High-resolution Nuclear Magnetic Resonance Spectra Research Articles

Use of deuterium labeling in NMR: overcoming a sizeable problem

In summary, the use of deuteration in combination with uniformly 13C- and 15N-labeling dramatically improves the quality of NMR spectra of larger proteins. These improvements allow the backbone and side-chain signals of larger proteins to be assigned and aids in the acquisition and analysis of NOE data. Using these methods, three-dimensional structures of proteins up to 30kDa have been determined [[[20]xStructure and ligand recognition of the phosphotyrosine binding domain of Shc. Zhou, M.-M...., and Fesik, S.W. Nature. 1995; 378: 584–592Crossref | PubMedSee all References, [31]xX-ray and NMR structure of human Bcl-xL, an inhibitor of programmed cell death. Muchmore, S.W...., and Fesik, S.W. Nature. 1996; 381: 335–341Crossref | PubMedSee all References, [32]xStructure of Bcl-xL–Bak peptide complex reveals how regulators of apoptosis interact. Sattler, M...., and Fesik, S.W. Science. 1996; : in pressSee all References] SWF, unpublished data]. Further developments of NMR methods and variation of labeling techniques promise to push the molecular weight limit even further.

High-Resolution NMR Spectra of Nuclear Spin Systems under Homogeneous Interactions in Solids Exhibiting Line Narrowing Induced by the Memory Effect

High-resolution nuclear magnetic resonance spectra of nuclear spin systems under strong homogeneous interactions in solids can be obtained simply by single-pulse excitation with a sufficiently long delay before data acquisition. The spectra are quantitative but subject to phase distortions. By inserting a refocusing pulse between excitation and acquisition, the sensitivity can be improved. The spectrum has the highest resolution when the sample is rotated at the magic angle, but the linewidth of the off-MAS spectrum does not show aP2(cos β) dependence. This method can be satisfactorily explained by means of memory-function theory, and many experimental results for static, magic-angle spinning, and off-magic angle spinning samples are presented.

Rapid identification of common human pathogens by high-resolution proton magnetic resonance spectroscopy.

Routine procedures for recovery of bacteria from clinical specimens involve culturing the latter on various nonselective and selective agar media. The bacteria are then identified by means of biochemical and immunological test procedures. Reduction of the time required to identify the bacteria is highly desirable for rapid clinical diagnosis. Towards this end the potential of proton nuclear magnetic resonance (NMR) spectroscopy for providing a "fingerprint" within the proton spectrum of five bacterial genera, reflecting their characteristic cell wall constituents, has been investigated. Establishing a database of high-resolution proton NMR spectra of a large number of bacterial species is a prerequisite for attaining this objective. A database has been established for five common human pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis. On the basis of the presence of characteristic resonances in their spectra, a simple algorithm has been developed to differentiate and identify these microorganisms. The NMR spectra of E. coli and S. aureus showed no dependency on the type of growth medium, growth density, or incubation time.

High-resolution 1H NMR spectroscopy of aqueous humour from rabbits.

Detection of different substances in aqueous humour is important for evaluation of the disorders affecting the eye. The purpose of the present study was to apply high-resolution proton (1H) nuclear magnetic resonance (NMR) spectroscopy for extensive characterisation of the metabolites in the aqueous humour from rabbits. High-resolution 1H NMR spectroscopy, including two-dimensional shift correlated (COSY) technique, was performed on aqueous humour from rabbits. More than 20 metabolites were simultaneously detected and identified in high-resolution 1H NMR spectra of aqueous humour from rabbits. Some of these were also quantified. High-resolution 1H NMR spectroscopy is a valuable method for simultaneous detection of many different metabolites in aqueous humour.

Triple-quantum NMR by selective triple resonance

In high-resolution nuclear magnetic resonance spectra of scalar coupled spins in isotropic phase, it is possible to convert single-into triple-quantum coherences and vice versa by irradiating simultaneously at the frequencies of three chemical shifts. A triple resonance condition can be achieved by modulating a radio-frequency carrier by a product of two cosinusoidal audiowaves, chosen so that three of the four sidebands coincide with three selected chemical shifts. When used in conjunction with two-dimensional Fourier transform spectroscopy, it is possible to obtain triple-quantum multiplets with very high resolution within a limited time span. The linewidths can give an accurate measure of the relaxation rates of triple-quantum coherences.

