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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.




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



Dynamic High-Resolution H-1 and P-31 NMR Spectroscopy and H-1 T-2 Measurements in Postmortem Rabbit Muscles Using Slow Magic Angle Spinning  

SciTech Connect

Postmortem changes in rabbit muscle tissue with different glycogen status (normal vs low) were followed continuously from 13 min postmortem until 8 h postmortem and again 20 h postmortem using simultaneous magic angle spinning 1H and 31P NMR spectroscopy together with measurement of the transverse relaxation time, T2, of the muscle water. The 1H metabolite spectra were measured using the phase-altered spinning sidebands (PASS) technique at a spinning rate of 40 Hz. pH values calculated from the 31P NMR spectra using the chemical shifts of the C-6 line of histidine in the 1H spectra and the chemical shifts of inorganic phosphate in the 31P spectra confirmed the different muscle glycogen status in the tissues. High-resolution 1H spectra obtained from the PASS technique revealed the presence of a new resonance line at 6.8 ppm during the postmortem period, which were absent in muscles with low muscle glycogen content. This new resonance line may originate from the aminoprotons in creatine, and its appearance may be a result of a pH effect on the exchange rate between the amino and the water protons and thereby the NMR visibility. Alternatively, the new resonance line may originate from the aromatic protons in tyrosine, and its appearance may be a result of a pH-induced protein unfolding exposing hydrophobic amino acid residues to the aqueous environment. Further studies are needed to evaluate these hypotheses. Finally, distributed analysis of the water T2 relaxation data revealed three relaxation populations and an increase in the population believed to reflect extramyofibrillar water through the postmortem period. This increase was significantly reduced (p < 0.0001) in samples from animals with low muscle glycogen content, indicating that the pH is controlling the extent of postmortem expulsion of water from myofibrillar structures. The significance of the postmortem increase in the amount extramyofibrillar water on the water-holding capacity was verified by centrifugation, which showed a reduced centrifugation loss in muscles with low preslaughter glycogen status (0.9 vs 1.9%, p 0.07).

Bertram, Hanne Christine; Hu, Jian Zhi; Rommereim, Donald N.; Wind, Robert A.; Andersen, Henrik J.



2 H Chemical-shift resolution and dipolar 2 H- 1 H, 2 H- 15 N correlations in solid-state MAS NMR spectroscopy for structure determination and distance measurements in hydrogen-bonded systems  

Microsoft Academic Search

In solid-state NMR, deuteron (2H) spectroscopy can be performed in full analogy to1H spectroscopy, including2H chemical-shift resolution and2H-X dipolar correlation schemes, when the NMR experiments are conducted in a “rotor-synchronized” fashion under fast magic-angle\\u000a spinning. Here, 2H-X NMR experiments of this type, including2H-15N and2H-1H chemical-shift correlations and distance measurements, are introduced and demonstrated on cytosine monohydrate, whose acidic\\u000a protons can

Martin Schulz-Dobrick; Ingo Schnell



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


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.



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.



"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.



Study of the conformational equilibria of some 2-(2?-hydroxyphenyl)-4-aryl-3 H -1,5-benzodiazepines using 1 H, 13 C, and 15 N NMR spectroscopy  

Microsoft Academic Search

Variable temperature1H NMR experiments of 2-(2'-hydroxyphenyl)-4-phenyl-3H-1,5-benzodiazepine (5a) and its derivatives5d and5e were carried out in order to investigate the conformational behaviour of these compounds. The ?G* values for the ring inversion barriers of5a and5d areca. 52 kJ\\/mol,i.e. they do not differ significantly as compared to analogous compounds without phenolic OH group(s). This indicates that the hydrogen bond has not to

R. Ahmad; M. Zia-ul-Haq; H. Duddeck; L. Stefaniak; J. Sitkowski




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...


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


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



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



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


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


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


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


Fast multidimensional NMR spectroscopy for sparse spectra.  


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



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.



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


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



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



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.


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.



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.



Metabolism of human gliomas: Assessment with H-1 MR spectroscopy and F-18 fluorodeoxyglucose PET  

SciTech Connect

Localized hydrogen-1 magnetic resonance (MR) spectroscopy and fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) were employed to obtain metabolic information from intracranial gliomas. Advantages and difficulties associated with comparison of results from the two modalities were realized. Forty patients were studied with H-1 MR spectroscopy. MR signal intensities from lactate, N-acetylaspartate (NAA), choline, and creatine from a volume of interest containing the tumor and a contralateral volume were obtained and evaluated. NAA signal intensities were generally decreased in the tumor spectra, and choline signal intensities were elevated. H-1 MR spectroscopy was unsuccessful in eight patients, and FDG PET scans were not obtained in four of the patients with successful MR spectroscopic examinations. Lactate signal intensity was detected in 10 of the 28 patients who had successful H-1 MR spectroscopic and FDG PET studies. Lactate signal intensities were observed in lesions shown at FDG PET to be hypermetabolic, as well as in lesions found to be hypometabolic.

Alger, J.R.; Frank, J.A.; Bizzi, A.; Fulham, M.J.; DeSouza, B.X.; Duhaney, M.O.; Inscoe, S.W.; Black, J.L.; van Zijl, P.C.; Moonen, C.T. (National Institute of Neurological Disorders and Stroke, National Institutes of Health (NIH), Bethesda, MD (USA))



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



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



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.



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



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.



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



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




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...


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


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



Metabolism of human gliomas: assessment with H-1 MR spectroscopy and F-18 fluorodeoxyglucose PET.  


Localized hydrogen-1 magnetic resonance (MR) spectroscopy and fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) were employed to obtain metabolic information from intracranial gliomas. Advantages and difficulties associated with comparison of results from the two modalities were realized. Forty patients were studied with H-1 MR spectroscopy. MR signal intensities from lactate, N-acetylaspartate (NAA), choline, and creatine from a volume of interest containing the tumor and a contralateral volume were obtained and evaluated. NAA signal intensities were generally decreased in the tumor spectra, and choline signal intensities were elevated. H-1 MR spectroscopy was unsuccessful in eight patients, and FDG PET scans were not obtained in four of the patients with successful MR spectroscopic examinations. Lactate signal intensity was detected in 10 of the 28 patients who had successful H-1 MR spectroscopic and FDG PET studies. Lactate signal intensities were observed in lesions shown at FDG PET to be hypermetabolic, as well as in lesions found to be hypometabolic. PMID:2243962

Alger, J R; Frank, J A; Bizzi, A; Fulham, M J; DeSouza, B X; Duhaney, M O; Inscoe, S W; Black, J L; van Zijl, P C; Moonen, C T



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



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



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


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))



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



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.



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



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



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


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


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.


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

SciTech Connect

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

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



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.


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


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



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


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


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


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


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



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


Multichannel visible spectroscopy diagnostic for particle transport studies in the H-1 heliac  

NASA Astrophysics Data System (ADS)

A multichannel spectroscopy diagnostic has been developed to study cross-field particle transport in the radiation-dominated low-temperature plasmas (Te<100 eV) in the H-1 heliac. The optical setup covers the full plasma minor radius in the poloidal plane collecting light from ten parallel chords arranged tangentially to the flux surfaces. The light collected from the plasma is coupled into optical fibers and through interference filters into photomultipliers. Two such ten-fiber arrays are aligned parallel to one another to allow the simultaneous monitoring of two different spectral lines. The net radial electron particle flux is determined from the continuity equation by integrating over the ionization source term in the steady-state partially ionized plasma. The diagnostic measures the neutral line intensities and their ratios (in case of helium using the line ratio technique) and also measures excited neutral and ion spectral lines (in case of the argon plasma transport studies). A comparative analysis of the radial particle transport in the low- and high-confinement regimes is presented.

Punzmann, H.; Shats, M. G.; Solomon, W. M.; Xia, H.



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.



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


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



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.



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.



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



Preparation, GIAO NMR calculations and acidic properties of some novel 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives with their antioxidant activities.  


Six novel 3-alkyl(aryl)-4-(p-nitrobenzoylamino)-4,5-dihydro-1H-1,2,4-triazol-5- ones (2a-f) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H- 1,2,4-triazol-5-ones (1a-f) with p-nitrobenzoyl chloride and characterized by elemental analyses and IR, (1)H-NMR, (13)C-NMR and UV spectral data. The newly synthesized compounds 2 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as acetone, isopropyl alcohol, tert-butyl alcohol and N,N-dimethylformamide, and the half-neutralization potential values and the corresponding pK(a) values were determined for all cases. Thus, the effects of solvents and molecular structure upon acidity were investigated. In addition, isotropic (1)H and (13)C nuclear magnetic shielding constants of compounds 2 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound has been optimized using the 6-311G basis set. Theoretical values were compared to the experimental data. Furthermore, these new compounds and five recently reported 3-alkyl-4-(2-furoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3a-c,e,f) were screened for their antioxidant activities. PMID:19325716

Yüksek, Haydar; Alkan, Muzaffer; Cakmak, Ismail; Ocak, Zafer; Bahçeci, Sule; Calapo?lu, Mustafa; Elmasta?, Mahfuz; Kolomuç, Ali; Aksu, Havva



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

SciTech Connect

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

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



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


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



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


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



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


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



Communication: Phase incremented echo train acquisition in NMR spectroscopy.  


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



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


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



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


Phosphorus speciation in a eutrophic lake by ³¹P NMR spectroscopy.  


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



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


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



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



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



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



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



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



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


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



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)



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.



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


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



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


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



Quantitative determination of cephalexin in cephradine by NMR spectroscopy.  


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



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



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



Solid-state NMR spectroscopy of Pb-rich apatite.  


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



NMR spectroscopy and perfusion of mammalian cells using surface microprobes.  


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



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.


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.



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



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



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



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



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


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



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



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


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



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


(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



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



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.



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


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



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.



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


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



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


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


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




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...


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



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



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


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.



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.



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.



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

NASA Astrophysics Data System (ADS)

We propose a solid-state NMR method that maximizes the advantages of high-resolution magic-angle-spinning (HRMAS) applied to intact biopsies when compared to more conventional liquid-state NMR approaches. Theoretical treatment, numerical simulations and experimental results on intact human brain biopsies are presented. Experimentally, it is proven that an optimized adiabatic TOBSY (TOtal through Bond correlation SpectroscopY) solid-state NMR pulse sequence for two-dimensional 1H- 1H homonuclear scalar-coupling longitudinal isotropic mixing provides a 20%-50% improvement in signal-to-noise ratio relative to its liquid-state analogue TOCSY (TOtal Correlation SpectroscopY). For this purpose we have refined the C9151 symmetry-based 13C TOBSY pulse sequence for 1H MRS use and compared it to MLEV-16 TOCSY sequence. Both sequences were rotor-synchronized and implemented using WURST-8 adiabatic inversion pulses. As discussed theoretically and shown in simulations, the improved magnetization-transfer comes from actively removing residual dipolar couplings from the average Hamiltonian. Importantly, the solid-state NMR techniques are tailored to perform measurements at low temperatures where sample degradation is reduced. This is the first demonstration of such a concept for HRMAS metabolic profiling of disease processes, including cancer, from biopsies requiring reduced sample degradation for further genomic analysis.

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



Heteronuclear NMR spectroscopy as a surface-selective technique: a unique look at the hydroxyl groups of ?-alumina.  


The surface hydroxyl groups of ?-alumina dehydroxylated at 500?°C were studied by a combination of one- and two-dimensional homo- and heteronuclear (1)H and (27)Al NMR spectroscopy at high magnetic field. In particular, by harnessing (1)H-(27) Al dipolar interactions, a high selectivity was achieved in unveiling the topology of the alumina surface. The terminal versus bridging character of the hydroxyl groups observed in the (1)H magic-angle spinning (MAS) NMR spectrum was demonstrated thanks to (1)H-(27) Al RESPDOR (resonance-echo saturation-pulse double-resonance). In a further step the hydroxyl groups were assigned to their aluminium neighbours thanks to a {(1)H}-(27) Al dipolar heteronuclear multiple quantum correlation (D-HMQC), which was used to establish a first coordination map. Then, in combination with (1)H-(1) H double quantum (DQ) MAS, these elements helped to reveal intimate structural features of the surface hydroxyls. Finally, the nature of a peculiar reactive hydroxyl group was demonstrated following this methodology in the case of CO2 reactivity with alumina. PMID:24604836

Taoufik, Mostafa; Szeto, Kai C; Merle, Nicolas; Del Rosal, Iker; Maron, Laurent; Trébosc, Julien; Tricot, Grégory; Gauvin, Régis M; Delevoye, Laurent



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



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


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



Water behavior in bacterial spores by deuterium NMR spectroscopy.  


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



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.



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



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



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



A system for NMR stark spectroscopy of quadrupolar nuclei.  


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



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


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



Insights into atomic-level interaction between mefenamic acid and eudragit EPO in a supersaturated solution by high-resolution magic-angle spinning NMR spectroscopy.  


The intermolecular interaction between mefenamic acid (MFA), a poorly water-soluble nonsteroidal anti-inflammatory drug, and Eudragit EPO (EPO), a water-soluble polymer, is investigated in their supersaturated solution using high-resolution magic-angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy. The stable supersaturated solution with a high MFA concentration of 3.0 mg/mL is prepared by dispersing the amorphous solid dispersion into a d-acetate buffer at pH 5.5 and 37 °C. By virtue of MAS at 2.7 kHz, the extremely broad and unresolved (1)H resonances of MFA in one-dimensional (1)H NMR spectrum of the supersaturated solution are well-resolved, thus enabling the complete assignment of MFA (1)H resonances in the aqueous solution. Two-dimensional (2D) (1)H/(1)H nuclear Overhauser effect spectroscopy (NOESY) and radio frequency-driven recoupling (RFDR) under MAS conditions reveal the interaction of MFA with EPO in the supersaturated solution at an atomic level. The strong cross-correlations observed in the 2D (1)H/(1)H NMR spectra indicate a hydrophobic interaction between the aromatic group of MFA and the backbone of EPO. Furthermore, the aminoalkyl group in the side chain of EPO forms a hydrophilic interaction, which can be either electrostatic or hydrogen bonding, with the carboxyl group of MFA. We believe these hydrophobic and hydrophilic interactions between MFA and EPO molecules play a key role in the formation of this extremely stable supersaturated solution. In addition, 2D (1)H/(1)H RFDR demonstrates that the molecular MFA-EPO interaction is quite flexible and dynamic. PMID:24283196

Higashi, Kenjirou; Yamamoto, Kazutoshi; Pandey, Manoj Kumar; Mroue, Kamal H; Moribe, Kunikazu; Yamamoto, Keiji; Ramamoorthy, Ayyalusamy



A mobile NMR system with full spectroscopy capability.  


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



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


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



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))



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


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



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.



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


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



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



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



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.



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


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



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




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.



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



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



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



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



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



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



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.



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



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



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


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



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



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


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



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.



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


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



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



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



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


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



?High resolution-magic-angle spinning NMR spectroscopy for metabolic phenotyping of Caenorhabditis elegans.  


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



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


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



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.



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.


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.



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



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)



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.



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


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



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



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.



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


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



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


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



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


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



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



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.



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



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 +\\/ 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.



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.



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



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


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



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




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.



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


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



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.



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



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



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



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


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



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.



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.



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


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



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



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



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:



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


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



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


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



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


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



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

Microsoft Academic Search

Surface enhanced Raman scattering (SERS) spectra of 1H-1,2,4-triazole-3-thione (TAS) adsorbed on silver sols were recorded. From the comparison between the SERS and normal Raman spectra of TAS in aqueous and in NaOH solutions, it can be deduced that the substance adsorbs in the ionized thiolic form (TASA) on the silver surface. From the description of the vibrational normal modes related

Barbara Pergolese; Adriano Bigotto



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



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


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



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.



