154

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

155

High-Resolution Solid-State NMR Spectroscopy: Characterization of Polymorphism in Cimetidine, a Pharmaceutical Compound  

ERIC Educational Resources Information Center

High-resolution solid-state NMR (SSNMR) spectroscopy has many advantages as a tool to characterize solid-phase material that finds applications in polymer chemistry, nanotechnology, materials science, biomolecular structure determination, and others, including the pharmaceutical industry. The technology associated with achieving high resolution…

Pacilio, Julia E.; Tokarski, John T.; Quiñones, Rosalynn; Iuliucci, Robbie J.

2014-01-01

156

DHA and EPA Interaction with Raft Domains Observed With Solid-State 2 H NMR Spectroscopy  

E-print Network

DHA and EPA Interaction with Raft Domains Observed With Solid-State 2 H NMR Spectroscopy Jacob J phospholipids and modify the structure and organization of lipid rafts, thus affecting cell signaling. We used-eicosapentaenoylphosphatidylcholine (PEPC) and 1-palmitoyl- 2-docosahexaenoylphosphatidylcholine (PDPC) with the raft

Zhou, Yaoqi

157

NATURAL ABUNDANCE 13C NMR SPECTROSCOPY OF DOUBLE-STRANDED DNA  

EPA Science Inventory

Although 13C NMR spectroscopy has already proved extremely useful in studies of biopolymers, including t-RNA's, and single-stranded polynucleotides, no successful study of native double-stranded DNA has been reported. This failure is mainly due to extremely unfavorable 13C spin r...

158

Identification and Quantitative Determination of Dipropylene Glycol in Terpene Mixtures Using 13C NMR Spectroscopy  

Microsoft Academic Search

A method that allows direct identification and quantitative determination of dipropylene glycol (DPG) using C NMR spectroscopy was developed. The quantitative procedure was checked and validated with commercially available DPG, controlled with two DPG-added essential oils, and then applied to commercial “Extraits de parfum” (perfume extracts).

Josephine Ottavioli; Joseph Casanova; Ange Bighelli

2011-01-01

159

Mobility and relaxation determinations of lithium in lithium aluminate ceramics using solid-state NMR spectroscopy  

Microsoft Academic Search

Lithium aluminate is one of the materials being considered for fusion reactor blankets. When preparing the ceramic, it is important to be able to monitor the microstructures since it is a controlling factor in the rate of tritium release from the blanket. Nuclear magnetic resonance spectroscopy (NMR) has been shown to be a useful tool for the nondestructive analysis of

F. F. Stewart; E. S. Peterson; J. F. Stebbins; Ian Farnan; S. O. Dunham; E. Adams; P. W. Jennings

1995-01-01

160

Temperature Gradients and Sample Heating in Variable Temperature High Speed MAS NMR Spectroscopy  

Microsoft Academic Search

High speed magic angle spinning NMR spectroscopy offers the possibility of im- proving the process of coherent averaging of various parts of the nuclear spin Hamil- tonian in the solid state ( 1-6). This considerably reduces the intensities of rotational sidebands. This isa great advantage especially in cross-polarization MAS experiments at high magnetic fields, where rotational sidebands mostly stem from

Institutftir Physikalische; Johannes Hess Strasse

161

PHIP NMR Spectroscopy in Ionic Liquids: Influence of Salts on the Intensity of Polarization Signals.  

PubMed

Parahydrogen-induced dynamic nuclear polarization NMR spectroscopy (PHIP) in ionic liquids leads to weak or no polarization signals, depending on the type of experiment. We demonstrate that the intensity of polarization is directly correlated to the concentration of the ionic liquids. High ion concentration is connected to fast T1 relaxation, resulting in annihilation of the polarization signals. PMID:25263717

Bröhl, Andreas; Giernoth, Ralf

2014-10-21

162

Ghost-peak suppression in ultrafast two-dimensional NMR spectroscopy  

E-print Network

Ghost-peak suppression in ultrafast two-dimensional NMR spectroscopy Yoav Shrot and Lucio Frydman indirect-domain spectral resolution. Brief mathematical descriptions of the ghost-peak generation and ghost; Ultrafast acquisitions; Ghost-peaks; Artifact suppression; Resolution enhancement 1. Introduction

Frydman, Lucio

163

Supramolecular Interactions at the Picomole Level Studied by 19F NMR Spectroscopy in a Microfluidic Chip  

Microsoft Academic Search

Small-scale chips: 19F NMR spectroscopy is performed on nanoliter volumes in a microfluidic chip equipped with a planar microcoil. The high resolution and sensitivity allow the detection of small chemical shift variations, which enables investigation of the supramolecular interaction between NaPF6 and ?-cyclodextrin.

M. Victoria Gomez; David N. Reinhoudt; Aldrik H. Velders

2008-01-01

164

Positional isotope exchange studies on enzyme using NMR spectroscopy  

SciTech Connect

The isotopically enriched compounds, /sup 18/O-..beta..,..gamma..-ATP and /sup 18/O bridge-labeled pyrophosphate, synthesized previously in this laboratory, were used to investigate and measure the exchange vs. turnover of substrates and products from their central complexes in four selected enzyme systems. Using hi-field /sup 31/P NMR, we were able to differentiate between /sup 18/O labeled in the bridge vs. the non-bridge positions by virtue of the isotope shift upon the phosphorus nuclei. The bridge to non-bridge scrambling of the label was quantitated and the exchange vs. turnover ratios under a variety of conditions was determined. Using the substrate inhibitor carboxycreatinine, PIX experiments with /sup 18/O-..beta..,..gamma..-ATP and creatine kinase were conducted. It was shown that carboxycreatinine and creatine kinase promoted exchange of the /sup 18/O label as determined by NMR. We have concluded that carboxycreatinine is either a substrate that catalyzes very slow turnover or it catalyzes exchange by a dissociative (SN/sub 1//sub P/) type of mechanism

Matsunaga, T.O.

1987-01-01

165

Water behavior in bacterial spores by deuterium NMR spectroscopy.  

PubMed

Dormant bacterial spores are able to survive long periods of time without nutrients, withstand harsh environmental conditions, and germinate into metabolically active bacteria when conditions are favorable. Numerous factors influence this hardiness, including the spore structure and the presence of compounds to protect DNA from damage. It is known that the water content of the spore core plays a role in resistance to degradation, but the exact state of water inside the core is a subject of discussion. Two main theories present themselves: either the water in the spore core is mostly immobile and the core and its components are in a glassy state, or the core is a gel with mobile water around components which themselves have limited mobility. Using deuterium solid-state NMR experiments, we examine the nature of the water in the spore core. Our data show the presence of unbound water, bound water, and deuterated biomolecules that also contain labile deuterons. Deuterium-hydrogen exchange experiments show that most of these deuterons are inaccessible by external water. We believe that these unreachable deuterons are in a chemical bonding state that prevents exchange. Variable-temperature NMR results suggest that the spore core is more rigid than would be expected for a gel-like state. However, our rigid core interpretation may only apply to dried spores whereas a gel core may exist in aqueous suspension. Nonetheless, the gel core, if present, is inaccessible to external water. PMID:24950158

Friedline, Anthony W; Zachariah, Malcolm M; Johnson, Karen; Thomas, Kieth J; Middaugh, Amy N; Garimella, Ravindranath; Powell, Douglas R; Vaishampayan, Parag A; Rice, Charles V

2014-07-31

166

A system for NMR stark spectroscopy of quadrupolar nuclei.  

PubMed

Electrostatic influences on NMR parameters are well accepted. Experimental and computational routes have been long pursued to understand and utilize such Stark effects. However, existing approaches are largely indirect informants on electric fields, and/or are complicated by multiple causal factors in spectroscopic change. We present a system to directly measure quadrupolar Stark effects from an applied electric (E) field. Our apparatus and applications are relevant in two contexts. Each uses a radiofrequency (rf) E field at twice the nuclear Larmor frequency (2omega(0)). The mechanism is a distortion of the E-field gradient tensor that is linear in the amplitude (E(0)) of the rf E field. The first uses 2omega(0) excitation of double-quantum transitions for times similar to T(1) (the longitudinal spin relaxation time). This perturbs the steady state distribution of spin population. Nonlinear analysis versus E(0) can be used to determine the Stark response rate. The second context uses POWER (perturbations observed with enhanced resolution) NMR. Here, coherent, short-time (NMR multiple-pulse line-narrowing sequence. Linear analysis of the Stark response is then possible: a quadrupolar multiplet with splitting proportional to E(0). The POWER sequence converts the 2omega(0) interaction from off-diagonal/nonsecular to the familiar diagonal form (I(z)(2)) of static quadrupole interactions. Meanwhile, background contributions to line width are averaged to zero, providing orders-of-magnitude resolution enhancement for correspondingly high sensitivity to the Stark effect. Using GaAs as a test case with well-defined Stark response, we provide the first demonstration of the 2omega(0) effect at high-field (14.1 T) and room temperature. This, along with the simplicity of our apparatus and spectral approach, may facilitate extensions to a wider array of material and molecular systems. The POWER context, which has not previously been tested, is detailed here with new design insights. Several key aspects are demonstrated here, while complete implementation is to be presented at a later time. At present, we (1) account for finite pulse times in pulse sequence design, (2) demonstrate two-channel phase coherence for magnetic (omega(0)) and electric (2omega(0)) excitation, and (3) provide line narrowing by a factor of 10(3). In addition, we find that certain anomalous contributions to the line shape, observed in previous low-field (250 mT) applications, are absent here. PMID:20394397

Tarasek, Matthew R; Kempf, James G

2010-05-13

167

New methods and applications in solid-state NMR spectroscopy of quadrupolar nuclei.  

PubMed

Solid-state nuclear magnetic resonance (NMR) spectroscopy has long been established as offering unique atomic-scale and element-specific insight into the structure, disorder, and dynamics of materials. NMR spectra of quadrupolar nuclei (I > (1)/2) are often perceived as being challenging to acquire and to interpret because of the presence of anisotropic broadening arising from the interaction of the electric field gradient and the nuclear electric quadrupole moment, which broadens the spectral lines, often over several megahertz. Despite the vast amount of information contained in the spectral line shapes, the problems with sensitivity and resolution have, until very recently, limited the application of NMR spectroscopy of quadrupolar nuclei in the solid state. In this Perspective, we provide a brief overview of the quadrupolar interaction, describe some of the basic experimental approaches used for acquiring high-resolution NMR spectra, and discuss the information that these spectra can provide. We then describe some interesting recent examples to showcase some of the more exciting and challenging new applications of NMR spectra of quadrupolar nuclei in the fields of energy materials, microporous materials, Earth sciences, and biomaterials. Finally, we consider the possible directions that this highly informative technique may take in the future. PMID:25296129

Ashbrook, Sharon E; Sneddon, Scott

2014-11-01

168

Paramagnetism (GCMP)  

NSDL National Science Digital Library

Paramagnetism: this is a resource in the collection "General Chemistry Multimedia Problems". In this problem we will begin by observing the magnetism of three manganese compounds. These compounds have been placed in capsules, which will be pulled toward a magnet if the compound is paramagnetic. General Chemistry Multimedia Problems ask students questions about experiments they see presented using videos and images. The questions asked apply concepts from different parts of an introductory course, encouraging students to decompartmentalize the material.

169

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

170

Solid-State NMR Investigation of Paramagnetic Nylon-6 Clay Nanocomposites. 2. Measurement of Clay Dispersion, Crystal Stratification, and Stability of Organic Modifiers  

NSDL National Science Digital Library

In this second paper of a two-part series dealing mainly with NMR characterization of nylon-6/clay nanocomposites (NnCâs) having nominally 5 mass % clay, measurements with application to processing are featured. The paramagnetism of the montmorillonite clays, discussed in the first paper, allowed us to use the corresponding spin-diffusion-moderated reduction in longitudinal proton relaxation time, T1 H, for two purposes, namely, to rank the quality of clay dispersion in NnC families with the same formulation and to investigate morphological stratification of the nylon-6 R- and ç-crystallites with respect to the clay surface. In a group of three NnCâs with the same formulation but different melt-blending conditions, variations in T1 H correlated well with previously published TEM assessments of the quality of the clay dispersion. Also, in a set of samples from an injection-molded, in situ polymerized NnC disk where strong variations in R/ç ratios were observed, it was found that these differences did not arise from processing-induced inhomogeneities in clay concentration; rather, variations in cooling histories throughout the disk was the more probable cause. In these latter samples, well-defined stratification of the ç-phase (versus the R-phase) crystallites nearer the clay surface did not occur until after annealing at 214 °C. We also examined the dependence of NnC T1 Hâs on the static field of the measurement. It is clear that the magnitude of the paramagnetic contribution to T1 H is a function of field and of Fe3+ concentration in the clay. Trends support the notion that spin-exchange interactions between the electrons on different Fe3+ ions largely define the spectral density of magnetic fluctuations near the clay surface. Some attention was, therefore, given to optimizing Fe3+ concentrations for the best NnC characterization. Finally, we investigated the chemical stability of a particular organic modifier (OM), which is used to pretreat the clay prior to melt blending. The OM, dimethyl, dehydrogenated-tallow ammonium ion, was followed in the process of blending this modified clay with nylon-6 at 240 °C. It was found that when such a clay surface was exposed to the nylon-6 during blending, most of the OM on that surface decomposed, releasing a free amine with one methyl and two tallow substituents. However, subsequent melting at 240 °C produced no further decomposition. The implication is that the combination of temperature and shear stress in blending causes decomposition, not just temperature alone. The susceptibility to chemical decomposition varied strongly with the OM. Ironically, extensive decomposition of the OM did not result in poor mixing; in fact, as judged by T1 H, the NnC with the best dispersion of clay also had the most extensively degraded OM. The implications of this degradation for the physical properties have not been explored in detail.

Vanderhart, D. L.; Asano, A.; Gilman, J. W.

2001-01-01

171

Reactivity ratios and sequence determination of methacrylonitrile/butyl acrylate copolymers by NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Methacrylonitrile/butyl acrylate (M/B) copolymers were prepared by bulk polymerization using benzoyl peroxide as an initiator. The Distortionless Enhancement by Polarization Transfer spectra were used to differentiate between the carbon resonance signals of methyl, methine, methylene and oxymethylene groups in the 13C{ 1H} NMR spectrum of the copolymer (M/B). Comonomer reactivity ratios were determined using Kelen-Tudos and non-linear error in variable methods. Two-dimensional Heteronuclear Single Quantum Coherence and Total Correlated Spectroscopy were used to resolve the complex 1H NMR spectrum and to determine the compositional and configurational sequences of M/B copolymers.

Brar, A. S.; Pradhan, D. R.; Hooda, Sunita

2004-08-01

172

Secondary structure, dynamics, and architecture of the p7 membrane protein from hepatitis C virus by NMR spectroscopy  

Microsoft Academic Search

P7 is a small membrane protein that is essential for the infectivity of hepatitis C virus. Solution-state NMR experiments on p7 in DHPC micelles, including hydrogen\\/deuterium exchange, paramagnetic relaxation enhancement and bicelle ‘q-titration,’ demonstrate that the protein has a range of dynamic properties and distinct structural segments. These data along with residual dipolar couplings yield a secondary structure model of

Gabriel A. Cook

2011-01-01

173

Application of electron paramagnetic resonance spectroscopy to comparative examination of different groups of free radicals in thermal injuries treated with propolis and silver sulphadiazine.  

PubMed

Different groups of free radicals expressed in burn wounds treated with propolis and silver sulphadiazine were examined. The thermal effect forms major types of free radicals in a wound because of the breaking of chemical bonds. Free radicals, located in the heated skin, were tested after 21 days of treating by these two substances. The aim of this work was to find the method for determination of types and concentrations of different groups of free radicals in wound after high temperature impact during burning. The effects of the therapy by propolis and silver sulphadiazine on free radicals were studied. Since the chemical methods of free radicals studies are destructive, the usefulness of the electron paramagnetic resonance spectroscopy was tested in this work. The electron paramagnetic resonance spectra measured with the microwave power of 2.2?mW were numerically fitted by theoretical curves of Gaussian and Lorentzian shapes. The experimental electron paramagnetic resonance spectra of tissue samples are best fitted by the sum of one Gauss and two Lorentz lines. An innovatory numerical procedure of spectroscopic skin analysis was presented. It is very useful in the alternative medicine studies. PMID:23762162

Olczyk, Pawel; Ramos, Pawel; Bernas, Marcin; Komosinska-Vassev, Katarzyna; Stojko, Jerzy; Pilawa, Barbara

2013-01-01

174

Application of Electron Paramagnetic Resonance Spectroscopy to Comparative Examination of Different Groups of Free Radicals in Thermal Injuries Treated with Propolis and Silver Sulphadiazine  

PubMed Central

Different groups of free radicals expressed in burn wounds treated with propolis and silver sulphadiazine were examined. The thermal effect forms major types of free radicals in a wound because of the breaking of chemical bonds. Free radicals, located in the heated skin, were tested after 21 days of treating by these two substances. The aim of this work was to find the method for determination of types and concentrations of different groups of free radicals in wound after high temperature impact during burning. The effects of the therapy by propolis and silver sulphadiazine on free radicals were studied. Since the chemical methods of free radicals studies are destructive, the usefulness of the electron paramagnetic resonance spectroscopy was tested in this work. The electron paramagnetic resonance spectra measured with the microwave power of 2.2?mW were numerically fitted by theoretical curves of Gaussian and Lorentzian shapes. The experimental electron paramagnetic resonance spectra of tissue samples are best fitted by the sum of one Gauss and two Lorentz lines. An innovatory numerical procedure of spectroscopic skin analysis was presented. It is very useful in the alternative medicine studies. PMID:23762162

Olczyk, Pawel; Ramos, Pawel; Bernas, Marcin; Komosinska-Vassev, Katarzyna; Stojko, Jerzy; Pilawa, Barbara

2013-01-01

175

A mobile NMR system with full spectroscopy capability.  

PubMed

This paper reports our work in developing a mobile nuclear magnetic resonance system with full spectroscopy capability. The system consists of a 0.93 T, portable permanent magnet, a 8-turn 550 µm diameter microcoil, and compact electronics systems. The system provides 0.4 parts per million spectrum linewidth and 408 signal-to-noise ratio from a 37 nL water sample with 128 averages. Representative (1)H and (19)F spectra are presented. PMID:23366810

Ma, Chao; Liang, Zhi-Pei

2012-01-01

176

Chemical-shift-resolved ¹?F NMR spectroscopy between 13.5 and 135 MHz: Overhauser-DNP-enhanced diagonal suppressed correlation spectroscopy.  

PubMed

Overhauser-DNP-enhanced homonuclear 2D (19)F correlation spectroscopy with diagonal suppression is presented for small molecules in the solution state at moderate fields. Multi-frequency, multi-radical studies demonstrate that these relatively low-field experiments may be operated with sensitivity rivalling that of standard 200-1000?MHz NMR spectroscopy. Structural information is accessible without a sensitivity penalty, and diagonal suppressed 2D NMR correlations emerge despite the general lack of multiplet resolution in the 1D ODNP spectra. This powerful general approach avoids the rather stiff excitation, detection, and other special requirements of high-field (19)F?NMR spectroscopy. PMID:24962142

George, Christy; Chandrakumar, Narayanan

2014-08-01

177

Fundamental studies of supported bimetallic catalysts by NMR spectroscopy  

SciTech Connect

Various hydrogenation reactions on transition metals are important commercially whereas certain hydrogenolysis reactions are useful from fundamental point of view. Understanding the hydrogen mobility and kinetics of adsorption-desorption of hydrogen is important in understanding the mechanisms of such reactions involving hydrogen. The kinetics of hydrogen chemisorption was studied by means of selective excitation NMR on silica supported Pt, Rh and Pt-Rh catalysts. The activation energy of hydrogen desorption was found to be lower on silica supported Pt catalysts as compared to Rh and Pt-Rh catalysts. It was found that the rates of hydrogen adsorption and desorption on Pt-Rh catalyst were similar to those on Rh catalyst and much higher as compared to Pt catalyst. The Ru-Ag bimetallic system is much simpler to study than the Pt-Rh system and serves as a model system to characterize more complicated systems such as the K/Ru system. Ag was found to decrease the amounts of adsorbed hydrogen and the hydrogen-to-ruthenium stoichiometry. Ag reduced the populations of states with low and intermediate binding energies of hydrogen on silica supported Ru catalyst. The rates of hydrogen adsorption and desorption were also lower on silica supported Ru-Ag catalyst as compared to Ru catalyst. This report contains introductory information, the literature review, general conclusions, and four appendices. An additional four chapters and one appendix have been processed separately for inclusion on the data base.

Savargaonkar, N.

1996-10-17

178

Magnesium and Calcium Aluminate Liquids: In Situ High-Temperature 27Al NMR Spectroscopy.  

PubMed

The use of high-temperature nuclear magnetic resonance (NMR) spectroscopy provides a means of investigating the structure of refractory aluminate liquids at temperatures up to 2500 K. Time-averaged structural information indicates that the average aluminum coordination for magnesium aluminate (MgAl(2)O(4)) liquid is slightly greater than for calcium aluminate (CaAl(2)O(4)) liquid and that in both liquids it is close to four. Ion dynamics simulations for these liquids suggest the presence of four-, five-, and six-coordinated aluminate species, in agreement with NMR experiments on fast-quenched glasses. These species undergo rapid chemical exchange in the high-temperature liquids, which is evidenced by a single Lorentzian NMR line. PMID:17809340

Poe, B T; McMillan, P F; Coté, B; Massiot, D; Coutures, J P

1993-02-01

179

Metabolic fingerprint of Brazilian maize landraces silk (stigma/styles) using NMR spectroscopy and chemometric methods.  

PubMed

Aqueous extract from maize silks is used by traditional medicine for the treatment of several ailments, mainly related to the urinary system. This work focuses on the application of NMR spectroscopy and chemometric analysis for the determination of metabolic fingerprint and pattern recognition of silk extracts from seven maize landraces cultivated in southern Brazil. Principal component analysis (PCA) of the (1)H NMR data set showed clear discrimination among the maize varieties by PC1 and PC2, pointing out three distinct metabolic profiles. Target compounds analysis showed significant differences (p < 0.05) in the contents of protocatechuic acid, gallic acid, t-cinnamic acid, and anthocyanins, corroborating the discrimination of the genotypes in this study as revealed by PCA analysis. Thus the combination of (1)H NMR and PCA is a useful tool for the discrimination of maize silks in respect to their chemical composition, including rapid authentication of the raw material of current pharmacological interest. PMID:20088591

Kuhnen, Shirley; Bernardi Ogliari, Juliana; Dias, Paulo Fernando; da Silva Santos, Maiara; Ferreira, Antônio Gilberto; Bonham, Connie C; Wood, Karl Vernon; Maraschin, Marcelo

2010-02-24

180

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

181

Characterization of covalent protein conjugates using solid-state sup 13 C NMR spectroscopy  

SciTech Connect

Cross-polarization magic-angle spinning (CPMAS) {sup 13}C NMR spectroscopy has been used to characterize covalent conjugates of alachlor, an {alpha}-chloroacetamide hapten, with glutathione (GSH) and bovine serum albumin (BSA). The solid-state NMR method demonstrates definitively the covalent nature of these conjugates and can also be used to characterize the sites of hapten attachment to proteins. Three different sites of alachlor binding are observed in the BSA system. Accurate quantitation of the amount of hapten covalently bound to GSH and BSA is reported. The solid-state {sup 13}C NMR technique can easily be generalized to study other small molecule/protein conjugates and can be used to assist the development and refinement of synthetic methods needed for the successful formation of such protein alkylation products.

Garbow, J.R.; Fujiwara, Hideji; Sharp, C.R.; Logusch, E.W. (Monsanto Co., St. Louis, MO (United States))

1991-07-23

182

Nuclear charge-distribution effects on the NMR spectroscopy parameters  

NASA Astrophysics Data System (ADS)

We present here a systematic study about the influence of the size and type of nuclear charge-distribution models (Gaussian and point-like) on the NMR spectroscopic parameters, the nuclear magnetic shielding ? and the indirect nuclear spin J-coupling. We found that relativistic effects largely enhance the nuclear charge-distribution effects (NChDE) on those parameters being them quite sensitive to the nuclear model adopted for calculations. Results for two rare gas atoms (Kr, Rn) and few molecular systems like HX, (X = Br, I, At), CH4, SnH4, SnIH3, SnI2H2, and PbIH3 are presented. J-couplings are more sensitive than shieldings in both, relativistic and non-relativistic (NR) regimes. The highest effect (close to 11% of variation in relativistic calculations with that two different nuclear models) is observed for J(Pb-I) in PbIH3. A similar effect is found for J(Pb-H) in the same molecule, close to 9%. The NChDE for ?(Sn) in SnI4-nHn with n = 1, 2 is as large as few ppm (between 3 and 8.56 ppm). For J(Sn-H) in this set of molecules, it goes from 37 Hz for SnH4 to 54 Hz for SnI2H2. Furthermore, we found that the vicinal NChDE is very small though not zero. For 1J(Sn-H) in SnIH3, the NChDE of iodine is close to 2 Hz (0.1%). We also studied the NChDE on the ground state electronic energies of atoms and molecules. We found that these effects are only important within the relativistic regime but not within the NR one. They are in good agreement with previous works.

Maldonado, Alejandro F.; Giménez, Carlos A.; Aucar, Gustavo A.

2012-06-01

183

Impurity profiling in bulk pharmaceutical batches using 19F NMR spectroscopy and distinction between monomeric and dimeric impurities by NMR-based diffusion measurements  

Microsoft Academic Search

The impurity profile of production batches of fluorine-containing drugs can be characterised efficiently using 19F NMR spectroscopy. This yields the number and proportions of impurities in the bulk drug to a level of ?0.1 mole% in a few minutes of NMR experiment time. The approach has been exemplified using a partially purified batch of the steroidal product fluticasone propionate, the

Nisha Mistry; Ismail M. Ismail; R. Duncan Farrant; Maili Liu; Jeremy K. Nicholson; John C. Lindon

1999-01-01

184

On the possibilities of in situ studies of the hydration of aluminate cements using wideline 27Al NMR spectroscopy  

Microsoft Academic Search

Wideline 27Al NMR spectroscopy has been applied to the investigation of the hydration of CA, CA2 and C3A. A selective disappearance of the lower frequency part of the 27Al NMR line of original CA was observed during hydration. The deconvolution of 27Al NMR spectra of anhydrous and hydrated CA into a number (6 to 9) of gaussian components allowed for

A. B. Kudryavtsev; T. V. Kouznetsova; W. Linert; G. Hunter

1997-01-01

185

Monitoring the Electrochemical Processes in the Lithium-Air Battery by Solid State NMR Spectroscopy  

PubMed Central

A multi-nuclear solid-state NMR approach is employed to investigate the lithium–air battery, to monitor the evolution of the electrochemical products formed during cycling, and to gain insight into processes affecting capacity fading. While lithium peroxide is identified by 17O solid state NMR (ssNMR) as the predominant product in the first discharge in 1,2-dimethoxyethane (DME) based electrolytes, it reacts with the carbon cathode surface to form carbonate during the charging process. 13C ssNMR provides evidence for carbonate formation on the surface of the carbon cathode, the carbonate being removed at high charging voltages in the first cycle, but accumulating in later cycles. Small amounts of lithium hydroxide and formate are also detected in discharged cathodes and while the hydroxide formation is reversible, the formate persists and accumulates in the cathode upon further cycling. The results indicate that the rechargeability of the battery is limited by both the electrolyte and the carbon cathode stability. The utility of ssNMR spectroscopy in directly detecting product formation and decomposition within the battery is demonstrated, a necessary step in the assessment of new electrolytes, catalysts, and cathode materials for the development of a viable lithium–oxygen battery. PMID:24489976

2013-01-01

186

In-cell ¹³C NMR spectroscopy for the study of intrinsically disordered proteins.  