High-Resolution 1H NMR Study of Membrane Phospholipids in Rat Pancreas Stimulated by Caerulein

In this study, the peak observed at 3.2 +/- 0.2 ppm in the 1H nuclear magnetic resonance (NMR) spectra recorded at 60 MHz of rat pancreas stimulated by caerulein was characterized at higher resolution (100 and 300 MHz). Whole pancreas from rats stimulated by caerulein was analyzed ex vivo by 1H NMR spectroscopy at 100 MHz. After suppression of the tissue water peak (OSIRIS method), a peak at 3.2 +/- 0.2 ppm appeared distinctly, along with two other weaker signals (2.8 and 3.5 ppm). No signals were observed in these regions in the spectra recorded from pancreas of 48-h fasted rats. The signal at 3.2 +/- 0.2 ppm was characterized by analysis of the high-resolution 1H NMR (300 MHz) spectra of lipid extracts of rat pancreas. Addition of various pure membrane phospholipids in extracts showed that the peak was due to the N(CH3)3 groups of choline-containing lipids. The weaker signals (2.8 and 3.5 ppm) were attributed to the methylene protons of fatty acids and the glycerol of glycerophosphorylcholine (GPC). A small decrease in phosphatidylcholine (PC) concentration was observed on analysis of these lipid extracts by high-performance liquid chromatography, indicating that the increase in intensity of the 3.2 +/- 0.2 ppm peak was not due to any increase in PC concentration, but rather to a change in conformation of PC, allowing higher mobility of the trimethylamino protons. Lorglumide, a specific inhibitor of caerulein, markedly reduced the intensity of the NMR peak, and pentagastrin, which also stimulates exocytosis of zymogen granules in the pancreas, had a similar but somewhat smaller effect than caerulein.(ABSTRACT TRUNCATED AT 250 WORDS)

The orientation of molecules with internal rotation in nematic phases

The anisotropic couplings obtained from the 1H nuclear magnetic resonance (NMR) spectra of partially oriented molecules with internal rotation are difficult to analyse because the order parameters for each conformer cannot be deduced without assumptions. The purpose of this paper is to show how a model for the anisotropic short-range potential can be useful in the interpretation of the high-resolution 1H NMR spectra of the flexible molecules furfural, 2-chlorobenzaldehyde, and 2,2′-dithiophene dissolved in a 55% Merck ZLI 1132-45% N-(p-ethoxybenzylidene)-2,6-dideutero-p'-n-butylaniline (w/w) mixture. In this nematic mixture there is no contribution to the anisotropic potential from the interaction between the solute molecular quadrupole moment and the average electric field gradient of the liquid crystal solvent; the dominant anisotropic intermolecular potential in this mixture is taken to result solely from short-range interactions. We find good agreement between experiment and the order parameters calcu...

Proton magnetic resonance spectroscopy of polymorphonuclear leukocytes from patients with serious bacterial infections.

Triacylglycerols in human neutrophils exposed to proinflammatory stimuli generate a high-resolution proton magnetic resonance (1H MR) spectrum. Lipid cross-peak F volumes in neutrophils from patients with inflammatory conditions were measured. Values in patients hospitalized with localized infections (14.4 +/- 9.0; mean +/- SD) or bacteremia (19.3 +/- 9.7) were significantly higher than in patients with noninflammatory conditions (6.2 +/- 5.3) and healthy controls (2.0 +/- 3.0; P < .001). The positive predictive value of F volumes > 10 was 93% for all infection; the negative predictive value of volumes < or = 10 was 68% for all infection and 92% for bacteremia. Plasma lipopolysaccharide (LPS) concentrations were highest in bacteremic patients but did not correlate with levels of tumor necrosis factor-alpha (TNF alpha) or interleukin-6. In vitro, LPS increased F volumes of control neutrophils from 2.0 +/- 3.0 to 37.2 +/- 6.7 (P < .001); TNF alpha had no effect. F volumes in 1H MR spectra may be useful clinically to discriminate between serious bacterial infection and other inflammatory conditions. TNF alpha is not the stimulus for generation of lipid spectra in vivo.

Diamagnetic behaviour of high-resolution nitrogen-14 nuclear magnetic resonance spectra for co-ordinated nitrogens in paramagnetic chromium(III) diamine complexes

Diamagnetic behaviour in the chemical shift and linewidth of high-resolution nitrogen-14 NMR spectra for paramagnetic chromium(III) diamine complexes was investigated in comparison with that for the corresponding diamine dihydrochlorides and the diamagnetic cobalt(III) complexes. The NMR signals can be assigned to each inequivalent nitrogen ligating atom of unsymmetic diamines in the chromium(III) complexes. The 14N NMR spectra are affected by the diamine chelate ring conformations of the tris(diamine) complexes, but hardly sensitive to the ligand replacement in trans- and cis-[CrX2(diamine)2] type complexes.