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.



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


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



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


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



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


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


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



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


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



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.



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


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



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


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



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

NASA Astrophysics Data System (ADS)

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

Pergolese, Barbara; Bigotto, Adriano



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



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


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



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


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



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


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



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


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



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))



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.



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


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



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.



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.



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


(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



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


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



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


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



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



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:; 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)



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


(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



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.



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.



Kinetic and J-resolved statistical total correlation NMR spectroscopy approaches to structural information recovery in complex reacting mixtures: application to acyl glucuronide intramolecular transacylation reactions.  


We demonstrate here a new variant on a statistical spectroscopic method for recovering structural information on unstable intermediates formed in reaction mixtures. We exemplify this approach with respect to the internal acyl migration reactions of 1-beta-O-acyl glucuronides (AGs), which rearrange at neutral or slightly alkaline pH on a minute to hour time scale to yield a series of positional glucuronide ring isomers and alpha/beta anomers from the 1-beta (starting material), i.e. 2-beta, 2-alpha, 1-alpha, 3-beta, 3-alpha, and 4-beta, 4-alpha isomers together with the aglycon and alpha- and beta-glucuronic acid hydrolysis products. Multiple sequential 800 MHz cryoprobe (1)H NMR spectra (1D and 2D J-resolved, JRES) were collected on a 5.1 mM solution of a synthetic model drug glucuronide, 1-beta-O-acyl (S)-alpha-methyl phenylacetyl glucuronide (MPG) in 0.1 M sodium phosphate buffer in D2O at pD 7.4 over 18 h to monitor the reaction which leads to the formation of the eight positional isomers and hydrolysis products. As the reaction proceeds and new isomers form, the NMR signal intensities vary accordingly allowing the application of a novel kinetic variant on statistical total correlation spectroscopy (K-STOCSY) method to recover the connectivities between proton signals on the same reacting molecule based on their intensity covariance through time. We performed K-STOCSY analysis on both the standard 1D NMR spectra and the skyline projected singlets of the (1)H-(1)H JRES NMR spectra through time, i.e. the K-JRES-STOCSY experimental variant, which increases the effective spectral dispersion and is ideally suited for the analysis of heavily overlapped spin systems. High statistical correlations were observed between mutarotated alpha- and beta-anomers of individual positional isomers, as well as directly acyl migrated products and anticorrelation observed between signals from compounds that were being depleted as others increased, e.g. between the 1-beta and 2-alpha/2-beta isomers. This statistical kinetic approach enabled the recovery of structural connectivity information on all isomers allowing unequivocal resonance assignment, and this approach to spectroscopic information recovery has wider potential uses in the study of reactions that occur on the second-to-minute time scale in conditions where multiple sequential NMR spectra can be collected. JRES-STOCSY is also of potential use as a method for recovering spectroscopic information in highly overlapped NMR signals and spin systems in other types of complex mixture analysis. PMID:18470997

Johnson, Caroline H; Athersuch, Toby J; Wilson, Ian D; Iddon, Lisa; Meng, Xiaoli; Stachulski, Andrew V; Lindon, John C; Nicholson, Jeremy K



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.



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


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


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

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



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


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



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


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



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.



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



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


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



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.



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.



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



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



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


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



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


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



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.



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


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



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.




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.



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


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



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


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


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


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


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.



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


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



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


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



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


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



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


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



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.



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



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.



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



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



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



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


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



Molecular Dynamics and NMR Spectroscopy Studies of E. coli Lipopolysaccharide Structure and Dynamics  

PubMed Central

Lipopolysaccharide (LPS), a component of Gram-negative bacterial outer membranes, comprises three regions: lipid A, core oligosaccharide, and O-antigen polysaccharide. Using the CHARMM36 lipid and carbohydrate force fields, we have constructed a model of an Escherichia coli R1 (core) O6 (antigen) LPS molecule. Several all-atom bilayers are built and simulated with lipid A only (LIPA) and varying lengths of 0 (LPS0), 5 (LPS5), and 10 (LPS10) O6 antigen repeating units; a single unit of O6 antigen contains five sugar residues. From 1H,1H-NOESY experiments, cross-relaxation rates are obtained from an O-antigen polysaccharide sample. Although some experimental deviations are due to spin-diffusion, the remaining effective proton-proton distances show generally very good agreement between NMR experiments and molecular dynamics simulations. The simulation results show that increasing the LPS molecular length has an impact on LPS structure and dynamics and also on LPS bilayer properties. Terminal residues in a LPS bilayer are more flexible and extended along the membrane normal. As the core and O-antigen are added, per-lipid area increases and lipid bilayer order decreases. In addition, results from mixed LPS0/5 and LPS0/10 bilayer simulations show that the LPS O-antigen conformations at a higher concentration of LPS5 and LPS10 are more orthogonal to the membrane and less flexible. The O-antigen concentration of mixed LPS bilayers does not have a significant effect on per-lipid area and hydrophobic thickness. Analysis of ion and water penetration shows that water molecules can penetrate inside the inner core region, and hydration is critical to maintain the integrity of the bilayer structure. PMID:24047996

Wu, Emilia L.; Engstrom, Olof; Jo, Sunhwan; Stuhlsatz, Danielle; Yeom, Min Sun; Klauda, Jeffery B.; Widmalm, Goran; Im, Wonpil



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



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.



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.


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


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



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.



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


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



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


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



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.



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


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



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



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



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


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



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



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



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



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.



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



Adducts of nitrogenous ligands with rhodium(II) tetracarboxylates and tetraformamidinate: NMR spectroscopy and density functional theory calculations.  


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



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


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



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



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



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


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



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.



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



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.



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


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



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



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.



Probing transient conformational states of proteins by solid-state R(1?) relaxation-dispersion NMR spectroscopy.  


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



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.



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


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



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.



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



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



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



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


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



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


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



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



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.



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



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



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


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



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


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



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.



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.  


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



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


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



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


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



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



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


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



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))



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


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



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.



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


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



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



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



Supramolecular assembly of dendritic polymers elucidated by 1H and 13C solid-state MAS NMR spectroscopy.  


Advanced solid-state NMR methods under fast magic-angle spinning (MAS) are used to study the structure and dynamics of large supramolecular systems, which consist of a polymer backbone with dendritic side groups and self-assemble into a columnar structure. The NMR experiments are performed on as-synthesized samples, i.e., no isotopic enrichment is required. The analysis of (1)H NMR chemical-shift effects as well as dipolar (1)H-(1)H or (1)H-(13)C couplings provide site-specific insight into the local structure and the segmental dynamics, in particular, of phenyl rings and -CH(2)O- linking units within the dendrons. Relative changes of (1)H chemical shifts (of up to -3 ppm) serve as distance constraints and allow protons to be positioned relative to aromatic rings. Together with dipolar spinning sideband patterns, pi-pi packing phenomena and local order parameters (showing variations between 30% and 100%) are selectively and precisely determined, enabling the identification of the dendron cores as the structure-directing moieties within the supramolecular architecture. The study is carried out over a representative selection of systems which reflect characteristic differences, such as different polymer backbones, sizes of dendritic side groups, or length and flexibility of linking units. While the polymer backbone is found to have virtually no effect on the overall structure and properties, the systems are sensitively affected by changing the generation or the linkage of the dendrons. The results help to understand the self-assembly process of dendritic moieties and aid the chemical design of self-organizing molecular structures. PMID:14570506

Rapp, Almut; Schnell, Ingo; Sebastiani, Daniel; Brown, Steven P; Percec, Virgil; Spiess, Hans Wolfgang



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


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



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



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



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


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



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



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



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



750 MHz 1H NMR spectroscopy characterisation of the complex metabolic pattern of urine from patients with inborn errors of metabolism: 2-hydroxyglutaric aciduria and maple syrup urine disease  

Microsoft Academic Search

750 MHz 1H NMR spectroscopy has been used to characterise in detail the abnormal low molecular weight metabolites of urine from two patients with inborn errors of metabolism. One case of the rare condition 2-hydroxyglutaric aciduria has been examined. There is at present no rapid routine method to detect this genetic defect, although NMR spectroscopy of urine is shown to

Elaine Holmes; Peta J. D Foxall; Manfred Spraul; R Duncan Farrant; Jeremy K Nicholson; John C Lindon



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.



Quantitative Determination of Chemical Processes by Dynamic Nuclear Polarization Enhanced Nuclear Magnetic Resonance Spectroscopy  

E-print Network

Transfer for Pharmacophore Mapping MRI Magnetic Resonance Imaging MRS Magnetic Resonance Spectroscopy MW Microwave viii NMR Nuclear Magnetic Resonance NOE Nuclear Overhauser Effect pCBA p-chlorobenzaldehyde ppm Parts per million PTD 4... (II-10)) using one assumed value for T1. ............ 38 III-1 Reaction of DPBD with PTD in acetonitrile. The signal intensities of H1 and H1? were monitored in the NMR experiments. .......................... 48 III-2 Stacked plots...

Zeng, Haifeng



Studies on the acute biochemical effects of La(NO3)3 using 1H NMR spectroscopy of urine combined with pattern recognition.  


(1)H NMR spectroscopic and pattern recognition-based methods were applied to the studies on the acute biochemical effects of La(NO(3))(3). Male Wistar rats were separated into groups (n=10) and each was treated with one of following compounds, sodium chromate (NaCrO(4)), mercury II chloride (HgCl(2)), 2-bromoethanamine hydrobromide (BEA), carbon tetrachloride (CCl(4)), hydrazine (HYD), alpha-naphthylisothiocyanate (ANIT), and three doses of La(NO(3))(3). Urine samples were collected over a 48-h time course and measured by 600 MHz NMR spectroscopy. Each spectrum was data-processed to provide 205 intensity-related descriptors used as input coordinates in a multidimensional space and analyzed by pattern recognition method. By NMR and principal components analysis (PCA) methods, the biochemical effects classification and time-course trajectories of various doses of La(NO(3))(3) were achieved. The toxicity of La(NO(3))(3) was similar to that of carbon tetrachloride according to the (1)H NMR spectral profiles and toxicity classification. This work illustrates the high reliability of NMR-PR method using (1)H NMR spectroscopy for the exploration and prediction of biochemical effects of rare earths in rats. PMID:15621299

Wu, Huifeng; Zhang, Xiaoyu; Li, Xiaojing; Li, Zhongfeng; Wu, Yijie; Pei, Fengkui



Determination of Structural Topology of a Membrane Protein in Lipid -Bilayers using Polarization Optimized Experiments (POE) for Static and MAS Solid State NMR Spectroscopy  

PubMed Central

The low sensitivity inherent to both the static and magic angle spinning techniques of solid-state NMR (ssNMR) spectroscopy has thus far limited the routine application of multidimensional experiments to determine the structure of membrane proteins in lipid bilayers. Here, we demonstrate the advantage of using a recently developed class of experiments, polarization optimized experiments (POE), for both static and MAS spectroscopy to achieve higher sensitivity and substantial time-savings for 2D and 3D experiments. We used sarcolipin, a single pass membrane protein, reconstituted in oriented bicelles (for oriented ssNMR) and multilamellar vesicles (for MAS ssNMR) as a benchmark. The restraints derived by these experiments are then combined into a hybrid energy function to allow simultaneous determination of structure and topology. The resulting structural ensemble converged to a helical conformation with a backbone RMSD ? 0.44 Å, a tilt angle of 24° ± 1°, and an azimuthal angle of 55° ± 6°. This work represents a crucial first step toward obtaining high-resolution structures of large membrane proteins using combined multidimensional O-ssNMR and MAS-ssNMR. PMID:23963722

Mote, Kaustubh R.; Gopinath, T.; Veglia, Gianluigi



Determination of structural topology of a membrane protein in lipid bilayers using polarization optimized experiments (POE) for static and MAS solid state NMR spectroscopy.  


The low sensitivity inherent to both the static and magic angle spinning techniques of solid-state NMR (ssNMR) spectroscopy has thus far limited the routine application of multidimensional experiments to determine the structure of membrane proteins in lipid bilayers. Here, we demonstrate the advantage of using a recently developed class of experiments, polarization optimized experiments, for both static and MAS spectroscopy to achieve higher sensitivity and substantial time-savings for 2D and 3D experiments. We used sarcolipin, a single pass membrane protein, reconstituted in oriented bicelles (for oriented ssNMR) and multilamellar vesicles (for MAS ssNMR) as a benchmark. The restraints derived by these experiments are then combined into a hybrid energy function to allow simultaneous determination of structure and topology. The resulting structural ensemble converged to a helical conformation with a backbone RMSD ~0.44 Å, a tilt angle of 24° ± 1°, and an azimuthal angle of 55° ± 6°. This work represents a crucial first step toward obtaining high-resolution structures of large membrane proteins using combined multidimensional oriented solid-state NMR and magic angle spinning solid-state NMR. PMID:23963722

Mote, Kaustubh R; Gopinath, T; Veglia, Gianluigi



Characterization of the disordered phosphate network in CaO–P 2O 5 glasses by 31P solid-state NMR and Raman spectroscopies  

Microsoft Academic Search

In this study, the disordered network of calcium phosphate glasses is investigated by Raman scattering and 31P magic angle spinning (MAS) solid-state NMR spectroscopies. The use of both spectroscopies in a combined approach allows drawing a detailed understanding of the structure of these glasses. The P?O?P connectivity between successive PO4 tetrahedra is probed using through-bond double quantum–single quantum (DQ–SQ) and

Claire Roiland; Franck Fayon; Patrick Simon; Dominique Massiot



Symbiosis between in vivo and in vitro NMR spectroscopy: The creatine, N-acetylaspartate, glutamate, and GABA content of the epileptic human brain  

Microsoft Academic Search

High resolution 1H NMR spectroscopy was used to analyze temporal lobe biopsies obtained from patients with epilepsy. Heat-stabilized cerebrum, dialyzed cytosolic macromolecules, and perchloric acid extracts were studied using one- and two dimensional spectroscopy. Anterior temporal lobe neocortex was enriched in GABA, glutamate, alanine, N-acetylaspartate, and creatine. Subjacent white matter was enriched in aspartate, glutamine, and inositol. The N-acetylaspartate\\/creatine mole

Ognen A. C. Petroff; Lisa A. Pleban; Dennis D. Spencer



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.