PubMed

A large number of proteins carry out their function in highly flexible and disordered states, lacking a well-defined 3D structure. These proteins, referred to as intrinsically disordered proteins (IDPs), are now in the spotlight of modern structural biology. Nuclear magnetic resonance (NMR) spectroscopy represents a unique tool for accessing atomic resolution information on IDPs in complex environments as whole cells, provided that the methods are optimized to their peculiar properties and to the characteristics of in-cell experiments. We describe procedures for the preparation of in-cell NMR samples, as well as for the setup of NMR experiments and their application to in-cell studies, using human ?-synuclein overexpressed in Escherichia coli as an example. The expressed protein is labeled with (13)C and (15)N stable isotopes to enable the direct recording of (13)C-detected NMR experiments optimized for the properties of IDPs. The entire procedure covers 24 h, including cell transformation, cell growth overnight, setup of the spectrometer and NMR experiment recording. PMID:25079425

Felli, Isabella C; Gonnelli, Leonardo; Pierattelli, Roberta

2014-09-01

187

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

188

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

189

Locust flight metabolism studied in vivo by 31 P NMR spectroscopy  

Microsoft Academic Search

Flight metabolism of locusts has been extensively studied, but biochemical and physiological methods have led to conflicting results. For this reason the non-invasive and non-destructive method of 31P NMR spectroscopy was used to study migratory locusts, Locusta migratoria, at rest and during flight.1.In the flight muscle of resting locusts the ratio of phosphoarginine to ATP was the same whether determined

Gerhard Wegener; Nicholas M. Bolas; André A. G. Thomas

1991-01-01

190

Study of complex formation between aluminum bromide and benzene by 27Al NMR spectroscopy  

Microsoft Academic Search

The reaction of aluminum bromide with benzene in n-hexane was studied by 27Al NMR spectroscopy in the temperature range from –80 to +20 °C. The formation of C6H6·Al2Br6 (1 : 2) complexes is accompanied by broadening of the resonance line with d 178. No peak splitting following a decrease in the temperature was observed but the temperature dependence of the

V. B. Murachev; A. I. Nesmelov

2001-01-01

191

Magnesium and Calcium Aluminate Liquids: In Situ High-Temperature 27Al NMR Spectroscopy  

Microsoft Academic Search

The use of high-temperature nuclear magnetic resonance (NMR) spectroscopy provides a means of investigating the structure of refractory aluminate liquids at temperatures up to 2500 K. Time-averaged structural information indicates that the average aluminum coordination for magnesium aluminate (MgAl_2O_4) liquid is slightly greater than for calcium aluminate (CaAl_2O_4) liquid and that in both liquids it is close to four. Ion

B. T. Poe; P. F. McMillan; B. Cote; D. Massiot; J. P. Coutures

1993-01-01

192

Mechanism of Aniline Methylation on Zeolite Catalysts Investigated by In Situ 13 C NMR Spectroscopy  

Microsoft Academic Search

The alkylation reaction of aniline with methanol on zeolites HY and CsOH\\/CsNaY was studied by in situ13C NMR spectroscopy under flow and batch conditions. Attention was focused on the identification of intermediates and on the determination of the formation mechanisms of N-methylaniline, N,N-dimethylaniline, and toluidines. To refine the main steps of the reaction, the transformations of the following individual compounds

I. I. Ivanova; E. B. Pomakhina; A. I. Rebrov; W. Wang; M. Hunger; J. Weitkamp

2003-01-01

193

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

194

Detection of Nitric Oxide and Superoxide Radical Anion by Electron Paramagnetic Resonance Spectroscopy from Cells using Spin Traps  

PubMed Central

Reactive nitrogen/oxygen species (ROS/RNS) at low concentrations play an important role in regulating cell function, signaling, and immune response but in unregulated concentrations are detrimental to cell viability1, 2. While living systems have evolved with endogenous and dietary antioxidant defense mechanisms to regulate ROS generation, ROS are produced continuously as natural by-products of normal metabolism of oxygen and can cause oxidative damage to biomolecules resulting in loss of protein function, DNA cleavage, or lipid peroxidation3, and ultimately to oxidative stress leading to cell injury or death4. Superoxide radical anion (O2•-) is the major precursor of some of the most highly oxidizing species known to exist in biological systems such as peroxynitrite and hydroxyl radical. The generation of O2•- signals the first sign of oxidative burst, and therefore, its detection and/or sequestration in biological systems is important. In this demonstration, O2•- was generated from polymorphonuclear neutrophils (PMNs). Through chemotactic stimulation with phorbol-12-myristate-13-acetate (PMA), PMN generates O2•- via activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase5. Nitric oxide (NO) synthase which comes in three isoforms, as inducible-, neuronal- and endothelial-NOS, or iNOS, nNOS or eNOS, respectively, catalyzes the conversion of L- arginine to L-citrulline, using NADPH to produce NO6. Here, we generated NO from endothelial cells. Under oxidative stress conditions, eNOS for example can switch from producing NO to O2•- in a process called uncoupling, which is believed to be caused by oxidation of heme7 or the co-factor, tetrahydrobiopterin (BH4)8. There are only few reliable methods for the detection of free radicals in biological systems but are limited by specificity and sensitivity. Spin trapping is commonly used for the identification of free radicals and involves the addition reaction of a radical to a spin trap forming a persistent spin adduct which can be detected by electron paramagnetic resonance (EPR) spectroscopy. The various radical adducts exhibit distinctive spectrum which can be used to identify the radicals being generated and can provide a wealth of information about the nature and kinetics of radical production9. The cyclic nitrones, 5,5-dimethyl-pyrroline-N-oxide, DMPO10, the phosphoryl-substituted DEPMPO11, and the ester-substituted, EMPO12 and BMPO13, have been widely employed as spin traps--the latter spin traps exhibiting longer half-lives for O2•- adduct. Iron (II)-N-methyl-D-glucamine dithiocarbamate, Fe(MGD)2 is commonly used to trap NO due to high rate of adduct formation and the high stability of the spin adduct14. PMID:22929836

Gopalakrishnan, Bhavani; Nash, Kevin M.; Velayutham, Murugesan; Villamena, Frederick A.

2012-01-01

195

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. PMID:21850648

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

2011-01-01

196

Insights into reaction mechanisms in heterogeneous catalysis revealed by in situ NMR spectroscopy.  

PubMed

This tutorial review intends to show the possibilities of in situ solid state NMR spectroscopy in the elucidation of reaction mechanisms and the nature of the active sites in heterogeneous catalysis. After a brief overview of the more usual experimental devices used for in situ solid state NMR spectroscopy measurements, some examples of applications taken from the recent literature will be presented. It will be shown that in situ NMR spectroscopy allows: (i) the identification of stable intermediates and transient species using indirect methods, (ii) to prove shape selectivity in zeolites, (iii) the study of reaction kinetics, and (iv) the determination of the nature and the role played by the active sites in a catalytic reaction. The approaches and methodology used to get this information will be illustrated here summarizing the most relevant contributions on the investigation of the mechanisms of a series of reactions of industrial interest: aromatization of alkanes on bifunctional catalysts, carbonylation reaction of methanol with carbon monoxide, ethylbenzene disproportionation, and the Beckmann rearrangement reaction. Special attention is paid to the research carried out on the role played by carbenium ions and alkoxy as intermediate species in the transformation of hydrocarbon molecules on solid acid catalysts. PMID:20976339

Blasco, Teresa

2010-12-01

197

Insights into the structure of cutin and cutan from Agave americana leaf cuticle using HRMAS NMR spectroscopy  

Microsoft Academic Search

The structure of cutan, and a cutin\\/cutan mixture from the Agave americana leaf cuticle is herein described by use of the technique of one and two-dimensional high-resolution magic angle spinning (HRMAS) NMR spectroscopy, with added information from solid-state 13C cross-polarization magic angle spinning (CPMAS) and Bloch decay NMR spectroscopy. Cutin in the cutin\\/cutan mixture is found to contain ester functionalities,

Ashish P. Deshmukh; André J. Simpson; Christopher M. Hadad; Patrick G. Hatcher

2005-01-01

198

Structure-Independent Analysis of the Breadth of the Positional Distribution of Disordered Groups in Macromolecules from Order Parameters for Long Variable-Length Vectors using NMR Paramagnetic Relaxation Enhancement  

PubMed Central

Quantitative information regarding structurally disordered groups is crucial for a complete understanding of the relationship between structure, dynamics and function in biological macromolecules. Experimental analysis, however, of the positional distribution of disordered groups in the macromolecular frame is extremely difficult. While NMR order parameters, S2, for fixed-length bond vectors such as N-H and C-H are commonly used for investigations of conformational dynamics of macromolecules, these order parameters only provide angular information about internal motions and are totally insensitive to translational motions. Although analysis of S2 for bond vectors permit identification of disordered groups in macromolecules, this type of order parameter cannot provide any information about the distribution radii of disordered groups. Here we describe an NMR approach to directly determine the distribution radius of a disordered group independent of any structural knowledge. This approach makes use of order parameters for long variable-length vectors (including proton-paramagnetic center and proton-proton vectors) between a disordered group and a rigid portion of the macromolecule. We demonstrate the application of this formalism to paramagnetic relaxation enhancement vectors. In addition, the potential utility of the same formalism to 1H-1H cross-relaxation rates is considered as an alternative approach for analyzing the breadth of the positional distribution of disordered groups. PMID:20795737

Iwahara, Junji; Clore, G. Marius

2010-01-01

199

Probing Structure and Dynamics of Protein Assemblies by Magic Angle Spinning NMR Spectroscopy  

PubMed Central

CONSPECTUS In living organisms, biological molecules often organize into multi-component complexes. Such assemblies consist of various proteins and carry out essential functions, ranging from cell division, transport, and energy transduction to catalysis, signaling, and viral infectivity. To understand the biological functions of these assemblies, in both healthy and disease states, researchers need to study their three-dimensional architecture and molecular dynamics. To date, the large size, the lack of inherent long-range order, and insolubility have made atomic-resolution studies of many protein assemblies challenging or impractical using traditional structural biology methods such as X-ray diffraction and solution NMR spectroscopy. In the past ten years, we have focused our work on the development and application of magic angle spinning solid-state NMR (MAS NMR) methods to characterize large protein assemblies at atomic-level resolution. In this Account, we discuss the rapid progress in the field of MAS NMR spectroscopy, citing work from our laboratory and others on methodological developments that have facilitated the in-depth analysis of biologically important protein assemblies. We emphasize techniques that yield enhanced sensitivity and resolution, such as fast MAS (spinning frequencies of 40 kHz and above) and non-uniform sampling protocols for data acquisition and processing. We also discuss the experiments for gaining distance restraints and for recoupling anisotropic tensorial interactions under fast MAS conditions. We give an overview of sample preparation approaches when working with protein assemblies. Following the overview of contemporary MAS NMR methods, we present case studies into the structure and dynamics of two classes of biological systems under investigation in our laboratory. We will first turn our attention to cytoskeletal microtubule motor proteins including mammalian dynactin and dynein light chain 8. We will then discuss protein assemblies from the HIV-1 retrovirus. PMID:23402263

Yan, Si; Suiter, Christopher L.; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana

2013-01-01

200

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

201

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

NASA Astrophysics Data System (ADS)

In order to study to what extent mechanisms of molecular motion can be unambiguously revealed by 2H NMR spectroscopy, 2H spectra for proteins (chicken villin protein headpiece HP36, selectively methyl-deuterated at leucine-69, C? D3) and binary systems of high viscosity (benzene-d6 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 2H 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 2H lineshapes. For benzene-d6 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.

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

2012-06-01

202

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

203

Metabolomic by 1H NMR spectroscopy differentiates "Fiano di Avellino" white wines obtained with different yeast strains.  

PubMed

We employed (1)H NMR spectroscopy to examine the molecular profile of a white "Fiano di Avellino" wine obtained through fermentation by either a commercial or a selected autochthonous Saccharomyces cerevisiae yeast starter. The latter was isolated from the same grape variety used in the wine-making process in order to strengthen the relationship between wine molecular quality and its geographical origin. (1)H NMR spectra, where water and ethanol signals were suppressed by a presaturated T1-edited NMR pulse sequence, allowed for definition of the metabolic content of the two differently treated wines. Elaboration of NMR spectral data by multivariate statistical analyses showed that the two different yeasts led to significant diversity in the wine metabolomes. Our results indicate that metabolomics by (1)H NMR spectroscopy combined with multivariate statistical analysis enables wine differentiation as a function of yeast species and other wine-making factors, thereby contributing to objectively relate wine quality to the terroir. PMID:24117410

Mazzei, Pierluigi; Spaccini, Riccardo; Francesca, Nicola; Moschetti, Giancarlo; Piccolo, Alessandro

2013-11-13

204

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. PMID:23552326

2013-01-01

205

NMR spectroscopy as a tool to close the gap on metabolite characterization under MIST.  

PubMed

Withdrawals from the market due to unforeseen adverse events have triggered changes in the way therapeutics are discovered and developed. This has resulted in an emphasis on truly understanding the efficacy and toxicity profile of new chemical entities (NCE) and the contributions of their metabolites to on-target pharmacology and off-target receptor-mediated toxicology. Members of the pharmaceutical industry, scientific community and regulatory agencies have held dialogues with respect to metabolites in safety testing (MIST); and both the US FDA and International Conference on Harmonisation have issued guidances with respect to when and how to characterize metabolites for human safety testing. This review provides a brief overview of NMR spectroscopy as applied to the structure elucidation and quantification of drug metabolites within the drug discovery and development process. It covers advances in this technique, including cryogenic cooling of detection circuitry for enhanced sensitivity, hyphenated LC-NMR techniques, improved dynamic range through new solvent-suppression pulse sequences and quantitation. These applications add to the already diverse NMR toolkit and further anchor NMR as a technique that is directly applicable to meeting the requirements of MIST guidelines. PMID:21083239

Caceres-Cortes, Janet; Reily, Michael D

2010-07-01

206

?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

207

Parametric spectrum analysis of 2D NMR signals. Application to in Vivo J spectroscopy  

NASA Astrophysics Data System (ADS)

Parametric modeling techniques for spectrum analysis, based on the linear prediction principle, have previously been proposed to process NMR data. In this paper, they are tested on different practical NMR signals, and especially on in vivo 2D NMR spectroscopy data. The linear prediction version of the maximum entropy method, using AR modeling, and the Prony method are outlined with some considerations about the choice of the AR algorithm. Then simulation and experimental results obtained with the Prony method are presented and compared with those obtained with classical 2D Fourier transform processing. The data processed here result from homonuclear 2D J-resolved spectroscopy experiments performed to measure the spin-spin coupling constants between the three phosphorus nuclei of ATP in the rat brain. The parametric techniques (especially the Prony method) applied in both dimensions yield increased resolution and sensitivity and their ability to process limited data allows the total acquisition time to be reduced without loss of resolution. Although the noise may damage the performances, the results obtained here, on in vivo 2D data, are quite encouraging.

Luthon, F.; Blanpain, R.; Decorps, M.; Albrand, J. P.

208

Qualitative and quantitative control of carbonated cola beverages using ¹H NMR spectroscopy.  

PubMed

¹H Nuclear magnetic resonance (NMR) spectroscopy (400 MHz) was used in the context of food surveillance to develop a reliable analytical tool to differentiate brands of cola beverages and to quantify selected constituents of the soft drinks. The preparation of the samples required only degassing and addition of 0.1% of TSP in D?O for locking and referencing followed by adjustment of pH to 4.5. The NMR spectra obtained can be considered as "fingerprints" and were analyzed by principal component analysis (PCA). Clusters from colas of the same brand were observed, and significant differences between premium and discount brands were found. The quantification of caffeine, acesulfame-K, aspartame, cyclamate, benzoate, hydroxymethylfurfural (HMF), sulfite ammonia caramel (E 150D), and vanillin was simultaneously possible using external calibration curves and applying TSP as internal standard. Limits of detection for caffeine, aspartame, acesulfame-K, and benzoate were 1.7, 3.5, 0.8, and 1.0 mg/L, respectively. Hence, NMR spectroscopy combined with chemometrics is an efficient tool for simultaneous identification of soft drinks and quantification of selected constituents. PMID:22356160

Maes, Pauline; Monakhova, Yulia B; Kuballa, Thomas; Reusch, Helmut; Lachenmeier, Dirk W

2012-03-21

209

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. PMID:23181936

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

2013-01-01

210

Structure of lysozyme dissolved in neat organic solvents as assessed by NMR and CD spectroscopies  

SciTech Connect

The structure of the model protein hen egg-white lysozyme dissolved in water and in five neat organic solvents (ethylene glycol, methanol, dimethylsufloxide (DMSO), formamide, and dimethylformamide (DMF)) has been examined by means of {sup 1}H NMR and circular dichroism (CD) spectroscopies. The NMR spectra of lysozyme reveal the lack of a defined tertiary structure in all five organic solvents, although the examination of line widths suggests the possibility of some ordered structure in ethylene glycol and in methanol. The near-UV CD spectra of the protein suggest no tertiary structure in lysozyme dissolved in DMSO, formamide, and DMF, while a distinctive tertiary structure is seen in ethylene glycol and a drastically changed one in methanol. A highly developed secondary structure was observed by far-UV CD in ethylene glycol and methanol; interestingly, the {alpha}-helix content of the protein in both was greater than in water, while the {beta}-structure content was lower.

Knubovets, T.; Klibanov, A.M. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Chemistry] [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Chemistry; Osterhout, J.J. [Rowland Inst. for Science, Cambridge, MA (United States)] [Rowland Inst. for Science, Cambridge, MA (United States)

1999-04-20

211

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 ±71.2 ± 1 MHz, corresponding to an electric field gradient of ±1.49 atomic units at the copper site, and an asymmetry parameter of approximately 0.2. Quantum chemical calculations employing second order Møller-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. PMID:19746904

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

212

Conformational problem of alkanes in liquid crystals by NMR spectroscopy: a mini-review.  

PubMed

Recent discoveries of the role of alkane flexibility in determining liquid-crystal behaviour are surveyed. With the impetus for understanding the alkane conformational problem established, recent model dependent (1)H NMR work on the topic will be reviewed where progress is made but the need to circumvent models eventually becomes evident. A closer look at the rigid basic units of alkanes will provide the way forward where it is shown that the orientational ordering and anisotropic potentials of these molecules dissolved in liquid crystals scale with each other. Once this relationship is established, a series of works using anisotropic and isotropic (1)H NMR spectroscopy to study alkane conformational statistics will be covered, wherein the influence of the gas, isotropic condensed and anisotropic condensed phases will be described. PMID:25142124

Weber, Adrian C J; Chen, Daniel H J

2014-10-01

213

Characterization of Intrinsically Disordered Prostate Associated Gene (PAGE5) at Single Residue Resolution by NMR Spectroscopy  

PubMed Central

Background The Cancer-Testis antigens (CTA) are proteins expressed in human germ line and certain cancer cells. CTAs form a large gene family, representing 10% of X-chromosomal genes. They have high potential for cancer-specific immunotherapy. However, their biological functions are currently unknown. Prostate associated genes (PAGE) are characterized as CTAs. PAGE5 is one of six proteins belonging to this protein family, also called CT16. Methodology/Principal findings In this study we show, using bioinformatics, chromatographic and solution state NMR spectroscopic methods, that PAGE5 is an intrinsically disordered protein (IDP). Conclusion/Significance The study stands out as the first time structural characterization of the PAGE family protein and introduces how solution state NMR spectroscopy can be effectively utilized for identification of molecular recognition regions (MoRF) in IDPs, known often as transiently populated secondary structures. PMID:22073178

Hellman, Maarit; Tossavainen, Helena; Rappu, Pekka; Heino, Jyrki; Permi, Perttu

2011-01-01

214

NMR spectroscopy of hyperpolarized ^129Xe at high fields: Maintaining spin polarization after optical pumping.  

NASA Astrophysics Data System (ADS)

Spin-polarized ^129Xe has become an invaluable tool in nuclear magnetic resonance research, with applications ranging from medical imaging to high-resolution spectroscopy. High-field NMR studies using hyperpolarized xenon as a spectroscopic probe benefit from the high signal-to-noise ratios and large chemical shifts typical of optically-pumped noble gases. The experimental sensitivity is ultimately determined by the absolute polarization of the xenon in the sample, which can be substantially decreased during purification and transfer. NMR of xenon at high fields (9.4 Tesla) will be discussed, and potential mechanisms of spin relaxation during the distillation, storage(N. N. Kuzma, B. Patton, K. Raman, and W. Happer, Phys. Rev. Lett. 88), 147602 (2002)., and delivery of hyperpolarized xenon will be analyzed.

Patton, Brian; Kuzma, Nicholas N.; Lisitza, Natalia V.; Happer, William

2003-05-01

215

Application of /sup 31/P-NMR spectroscopy to the study of striated muscle metabolism  

SciTech Connect

This review presents the principles and limitations of phosphorus nuclear magnetic resonance (/sup 31/P-NMR) spectroscopy as applied to the study of striated muscle metabolism. Application of the techniques discussed include noninvasive measurement of high-energy phosphate, intracellular pH, intracellular free Mg/sup 2 +/, and metabolite compartmentation. In perfused cat biceps (fast-twitch) muscles, but not in soleus (slow-twitch), NMR spectra indicate a substantially lower (1 mM) free inorganic phosphate level than when measured chemically (6 mM). In addition, saturation and inversion spin-transfer methods that enable direct measurement of the unidirectional fluxes through creatine kinase are described. In perfused cat biceps muscle, results suggest that this enzyme and its substrates are in simple chemical equilibrium.

Meyer, R.A.; Kushmerick, M.J.; Brown, T.R.

1982-01-01

216

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

217

Recent advances in solid-state NMR spectroscopy of quadrupolar nuclei.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy of quadrupolar nuclei (i.e., those with a spin quantum number I > 1/2) has always been viewed as "difficult" owing to the presence of an anisotropic broadening arising from the interaction of the nuclear electric quadrupole moment with the electric field gradient. This quadrupolar interaction can be considerable, resulting in broadening of the spectral resonances often over many MHz. Furthermore, magic-angle spinning (MAS), a conventional approach for increasing the resolution in solid-state NMR, is often unable to remove the broadening completely and high-resolution spectra are generally not obtained. Despite the vast amount of information contained in the anisotropic linewidths and lineshapes, the resolution and sensitivity challenges have, until recently, somewhat limited the application of solid-state NMR for quadrupolar nuclei. In general, structural information, such as that obtained through recoupling techniques or from two-dimensional correlation spectroscopy, is much more difficult to extract easily and accurately. However, recent advances in magnet design, probe hardware and pulse sequence development have significantly improved the ease with which quadrupolar spins can be studied and high-resolution spectra can be obtained, and recent applications are beginning to exploit the wealth of information available. In this discussion, we highlight just a few of the recent developments in this area, including new state-of-the art correlation experiments, the expanding study of nuclei with low gyromagnetic ratio, gamma, the increasing application of first-principles calculations in the solid state, and methods which exploit the quadrupolar broadening to provide information on dynamics. Whilst not a complete review, it is hoped that this brief overview of some of the more exciting recent developments can provide insight into the challenges, and the rewards, involved in the NMR study of quadrupolar nuclei. PMID:19652823

Ashbrook, Sharon E

2009-08-28

218

Solid-state Ru-99 NMR spectroscopy: a useful tool for characterizing prototypal diamagnetic ruthenium compounds.  

PubMed

The feasibility of (99)Ru NMR spectroscopy as a tool to characterize solid compounds is demonstrated. Results of the first solid-state (99)Ru NMR investigation of diamagnetic compounds are presented for Ru(NH(3))(6)Cl(2), K(4)Ru(CN)(6). xH(2)O (x = 0, 3), LaKRu(CN)(6), and Ru(3)(CO)(12). The sensitivity of the ruthenium magnetic shielding tensor to subtle changes in the local structure about the ruthenium nucleus is highlighted by comparing the (99)Ru isotropic chemical shift of Ru(NH(3))(6)Cl(2) in aqueous solutions and in the solid state. The narrow isotropic (99)Ru NMR peak observed for solid Ru(NH(3))(6)Cl(2) indicates that this compound is an ideal secondary reference sample for solid-state (99)Ru NMR studies. The isotropic (99)Ru chemical shift, (99)Ru nuclear quadrupolar coupling constant, C(Q), and quadrupolar asymmetry parameter of K(4)Ru(CN)(6). xH(2)O (x = 0, 3) are shown to be sensitive to x. For Ru(3)(CO)(12), the magnetic shielding tensors of each of the three nonequivalent Ru nuclei have spans of 1300-1400 ppm, and the (99)Ru C(Q) values are also similar, 1.36-1.85 MHz, and are surprisingly small given that (99)Ru has a moderate nuclear quadrupole moment. Information about the relative orientation of the Ru magnetic shielding and electric field gradient tensors has been determined for Ru(3)(CO)(12) from experimental (99)Ru NMR spectra as well as quantum chemical calculations. PMID:15339183

Ooms, Kristopher J; Wasylishen, Roderick E

2004-09-01

219

Microfabricated inserts for magic angle coil spinning (MACS) wireless NMR spectroscopy.  

PubMed

This article describes the development and testing of the first automatically microfabricated probes to be used in conjunction with the magic angle coil spinning (MACS) NMR technique. NMR spectroscopy is a versatile technique for a large range of applications, but its intrinsically low sensitivity poses significant difficulties in analyzing mass- and volume-limited samples. The combination of microfabrication technology and MACS addresses several well-known NMR issues in a concerted manner for the first time: (i) reproducible wafer-scale fabrication of the first-in-kind on-chip LC microresonator for inductive coupling of the NMR signal and reliable exploitation of MACS capabilities; (ii) improving the sensitivity and the spectral resolution by simultaneous spinning the detection microcoil together with the sample at the "magic angle" of 54.74° with respect to the direction of the magnetic field (magic angle spinning - MAS), accompanied by the wireless signal transmission between the microcoil and the primary circuit of the NMR spectrometer; (iii) given the high spinning rates (tens of kHz) involved in the MAS methodology, the microfabricated inserts exhibit a clear kinematic advantage over their previously demonstrated counterparts due to the inherent capability to produce small radius cylindrical geometries, thus tremendously reducing the mechanical stress and tearing forces on the sample. In order to demonstrate the versatility of the microfabrication technology, we have designed MACS probes for various Larmor frequencies (194, 500 and 700 MHz) testing several samples such as water, Drosophila pupae, adamantane solid and LiCl at different magic angle spinning speeds. PMID:22936994

Badilita, Vlad; Fassbender, Birgit; Kratt, Kai; Wong, Alan; Bonhomme, Christian; Sakellariou, Dimitris; Korvink, Jan G; Wallrabe, Ulrike

2012-01-01

220

Microfabricated Inserts for Magic Angle Coil Spinning (MACS) Wireless NMR Spectroscopy  

PubMed Central

This article describes the development and testing of the first automatically microfabricated probes to be used in conjunction with the magic angle coil spinning (MACS) NMR technique. NMR spectroscopy is a versatile technique for a large range of applications, but its intrinsically low sensitivity poses significant difficulties in analyzing mass- and volume-limited samples. The combination of microfabrication technology and MACS addresses several well-known NMR issues in a concerted manner for the first time: (i) reproducible wafer-scale fabrication of the first-in-kind on-chip LC microresonator for inductive coupling of the NMR signal and reliable exploitation of MACS capabilities; (ii) improving the sensitivity and the spectral resolution by simultaneous spinning the detection microcoil together with the sample at the “magic angle” of 54.74° with respect to the direction of the magnetic field (magic angle spinning – MAS), accompanied by the wireless signal transmission between the microcoil and the primary circuit of the NMR spectrometer; (iii) given the high spinning rates (tens of kHz) involved in the MAS methodology, the microfabricated inserts exhibit a clear kinematic advantage over their previously demonstrated counterparts due to the inherent capability to produce small radius cylindrical geometries, thus tremendously reducing the mechanical stress and tearing forces on the sample. In order to demonstrate the versatility of the microfabrication technology, we have designed MACS probes for various Larmor frequencies (194, 500 and 700 MHz) testing several samples such as water, Drosophila pupae, adamantane solid and LiCl at different magic angle spinning speeds. PMID:22936994

Badilita, Vlad; Fassbender, Birgit; Kratt, Kai; Wong, Alan; Bonhomme, Christian; Sakellariou, Dimitris; Korvink, Jan G.; Wallrabe, Ulrike

2012-01-01

221

Investigation on origin of Z{sub 1/2} center in SiC by deep level transient spectroscopy and electron paramagnetic resonance  

SciTech Connect

The Z{sub 1/2} center in n-type 4H-SiC epilayers-a dominant deep level limiting the carrier lifetime-has been investigated. Using capacitance versus voltage (C-V) measurements and deep level transient spectroscopy (DLTS), we show that the Z{sub 1/2} center is responsible for the carrier compensation in n-type 4H-SiC epilayers irradiated by low-energy (250 keV) electrons. The concentration of the Z{sub 1/2} defect obtained by C-V and DLTS correlates well with that of the carbon vacancy (V{sub C}) determined by electron paramagnetic resonance, suggesting that the Z{sub 1/2} deep level originates from V{sub C}.

Kawahara, Koutarou; Suda, Jun; Kimoto, Tsunenobu [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510 (Japan)] [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510 (Japan); Thang Trinh, Xuan; Tien Son, Nguyen; Janzen, Erik [Department of Physics Chemistry and Biology, Linkoeping University, 581 83 Linkoeping (Sweden)] [Department of Physics Chemistry and Biology, Linkoeping University, 581 83 Linkoeping (Sweden)

2013-03-18

222

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

223

Study of amino acid coordination to chromium(III) by deuterium NMR spectroscopy  

Microsoft Academic Search

Interest in monodentate amino acid coordination to chromium(III) results in the synthesis and characterization of the Cr(III)-nicotinic acid complexes and the \\/sup +\\/-carboxylato-..mu..-hydroxo Cr(III) complexes. A relatively stable Cr(III) complex containing carboxyl-bound nicotinic acid, trans-(Cr(1,3-pn)â(nic-O)â) Cl (where 1,3-pn = 1,3-propanediamine, and nic-O = nicotinate with a deuterium label on the 2-carbon), was synthesized and then characterized by deuterium NMR spectroscopy.