Sodium and Chloride Sorption by Imogolite and Allophanes

AbstractThe surface excesses of Na and Cl on synthetic imogolite and allophanes with varying Al/Si molar ratios in 0.10 M and 0.01 M NaCl solutions were determined using 22Na and 36Cl as ion probes. The point of zero net charge (PZNC) values ranged from 4.1 to 8.4, increasing with the Al/Si molar ratio for the allophanes, and was highest for imogolite (Al/Si = 2.01). The PZNC values were significantly lower than the point of zero charge (PZC) values previously determined by microelectrophoresis for the same material, indicating that Na resided within the shear plane to a greater extent than Cl. The PZNC values of allophanes were lower than their PZSE values, indicating that permanent charge existed in allophanes, and increased as Al/Si decreased. Conversely, the PZNC of imogolite was higher than its point of zero salt effect (PZSE) determined by potentiometric titration. Adsorption of Cl on imogolite from 0.1 and 0.01 M NaCl solutions below pH 8.4 and of Na from 0.1 M NaCl solutions between pH 5 and 8.4 exceeded the proton charge determined by potentiometric titration. There was no direct evidence of permanent charge in imogolite and excess Cl adsorption could not be entirely explained by simultaneous intercalation of Na and Cl. Isomorphic substitution of Al in tetrahedral sites was shown to increase with decreasing Al/Si by 27Al high-resolution solid-state nuclear magnetic resonance (NMR) spectra of allophanes, and was absent in imogolite. The chemical shifts of Al(4) and Al(6) were similar in allophanes (63.0–64.7 ppm and 6.1–7.8 ppm, respectively) and the chemical shift of Al(6) was 9.4 in imogolite.

Investigation of interaction of polyester-polyurethanes and their zwitterionomers by solid-state nuclear magnetic resonance

High-resolution 1H and 13C nuclear magnetic resonance spectra are used to investigate the intermolecular interaction of polyester-polyurethanes with different contents of hard segments and different degrees of ionization. Because there are several kinds of hydrogen bonds, the hydrogen bonds play an important role in phase separation and physical properties. The higher the percentage of intermolecular hydrogen bonds, the greater are the tensile strength and strength at definite elongation. The interaction between 4,4′-methylene diphenyl diisocyanate and N-methyldiethanolamine is weak for the ES-33.4 series. Ionization does not change the percentage of intermolecular hydrogen bonds for the ES-33.4 series and ES-41 series, and ionization does not improve the physical properties and phase separation.

Properties of the spectrin‐like structural element of smooth‐muscle α‐actinin

The fragment of smooth muscle alpha-actinin, comprising the four spectrin-like structural repeating units, has a high alpha-helix content, similar to that of spectrin, and a hydrodynamic frictional coefficient, indicative of an elongated, probably bent or kinked rod-like structure, as found for spectrin dimer and tetramer. The fragment exists in solution as an extremely stable dimer, which is dissociated only under denaturing conditions and is much more resistant to dissociation by urea than is the spectrin heterodimer. High-resolution proton magnetic resonance spectra reveal that a part of the polypeptide chain gives rise to sharp resonances; this is also true of spectrin and it implies that the individual structural repeating units contain segmentally mobile elements, which may be required to generate the elastic properties of the spectrin family of proteins. Again like spectrin, the alpha-actinin fragment contains multiple binding sites for long-chain fatty acids, as revealed by quenching of tryptophan fluorescence by 2-bromostearate (though not by 9(10)-bromostearate). The results point to extensive structural and functional similarities between the repeating units of all the proteins of the spectrin family.

Following the spatial distribution of a solid dissolving at an interface by high-resolution nuclear magnetic resonance spectroscopy

The effects of the inherent magnetic susceptibility discontinuities found in heterogeneous systems on conventional high-resolution nuclear magnetic resonance spectra have been used to differentiate space near a phase boundary. The system studied is that of a solid dissolving at and diffusing from a liquid/liquid boundary. The concentration of the solute has been measured as a function of time and distance from the interface and the results obtained compared with those from a simple mathematical model of the system. As this technique makes use of the heterogeneities within a system, it has obvious applications where the effects of such heterogeneities make normal NMR analysis (either spectroscopy or imaging) very difficult.

High-resolution 27AI NMR spectroscopy of the aluminophosphate molecular sieve VPI-5

ALUMINIUM plays an important part in determining the properties of many materials, such as the catalytic behaviour of zeolites. Aluminophosphate molecular sieves, in particular, have useful applications as superlattice hosts in the fabrication of quantum-effect devices1. Although nuclear magnetic resonance (NMR) spectroscopy is often a sensitive probe of solids, the use of 27Al NMR to investigate the structure of aluminosilicates and alumino-phosphates has been severely limited because anisotropic second-order quadrupolar interactions, responsible for spectral broadening, cannot be eliminated by conventional magic-angle-spinning or multiple-pulse techniques. Here we report the first high-resolution NMR spectra of 27A1 in a solid using double rotation2–4 and demonstrate its usefulness for probing subtle structural perturbations in the aluminophosphate molecular sieve VPI-55,6. From our results, we conclude that high-resolution 27A1 NMR is capable of resolving discrete framework aluminium sites, permitting quantitative investigation of site-specific adsorbate interactions with the VPI-5 host.