Structure determination of the seven-helical transmembrane receptor sensory rhodopsin II by solution NMR spectroscopy  

PubMed Central

Seven-helical membrane proteins represent a challenge for structural biology. Here, we report the first NMR structure determination of a detergent-solubilized seven-helical transmembrane (7TM) protein, the phototaxis receptor sensory rhodopsin II (pSRII) from Natronomonas pharaonis, as a proof of principle. The overall quality of the structure ensemble is extremely good (backbone root mean squared deviation of 0.48 Å) and agrees well with previously determined X-ray structures. Furthermore, measurements in more native-like small phospholipid bicelles indicate that the protein structure is the same as in detergent micelles, suggesting that environment specific effects are minimal when using mild detergents. We use our case study as a platform to discuss the feasibility of similar solution NMR studies for other 7TM proteins including members of the family of G protein-coupled receptors (GPCRs). PMID:20512150

Gautier, Antoine; Mott, Helen R.; Bostock, Mark J.; Kirkpatrick, John P.; Nietlispach, Daniel



SIMPSON: A General Simulation Program for Solid-State NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

A computer program for fast and accurate numerical simulation of solid-state NMR experiments is described. The program is designed to emulate a NMR spectrometer by letting the user specify high-level NMR concepts such as spin systems, nuclear spin interactions, RF irradiation, free precession, phase cycling, coherence-order filtering, and implicit/explicit acquisition. These elements are implemented using the Tcl scripting language to ensure a minimum of programming overhead and direct interpretation without the need for compilation, while maintaining the flexibility of a full-featured programming language. Basicly, there are no intrinsic limitations to the number of spins, types of interactions, sample conditions (static or spinning, powders, uniaxially oriented molecules, single crystals, or solutions), and the complexity or number of spectral dimensions for the pulse sequence. The applicability ranges from simple 1D experiments to advanced multiple-pulse and multiple-dimensional experiments, series of simulations, parameter scans, complex data manipulation/visualization, and iterative fitting of simulated to experimental spectra. A major effort has been devoted to optimizing the computation speed using state-of-the-art algorithms for the time-consuming parts of the calculations implemented in the core of the program using the C programming language. Modification and maintenance of the program are facilitated by releasing the program as open source software (General Public License) currently at The general features of the program are demonstrated by numerical simulations of various aspects for REDOR, rotational resonance, DRAMA, DRAWS, HORROR, C7, TEDOR, POST-C7, CW decoupling, TPPM, F-SLG, SLF, SEMA-CP, PISEMA, RFDR, QCPMG-MAS, and MQ-MAS experiments.

Bak, Mads; Rasmussen, Jimmy T.; Nielsen, Niels Chr.



Analysis of lipoproteins using 2D diffusion-edited NMR spectroscopy and multi-way chemometrics  

Microsoft Academic Search

This study represents the first application of multi-way calibration by N-PLS and multi-way curve resolution by PARAFAC to 2D diffusion-edited 1H NMR spectra. The aim of the analysis was to evaluate the potential for quantification of lipoprotein main- and subfractions in human plasma samples. Multi-way N-PLS calibrations relating the methyl and methylene peaks of lipoprotein lipids to concentrations of the

Marianne Dyrby; Martin Petersen; Andrew K. Whittaker; Lynette Lambert; Lars Nørgaard; Rasmus Bro; Søren Balling Engelsen



Investigation of Polymorphism in Aspartame and Neotame Using Solid-State NMR Spectroscopy  

Microsoft Academic Search

We have been studying the artificial sweeteners aspartame (l-aspartyl-l-phenylalanine methyl ester) and neotame (N-(3,3-dimethylbutyl)-l-aspartyl-l-phenylalanine methyl ester) as compounds which exhibit polymorphism. 13C CP\\/MAS NMR shows that aspartame exists in three distinct forms at room temperature, depending on preparation conditions. For two of the forms, there exists three resonances for each carbon, indicating three crystallographically inequivalent sites and therefore three distinct

Mark T Zell; Brian E Padden; David J. W Grant; Stephen A Schroeder; Kurt L Wachholder; Indra Prakash; Eric J Munson



In Vivo 31P-NMR Diffusion Spectroscopy of ATP and Phosphocreatine in Rat Skeletal Muscle  

Microsoft Academic Search

The aim of this study was to measure the diffusion of ATP and phosphocreatine (PCr) in intact rat skeletal muscle, using 31P-NMR. The acquisition of the diffusion-sensitized spectra was optimized in terms of the signal-to-noise ratio for ATP by using a frequency-selective stimulated echo sequence in combination with adiabatic radio-frequency pulses and surface coil signal excitation and reception. Diffusion restriction

Robin A. de Graaf; Arnaud van Kranenburg; Klaas Nicolay



Practical considerations over spectral quality in solid state NMR spectroscopy of soluble proteins.  


Great theoretical and methodological advances are pushing the limits of resolution and sensitivity in solid state NMR (SSNMR). However, sample preparation remains a critical issue for the success of an experiment. The factors affecting spectral quality in SSNMR samples are discussed, examining cases encountered in the literature and presenting new experimental data. A discussion on resolution and sensitivity in sedimented solutes is framed in this context. PMID:23990200

Fragai, Marco; Luchinat, Claudio; Parigi, Giacomo; Ravera, Enrico



Determination of additives in an electrolytic zinc bath by q 1 H-NMR spectroscopy  

Microsoft Academic Search

The use of proton nuclear magnetic resonance (1H-NMR) for the quantification of additives in an electrolytic Zn bath is reported. A simple and quick method is described\\u000a that does not need any prior sample preparation. Contrary to other analytical methods, the three additives in the bath, benzylidene\\u000a acetone (BDA), benzoic acid (BA) and poly(ethylene glycol) (PE400), can be quantified. Two

Ainara Barriola; José I. Miranda; Miren Ostra; Carlos Ubide



Following macromolecular interactions and sugar metabolism using site specific /sup 3/H labelling and NMR spectroscopy  

SciTech Connect

In this paper we discuss the application of /sup 3/H NMR to biological problems. Two specific examples will be described; first, analysis of the binding of maltose to its transport protein from E. coli, called MBP; and second, following the glycolytic metabolism of glucose in erythrocytes. In both of these cases the unique properties of /sup 3/H for magnetic resonance make possible observations which are difficult with other methods. 4 refs., 2 figs.

Williams, P.; Morimoto, Hiromi; Gehring, K.B.; Nikaido, Hiroshi; Carson, P.; Un, Sun; Klein, M.; Wemmer, D.E.



Feasibility of arsenic and antimony NMR spectroscopy in solids: an investigation of some group 15 compounds.  


The feasibility of obtaining (75)As and (1)(21/123)Sb NMR spectra for solids at high and moderate magnetic field strengths is explored. Arsenic-75 nuclear quadrupolar coupling constants and chemical shifts have been measured for arsenobetaine bromide and tetraphenylarsonium bromide. Similarly, (121/123)Sb NMR parameters have been measured for tetraphenylstibonium bromide and potassium hexahydroxoantimonate. The predicted pseudo-tetrahedral symmetry at arsenic and the known trigonal bipyramidal symmetry at antimony in their respective tetraphenyl-bromide "salts" are reflected in the measured (75)As and (121)Sb nuclear quadrupole coupling constants, CQ((75)As)=7.8MHz and CQ((121)Sb)=159MHz, respectively. Results of density functional theory quantum chemistry calculations for isolated molecules using ADF and first-principles calculations using CASTEP, a gauge-including projector augmented wave method to deal with the periodic nature of solids, are compared with experiment. Although the experiments can be time consuming, measurements of (75)As and (121)Sb NMR spectra (at 154 and 215MHz, respectively, i.e., at B0=21.14T) with linewidths in excess of 1MHz are feasible using uniform broadband excitation shaped pulse techniques (e.g., WURST and WURST-QCPMG). PMID:24973027

Faucher, Alexandra; Terskikh, Victor V; Wasylishen, Roderick E



3D Localized 2D NMR Spectroscopy on an MRI Scanner  

NASA Astrophysics Data System (ADS)

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, 2D zero-quantum, 2D double-quantum, zero-quantum-filtered COSY and SECSY, and double-quantum-filtered COSY and SECSY. Two-dimensional plots for the J-resolved and multiple-quantum sequences are presented for a phantom containing an aqueous solution of 10 m M alanine. Sensitivity of different multiple-quantum-coherence orders to B0 inhomogeneity is discussed. Localized double-quantum-filtered COSY of a phantom containing physiological concentrations of several metabolites also is presented to demonstrate the feasibility of performing this technique within time limits reasonable for human comfort. The first-reported 2D J-resolved 1H in vivo MR spectrum localized in three dimensions in presented here, acquired predominantly from the cerebral white matter of a healthy volunteer and demonstrating the use of localized 2D NMR techniques in vivo.

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


Mg/Al Ordering in Layered Double Hydroxides Revealed by Multinuclear NMR Spectroscopy  

SciTech Connect

The anion-exchange ability of layered double hydroxides (LDHs) has been exploited to create materials for use in catalysis, drug delivery, and environmental remediation. The specific cation arrangements in the hydroxide layers of hydrotalcite-like LDHs, of general formula Mg2+1–xAl3+xOH2(Anionn– x/n)·yH2O, have, however, remained elusive, and their elucidation could enhance the functional optimization of these materials. We applied rapid (60 kilohertz) magic angle spinning (MAS) to obtain high-resolution hydrogen-1 nuclear magnetic resonance (1H NMR) spectra and characterize the magnesium and aluminum distribution. These data, in combination with 1H-27Al double-resonance and 25Mg triple-quantum MAS NMR data, show that the cations are fully ordered for magnesium:aluminum ratios of 2:1 and that at lower aluminum content, a nonrandom distribution of cations persists, with no Al3+-Al3+ close contacts. The application of rapid MAS NMR methods to investigate proton distributions in a wide range of materials is readily envisaged.

Sideris, Paul J.; Nielsen, Ulla G.; Gan, Zhehong; Grey, Clare P.



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

PubMed Central

We use optical Faraday rotation (OFR) to probe nuclear spins in real time at high-magnetic field in a range of diamagnetic sample fluids. Comparison of OFR-detected NMR spectra reveals a correlation between the relative signal amplitude and the fluid Verdet constant, which we interpret as a manifestation of the variable detuning between the probe beam and the sample optical transitions. The analysis of chemical-shift-resolved, optically detected spectra allows us to set constraints on the relative amplitudes of hyperfine coupling constants, both for protons at chemically distinct sites and other lower-gyromagnetic-ratio nuclei including carbon, fluorine, and phosphorous. By considering a model binary mixture we observe a complex dependence of the optical response on the relative concentration, suggesting that the present approach is sensitive to the solvent-solute dynamics in ways complementary to those known in inductive NMR. Extension of these experiments may find application in solvent suppression protocols, sensitivity-enhanced NMR of metalloproteins in solution, the investigation of solvent-solute interactions, or the characterization of molecular orbitals in diamagnetic systems. PMID:22100736

Pagliero, Daniela; Meriles, Carlos A.



Metabolomic Investigations of American Oysters Using 1H-NMR Spectroscopy  

PubMed Central

The Eastern oyster (Crassostrea virginica) is a useful, robust model marine organism for tissue metabolism studies. Its relatively few organs are easily delineated and there is sufficient understanding of their functions based on classical assays to support interpretation of advanced spectroscopic approaches. Here we apply high-resolution proton nuclear magnetic resonance (1H NMR)-based metabolomic analysis to C. virginica to investigate the differences in the metabolic profile of different organ groups, and magnetic resonance imaging (MRI) to non-invasively identify the well separated organs. Metabolites were identified in perchloric acid extracts of three portions of the oyster containing: (1) adductor muscle, (2) stomach and digestive gland, and (3) mantle and gills. Osmolytes dominated the metabolome in all three organ blocks with decreasing concentration as follows: betaine > taurine > proline > glycine > ß-alanine > hypotaurine. Mitochondrial metabolism appeared most pronounced in the adductor muscle with elevated levels of carnitine facilitating ß-oxidation, and ATP, and phosphoarginine synthesis, while glycogen was elevated in the mantle/gills and stomach/digestive gland. A biochemical schematic is presented that relates metabolites to biochemical pathways correlated with physiological organ functions. This study identifies metabolites and corresponding 1H NMR peak assignments for future NMR-based metabolomic studies in oysters. PMID:21116407

Tikunov, Andrey P.; Johnson, Christopher B.; Lee, Haakil; Stoskopf, Michael K.; Macdonald, Jeffrey M.



Conformational Analysis of Oxidized Peptide Fragments of the C-terminal Redox Center in Thioredoxin Reductases by NMR Spectroscopy†  

PubMed Central

Vicinal disulfide rings (VDRs) occur when a disulfide bond forms between adjacent cysteine residues in a protein and results in a rare eight-membered ring structure. This eight-membered ring has been found to exist in four major conformations in solution, divided between cis and trans conformers. Some selenoenzymes use a special type of VDR in which selenium replaces sulfur, generating a vicinal selenosulfide ring (VSeSR). Here we provide evidence that this substitution reduces ring strain, resulting in a strong preference for the trans conformation relative to cis in a VSeSR (cis:trans – 9:91). This was determined by using the “?-gauche effect” which makes use of both 1H-NMR and two-dimensional (2D) NMR techniques for determining the amide bond conformeric ratio. The presence of selenium in a VSeSR also lowers the dihedral strain energy (DSE) of the selenosulfide bond relative to the disulfide bond of VDRs. While cis amide geometry decreases strain on the amide bond, it increases strain on the scissile disulfide bond of the VDR found in thioredoxin reductase from D. melanogaster (DmTR). We hypothesize that the cis conformation of the VDR is the catalytically competent conformer for thiol/disulfide exchange. This hypothesis was investigated by computing the DSE of VDR and VSeSR conformers, the structure of which was determined by 2D NMR spectroscopy and energy minimization. The computed values of the VDR from DmTR are 16.5 kJ/mol DSE and 14.3 kJ/mol for the C+ and T? conformers, respectively, supporting the hypothesis that the enzyme uses the C+ conformer for thiol/disulfide exchange. PMID:24599608

Ruggles, Erik L.; Deker, P. Bruce; Hondal, Robert J.



TSNo s02-hunger124547-O On the Use of 31-P NMR Spectroscopy to Determine Chemical Forms of Phosphorus in Soils.  

E-print Network

TSNo s02-hunger124547-O Title On the Use of 31-P NMR Spectroscopy to Determine Chemical Forms by surface reactions with iron and aluminum (hydr)oxides. Despite extensive past research, basic reactions to the common aluminum mineral gibbsite are investigated. The structure and bonding environment of phosphate

Sparks, Donald L.


Alkylation of benzene with carbon monoxide over Zn/H-ZSM-5 zeolite studied using in situ solid-state NMR spectroscopy.  


Using in situ solid-state NMR spectroscopy we show that CO can act as an alkylating reagent and react with benzene to produce toluene over a Zn/H-ZSM-5 zeolite. In the alkylation reaction, CO provides the methyl group of toluene via a methoxy intermediate. PMID:25126651

Wang, Xiumei; Xu, Jun; Qi, Guodong; Wang, Chao; Wang, Qiang; Deng, Feng



Use of ionic liquids in the study of fruit ripening by high-resolution 13C NMR spectroscopy: 'green' solvents meet green bananas.  


Banana pulps at any ripening stage can be completely dissolved in solvent systems based on the ionic liquid (IL) 1-n-butyl-3-methylimidazolium chloride ([C4mim]Cl), and variations in the carbohydrate composition of the fruit analyzed directly on the resulting solutions using high-resolution 13C NMR spectroscopy. PMID:16465316

Fort, Diego A; Swatloski, Richard P; Moyna, Patrick; Rogers, Robin D; Moyna, Guillermo



Elucidation of Specific Binding Sites for Organofluorine Compounds in Peat Humic Acid using Reversed Heteronuclear Saturation Transfer Difference NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

In this presentation, a modified version of the NMR technique of Saturation Transfer Difference (STD) NMR is used to identify the distinct structural components of a peat humic acid mixture to which organic contaminants may bind. In our version of this experiment the direction of saturation transfer is reversed, from small molecules to macromolecules, and the transfer is between heteronuclei, from 19F nuclei on organofluorides to 1H nuclei on humic acid components, hence our term: reversed-Heteronuclear Saturation Transfer Difference (r-HSTD) spectroscopy. In the r-HSTD spectra of a humic acid mixture, only those components in contact with an organofluorine species will be observed, the identity of which can be inferred from the 1H chemical shift. This approach is used here to show that aromatic organofluoride compounds interact preferentially with lignin- derived material, whereas an aliphatic perfluorocarboxylic acid interacts nearly exclusively with protein-derived material. These findings have direct implications in the greater understanding of soil sorption phenomenon, as we present a powerful tool for the elucidation of the specific interactions through which organic pollutants bind to natural organic matter.