1986-01-01

224

Impact of Hydrophilic Surfaces on Interfacial Water Dynamics Probed with NMR Spectroscopy  

PubMed Central

In suspensions of Nafion beads and of cationic gel beads, NMR spectroscopy showed two water–proton resonances, one representing intimate water layers next to the polymer surface, the other corresponding to water lying beyond. Both resonances show notably shorter spin–lattice relaxation times (T1) and smaller self-diffusion coefficients (D) indicating slower dynamics than bulk water. These findings confirm the existence of highly restricted water layers adsorbed onto hydrophilic surfaces and dynamically stable water beyond the first hydration layers. Thus, aqueous regions on the order of micrometers are dynamically different from bulk water. PMID:22003430

Yoo, Hyok; Paranji, Rajan

2011-01-01

225

Application of nmr spectroscopy to determine the thermodynamic characteristics of water bound to OX-50 nanosilica  

NASA Astrophysics Data System (ADS)

We have used low-temperature 1H NMR spectroscopy to determine the thermodynamic characteristics of water bound to OX-50 nanosilica (SBET ? 50 m2/g) in different media: aqueous, air, chloroform medium, and gaseous methane. We demonstrate the difference between the hydration parameters of silica OX-50 on going from an aqueous suspension to a hydrated powder. We present the water cluster size distributions in the studied systems, calculated from the Gibbs-Thomson equation. We found that the average water cluster size in suspension is considerably larger than the cluster sizes in hydrated powders.

Turov, V. V.; Gun'ko, V. M.; Gaishun, V. E.; Kosenok, Ya. A.; Golovan, A. P.

2010-09-01

226

Electrical and electron paramagnetic resonance spectroscopy characterization of Mn-doped nanostructured TiO2 for capacitor applications  

NASA Astrophysics Data System (ADS)

Nanostructured TiO2 has shown promise as a dielectric material for high energy density ceramic capacitors because of its high dielectric breakdown strength and dielectric constant. Strategies to increase the insulation resistance or to reduce the leakage current of TiO2 include doping with transition metal ions. It is shown that Mn doping followed by an appropriate thermal treatment increases the grain boundary resistivity significantly and lowers the dielectric loss. Electrical measurements along with electron paramagnetic resonance and scanning electron microscopy of Mn-doped nanoscopic TiO2 demonstrate that sintering at 900 °C leads to optimal electrical properties that are correlated with a non-uniform distribution of dopant ions, concentrated at the grain boundaries. Nanostructured TiO2 dielectrics with improved insulation resistance are promising for the development of higher energy density capacitors.

Vazquez-Reina, Rafael; Chao, Sheng; Petrovsky, Vladimir; Dogan, Fatih; Greenbaum, Steven

2012-07-01

227

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

228

Chemistry of paramagnetic and diamagnetic contrast agents for Magnetic Resonance Imaging and Spectroscopy pH responsive contrast agents.  

PubMed

We provide a brief overview of the chemistry and most relevant properties of paramagnetic and diamagnetic contrast agents (CAs) for Magnetic Resonance Imaging and Magnetic Resonance Spectroscopic Imaging. Paramagnetic CAs for MRI consist mainly of Gd(III) complexes from linear or macrocyclic polyaminopolycarboxylates. These agents reduce, the relaxation times T(1) and T(2) of the water protons in a concentration dependent manner, increasing selectively MRI contrast in those regions in which they accumulate. In most instances they provide anatomical information on the localization of lesions and in some specific cases they may allow to estimate some physiological properties of tissues including mainly vascular performance. Because of its ability to discriminate easily between normal and diseased tissue, extracellular pH (pH(e)) has been added recently, to the battery of variables amenable to MRI investigation. A variety of Gd(III) containing macrocycles sensitive to pH, endogenous or exogenous polypeptides or even liposomes have been investigated for this purpose, using the pH dependence of their relaxivity or magnetization transfer rate constant (chemical exchange saturation transfer, CEST). Many environmental circumstances in addition to pH affect, however, relaxivity or magnetization transfer rate constants of these agents, making the results of pH measurements by MRI difficult to interpret. To overcome these limitations, our laboratory synthesized and developed a novel series of diamagnetic CAs for Magnetic Resonance Spectroscopic Imaging, a new family of monomeric and dimeric imidazolic derivatives able to provide unambiguous measurements of pH(e), independent of water relaxivity, diffusion or exchange. PMID:18455343

Pérez-Mayoral, Elena; Negri, Viviana; Soler-Padrós, Jordi; Cerdán, Sebastián; Ballesteros, Paloma

2008-09-01

229

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

230

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

231

Oil droplet size determination in complex flavor delivery systems by diffusion NMR spectroscopy.  

PubMed

Droplet size distribution of flavor oils in two different solid flavor delivery systems were determined with pulsed field gradient NMR spectroscopy: yeast encapsulation system, a spray dried flavor encapsulation system based on empty yeast cells, and glassy encapsulation system, an extruded solid water soluble carbohydrate delivery system. The oil droplet sizes are limited by the yeast cell walls in the yeast encapsulation system and the size distribution is unimodal according to images from transmission electron microscopy. The droplet size determination with diffusion NMR is based on the Murday and Cotts theory of restricted diffusion of liquids in geometrical confinements. Good fits of the diffusion data could be obtained by applying a unimodal, log-normal size distribution model and average droplet sizes of about 2 ?m were found that correspond approximately to the inner diameter of the yeast cells. Scanning electron microscopy images showed a multimodal droplet size distribution in the glassy extruded delivery systems. To fit the NMR data a bimodal log-normal distribution function with five independent fitting parameters was implemented that yielded consistent and robust results. The two size populations were found in the micron and sub-micron range, respectively. The method was sufficiently accurate to depict variation of droplet size distributions in glassy encapsulation systems of different formulation. PMID:21316700

Fieber, Wolfgang; Hafner, Valeria; Normand, Valéry

2011-04-15

232

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. PMID:20028318

Tikhonova, Irina G.; Costanzi, Stefano

2009-01-01

233

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

SciTech Connect

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 {sup 1}H-{sup 15}N correlation spectra of a {sup 15}N-labelled RTP.C110S mutant upon the addition of a 21 base pair symmetrical DNA binding site. Assignment of the {sup 1}H-{sup 15}N correlations was achieved using a suite of triple resonance NMR experiments with {sup 15}N,{sup 13}C,70% {sup 2}H enriched protein recorded at 800 MHz and using TROSY pulse sequences. Perturbations to {sup 1}H-{sup 15}N spectra revealed that the N-termini, {alpha}3-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.

Hastings, Adam F. [School of Molecular and Microbial Biosciences, University of Sydney, Sydney, NSW 2006 (Australia); Otting, Gottfried [Research School of Chemistry, Australian National University, Canberra, ACT (Australia); Folmer, Rutger H.A. [Structural Chemistry Laboratory, AstraZeneca R and D, S-431 83, Moelndal (Sweden); Duggin, Iain G. [School of Molecular and Microbial Biosciences, University of Sydney, Sydney, NSW 2006 (Australia); Wake, R. Gerry [School of Molecular and Microbial Biosciences, University of Sydney, Sydney, NSW 2006 (Australia); Wilce, Matthew C.J. [Biochemistry and Molecular Biology, Monash University, Melbourne, Vic. 3800 (Australia); Wilce, Jacqueline A. [Biochemistry and Molecular Biology, Monash University, Melbourne, Vic. 3800 (Australia)]. E-mail: Jackie.Wilce@med.monash.edu.au

2005-09-23

234

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

235

Analysis of trivalent cation complexation to functionalized mesoporous silica using solid-state NMR spectroscopy.  

PubMed

Functionalized mesoporous silica has applications in separations science, catalysis, and sensors. In this work, we studied the fundamental interactions of trivalent cations with functionalized mesoporous silica. We contacted trivalent cations of varying ionic radii with N-[5-(trimethoxysilyl)-2-aza-1-oxopentyl]caprolactam functionalized mesoporous silica with the aim of probing the binding mechanism of the metal to the surface of the solid. We studied the functionalized silica using solid-state nuclear magnetic resonance (NMR) spectroscopy before and after contact with the metals of interest. We collected NMR spectra of the various metals, as well as of (29)Si and (13)C to probe the silica substrate and the ligand properties, respectively. The NMR spectra indicate that the metals bind to the functionalized silica via two mechanisms. Aluminum sorbed to both the silica and the ligand, but with different coordination for each. Scandium also sorbed to both the silica and the ligand, and unlike the aluminum, had the same coordination number. Additionally, the functionalized silica was susceptible to acid hydrolysis and two primary mechanisms of degradation were observed: detachment from the silica surface and opening of the seven-membered ring in the ligand. Opening of the seven-membered ring may be beneficial in that it decreases steric hindrance of the molecule for binding. PMID:25265419

Shusterman, Jennifer; Mason, Harris; Bruchet, Anthony; Zavarin, Mavrik; Kersting, Annie B; Nitsche, Heino

2014-10-22

236

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

237

Enhanced sensitivity by nonuniform sampling enables multidimensional MAS NMR spectroscopy of protein assemblies.  

PubMed

We report dramatic sensitivity enhancements in multidimensional MAS NMR spectra by the use of nonuniform sampling (NUS) and introduce maximum entropy interpolation (MINT) processing that assures the linearity between the time and frequency domains of the NUS acquired data sets. A systematic analysis of sensitivity and resolution in 2D and 3D NUS spectra reveals that with NUS, at least 1.5- to 2-fold sensitivity enhancement can be attained in each indirect dimension without compromising the spectral resolution. These enhancements are similar to or higher than those attained by the newest-generation commercial cryogenic probes. We explore the benefits of this NUS/MaxEnt approach in proteins and protein assemblies using 1-73-(U-(13)C,(15)N)/74-108-(U-(15)N) Escherichia coli thioredoxin reassembly. We demonstrate that in thioredoxin reassembly, NUS permits acquisition of high-quality 3D-NCACX spectra, which are inaccessible with conventional sampling due to prohibitively long experiment times. Of critical importance, issues that hinder NUS-based SNR enhancement in 3D-NMR of liquids are mitigated in the study of solid samples in which theoretical enhancements on the order of 3-4 fold are accessible by compounding the NUS-based SNR enhancement of each indirect dimension. NUS/MINT is anticipated to be widely applicable and advantageous for multidimensional heteronuclear MAS NMR spectroscopy of proteins, protein assemblies, and other biological systems. PMID:22667827

Paramasivam, Sivakumar; Suiter, Christopher L; Hou, Guangjin; Sun, Shangjin; Palmer, Melissa; Hoch, Jeffrey C; Rovnyak, David; Polenova, Tatyana

2012-06-28

238

Investigation of Chiral Molecular Micelles by NMR Spectroscopy and Molecular Dynamics Simulation  

PubMed Central

NMR spectroscopy and molecular dynamics (MD) simulation analyses of the chiral molecular micelles poly-(sodium undecyl-(L,L)-leucine-valine) (poly-SULV) and poly-(sodium undecyl-(L,L)- valine-leucine) (poly-(SUVL)) are reported. Both molecular micelles are used as chiral selectors in electrokinetic chromatography and each consists of covalently linked surfactant chains with chiral dipeptide headgroups. To provide experimental support for the structures from MD simulations, NOESY spectra were used to identify protons in close spatial proximity. Results from the NOESY analyses were then compared to radial distribution functions from MD simulations. In addition, the hydrodynamic radii of both molecular micelles were calculated from NMR-derived diffusion coefficients. Corresponding radii from the MD simulations were found to be in agreement with these experimental results. NMR diffusion experiments were also used to measure association constants for polar and non-polar binaphthyl analytes binding to both molecular micelles. Poly(SUVL) was found to bind the non-polar analyte enantiomers more strongly, while the more polar analyte enantiomers interacted more strongly with poly(SULV). MD simulations in tum showed that poly(SUL V) had a more open structure that gave greater access for water molecules to the dipeptide headgroup region. PMID:23991355

Morris, Kevin F.; Billiot, Eugene J.; Billiot, Fereshteh H.; Lipkowitz, Kenny B.; Southerland, William M.; Fang, Yayin

2013-01-01

239

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

240

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

241

(1) H and DOSY NMR spectroscopy analysis of Ligusticum porteri rhizome extracts.  

PubMed

The presence of dimeric phthalides and other constituents in extracts of the vegetal species Ligusticum porteri was established by NMR spectroscopy. In comparative qualitative (1) H NMR analyses of acetone extracts of rhizomes from fresh and dried L. porteri samples, we found that the dimeric phthalides tokinolide B (3), diligustilide (4) and riligustilide (5) were naturally produced by the plant and not post-harvest products. We also obtained DOSY (1) H NMR data that provided both virtual separation and structural information for the phthalides present in a dry acetone extract of L. porteri. In addition, we developed a protocol for the quantification of dimeric phthalides, which is performed by calculating the relative ratio of the peak area of selected proton signals for some compounds with respect to the known signal of the internal standard, 4-dimethylaminopyridine. The protocol allows the rapid and direct quantification of dimeric phthalides and others constituents in fresh L. porteri rhizomes. Copyright © 2011 John Wiley & Sons, Ltd. PMID:21761449

León, Alejandra; Chávez, María Isabel; Delgado, Guillermo

2011-07-14

242

Moving NMR  

NASA Astrophysics Data System (ADS)

Initiated by the use of NMR for well logging, portable NMR instruments are being developed for a variety of novel applications in materials testing and process analysis and control. Open sensors enable non-destructive testing of large objects, and small, cup-size magnets become available for high throughput analysis by NMR relaxation and spectroscopy. Some recent developments of mobile NMR are reviewed which delineate the direction into which portable NMR is moving.

Blümich, Bernhard; Casanova, Federico; Danieli, Ernesto; Gong, Qingxia; Greferath, Marcus; Haber, Agnes; Kolz, Jürgen; Perlo, Juan

2008-12-01

243

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

244

NMR spectroscopy in the milli-Tesla regime: Measurement of 1H chemical-shift differences below the line width  

Microsoft Academic Search

NMR spectroscopy for chemical analysis at high field employs precision measurements of resonance frequencies governed by chemical shift and nuclear spin interactions. At low field and in the absence of hetero-nuclear J-couplings the natural line width limits the chemical shift measurements. We have performed chemical-shift resolved proton NMR spectra in the milli-Tesla regime, and found that in the presence of

Stephan Appelt; Stefan Glöggler; Friedrich W. Häsing; Ulrich Sieling; Ali Gordji Nejad; Bernhard Blümich

2010-01-01

245

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

246

Monitoring the on-line titration of enantiomeric omeprazole employing continuous-flow capillary microcoil 1H NMR spectroscopy.  

PubMed

The titration of the (S)-enantiomer of omeprazole with the (R)-enantiomer in chloroform-d(1) is monitored by continuous-flow capillary microcoil (1)H NMR spectroscopy employing a microcoil with a detection volume of 1.5 µl. The observed changes of the (1)H NMR chemical shifts indicate the formation of a heterochiral (R,S) dimer of omeprazole via its sulfinyl group and the NH group of the benzimidazole ring. PMID:22887745

Hentschel, Petra; Holtin, Karsten; Steinhauser, Lisa; Albert, Klaus

2012-12-01

247

HRMAS NMR spectroscopy combined with chemometrics as an alternative analytical tool to control cigarette authenticity.  

PubMed

In this paper, we present for the first time the use of high-resolution magic angle spinning nuclear magnetic resonance (HRMAS NMR) spectroscopy combined with chemometrics as an alternative tool for the characterization of tobacco products from different commercial international brands as well as for the identification of counterfeits. Although cigarette filling is a very complex chemical mixture, we were able to discriminate between dark, bright, and additive-free cigarette blends belonging to six different filter-cigarette brands, commercially available, using an approach for which no extraction procedure is required. Second, we focused our study on a specific worldwide-distributed brand for which established counterfeits were available. We discriminated those from their genuine counterparts with 100% accuracy using unsupervised multivariate statistical analysis. The counterfeits that we analyzed showed a higher amount of nicotine and solanesol and a lower content of sugars, all endogenous tobacco leaf metabolites. This preliminary study demonstrates the great potential of HRMAS NMR spectroscopy to help in controlling cigarette authenticity. PMID:24057027

Shintu, Laetitia; Caldarelli, Stefano; Campredon, Mylène

2013-11-01

248

Secondary structure determination of human. beta. -endorphin by /sup 1/H NMR spectroscopy  

SciTech Connect

The /sup 1/H NMR spectra of human ..beta..-endorphin indicate that the peptide exists in random-coil form in aqueous solution but becomes helical in mixed solvent. Thermal denaturation NMR experiments show that in water there is no transition between 24 and 75/sup 0/C, while a slow noncooperative thermal unfolding is observed in a 60% methanol-40% water mixed solvent in the same temperature range. These findings are consistent with circular dichroism studies by other workers concluding that ..beta..-endorphin is a random coil in water but that it forms 50% ..cap alpha..-helix or more in mixed solvents. The peptide in the mixed water-methanol solvent was further studied by correlated spectroscopy (COSY) and nuclear Overhauser effect spectroscopy (NOESY) experiments. These allow a complete set of assignments to be made and establish two distinct stretches over which the solvent induces formation of ..cap alpha..-helices: the first occurs between Tyr-1 and Thr-12 and the second between Leu-14 and extending to Lys-28. There is evidence that the latter is capped by a turn occurring between Lys-28 and Glu-31. These helices form at the enkephalin receptor binding site, which is at the amino terminus, and at the morphine receptor binding site, located at the carboxyl terminus. The findings suggest that these two receptors may specifically recognize ..cap alpha..-helices.

Lichtarge, O.; Jardetzky, O.; Li, C.H.

1987-09-08

249

Phosphorus Speciation of Sequential Extracts of Organic Amendments using NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

O.O. 1Akinremi Babasola Ajiboye and Donald N. Flaten 1Department of Soil Science, University of Manitoba, Winnipeg, R3T 2NT, Canada We carried out this study in order to determine the forms of phosphorus in various organic amendments using state-of-the art spectroscopic technique. Anaerobically digested biosolids (BIO), hog (HOG), dairy (DAIRY), beef (BEEF) and poultry (POULTRY) manures were subjected to sequential extraction. The extracts were analyzed by solution 31P nuclear magnetic resonance (NMR) spectroscopy. Most of the total P analysed by inductively coupled plasma-optical emission spectroscopy (ICP-OES) in the sequential extracts of organic amendments were orthophosphate, except POULTRY, which was dominated by organic P. The labile P fraction in all the organic amendments, excluding POULTRY, was mainly orthophosphate P from readily soluble calcium and some aluminum phosphates. In the poultry litter, however, Ca phytate was the main P species controlling P solubility. Such knowledge of the differences in the chemical forms of phosphorus in organic amendments are essential for proper management of these amendments for agro-environmental purposes Key words: organic amendments, solution NMR, sequential fractionation, labile phosphorus

Akinremi, O.

2009-04-01

250

Quantitation of crystalline and amorphous forms of anhydrous neotame using 13C CPMAS NMR spectroscopy.  

PubMed

Although most drugs are formulated in the crystalline state, amorphous or other crystalline forms are often generated during the formulation process. The presence of other forms can dramatically affect the physical and chemical stability of the drug. The identification and quantitation of different forms of a drug is a significant analytical challenge, especially in a formulated product. The ability of solid-state 13C NMR spectroscopy with cross polarization (CP) and magic-angle spinning (MAS) to quantify the amounts of three of the multiple crystalline and amorphous forms of the artificial sweetener neotame is described. It was possible to quantify, in a mixture of two anhydrous polymorphic forms of neotame, the amount of each polymorph within 1-2%. In mixtures of amorphous and crystalline forms of neotame, the amorphous content could be determined within 5%. It was found that the crystalline standards that were used to prepare the mixtures were not pure crystalline forms, but rather a mixture of crystalline and amorphous forms. The effect of amorphous content in the crystalline standards on the overall quantitation of the two crystalline polymorphic forms is discussed. The importance of differences in relaxation parameters and CP efficiencies on quantifying mixtures of different forms using solid-state NMR spectroscopy is also addressed. PMID:16258988

Offerdahl, Thomas J; Salsbury, Jonathon S; Dong, Zedong; Grant, David J W; Schroeder, Stephen A; Prakash, Indra; Gorman, Eric M; Barich, Dewey H; Munson, Eric J

2005-12-01

251

Structural investigation of aluminium doped ZnO nanoparticles by solid-state NMR spectroscopy.  

PubMed

The electrical conductivity of aluminium doped zinc oxide (AZO, ZnO:Al) materials depends on doping induced defects and grain structure. This study aims at relating macroscopic electrical conductivity of AZO nanoparticles with their atomic structure, which is non-trivial because the derived materials are heavily disordered and heterogeneous in nature. For this purpose we synthesized AZO nanoparticles with different doping levels and narrow size distribution by a microwave assisted polyol method followed by drying and a reductive treatment with forming gas. From these particles electrically conductive, optically transparent films were obtained by spin-coating. Characterization involved energy-dispersive X-ray analysis, wet chemical analysis, X-ray diffraction, electron microscopy and dynamic light scattering, which provided a basis for a detailed structural solid-state NMR study. A multinuclear ((27)Al, (13)C, (1)H) spectroscopic investigation required a number of 1D MAS NMR and 2D MAS NMR techniques (T(1)-measurements, (27)Al-MQMAS, (27)Al-(1)H 2D-PRESTO-III heteronuclear correlation spectroscopy), which were corroborated by quantum chemical calculations with an embedded cluster method (EEIM) at the DFT level. From the combined data we conclude that only a small part of the provided Al is incorporated into the ZnO structure by substitution of Zn. The related (27)Al NMR signal undergoes a Knight shift when the material is subjected to a reductive treatment with forming gas. At higher (formal) doping levels Al forms insulating (Al, H and C containing) side-phases, which cover the surface of the ZnO:Al particles and increase the sheet resistivity of spin-coated material. Moreover, calculated (27)Al quadrupole coupling constants serve as a spectroscopic fingerprint by which previously suggested point-defects can be identified and in their great majority be ruled out. PMID:22801707

Avadhut, Yamini S; Weber, Johannes; Hammarberg, Elin; Feldmann, Claus; Schmedt auf der Günne, Jörn

2012-09-01

252

Characterisation of sodium cations in dehydrated zeolite NaX by 23Na NMR spectroscopy.  

PubMed

23Na MAS, 2D nutation MAS, and DOR NMR spectroscopy has been applied to characterise the location of sodium cations in dehydrated zeolite NaX (Si/Al = 1.23). The 23Na MAS NMR spectra recorded at three different magnetic field strengths were decomposed by computer simulation into five lines, which were attributed to five crystallographically distinct cation sites known from X-ray diffraction studies. The assignments of the lines follow from electric field gradient calculations at the 23Na nuclei applying a simple point charge model based on crystal structure data. A weak Gaussian line at low field (delta iso = -6 ppm) is assigned to sodium cations at site I, two broad quadrupole patterns at the high-field side of the spectra are attributed to site I' (delta iso = -19 ppm, QCC = 5.2 MHz, eta = 0) and site II cations (delta iso = -15 ppm, QCC = 4.6 MHz, eta = 0), and two quadrupolar lines dominating the central region of the spectra originate from Na+ at two different III' sites (delta iso = -13 and -29 ppm, QCC = 2.6 and 1.6 MHz, eta = 0.7 and 0.9, respectively). Na+ ions located on a second I' site could be identified from the DOR NMR spectra. The line assignment is further corroborated by the reasonable agreement of the site occupancies estimated from the line intensities with those determined by X-ray diffraction. In addition, sodium site populations of five dehydrated zeolites NaX and NaY with Si/Al ratios between 1.09 and 4.0 were derived from the 23Na MAS NMR spectra. PMID:8986022

Feuerstein, M; Hunger, M; Engelhardt, G; Amoureux, J P

1996-11-01

253

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. PMID:21252295

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

2011-01-01

254

Heterogeneous ordered-disordered structure of the mesodomain in frozen sucrose-water solutions revealed by multiple electron paramagnetic resonance spectroscopies.  

PubMed

The microscopic structure of frozen aqueous sucrose solutions, over concentrations of 0-75% (w/v), is characterized by using multiple continuous-wave and pulsed electron paramagnetic resonance (EPR) spectroscopic and relaxation techniques and the paramagnetic spin probe, TEMPOL. The temperature dependence of the TEMPOL EPR line-shape anisotropy reveals a mobility transition, specified at 205 K in pure water and 255 ± 5 K for >1% (w/v) added sucrose. The transition temperature is >Tg, where Tg is the homogeneous water glass transition temperature, which shows that TEMPOL resides in the mesoscopic domain (mesodomain) at water-ice crystallite boundaries and that the mesodomain sucrose concentrations are comparable at >1% (w/v) added sucrose. Electron spin-echo envelope modulation (ESEEM) spectroscopy of TEMPOL-(2)H2-sucrose hyperfine interactions also indicates comparable sucrose concentrations in mesodomains at >1% (w/v) added sucrose. Electron spin-echo (ESE) detected longitudinal and phase memory relaxation times (T1 and TM, respectively) at 6 K indicate a general trend of increased mesodomain volume with added sucrose, in three stages: 1-15, 20-50, and >50% (w/v). The calibrated TEMPOL concentrations indicate that the mesodomain volume is less than the predicted maximally freeze-concentrated value [80 (w/w); 120% (w/v)], with transitions at 15-20% and 50% (w/v) starting sucrose. An ordered sucrose hydrate phase, which excludes TEMPOL, and a disordered, amorphous sucrose-water glass phase, in which TEMPOL resides, are proposed to compose a heterogeneous mesodomain. The results show that the ratio of ordered and disordered volume fractions in the mesodomain is exquisitely sensitive to the starting sucrose concentration. PMID:23464733

Chen, Hanlin; Sun, Li; Warncke, Kurt

2013-04-01

255

Heterogeneous Ordered-Disordered Structure of the Mesodomain in Frozen Sucrose-Water Solutions Revealed by Multiple Electron Paramagnetic Resonance Spectroscopies  

PubMed Central

The microscopic structure of frozen aqueous sucrose solutions, over concentrations of 0–75% (w/v), is characterized by using multiple continuous-wave and pulsed electron paramagnetic resonance (EPR) spectroscopic and relaxation techniques and the paramagnetic spin probe, TEMPOL. The temperature dependence of the TEMPOL EPR lineshape anisotropy reveals a mobility transition, specified at 205 K in pure water and 255 ±5 K for >1% (w/v) added sucrose. The transition temperature is >>Tg, where Tg is the homogeneous water glass transition temperature, which shows that TEMPOL resides in the mesoscopic domain (mesodomain) at water-ice crystallite boundaries, and that the mesodomain sucrose concentrations are comparable at >1% (w/v) added sucrose. Electron spin echo envelope modulation (ESEEM) spectroscopy of TEMPOL-2H2-sucrose hyperfine interactions also indicates comparable sucrose concentrations in mesodomains at >1% (w/v) added sucrose. Electron spin echo (ESE) – detected longitudinal and phase memory relaxation times (T1 and TM, respectively) at 6 K indicate a general trend of increased mesodomain volume with added sucrose, in three stages: 1-15, 20-50, and >50% (w/v). The calibrated TEMPOL concentrations indicate that the mesodomain volume is less than the predicted maximally freeze-concentrated value [80 (w/w); 120% (w/v)], with transitions at 15-20% and 50% (w/v) starting sucrose. An ordered sucrose hydrate phase, which excludes TEMPOL, and a disordered, amorphous sucrose-water glass phase, in which TEMPOL resides, are proposed to compose a heterogeneous mesodomain. The results show that the ratio of ordered and disordered volume fractions in the mesodomain is exquisitely sensitive to the starting sucrose concentration. PMID:23464733

Chen, Hanlin; Sun, Li; Warncke, Kurt

2013-01-01

256

The use of election paramagnetic resonance spectroscopy in early preformulation experiments: the impact of different experimental formulations on the release of a lipophilic spin probe into gastric juice.  

PubMed

The lipophilic spin probe TEMPOL-benzoate was dissolved in different experimental formulations, including polyethylene glycol 400 (PEG 400), Miglyol, glycerol monooleate (GMO), and Cremophor RH-40. Samples were measured by electron paramagnetic resonance (EPR) spectroscopy before and after addition to human gastric juice. The distance between the first and the third peak in the EPR spectrum (2a(N)) was measured to monitor the polarity of the spin probe's microenvironment. Moreover, the ratio between the signal amplitudes of the second and the third peak (a/b ratio) was used to monitor the mobility of the spin probe in a certain formulation. Thus, by calculating 2a(N) and the a/b ratio of the EPR spectra it was possible to determine a potential release of the spin probe from different formulations into gastric juice. It was found that oily and surface-active vehicles (Miglyol, Cremophor RH-40, and GMO) were more suitable to protect a lipophilic compound from being released within a gastric environment than PEG 400. Our results demonstrate that EPR spectroscopy seems to be a promising tool in early preformulation experiments to monitor the release of spin probes from formulations of different nature. This kind of experiment can be of value for the optimization of exploratory formulations. PMID:11226824

Bittner, B; Isel, H; Mountfield, R J

2001-03-01

257

Sub-second 2D NMR Spectroscopy at Sub-millimolar Concentrations Boaz Shapira, Erel Morris, Karol A. Muszkat, and Lucio Frydman*,  

E-print Network

Sub-second 2D NMR Spectroscopy at Sub-millimolar Concentrations Boaz Shapira, Erel Morris, Karol A that both kinds of complications could be simulta- neously lifted if pre-polarization and ultrafast 2D NMR hyperpolarization schemes a limited compatibility with 2D NMR, stemming from significant photobleaching effects

Frydman, Lucio

258

Pulsed electron paramagnetic resonance spectroscopy of (33)S-labeled molybdenum cofactor in catalytically active bioengineered sulfite oxidase.  