Proton NMR Observation of Phenylalanine and an Aromatic Metabolite in the Rabbit Brain in Vivo

1H nuclear magnetic resonance (NMR) was used to detect directly the signal from the aromatic protons of phenylalanine (phe) in the brains of rabbits made hyperphenylalaninemic by administration of a diet high in phe and containing 0.4% alpha-methylphenylalanine. In addition to those resonances found in the region between 6.5 and 8.5 ppm in the 1H NMR spectra of control rabbits, a resonance centered at 7.37 ppm was observed in the spectra obtained from the brains of hyperphenylalaninemic rabbits in vivo or in situ postmortem. The chemical shift of this additional resonance was that expected for protons of the phenyl ring of phe. Its intensity correlated well with measurements of brain phe levels made on postmortem samples by amino acid analyzer. Both of these measurements correlated poorly with amino acid analyzer measurements of serum phe, especially at high values of the latter. High-resolution 1H NMR spectra of the brain extracts showed that in most animals an unidentified aromatic compound, possibly gamma-glutamyl-phe, was present in addition to phe. This study demonstrates the feasibility of measuring the concentration of brain phenyl and its metabolites noninvasively by 1H NMR. The method can be used for similar measurements in human brain.

High-resolution carbon-13 nuclear magnetic resonance spectra and structure of amorphous and crystalline forms of stereoregular poly(methyl methacrylate)s

High-resolution carbon-13 nuclear magnetic resonance spectra and structure of amorphous and crystalline forms of stereoregular poly(methyl methacrylate)s

17O NMR in simple oxides

The following binary metal oxides have yielded high-resolution 17O nuclear magnetic resonance (NMR) spectra, obtained by magic-angle spinning (MAS) without isotopic enrichment: α-Al 2O 3, TiO 2 (anatase and rutile), Ti 2O 3, monoclinic VO 2, Cu 2O, ZnO, tetragonal and monoclinic ZrO 2, Ag 2O, tetragonal SnO, hexagonal La 2O 3, CeO 2, HfO 2, α-PbO; also Na β-Al 2O 3 and cubic MgO-ZrO 2. Detection sensitivity limits observation to cases where the nuclear quadrupole coupling is less than 4 MHz. Different ceramic phases can readily be distinguished by their chemical shift. As empirical chemical shift correlation is suggested between 17O in the oxide M 2O m , and 19F in the corresponding fluoride MF m .

High-resolution solid-state nuclear magnetic resonance spectra of dentin collagen

Insoluble collagen of bovine dentin was characterized by high-resolution solid-state 13C nuclear magnetic resonance (NMR) spectroscopy using a cross-polarization magic angle spinning procedure. A downfield shift was observed in the signal of hydroxyproline Cβ compared with that in skin collagen, indicating a distortion in the hydroxyproline structure. A signal of 31P NMR was detected in dentin collagen that was compatible with the presence of matrix-associated phosphoprotein.

High-temperature NMR using inductive heating

We report a simple, efficient method for carrying out nuclear magnetic resonance (NMR) experiments at high temperature in any NMR probe without modification. The sample tube is coated with a thin film of metal and the rf coil used for the NMR experiment is used to inductively heat the film, thus heating the sample inside the tube. Using this approach, we have obtained both proton and high-resolution carbon-13 NMR spectra at temperatures as high as 730 K.

Quantitation of the relative amounts of anhydrous carbamazepine (C15H12N2O) and carbamazepine dihydrate (C15H12N2O.2H2O) in a mixture by solid-state nuclear magnetic resonance (NMR).

The application of solid state nuclear magnetic resonance (NMR) for the quantitation of the relative amounts of carbamazepine anhydrate (I) and carbamazepine dihydrate (II) in a mixture is presented. The techniques of cross polarization, dipolar decoupling, and magic angle spinning have been used to obtain high-resolution NMR spectra of the samples in the solid state. Although the chemical shifts of I and II were similar, the proton spin lattice relaxation time of II was much shorter than that of I. A delay time of 10 sec between pulses resulted in saturation of the signal from I and in a spectrum arising solely from II. The dependence of the observed signal intensity on the contact time was evaluated for II and glycine, the internal standard, to allow theoretical estimation of the peak area ratios. Various molar ratios of I and II were then mixed with glycine, and the resulting peak area ratios of II to the area of the alpha and the carbonyl carbons of glycine was linearly related to the relative proportion of II in the mixture.