Longstaffe, J. G.; Simpson, M. J.; Maas, W.; Simpson, A. J.



Two-dimensional NMR spectroscopy reveals cation-triggered backbone degradation in polysulfone-based anion exchange membranes  

PubMed Central

Anion exchange membranes (AEMs) find widespread applications as an electrolyte and/or electrode binder in fuel cells, electrodialysis stacks, flow and metal-air batteries, and electrolyzers. AEMs exhibit poor stability in alkaline media; their degradation is induced by the hydroxide ion, a potent nucleophile. We have used 2D NMR techniques to investigate polymer backbone stability (as opposed to cation stability) of the AEM in alkaline media. We report the mechanism behind a peculiar, often-observed phenomenon, wherein a demonstrably stable polysulfone backbone degrades rapidly in alkaline solutions upon derivatization with alkaline stable fixed cation groups. Using COSY and heteronuclear multiple quantum correlation spectroscopy (2D NMR), we unequivocally demonstrate that the added cation group triggers degradation of the polymer backbone in alkaline via quaternary carbon hydrolysis and ether hydrolysis, leading to rapid failure. This finding challenges the existing perception that having a stable cation moiety is sufficient to yield a stable AEM and emphasizes the importance of the often ignored issue of backbone stability. PMID:23335629

Arges, Christopher G.; Ramani, Vijay



Two-dimensional NMR spectroscopy reveals cation-triggered backbone degradation in polysulfone-based anion exchange membranes.  


Anion exchange membranes (AEMs) find widespread applications as an electrolyte and/or electrode binder in fuel cells, electrodialysis stacks, flow and metal-air batteries, and electrolyzers. AEMs exhibit poor stability in alkaline media; their degradation is induced by the hydroxide ion, a potent nucleophile. We have used 2D NMR techniques to investigate polymer backbone stability (as opposed to cation stability) of the AEM in alkaline media. We report the mechanism behind a peculiar, often-observed phenomenon, wherein a demonstrably stable polysulfone backbone degrades rapidly in alkaline solutions upon derivatization with alkaline stable fixed cation groups. Using COSY and heteronuclear multiple quantum correlation spectroscopy (2D NMR), we unequivocally demonstrate that the added cation group triggers degradation of the polymer backbone in alkaline via quaternary carbon hydrolysis and ether hydrolysis, leading to rapid failure. This finding challenges the existing perception that having a stable cation moiety is sufficient to yield a stable AEM and emphasizes the importance of the often ignored issue of backbone stability. PMID:23335629

Arges, Christopher G; Ramani, Vijay



Using 15N-Ammonium to Characterise and Map Potassium Binding Sites in Proteins by NMR Spectroscopy  

PubMed Central

A variety of enzymes are activated by the binding of potassium ions. The potassium binding sites of these enzymes are very specific, but ammonium ions can often replace potassium ions in vitro because of their similar ionic radii. In these cases, ammonium can be used as a proxy for potassium to characterise potassium binding sites in enzymes: the 1H,15N spin-pair of enzyme-bound 15NH4+ can be probed by 15N-edited heteronuclear NMR experiments. Here, we demonstrate the use of NMR spectroscopy to characterise binding of ammonium ions to two different enzymes: human histone deacetylase 8 (HDAC8), which is activated allosterically by potassium, and the bacterial Hsp70 homologue DnaK, for which potassium is an integral part of the active site. Ammonium activates both enzymes in a similar way to potassium, thus supporting this non-invasive approach. Furthermore, we present an approach to map the observed binding site onto the structure of HDAC8. Our method for mapping the binding site is general and does not require chemical shift assignment of the enzyme resonances. PMID:24520048

Werbeck, Nicolas D; Kirkpatrick, John; Reinstein, Jochen; Hansen, D Flemming



Evolution of organic matter during composting of different organic wastes assessed by CPMAS {sup 13}C NMR spectroscopy  

SciTech Connect

In this paper, the evolution of organic matter (OM) during composting of different mixtures of various organic wastes was assessed by means of chemical analyses and CPMAS {sup 13}C NMR spectroscopy measured during composting. The trends of temperatures and C/N ratios supported the correct evolution of the processes. The CPMAS {sup 13}C NMR spectra of all composting substrates indicated a reduction in carbohydrates and an increase in aromatic, phenolic, carboxylic and carbonylic C which suggested a preference by microorganisms for easily degradable C molecules. The presence of hardly degradable pine needles in one of the substrates accounted for the lowest increase in alkyl C and the lowest reduction in carbohydrates and carboxyl C as opposite to another substrate characterized by the presence of a highly degradable material such as spent yeast from beer production, which showed the highest increase of the alkyl C/O-alkyl C ratio. The highest increase of COOH deriving by the oxidative degradation of cellulose was shown by a substrate composed by about 50% of plant residues. The smallest increases in alkyl C/O-alkyl C ratio and in polysaccharides were associated to the degradation of proteins and lipids which are major components of sewage sludge. Results obtained were related to the different composition of fresh organic substrates and provided evidence of different OM evolution patterns as a function of the initial substrate composition.

Caricasole, P. [Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529 (United States); Provenzano, M.R., E-mail: [Dipartimento di Biologia e Chimica Agroforestale ed Ambientale, Universita di Bari, Via G. Amendola 165/a, 70126 Bari (Italy); Hatcher, P.G. [Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529 (United States); Senesi, N. [Dipartimento di Biologia e Chimica Agroforestale ed Ambientale, Universita di Bari, Via G. Amendola 165/a, 70126 Bari (Italy)



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

NASA Astrophysics Data System (ADS)

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 was devoted to the formation of mixed structural units B(OP)4-n(OTe)n in the studied borophosphate glasses, where by the deconvolution of 11B MAS NMR spectra quantitative data on the number of BO3 and B(OP)4-n(OTe)n mixed structural units were obtained. Raman spectra showed shortening of phosphate chains both with increasing TeO2 and B2O3 content. Raman spectra also showed that with the replacement of P2O5 by B2O3 in the studied glasses TeO4 units are replaced by TeO3 units as the number of oxygen atoms in the glass decreases when the B2O3/P2O5 ratio increases.

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



The Effect of Antitumor Glycosides on Glioma Cells and Tissues as Studied by Proton HR-MAS NMR Spectroscopy  

PubMed Central

The effect of the treatment with glycolipid derivatives on the metabolic profile of intact glioma cells and tumor tissues, investigated using proton high resolution magic angle spinning (1H HR-MAS) nuclear magnetic resonance (NMR) spectroscopy, is reported here. Two compounds were used, a glycoside and its thioglycoside analogue, both showing anti-proliferative activity on glioma C6 cell cultures; however, only the thioglycoside exhibited antitumor activity in vivo. At the drug concentrations showing anti-proliferative activity in cell culture (20 and 40 µM), significant increases in choline containing metabolites were observed in the 1H NMR spectra of the same intact cells. In vivo experiments in nude mice bearing tumors derived from implanted C6 glioma cells, showed that reduction of tumor volume was associated with significant changes in the metabolic profile of the same intact tumor tissues; and were similar to those observed in cell culture. Specifically, the activity of the compounds is mainly associated with an increase in choline and phosphocholine, in both the cell cultures and tumoral tissues. Taurine, a metabolite that has been considered a biomarker of apoptosis, correlated with the reduction of tumor volume. Thus, the results indicate that the mode of action of the glycoside involves, at least in part, alteration of phospholipid metabolism, resulting in cell death. PMID:24194925

Garcia-Alvarez, Isabel; Garrido, Leoncio; Romero-Ramirez, Lorenzo; Nieto-Sampedro, Manuel; Fernandez-Mayoralas, Alfonso; Campos-Olivas, Ramon



NMR Spectroscopy of the Hydrated Layer of Composite Particles Based on Nanosized Al2O3 and Vitreous Humor  

NASA Astrophysics Data System (ADS)

The hydrated layer of composite particles prepared using Al2O3 and cattle vitreous humor was investigated using NMR spectroscopy. It was found that water bound to Al2O3 nanoparticles was present in the form of clusters with different degrees of association and energies of interaction with the surface. Water bound to the surface of the Al2O3/vitreous humor composite became more uniform upon immobilization of vitreous humor components on the surface of the Al2O3. With this, the clusters of adsorbed water had characteristics that were close to those found in air and weakly polar CHCl3 media. Addition of polar CH3CN led to the formation of very small water clusters. PMR spectra of the surface of the Al2O3/vitreous humor composite in the presence of trifluoroacetic acid differentiated four types of hydrated structures that differed in the degree of water association.

Turov, V. V.; Gerashchenko, I. I.; Markina, A. I.



Parahydrogen-induced polarization transfer to 19F in perfluorocarbons for 19F?NMR spectroscopy and MRI.  


Fluorinated substances are important in chemistry, industry, and the life sciences. In a new approach, parahydrogen-induced polarization (PHIP) is applied to enhance (19)F?MR signals of (perfluoro-n-hexyl)ethene and (perfluoro-n-hexyl)ethane. Unexpectedly, the end-standing CF3 group exhibits the highest amount of polarization despite the negligible coupling to the added protons. To clarify this non-intuitive distribution of polarization, signal enhancements in deuterated chloroform and acetone were compared and (19)F-(19)F?NOESY spectra, as well as (19)F T1 values were measured by NMR spectroscopy. By using the well separated and enhanced signal of the CF3 group, first (19)F?MR images of hyperpolarized linear semifluorinated alkenes were recorded. PMID:23526596

Plaumann, Markus; Bommerich, Ute; Trantzschel, Thomas; Lego, Denise; Dillenberger, Sonja; Sauer, Grit; Bargon, Joachim; Buntkowsky, Gerd; Bernarding, Johannes



Interaction of electrolyte molecules with carbon materials of well-defined porosity: characterization by solid-state NMR spectroscopy.  


Electrochemical double-layer capacitors (EDLCs or supercapacitors) are of special potential interest with respect to energy storage. Nearly all EDLCs make use of porous carbons as electrode materials. Further tuning of their performance in EDLC applications requires a better understanding of their properties. In particular, the understanding of the interactions between carbon-based materials and electrolyte solutions is of fundamental interest with respect to future applications. Since the capacitance of carbon-based electrode materials is known to depend on the pore size, we have studied different porous carbon materials of well-defined, variable pore size loaded with 1 M TEABF4 in acetonitrile or with pure acetonitrile using solid-state magic angle spinning (MAS) (1)H, (11)B, and (13)C NMR spectroscopy. PMID:23925570

Borchardt, Lars; Oschatz, Martin; Paasch, Silvia; Kaskel, Stefan; Brunner, Eike




PubMed Central

The catalytic subunit of cAMP-dependent protein kinase A (PKA-C) is an exquisite example of a single molecule allosteric enzyme, where classical and modern views of allosteric signaling merge. In this chapter, we describe the mapping of PKA-C conformational dynamics and allosteric signaling in the free and bound states using a combination of NMR spectroscopy and molecular dynamics simulations. We show that ligand binding affects the enzyme’s conformational dynamics, shaping the free-energy landscape toward the next stage of the catalytic cycle. While nucleotide and substrate binding enhance the enzyme’s conformational entropy and define dynamically committed states, inhibitor binding attenuates the internal dynamics in favor of enthalpic interactions and delineates dynamically quenched states. These studies support a central role of conformational dynamics in many aspects of enzymatic turnover and suggest future avenues for controlling enzymatic function. PMID:22607761




Orientational microdynamics and magnetic-field-induced ordering of clay platelets detected by 2H NMR spectroscopy.  


The orientation of montmorillonite clays induced by a static magnetic field is quantified by using (2)H NMR spectroscopy. Indeed, the residual quadrupolar splitting of the (2)H resonance line measured for heavy water is a direct consequence of the specific orientation of the clay platelets in the static magnetic field. In the dilute regime, this residual splitting increases linearly with clay concentration, which confirms that the clay/clay electrostatic repulsions remain negligible by comparison with the diamagnetic coupling of these anisotropic platelets. At higher concentration, the electrostatic repulsion between clay particles markedly enhances the detected splitting. Such enhancement is well predicted by numerical simulations. By varying the size of the clay platelets and the strength of the static magnetic field, it is possible to evaluate the order of magnitude of the diamagnetic susceptibility of these anisotropic colloids. PMID:20047274

Porion, Patrice; Faugère, Anne Marie; Michot, Laurent J; Paineau, Erwan; Delville, Alfred



Determination of the (Na+) Sternheimer antishielding factor by 23Na NMR spectroscopy on sodium oxide chloride, Na3OCl.  


The (Na+) Sternheimer antishielding factor gammainifinity (Na+) was determined by 23Na NMR spectroscopy on sodium oxide-chloride, Na3OCl. The quadrupolar coupling constant of the sodium ion in Na3OCI was determined to QCC = 11.34 MHz, which presents the largest coupling constant of a sodium nucleus observed so far. Applying a simple point charge model, the largest principal value of the electric field gradient at the sodium site was calculated to V(zz) = -6.76762 x 10(20) V/m2. From these values we calculated the (Na+) Sternheimer antishielding factor to gammainifinity (Na+)= -5.36. In sodium oxide, Na2O, we observed an isotropic chemical shift of deltaCS = 55.1 ppm, referenced to 1 M aqueous NaCI (delta = 0 ppm). PMID:10928632

Klösters, G; Jansen, M



Raman Spectroscopy and Solid State NMR Characterization of Carbonates and Metal-Oxide Clusters  

NASA Astrophysics Data System (ADS)

Presented here is data showing the utility of combining Raman spectroscopy and solid-state Nuclear Magnetic Resonance. These techniques were combined to study local structure of carbonate minerals and metal oxides.

Moore, J. K.; Hammann, B. A.; Surface, J. A.; Ma, Z. L.; Hayes, S. E.



Methods for Increasing Sensitivity and Throughput of Solid-State NMR Spectroscopy of Pharmaceutical Solids  

E-print Network

Solid-state nuclear magnetic resonance (SSNMR) spectroscopy has been demonstrated to be a powerful technique for investigating solid dosage formulations. SSNMR has the ability to determine physical form, molecular structure, ...

Schieber, Loren



Solid-state NMR analysis of membrane proteins and protein aggregates by proton detected spectroscopy  

PubMed Central

Solid-state NMR has emerged as an important tool for structural biology and chemistry, capable of solving atomic-resolution structures for proteins in membrane-bound and aggregated states. Proton detection methods have been recently realized under fast magic-angle spinning conditions, providing large sensitivity enhancements for efficient examination of uniformly labeled proteins. The first and often most challenging step of protein structure determination by NMR is the site-specific resonance assignment. Here we demonstrate resonance assignments based on high-sensitivity proton-detected three-dimensional experiments for samples of different physical states, including a fully-protonated small protein (GB1, 6 kDa), a deuterated microcrystalline protein (DsbA, 21 kDa), a membrane protein (DsbB, 20 kDa) prepared in a lipid environment, and the extended core of a fibrillar protein (?-synuclein, 14 kDa). In our implementation of these experiments, including CONH, CO(CA)NH, CANH, CA(CO)NH, CBCANH, and CBCA(CO)NH, dipolar-based polarization transfer methods have been chosen for optimal efficiency for relatively high protonation levels (full protonation or 100 % amide proton), fast magic-angle spinning conditions (40 kHz) and moderate proton decoupling power levels. Each H–N pair correlates exclusively to either intra- or inter-residue carbons, but not both, to maximize spectral resolution. Experiment time can be reduced by at least a factor of 10 by using proton detection in comparison to carbon detection. These high-sensitivity experiments are especially important for membrane proteins, which often have rather low expression yield. Proton-detection based experiments are expected to play an important role in accelerating protein structure elucidation by solid-state NMR with the improved sensitivity and resolution. PMID:22986689

Nieuwkoop, Andrew J.; Berthold, Deborah A.; Comellas, Gemma; Sperling, Lindsay J.; Tang, Ming; Shah, Gautam J.; Brea, Elliott J.; Lemkau, Luisel R.