PubMed

Molybdenum enzymes contain at least one pyranopterin dithiolate (molybdopterin, MPT) moiety that coordinates Mo through two dithiolate (dithiolene) sulfur atoms. For sulfite oxidase (SO), hyperfine interactions (hfi) and nuclear quadrupole interactions (nqi) of magnetic nuclei (I ? 0) near the Mo(V) (d(1)) center have been measured using high-resolution pulsed electron paramagnetic resonance (EPR) methods and interpreted with the help of density functional theory (DFT) calculations. These have provided important insights about the active site structure and the reaction mechanism of the enzyme. However, it has not been possible to use EPR to probe the dithiolene sulfurs directly since naturally abundant (32)S has no nuclear spin (I = 0). Here we describe direct incorporation of (33)S (I = 3/2), the only stable magnetic sulfur isotope, into MPT using controlled in vitro synthesis with purified proteins. The electron spin echo envelope modulation (ESEEM) spectra from (33)S-labeled MPT in this catalytically active SO variant are dominated by the "interdoublet" transition arising from the strong nuclear quadrupole interaction, as also occurs for the (33)S-labeled exchangeable equatorial sulfite ligand [ Klein, E. L., et al. Inorg. Chem. 2012 , 51 , 1408 - 1418 ]. The estimated experimental hfi and nqi parameters for (33)S (aiso = 3 MHz and e(2)Qq/h = 25 MHz) are in good agreement with those predicted by DFT. In addition, the DFT calculations show that the two (33)S atoms are indistinguishable by EPR and reveal a strong intermixing between their out-of-plane pz orbitals and the dxy orbital of Mo(V). PMID:24387640

Klein, Eric L; Belaidi, Abdel Ali; Raitsimring, Arnold M; Davis, Amanda C; Krämer, Tobias; Astashkin, Andrei V; Neese, Frank; Schwarz, Günter; Enemark, John H

2014-01-21

259

Passivation of the Mg-related acceptor in GaN:Mg as monitored by electron paramagnetic resonance spectroscopy  

NASA Astrophysics Data System (ADS)

Hydrogen removal from GaN:Mg is necessary to activate p-type conductivity, but the exact chemical process is not clear. We have investigated this issue by monitoring the intensity of an electron paramagnetic resonance (EPR) signal thought to be due to the Mg acceptor complex. CVD-grown GaN:Mg films on sapphire were activated at 800 ^oC for 30 min in dry N2 or O_2. The samples were measured before and after annealing between 200 and 850 ^oC in 93% N_2:7% H2 forming gas. During the forming gas anneals, the intensity of the EPR signal decreased between 700 and 850 ^oC in both the N2 and O2 activated samples. However, the EPR signal intensity showed a dependence on the activation gas for temperatures between 200 and 700 ^oC in that it increased by about 20% for the N2 activated sample while decreasing by about 20% for the O2 sample. We suggest that this behavior reflects simultaneous activation and passivation processes which could differ in N2 and O2 treated GaN. After quenching the signal at 850 ^oC, we were able to re-activate the Mg signal in both samples by annealing them in their respective ambient gases indicating that the passivation of the Mg signal was due to the intoduction of hydrogen and not due to the decompostion of GaN. This work is supported by Dr. Colin Wood, ONR.

Matlock, D. M.; Zvanut, M. E.

2004-03-01

260

Unilateral NMR, 13C CPMAS NMR spectroscopy and micro-analytical techniques for studying the materials and state of conservation of an ancient Egyptian wooden sarcophagus.  

PubMed

A multi-technique approach was employed to study a decorated Egyptian wooden sarcophagus (XXV-XXVI dynasty, Third Intermediate Period), belonging to the Museo del Vicino Oriente of the Sapienza University of Rome. Portable non-invasive unilateral NMR was applied to evaluate the conservation state of the sarcophagus. Moreover, using unilateral NMR, a non-invasive analytical protocol was established to detect the presence of organic substances on the surface and/or embedded in the wooden matrix. This protocol allowed for an educated sampling campaign aimed at further investigating the state of degradation of the wood and the presence of organic substances by (13)C cross polarization magic angle spinning (CPMAS) NMR spectroscopy. The composition of the painted layer was analysed by optical microscopy (OM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Raman and surface enhanced (resonance) Raman spectroscopy (SERS/SERRS), infrared and GC-MS techniques, evidencing original components such as clay minerals, Egyptian green, indigo, natural gums, and also highlighting restoration pigments and alteration compounds. The identification of the wood, of great value for the reconstruction of the history of the artwork, was achieved by means of optical microscopy. PMID:20931176

Proietti, Noemi; Presciutti, Federica; Di Tullio, Valeria; Doherty, Brenda; Marinelli, Anna Maria; Provinciali, Barbara; Macchioni, Nicola; Capitani, Donatella; Miliani, Costanza

2011-03-01

261

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

262

Electron paramagnetic resonance (EPR) biodosimetry  

Microsoft Academic Search

Radiation-induced electron paramagnetic resonance (EPR) signals were first reported by Gordy et al. [Proc. Natl. Acad. Sci. USA 41 (1955) 983]. The application of EPR spectroscopy to ionizing radiation dosimetry was later proposed by Brady et al. [HealthPhys. 15 (1968) 43]. Since that time EPR dosimetry has been applied to accident and epidemiologic dose reconstruction, radiation therapy, food irradiation, quality

Marc Desrosiers; David A Schauer

2001-01-01

263

Exploring high-resolution magic angle spinning (HR-MAS) NMR spectroscopy for metabonomic analysis of apples.  

PubMed

Classical liquid-state high-resolution (HR) NMR spectroscopy has proved a powerful tool in the metabonomic analysis of liquid food samples like fruit juices. In this paper the application of (1)H high-resolution magic angle spinning (HR-MAS) NMR spectroscopy to apple tissue is presented probing its potential for metabonomic studies. The (1)H HR-MAS NMR spectra are discussed in terms of the chemical composition of apple tissue and compared to liquid-state NMR spectra of apple juice. Differences indicate that specific metabolic changes are induced by juice preparation. The feasibility of HR-MAS NMR-based multivariate analysis is demonstrated by a study distinguishing three different apple cultivars by principal component analysis (PCA). Preliminary results are shown from subsequent studies comparing three different cultivation methods by means of PCA and partial least squares discriminant analysis (PLS-DA) of the HR-MAS NMR data. The compounds responsible for discriminating organically grown apples are discussed. Finally, an outlook of our ongoing work is given including a longitudinal study on apples. PMID:23146259

Vermathen, Martina; Marzorati, Mattia; Vermathen, Peter

2012-01-01

264

Characterization of trimethyllysine 115 in calmodulin by 14N and 13C NMR spectroscopy.  

PubMed

In this paper, we describe three approaches to study the single trimethyllysine 115 in calmodulin. First, 14N NMR spectroscopy has been used as a novel spectroscopic tool. Because of the unique symmetrical tetrahedral substitution of its side chain, the trimethyllysine residue gives rise to a sharp 14N NMR resonance; hence, this has allowed the detection and quantitation of the level of trimethylation. Trimethyllysine side chains of bovine testis calmodulin and yeast cytochrome c were shown to have a high mobility in aqueous solution as determined by 14N NMR relaxation measurements. Second, we have purified mammalian calmodulin from an overproducing Escherichia coli strain. By comparison of the 1H-13C heteronuclear multiple quantum coherence spectra of 13C-dimethylated calmodulin samples from bovine testis and E. coli, the resonance for Lys-115 in bacterially expressed calmodulin could be identified. pH titration experiments showed that epsilon-NH2 group of Lys-115 has a normal pKa value both in the apo and Ca2+ forms of the protein and in a complex of calmodulin with a 22-residue calmodulin-binding peptide derived from myosin light chain kinase. Third, we have shown that mutation of Lys-115 to the uncharged Gln residue does not alter the ability of the protein to stimulate the enzymes cyclic nucleotide phosphodiesterase and myosin light chain kinase. These results show that the trimethylation of Lys-115 is not caused by an unusual pKa and reactivity of its epsilon-NH2 group and that its side chain remains flexible. Moreover, our data suggest that the introduction of a permanent positive charge on Lys-115 by trimethylation is also not the major reason for this specific post-translational modification. PMID:8106489

Zhang, M; Huque, E; Vogel, H J

1994-02-18

265

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. PMID:22767482

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

2012-01-01

266

Surface speciation of phosphate on boehmite (gamma-AlOOH) determined from NMR spectroscopy.  

PubMed

Interaction of phosphate with the surfaces of clays and metal oxyhydroxides is important for nutrient cycling in natural and agricultural systems. We examined the specific adsorption of phosphate to boehmite (gamma-AlOOH) by solid-state (31)P NMR spectroscopy, which yields evidence for the presence of two bridging bidentate surface complexes differing in protonation. For samples prepared along the sorption isotherm at pH 5, distinct phosphate environments are observed as two major peaks in (31)P NMR spectra (chemical shifts of 0 and -6 ppm) that show little change in relative intensity with adsorbate loading. Both peaks correspond to rigid phosphate in close proximity to H, as indicated by (31)P{(1)H} cross-polarization magic-angle-spinning (CP/MAS) data, and yield nearly identical (31)P{(27)Al} dephasing curves in rotational echo adiabatic passage double resonance (REAPDOR) experiments. The REAPDOR results indicate that both phosphate environments have similar coordination to Al and are best fit by dephasing curves simulated for bridging bidentate configurations. The two resolved phosphate species exhibit distinct (31)P chemical shift anisotropy (CSA) and intensity variations with pH, the peak near 0 ppm being dominant at pH > 7. (31)P CSA's from quantum chemical calculations of hydrated bidentate cluster models with varying protonation state show that the CSA for monoprotonated phosphate is unique and closely matches that for the peak at -6 ppm. The CSA for the peak at 0 ppm is consistent with both di- and nonprotonated phosphate, but assignment to the latter is suggested based on the dominance of this peak in samples prepared at high pH and with trends in (31)P NMR chemical shifts. PMID:20180597

Li, Wei; Feng, Jian; Kwon, Kideok D; Kubicki, James D; Phillips, Brian L

2010-04-01

267

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

268

Characterization of Glycosaminoglycans by 15N-NMR Spectroscopy and in vivo Isotopic Labeling  

PubMed Central

Characterization of glycosaminoglycans (GAGs), including chondroitin sulfate (CS), dermatan sulfate (DS) and heparan sulfate (HS), is important in developing an understanding of cellular function and in assuring quality of preparations destined for biomedical applications. While use of 1H and 13C NMR spectroscopy has become common in characterization of these materials, spectra are complex and difficult to interpret when a more heterogeneous GAG type or a mixture of several types is present. Herein a method based on 1H-15N two dimensional NMR experiments is described. The 15N- and 1H-chemical shifts of amide signals from 15N-containing acetylgalactosamines in CSs are shown to be quite sensitive to the sites of sulfation (4-, 6- or 4,6-), and easily distinguishable from those of DS. The amide signals from residual 15N-containing acetylglucosamines in HS are shown to be diagnostic of the presence of these GAG components as well. Most data were collected at natural abundance of 15N despite its low percentage. However enrichment of the 15N-content in GAGs using metabolic incorporation from 15N-glutamine added to cell culture media is also demonstrated, and used to distinguish metabolic states in different cell types. PMID:20423049

Pomin, Vitor H.; Sharp, Joshua S.; Li, Xuanyang; Wang, Lianchun; Prestegard, James H.

2010-01-01

269

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 (R²>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 10 mM 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

270

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

271

Quadruple-resonance magic-angle spinning NMR spectroscopy of deuterated solid proteins.  

PubMed

(1)H-detected magic-angle spinning NMR experiments facilitate structural biology of solid proteins, which requires using deuterated proteins. However, often amide protons cannot be back-exchanged sufficiently, because of a possible lack of solvent exposure. For such systems, using (2)H?excitation instead of (1)H?excitation can be beneficial because of the larger abundance and shorter longitudinal relaxation time, T1, of deuterium. A new structure determination approach, "quadruple-resonance NMR spectroscopy", is presented which relies on an efficient (2)H-excitation and (2)H-(13)C cross-polarization (CP) step, combined with (1)H?detection. We show that by using (2)H-excited experiments better sensitivity is possible on an SH3 sample recrystallized from 30?% H2O. For a membrane protein, the ABC transporter ArtMP in native lipid bilayers, different sets of signals can be observed from different initial polarization pathways, which can be evaluated further to extract structural properties. PMID:24474388

Akbey, Ümit; Nieuwkoop, Andrew J; Wegner, Sebastian; Voreck, Anja; Kunert, Britta; Bandara, Priyanga; Engelke, Frank; Nielsen, Niels Chr; Oschkinat, Hartmut

2014-02-24

272

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

273

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

274

Quantitative analysis of sesquiterpene lactones in extract of Arnica montana L. by 1H NMR spectroscopy.  

PubMed

(1)H NMR spectroscopy was used as a method for quantitative analysis of sesquiterpene lactones present in a crude lactone fraction isolated from Arnica montana. Eight main components - tigloyl-, methacryloyl-, isobutyryl- and 2-methylbutyryl-esters of helenalin (H) and 11?,13-dihydrohelenalin (DH) were identified in the studied sample. The method allows the determination of the total amount of sesquiterpene lactones and the quantity of both type helenalin and 11?,13-dihydrohelenalin esters separately. Furthermore, 6-O-tigloylhelenalin (HT, 1), 6-O-methacryloylhelenalin (HM, 2), 6-O-tigloyl-11?,13-dihydrohelenalin (DHT, 5), and 6-O-methacryloyl-11?,13-dihydrohelenalin (DHM, 6) were quantified as individual components. PMID:20837387

Staneva, Jordanka; Denkova, Pavletta; Todorova, Milka; Evstatieva, Ljuba

2011-01-01

275

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

276

Pulse design for broadband correlation NMR spectroscopy by multi-rotating frames.  

PubMed

We present a method for designing radio-frequency (RF) pulses for broadband or multi-band isotropic mixing at low power, suitable for protein NMR spectroscopy. These mixing pulses are designed analytically, rather than by numerical optimization, by repeatedly constructing new rotating frames of reference. We show how pulse parameters can be chosen frame-by-frame to systematically reduce the effective chemical shift bandwidth, but maintain most of the effective J-coupling strength. The effective Hartmann-Hahn mixing condition is then satisfied in a multi-rotating frame of reference. This design method yields multi-band and broadband mixing pulses at low RF power. In particular, the ratio of RF power to mixing bandwidth for these pulses is lower than for existing mixing pulses, such as DIPSI and FLOPSY. Carbon-carbon TOCSY experiments at low RF power support our theoretical analysis. PMID:23420125

Coote, Paul; Arthanari, Haribabu; Yu, Tsyr-Yan; Natarajan, Amarnath; Wagner, Gerhard; Khaneja, Navin

2013-03-01

277

Photo-CIDNP NMR spectroscopy of a heme-containing protein  

NASA Astrophysics Data System (ADS)

There are relatively few examples of the application of photo-CIDNP NMR spectroscopy to chromophore-containing proteins. The most likely reason for this is that simultaneous absorption of light by the photosensitiser molecule and the protein chromophore reduces the effectiveness of the photochemical reaction that produces the observed nuclear polarisation. We present details of experiments performed on the air-oxidised form of a small cytochrome, from the thermophilic bacterium Hydrogenobacter thermophilus, using both the wild-type protein and apo and holo forms of a double alanine b-type mutant. We show that, along with the apo state, it is possible to generate CIDNP in the air-oxidised form of the b-type mutant, but not in the corresponding c-type cytochrome. This finding is supported by control experiments using horse-heart cytochrome c.

Day, Iain J.; Wain, Rachel; Tozawa, Kaeko; Smith, Lorna J.; Hore, P. J.

2005-08-01

278

Recent applications of /sup 13/C NMR spectroscopy to biological systems  

SciTech Connect

Carbon-13 nuclear magnetic resonance (NMR) spectroscopy, in conjunction with carbon-13 labelling, is a powerful new analytical technique for the study of metabolic pathways and structural components in intact organelles, cells, and tissues. The technique can provide, rapidly and non-destructively, unique information about: the architecture and dynamics of structural components; the nature of the intracellular environment; and metabolic pathways and relative fluxes of individual carbon atoms. With the aid of results recently obtained by us and those reported by a number of other laboratories, the problems and potentialities of the technique will be reviewed with emphasis on: the viscosities of intracellular fluids; the structure and dynamics of the components of membranes; and the primary and secondary metabolic pathways of carbon in microorganisms, plants, and mammalian cells in culture.

Matwiyoff, N.A.

1981-01-01

279

Platinum-modified adenines: unprecedented protonation behavior revealed by NMR spectroscopy and relativistic density-functional theory calculations.  

PubMed

Two novel Pt(IV) complexes of aromatic cytokinins with possible antitumor properties were prepared by reaction of selected aminopurines with K(2)PtCl(6). The structures of both complexes, 9-[6-(benzylamino)purine] pentachloroplatinate (IV) and 9-[6-(furfurylamino)purine] pentachloroplatinate (IV), were characterized in detail by using two-dimensional NMR spectroscopy ((1)H, (13)C, (15)N, and (195)Pt) in solution and CP/MAS NMR techniques in the solid state. We report for the first time the X-ray structure of a nucleobase adenine derivative coordinated to Pt(IV) via the N9 atom. The protonation equilibria for the complexes in solution were characterized by using NMR spectroscopy (isotropic chemical shifts and indirect nuclear spin-spin coupling constants) and the structural conclusions drawn from the NMR analysis are supported by relativistic density-functional theory (DFT) calculations. Because of the presence of the Pt atom, hybrid GGA functionals and scalar-relativistic and spin-orbit corrections were employed for both the DFT calculations of the molecular structure and particularly for the NMR chemical shifts. In particular, the populations of the N7-protonated and neutral forms of the complexes in solution were characterized by correlating the experimental and the DFT-calculated NMR chemical shifts. In contrast to the chemical exchange process involving the N7-H group, the hydrogen atom at N3 was determined to be unexpectedly rigid, probably because of the presence of the stabilizing intramolecular interaction N3-H···Cl. The described methodology combining the NMR spectroscopy and relativistic DFT calculations can be employed for characterizing the tautomeric and protonation equilibria in a large family of transition-metal-modified purine bases. PMID:22260420

Vícha, Jan; Demo, Gabriel; Marek, Radek

2012-02-01

280

NMR characterization of shocked quartz  

SciTech Connect

We have characterized experimentally and naturally-shocked quartz (both synthetic and natural samples) by solid state nuclear magnetic resonance (NMR) spectroscopy. Relaxation analysis of experimentally-shocked samples provides a means for quantitative characterization of the amorphous/disordered silica component NMR spectra demonstrate that magnetization in both the amorphous and crystalline components follows power-law behavior as a function of recycle time. This observation is consistent with the relaxation of nuclear spins by paramagnetic impurities. A fractal dimension can be extracted from the power-law exponent associated with each phase, and relative abundances can be extracted from integrated intensities of deconvolved peaks. NMR spectroscopy of naturally-shocked sandstone from Meteor Crater, Arizona (USA) led to the discovery of a new amorphous hydroxylated silica phase. Solid state NMR spectra of both experimentally and naturally shocked quartz were unexpectedly rich in microstructural information, especially when combined with relaxation analysis and cross-polarization studies. We suggest solid state NMR as a potentially useful tool for examining shock-induced microstructural changes in other inorganic compounds, with possible implications for shock processing of structural ceramics.

Boslough, M.B.; Cygan, R.T.; Assink, R.A. [Sandia National Labs., Albuquerque, NM (United States); Kirkpatrick, R.J. [Illinois Univ., Urbana, IL (United States)

1994-03-01

281

MAGNETIC RESONANCE IN CHEMISTRY, VOL. 33, 729-733 (1995) 61NiNMR Spectroscopy of Di-and  

E-print Network

MAGNETIC RESONANCE IN CHEMISTRY, VOL. 33, 729-733 (1995) 61NiNMR Spectroscopy of Di) are low, whereas the quadrupolar moment (0.16 x m2)of this spin-3/2 nucleus is large. The latter leads, measurementsof 'difficult' quadrupolar nuclei such as 61Niin solution are also facilitated by the bene- ficial

Bluemel, Janet

282

Muscle metabolism changes with training in the nonamputated limb after vascular amputation: Interest of phosphorus 31 NMR spectroscopy  

Microsoft Academic Search

Objective: To determine by 31P nuclear magnetic resonance (NMR) spectroscopy the efficacy of training in improving aerobic metabolism of calf muscle in nonamputated limb after recent vascular amputation; to assess the possible associated microcirculatory changes; and to evaluate the need for noninvasive monitoring techniques during training in the nonamputated limb after recent vascular amputation.Design: Prospective study, before and after training.

Veronique Dulieu; Jean-Marie Casillas; Jean-Françis Maillefert; Paul Walker; Yves Cottin; Jean-Pierre Didier; François Brunotte

1997-01-01

283

NMR spectroscopy with force-gradient detection on a GaAs epitaxial layer  

NASA Astrophysics Data System (ADS)

We demonstrate nuclear magnetic resonance spectroscopy on 35 ?m3 of 69Ga in a GaAs epitaxial layer in vacuum at 5 K, and 5 T yielding a linewidth on the order of 10 kHz. This was achieved by a force-gradient magnetic resonance detection scheme, using the interaction between the force-gradient of a Ni sphere-tipped single crystal Si cantilever and the nuclear spins to register changes in the spin state as a change in the driven cantilever's natural resonant frequency. The dichotomy between the background magnetic field (B0) homogeneity requirements imposed by NMR spectroscopy and the magnetic particle's large magnetic field gradient is resolved via sample shuttling during the NMR pulse encoding. A GaAs sample is polarized in a B0 of 5 T for 3 * T1. The sample is shuttled away from the magnetic particle to a region of negligible magnetic field inhomogeneity. A (?/2)x pulse rotates the polarization to the xy-plane, the magnetization is allowed to precess for 2-200 ?s before a (?/2)x or (?/2)y pulse stores the remaining spin along the z-axis that represents a single point of the free induction decay (FID). The sample is shuttled back to the established tip-sample distance. An adiabatic rapid passage (ARP) sweep inverts the spins in a volume of interest, causing the cantilever's natural resonance frequency to shift an amount proportional to the spin polarization in the volume. By varying the delay between the first and second (?/2) pulses the entire FID is measured.

Alexson, Dimitri A.; Smith, Doran D.

2013-10-01

284

Investigation of Cu-doped Li2B4O7 single crystals by electron paramagnetic resonance and time-resolved optical spectroscopy  

NASA Astrophysics Data System (ADS)

A low-temperature study of the thermoluminescent dosimeter material, lithium tetraborate (Li2B4O7) doped by Cu, has been carried out by the methods of electron paramagnetic resonance (EPR) and time-resolved polarization spectroscopy using 4-20 eV synchrotron radiation and 1 µs Xe flash lamp pulses in the region 3-6 eV. The observed EPR spectra of an unpaired hole with strong d-character and characteristic hyperfine splittings can be ascribed to Cu2+ substituted at a Li lattice site and displaced due to relaxation. The results on the Cu+-related luminescence strongly support the conclusion about a low-symmetry position of copper impurity ions in the lithium tetraborate lattice. The temperature dependence of the decay kinetics of the Cu+-related 3.35 eV emission indicates a triplet nature for the relaxed excited state of the Cu+ centres. An off-centre position of the Cu+ ion in the relaxed excited state is suggested.

Corradi, G.; Nagirnyi, V.; Kotlov, A.; Watterich, A.; Kirm, M.; Polgár, K.; Hofstaetter, A.; Meyer, M.

2008-01-01

285

Characterization of Monomeric MnII/III/IV-Hydroxo Complexes from X- and Q-Band Dual Mode Electron Paramagnetic Resonance (EPR) Spectroscopy  

PubMed Central

Manganese–hydroxo species have been implicated in C–H bond activation performed by metalloenzymes, but the electronic properties of many of these intermediates are not well characterized. The present work presents a detailed characterization of three Mnn–OH complexes (where n = II, III, and IV) of the tris[(N?-tert-butylureaylato)-N-ethylene]aminato ([H3buea]3?) ligand using X- and Q-band dual mode electron paramagnetic resonance (EPR). Quantitative simulations for the [MnIIH3buea(OH)]2? complex demonstrated the ability to characterize similar MnII species commonly present in the resting states of manganese-containing enzymes. The spin states of the MnIII and MnIV complexes determined from EPR spectroscopy are S = 2 and 3/2, respectively, as expected for the C3 symmetry imposed by the [H3buea]3? ligand. Simulations of the spectra indicated the constant presence of two MnIV species in solutions of [MnIVH3buea(OH)] complex. The simulations of perpendicular- and parallel-mode EPR spectra allow determination of zero-field splitting and hyperfine parameters for all complexes. For the MnIII and MnIV complexes, density functional theory calculations are used to determine the isotropic Mn hyperfine values, to compare the excited electronic state energies, and to give theoretical estimates of the zero-field energy. PMID:24156406

Gupta, Rupal; Taguchi, Taketo; Borovik, A. S.; Hendrich, Michael P.

2013-01-01

286

Control of Chemical Dynamics Using Arbitrary Shaped Optical Pulses and Laser-Enhanced NMR Spectroscopy.  

NASA Astrophysics Data System (ADS)

A key feature of this thesis is the application of novel laser techniques to various fields of spectroscopy. The overall effort has been towards achieving either chemical control or enhanced spectroscopic resolution. The issue of chemical control forms the major bulk. Over the past decade, theoretical and technological developments have made it possible for a modern day chemist to be a more active participant in nature's chemical processes. Consequently, although the idea of manipulating chemical reactions has been a long term dream, it is only now that realization of such dreams has become realistic. One of the major contributions that is leading towards this realization is the development of pulse shaping techniques. Here, we concentrate on the important developments in this area that has come by recently, particularly emphasizing new results from our laboratory. We discuss in detail the current state-of-the-art, and present some experimental and theoretical demonstrations of chemical control by using arbitrarily shaped pulses. The major strength of our approach to pulse shaping has been in considering "robustness in the laboratory" as a primary constraint. Most of the shapes, addressed here, work under adiabatic conditions where the exact shape of the pulse is not critical as long as the basic criteria dictated by the adiabatic theorem are satisfied. A novel approach of "molecular pulse shaping"--using the molecule itself to generate its own pulse shape--is presented as an example of the ultimate form of robustness. Finally, we get into the issue of resolution enhancement by coupling laser radiation into a Nuclear Magnetic Resonance (NMR) spectrometer. Spectroscopic resolution enhancement is an everlasting effort in the field of NMR--even more for biological NMR. We present some of the recent experimental findings in our laboratory that show selective dispersion in the NMR spectrum when it is acquired under a non-resonant laser irradiation of the sample. Albeit promising, the observed effects are weak and the theoretical understanding of these experiments is not profound enough for implementing any immediate applications.

Goswami, Debabrata

287

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

288

Electron paramagnetic resonance spectroscopy with N-methyl-D-glucamine dithiocarbamate iron complexes distinguishes nitric oxide and nitroxyl anion in a redox-dependent manner: applications in identifying nitrogen monoxide products from nitric oxide synthase  

Microsoft Academic Search

Though a large number of studies indicate that nitric oxide synthase (NOS) is responsible for NO production in biological systems, controversy still remains concerning whether NOS directly produces NO. Schmidt et al. (PNAS 93:144492, 1996) proposed that NOS first synthesizes nitroxyl anion (NO?), which is then converted to NO by superoxide dismutase (SOD). With electron paramagnetic resonance spectroscopy using N-methyl-D-glucamine

Yong Xia; A. J Cardounel; Anatoly F Vanin; Jay L Zweier

2000-01-01

289

Multiple acquisition/multiple observation separated local field/chemical shift correlation solid-state magic angle spinning NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Multiple acquisition spectroscopy (MACSY) experiments that enable multiple free induction decays to be recorded during individual experiments are demonstrated. In particular, the experiments incorporate separated local field spectroscopy into homonuclear and heteronuclear correlation spectroscopy. The measured heteronuclear dipolar couplings are valuable in structure determination as well as in enhancing resolution by providing an additional frequency axis. In one example four different three-dimensional spectra are obtained in a single experiment, demonstrating that substantial potential saving in experimental time is available when multiple multi-dimensional spectra are required as part of solid-state NMR studies.

