An Improved Diffusion-Ordered Spectroscopy Experiment Incorporating Bipolar-Gradient Pulses

Wu, Donghui; Chen, A.D.; Johnson, Charles S.

doi:10.1006/jmra.1995.1176

Cited by 1,411 publications

(1,086 citation statements)

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“…The diffusion experiments were performed by using a stimulated-echo sequence incorporating bipolar gradient pulses and a longitudinal eddy current delay (27). The gradient strength was incremented in 16 steps from 2% to 95% of the maximum gradient strength in a customarily programmed scheme, which was optimized to achieve a 95% decrease in the resonance intensity at the largest gradient amplitudes for all of the mixture components.…”

Section: Methodsmentioning

confidence: 99%

Enhanced diffusion-edited NMR spectroscopy of mixtures using chromatographic stationary phases

Viel

Ziarelli

Caldarelli

2003

Proc. Natl. Acad. Sci. U.S.A.

104

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We introduce an analytical method that combines in one pot the advantages of column chromatography separation and NMR structural analysis. The separation of the NMR spectra of the components of a mixture can be achieved according to their apparent diffusion rates [James, T. L. and McDonald, G. G. (1973) J. Magn. Reson. 58, 58 -61]. We show that the separation of the spectral components, corresponding to single molecular species, can be enhanced by order of magnitudes upon addition of a typical stationary phase used in HPLC. The solid phase imbibed by the mixture for analysis is an heterogeneous ensemble, so that solidstate NMR methods (high-resolution magic angle spinning) are necessary to recover high-resolution spectra. We demonstrate applications of this combination of high-resolution magic angle spinning and NMR diffusometry on test mixtures for direct (silica gel) and inverse (C18) columns. However, many common chromatographic supports available for HPLC should be readily adaptable for use with this technique.T he challenge in the analysis of complex mixtures is 2-fold: to achieve an effective separation of the components and provide a proper structural characterization for each of them. The common solution is hyphenation, which is a sequential combination of chromatography and spectroscopic analysis such as mass or UV spectrometry. Because NMR is often the tool of choice for precise structural characterizations of organic molecules, an effort has been done to introduce NMR as a detector in hyphenated techniques (1). An alternative solution for the NMR characterization of mixture components exploits the behavior of the NMR signal of a molecule diffusing in an inhomogeneous magnetic field. In this case, the frequency of the observed target becomes time dependent, with consequent broadening of the resonance line (2). The apparent diffusion rate associated to a molecular resonance can be estimated by performing a series of experiments varying the amplitude of the inhomogeneous field and inverting the corresponding decay curve of the signal amplitude. Diffusion-ordered spectroscopy (DOSY) (3) is a particularly convenient means of displaying this information, organized in a bidimensional array with the NMR spectrum on one dimension and the apparent diffusion rate on the other one. As a collateral aspect, the DOSY display decomposes the overall NMR spectrum of a mixture into those of its components if these latter possess different molecular mobility, without previous collection of separate fractions (4-7). In optimal conditions, the diffusion experiment is capable of resolving contributions from molecules whose diffusion coefficients differ only by a few percent (8). In cases of serious signal overlapping, other methods for processing diffusion data achieve better spectral separation (9-11). We present here an analytical procedure that capitalizes on this idea, but in which the separation properties of the NMR method are enhanced by addition of a solid phase, a typical stationary phase material used for chromato...

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Section: Methodsmentioning

confidence: 99%

Enhanced diffusion-edited NMR spectroscopy of mixtures using chromatographic stationary phases

Viel

Ziarelli

Caldarelli

2003

Proc. Natl. Acad. Sci. U.S.A.

104

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“…After linear forward prediction to 512 data points in the f 2 dimension and sinusoidal multiplication in both dimensions, they were Fourier transformed to twodimensional spectra with a 6,000 Hz range in both dimensions. The diffusion behavior of the monosaccharide was derived from the signal attenuation in a series of stimulated echo spectra with increasing gradient amplitudes by fixed diffusion delay (35,36). All measurements were performed at 298.1 K. Chemical shifts were referenced to external acetone (␦ H 2.225 ppm).…”

Section: Lc-esi-ms/ms-borohydride-reduced O-glycansmentioning

confidence: 99%

Characterization and Scope of S-layer Protein O-Glycosylation in Tannerella forsythia

Posch

Pabst

Brecker

et al. 2011

Journal of Biological Chemistry

188

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“…Diffusionedited (DE) experiments were performed using a bipolar pulse longitudinal encode-decode sequence. [19] Scans (1024) were collected using a 2.5-ms, 49-gauss cm À1 , sine-shaped gradient pulse, a diffusion time of 100 ms, 8192 time domain points and 410 ms acquisition time. Spectra were apodised through multiplication with an exponential decay corresponding to 10 Hz line broadening and zero-filling factor of 2.…”

Section: Nmr Spectroscopic Analysismentioning

confidence: 99%

“…In diffusion edited NMR experiments, small molecules are essentially gated from the final spectrum but signals from macromolecules that display little translational diffusion are not gated and appear in the spectrum. [19,25] The diffusion edited spectrum of Ballina DOM is shown in Fig. 2b.…”

Section: General Characterisationmentioning

confidence: 99%

Composition of dissolved organic matter within a lacustrine environment

McCaul¹,

Sutton²,

Simpson³

et al. 2011

Environ. Chem.

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Environmental context. Freshwater dissolved organic matter is a complex chemical mixture central to many environmental processes, including carbon and nitrogen cycling. Questions remain, however, as to its chemical characteristics, sources and transformation mechanisms. We studied the nature of dissolved organic matter in a lake system and found that it is influenced by anthropogenic activities. Human activities can therefore influence the huge amounts of carbon sequestered in lakes as dissolved organic matter.Abstract. Freshwater dissolved organic matter (DOM) is a complex mixture of chemical components that are central to many environmental processes, including carbon and nitrogen cycling. However, questions remain as to its chemical characteristics, sources and transformation mechanisms. Here, we employ 1-and 2-D nuclear magnetic resonance (NMR) spectroscopy to investigate the structural components of lacustrine DOM from Ireland, and how it varies within a lake system, as well as to assess potential sources. Major components found, such as carboxyl-rich alicyclic molecules (CRAM) are consistent with those recently identified in marine and freshwater DOM. Lignin-type markers and protein/peptides were identified and vary spatially. Phenylalanine was detected in lake areas influenced by agriculture, whereas it is not detectable where zebra mussels are prominent. The presence of peptidoglycan, lipoproteins, large polymeric carbohydrates and proteinaceous material supports the substantial contribution of material derived from microorganisms. Evidence is provided that peptidoglycan and silicate species may in part originate from soil microbes.

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An Improved Diffusion-Ordered Spectroscopy Experiment Incorporating Bipolar-Gradient Pulses

Cited by 1,411 publications

References 0 publications

Enhanced diffusion-edited NMR spectroscopy of mixtures using chromatographic stationary phases

Enhanced diffusion-edited NMR spectroscopy of mixtures using chromatographic stationary phases

Characterization and Scope of S-layer Protein O-Glycosylation in Tannerella forsythia

Composition of dissolved organic matter within a lacustrine environment

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