NMR spectroscopy: structure elucidation of cycloelatanene A: a natural product case study.  


The structure elucidation of new secondary metabolites derived from marine and terrestrial sources is frequently a challenging task. The hurdles include the ability to isolate stable secondary metabolites of sufficient purity that are often present in <0.5 % of the dry weight of the sample. This usually involves a minimum of several chromatographic purification steps. The second issue is the stability of the compound isolated. It must always be assumed when dealing with the isolation of natural products that the compound may rapidly degrade during and/or after the isolation, due to sensitivity to light, air oxidation, and/or temperature. In this way, precautions need to be taken, as much as possible to avoid any such chemical inter-conversions and/or degradations. Immediately after purification, the next step is to rapidly acquire all analytical spectroscopic data in order to complete the characterization of the isolated secondary metabolite(s), prior to any possible decomposition. The final hurdle in this multiple step process, especially in the acquisition of the NMR spectroscopic and other analytical data (mass spectra, infrared and ultra-violet spectra, optical rotation, etc.), is to assemble the structural moieties/units in an effort to complete the structure elucidation. Often ambiguity with the elucidation of the final structure remains when structural fragments identified are difficult to piece together on the basis of the HMBC NMR correlations or when the relative configuration cannot be unequivocally identified on the basis of NOE NMR enhancements observed. Herein, we describe the methodology used to carry out the structure elucidation of a new C16 chamigrene, cycloelatanene A (5) which was isolated from the southern Australian marine alga Laurencia elata (Rhodomelaceae). The general approach and principles used in the structure determination of this compound can be applied to the structure elucidation of other small molecular weight compounds derived from either natural or synthetic sources. PMID:23963906

Urban, Sylvia; Dias, Daniel Anthony



Residue Ionization in LpxC Directly Observed by 67Zn NMR Spectroscopy  

PubMed Central

The pH dependence of the solid-state 67Zn NMR lineshapes has been measured for both wild type (WT) and the H265A mutant of Aquifex aeolicus LpxC, each in the absence of substrate (resting state). The 67Zn NMR spectrum of WT LpxC at pH 6 (prepared at 0 °C) contains two overlapping quadrupole lineshapes with Cq's of 10 and 12.9 MHz, while the spectrum measured for the sample prepared at a pH near 9 (at 0 °C) is dominated by the appearance of a third species with a Cq of 14.3 MHz. These findings are consistent with the two pKa values previously observed by the bell-shaped dependence of the LpxC-catalyzed reaction. Based on comparison of the experimental results with predictions from QM/MM modeling we suggest that pKa1 (low pH) represents the ionization of Glu78 and pKa2 (high pH) reflects the ionization of another active site residue located near the zinc ion, such as His265. These results are also consistent with water being bound to the Zn2+ throughout this pH range. The 67Zn NMR spectra of the H265A mutant appear to be pH independent with a Cq of 9.55 MHz being sufficient to describe both low and high pH data. The QM/MM models of the H265A mutant suggest that over this pH range water is bound to the zinc, while Glu78 is protonated. PMID:18761443

Lipton, Andrew S.; Heck, Robert W.; Hernick, Marcy; Fierke, Carol A.; Ellis, Paul D.



Direct detection of aluminosilicate species in aqueous solution by silicon-29 and aluminum-27 NMR spectroscopy  

Microsoft Academic Search

Silicon-29 NMR spectra of solutions containing 1 mol kg⁻¹ SiOâ and 0.07 mol kg⁻¹ Al in 2.4 mol kg⁻¹ aqueous NaOH at 5°C show five bands which are attributable to dissolved species containing Si-O-Al links. The major aluminosilicate species in solution appear to be Al-substituted derivatives of the silicate dimer, cyclic trimer, cyclic tetramer, and acyclic trimer. ²⁹Si spectra suggest

Stephen D. Kinrade; Thomas W. Swaddle



Determination of metabolite profiles in tropical wines by 1H NMR spectroscopy and chemometrics.  


Traditionally, wines are produced in temperate climate zones, with one harvest per year. Tropical wines are a new concept of vitiviniculture that is being developed, principally in Brazil. The new Brazilian frontier is located in the northeast region (São Francisco River Valley) in Pernambuco State, close to the equator, between 8 and 9 degrees S. Compared with other Brazilian and worldwide vineyards, the grapes of this region possess peculiar characteristics. The aim of this work is a preliminary study of commercial São Francisco River Valley wines, analyzing their metabolite profiles by (1)H NMR and chemometric methods. PMID:19810052

da Silva Neto, Humberto G; da Silva, João B P; Pereira, Giuliano E; Hallwass, Fernando



Characterizing RNA Dynamics at Atomic Resolution Using Solution-state NMR Spectroscopy  

PubMed Central

Many recently discovered non-coding RNAs do not fold into a single native conformation, but rather, sample many different conformations along their free energy landscape to carry out their biological function. Unprecedented insights into the RNA dynamic structure landscape are provided by solution-state NMR techniques that measure the structural, kinetic, and thermodynamic characteristics of motions spanning picosecond to second timescales at atomic resolution. From these studies a basic description of the RNA dynamic structure landscape is emerging, bringing new insights into how RNA structures change to carry out their function as well as applications in RNA-targeted drug discovery and RNA bioengineering. PMID:22036746

Bothe, Jameson R.; Nikolova, Evgenia N.; Eichhorn, Catherine D.; Chugh, Jeetender; Hansen, Alexandar L.; Al-Hashimi, Hashim M.



Indirectly detected heteronuclear correlation solid-state NMR spectroscopy of naturally abundant 15N nuclei.  


Two-dimensional indirectly detected through-space and through-bond (1)H{(15)N} solid-state NMR experiments utilizing fast magic angle spinning (MAS) and homonuclear multipulse (1)H decoupling are evaluated. Remarkable efficiency of polarization transfer can be achieved at a MAS rate of 40 kHz by both cross-polarization and INEPT, which makes these methods applicable for routine characterizations of natural abundance solids. The first measurement of 2D (1)H{(15)N} HETCOR spectrum of natural abundance surface species is also reported. PMID:24287060

Althaus, Stacey M; Mao, Kanmi; Stringer, John A; Kobayashi, Takeshi; Pruski, Marek



Two-dimensional NMR spectroscopy as a tool to link soil organic matter composition to ecosystem processes  

NASA Astrophysics Data System (ADS)

Environmental factors (e.g. temperature and moisture) and the size and composition of soil microbial populations are often considered the main drivers of soil organic matter (SOM) mineralization. Less consideration is given to the role of SOM as a substrate for microbial metabolism and the importance of the organo-chemical composition of SOM on decomposition. In addition, a fraction of the SOM is often considered as recalcitrant to mineralization leading to accumulation of SOM. However, recently the concept of intrinsic recalcitrance of SOM to mineralization has been questioned. The challenge in investigating the role of SOM composition on its mineralization to a large extent stems from the difficulties in obtaining high resolution characterization of a very complex matrix. 13C nuclear magnetic resonance (NMR) spectroscopy is a widely used tool to characterize SOM. However, SOM is a very complex mixture and in the resulting 13C NMR spectra, the identified functional groups may represent different molecular fragments that appear in the same spectral region leading to broad peaks. These overlaps defy attempts to identify molecular moieties, and this makes it impossible to derive information at a resolution needed for evaluating e.g. recalcitrance of SOM. Here we applied a method, developed in wood science for the pulp paper industry, to achieve a better characterization of SOM. We directly dissolved finely ground organic layers of boreal forest floors-litters, fibric and humic horizons of both coniferous and broadleaved stands-in dimethyl sulfoxide and analyzed the resulting solution with a two-dimensional (2D) 1H-13C NMR experiment. We will discuss methodological aspects related to the ability to identify and quantify individual molecular moieties in SOM. We will demonstrate how the spectra resolve signals of CH groups in a 2D plane determined by the 13C and 1H chemical shifts, thereby vastly increasing the resolving power and information content of NMR spectra. The obtained 2D spectra resolve overlaps observed in 1D 13C spectra, so that hundreds of distinct CH moieties can be observed and many individual molecular fragments can be identified. For instance, in the aromatic spectral region, signals originating from various lignin monomers and unsaturated compounds can be resolved. This yields a detailed chemical fingerprint of the SOM samples, and valuable insights on molecular structures. We observed differences in the respective aromatic region of the 2D spectra of the litter layers and the fibric and humic horizons, in relation with humification processes. We were also able to relate the cross-peak complexity and abundance patterns of identifiable molecular moieties to variability in the temperature response of organic matter degradation, as assessed by Q10. To conclude, solution-state 2D NMR spectroscopy is a highly promising new tool to characterize SOM composition at the molecular level, which opens completely new possibilities to link SOM molecular composition to ecosystem processes, and their responses to environmental changes.

Soucemarianadin, Laure; Erhagen, Björn; Öquist, Mats; Nilsson, Mats; Schleucher, Jürgen



Screening protein - Single stranded RNA complexes by NMR spectroscopy for structure determination?  

PubMed Central

In the past few years, RNA molecules have been revealed to be at the center of numerous biological processes. Long considered as passive molecules transferring genetic information from DNA to proteins, it is now well established that RNA molecules play important regulatory roles. Associated with that, the number of identified RNA binding proteins (RBPs) has increased considerably and mutations in RNA molecules or RBP have been shown to cause various diseases, such as cancers. It is therefore crucial to understand at the molecular level how these proteins specifically recognise their RNA targets in order to design new generation drug therapies targeting protein–RNA complexes. Nuclear magnetic resonance (NMR) is a particularly well-suited technique to study such protein–RNA complexes at the atomic level and can provide valuable information for new drug discovery programs. In this article, we describe the NMR strategy that we and other laboratories use for screening optimal conditions necessary for structural studies of protein-single stranded RNA complexes, using two proteins, Sam68 and T-STAR, as examples. PMID:24096002

Foot, Jaelle N.; Feracci, Mikael; Dominguez, Cyril



The nature of fatty acid interaction with a polyelectrolyte-surfactant pair revealed by NMR spectroscopy.  


The interaction mechanisms of an oppositely charged polyelectrolyte-surfactant pair and dodecanoic (lauric) acid (LA) were experimentally investigated using a combination of nuclear magnetic resonance (NMR) techniques. It is observed that LA significantly affects the interaction between the anionic surfactant sodium dodecylethersulfate (SDES) and the cationic polymer guar modified with grafted hydroxypropyl trimethylammonium chloride (Jaguar C13 BF). Typically, oppositely charged polymers and surfactants interact electrostatically at a certain surfactant concentration known as the critical aggregation concentration (CAC). Once the polymer is neutralized by the surfactant, an insoluble complex (precipitate) is observed (phase separation), and, at concentrations beyond the surfactant critical micellar concentration (CMC'), the system returns to a one phase entity. In a system in which a mixture of SDES-LA is added to the polymer, NMR data show that below the neutralization onset, some of the polymer interacts with SDES, while some of the polymer is adsorbed at the surface of LA solid aggregates present in the system. Furthermore, SDES is found to aggregate in a lamellar-like structure at the polymer side chain prior to the SDES CMC'. Above the SDES (CMC'), LA is solubilized and incorporated at the palisade region of SDES micelles. Analysis of (1)H resonances provided estimated concentrations of all species in the system phases at all stages of interaction. PMID:25109504

Martinez-Santiago, Jose; Totland, Christian; Ananthapadmanabhan, Kavssery P; Tsaur, Liang; Somasundaran, Ponisseril



Quantitative analysis of polymer mixtures in solution by pulsed field-gradient spin echo NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Pulsed Field-Gradient Spin Echo (PGSE) NMR, which associates to a spectral dimension the measure of diffusion coefficients, is a convenient technique for mixture analysis. Unfortunately, because of relaxation, the quantification of mixtures by PGSE NMR is far from straightforward for mixtures with strong spectral overlap. Antalek (J. Am. Chem. Soc. 128 (2006) 8402-8403) proposed a quantification strategy based on DECRA analysis and extrapolation to zero of the diffusion delay. More recently, Barrère et al. (J. Magn. Reson. 216 (2012) 201-208) presented a new strategy based also on DECRA and on the renormalization of the intensities using estimates of the T1 and T2 relaxation times. Here we report an alternative quantification approach in which the fractions are obtained by analyzing the PGSE attenuation profile with a general Stejskal-Tanner equation that explicitly includes the relaxation effects. The required values of T1 and T2 relaxation times are either independently measured with conventional sequences or determined, along with the fractions and the diffusion coefficients, from the simultaneous analysis of up to 6 PGSE data sets recorded with different diffusion delays. This method yields errors lower than 3% for the fractions, even for complete spectral overlap, as demonstrated on model binary and ternary mixtures of polystyrene in the case of a convection compensating double stimulated echo (DSTE) sequence.

Van Lokeren, Luk; Ben Sassi, Hanen; Van Assche, Guy; Ribot, François



Quantitative analysis of polymer mixtures in solution by pulsed field-gradient spin echo NMR spectroscopy.  


Pulsed Field-Gradient Spin Echo (PGSE) NMR, which associates to a spectral dimension the measure of diffusion coefficients, is a convenient technique for mixture analysis. Unfortunately, because of relaxation, the quantification of mixtures by PGSE NMR is far from straightforward for mixtures with strong spectral overlap. Antalek (J. Am. Chem. Soc. 128 (2006) 8402-8403) proposed a quantification strategy based on DECRA analysis and extrapolation to zero of the diffusion delay. More recently, Barrère et al. (J. Magn. Reson. 216 (2012) 201-208) presented a new strategy based also on DECRA and on the renormalization of the intensities using estimates of the T1 and T2 relaxation times. Here we report an alternative quantification approach in which the fractions are obtained by analyzing the PGSE attenuation profile with a general Stejskal-Tanner equation that explicitly includes the relaxation effects. The required values of T1 and T2 relaxation times are either independently measured with conventional sequences or determined, along with the fractions and the diffusion coefficients, from the simultaneous analysis of up to 6 PGSE data sets recorded with different diffusion delays. This method yields errors lower than 3% for the fractions, even for complete spectral overlap, as demonstrated on model binary and ternary mixtures of polystyrene in the case of a convection compensating double stimulated echo (DSTE) sequence. PMID:23567882

Van Lokeren, Luk; Ben Sassi, Hanen; Van Assche, Guy; Ribot, François



31P NMR spectroscopy of rat organs, in situ, using chronically implanted radiofrequency coils.  