Das, Bibhuti B.; Opella, Stanley J.

2014-08-01

290

Multiple acquisition/multiple observation separated local field/chemical shift correlation solid-state magic angle spinning NMR spectroscopy.  

PubMed

Multiple acquisition spectroscopy (MACSY) experiments that enable multiple free induction decays to be recorded during individual experiments are demonstrated. In particular, the experiments incorporate separated local field spectroscopy into homonuclear and heteronuclear correlation spectroscopy. The measured heteronuclear dipolar couplings are valuable in structure determination as well as in enhancing resolution by providing an additional frequency axis. In one example four different three-dimensional spectra are obtained in a single experiment, demonstrating that substantial potential saving in experimental time is available when multiple multi-dimensional spectra are required as part of solid-state NMR studies. PMID:25023566

Das, Bibhuti B; Opella, Stanley J

2014-08-01

291

(1)H NMR spectroscopy for profiling complex carbohydrate mixtures in non-fractionated beer.  

PubMed

A plethora of biological and biotechnological processes involve the enzymatic remodelling of carbohydrates in complex mixtures whose compositions affect both the processes and products. In the current study, we employed high-resolution (1)H NMR spectroscopy for the analysis of cereal-derived carbohydrate mixtures as exemplified on six beer samples of different styles. Structural assignments of more than 50 carbohydrate moieties were obtained using (1)H1-(1)H2 groups as structural reporters. Spectroscopically resolved carbohydrates include more than ''20 different'' small carbohydrates with more than 38 isomeric forms in addition to cereal polysaccharide fragments with suspected organoleptic and prebiotic function. Structural motifs at the cleavage sites of starch, ?-glucan and arabinoxylan fragments were identified, showing different extent and specificity of enzymatic polysaccharide cleavage during the production of different beer samples. Diffusion ordered spectroscopy supplied independent size information for the characterisation and identification of polysaccharide fragments, indicating the presence especially of high molecular weight arabinoxylan fragments in the final beer. PMID:24360420

Petersen, Bent O; Nilsson, Mathias; Bøjstrup, Marie; Hindsgaul, Ole; Meier, Sebastian

2014-05-01

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. PMID:20225842

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

2010-01-01

293

Characterization of cyclodextrin complexes of camostat mesylate by ESI mass spectrometry and NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Supramolecular interactions between camostat mesylate, a serine protease inhibitor ( 1), with ?-, ?-, and ?-cyclodextrin (CD) in water were investigated using electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy. ESI mass spectral analysis revealed that the 1:1 stoichiometry in all the complexes was formed. The binding constants ( Kst) calculated by linear equations constructed from the ESI mass spectra of all the complexes indicated that ?-CD was most favorable complexing agent for the binding with 1 among the CDs. Pronounced changes in the 1H chemical shift upon complex formation with ?-CD were observed for the protons of the two aromatic rings of 1, with much larger chemical shift changes observed for the protons of the guanidinyl group-linked aromatic ring of 1. These results suggest that the cavity of ?-CD rather than that of ?- or ?-CD is large enough to accommodate the guanidine group of 1. Spatial geometry of 1 within the cavity of ?-CD was further identified with two-dimensional rotating frame nuclear Overhauser effect spectroscopy (2D ROESY) experiment. The observed ROESY cross peaks indicated intermolecular dipolar interactions between the two aromatic ring protons of 1 and the protons within the cavity of ?-CD. Based on the 1:1 stoichiometry of the complex, ROESY cross peaks suggest that two types of 1:1 complexes of ?-CD with 1 exist simultaneously in solution with different geometries.

Kwon, Soonho; Lee, Woonhyoung; Shin, Hye-Jin; Yoon, Sung-il; Kim, Yun-tae; Kim, Young-Jin; Lee, Kyungruyl; Lee, Sanghoo

2009-12-01

294

Characteristics of zero-quantum correlation spectroscopy in MAS NMR experiments  

NASA Astrophysics Data System (ADS)

Zero-quantum coherence generation and reconversion in magic-angle spinning solid-state NMR is analyzed. Two methods are discussed based on implementations using symmetry-based pulse sequences that utilize either isotropic J couplings or dipolar couplings. In either case, the decoupling of abundant proton spins plays a crucial role for the efficiency of the zero-quantum generation. We present optimized sequences for measuring zero-quantum single-quantum correlation spectra in solids, achieving an efficiency of 50% in ubiquitin. The advantages and disadvantages of zero-quantum single-quantum over single-quantum single-quantum correlation spectroscopy are explored, and similarities and differences with double-quantum single-quantum correlation spectroscopy are discussed. Finally, possible application of zero-quantum single-quantum experiments to polypeptides, where it can lead to better spectral resolution is investigated using ubiquitin, where we find high efficiency and high selectivity, but also increased line widths in the MQ dimension.

Köneke, Stephanie G.; van Beek, Jacco D.; Ernst, Matthias; Meier, Beat H.

2010-12-01

295

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

296

The effects of cholesterol on magnetically aligned phospholipid bilayers: a solid-state NMR and EPR spectroscopy study  

NASA Astrophysics Data System (ADS)

This paper presents the first time that both solid-state NMR spectroscopy and EPR spectroscopy are used to study the effects of cholesterol on magnetically aligned phospholipid bilayers (bicelles). Solid-state deuterium NMR spectroscopy was carried out using both chain perdeuterated 1,2-dimyristoyl- sn-glycero-3-phosphatidylcholine (DMPC-d 54) and a partially deuterated ?-[2,2,3,4,4,6- 2H 6]cholesterol (cholesterol-d 6). Also, EPR spectroscopy was carried out utilizing a 3?-doxyl-5?-cholestane (cholestane) spin probe incorporated into magnetically aligned bilayers to provide a more complete picture about the ordering and dynamics of the phospholipid and cholesterol molecules in the bicelle membrane system. The results demonstrate that cholesterol was successfully incorporated into the phospholipid bilayers. The molecular order parameters extracted directly from the 2H NMR spectra of both DMPC-d 54 and cholesterol-d 6 were compared to that from the EPR study of cholestane. The order parameters indicate that the sterol was motionally restricted, and that the DMPC had high order and low motion for the hydrocarbon segments close to the head groups of the phospholipids and less order and more rapid motion toward the terminal methyl groups. Both methods clearly indicate an overall increase in the degree of ordering of the molecules in the presence of cholesterol and a decrease in the degree of ordering at higher temperatures. However, EPR spectroscopy and 2H NMR spectroscopy exhibit different degrees of sensitivity in detecting the phospholipid molecular motions in the membrane. Finally, cholesterol increases the minimum alignment temperature necessary to magnetically align the phospholipid bilayers.

Lu, Jun-Xia; Caporini, Marc A.; Lorigan, Gary A.

2004-05-01

297

Thermodynamic and activation parameters for dissociation of [CpCr(CO){sub 3}]{sub 2} and [Cp*Cr(CO){sub 3}]{sub 2} into paramagnetic monomers from {sup 1}H NMR shift and line width measurements  

SciTech Connect

Substitution of pentamethyl cyclopentadienide (Cp*) for cyclopentadienide (Cp) is commonly used as an approach for increasing ligand steric requirements that can enhance dissociation of M-M bonded complexes. {sup 1}H NMR spectra for solutions prepared by dissolution of [CpCr(CO){sub 3}]{sub 2} and [Cp*Cr(CO){sub 3}]{sub 2} in toluene in the temperature range 190--390 K are interpreted in terms of thermodynamic and kinetic parameters for dissociation of the diamagnetic dimers into the paramagnetic monomers CpCr(CO){sub 3} and Cp*Cr(CO){sub 3}. There is no evidence in this temperature range for thermally populated excited states or non-Curie magnetic behavior of the monomers making a significant contribution to the NMR. An expression for the temperature dependence of the NMR chemical shift at limiting fast interchange of monomer and dimer in terms of the {Delta}H{degree} and {Delta}S{degree} for dimer dissociation is applied in determining the thermodynamic parameters for Cr-Cr bond homolysis of [CpCr(CO){sub 3}]{sub 2} ({Delta}H{sub 1}{degree} = 15.3 {+-} 0.6 kcal mol{sup {minus}1}; {Delta}S{sub 1}{degree} = 39 {+-} 2 cal K{sup {minus}1} mol{sup {minus}1}) and [Cp*Cr(CO){sub 3}]{sub 2} ({Delta}H{sub 2}{degree} = 14.2 {+-} 0.4 kcal mol{sup {minus}1}; {Delta}S{sub 2}{degree} = 47 {+-} 2 cal K{sup {minus}1}mol{sup {minus}1}). Rate constants and activation parameters have been evaluated from {sup 1}H NMR line broadening in the region of slow dimer-monomer interchange for dissociation of [CpCr(CO){sub 3}]{sub 2} ({kappa}{sub 1} (240 K) {approx} 59 s{sup {minus}1}; {Delta}H{sub 1}{double{underscore}dagger} = 17 {+-} 2 kcal mol{sup {minus}1}; {Delta}S{sub 1}{double{underscore}dagger} = 21 {+-} 6 cal K{sup {minus}1} mol{sup {minus}1}) and [Cp*Cr(CO){sub 3}]{sub 2} ({kappa}{sub 2} (240 K) {approx} 1.4 x 10{sup 4} s{sup {minus}1}; {Delta}H{sub 2}{double{underscore}dagger} = 16 {+-} 1 kcal mol{sup {minus}1}; {Delta}S{sub 2}{double{underscore}dagger} = 30 {+-} 6 cal K{sup {minus}1} mol{sup {minus}1}). Paramagnetic shifts also were used in deriving electron-proton coupling constants (A{sub H}) for CpCr(CO){sub 3}(9.22 x 10{sup 5} Hz) and Cp*Cr(CO){sub 3} (1.33 x 10{sup 6} Hz).

Woska, D.C.; Ni, Y.; Wayland, B.B.

1999-09-06

298

Correlating nuclear frequencies by two-dimensional ELDOR-detected NMR spectroscopy  

NASA Astrophysics Data System (ADS)

ELDOR (Electron Double Resonance)-detected NMR (EDNMR) is a pulse EPR experiment that is used to measure the transition frequencies of nuclear spins coupled to electron spins. These frequencies are further used to determine hyperfine and quadrupolar couplings, which are signatures of the electronic and spatial structures of paramagnetic centers. In recent years, EDNMR has been shown to be particularly useful at high fields/high frequencies, such as W-band (?95 GHz, ?3.5 T), for low ? quadrupolar nuclei. Although at high fields the nuclear Larmor frequencies are usually well resolved, the limited resolution of EDNMR still remains a major concern. In this work we introduce a two dimensional, triple resonance, correlation experiment based on the EDNMR pulse sequence, which we term 2D-EDNMR. This experiment allows circumventing the resolution limitation by spreading the signals in two dimensions and the observed correlations help in the assignment of the signals. First we demonstrate the utility of the 2D-EDNMR experiment on a nitroxide spin label, where we observe correlations between 14N nuclear frequencies. Negative cross-peaks appear between lines belonging to different MS electron spin manifolds. We resolved two independent correlation patterns for nuclear frequencies arising from the EPR transitions corresponding to the 14N mI = 0 and mI = -1 nuclear spin states, which severely overlap in the one dimensional EDNMR spectrum. The observed correlations could be accounted for by considering changes in the populations of energy levels that S = 1/2, I = 1 spin systems undergo during the pulse sequence. In addition to these negative cross-peaks, positive cross-peaks appear as well. We present a theoretical model based on the Liouville equation and use it to calculate the time evolution of populations of the various energy levels during the 2D-EDNMR experiment and generated simulated 2D-EDMR spectra. These calculations show that the positive cross-peaks appear due to off resonance effects and/or nuclear relaxation effects. These results suggest that the 2D-EDNMR experiment can be also useful for relaxation pathway studies. Finally we present preliminary results demonstrating that 2D-EDNMR can resolve overlapping 33S and 14N signals of type 1 Cu(II) center in 33S enriched Azurin.

Kaminker, Ilia; Wilson, Tiffany D.; Savelieff, Masha G.; Hovav, Yonatan; Zimmermann, Herbert; Lu, Yi; Goldfarb, Daniella

2014-03-01

299

A structural study of epoxidized natural rubber (ENR-50) and its cyclic dithiocarbonate derivative using NMR spectroscopy techniques.  

PubMed

A structural study of epoxidized natural rubber (ENR-50) and its cyclic dithiocarbonate derivative was carried out using NMR spectroscopy techniques. The overlapping (1)H-NMR signals of ENR-50 at ? 1.56, 1.68-1.70, 2.06, 2.15-2.17 ppm were successfully assigned. In this work, the <(13)C-NMR chemical shift assignments of ENR-50 were consistent to the previously reported work. A cyclic dithiocarbonate derivative of ENR-50 was synthesized from the reaction of purified ENR-50 with carbon disulfide (CS(2)), in the presence of 4-dimethylaminopyridine (DMAP) as catalyst at reflux temperature. The cyclic dithiocarbonate formation involved the epoxide ring opening of the ENR-50. This was followed by insertion of the C-S moiety of CS(2) at the oxygen attached to the quaternary carbon and methine carbon of epoxidized isoprene unit, respectively. The bands due to the C=S and C-O were clearly observed in the FTIR spectrum while the (1)H-NMR spectrum of the derivative revealed the peak attributed to the methylene protons had split. The (13)C-NMR spectrum of the derivative further indicates two new carbon peaks arising from the >C=S and quaternary carbon of cyclic dithiocarbonate. All other (1)H- and (13)C-NMR chemical shifts of the derivative remain unchanged with respect to the ENR-50. PMID:22971583

Hamzah, Rosniza; Bakar, Mohamad Abu; Khairuddean, Melati; Mohammed, Issam Ahmed; Adnan, Rohana

2012-01-01

300

How to investigate oxygen supply, uptake, and utilization simultaneously by interleaved NMR imaging and spectroscopy of the skeletal muscle.  

PubMed

Human skeletal muscle perfusion, oxygenation, and high-energy phosphate distribution were measured simultaneously by interleaved (1)H and (31)P NMR spectroscopy and (1)H NMR imaging in vivo. From these parameters, arterial oxygen supply (DO(2)), muscle reoxygenation rate, mitochondrial ATP production, and O(2) consumption (VO(2)) were deduced at the recovery phase of a short ischemic exercise bout. In addition, by using a reformulation of the mass conservation law, muscle maximum O(2) extraction was calculated from these parameters. PMID:16155896

Carlier, P G; Brillault-Salvat, C; Giacomini, E; Wary, C; Bloch, G

2005-10-01

301

Exploring weak, transient protein-protein interactions in crowded in vivo environments by in-cell NMR spectroscopy  

PubMed Central

Biology relies on functional interplay of proteins in the crowded and heterogeneous environment inside cells, and functional protein interactions are often weak and transient. Thus, methods are needed that preserve these interactions and provide information about them. In-cell NMR spectroscopy is an attractive method to study a protein’s behavior in cells because it may provide residue-level structural and dynamic information. Yet several factors limit the feasibility of protein NMR spectroscopy in cells, and among them slow rotational diffusion has emerged as the most important. In this paper, we seek to elucidate the causes of the dramatically slow protein tumbling in cells and in so doing to gain insight into how the intracellular viscosity and weak, transient interactions modulate protein mobility. To address these questions, we characterized the rotational diffusion of three model globular proteins in E. coli cells using 2D heteronuclear NMR spectroscopy. These proteins have a similar molecular size and globular fold, but very different surface properties, and indeed, they show very different rotational diffusion in the E. coli intracellular environment. Our data are consistent with an intracellular viscosity approximately eight times that of water—too low to be a limiting factor to observing small globular proteins by in-cell NMR spectroscopy. Thus, we conclude that transient interactions with cytoplasmic components significantly and differentially affect the mobility of proteins and therefore their NMR detectability. Moreover, we suggest that an intricate interplay of total protein charge and hydrophobic interactions plays a key role in regulating these weak intermolecular interactions in cells. PMID:21942871

Wang, Qinghua; Zhuravleva, Anastasia; Gierasch, Lila M.

2011-01-01

302

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

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; Leitão, Alexandre A.

2013-09-01

304

31P-NMR SPECTROSCOPY OF RAT LIVER DURING SIMPLE STORAGE OR CONTINUOUS HYPOTHERMIC PERFUSION1  

PubMed Central

SUMMARY The ATP content and intracellular pH (pHi)3 of isolated rat liver before, during, and after cold preservation in either UW-lactobionate (UW, n=10) or Euro-Collins (EC, n=8) solutions were monitored using phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy. The 31P-NMR spectra were obtained on a 4.7-Tesla system operating at 81 MHz. Fructose metabolism, liver enzyme release, O2 consumption, and rat survival after liver transplantation were also evaluated. During simple cold storage (SCS), the ATP level declined to undetectable levels with both preservation solutions while the pHi declined to approximately 7.0. In contrast, during continuous hypothermic perfusion (CHP), hepatic ATP levels remained measurable during the 24-hour EC preservation and actually increased significantly (p>0.01) during UW preservation. After reperfusion at 37°C with Krebs-lactate, the SCS livers treated with EC differed significantly from the UW livers in terms of their ATP and pHi as well as their response to a fructose challenge. In contrast, livers undergoing CHP demonstrated similar behaviors with both solutions. These results demonstrate an increase in the hepatic ATP content during CHP which occurs with UW but is not seen with EC. On the other hand, only livers that were simply stored with UW achieved significant survival after transplant, while CHP livers were affected by vascular damage as demonstrated by fatal thrombosis after transplant. These data suggest that ATP content is not the only determinant of good liver function although a system of hypothermic perfusion might further improve liver preservation efficacy should injury to vascular endothelium be avoided. PMID:1402332

Rossaro, Lorenzo; Murase, Noriko; Caldwell, Cary; Farghali, Hassan; Casavilla, Adrian; Starzl, Thomas E.; Ho, Chien; Van Thiel, David H.

2010-01-01

305

The Basics of NMR  

NSDL National Science Digital Library

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

Hornak, Joseph

2003-10-10

306

Single-Scan NMR Spectroscopy at Arbitrary Dimensions Yoav Shrot and Lucio Frydman*  

E-print Network

a parametric incrementation of their values throughout independent experiments. Two-dimensional (2D) NMR whereby data acquisition in 2D NMR can be parallelized, enabling the collection of complete 2D spectral sets within a single transient. The present paper discusses the extension of this 2D NMR methodology

Frydman, Lucio

307

Sensitivity Enhancement in 1D Heteronuclear NMR Spectroscopy via Single-Scan Inverse  

E-print Network

place.[5] During the development of 2D NMR as a tool for biomolecu- lar investigations; a potential made possible by the advent of spatially encoded acquisition methods capable of providing 2D NMR NMR obser- vations. A well-known solution to this sensitivity problem is indi- rect detection: a 2D

Frydman, Lucio

308

Principles and Features of Single-Scan Two-Dimensional NMR Spectroscopy  

E-print Network

resonance (2D NMR) provides one of the foremost contemporary tools available for the elucidation of molecular structure, function, and dynamics. Execution of a 2D NMR experiment generally involves scanning various conceptual and experimental aspects of this novel 2D NMR methodology. The basic principles

Frydman, Lucio

309

Monitoring Mechanistic Details in the Synthesis of Pyrimidines via Real-Time, Ultrafast Multidimensional NMR Spectroscopy  

E-print Network

of nitriles to yield alkylpyrimidines. Up to 2500 2D NMR data sets were thus collected over the course of complex chemical problems such as this one. Two-dimensional (2D) NMR, in particular, could enable one of formation. Doing so, however, requires completing the 2D NMR measurement in time scales compatible

Frydman, Lucio

310

Intramolecular electron transfer versus substrate oxidation in lactoperoxidase: investigation of radical intermediates by stopped-flow absorption spectrophotometry and (9-285 GHz) electron paramagnetic resonance spectroscopy.  

PubMed

We have combined the information obtained from rapid-scan electronic absorption spectrophotometry and multifrequency (9-295 GHz) electron paramagnetic resonance (EPR) spectroscopy to unequivocally determine the electronic nature of the intermediates in milk lactoperoxidase as a function of pH and to monitor their reactivity with organic substrates selected by their different accessibilities to the heme site. The aim was to address the question of the putative catalytic role of the protein-based radicals. This experimental approach allowed us to discriminate between the protein-based radical intermediates and [Fe(IV)=O] species, as well as to directly detect the oxidation products by EPR. The advantageous resolution of the g anisotropy of the Tyr (*) EPR spectrum at high fields showed that the tyrosine of the [Fe(IV)=O Tyr (*)] intermediate has an electropositive and pH-dependent microenvironment [g(x) value of 2.0077(0) at pH >or= 8.0 and 2.0066(2) at 4.0

Fielding, Alistair J; Singh, Rahul; Boscolo, Barbara; Loewen, Peter C; Ghibaudi, Elena M; Ivancich, Anabella

2008-09-16

311

Silicon displacement threshold energy determined by electron paramagnetic resonance and positron annihilation spectroscopy in cubic and hexagonal polytypes of silicon carbide  

NASA Astrophysics Data System (ADS)

Both for electronic and nuclear applications, it is of major interest to understand the properties of point defects into silicon carbide (SiC). Low energy electron irradiations are supposed to create primary defects into materials. SiC single crystals have been irradiated with electrons at two beam energies in order to investigate the silicon displacement threshold energy into SiC. This paper presents the characterization of the electron irradiation-induced point defects into both polytypes hexagonal (6H) and cubic (3C) SiC single crystals by using both positron annihilation spectroscopy (PAS) and electron paramagnetic resonance (EPR). The nature and the concentration of the generated point defects depend on the energy of the electron beam and the polytype. After an electron irradiation at an energy of 800 keV v Si mono-vacancies and v Si-v C di-vacancies are detected in both 3C and 6H-SiC polytypes. On the contrary, the nature of point defects detected after an electron irradiation at 190 keV strongly depends on the polytype. Into 6H-SiC crystals, silicon Frenkel pairs v Si-Si are detected whereas only carbon vacancy related defects are detected into 3C-SiC crystals. The difference observed in the distribution of defects detected into the two polytypes can be explained by the different values of the silicon displacement threshold energies for 3C and 6H-SiC. By comparing the calculated theoretical numbers of displaced atoms with the defects numbers measured using EPR, the silicon displacement threshold energy has been estimated to be slightly lower than 20 eV in the 6H polytype and close to 25 eV in the 3C polytype.

Kerbiriou, X.; Barthe, M.-F.; Esnouf, S.; Desgardin, P.; Blondiaux, G.; Petite, G.

2007-05-01

312

Adsorption-desorption induced structural changes of Cu-MOF evidenced by solid state NMR and EPR spectroscopy.  

PubMed

Adsorption-desorption induced structural changes of Cu(bpy)(H(2)O)(2)(BF(4)),(bpy) (bpy = 4,4'-bipyridine) [Cu-MOF] have been evidenced by combined NMR and EPR spectroscopy. Upon adsorption of probe molecules even at a few mbar, EPR spectra show that they are activated to form complexes at Cu(II) sites, which results in a change of the Cu-MOF's structure as indicated by a high-field shift of the (11)B MAS NMR. After desorption, both EPR and (11)B MAS NMR spectra evidenced that the structure of the Cu-MOF reversibly shifted to the original state. This observation indicates that MOFs can undergo structural changes during processes where adsorption-desorption steps are involved such as gas storage, separation, and catalysis. PMID:19159296

Jiang, Yijiao; Huang, Jun; Kasumaj, Besnik; Jeschke, Gunnar; Hunger, Michael; Mallat, Tamas; Baiker, Alfons

2009-02-18

313

Could smaller really be better? Current and future trends in high-resolution microcoil NMR spectroscopy.  

PubMed

NMR is an invaluable analytical technique that provides structural and chemical information about a molecule without destroying the sample. However, NMR suffers from an inherent lack of sensitivity compared to other popular analytical techniques. This trends article focuses on strategies to increase the sensitivity of NMR using solenoidal microcoil, microstrip, and microslot probes. The role of these reduced-volume receiver coils for detection in hyphenated capillary electrophoresis (CE) and capillary isotachophoresis (cITP) NMR experiments is discussed. Future directions will likely build on work to develop probes containing multiple coils for high-throughput NMR and field-portable instruments. PMID:21879299

Jones, Christopher J; Larive, Cynthia K

2012-01-01

314

Silicon carbide polytype characterisation in coated fuel particles by Raman spectroscopy and 29Si magic angle spinning NMR  

NASA Astrophysics Data System (ADS)

The silicon carbide layer of a batch of as-produced TRISO (tristructural isotropic) coated fuel particles with zirconia kernels was characterised by Raman spectroscopy and magic angle spinning nuclear magnetic resonance (MAS-NMR). The techniques were evaluated as a probe for the evolution of SiC local structure as a function of chemical vapour deposition processing. Nuclear magnetic resonance resolved 29Si resonances for multiple hexagonal or cubic silicon local environments, consistent with a mixture of 6H, 15R and 4H polytypes, within a majority (36%) 3C-SiC target structure. Polarised Raman spectroscopy by contrast, showed some evidence of hexagonal and cubic local environments but no evidence for clearly defined hexagonal or orthorhombic polytypes. It was clear from the Raman that there was significant scattering from q > 0 regions of the Brillouin zone, consistent with a loss of translational symmetry associated with stacking faults. Simulation and TEM images suggested that the signals observed in Raman and NMR correspond closer to a random arrangement of SiC layers in which structures similar to the various polytypes occur over short distances. As NMR is a probe of local environment, the signals obtained were similar to those that would come from a mixture of crystallites, each of a well-defined polytype. The NMR data was analysed quantitatively by fitting the spectra of known polytypes and by using a simple model to represent the random arrangement of layers in a heavily faulted crystal.

López-Honorato, E.; Brigden, C.; Shatwell, R. A.; Zhang, H.; Farnan, I.; Xiao, P.; Guillermier, P.; Somers, J.

2013-02-01

315

Metabolic profiling for studying chemotype variations in Withania somnifera (L.) Dunal fruits using GC-MS and NMR spectroscopy.  

PubMed

Withania somnifera (L.) Dunal (Solanaceae), commonly known as Ashwagandha, is one of the most valued Indian medicinal plant with several pharmaceutical and nutraceutical applications. Metabolic profiling was performed by GC-MS and NMR spectroscopy on the fruits obtained from four chemotypes of W. somnifera. A combination of (1)H NMR spectroscopy and GC-MS identified 82 chemically diverse metabolites consisting of organic acids, fatty acids, aliphatic and aromatic amino acids, polyols, sugars, sterols, tocopherols, phenolic acids and withanamides in the fruits of W. somnifera. The range of metabolites identified by GC-MS and NMR of W. somnifera fruits showed various known and unknown metabolites. The primary and secondary metabolites observed in this study represent MVA, DOXP, shikimic acid and phenylpropanoid biosynthetic metabolic pathways. Squalene and tocopherol have been rated as the most potent naturally occurring compounds with antioxidant properties. These compounds have been identified by us for the first time in the fruits of W. somnifera. Multivariate principal component analysis (PCA) on GC-MS and NMR data revealed clear distinctions in the primary and secondary metabolites among the chemotypes. The variation in the metabolite concentration among different chemotypes of the fruits of W. somnifera suggest that specific chemovars can be used to obtain substantial amounts of bioactive ingredients for use as potential pharmacological and nutraceuticals agents. PMID:23578960

Bhatia, Anil; Bharti, Santosh K; Tewari, Shri K; Sidhu, Om P; Roy, Raja

2013-09-01

316

Characterization of a multicomponent lithium lithiate from a combined x-ray diffraction, NMR spectroscopy, and computational approach.  

PubMed

An unusual lithium lithiate [Li(diglyme)2 ][(diglyme)Li2 (C4 H3 S)3 ], made up from three carbanions, two lithium cations, and a single donor base molecule in the anion and a single lithium cation, coordinated by two donor base molecules, is investigated in a combined study including X-ray diffraction, NMR spectroscopy and computational approaches in solution and the solid state. While the multicomponent lithiate is the only species present in the solid state, solution NMR spectroscopy and computational methods were employed to identify a second species in solution. The dimer [(diglyme)Li(C4 H3 S)]2 coexists with the lithiate in solution in a 1:1 ratio, the more the higher the polarity of the solvent is. Only the combination of this multitude of methods provides a firm picture of the whole. PMID:25284593

Pöppler, Ann-Christin; Granitzka, Markus; Herbst-Irmer, Regine; Chen, Yu-Sheng; Iversen, Bo B; John, Michael; Mata, Ricardo A; Stalke, Dietmar

2014-11-24

317

Cherry tomatoes metabolic profile determined by ¹H-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 3 years 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

318

Metabolic footprinting study of white spruce somatic embryogenesis using NMR spectroscopy.  

PubMed

White spruce is an important commercial species for reforestation. The success in its propagation through somatic embryogenesis is well documented; however the physiological processes involved are poorly understood and remain unoptimized. The variable quality embryos generated in vitro from the same genotype suggest control at the protein and metabolite level. In order to probe metabolic changes, we have conducted a "metabolic footprinting" study, whereby culture media from growing cells was quantitatively analyzed to determine which metabolites were consumed and excreted. Such experiments are advantageous in that there is no need to quench cellular metabolism or extract intracellular metabolites through time-consuming protocols. In this paper we demonstrate the application of the footprinting assay to somatic embryo cells of white spruce (Picea glauca) using 1D (1)H NMR spectroscopy. We have surveyed embryogenesis metabolism in two types of media, maintenance (MN) and maturation (MT). MN medium does not result in shoot apical meristem (SAM) formation, while MT medium induces the necessary changes leading to fully developed somatic embryos. The two types of media were easily distinguished using metabolomics analysis, namely multivariate pattern recognition statistics (orthogonal partial least squares discriminatory analysis). From this analysis, we have identified numerous compounds involved with branched chain amino acid pathways such as valine and isoleucine. These results are explained on the basis of known metabolic pathways implicated in plant and animal developmental processes, and ultimately implicate altered CoA biosynthesis. PMID:19195904

Dowlatabadi, Reza; Weljie, Aalim M; Thorpe, Trevor A; Yeung, Edward C; Vogel, Hans J

2009-05-01

319

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

PubMed Central

Comprehensive application of solution NMR spectroscopy to studies of macromolecules remains fundamentally limited by the molecular rotational correlation time. For proteins, molecules larger than 30 kDa require complex experimental methods, such as TROSY in conjunction with isotopic labeling schemes that are often expensive and generally reduce the potential information available. We have developed the reverse micelle encapsulation strategy as an alternative approach. Encapsulation of proteins within the protective nano-scale water pool of a reverse micelle dissolved in ultra-low viscosity nonpolar solvents overcomes the slow tumbling problem presented by large proteins. Here, we characterize the contributions from the various components of the protein-containing reverse micelle system to the rotational correlation time of the encapsulated protein. Importantly, we demonstrate that the protein encapsulated in the reverse micelle maintains a hydration shell comparable in size to that seen in bulk solution. Using moderate pressures, encapsulation in ultra-low viscosity propane or ethane can be used to magnify this advantage. We show that encapsulation in liquid ethane can be used to reduce the tumbling time of the 43 kDa maltose binding protein from ~23 ns to ~10 ns. These conditions enable, for example, acquisition of TOCSY-type data resolved on the adjacent amide NH for the 42 kDa encapsulated maltose binding protein dissolved in liquid ethane, which is typically impossible for proteins of such size without use of extensive deuteration or the TROSY effect. PMID:21748265

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

2014-01-01

320

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

321

NMR-spectroscopy study of compounds in sodium-aluminum phosphate glass-forming systems  

SciTech Connect

The objective of this investigation was to explore a number of model systems used in the radioactive waste vitrification process. Using the method of NMR spectroscopy, the systems investigated consisted of water solutions of orthophosphoric acid, sodium/aluminium nitrates, as well as products of solid-state synthesis which form in the Na{sub 2}O-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5} system. The data indicated that the difference between the liquid and solid phases of glass-forming compounds is that aluminum phosphate complexes form in the liquid stage, while sodium phosphate complexes form in the solid stage. There arises the problem of establishing the effect on the formation of the phosphate glass as the liquid phase of the glass forming transforms into the solid phase of radioactive waste processing. It is possible that the sodium phosphate compounds form in the solid phase as a result of the substitution of sodium for aluminum in the aluminum phosphate compounds. The presence of these latter compounds would be the determining factor in the final product of the waste vitrification process.

Vashman, A.A.; Pronin, I.S.; Polyakov, A.S.

1994-06-01

322

NMR spectroscopy reveals a preferred conformation with a defined hydrophobic cluster for polyglutamine binding peptide 1.  

PubMed

Several important human inherited neurodegenerative diseases are caused by "polyQ expansions", which are aberrant long repeats of glutamine residues in proteins. PolyQ binding peptide 1 (QBP1), whose minimal active core sequence is Trp-Lys-Trp-Trp-Pro-Gly-Ile-Phe, binds to expanded polyQs and blocks their ?-structure transition, aggregation and in vivo neurodegeneration. Whereas QBP1 is a widely used, commercially available product, its structure is unknown. Here, we have characterized the conformations of QBP1 and a scrambled peptide (Trp-Pro-Ile-Trp-Lys-Gly-Trp-Phe) in aqueous solution by CD, fluorescence and NMR spectroscopies. A CD maximum at 227 nm suggests the presence of rigid Trp side chains in QBP1. Based on 41 NOE-derived distance constraints, the 3D structure of QBP1 was determined. The side chains of Trp 4 and Ile 7, and to a lesser extent, those of Lys 2, Trp 3 and Phe 8, form a small hydrophobic cluster. Pro 5 and Gly 6 adopt a type II tight turn and Lys 2's ?-NH3(+) is positioned to form a favorable cation-? interaction with Trp 4's indole ring. In contrast, the scrambled QBP1 peptide, which lacks inhibitory activity, does not adopt a preferred structure. These results provide a basis for future structure-based design approaches to further optimize QBP1 for therapy. PMID:25009140

Ramos-Martín, Francisco; Hervás, Rubén; Carrión-Vázquez, Mariano; Laurents, Douglas V

2014-09-15

323

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. PMID:23457556

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

2013-01-01

324

Phosphate defects and apatite inclusions in coral skeletal aragonite revealed by solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Recent development of paleo-nutrient proxies based on the phosphorus/calcium (P/Ca) ratio in tropical- and deep-water corals (also known as cold-water corals) require an understanding of the processes by which P is incorporated into the coral skeletal aragonite. Here, we apply single- and double-resonance solid-state nuclear magnetic resonance (NMR) spectroscopy to determine the speciation of P in coral aragonite. The results show that the majority of P occurs as phosphate defects in the aragonite structure, but in many samples a significant fraction of the P occurs also in crystalline hydroxylapatite inclusions. Quantification of the amount of hydroxylapatite indicates that its presence is not related simply to external environmental factors and that it can occur at varying abundances in different parts of the same corallite. Since there is currently no model available to describe the relationship between dissolved inorganic phosphate and its incorporation as apatite inclusions into carbonates, careful screening of samples which contain only phosphate in the aragonite structure or selective microsampling could improve proxy development.

Mason, Harris E.; Montagna, Paolo; Kubista, Laura; Taviani, Marco; McCulloch, Malcolm; Phillips, Brian L.

2011-12-01

325

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. PMID:24014355

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

2014-01-01

326

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

327

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.

328

In Vivo Phosphorus-31 Nuclear Magnetic Resonance (NMR) Spectroscopy Of Cardiac Metabolism: Initial Observations Of Hypoxia And Adrenergic Stimulation  

NASA Astrophysics Data System (ADS)

High resolution 31P nuclear magnetic resonance (NMR) spectroscopy has been applied to the direct, noninvasive examination of phosphorylated substrate metabolism in the myocardium of live rabbits. By the combination of field profiling gradients and a surface, or flat, NMR coil placed directly over the region of the thorax which contains the heart, spatially localized NMR measurements of metabolic function in live animals can be obtained. This technique, termed "topical magnetic resonance" or TMR, has been used to follow the effects of several physiological conditions on the tissue pH and levels of key, energy-rich phosphorylated compounds in the hearts of live, anesthetized rabbits. Changes in tissue content of adenosine triphosphate (ATP), creatine phosphate (CP), and inorganic phosphate (Pi) and the NMR line widths of these species have been observed in animals given appropriate doses of adriamycin for a five day period. These preliminary data demonstrate the potential of spectroscopic NMR techniques in the evaluation of disease states in organs and tissues within the body and the ability to monitor both toxic and therapeutic effects of drugs.

Nunnally, Ray L.

1982-12-01

329

Structural studies of boron and tellurium coordination in zinc borophosphate glasses by 11B MAS NMR and Raman spectroscopy  

Microsoft Academic Search

Zinc borophosphate glasses doped with TeO2 with different B2O3\\/P2O5 ratio were prepared, their basic properties were determined and their structure was studied by 11B MAS NMR and Raman spectroscopies. Structural studies were devoted to the investigation of changes in boron coordination in the dependence on changes in TeO2 content and in B2O3\\/P2O5 ratio in the borophosphate glasses. A special attention

Kate?ina Vosejpková; Ladislav Koudelka; Zden?k ?ernošek; Petr Mošner; Lionel Montagne; Bertrand Revel

330

Complex formation in rare-earth metal-propionic acid-diamagnetic salt systems by 1 H NMR spectroscopy  

Microsoft Academic Search

Complex formation of propionic acid with ions of rare-earth metals of the yttrium subgroup (D2O, 5.0 M NaNO3) in the absence and presence of diamagnetic Mg2+ cations was studied by 1H NMR spectroscopy in combination with mathematic simulation of complicated equilibria. Stability constants for monopropionate\\u000a complexes of rare-earth ions decrease when the rare-earth cation and Mg2+ are present in the

I. V. Sukhno; V. Yu. Buz’ko; V. T. Panyushkin

2006-01-01

331

Surface Species Formed during Aniline Methylation on Zeolite H–Y Investigated by in Situ MAS NMR Spectroscopy  

Microsoft Academic Search

Aniline alkylation with methanol on zeolite H–Y has been studied using in situ13C MAS NMR spectroscopy under batch conditions. To clarify the main reaction pathways, the conversion of methanol as well as the interaction of aniline with surface methoxy groups were investigated under similar conditions. Methanol-13C and methyl iodide-13C were used as labeled reactants. Co -adsorption of aniline and methanol-13C

Irina I. Ivanova; Elena B. Pomakhina; Alexander I. Rebrov; Michael Hunger; Yuryi G. Kolyagin; Jens Weitkampz

2001-01-01

332

Hydrogen bonding interactions of ?-phenylcinnamic acid isomers in the liquid phase studied by IR and NMR spectroscopies and computational methods  

Microsoft Academic Search

Intra- and intermolecular hydrogen bonding interactions of ?-phenylcinnamic acid isomers were studied in the solution phase by infrared (IR) and proton nuclear magnetic resonance (1H NMR) spectroscopies and the AM1 semi-empirical method. The solvents were CDCl3 or dimethyl sulfoxide (DMSO), the concentration of the acid isomers were varied. Spectroscopic measurements revealed that (i) intermolecular hydrogen bonds are typical for both

I. Pálinkó; B. Török; M. Rózsa-Tarjányi; J. T. Kiss; Gy. Tasi

1995-01-01

333

Monitoring of cell volume and water exchange time in perfused cells by diffusion-weighted1H NMR spectroscopy  

Microsoft Academic Search

Diffusion of intracellular water was measured in perfused cells embedded in basement membrane gel threads. F98 glioma cells, primary astrocytes, and epithelial KB cells were used and were exposed to osmotic stress, immunosuppressiva, the water channel blocker p-chloromercuriobenzenesulfonate (pCMBS), and apoptotic conditions. With diffusion-weighted 1H NMR spectroscopy changes in the intracellular signal could be monitored and quantified with single signal

Josef Pfeuffer; Ulrich Flögel; Dieter Leibfritz

1998-01-01

334

Application of 1 H-NMR spectroscopy to validation of berberine alkaloid reagents and to chemical evaluation of Coptidis Rhizoma  

Microsoft Academic Search

Berberine, palmatine, and coptisine are major pharmacologically active protoberberine alkaloids in Coptidis Rhizoma, and have\\u000a been used as indices for chemical evaluation of the crude drug. 1H-NMR spectroscopy was applied to determination of purities of commercial reagents of protoberberine alkaloids. The purities\\u000a of the alkaloids were calculated from the ratios of the intensities of the H-13 singlet signal at about

Keiko Hasada; Takamitsu Yoshida; Takeshi Yamazaki; Naoki Sugimoto; Tetsuji Nishimura; Akito Nagatsu; Hajime Mizukami

2011-01-01

335

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

336

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. PMID:15518588

Anick, David J

2004-01-01

337

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

338

A 13C CP\\/MAS NMR spectroscopy and AFM study of the structure of Glucagel™, a gelling ?-glucan from barley  

Microsoft Academic Search

The structure of Glucagel™, a mixed-linked (1?3), (1?4)-?-d-glucan extracted from barley, was examined using 13C CP\\/MAS NMR spectroscopy and atomic force microscopy (AFM). Results from 13C CP\\/MAS NMR spectroscopy showed that Glucagel™ contained regions with two distinct conformations. In some of the regions the ?-glucan chains associated to form a unique conformation, the A-conformation, while in the other regions the

Keith R. Morgan; Clive J. Roberts; Saul J. B. Tendler; Martyn C. Davies; Phil M. Williams

1999-01-01

339

Structural characterization of beta-D-(1 --> 3, 1 --> 6)-linked glucans using NMR spectroscopy.  

PubMed

Nondestructive structural analysis of a series of beta-D-(1 --> 3, 1 --> 6)-linked glucans (laminaran, curdlan, yeast glucan, scleroglucan, etc.) was performed using two-dimensional NMR spectroscopy. The relative ratios of H-1 at different AGUs provided the information about DPn and DB. The alpha-, and beta-anomeric protons on reducing terminals were assigned at 5.02 to approximately 5.03 ppm (J 3.6 to approximately 3.7 Hz), and 4.42 to approximately 4.43 ppm (J 7.6 to approximately 7.9 Hz), respectively, whereas the H-1 protons of internal AGUs and beta-(1 --> 6)-branched AGUs appeared at 4.56 to approximately 4.59 ppm (J 7.6 to approximately 7.8 Hz), and 4.26 to approximately 4.28 ppm (J 7.6 to approximately 10.6 Hz), respectively, in a mixed solvent of 6:1 Me2SO-d6-D2O at 80 degrees C. In the solvent, the OH peaks were eliminated from the spectra allowing the H-1 protons to appear clearly. In addition, the nonreducing terminal H-1 and H-1 at the AGU next to reducing terminal could be assigned at 4.45 to approximately 4.46 ppm (J 7.8 to approximately 7.9 Hz), and 4.51 to approximately 4.53 ppm (J 7.8 Hz), respectively. The DPn of the laminaran was 33 (polydispersity 1.12) and the DB was 0.07. The number of glucosyl units in the side chain of laminaran is more than one. The DPn and DB of the water-insoluble yeast glucan were 228 and 0.003, respectively. However the DPn of water soluble yeast glucan phosphate and curdlan was changed upon the number of freeze-drying processes and the content of water in the mixed solvent, respectively. And the DB of those were calculated as 0.02 and 0, respectively. The DB of scleroglucan was precisely calculated as 0.33, compared with the previously reported data. The H-1s at different AGUs of the various beta-D-(1 --> 3, 1 --> 6)-linked glucans having different DB can be exactly assigned by their chemical shifts in the mixed solvent system. This NMR analysis can be effectively used to determine the DP and DB of polysaccharides in a simple and non-destructive manner. PMID:11072840

Kim, Y T; Kim, E H; Cheong, C; Williams, D L; Kim, C W; Lim, S T

2000-09-22

340

Structural transitions in short-chain lipid assemblies studied by (31)P-NMR spectroscopy.  

PubMed Central

The self-assembled supramolecular structures of diacylphosphatidylcholine (diC(n)PC), diacylphosphatidylethanolamine (diC(n)PE), diacylphosphatidyglycerol (diC(n)PG), and diacylphosphatidylserine (diC(n)PS) were investigated by (31)P nuclear magnetic resonance (NMR) spectroscopy as a function of the hydrophobic acyl chain length. Short-chain homologs of these lipids formed micelles, and longer-chain homologs formed bilayers. The shortest acyl chain lengths that supported bilayer structures depended on the headgroup of the lipids. They increased in the order PE (C(6)) < PC (C(9)) < or = PS (C(9) or C(10)) < PG (C(11) or C(12)). This order correlated with the effective headgroup area, which is a function of the physical size, charge, hydration, and hydrogen-bonding capacity of the four headgroups. Electrostatic screening of the headgroup charge with NaCl reduced the effective headgroup area of PS and PG and thereby decreased the micelle-to-bilayer transition of these lipid classes to shorter chain lengths. The experimentally determined supramolecular structures were compared to the assembly states predicted by packing constraints that were calculated from the hydrocarbon-chain volume and effective headgroup area of each lipid. The model accurately predicted the chain-length threshold for bilayer formation if the relative displacement of the acyl chains of the phospholipid were taken into account. The model also predicted cylindrical rather than spherical micelles for all four diacylphospholipid classes and the (31)P-NMR spectra provided evidence for a tubular network that appeared as an intermediate phase at the micelle-to-bilayer transition. The free energy of micellization per methylene group was independent of the structure of the supramolecular assembly, but was -0.95 kJ/mol (-0.23 kcal/mol) for the PGs compared to -2.5 kJ/mol (-0.60 kcal/mol) for the PCs. The integral membrane protein OmpA did not change the bilayer structure of thin (diC(10)PC) bilayers. PMID:12124281

Kleinschmidt, Jorg H; Tamm, Lukas K

2002-01-01

341

Structural study of a lead–barium–aluminum phosphate glass by MAS-NMR spectroscopy  

Microsoft Academic Search

The 31P- and 27Al-MAS-NMR spectra of a lead–barium–aluminum phosphate glass were measured and analyzed, and the short range structure of the glass are discussed. The 31P-MAS-NMR spectrum of the glass studied has a single isotropic peak at ?4.76 ppm, indicating that orthophosphate species are the dominant P-sites in the glass. The 27Al-MAS-NMR spectrum of the glass shows that the aluminum

Guo Gongyi

1998-01-01

342

Electronic structure of the Mn-cofactor of modified bacterial reaction centers measured by electron paramagnetic resonance and electron spin echo envelope modulation spectroscopies.  

PubMed

The electronic structure of a Mn(II) ion bound to highly oxidizing reaction centers of Rhodobacter sphaeroides was studied in a mutant modified to possess a metal binding site at a location comparable to the Mn4Ca cluster of photosystem II. The Mn-binding site of the previously described mutant, M2, contains three carboxylates and one His at the binding site (Thielges et al., Biochemistry 44:389-7394, 2005). The redox-active Mn-cofactor was characterized using electron paramagnetic resonance (EPR) and electron spin echo envelope modulation (ESEEM) spectroscopies. In the light without bound metal, the Mn-binding mutants showed an EPR spectrum characteristic of the oxidized bacteriochlorophyll dimer and reduced quinone whose intensity was significantly reduced due to the diminished quantum yield of charge separation in the mutant compared to wild type. In the presence of the metal and in the dark, the EPR spectrum measured at the X-band frequency of 9.4 GHz showed a distinctive spin 5/2 Mn(II) signal consisting of 16 lines associated with both allowed and forbidden transitions. Upon illumination, the amplitude of the spectrum is decreased by over 80 % due to oxidation of the metal upon electron transfer to the oxidized bacteriochlorophyll dimer. The EPR spectrum of the Mn-cofactor was also measured at the Q-band frequency of 34 GHz and was better resolved as the signal was composed of the six allowed electronic transitions with only minor contributions from other transitions. A fit of the Q-band EPR spectrum shows that the Mn-cofactor is a high spin Mn(II) species (S = 5/2) that is six-coordinated with an isotropic g-value of 2.0006, a weak zero-field splitting and E/D ratio of approximately 1/3. The ESEEM experiments showed the presence of one (14)N coordinating the Mn-cofactor. The nitrogen atom is assigned to a His by comparing our ESEEM results to those previously reported for Mn(II) ions bound to other proteins and on the basis of the X-ray structure of the M2 mutant that shows the presence of only one His, residue M193, that can coordinate the Mn-cofactor. Together, the data allow the electronic structure and coordination environment of the designed Mn-cofactor in the modified reaction centers to be characterized in detail and compared to those observed in other proteins with Mn-cofactors. PMID:23868400

Tufts, A A; Flores, M; Olson, T L; Williams, J C; Allen, J P

2014-05-01

343

High-resolution diffusion and relaxation edited one- and two-dimensional 1H NMR spectroscopy of biological fluids.  

PubMed

A new approach to the characterization of biomolecules in whole biological fluids is presented based on simplification of 1H NMR spectra by utilizing differences in molecular diffusion coefficients alone and combinations of relaxation and diffusion parameters. New NMR pulse sequences incorporating both spectral editing features together with solvent water resonance elimination are presented. The methods are exemplified using whole human blood plasma, and it is shown that it is possible to obtain NMR spectra of the slowly diffusing species (generally large molecules) by diffusion editing, the slowly relaxing species (generally small molecules) by spin relaxation editing, or spectra showing any range of molecular mobility using a combination of the two methods. The diffusion-based editing methods are also applicable to the selection of resonances in two-dimensional NMR spectroscopy of biofluids, and we show this for the first time by the production of 1H-1H diffusion-edited TOCSY spectra of human blood plasma where the resonance intensities are weighted according to the molecular diffusion coefficient. In this case, by measuring a diffusion-edited 1H-1H TOCSY NMR spectrum of plasma, it is possible to obtain signals from only the macromolecular components, and this may be of benefit in the analysis of blood lipoproteins. In complex biofluids, the combination of diffusion and relaxation editing brings about considerable spectral simplification leading to an easier resonance assignment process. We also demonstrate the production of 1H NMR spectra with intensities corresponding to diffusion coefficient rather than number of protons, and this opens up new possibilities for pattern recognition classification of samples based on altered molecular mobility features of biofluid components. PMID:8843135

Liu, M; Nicholson, J K; Lindon, J C

1996-10-01

344

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

PubMed

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 (1)H-(1)H 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 (1)H-(1)H 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 (1)H irradiation. We also report that high resolution requires the preservation of (1)H 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 (1)H-(1)H 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 (1)H-{(13)C} D-HMQC experiments on [U-(13)C]-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 (14)N sites in L-histidine?HCl?H2O. PMID:24929867

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

2014-08-01

345

The structure of phosphate and borosilicate glasses and their structural evolution at high temperatures as studied with solid state NMR spectroscopy: Phase separation, crystallisation and dynamic species exchange  

NASA Astrophysics Data System (ADS)

In this contribution we present an in-depth study of the network structure of different phosphate based and borosilicate glasses and its evolution at high temperatures. Employing a range of advanced solid state NMR methodologies, complemented by the results of XPS, the structural motifs on short and intermediate length scales are identified. For the phosphate based glasses, at temperatures above the glass transition temperature Tg, structural relaxation processes and the devitrification of the glasses were monitored in situ employing MAS NMR spectroscopy and X-ray diffraction. Dynamic species exchange involving rapid P-O-P and P-O-Al bond breaking and reforming was observed employing in situ27Al and 31P MAS NMR spectroscopy and could be linked to viscous flow. For the borosilicate glasses, an atomic scale investigation of the phase separation processes was possible in a combined effort of ex situ NMR studies on glass samples with different thermal histories and in situ NMR studies using high temperature MAS NMR spectroscopy including 11B MAS, 29Si MAS and in situ29Si{ 11B} REAPDOR NMR spectroscopy.

Wegner, Sebastian; van Wüllen, Leo; Tricot, Gregory

2010-04-01

346

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

347

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). PMID:20617157

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

2009-01-01

348

Detection of Potential TNA and RNA Nucleoside Precursors in a Prebiotic Mixture by Pure Shift Diffusion-Ordered NMR Spectroscopy  

PubMed Central

In the context of prebiotic chemistry, one of the characteristics of mixed nitrogenous-oxygenous chemistry is its propensity to give rise to highly complex reaction mixtures. There is therefore an urgent need to develop improved spectroscopic techniques if onerous chromatographic separations are to be avoided. One potential avenue is the combination of pure shift methodology, in which NMR spectra are measured with greatly improved resolution by suppressing multiplet structure, with diffusion-ordered spectroscopy, in which NMR signals from different species are distinguished through their different rates of diffusion. Such a combination has the added advantage of working with intact mixtures, allowing analyses to be carried out without perturbing mixtures in which chemical entities are part of a network of reactions in equilibrium. As part of a systems chemistry approach towards investigating the self-assembly of potentially prebiotic small molecules, we have analysed the complex mixture arising from mixing glycolaldehyde and cyanamide, in a first application of pure shift DOSY NMR to the characterisation of a partially unknown reaction composition. The work presented illustrates the potential of pure shift DOSY to be applied to chemistries that give rise to mixtures of compounds in which the NMR signal resolution is poor. The direct formation of potential RNA and TNA nucleoside precursors, amongst other adducts, was observed. These preliminary observations may have implications for the potentially prebiotic assembly chemistry of pyrimidine threonucleotides, and therefore of TNA, by using recently reported chemistries that yield the activated pyridimidine ribonucleotides. PMID:23371787

Islam, Saidul; Aguilar, Juan A; Powner, Matthew W; Nilsson, Mathias; Morris, Gareth A; Sutherland, John D

2013-01-01

349

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

350

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

351

Precision high-throughput proton NMR spectroscopy of human urine, serum, and plasma for large-scale metabolic phenotyping.  

PubMed

Proton nuclear magnetic resonance (NMR)-based metabolic phenotyping of urine and blood plasma/serum samples provides important prognostic and diagnostic information and permits monitoring of disease progression in an objective manner. Much effort has been made in recent years to develop NMR instrumentation and technology to allow the acquisition of data in an effective, reproducible, and high-throughput approach that allows the study of general population samples from epidemiological collections for biomarkers of disease risk. The challenge remains to develop highly reproducible methods and standardized protocols that minimize technical or experimental bias, allowing realistic interlaboratory comparisons of subtle biomarker information. Here we present a detailed set of updated protocols that carefully consider major experimental conditions, including sample preparation, spectrometer parameters, NMR pulse sequences, throughput, reproducibility, quality control, and resolution. These results provide an experimental platform that facilitates NMR spectroscopy usage across different large cohorts of biofluid samples, enabling integration of global metabolic profiling that is a prerequisite for personalized healthcare. PMID:25180432

Dona, Anthony C; Jiménez, Beatriz; Schäfer, Hartmut; Humpfer, Eberhard; Spraul, Manfred; Lewis, Matthew R; Pearce, Jake T M; Holmes, Elaine; Lindon, John C; Nicholson, Jeremy K

2014-10-01

352

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

353

Molecular characterization of dissolved organic matter in glacial ice: coupling natural abundance 1H NMR and fluorescence spectroscopy.  

PubMed

Glaciers and ice sheets are the second largest freshwater reservoir in the global hydrologic cycle, and the onset of global climate warming has necessitated an assessment of their contributions to sea-level rise and the potential release of nutrients to nearby aquatic environments. In particular, the release of dissolved organic matter (DOM) from glacier melt could stimulate microbial activity in both glacial ecosystems and adjacent watersheds, but this would largely depend on the composition of the material released. Using fluorescence and (1)H NMR spectroscopy, we characterize DOM at its natural abundance in unaltered samples from a number of glaciers that differ in geographic location, thermal regime, and sample depth. Parallel factor analysis (PARAFAC) modeling of DOM fluorophores identifies components in the ice that are predominantly proteinaceous in character, while (1)H NMR spectroscopy reveals a mixture of small molecules that likely originate from native microbes. Spectrofluorescence also reveals a terrestrial contribution that was below the detection limits of NMR; however, (1)H nuclei from levoglucosan was identified in Arctic glacier ice samples. This study suggests that the bulk of the DOM from these glaciers is a mixture of biologically labile molecules derived from microbes. PMID:22385100

Pautler, Brent G; Woods, Gwen C; Dubnick, Ashley; Simpson, André J; Sharp, Martin J; Fitzsimons, Sean J; Simpson, Myrna J

2012-04-01

354

5-Fluoro pyrimidines: labels to probe DNA and RNA secondary structures by 1D 19F NMR spectroscopy  

PubMed Central

19F NMR spectroscopy has proved to be a valuable tool to monitor functionally important conformational transitions of nucleic acids. Here, we present a systematic investigation on the application of 5-fluoro pyrimidines to probe DNA and RNA secondary structures. Oligonucleotides with the propensity to adapt secondary structure equilibria were chosen as model systems and analyzed by 1D 19F and 1H NMR spectroscopy. A comparison with the unmodified analogs revealed that the equilibrium characteristics of the bistable DNA and RNA oligonucleotides were hardly affected upon fluorine substitution at C5 of pyrimidines. This observation was in accordance with UV spectroscopic melting experiments which demonstrated that single 5-fluoro substitutions in double helices lead to comparable thermodynamic stabilities. Thus, 5-fluoro pyrimidine labeling of DNA and RNA can be reliably applied for NMR based nucleic acid secondary structure evaluation. Furthermore, we developed a facile synthetic route towards 5-fluoro cytidine phosphoramidites that enables their convenient site-specific incorporation into oligonucleotides by solid-phase synthesis. PMID:19843610

Puffer, Barbara; Kreutz, Christoph; Rieder, Ulrike; Ebert, Marc-Olivier; Konrat, Robert; Micura, Ronald

2009-01-01

355

Structural effects of insulin-loading into HII mesophases monitored by electron paramagnetic resonance (EPR), small angle X-ray spectroscopy (SAXS), and attenuated total reflection Fourier transform spectroscopy (ATR-FTIR).  