PubMed Central

A technique for making 31P NMR spectroscopic measurements in rat kidney, heart, and liver in vivo is presented. Two-turn solenoid coils were surgically implanted around the organ sufficiently in advance of NMR experiments to allow recovery of the animal. These chronically implanted coils allowed acquisition of high-resolution spectra at 40.5 and 97.3 MHz. No resolution improvement occurred at the higher field. Spectra were stable for up to 24 hr, during which time a variety of experiments could be performed. By accumulating spectra at 10-min intervals, the effects of intraperitoneal fructose injections were monitored; in kidney and liver, a rapid increase in sugar phosphates at the expense of Pi and ATP resulted. Fructose had no effect on heart metabolite levels. Spectra from the heart in vivo were obtained at systole and diastole by gating the spectrometer to the aortic pressure wave; no differences in phosphate metabolites were detected. Finally, saturation transfer techniques were used to monitor the rate of ATP synthesis in the kidney. The unidirectional rate constant for the conversion of Pi to ATP was 0.12 +/- 0.03 sec-1. Images PMID:6584867

Koretsky, A P; Wang, S; Murphy-Boesch, J; Klein, M P; James, T L; Weiner, M W



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


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



Probing Quadrupolar Nuclei by Solid-State NMR Spectroscopy: Recent Advances  

SciTech Connect

Solid-state nuclear magnetic resonance (NMR) of quadrupolar nuclei has recently undergone remarkable development of capabilities for obtaining structural and dynamic information at the molecular level. This review summarizes the key achievements attained during the last couple of decades in solid-state NMR of both integer spin and half-integer spin quadrupolar nuclei. We provide a concise description of the first- and second-order quadrupolar interactions, and their effect on the static and magic angle spinning (MAS) spectra. Methods are explained for efficient excitation of single- and multiple-quantum coherences, and acquisition of spectra under low- and high-resolution conditions. Most of all, we present a coherent, comparative description of the high-resolution methods for half-integer quadrupolar nuclei, including double rotation (DOR), dynamic angle spinning (DAS), multiple-quantum magic angle spinning (MQMAS), and satellite transition magic angle spinning (STMAS). Also highlighted are methods for processing and analysis of the spectra. Finally, we review methods for probing the heteronuclear and homonuclear correlations between the quadrupolar nuclei and their quadrupolar or spin-1/2 neighbors.

Fernandez, Christian; Pruski, Marek



Kinetic analyses of liver phosphatidylcholine and phosphatidylethanolamine biosynthesis using (13)C NMR spectroscopy.  


Choline and ethanolamine are substrates for de novo synthesis of phosphatidylcholine (PtdC) and phosphatidylethanolamine (PtdE) through the CDP-choline and CDP-ethanolamine pathways. In liver, PtdE can also be converted to PtdC by PtdE N-methyltransferase (PEMT). We investigated these kinetics in rat liver during a 60 min infusion with (13)C-labeled choline and ethanolamine. NMR analyses of liver extracts provided concentrations and (13)C enrichments of phosphocholine (Pcho), phosphoethanolamine (Peth), PtdC, and PtdE. Kinetic models showed that the de novo and PEMT pathways are 'channeled' processes. The intermediary metabolites directly derived from exogenous choline and ethanolamine do not completely mix with the intracellular pools, but are preferentially used for phospholipid synthesis. Of the newly synthesized PtdC, about 70% was derived de novo and 30% was by PEMT. PtdC and PtdE de novo syntheses displayed different kinetics. A simple model assuming constant fluxes yielded a modest fit to the data; allowing upregulated fluxes significantly improved the fit. The ethanolamine-to-Peth flux exceeded choline-to-Pcho, and the rate of PtdE synthesis (1.04 micromol/h/g liver) was 2-3 times greater than that of PtdC de novo synthesis. The metabolic pathway information provided by these studies makes the NMR method superior to earlier radioisotope studies. PMID:11880242

Reo, Nicholas V; Adinehzadeh, Mehdi; Foy, Brent D



Structural Studies of N-Terminal Mutants of Connexin 32 Using 1H NMR Spectroscopy  

PubMed Central

The amino terminus of gap junction proteins, connexins, plays a fundamental role in voltage gating and ion permeation. We have previously shown with 1H NMR that the structure of the N-terminus of functional connexin molecules contains a flexible turn around G12 (Arch. Biochem. Biophys.490:9,2009) allowing the N-terminus to form a portion of the channel pore near the cytoplasmic entrance. The mutants of nonfunctional connexin molecules G12S and G12Y were found to prevent this turn. Previous functional studies of loci at which Cx32 mutations cause a peripheral neuropathy, Charcot-Marie-Tooth disease, have shown that G12S is not plasma membrane inserted. Presently, we solve the structure of nonfunctional Connexin 32 mutants W3D and Y7D which do not appear to be membrane inserted. Using 2D 1H NMR, we report that similar to G12S and G12Y, alterations in hydrophobic sidechain interactions disrupt (Y7D) or constrain (W3D) the flexible turn around G12. The alteration in the open turn around residue 12, observed in all nonfunctional mutants G12S, G12Y, W3D and Y7D correlates with loss of function. We propose that loss of the open turn causes the N-terminus to extend out of the channel pore and this misfolding may target mutants for destruction in the endoplasmic reticulum. PMID:22705201

Kalmatsky, D. B.; Batir, Y.; Bargiello, T. A.; Dowd, T.L.



Probing the Geometry and Interconnectivity of Pores in Organic Aerogels Using Hyperpolarized 129Xe NMR Spectroscopy  

SciTech Connect

Aerogels represent a class of novel open-pore materials with high surface area and nanometer pore sizes. They exhibit extremely low mass densities, low thermal conductivity, good acoustic insulation, and low dielectric constants. These materials have potential applications in catalysis, advanced separation techniques, energy storage, environmental remediation, and as insulating materials. Organic aerogels are stiffer and stronger than silica aerogels and are better insulators with higher thermal resistance. Resorcinol-Formaldehyde (RF) aerogels are typically prepared through the base-catalyzed sol-gel polymerization of resorcinol with formaldehyde in aqueous solution to produce gels, which are then dried in supercritical CO2.1,2 The [resorcinol]/ [catalyst] (R/C) ratio of the starting sol-gel solution has been determined to be the dominant factor that affects the properties of RF aerogels. Since the unique microstructures of aerogels are responsible for their unusual properties, characterizing the detailed porous structures and correlating them with the processing parameters are vital to establish rational design principles for novel organic aerogels with tailored properties. In this communication we report the first use of hyperpolarized (HP) 129Xe NMR to probe the geometry and interconnectivity of pores in RF aerogels and to correlate these with synthetic conditions. Our work demonstrates that HP 129Xe NMR is so far the only method for accurately measuring the free volume-to-surface-area (Vg/S) ratios for soft mesoporous materials without using any geometric models.

Moudrakovski, Igor L.; Wang, Li Q.; Baumann, T.; Satcher, J. H.; Exarhos, Gregory J.; Ratcliffe, C. I.; Ripmeester, J. A.



Spatially Localized, One- and Two-Dimensional NMR Spectroscopy and in VivoApplication to Human Muscle  

NASA Astrophysics Data System (ADS)

The localized 1H MR spectrum of human muscle has recently been reported to feature unassigned, orientation-dependent resonance lines. For their characterization in vivo,various NMR techniques were combined with 3D spatial localization: 2D-J spectroscopy, zero-quantum- and Zeeman-order-filtering, double-quantum-filtering, 2D-constant-time COSY, dipolar-order filtering, and 2D-longitudinal-order separated spectroscopy. The successful implementation of these methods on a whole-body MR system and their application to study human subjects is described. 1H MR spectra of human muscle were found to feature residual dipolar couplings and anisotropic susceptibilities which render resonance frequencies, phases, and—with some sequences—signal intensities orientation dependent. Two of the unidentified resonances unequivocally form a dipolar doublet of two equivalent protons, centered at 3.93 ppm. All unknown as well as previously assigned peaks in the range between 2.7 and 3.6 ppm are either subject to dipolar coupling themselves or overlap with spectral contributions of metabolites involved in dipolar coupling. The methyl protons of creatine are likely to be subject to residual dipolar coupling and do therefore form a dipolar triplet and not a singlet as previously assumed. Finally, X3, a further unidentified peak at 3.5 ppm, appears to be part of a multiplet with its center at 3.3 ppm and overlapping the trimethylammonium resonance.

Kreis, Roland; Boesch, Chris


Pleural effusion lipoproteins measured by NMR spectroscopy for diagnosis of exudative pleural effusions: a novel tool for pore-size estimation.  


High-resolution proton nuclear magnetic resonance (NMR) spectrometry of biofluids has been increasingly used in laboratory diagnosis of various diseases. In this study, we extended the use of (1)H NMR spectroscopy for laboratory diagnosis of exudative pleural effusions using pleural fluids. We compared this new NMR-based test with Light's criteria, the current gold standard for laboratory diagnosis of exudative pleural effusions. We analyzed 67 samples of pleural effusions from patients with pulmonary malignancy (N = 32), pulmonary tuberculosis (N = 18), and congestive heart failure (N = 17). The metabolomes of pleural effusions were analyzed using (1)H NMR spectroscopy on a Bruker 600 MHz spectrometer. Through a metabolome-wide association approach with filtering of insignificant markers (p value <4 × 10(-6)) and multivariate analysis (principal component analysis and orthogonal partial least squares-discriminant analysis), lipoprotein was found to be the best biomarker that distinguished exudates from transudates. Using NMR-based lipoprotein profiling to classify exudative pleural effusions from transudates, the area-under-receiver operating characteristic (ROC) curve was 0.96 with sensitivity of 98%, specificity of 88%, and accuracy of 98%. In contrast, the current gold standard, Light's criteria, give a specificity of only 65% at the same sensitivity level of 98%. Using the principle of size exclusion, NMR-based lipoprotein profiling of pleural fluids has an unprecedented diagnostic performance superiority over the Light's criteria. The capillary leaks secondary to inflammation result in a larger pleural pore-size, which allows the large-sized lipoproteins to accumulate in exudative pleural effusions. In contrast, the pleural permeability is intact in transudates, which allow only small-sized lipoproteins to pass into the pleural effusions. The average capillary pore-size of the pleura can therefore be determined by using NMR-based lipoprotein profiling of pleural fluids. We believe this new test will change the current clinical practice for management of pleural effusions and will become a new standard for clinical practice. PMID:25072840

Lam, Ching-Wan; Law, Chun-Yiu



X-ray crystallography characterization, vibrational spectroscopy, NMR spectra and quantum chemical DFT/HF study of N,N'-di(2-methoxyphenyl)formamidine.  


The title compound, N,N'-di(2-methoxyphenyl)formamidine (DMPF) was synthesized and characterized by FT-IR, FT-Raman, (1)H NMR, (13)C NMR spectroscopy and X-ray single crystal diffraction. The results show that the compound crystallizes in an orthorhombic system, with space group of Pbca and eight molecules in the unit cell. The unit cell parameters are: a=11.1118 (7)A, b=14.9878 (9)A and c=16.2851 (10)A. The molecular geometry, the normal mode frequencies and corresponding vibrational assignments of DMPF at the ground state were performed by HF and B3LYP methods with 6-311+G(d,p) basis set. It was observed that the bond lengths and angles in the molecule, obtained by X-ray at the level of theory, were in good agreement with those of the experiment. A detailed interpretation of the infrared and Raman spectra of DMPF was reported. The (13)C NMR and (1)H NMR of DMPF have been calculated using HF and B3LYP methods with 6-311+G(d,p) basis set. Comparison between experimental and theoretical results showed that B3LYP/6-311+G(d,p) method is able to provide more satisfactory results for predicting IR, Raman, (1)H NMR and (13)C NMR properties. PMID:20409749

Rofouei, M K; Sohrabi, N; Shamsipur, M; Fereyduni, E; Ayyappan, S; Sundaraganesan, N



The Discovery-Oriented Approach to Organic Chemistry. 4. Epoxidation of p-Methoxy-trans-b-methylstyrene: An Exercise in NMR and IR Spectroscopy for Sophomore Organic Laboratories  

NASA Astrophysics Data System (ADS)

Epoxidation of alkenes using peroxyacids is one of the most fundamental reactions in organic chemistry, yet there are very few examples of laboratory experiments that illustrate this important reaction. We have developed a discovery-oriented lab experiment that illustrates epoxidation of alkenes as well as the reactivity of epoxides toward acids. The experiment involves reaction of p-methoxy-trans-b-methylstyrene (trans-anethole) with m-chloroperoxybenzoic acid (MCPBA), in both the absence and presence of a buffer, followed by product identification using 1H NMR, 13C NMR, and IR spectroscopy. The added element of discovery ensures that students' interest and enthusiasm are retained.

Centko, Rebecca S.; Mohan, Ram S.



The heterogeneous structural behavior of E7 from HPV16 revealed by NMR spectroscopy.  


The E7 protein from human papillomavirus (HPV) plays a key role in oncogenesis; for this reason, it is a target of great biomedical interest. To date, no high resolution information is available for the full protein. We present here the NMR characterization of the entire E7 from HPV16, one of the most oncogenic variants of the virus. The protein is very heterogeneous in terms of structural and dynamic properties with a highly flexible N-terminal module and a more structured C terminus. This opens possibilities for studies of molecular-level interactions and post-translational modifications of the protein to unravel functional details that might be linked to its highly oncogenic potential. PMID:23940009

Calçada, Eduardo O; Felli, Isabella C; Hošek, Tomáš; Pierattelli, Roberta



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

SciTech Connect

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

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



Dynamically committed, uncommitted, and quenched states encoded in protein kinase A revealed by NMR spectroscopy  

PubMed Central

Protein kinase A (PKA) is a ubiquitous phosphoryl transferase that mediates hundreds of cell signaling events. During turnover, its catalytic subunit (PKA-C) interconverts between three major conformational states (open, intermediate, and closed) that are dynamically and allosterically activated by nucleotide binding. We show that the structural transitions between these conformational states are minimal and allosteric dynamics encode the motions from one state to the next. NMR and molecular dynamics simulations define the energy landscape of PKA-C, with the substrate allowing the enzyme to adopt a broad distribution of conformations (dynamically committed state) and the inhibitors (high magnesium and pseudosubstrate) locking it into discrete minima (dynamically quenched state), thereby reducing the motions that allow turnover. These results unveil the role of internal dynamics in both kinase function and regulation. PMID:21471451

Masterson, Larry R.; Shi, Lei; Metcalfe, Emily; Gao, Jiali; Taylor, Susan S.; Veglia, Gianluigi



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

NASA Astrophysics Data System (ADS)

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. The correctness of assignments was verified by GIAO DFT calculations of shielding constants. The differences between the solution and solid state chemical shift values were explained in terms of orientation of OH groups and intramolecular hydrogen bonds. The splitting of the C1 dbnd O resonance shows that there exists a polymorphism in the solid phase, which might be due to the formation of intramolecular hydrogen bond involving carbonyl or methoxy oxygen (i.e. C10 sbnd OH⋯O dbnd C or C10 sbnd OH⋯OCH 3).