PubMed

Insulin entrapment within a monoolein-based reverse hexagonal (H(II)) mesophase was investigated under temperature-dependent conditions at acidic (pH 3) and basic (pH 8) conditions. Studying the structure of the host H(II) system and the interactions of insulin under temperature-dependent conditions has great impact on the enhancement of its thermal stabilization and controlled release for the purposes of transdermal delivery. Small angle X-ray spectroscopy (SAXS) measurements show that pH variation and/or insulin entrapment preserve the hexagonal structure and do not influence the lattice parameter. Attenuated total reflection Fourier transform spectroscopy (ATR-FTIR) spectra indicate that, although insulin interacts with hydroxyl groups of GMO in the interface region, it is not affected by pH variations. Hence different microenvironments within the H(II) mesophase were monitored by a computer-aided electron paramagnetic resonance (EPR) analysis using 5-doxylstearic acid (5-DSA) as a pH-dependent probe. The microviscosity, micropolarity, order of systems, and distribution of the probes in different microenvironments were influenced by three factors: temperature, pH, and insulin solubilization. When the temperature is increased, microviscosity and order parameters decreased at both pH 3 and 8, presenting different decrease trends. It was found that, at pH 3, the protein perturbs the lipid structure while "pushing aside" the un-ionized 5-DSA probe to fit into the narrow water cylinders. At the interface region (pH 8), the probe was distributed in two differently structured environments that significantly modifies by increasing temperature. Insulin loading within the H(II) mesophase decreased the order and microviscosity of both the microenvironments and increased their micropolarity. Finally, the EPR analysis also provides information about the unfolding/denaturation of insulin within the channel at high temperatures. PMID:21591776

Mishraki, Tehila; Ottaviani, Maria Francesca; Shames, Alexander I; Aserin, Abraham; Garti, Nissim

2011-06-30

356

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

357

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

E-print Network

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

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

2014-01-01

358

Rapid determination of total conjugated linoleic acid content in select Canadian cheeses by (1)h NMR spectroscopy.  

PubMed

The application of (1)H nuclear magnetic resonance (NMR) spectroscopy to the measurement of conjugated linoleic acid (CLA) content in the lipid fraction of dairy products is both a novel and inviting alternative to traditional methods such as gas chromatography (GC), which can require time-consuming sample derivatization. In this work, a newly developed, rapid, and reliable lipid extraction protocol was combined with simple, nondestructive (1)H NMR spectroscopic analysis to measure the total CLA content in CLA standards and in various Canadian cheeses from conventional, organic, and grass-fed dairy sources. The total CLA concentrations (mg/g cheese) obtained using these new extraction and analysis methods were consistent with amounts found using the modified Folch extraction and GC analysis (correlation coefficient of 0.948). Results showed that cheeses from exclusively grass-fed dairy cows were significantly higher in total CLA content than either conventional or organic cheese. PMID:24099031

Prema, Dipesh; Pilfold, Jessica L; Krauchi, Jessica; Church, John S; Donkor, Kingsley K; Cinel, Bruno

2013-10-16

359

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

360

Lanthanum phosphate calcium aluminate glasses: 27Al and 31P NMR spectroscopy  

Microsoft Academic Search

A new protocol for synthesis of glassy aluminates with substantial content of the refractory compound LaPO4 has been developed, utilizing hydrated monazite and anhydrous metal oxides as starting materials. Ultra high-temperature NMR of samples containing up to 75mol% LaPO4 shows that monazite is incorporated homogeneously into melts, while analysis by electron microprobe, X-ray diffraction, solid-state NMR and Raman scattering shows

R. Marzke; S. Boucher; G. Wolf; J. Piwowarczyk; W. Petuskey

2008-01-01

361

3D Localized 2D NMR Spectroscopy on an MRI Scanner  

Microsoft Academic Search

Three-dimensionally localized versions of several two-dimensional NMR sequences have been implemented on a 1.5 T whole-body MRI\\/MRS scanner. In addition to the localization of voxels, the slice-selective RF pulses were also used for refocusing\\/transfer of various coherences in the 2D NMR sequences. Initial phantom and in vivo human studies are presented here. The sequences were localized versions of 2D J-resolved,

L. N. Ryner; J. A. Sorenson; M. A. Thomas

1995-01-01

362

A continuous phase-modulated approach to spatial encoding in ultrafast 2D NMR spectroscopy  

Microsoft Academic Search

Ultrafast 2D NMR replaces the time-domain parametrization usually employed to monitor the indirect-domain spin evolution, with an equivalent encoding along a spatial geometry. When coupled to a gradient-assisted decoding during the acquisition, this enables the collection of complete 2D spectra within a single transient. We have presented elsewhere two strategies for carrying out the spatial encoding underlying ultrafast NMR: a

Assaf Tal; Boaz Shapira; Lucio Frydman

2005-01-01

363

Stereoregularity evolution of isobornyl acrylate and styrene copolymers by 2D NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Isobornyl acrylate/styrene (B/S) copolymers of different compositions have been prepared by Atom Transfer Radical Polymerization (ATRP) using methyl-2-bromopropionate as an initiator and PMDETA/CuBr as catalyst under nitrogen atmosphere at 60 °C. Copolymer compositions calculated from 1H NMR spectra are used to determine the reactivity ratios of monomers. Linear Kelen-Tudos (KT) and non-linear error in variable methods (EVM) have been employed for determination of monomer reactivity ratios in copolymers. The reactivity ratios obtained from KT and EVM are found to be rB = 0.41 ± 0.08, rS = 0.92 ± 0.13 and rB = 0.41 and rS = 0.93 respectively. These copolymers have been analyzed for their stereochemical structure using various 1D (1H, 13C{1H}, DEPT) and 2D (HSQC, TOCSY, NOESY, HMBC) NMR techniques. 2D HSQC and TOCSY NMR experiments are employed to resolve the highly overlapped and complex 1H and 13C{1H} NMR spectra of the copolymers. Spatial coupling of different types of protons are resolved by 2D NOESY NMR spectra. The configurational and compositional sequences of ?-methylene carbons are assigned upto tetrad level whereas methine carbon is assigned as triad level of compositional sequences. The quaternary carbon of styrene and carbonyl carbon of isobornyl acrylate have been assigned as triad level of compositional sequences and are further confirmed by 2D HMBC NMR spectra.

Khandelwal, Deepika; Hooda, Sunita; Brar, A. S.; Shankar, Ravi

2013-10-01

364

Recent developments and applications of saturation transfer difference nuclear magnetic resonance (STD NMR) spectroscopy.  

PubMed

This review aims to illustrate that STD NMR is not simply a method for drug screening and discovery, but has qualitative and quantitative applications that can answer fundamental and applied biological and biomedical questions involving molecular interactions between ligands and proteins. We begin with a basic introduction to the technique of STD NMR and report on recent advances and biological applications of STD including studies to follow the interactions of non-steroidal anti-inflammatories, minimum binding requirements for virus infection and understating inhibition of amyloid fibre formation. We expand on this introduction by reporting recent STD NMR studies of live-cell receptor systems, new methodologies using scanning STD, magic-angle spinning STD and approaches to use STD NMR in a quantitative fashion for dissociation constants and group epitope mapping (GEM) determination. We finish by outlining new approaches that have potential to influence future applications of the technique; NMR isotope-editing, heteronuclear multidimensional STD and (19)F STD methods that are becoming more amenable due to the latest NMR equipment technologies. PMID:23232937

Wagstaff, Jane L; Taylor, Samantha L; Howard, Mark J

2013-04-01

365

Diffusion of small solutes in cartilage as measured by nuclear magnetic resonance (NMR) spectroscopy and imaging.  

PubMed

The ability of water and solutes to move through the cartilage matrix is important to the normal function of cartilage and is presumed to be altered in degenerative diseases of cartilage such as osteoarthritis and rheumatoid arthritis. Nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) techniques were used to measure a self diffusion coefficient (D) for small solutes in samples of explanted cartilage for diffusion times ranging from 13 ms to 2 s. With a diffusion time of 13 ms, the intratissue diffusivity of several small solutes (water, Na+, Li+, and CF3CO2-) was found consistently to be about 60% of the diffusivity of the same species in free solution. Equilibration of the samples at low pH (which titrates the charge groups so that the net matrix charge of -300 mM at pH 8 becomes approximately -50 mM at pH 2) did not affect the diffusivity of water or Na+. These data, and the similarity between the D in cartilage relative to free solution for water, anions, and cations, are consistent with the view that charge is not an important determinant of the intratissue diffusivity of small solutes in cartilage. With 35% compression, the diffusivity of water and Li+ dropped by 19 and 39%, respectively. In contrast, the diffusivity of water increased by 20% after treatment with trypsin (to remove the proteoglycans and noncollagenous proteins). These data and the lack of an effect of charge on diffusivity are consistent with D being dependent on the composition and density of the solid tissue matrix. A series of diffusion-weighted proton images demonstrated that D could be measured on a localized basis and that changes in D associated with an enzymatically depleted matrix could be clearly observed. Finally, evidence of restriction to diffusion within the tissue was found with studies in which D was measured as a function of diffusion time. The measured D for water in cartilage decreased with diffusion times ranging from 25 ms to 2 s, at which point the measured D was roughly 40% of the diffusivity in free solution. Although changes in matrix density by compression or digestion with trypsin led to a decrease or increase, respectively, in the measured D, the functional change in measured diffusivity with diffusion time remained essentially unchanged. In a different type of study, in which bulk transport could be observed over long periods of time, cartilage was submerged in 99% D2O and MRI studies were performed to demonstrate the bulk movement of water out of the cartilage matrix.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:8340820

Burstein, D; Gray, M L; Hartman, A L; Gipe, R; Foy, B D

1993-07-01

366

Hydrogen bonding pattern in N-benzoyl(- DL-)- L-phenylalanines as revealed by solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The nature of the hydrogen bonding pattern has been investigated in N-benzoyl- DL-phenylalanine ( 1) and N-benzoyl- L-phenylalanine ( 2) polymorphes by solid-state NMR spectroscopy. It has been shown that the multiple resonances of carboxyl carbon in 2 are directly connected to different types of hydrogen bonding. The differences in intermolecular distances of carboxyl groups involved in different types of hydrogen bonding have been visualized by the 2D exchange and 1D ODESSA experiments. Potential applications of such a new approach include the exploration of intermolecular distances in hydrogen bonded compounds with singly labeled biomolecules.

Potrzebowski, M. J.; Schneider, C.; Tekely, P.

1999-11-01

367

Molecular recognition of rosmarinic acid from Salvia?sclareoides extracts by acetylcholinesterase: a new binding site detected by NMR spectroscopy.  

PubMed

Acetylcholinesterase (AChE) inhibition is one of the most currently available therapies for the management of Alzheimer's disease (AD) symptoms. In this context, NMR spectroscopy binding studies were accomplished to explain the inhibition of AChE activity by Salvia sclareoides extracts. HPLC-MS analyses of the acetone, butanol and water extracts eluted with methanol and acidified water showed that rosmarinic acid is present in all the studied samples and is a major constituent of butanol and water extracts. Moreover, luteolin 4'-O-glucoside, luteolin 3',7-di-O-glucoside and luteolin 7-O-(6''-O-acetylglucoside) were identified by MS(2) and MS(3) data acquired during the LC-MS(n) runs. Quantification of rosmarinic acid by HPLC with diode-array detection (DAD) showed that the butanol extract is the richest one in this component (134??g?mg(-1) extract). Saturation transfer difference (STD) NMR spectroscopy binding experiments of S. sclareoides crude extracts in the presence of AChE in buffer solution determined rosmarinic acid as the only explicit binder for AChE. Furthermore, the binding epitope and the AChE-bound conformation of rosmarinic acid were further elucidated by STD and transferred NOE effect (trNOESY) experiments. As a control, NMR spectroscopy binding experiments were also carried out with pure rosmarinic acid, thus confirming the specific interaction and inhibition of this compound against AChE. The binding site of AChE for rosmarinic acid was also investigated by STD-based competition binding experiments using Donepezil, a drug currently used to treat AD, as a reference. These competition experiments demonstrated that rosmarinic acid does not compete with Donepezil for the same binding site. A 3D model of the molecular complex has been proposed. Therefore, the combination of the NMR spectroscopy based data with molecular modelling has permitted us to detect a new binding site in AChE, which could be used for future drug development. PMID:23536497

Marcelo, Filipa; Dias, Catarina; Martins, Alice; Madeira, Paulo J; Jorge, Tiago; Florêncio, M Helena; Cañada, F Javier; Cabrita, Eurico J; Jiménez-Barbero, Jesús; Rauter, Amélia P

2013-05-17

368

Probing transient conformational states of proteins by solid-state R(1?) 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

369

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

370

The development and application of non-adiabtic rapid sweep electron paramagnetic resonance spectroscopy and interspin distance determination at L-band  

NASA Astrophysics Data System (ADS)

A continuous wave (CW) electron paramagnetic resonance (EPR) spectrum is typically displayed as the first harmonic response to the application of 100 kHz magnetic field modulation followed by a phase sensitive detector (PSD). Field modulation is used to enhance sensitivity by transferring the signal to harmonics of the modulation frequency. However, magnetic field modulation of any amplitude causes spectral broadening and sacrifices EPR spectral intensity by a minimum factor of two. In the first part of this work, a new CW rapid-scan spectroscopic technique that avoids these compromises is developed. This technique, termed non-adiabatic rapid sweep (NARS) EPR, consists of repetitively sweeping the magnetic field linearly through a spectral fragment at a rate that is sufficiently high to overcome receiver noise, microwave phase noise, and environmental microphonics, but is sufficiently slow to avoid adiabatic rapid passage. Under these conditions, thermal equilibrium is maintained and undistorted pure absorption responses are collected. NARS nitroxide spectra were collected at X-band using the optimized instrumental parameters determined by preliminary studies. Spectra were collected in segments using the overlapped regions of each segment to align fragments and an off-resonance background subtraction to correct any baseline offsets. The technique was validated by comparing the spectra to integrated CW spectra collected using low field modulation amplitudes over three orders of magnitude in rotational correlation time. The two sets of spectra were found to be in excellent agreement, suggesting NARS is suitable for any lineshape or linewidth over a short magnetic field range. Attempts to assemble a complete nitroxide spectrum at L-band using the initial NARS spectral construction method developed at X-band were unsuccessful. This was a consequence of higher eddy current distortion due the differences in resonator design between the frequencies. The problem is exacerbated by Lorentz forces produced by the cross product of the eddy currents with H o, which resulted in a large baseline offset. Consequently, a new spectral collection method that addressed the baseline and spectral assembly problem was developed in Chapter Two to collect undistorted NARS L-band spectra and utilized to test the distance determination hypothesis in Chapter Three. The new acquisition method was initially developed and applied to collect a copper (II) imidazole (CuIm) spectrum. CuIm was chosen as a model system because of its wide spectral width (800 G) and disparate spectral linewidths (8-40 G). Successful collection of this spectrum was thought to ensure the applicability of the new technique over any spectral width and at any microwave frequency. Copper spectra are traditionally displayed as the derivative-like first harmonic response. Since NARS spectroscopy produces pure absorption spectra, the desired spectral display was computed using pseudomodulation. A conventional CW spectrum of the same sample and orientation was shown to be in remarkably good agreement with the pseudomodulated NARS spectrum with similar modulation amplitude. The application of different pseudomodulation amplitudes provided insight into different spectral features since large modulation amplitudes increase the intensity of broad features while small modulation amplitudes allow observation of more detailed hyperfine structures. To achieve this with conventional CW techniques, several experiments must be performed, and, in some instances, cannot be performed due to the restrictions of the spectrometer. (Abstract shortened by UMI.)

Kittell, Aaron W.

371

Estimation of the age of human bloodstains by electron paramagnetic resonance spectroscopy: Long-term controlled experiment on the effects of environmental factors  

Microsoft Academic Search

In this study, we examined the efficacy and limitations of electron paramagnetic resonance (EPR) for estimating the age of human bloodstains. At 77K, human bloodstains give four striking EPR signals in the g=6.2 (g6), 4.3 (g4), 2.27 (H) and 2.005 (R) regions due to ferric high-spin, ferric non-heme, ferric low-spin and free radical species, respectively. We found that plotting double

Yoshihiko Fujita; Koichiro Tsuchiya; Shinji Abe; Yoshiharu Takiguchi; Shin-ichi Kubo; Hiromu Sakurai

2005-01-01

372

Incorporation of phosphorus guest ions in the calcium silicate phases of Portland cement from 31P MAS NMR spectroscopy.  

PubMed

Portland cements may contain small quantities of phosphorus (typically below 0.5 wt % P(2)O(5)), originating from either the raw materials or alternative sources of fuel used to heat the cement kilns. This work reports the first (31)P MAS NMR study of anhydrous and hydrated Portland cements that focuses on the phase and site preferences of the (PO(4))(3-) guest ions in the main clinker phases and hydration products. The observed (31)P chemical shifts (10 to -2 ppm), the (31)P chemical shift anisotropy, and the resemblance of the lineshapes in the (31)P and (29)Si MAS NMR spectra strongly suggest that (PO(4))(3-) units are incorporated in the calcium silicate phases, alite (Ca(3)SiO(5)) and belite (Ca(2)SiO(4)), by substitution for (SiO(4))(4-) tetrahedra. This assignment is further supported by a determination of the spin-lattice relaxation times for (31)P in alite and belite, which exhibit the same ratio as observed for the corresponding (29)Si relaxation times. From simulations of the intensities, observed in inversion-recovery spectra for a white Portland cement, it is deduced that 1.3% and 2.1% of the Si sites in alite and belite, respectively, are replaced by phosphorus. Charge balance may potentially be achieved to some extent by a coupled substitution mechanism where Ca(2+) is replaced by Fe(3+) ions, which may account for the interaction of the (31)P spins with paramagnetic Fe(3+) ions as observed for the ordinary Portland cements. A minor fraction of phosphorus may also be present in the separate phase Ca(3)(PO(4))(2), as indicated by the observation of a narrow resonance at delta((31)P) = 3.0 ppm for two of the studied cements. (31)P{(1)H} CP/MAS NMR spectra following the hydration of a white Portland cement show that the resonances from the hydrous phosphate species fall in the same spectral range as observed for (PO(4))(3-) incorporated in alite. This similarity and the absence of a large (31)P chemical shift ansitropy indicate that the hydrous (PO(4))(3-) species are incorporated in the interlayers of the calcium-silicate-hydrate (C-S-H) phase, the principal phase formed upon hydration of alite and belite. PMID:20481523

Poulsen, Søren L; Jakobsen, Hans J; Skibsted, Jørgen

2010-06-21

373

Advancing fragment binders to lead-like compounds using ligand and protein-based NMR spectroscopy.  

PubMed

The application of NMR in fragment-based lead discovery (FBLD) has quickly developed from a sensitive method for the identification of low-affinity binders to an important tool in the hit-to-lead process. NMR can play a constructive role in the process from identifying those fragments with the best potential toward a biochemically active compound to developing them into molecules with high affinity and selectivity to a given target protein. NMR hit-to-lead involves revising the lead identification process at the beginning of a fragment-based drug discovery project, the primary screen, and also looking toward protein-detected NMR methods in advancing compounds from fragment hit into and through fragment hit-to-lead. With the development of higher sensitivity cold NMR probes, ligand-based NMR methods can be successfully applied to a majority of projects found in a pharmaceutical pipeline. Having matured from the original concepts such as SAR by NMR (Shuker, S. B., Hajduk, P. J., Meadows, R. P., Fesik, S. W. (1996) Discovering high-affinity ligands for proteins: SAR by NMR. Science274 (5292), 1531-1534.), projects that base their lead matter on fragment hits are close to or already in the clinic (Woodhead, A. J., Angove, H., Carr, M. G., Chessari, G., Congreve, M., Coyle, J. E., Cosme, J., Graham, B., Day, P. J., Downham, R., Fazal, L., Feltell, R., et al. (2010) discovery of (2,4-dihydroxy-5-isopropylphenyl)-[5-(4-methylpiperazin-1-ylmethyl)-1,3-dihydroisoindol-2-yl]methanone (AT13387), a novel inhibitor of the molecular chaperone Hsp90 by fragment based drug design. J. Med. Chem.53, 5956-5969, Chessari, G., and Woodhead, A. J. (2009). From fragment to clinical candidate: A historical perspective. Drug Discov. Today14 (13-14), 668-675.). Generating new ideas toward new binding modes and mechanisms of action as well as new intellectual property will be the standard by which the success of FBLD will need to be measured. A strategy outlining the various steps involved in NMR hit-to-lead is provided. By means of a specific example, the workflow is described to guide the reader through the experimental setup. PMID:21371602

Maurer, Till

2011-01-01

374

Metabolic Discrimination of Catharanthus roseus Leaves Infected by Phytoplasma Using 1H-NMR Spectroscopy and Multivariate Data Analysis1  

PubMed Central

A comprehensive metabolomic profiling of Catharanthus roseus L. G. Don infected by 10 types of phytoplasmas was carried out using one-dimensional and two-dimensional NMR spectroscopy followed by principal component analysis (PCA), an unsupervised clustering method requiring no knowledge of the data set and used to reduce the dimensionality of multivariate data while preserving most of the variance within it. With a combination of these techniques, we were able to identify those metabolites that were present in different levels in phytoplasma-infected C. roseus leaves than in healthy ones. The infection by phytoplasma in C. roseus leaves causes an increase of metabolites related to the biosynthetic pathways of phenylpropanoids or terpenoid indole alkaloids: chlorogenic acid, loganic acid, secologanin, and vindoline. Furthermore, higher abundance of Glc, Glu, polyphenols, succinic acid, and Suc were detected in the phytoplasma-infected leaves. The PCA of the 1H-NMR signals of healthy and phytoplasma-infected C. roseus leaves shows that these metabolites are major discriminating factors to characterize the phytoplasma-infected C. roseus leaves from healthy ones. Based on the NMR and PCA analysis, it might be suggested that the biosynthetic pathway of terpenoid indole alkaloids, together with that of phenylpropanoids, is stimulated by the infection of phytoplasma. PMID:15286294

Choi, Young Hae; Tapias, Elisabet Casas; Kim, Hye Kyong; Lefeber, Alfons W.M.; Erkelens, Cornelis; Verhoeven, Jacobus Th.J.; Brzin, Jernej; Zel, Jana; Verpoorte, Robert

2004-01-01

375

Taurine - a possible fingerprint biomarker in non-muscle invasive bladder cancer: A pilot study by 1H NMR spectroscopy.  

PubMed

Urinary bladder cancer is a major epidemiological problem that continues to grow each year. It opens avenues for investigative research for the identification of new disease markers and diagnostic techniques. In this pilot study, utility of non-invasive (1)H NMR spectroscopy has been evaluated for probing the metabolic perturbations occurring in non-muscle invasive urinary bladder cancer. (1)H NMR spectra of urine of bladder cancer patients and controls (healthy and urinary tract infection/bladder stone) (n = 103) were acquired at 400MHz. The non-overlapping resonances of citrate, dimethylamine, phenylalanine, taurine and hippurate were first identified and then quantitated by (1)H NMR spectra, with respect to an external reference sodium-3-trimethylsilylpropionate (TSP). The concentrations of these metabolites were then statistically analyzed. The cancer patients showed significant (p < 0.05) variations in concentration of hippurate and citrate as compared with healthy controls and benign controls. The significant elevation in concentration of taurine was observed in urine of bladder cancer patients, which was below the sensitivity limit of 400MHz in control cases. However, stages Ta, T1 and carcinoma in situ (CIS) cannot be differentiated on the basis of altered metabolite indices but their composition may reflect the biochemical alterations in metabolism of cancer cells. PMID:20164538

Srivastava, Shatakshi; Roy, Raja; Singh, Sudhir; Kumar, Praveen; Dalela, Diwakar; Sankhwar, Satya N; Goel, Apul; Sonkar, Abhinav A

2010-01-01

376

Multinuclear nanoliter one-dimensional and two-dimensional NMR spectroscopy with a single non-resonant microcoil.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique, but its low sensitivity and highly sophisticated, costly, equipment severely constrain more widespread applications. Here we show that a non-resonant planar transceiver microcoil integrated in a microfluidic chip (detection volume 25?nl) can detect different nuclides in the full broad-band range of Larmor frequencies (at 9.4?T from 61 to 400?MHz). Routine one-dimensional (1D) and two-dimensional (2D), homo- and heteronuclear experiments can be carried out using the broad-band coil set-up. Noteworthy, heteronuclear 2D experiments can be performed in a straightforward manner on virtually any combination of nuclides (from classical ¹H-¹³C to more exotic combinations like ¹?F-³¹P) both in coupled and decoupled mode. Importantly, the concept of a non-resonant system provides magnetic field-independent NMR probes; moreover, the small-volume alleviates problems related to field inhomogeneity, making the broad-band coil an attractive option for, for example, portable and table-top NMR systems. PMID:24394755

Fratila, Raluca M; Gomez, M Victoria; Sýkora, Stanislav; Velders, Aldrik H

2014-01-01

377

Multinuclear nanoliter one-dimensional and two-dimensional NMR spectroscopy with a single non-resonant microcoil  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique, but its low sensitivity and highly sophisticated, costly, equipment severely constrain more widespread applications. Here we show that a non-resonant planar transceiver microcoil integrated in a microfluidic chip (detection volume 25?nl) can detect different nuclides in the full broad-band range of Larmor frequencies (at 9.4?T from 61 to 400?MHz). Routine one-dimensional (1D) and two-dimensional (2D), homo- and heteronuclear experiments can be carried out using the broad-band coil set-up. Noteworthy, heteronuclear 2D experiments can be performed in a straightforward manner on virtually any combination of nuclides (from classical 1H-13C to more exotic combinations like 19F-31P) both in coupled and decoupled mode. Importantly, the concept of a non-resonant system provides magnetic field-independent NMR probes; moreover, the small-volume alleviates problems related to field inhomogeneity, making the broad-band coil an attractive option for, for example, portable and table-top NMR systems.

Fratila, Raluca M.; Gomez, M. Victoria; Sýkora, Stanislav; Velders, Aldrik H.

2014-01-01

378

Order and dynamics of a liquid crystalline dendrimer by means of 2H NMR spectroscopy.  

PubMed

A complete Deuterium NMR study performed on partially deuterated liquid crystalline carbosilane dendrimer is here reported. The dendrimer under investigation shows a SmA phase in a large temperature range from 381 to 293 K, and its mesophasic properties have been previously determined. However, in this work the occurrence of a biphasic region between the isotropic and SmA phases has been put in evidence. The orientational order of the dendrimer, labeled on its lateral mesogenic units, is here evaluated in the whole temperature range by means of (2)H NMR, revealing a peculiar trend at low temperatures (T < 326 K). This aspect has been further investigated by a detailed analysis of the (2)H NMR spectral features, such as the quadrupolar splitting, the line shape, and the line-width, as a function of temperature. In the context of a detailed NMR analysis, relaxation times (T(1) and T(2)) have also been measured, pointing out a slowing down of the dynamics by decreasing the temperature, which determines from one side the spectral changes observed in the NMR spectra, on the other the observation of a minimum in the T(1). PMID:18956837

Domenici, Valentina; Cifelli, Mario; Veracini, Carlo Alberto; Boiko, Natalia I; Agina, Elena V; Shibaev, Valery P

2008-11-27

379

An investigation into the effect of potassium ions on the folding of silk fibroin studied by generalized two-dimensional NMR-NMR correlation and Raman spectroscopy.  

PubMed

We used generalized two-dimensional NMR-NMR correlation to examine the effect of potassium ions on the conformation transition in silk fibroin to investigate the possibility that the fairly high K+ ion content found in the distal end of silk-secreting ducts in the silkworms could have a bearing on natural formation of the silk fiber. This has enabled us to propose a detailed mechanism for the transition process. Our evidence indicates that increasing the [K+] from 0 to 3.7 mg.g(-1) in the silk fibroin, as is thought to occur as the silk fibroin moves through the secretory pathway to the spigot, produces a sequence of secondary structural changes: helix and/or random coil-->helix-like-->beta-sheet-like-->beta-sheet. The sequence is the same as that produced in silk fibroin films by decreasing the pH of fibroin from 6.8 to 4.8. In addition, we used Raman spectroscopy to study the effect of K+ ions on the Fermi doublet resonance of the tyrosyl phenolic ring at 850 and 830 cm(-1). The intensity ratio I(850)/I(830) at these wave numbers indicated that the hydrogen bonding formed by the tyrosyl phenolic-OH becomes more stable with an increase in the K+ ion concentration as above. Our investigation on the effect of K+ ions on fibroin may help provide a theoretical basis for understanding the natural silk-spinning process and the conditions required for biomimetic spinning. It may also have relevance to the aggregation of other beta-sheet proteins, including prion proteins, neurofibrillary proteins and amyloid plaques. PMID:18081855

Ruan, Qing-Xia; Zhou, Ping; Hu, Bing-Wen; Ji, Dan

2008-01-01

380

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

NASA Astrophysics Data System (ADS)

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

Cozar, O.; Filip, C.; Cioica, N.; Coţa, C.; Tripon, C.; Nagy, E. M.