Wolniak, Micha?; Tomczyk, Micha?; Gudej, Jan; Wawer, Iwona



Staphylococcus aureus Peptidoglycan Stem Packing by Rotational-Echo Double Resonance NMR Spectroscopy  

PubMed Central

Staphylococcus aureus grown in the presence of an alanine-racemase inhibitor was labeled with D-[1-13C]alanine and L-[15N]alanine to characterize some details of the peptidoglycan tertiary structure. Rotational-echo double-resonance NMR of intact whole cells was used to measure internuclear distances between 13C and 15N of labeled amino acids incorporated in the peptidoglycan, and from those labels to 19F of a glycopeptide drug specifically bound to the peptidoglycan. The observed 13C-15N average distance of 4.1 to 4.4 Å between D- and L-alanines in nearest-neighbor peptide stems is consistent with a local, tightly packed, parallel-stem architecture for a repeating structural motif within the peptidoglycan of S. aureus. PMID:23617832

Kim, Sung Joon; Singh, Manmilan; Preobrazhenskaya, Maria; Schaefer, Jacob



13C NMR spectroscopy of the insoluble carbon of carbonaceous chondrites  

NASA Technical Reports Server (NTRS)

13C NMR spectra have been obtained of the insoluble carbon residues resulting from HF-digestion of three carbonaceous chondrites, Orgueil (C1), Murchison (CM2), and Allende (CV3). Spectra obtained using the cross polarization magic-angle spinning technique show two major features attributable respectively to carbon in aliphatic/olefinic structures. The spectrum obtained from the Allende sample was weak, presumably as a consequence of its low hydrogen content. Single pulse excitation spectra, which do not depend on 1H-13C polarization transfer for signal enhancement were also obtained. These spectra, which may be more representative of the total carbon in the meteorite samples, indicate a greater content of carbon in aromatic/olefinic structures. These results suggest that extensive polycyclic aromatic sheets are important structural features of the insoluble carbon of all three meteorites. The Orgueil and Murchison materials contain additional hydrogenated aromatic/olefinic and aliphatic groups.

Cronin, J. R.; Pizzarello, S.; Frye, J. S.



High-resolution NMR spectroscopy of biological tissues usingprojected Magic Angle Spinning  

SciTech Connect

High-resolution NMR spectra of materials subject toanisotropic broadening are usually obtained by rotating the sample aboutthe magic angle, which is 54.7 degrees to the static magnetic field. Inprojected Magic Angle Spinning (p-MAS), the sample is spun about twoangles, neither of which is the magic angle. This provides a method ofobtaining isotropic spectra while spinning at shallow angles. The p-MASexperiment may be used in situations where spinning the sample at themagic angle is not possible due to geometric or other constraints,allowing the choice of spinning angle to be determined by factors such asthe shape of the sample, rather than by the spin physics. The applicationof this technique to bovine tissue samples is demonstrated as a proof ofprinciple for future biological or medical applications.

Martin, Rachel W.; Jachmann, Rebecca C.; Sakellariou, Dimitris; Nielsen, Ulla Gro; Pines, Alexander



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



Allosteric modulation of myristate and Mn(III)heme binding to human serum albumin. Optical and NMR spectroscopy characterization.  


Human serum albumin (HSA) is best known for its extraordinary ligand binding capacity. HSA has a high affinity for heme and is responsible for the transport of medium and long chain fatty acids. Here, we report myristate binding to the N and B conformational states of Mn(III)heme-HSA (i.e. at pH 7.0 and 10.0, respectively) as investigated by optical absorbance and NMR spectroscopy. At pH 7.0, Mn(III)heme binds to HSA with lower affinity than Fe(III)heme, and displays a water molecule coordinated to the metal. Myristate binding to a secondary site FAx, allosterically coupled to the heme site, not only increases optical absorbance of Mn(III)heme-bound HSA by a factor of approximately three, but also increases the Mn(III)heme affinity for the fatty acid binding site FA1 by 10-500-fold. Cooperative binding appears to occur at FAx and accessory myristate binding sites. The conformational changes of the Mn(III)heme-HSA tertiary structure allosterically induced by myristate are associated with a noticeable change in both optical absorbance and NMR spectroscopic properties of Mn(III)heme-HSA, allowing the Mn(III)-coordinated water molecule to exchange with the solvent bulk. At pH = 10.0 both myristate affinity for FAx and allosteric modulation of FA1 are reduced, whereas cooperation of accessory sites and FAx is almost unaffected. Moreover, Mn(III)heme binds to HSA with higher affinity than at pH 7.0 even in the absence of myristate, and the metal-coordinated water molecule is displaced. As a whole, these results suggest that FA binding promotes conformational changes reminiscent of N to B state HSA transition, and appear of general significance for a deeper understanding of the allosteric modulation of ligand binding properties of HSA. PMID:16156788

Fanali, Gabriella; Fesce, Riccardo; Agrati, Cristina; Ascenzi, Paolo; Fasano, Mauro



Recombinant proteins incorporating short non-native extensions may display increased aggregation propensity as detected by high resolution NMR spectroscopy  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Bile acid binding proteins from different constructs retain structural integrity. Black-Right-Pointing-Pointer NMR {sup 15}N-T{sub 1} relaxation data of BABPs show differences if LVPR extension is present. Black-Right-Pointing-Pointer Deviations from a {sup 15}N-T{sub 1}/molecular-weight calibration curve indicate aggregation. -- Abstract: The use of a recombinant protein to investigate the function of the native molecule requires that the former be obtained with the same amino acid sequence as the template. However, in many cases few additional residues are artificially introduced for cloning or purification purposes, possibly resulting in altered physico-chemical properties that may escape routine characterization. For example, increased aggregation propensity without visible protein precipitation is hardly detected by most analytical techniques but its investigation may be of great importance for optimizing the yield of recombinant protein production in biotechnological and structural biology applications. In this work we show that bile acid binding proteins incorporating the common C-terminal LeuValProArg extension display different hydrodynamic properties from those of the corresponding molecules without such additional amino acids. The proteins were produced enriched in nitrogen-15 for analysis via heteronuclear NMR spectroscopy. Residue-specific spin relaxation rates were measured and related to rotational tumbling time and molecular size. While the native-like recombinant proteins show spin-relaxation rates in agreement with those expected for monomeric globular proteins of their mass, our data indicate the presence of larger adducts for samples of proteins with very short amino acid extensions. The used approach is proposed as a further screening method for the quality assessment of biotechnological protein products.

Zanzoni, Serena; D'Onofrio, Mariapina; Molinari, Henriette [Department of Biotechnology, University of Verona, 37134 Verona (Italy)] [Department of Biotechnology, University of Verona, 37134 Verona (Italy); Assfalg, Michael, E-mail: [Department of Biotechnology, University of Verona, 37134 Verona (Italy)] [Department of Biotechnology, University of Verona, 37134 Verona (Italy)



High-resolution molecular structure of a peptide in an amyloid fibril determined by magic angle spinning NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Amyloid fibrils are self-assembled filamentous structures associated with protein deposition conditions including Alzheimer's disease and the transmissible spongiform encephalopathies. Despite the immense medical importance of amyloid fibrils, no atomic-resolution structures are available for these materials, because the intact fibrils are insoluble and do not form diffraction-quality 3D crystals. Here we report the high-resolution structure of a peptide fragment of the amyloidogenic protein transthyretin, TTR(105-115), in its fibrillar form, determined by magic angle spinning NMR spectroscopy. The structure resolves not only the backbone fold but also the precise conformation of the side chains. Nearly complete 13C and 15N resonance assignments for TTR(105-115) formed the basis for the extraction of a set of distance and dihedral angle restraints. A total of 76 self-consistent experimental measurements, including 41 restraints on 19 backbone dihedral angles and 35 13C-15N distances between 3 and 6 Å were obtained from 2D and 3D NMR spectra recorded on three fibril samples uniformly 13C, 15N-labeled in consecutive stretches of four amino acids and used to calculate an ensemble of peptide structures. Our results indicate that TTR(105-115) adopts an extended -strand conformation in the amyloid fibrils such that both the main- and side-chain torsion angles are close to their optimal values. Moreover, the structure of this peptide in the fibrillar form has a degree of long-range order that is generally associated only with crystalline materials. These findings provide an explanation of the unusual stability and characteristic properties of this form of polypeptide assembly.

Jaroniec, Christopher P.; Macphee, Cait E.; Bajaj, Vikram S.; McMahon, Michael T.; Dobson, Christopher M.; Griffin, Robert G.



Determination of neo- and d-chiro-Inositol Hexakisphosphate in Soils by Solution 31P NMR Spectroscopy  

PubMed Central

The inositol phosphates are an abundant but poorly understood group of organic phosphorus compounds found widely in the environment. Four stereoisomers of inositol hexakisphosphate (IP6) occur, although for three of these (scyllo, neo, and d-chiro) the origins, dynamics, and biological function remain unknown, due in large part to analytical limitations in their measurement in environmental samples. We synthesized authentic neo- and d-chiro-IP6 and used them to identify signals from these compounds in three soils from the Falkland Islands. Both compounds resisted hypobromite oxidation and gave quantifiable 31P NMR signals at ? = 6.67 ppm (equatorial phosphate groups of the 4-equatorial/2-axial conformer of neo-IP6) and ? = 6.48 ppm (equatorial phosphate groups of the 2-equatorial/4-axial conformer of d-chiro-IP6) in soil extracts. Inositol hexakisphosphate accounted for 46–54% of the soil organic phosphorus, of which the four stereoisomers constituted, on average, 55.9% (myo), 32.8% (scyllo), 6.1% (neo), and 5.2% (d-chiro). Reappraisal of the literature based on the new signal assignments revealed that neo- and d-chiro-IP6 occur widely in both terrestrial and aquatic ecosystems. These results confirm that the inositol phosphates can constitute a considerable fraction of the organic phosphorus in soils and reveal the prevalence of neo- and d-chiro-IP6 in the environment. The hypobromite oxidation and solution 31P NMR spectroscopy procedure allows the simultaneous quantification of all four IP6 stereoisomers in environmental samples and provides a platform for research into the origins and ecological significance of these enigmatic compounds. PMID:22489788



Pulsed Field Gradient Selection in Two-Dimensional Magic Angle Spinning NMR Spectroscopy of Dipolar Solids  

NASA Astrophysics Data System (ADS)

The utility of gradient selection in MAS spectroscopy of dipolar solids is explored in two examples. In the first, rotor-synchronized gradients of appropriate strength and duration are applied to select 1H double-quantum coherences. The resulting DQ MAS spectrum of adamantane is compared with that acquired by the corresponding phase-cycling technique. As a second example, a 1H 2D exchange MAS experiment is performed on an elastomer sample. In this experiment, a gradient is applied to remove undesired coherences that would otherwise distort the spectrum for short mixing times. The diagonal-peak intensities in the resulting spectrum show a linear decrease with increasing mixing time indicating cross-relaxation by slow chain motions as the relevant process. Both types of experiments demonstrate the potential of gradient-selection techniques for MAS spectroscopy of dipolar solids.

Fritzhanns, Tilo; Hafner, Siegfried; Demco, Dan E.; Spiess, Hans W.; Laukien, Frank H.



Recoupling of chemical shift anisotropy by R-symmetry sequences in magic angle spinning NMR spectroscopy  

PubMed Central

13C and 15N chemical shift (CS) interaction is a sensitive probe of structure and dynamics in a wide variety of biological and inorganic systems, and in the recent years several magic angle spinning NMR approaches have emerged for residue-specific measurements of chemical shift anisotropy (CSA) tensors in uniformly and sparsely enriched proteins. All of the currently existing methods are applicable to slow and moderate magic angle spinning (MAS) regime, i.e., MAS frequencies below 20 kHz. With the advent of fast and ultrafast MAS probes capable of spinning frequencies of 40–100 kHz, and with the superior resolution and sensitivity attained at such high frequencies, development of CSA recoupling techniques working under such conditions is necessary. In this work, we present a family of R-symmetry based pulse sequences for recoupling of 13C/15N CSA interactions that work well in both natural abundance and isotopically enriched systems. We demonstrate that efficient recoupling of either first-rank (?1) or second-rank (?2) spatial components of CSA interaction is attained with appropriately chosen ?-encoded RNnv symmetry sequences. The advantage of these ?-encoded RNnv-symmetry based CSA (RNCSA) recoupling schemes is that they are suitable for CSA recoupling under a wide range of MAS frequencies, including fast MAS regime. Comprehensive analysis of the recoupling properties of these RNnv symmetry sequences reveals that the ?1-CSA recoupling symmetry sequences exhibit large scaling factors; however, the partial homonuclear dipolar Hamiltonian components are symmetry allowed, which makes this family of sequences suitable for CSA measurements in systems with weak homonuclear dipolar interactions. On the other hand, the ?-encoded symmetry sequences for ?2-CSA recoupling have smaller scaling factors but they efficiently suppress the homonuclear dipole-dipole interactions. Therefore, the latter family of sequences is applicable for measurements of CSA parameters in systems with strong homonuclear dipolar couplings, such as uniformly-13C labeled biological solids. We demonstrate RNCSA NMR experiments and numerical simulations establishing the utility of this approach to the measurements of 13C and 15N CSA parameters in model compounds, [15N]-N-acetyl-valine (NAV), [U-13C, 15N]-alanine, [U-13C,15N]-histidine, and present the application of this approach to [U-13C/15N]-Tyr labeled C-terminal domain of HIV-1 CA protein. PMID:23039592

Hou, Guangjin; Byeon, In-Ja L.; Ahn, Jinwoo; Gronenborn, Angela M.; Polenova, Tatyana



Double tuning a single input probe for heteronuclear NMR spectroscopy at low field  

PubMed Central

Applications of PASADENA in biomedicine are continuing to emerge due to recent demonstrations that hyperpolarized metabolic substrates and the corresponding reaction products persist sufficiently long to be detected in vivo. Biomedical applications of PASADENA typically differ from their basic science counterparts in that the polarization endowed by addition of parahydrogen is usually transferred from nascent protons to coupled storage nuclei for subsequent detection on a higher field imaging instrument. These pre-imaging preparations usually take place at low field, but commercial spectrometers capable of heteronuclear pulsed NMR at frequencies in the range of 100 kHz to 1 MHz are scarce though, in comparison to single channel consoles in that field regime. Reported here is a probe circuit that can be used in conjunction with a phase and amplitude modulation scheme we have developed called PANORAMIC (Precession And Nutation for Observing Rotations At Multiple Intervals about the Carrier), that expands a single channel console capability to double or generally multiple resonance with minimal hardware modifications. The demands of this application are geared towards uniform preparation, and since the hyperpolarized molecules are being detected externally at high field, detection sensitivity is secondary to applied field uniformity over a large reaction volume to accommodate heterogeneous chemistry of gas molecules at a liquid interface. The probe circuit was therefore configured with a large (40 mL) Helmholtz sample coil for uniformity, and double-tuned to the Larmor precession frequencies of 13C/1H (128/510 kHz) within a custom solenoidal electromagnet at a static field of 12 mT. Traditional (on-resonant) as well as PANORAMIC NMR signals with signal to noise ratios of approximately 75 have been routinely acquired with this probe and spectrometer setup from 1024 repetitions on the high frequency channel. The proton excitation pulse width was 240 ?s at 6.31 W, compared to a carbon-13 pulse width of 220 ?s at 2.51 W. When PANORAMIC refocusing waveforms were transmitted at a carrier frequency of 319 kHz, integrated signal intensities from a spin-echo sequence at both proton (510 kHz) and carbon-13 (128 kHz) frequencies were within experimental error to block pulse analogs transmitted on resonance. We anticipate that this probe circuit design could be extended to higher and lower frequencies, and that when used in conjunction with PANORAMIC phase and amplitude modulated arrays, will enable low field imaging consoles to serve as multinuclear consoles. PMID:22975236

Tadanki, Sasidhar; Colon, Raul D.; Moore, Jay; Waddell, Kevin W.



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

PubMed Central

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

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



Analysis of RF heating and sample stability in aligned static solid-state NMR spectroscopy.  