2013-11-01

381

Structure of the O-deacetylated glucuronoxylomannan from Cryptococcus neoformans serotype C as determined by 2D 1H NMR spectroscopy  

Microsoft Academic Search

The primary structure of the O-deacetylated capsular glucuronoxylomannan (GXM) isolated from Cryptococcus neoformans serotype C was investigated by 2D NMR spectroscopy. Assignment of the 1H NMR chemical shifts for the polysaccharide was accomplished from the analysis of DQF-COSY, TOCSY, NOESY and\\/or ROESY spectra of three isolates (298, 34, and 401). These isolates contain the same polysaccharide glycosyl residues but in

Bradley E. Bacon; Robert Cherniak

1995-01-01

382

Magneto-optical contrast in liquid-state optically-detected NMR spectroscopy  

NASA Astrophysics Data System (ADS)

We use optical Faraday rotation (OFR) to probe nuclear spins in real time at high-magnetic field in a range of diamagnetic sample fluids [1]. This technique is shown to speciate functional groups with the same chemical shifts as is seen in conventional NMR, however, the intensities of the OFR-NMR peaks are influenced by optical detuning and hyperfine couplings. We investigate protons at chemically-distinct sites and other lower-gyromagnetic-ratio nuclei including carbon, fluorine and phosphorous [2]. Binary mixtures for protonated systems were also tested and the results suggest that the present approach is sensitive to the solvent-solute dynamics in ways complementary to those known in inductive NMR. [4pt] [1] D. Pagliero, W. Dong, D. Sakellariou and C. A. Meriles. J. Chem. Phys. 133, 154505 (2010). [0pt] [2] D. Pagliero and C. A. Meriles. Proc. Natl. Aca. Sci. USA (2011) in press.

Pagliero, Daniela; Meriles, Carlos

2012-02-01

383

An Active Photoreceptor Intermediate Revealed by In Situ Photoirradiated Solid-State NMR Spectroscopy  

PubMed Central

A novel, to our knowledge, in situ photoirradiation system for solid-state NMR measurements is improved and demonstrated to successfully identify the M-photointermediate of pharaonis phoborhodopsin (ppR or sensory rhodopsin II), that of the complex with transducer (ppR/pHtrII), and T204A mutant embedded in a model membrane. The 13C NMR signals from [20-13C]retinal-ppR and ppR/pHtrII revealed that multiple M-intermediates with 13-cis, 15-anti retinal configuration coexisted under the continuously photoirradiated condition. NMR signals observed from the photoactivated retinal provide insights into the process of photocycle in the ppR/pHtrII complex. PMID:22098758

Tomonaga, Yuya; Hidaka, Tetsurou; Kawamura, Izuru; Nishio, Takudo; Ohsawa, Kazuhiro; Okitsu, Takashi; Wada, Akimori; Sudo, Yuki; Kamo, Naoki; Ramamoorthy, Ayyalusamy; Naito, Akira

2011-01-01

384

Hydrogenation of Carbon Dioxide Catalyzed by Ruthenium Trimethylphosphine Complexes: A Mechanistic Investigation using High-Pressure NMR Spectroscopy  

SciTech Connect

The previously reported complex, cis-(PMe3)4RuCl(OAc) (1) acts as a catalyst for CO2 hydrogenation into formic acid in the presence of a base and an alcohol co-catalyst. NMR spectroscopy has revealed that 1 exists in solution in equilibrium with fac-(PMe3)3RuCl(h2-OAc) (2), [(PMe3)4Ru(h2-OAc)]Cl (3a), and free PMe3. Complex 2 has been isolated and characterized by elemental analysis, NMR spectroscopy, and X-ray crystallography. 2 has been tested as a CO2 hydrogenation catalyst, however, it performed poorly under the conditions of catalysis used for 1. Complex 3a can be prepared by adding certain alcohols, such as MeOH, EtOH, or o-C6H5OH, to a solution of 1 in CDCl3. The chloride ion of 3a has been exchanged for the non-coordinating anions BPh4 or B(ArF )4 (B(ArF)4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) to produce [(PMe3)4Ru(h2-OAc)]BPh4 (3b) and [(PMe3)4Ru(h2-OAc)]B(ArF)4 (3c). Both of these complexes have been isolated and characterized by elemental analysis, NMR spectroscopy, and in the case of 3b, X-ray crystallography. Complexes 3b and 3c perform just as well as 1 for CO2 hydrogenation to formic acid in the presence of an alcohol co-catalyst; however, 3b,c perform equally well without the added alcohol. High-pressure NMR has been used to investigate the mechanism of CO2 hydrogenation via 3a,b in the presence of base. Two of the intermediates involved have been identified as cis-(PMe3)4RuH2 (5) and cis-(PMe3)4Ru(H)O2CH (6), and the role of the base includes not only trapping of the formic acid product, but also initiation of the catalysis by aiding the conversion of 3b,c to 5.

Getty, April D.; Tai, Chih-Cheng; Linehan, John C.; Jessop, Philip G.; Olmstead, Marilyn M.; Rheingold, Arnold

2009-08-26

385

Interaction of purine nucleotides with inert paramagnetic Cr(III) probes evaluated by NMR relaxation effects. Molecular mechanics calculations on Cr(III) and Co(III) polyphosphate complexes.  

PubMed

The 1H NMR relaxation effects produced by paramagnetic Cr(III) complexes on nucleoside 5'-mono- and -triphosphates in D2O solution at pH' = 3 were measured. The paramagnetic probes were [Cr(III)(H2O)6]3+, [Cr(III)(H2O)3(HATP)], [Cr(III)(H2O)3(HCTP)] and [Cr(III)(H2O)3(UTP)-, while the matrix nucleotides (0.1 M) were H2AMP, HIMP-, and H2ATP2-. For the aromatic base protons, the ratios of the transverse to longitudinal paramagnetic relaxation rates (R2p/R1p) for the [Cr(III)(H2O)6]3+/H2ATP2-, [Cr(III)(H2O)3(HATP)]/H2ATP2-, [Cr(III)(H2O)3(HCTP)]/H2ATP2 and [Cr(III)(H2O)3(UTP)]-/H2ATP2 systems were below 2.33 so the dipolar term predominates. For a given nucleotide, R1p for the purine H(8) signal was larger than for the H(2) signal with the [Cr(III)(H2O)6]3+ probe, while R1p for the H(2) signal was larger with all the other Cr(III) probes. Molecular mechanics computations on the [Cr(III)(H2O)4(HPP)(alpha,beta)], [Cr(III)(NH3)4(HPP)(alpha,beta)], [Co(III)(NH3)3(H2PPP)(alpha,beta,gamma)] and [Co(III)(NH3)4(HPP)(alpha,beta)] complexes gave calculated energy-minimized geometries in good agreement with those reported in crystal structures. The molecular mechanics force constants found were then used to calculate the geometry of the inner sphere [Cr(III)(H2O)6]3+ and [Cr(III)(H2O)3(HATP)(alpha,beta,gamma)] complexes as well as the structures of the outer sphere [Cr(III)(H2O)6]3(+)-(H2AMP) and [Cr(III)(H2O)6]-(HIMP)- species. The gas-phase structure of the [Cr(III)(H2O)3(HATP)(alpha,beta,gamma)] complex shows the existence of a hydrogen bond interaction between a water ligand and the adenine N(7)(O...N = 2.82 A). The structure is also stabilized by intramolecular hydrogen bonds involving the -O(2')H group and the adenine N(3) (O...N = 2.80 A) as well as phosphate oxygen atoms and a water molecule (O...O = 2.47 A). The metal center has an almost regular octahedral coordination geometry. The structures of the two outer-sphere species reveal that the phosphate group interacts strongly with the hexa-aquochromium probe. In both complexes, the nucleotides have a similar "anti" conformation around the N(9)-C(1') glycosidic bond. However, a very important difference characterizes the two structures. For the (HIMP)- complex, strong hydrogen bond interactions exist between one and two water ligands and the inosine N(7) and O(6) atoms, respectively (O...O = 2.63 A; O...N = 2.72, 2.70 A). For the H2AMP complex, the [Cr(III)(H2O)6]3+ cation does not interact with N(7) since it is far from the purine system. Hydrogen bonds occur between water ligands and phosphate oxygens. The Cr-H(8) and Cr-H(2) distances revealed by the energy-minimized geometries for the two outer sphere species were used to calculate the R1p values for the H(8) and H(2) signals for comparison with the observed R1p values: 0.92(c), 1.04(ob) (H(8)) and 0.06(c), 0.35(ob) (H(2)) for H2AMP; and 3.76(c), 4.53(ob) (H(8)) and 0.16(c), 0.77(ob) s-1 (H(2)) for HIMP-.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2310520

Cini, R; Giorgi, G; Laschi, F; Rossi, C; Marzilli, L G

1990-02-01

386

Evolution of the dynamic susceptibility in molecular glass formers: Results from light scattering, dielectric spectroscopy, and NMR  

NASA Astrophysics Data System (ADS)

Although broadly studied, molecular glass formers are not well investigated above their melting point. Correlation times down to 10-12 s are easily accessible when studying low-Tg systems by depolarized light scattering, employing a tandem-Fabry-Perot interferometer and a double monochromator. When combining these techniques with state-of-the-art photon correlation spectroscopy (PCS), broad band susceptibility spectra become accessible which can compete with those of dielectric spectroscopy (DS). Comparing the results with those from DS, optical Kerr effect, and NMR, we describe the evolution of the susceptibilities starting from the boiling point Tb down to Tg, i.e., from simple liquid to glassy dynamics. Special attention is given to the emergence of the excess wing contribution which is also probed by PCS and which signals a crossover of the spectral evolution. The process is attributed to a small-angle precursor process of the ?-relaxation, and the apparent probe dependent stretching of the ?-process is explained by a probe dependent contribution of the excess wing. Upon cooling, its emergence is linked to a strong decrease of the strength of the fast dynamics which is taken as reorientational analog of the anomaly of the Debye-Waller factor. Many glass formers show in addition a slow ?-process which manifests itself rather universally in NMR, in DS, however, with different amplitudes, but not at all in PCS experiments. Finally, a three-parameter function is discussed interpolating ??(T) from Tb to Tg by connecting high- and low-temperature dynamics.

Petzold, N.; Schmidtke, B.; Kahlau, R.; Bock, D.; Meier, R.; Micko, B.; Kruk, D.; Rössler, E. A.

2013-03-01

387

Characterization of bio-oil from hydrothermal liquefaction of organic waste by NMR spectroscopy and FTICR mass spectrometry.  

PubMed

Solid wastes of organic origins are potential feedstocks for the production of liquid biofuels, which could be suitable alternatives to fossil fuels for the transport and heating sectors, as well as for industrial use. By hydrothermal liquefaction, the wet biomass is partially transformed into a water-immiscible, oil-like organic matter called bio-oil. In this study, an integrated NMR spectroscopy/mass spectrometry approach has been developed for the characterization of the hydrothermal liquefaction of bio-oil at the molecular level. (1)H and (13)C NMR spectroscopy were used for the identification of functional groups and gauging the aromatic carbon content in the mixture. GC-MS analysis revealed that the volatile fraction was rich in fatty acids, as well as in amides and esters. High-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) has been applied in a systematic way to fully categorize the bio-oil in terms of different classes of components, according to their molecular formulas. Most importantly, for the first time, by using this technique, and for the liquefaction bio-oil characterization in particular, FT-MS data have been used to develop a methodology for the determination of the aromatic versus aliphatic carbon and nitrogen content. It is well known that, because they resist hydrogenation and represent sources of polluting species, both aromatic molecules and nitrogen-containing species raise concerns for subsequent upgrading of bio-oil into a diesel-like fuel. PMID:23139164

Leonardis, Irene; Chiaberge, Stefano; Fiorani, Tiziana; Spera, Silvia; Battistel, Ezio; Bosetti, Aldo; Cesti, Pietro; Reale, Samantha; De Angelis, Francesco

2013-01-01

388

Site-directed mutagenesis and high-resolution NMR spectroscopy of the active site of porphobilinogen deaminase  

SciTech Connect

The active site of porphobilinogen (PBG){sup 1} deaminase from Escherichia coli has been found to contain an unusual dipyrromethane derived from four molecules of 5-aminolevulinic acid (ALA) covalently linked to Cys-242, one of the two cysteine residues conserved in E. coli and human deaminase. By use of a hemA{sup {minus}} strain of E. coli the enzyme was enriched from (5-{sup 13}C)ALA and examined by {sup 1}H-detected multiple quantum coherence spectroscopy, which revealed all of the salient features of a dipyrromethane composed of two PBG units linked heat to tail and terminating in a CH{sub 2}-S bond to a cysteine residue. Site-specific mutagenesis of Cys-99 and Cys-242, respectively, has shown that substitution of Ser for Cys-99 does not affect the enzymatic activity, whereas substitution of Ser for Cys-242 removes essentially all of the catalytic activity as measured by the conversion of the substrate PBG to uro'gen I. The NMR spectrum of the covalent complex of deaminase with the suicide inhibitor 2-bromo-(2,11-{sup 13}C{sub 2})PBG reveals that the aminomethyl terminus of the inhibitor reacts with the enzyme's cofactor at the {alpha}-free pyrrole. NMR spectroscopy of the ES{sub 2} complex confirmed a PBG-derived head-to-tail dipyrromethane attached to the {alpha}-free pyrrole position of the enzyme. A mechanistic rationale for deaminase is presented.

Scott, A.I.; Roessner, C.A.; Stolowich, N.J.; Karuso, P.; Williams, H.J.; Grant, S.K.; Gonzalez, M.D.; Hoshino, T. (Texas A M Univ., College Station (USA))

1988-10-18

389

Photoisomerization and structural dynamics of two nitrosylruthenium complexes: a joint study by NMR and nonlinear IR spectroscopies.  

PubMed

In this work, the photoisomerization and structural dynamics of two isomeric nitrosylruthenium(ii) complexes [Ru(OAc)(2cqn)2NO] (H2cqn = 2-chloro-8-quinolinol) in CDCl3 and DMSO are examined using NMR and IR spectroscopic methods. The two N atoms in the 2cqn ligand are in trans position in the synthesized cis-1 isomer, while they are in cis position in the cis-2 isomer. Kinetics monitored by NMR spectroscopy shows that the rate constant of photoisomerization from cis-2 to cis-1 isomer depends on the wavelength of irradiation and solvent polarity; it proceeds faster on irradiating near the absorption peak in the UV-Vis region, and also in more polar solvents (DMSO). Density functional theory computation indicates that the peculiarity of [Ru(ii)-NO(+)] group affects the structure and reactivity of the nitrosylruthenium complexes. Using the nitrosyl stretching (?NO) to be vibrational probe, the structural dynamics and structural distributions of the cis-1 and cis-2 isomers are examined by steady-state linear infrared and ultrafast two-dimensional infrared (2D IR) spectroscopies. The structural and photochemical aspects of the observed spectroscopic parameters are discussed in terms of solute-solvent interactions for the two nitrosylruthenium complexes. PMID:25285659

Wang, Jianru; Yang, Fan; Zhao, Yan; Yu, Pengyun; Qiao, Xiaoyan; Wang, Jianping; Wang, Hongfei

2014-11-21

390

Determination of analyte concentration using the residual solvent resonance in (1)H NMR spectroscopy.  

PubMed

An NMR protocol that uses the residual proton signal from DMSO -d(6) (i.e., DMSO -d(5)) to determine the concentration of an analyte in a NMR sample was developed. This technique provides an alternative method for determining the molar concentration of compounds in solution without prior knowledge of their molecular weight. The method is particularly useful when submilligram quantities of compound are to be analyzed and is applicable to a variety of different research areas such as compound management, and natural product, combinatorial, and medicinal chemistry. PMID:18393462

Pierens, Gregory K; Carroll, Anthony R; Davis, Rohan A; Palframan, Meredith E; Quinn, Ronald J

2008-05-01

391

Transformation of meta-stable calcium silicate hydrates to tobermorite: reaction kinetics and molecular structure from XRD and NMR spectroscopy.  

PubMed

Understanding the integrity of well-bore systems that are lined with Portland-based cements is critical to the successful storage of sequestered CO2 in gas and oil reservoirs. As a first step, we investigate reaction rates and mechanistic pathways for cement mineral growth in the absence of CO2 by coupling water chemistry with XRD and NMR spectroscopic data. We find that semi-crystalline calcium (alumino-)silicate hydrate (Al-CSH) forms as a precursor solid to the cement mineral tobermorite. Rate constants for tobermorite growth were found to be k = 0.6 (+/- 0.1) x 10(-5) s(-1) for a solution:solid of 10:1 and 1.6 (+/- 0.8) x 10(-4) s(-1) for a solution:solid of 5:1 (batch mode; T = 150 degrees C). This data indicates that reaction rates for tobermorite growth are faster when the solution volume is reduced by half, suggesting that rates are dependent on solution saturation and that the Gibbs free energy is the reaction driver. However, calculated solution saturation indexes for Al-CSH and tobermorite differ by less than one log unit, which is within the measured uncertainty. Based on this data, we consider both heterogeneous nucleation as the thermodynamic driver and internal restructuring as possible mechanistic pathways for growth. We also use NMR spectroscopy to characterize the site symmetry and bonding environment of Al and Si in a reacted tobermorite sample. We find two [4]Al coordination structures at delta iso = 59.9 ppm and 66.3 ppm with quadrupolar product parameters (PQ) of 0.21 MHz and 0.10 MHz (+/- 0.08) from 27Al 3Q-MAS NMR and speculate on the Al occupancy of framework sites by probing the protonation environment of Al metal centers using 27Al{1H}CP-MAS NMR. PMID:19144195

Houston, Jacqueline R; Maxwell, Robert S; Carroll, Susan A

2009-01-01

392

NMR Spectroscopy and Structural Characterization of Dithiophosphinates Relevant to Minor Actinide Extraction Processes  

SciTech Connect

Synthetic routes to alkyl and aryl substituted dithiophosphinate salts that contain non-coordinating PPh{sub 4}{sup 1+} counter cations are reported. In general, these compounds can be prepared via a multi-step procedure that starts with reacting secondary phosphines, i.e. HPR{sub 2}, with two equivalents elemental S. This transformation proceeds in two steps - first oxidation of the phosphine and second insertion of S into the H-P bond - and has been used to synthesize a series of dithiophoshinic acids, which were fully characterized, namely HS{sub 2}P(p-CF{sub 3}C{sub 6}H{sub 4}){sub 2}, HS{sub 2}P(m-CF{sub 3}C{sub 6}H{sub 4}){sub 2}, HS{sub 2}P(o-MeC{sub 6}H{sub 4}){sub 2}, and HS{sub 2}P(o-MeOC{sub 6}H{sub 4}){sub 2}. Although the insertion step was found to be much slower than the oxidation reaction, the formation of (NH{sub 4})S{sub 2}PR{sub 2} from HPSR{sub 2} occurs almost instantaneous upon addition of NH{sub 4}OH. Subsequent cation exchange reactions proceed readily with PPh{sub 4}Cl in water, under air, and at ambient conditions to provide analytically pure samples of [PPh{sub 4}][S{sub 2}PR{sub 2}] (R = p-CF{sub 3}C{sub 6}H{sub 4}, m-CF{sub 3}C{sub 6}H{sub 4}, o-CF{sub 3}C{sub 6}H{sub 4}, o-MeC{sub 6}H{sub 4}, o-MeOC{sub 6}H{sub 4}, Ph, and Me, 1b-7b, respectively), which were characterized by elemental analysis, multinuclear NMR, and IR spectroscopy. In addition the S{sub 2}PMe{sub 2}{sup 1-}, S{sub 2}PPh{sub 2}{sup 1-}, and dithiophosphinates with ortho-substituted arene rings were characterized by X-ray crystallography. Structural analysis show that, as opposed to the acids which have short P=S double bonds and long P-SH single bonds, the metric parameters for the S atoms in S{sub 2}PR{sub 2}{sup 1-} are equivalent. In addition, the presence of large non-coordinating PPh{sub 4}{sup 1+} cations guard against intermolecular P-S {hor_ellipsis} X interactions and insure that the P-S bond is isolated. Overall, this synthetic procedure provides high-purity S{sub 2}PR{sub 2}{sup 1-} compounds necessary for subsequent spectroscopic and theoretical studies.

Scott R. Daly; Kevin S. Boland; John R. Klaehn; Stosh A. Kozimor; Molly M. MacInnes; Dean R. Peterman; Brian L. Scott

2012-02-01

393

Self-Association of N-Methylacetamide Examined by Infrared and NMR Spectroscopies  

ERIC Educational Resources Information Center

These spectroscopic experiments investigate polarity and concentration effects on self-association behavior in N-methylacetamide. Inquiry can be limited to the concentration dependence of hydrogen bonding and estimation of dimerization constant (NMR studies) or to the effect of solvent polarity on extent of hydrogen bonding (IR studies). The…

Schenck, Heather L.; Hui, KaWai

2011-01-01

394

Determination of fluid density confined in nanopore by means of NMR spectroscopy  

NASA Astrophysics Data System (ADS)

We propose a new method, which determines the mean density of fluid confined in nanopore from the ratio of the NMR signals due to bulk and confined fluids. The present method is successfully applied to SF 6 confined in porous Vycor glass in a wide range of the fluid phase. The mean density in nanopore accounts for the behavior of the chemical shift.

Hiejima, Yusuke; Kanakubo, Mitsuhiro; Aizawa, Takafumi; Kurata, Yoshiaki; Ikushima, Yutaka

2005-06-01

395

Structural studies of methyl brevifolincarboxylate in solid state by means of NMR spectroscopy and DFT calculations  

Microsoft Academic Search

Methyl brevifolincarboxylate isolated from the herb of Potentilla argentea L. (Rosaceae) is a representative of the naturally occurring polyphenols. The compound is of pharmaceutical interest mainly because of its antiviral and antioxidant properties. 13C NMR spectra were recorded for solution and solid phase. 13C CPMAS spectra were assigned by comparison with solution data, dipolar dephasing and short contact time experiments.

Michal Wolniak; Michal Tomczyk; Jan Gudej; Iwona Wawer

2006-01-01

396

Dynamics and intramolecular ligand binding of DtxR studied by MD simulations and NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Diphtheria toxin repressor (DtxR) regulates the expression of the diphtheria toxin gene through intramolecular ligand binding (Wylie et al., Biochemistry 2005, 44:40-51). Protein dynamics is essential to the binding process of the Pro-rich (Pr) ligand to the C-terminal SH3 domain. We present MD and NMR results on the dynamics and ligand interactions of a Pr-SH3 construct of DtxR. NMR relaxation data (T1, T2, and NOE) showed that the Pr ligand is very flexible, suggesting that it undergoes binding/unbinding transitions. A 50-ns MD trajectory of the protein was used to calculate T1, T2, and NOE, reproducing the NMR results for the SH3 domain but not for the Pr segment. During the MD simulation, the ligand stayed bound to the SH3 domain; thus the simulation represented the bound state. The NMR data for the Pr-segment could be explained by assuming that they represented the average behavior of a fast binding/unbinding exchange. Though unbinding was not observed in the MD simulation, the simulation did show large fluctuations of a loop which forms part of the wall of the binding pocket. The fluctuations led to opening up of the binding pocket, thus weakening the interaction with the Pr segment and perhaps ultimately leading to ligand unbinding.

Yi, Myunggi; Bhattacharya, Nilakshee; Zhou, Huan-Xiang

2005-11-01

397

Conformational properties and orientational order of a de Vries liquid crystal investigated through NMR spectroscopy.  

PubMed

Solid-state and liquid-state NMR spectroscopic techniques are used to describe at molecular level the behaviour of a de Vries liquid crystal (namely the mesogen 9HL) at the SmA-SmC* transition, which is characterized by the absence of the layer shrinkage, typical of non-de Vries smectogens. Previous (2)H NMR studies on the same smectogen, performed at a different magnetic field (from 4.70 to 18.80 T), provided evidence of the occurrence of a tilt of one of the three phenyl rings, constituting the aromatic core of 9HL, at the SmA-SmC* phase transition. In this work, the study is extended to the whole rigid aromatic core of the 9HL. In particular, the variable temperature behavior of the mesogen studied by 1D (13)C NMR cross-polarization (CP) and 2D (1)H-(13)C PDLF (proton-encoded (13)C-detected, local field) NMR experiments made possible the characterization of the conformational and orientational properties in the two smectic phases. These results are compared with various proposed models invoked to describe the SmA-SmC* transition in de Vries smectogens at a molecular level. PMID:24482195

Domenici, Valentina; Lelli, Moreno; Cifelli, Mario; Hamplova, Vera; Marchetti, Alessandro; Veracini, Carlo Alberto

2014-05-19

398

Noncovalent tagging proteins with paramagnetic lanthanide complexes for protein study.  

PubMed

The site-specific labeling of proteins with paramagnetic lanthanides offers unique opportunities for NMR spectroscopic analysis in structural biology. Herein, we report an interesting way of obtaining paramagnetic structural restraints by employing noncovalent interaction between a lanthanide metal complex, [Ln(L)3](n-) (L=derivative of dipicolinic acid, DPA), and a protein. These complexes formed by lanthanides and DPA derivatives, which have different substitution patterns on the DPA derivatives, produce diverse thermodynamic and paramagnetic properties when interacting with proteins. The binding affinity of [Ln(L)3](n-) with proteins, as well as the determined paramagnetic tensor, are tunable by changing the substituents on the ligands. These noncovalent interactions between [Ln(L)3](n-) and proteins offer great opportunities in the tagging of proteins with paramagnetic lanthanides. We expect that this method will be useful for obtaining multiple angles and distance restraints of proteins in structural biology. PMID:23450718

Wei, Zhen; Yang, Yin; Li, Qing-Feng; Huang, Feng; Zuo, Hui-Hui; Su, Xun-Cheng

2013-04-26

399

Comprehensive multiphase NMR spectroscopy: Basic experimental approaches to differentiate phases in heterogeneous samples  

NASA Astrophysics Data System (ADS)

Heterogeneous samples, such as soils, sediments, plants, tissues, foods and organisms, often contain liquid-, gel- and solid-like phases and it is the synergism between these phases that determine their environmental and biological properties. Studying each phase separately can perturb the sample, removing important structural information such as chemical interactions at the gel-solid interface, kinetics across boundaries and conformation in the natural state. In order to overcome these limitations a Comprehensive Multiphase-Nuclear Magnetic Resonance (CMP-NMR) probe has been developed, and is introduced here, that permits all bonds in all phases to be studied and differentiated in whole unaltered natural samples. The CMP-NMR probe is built with high power circuitry, Magic Angle Spinning (MAS), is fitted with a lock channel, pulse field gradients, and is fully susceptibility matched. Consequently, this novel NMR probe has to cover all HR-MAS aspects without compromising power handling to permit the full range of solution-, gel- and solid-state experiments available today. Using this technology, both structures and interactions can be studied independently in each phase as well as transfer/interactions between phases within a heterogeneous sample. This paper outlines some basic experimental approaches using a model heterogeneous multiphase sample containing liquid-, gel- and solid-like components in water, yielding separate 1H and 13C spectra for the different phases. In addition, 19F performance is also addressed. To illustrate the capability of 19F NMR soil samples, containing two different contaminants, are used, demonstrating a preliminary, but real-world application of this technology. This novel NMR approach possesses a great potential for the in situ study of natural samples in their native state.

Courtier-Murias, Denis; Farooq, Hashim; Masoom, Hussain; Botana, Adolfo; Soong, Ronald; Longstaffe, James G.; Simpson, Myrna J.; Maas, Werner E.; Fey, Michael; Andrew, Brian; Struppe, Jochem; Hutchins, Howard; Krishnamurthy, Sridevi; Kumar, Rajeev; Monette, Martine; Stronks, Henry J.; Hume, Alan; Simpson, André J.

2012-04-01

400

Simultaneous Application of ?-detected LMR and NMR Spectroscopy for Measurement of Nuclear Dipole and Quadrupole Moments  

NASA Astrophysics Data System (ADS)

We report the successful application of simultaneous ?-detected LMR (Level Mixing Resonance) and NMR (Nuclear Magnetic Resonance) techniques on ^12B implanted in a Mg single crystal. LMR experiments performed on ?-decaying nuclei allow determination of quadrupole frequency to magnetic moment ratio, and the addition of RF perturbation and subsequent determination of the NMR allows for extraction of each of the two individual moments. A major advantage of this technique is that projectile fragment alignment, which is readily produced in a projectile-fragmentation reaction, is transferred to nuclear polarization via the perturbing interaction in the non-cubic crystal. >From resonant change of the ?-decay asymmetry as a function of static magnetic field and applied RF we obtain information on nuclear structure and on initial alignment of the projectile fragments. This combined technique was then applied to neutron-rich ^18N spin-aligned projectile fragments, the results of which will be presented.

Rogers, W. F.; Neyens, G.; Coulier, N.; Teughels, S.; Vyvey, K.; Ternier, S.; Georgiev, G.; Coussement, R.; Lépine-Szily, A.

1997-10-01