Sample instability during solid-state NMR experiments frequently arises due to RF heating in aligned samples of hydrated lipid bilayers. A new, simple approach for estimating sample temperature is used to show that, at 9.4 T, sample heating depends mostly on (1)H decoupling power rather than on (15)N irradiation in PISEMA experiments. Such heating for different sample preparations, including lipid composition, salt concentration and hydration level was assessed and the hydration level was found to be the primary parameter correlated with sample heating. The contribution to RF heating from the dielectric loss appears to be dominant under our experimental conditions. The heat generated by a single scan was approximately calculated from the Q values of the probe, to be a 1.7 degrees C elevation per single pulse sequence iteration under typical sample conditions. The steady-state sample temperature during PISEMA experiments can be estimated based on the method presented here, which correlates the loss factor with the temperature rise induced by the RF heating of the sample. PMID:16483809

Li, Conggang; Mo, Yiming; Hu, Jun; Chekmenev, Eduard; Tian, Changlin; Gao, Fei Philip; Fu, Riqiang; Gor'kov, Peter; Brey, William; Cross, Timothy A



Conformational Dynamics of Escherichia coli Flavodoxins in Apo- and Holo-States by Solution NMR Spectroscopy  

PubMed Central

Flavodoxins are a family of small FMN-binding proteins that commonly exist in prokaryotes. They utilize a non-covalently bound FMN molecule to act as the redox center during the electron transfer processes in various important biological pathways. Although extensive investigations were performed, detailed molecular mechanisms of cofactor binding and electron transfer remain elusive. Herein we report the solution NMR studies on Escherichia coli flavodoxins FldA and YqcA, belonging to the long-chain and short-chain flavodoxin subfamilies respectively. Our structural studies demonstrate that both proteins show the typical flavodoxin fold, with extensive conformational exchanges observed near the FMN binding pocket in their apo-forms. Cofactor binding significantly stabilizes both proteins as revealed by the extension of secondary structures in the holo-forms, and the overall rigidity shown by the backbone dynamics data. However, the 50 s loops of both proteins in the holo-form still show conformational exchanges on the µs-ms timescales, which appears to be a common feature in the flavodoxin family, and might play an important role in structural fine-tuning during the electron transfer reactions. PMID:25093851

Jin, Changwen



Solid-state NMR spectroscopy to probe photoactivation in canonical phytochromes.  


The photoreceptor phytochrome switches photochromically between two thermally stable states called Pr and Pfr. Here, we summarize recent solid-state magic-angle spinning (MAS) NMR work on this conversion process and interpret the functional mechanism in terms of a nano-machine. The process is initiated by a double-bond photoisomerization of the open-chain tetrapyrrole chromophore at the methine bridge connecting pyrrole rings C and D. The Pr-state chromophore and its surrounding pocket in canonical cyanobacterial and plant phytochromes has significantly less order, tends to form isoforms and is soft. Conversely, Pfr shows significantly harder chromophore-protein interactions, a well-defined protonic and charge distribution with a clear classical counterion for the positively charged tetrapyrrole system. The soft-to-hard/disorder-to-order transition involves the chromophore and its protein surroundings within a sphere of at least 5.5 Å. The relevance of this collective event for signaling is discussed. Measurement of the intermediates during the Pfr ? Pr back-reaction provides insight into the well-adjusted mechanics of a two-step transformation. As both Pr ? Pfr and Pfr ? Pr reaction pathways are different in ground and excited states, a photochemically controlled hyper-landscape is proposed allowing for ratchet-type reaction dynamics regulating signaling activity. PMID:23216105

Song, Chen; Rohmer, Thierry; Tiersch, Markus; Zaanen, Jan; Hughes, Jon; Matysik, Jörg



Assessment of ternary iron-cyclodextrin-2-naphthol complexes using NMR and fluorescence spectroscopies  

NASA Astrophysics Data System (ADS)

Recent research has indicated that ternary complexes can be formed among carboxymethyl-?-cyclodextrin, certain polycyclic aromatic hydrocarbons (PAHs) (e.g. anthracene and 2-naphthol), and Fe 2+ in aqueous solution. The formation of these ternary complexes has been suggested as the reason for improved reaction efficiency in iron catalyzed Fenton degradation (H 2O 2 + Fe 2+ ? rad OH + OH - + Fe 3+) of PAHs and other pollutants. In the present work, several other cyclodextrins were examined to determine their ability to form similar ternary complexes with 2-naphthol and Fe 2+. Fluorescence and NMR techniques were employed in this study. Results showed that hydroxypropyl-?-cyclodextrin, ?-cyclodextrin, and ?-cyclodextrin were able to encapsulate 2-naphthol molecules, but their binding with Fe 2+ was weak. On the contrary, sulfated-?-cyclodextrin has significant binding with Fe 2+, but it showed little inclusion of 2-naphthol molecules. Consequently, none of these four cyclodextrins formed significant amounts of ternary complexes in aqueous solution. The techniques used in this study provide useful methods for assessing the ability of cyclodextrins to form ternary complexes with guest compounds and metal ions.

Zheng, Weixi; Tarr, Matthew A.



Improved pulse sequences for pure exchange solid-state NMR spectroscopy.  


Spin-exchange experiments are useful for improving the resolution and establishment of sequential assignments in solid-state NMR spectra of uniformly (15)N-labeled proteins oriented macroscopically in phospholipid bilayers. To exploit this advantage fully, it is crucial that the diagonal peaks in the two-dimensional exchange spectra are suppressed. This may be accomplished using the recent pure-exchange (PUREX) experiments, which, however, suffer from up to a threefold reduction of the cross-peak intensity relative to experiments without diagonal-peak suppression. This loss in sensitivity may severely hamper the applicability for the study of membrane proteins. In this paper, we present a two-dimensional exchange experiment (iPUREX) which improves the PUREX sensitivity by 50%. The performance of iPUREX is demonstrated experimentally by proton-mediated (15)N-(15)N spin-exchange experiments for a (15)N-labeled N-acetyl-L-valyl-L-leucine dipeptide. The relevance of exchange experiments with diagonal-peak suppression for large, uniformly (15)N-labeled membrane proteins in oriented phospholipid bilayers is demonstrated numerically for the G-protein coupled receptor rhodopsin. PMID:14745809

Vosegaard, Thomas; Nielsen, Niels C



?-Bromo-2,6-dichlorotoluene: Molecular structure, vibrational spectroscopy, natural bond orbital analysis and NMR studies  

NASA Astrophysics Data System (ADS)

The FT-IR and FT-Raman spectra of ?-bromo-2,6-dichlorotoluene (?BDCT) have been recorded. The structural and spectroscopic data of the molecule in the ground state have been calculated using Hartree Fock (HF) and Density Functional Theory (DFT)/B3LYP with the standard 6-31++G(d,p) basis set. The optimized molecular geometry, vibrational frequencies and atomic charges in the ground state are calculated. With the help of specific scaling procedures, the observed vibrational wavenumbers in FT-IR and FT-Raman spectra have been analyzed and assigned to different normal modes of the molecule. A detailed interpretation of the infrared and Raman spectra of ?BDCT is also reported based on total energy distribution (TED). The 1H and 13C NMR chemical shifts have been calculated by gauge-including atomic orbital method with B3LYP/6-31++G(d,p) approach. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The theoretical results agree well with the observed spectra.

Karunakaran, V.; Balachandran, V.



Accurate determination of reference materials and natural isolates by means of quantitative (1)h NMR spectroscopy.  


A fast and precise proton nuclear magnetic resonance (qHNMR) method for the quantitative determination of low molecular weight target molecules in reference materials and natural isolates has been validated using ERETIC 2 (Electronic REference To access In vivo Concentrations) based on the PULCON (PULse length based CONcentration determination) methodology and compared to the gravimetric results. Using an Avance III NMR spectrometer (400 MHz) equipped with a broad band observe (BBO) probe, the qHNMR method was validated by determining its linearity, range, precision, and accuracy as well as robustness and limit of quantitation. The linearity of the method was assessed by measuring samples of l-tyrosine, caffeine, or benzoic acid in a concentration range between 0.3 and 16.5 mmol/L (r(2) ? 0.99), whereas the interday and intraday precisions were found to be ?2%. The recovery of a range of reference compounds was ?98.5%, thus demonstrating the qHNMR method as a precise tool for the rapid quantitation (~15 min) of food-related target compounds in reference materials and natural isolates such as nucleotides, polyphenols, or cyclic peptides. PMID:24559241

Frank, Oliver; Kreissl, Johanna Karoline; Daschner, Andreas; Hofmann, Thomas



High-Resolution 1H NMR Spectroscopy of Fish Muscle, Eggs and Small Whole Fish via Hadamard-Encoded Intermolecular Multiple-Quantum Coherence  

PubMed Central

Background and Purpose Nuclear magnetic resonance (NMR) spectroscopy has become an important technique for tissue studies. Since tissues are in semisolid-state, their high-resolution (HR) spectra cannot be obtained by conventional NMR spectroscopy. Because of this restriction, extraction and high-resolution magic angle spinning (HR MAS) are widely applied for HR NMR spectra of tissues. However, both of the methods are subject to limitations. In this study, the feasibility of HR 1H NMR spectroscopy based on intermolecular multiple-quantum coherence (iMQC) technique is explored using fish muscle, fish eggs, and a whole fish as examples. Materials and Methods Intact salmon muscle tissues, intact eggs from shishamo smelt and a whole fish (Siamese algae eater) are studied by using conventional 1D one-pulse sequence, Hadamard-encoded iMQC sequence, and HR MAS. Results When we use the conventional 1D one-pulse sequence, hardly any useful spectral information can be obtained due to the severe field inhomogeneity. By contrast, HR NMR spectra can be obtained in a short period of time by using the Hadamard-encoded iMQC method without shimming. Most signals from fatty acids and small metabolites can be observed. Compared to HR MAS, the iMQC method is non-invasive, but the resolution and the sensitivity of resulting spectra are not as high as those of HR MAS spectra. Conclusion Due to the immunity to field inhomogeneity, the iMQC technique can be a proper supplement to HR MAS, and it provides an alternative for the investigation in cases with field distortions and with samples unsuitable for spinning. The acquisition time of the proposed method is greatly reduced by introduction of the Hadamard-encoded technique, in comparison with that of conventional iMQC method. PMID:24466083

Cai, Honghao; Chen, Yushan; Cui, Xiaohong; Cai, Shuhui; Chen, Zhong



Continuously Tunable 250 GHz Gyrotron with a Double Disk Window for DNP-NMR Spectroscopy  

PubMed Central

In this paper, we describe the design and experimental results from the rebuild of a 250 GHz gyrotron used for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance spectroscopy on a 380 MHz spectrometer. Tuning bandwidth of approximately 2 GHz is easily achieved at a fixed magnetic field of 9.24 T and a beam current of 95 mA producing an average output power of >10 W over the entire tuning band. This tube incorporates a double disk output sapphire window in order to maximize the transmission at 250.58 GHz. DNP Signal enhancement of >125 is achieved on a 13C-Urea sample using this gyrotron. PMID:23539422

Jawla, Sudheer; Ni, Qing Zhe; Barnes, Alexander; Guss, William; Daviso, Eugenio; Herzfeld, Judith; Griffin, Robert; Temkin, Richard



Looking at microbial metabolism by high-resolution 2H-NMR spectroscopy  

PubMed Central

We analyzed the applicability of high-resolution 2H-HMR spectroscopy for the analysis of microbe metabolism in samples of mitochondrion isolated from rat liver and from aqueous extracts of homogenates of rat liver and other organs and tissues in the presence of high D2O contents. Such analysis is possible due to the fast microbe adaptation to life in the heavy water. It is also shown that some enzymatic processes typical for the intact cells are preserved in the homogenized tissue preparations. The microbial and cellular metabolic processes can be differentiated via the strategic use of cell poisons and antibiotics. PMID:23862103

Beskaravayny, Petr M.; Molchanov, Maxim V.; Paskevich, Svetlana I.; Prokhorov, Dmitry A.



Quantitative analysis of iobitridol in an injectable preparation by 1H NMR spectroscopy.  


Nuclear magnetic resonance spectroscopy was used for direct quantitative determination of iobitridol in an injectable formulation. The method was developed on a medium field strength magnet (400MHz) and validation was performed by assessing specificity, accuracy, precision, linearity, stability of samples and robustness. Validation data confirm that the method is highly appropriate for direct quantification of iobitridol in the final formulation. Moreover the method has a good potential for rapid screening analyses due to straightforward experimental setup and lack of any sample pretreatment. PMID:24531005

Borioni, Anna; Gostoli, Gianluca; Bossù, Elena; Sestili, Isabella



Pb-207 NMR Spectroscopy Reveals that Pb(II) Coordinates with Glutathione (GSH) and Tris Cysteine Zinc Finger Proteins in a PbS3 Coordination Environment  

PubMed Central

207Pb NMR spectroscopy can be used to monitor the binding of Pb(II) to thiol rich biological small molecules such as glutathione and to zinc finger proteins. The UV/visible (UV/Vis) absorption band centered at 334 nM and the observed 207Pb-signal in 207Pb NMR (? ~ 5750 ppm) indicate that glutathione binds Pb(II) in a trigonal pyramidal geometry (PbS3) at pH 7.5 or higher with a 1:3 molar ratio of Pb(II) to GSH. While previous studies using UV/Vis and extended X-ray absorption fine structure (EXAFS) spectroscopy were interpreted to show that the zinc binding domain from HIV nucleocapsid protein (HIV-CCHC) binds Pb(II) in a single PbS3 environment, the more sensitive 207Pb NMR spectra (at pH 7.0, 1:1 molar ratio) provide compelling evidence for the presence of two PbS3 structures (? = 5790 and 5744 ppm), one of which is more stable at high temperatures. It has previously been proposed that the HIV-CCHH peptide does not fold properly to afford a PbS2N motif, because histidine does not bind to Pb(II). These predictions are confirmed by the present studies. These results demonstrate the applicability of 207Pb NMR to biomolecular structure determination in proteins with cysteine binding sites for the first time. PMID:21625408

Neupane, Kosh P.; Pecoraro, Vincent L.



Exploring the molecular structure of imidazolium-silica-based nanoparticle networks by combining solid-state NMR spectroscopy and first-principles calculations.  


A DFT-based molecular model for imidazolium-silica-based nanoparticle networks (INNs) is presented. The INNs were synthesized and characterized by using small-angle X-ray scattering (SAXS), NMR spectroscopy, and theoretical ab initio calculations. (11) B and (31) P HETCOR CP MAS experiments were recorded. Calculated (19) F?NMR spectroscopy results, combined with the calculated anion-imidazolium (IM) distances, predicted the IM chain density in the INN, which was also confirmed from thermogravimetric analysis/mass spectrometry results. The presence of water molecules trapped between the nanoparticles is also suggested. First considerations on possible ?-? stacking between the IM rings are presented. The predicted electronic properties confirm the photoluminescence emissions in the correct spectral domain. PMID:25241702

Neouze, Marie-Alexandra; Kronstein, Martin; Litschauer, Marco; Puchberger, Michael; Coelho, Cristina; Bonhomme, Christian; Gervais, Christel; Tielens, Frederik



In Vivo Neurochemical Profiling of Rat Brain by 1H-[13C] NMR Spectroscopy. Cerebral Energetics and Glutamatergic/GABAergic Neurotransmission  

PubMed Central

The simultaneous quantification of excitatory and inhibitory neurotransmission and the associated energy metabolism is crucial for a proper understanding of brain function. While the detection of glutamatergic neurotransmission in vivo by 13C NMR spectroscopy is now relatively routine, the detection of GABAergic neurotransmission in vivo has remained elusive due to the low GABA concentration and spectral overlap. Using 1H-[13C] NMR spectroscopy at