RDC as a New NMR-Parameter for Peptides

Kessler, Horst; Luy, Burkhard; Kobzar, Kyryl; Freudenberger, J.; Knör, Sebastian; Heckmann, Dominik; Klages, Jochen

doi:10.1007/978-0-387-26575-9_330

Cited by 2 publications

(3 citation statements)

References 10 publications

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“…It turns out that achievable performances are generally better than for corresponding hard pulses with the inherent advantage that no phase correction has to be applied with the RADFA pulses. As the optimized pulses belong to the class of so‐called point‐to‐point pulses, starting with I z polarization, pulses are mainly designed for use as excitation pulses with variable effective flip angle, as, for example, routinely used in 13 C‐1D experiments. In such cases, the duration of corresponding pulse shapes is usually not critical, and longest, best performing pulses should be used.…”

Section: Discussionmentioning

confidence: 99%

“…With the introduction of composite pulses and more general shapes, pulse performance can usually be improved significantly. As has been shown previously, optimal control theory‐derived algorithms like GRAPE allow the highly efficient optimization of pulse shapes, as, for example, for broadband excitation, inversion, universal rotation, and other pulses that can be straightforwardly used in modern NMR spectroscopy (see e.g., Ref. ,,–,–]).…”

Section: Introductionmentioning

confidence: 99%

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Broadband excitation pulses with variable RF amplitude‐dependent flip angle (RADFA)

Koos

Feyrer

2015

Magnetic Reson in Chemistry

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Pulse sequences in NMR spectroscopy sometimes require the adjustment of effective flip angles with respect to experiment-specific or sample-specific parameters. Here, we present a quality factor for efficient optimization of offset-compensated broadband excitation pulses with RF amplitude-dependent effective flip angles (RADFA). After proof of principle, physical limits of RF amplitude-restricted and RF power-restricted broadband RADFA pulses are explored and corresponding pulse shapes and performances characterized in detail.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Broadband excitation pulses with variable RF amplitude‐dependent flip angle (RADFA)

Koos

Feyrer

2015

Magnetic Reson in Chemistry

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“…Since the pioneering work by Courtieu and co-workers on the determination of relative configuration by RDCs using poly-gbenzyl-l-glutamate (PBLG)/CDCl 3 , [8,9] more alignment media compatible with organic solvents are now available. [10][11][12][13][14][15][16][17][18][19][20][21][22] In natural products in particular, the power of RDCs for the resolution of configurational problems has been tested against known molecules such as menthol, [23] cyclosporin, [15] ludartin, [22] strychnine, [21,24] sphaeropsidin A, [11] sagittamide A, [25] archazolid A, [26] sodium cholate, [27] and even used, in the case of the novel glycoside sucro-neo-lambertellin [28] for the determination of the unknown configuration in several stereocenters. Another case is the configuration of a synthetic a-methylene-g-butyrolactone that could not be resolved by conventional means.…”

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confidence: 99%

Stereochemistry Determination by Powder X‐Ray Diffraction Analysis and NMR Spectroscopy Residual Dipolar Couplings

García¹,

Pagola²,

Navarro‐Vázquez³

et al. 2009

Angewandte Chemie

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Traditional techniques for stereochemistry analysis have limitations; for example solution NMR spectroscopy has spatial limitation for the transference of stereochemical information, and suitable single crystals for X-ray analysis may not be available. Residual dipolar coupling (RDC) and powder X-ray diffraction (PXRD) are both techniques whose use is not yet widespread. We report a double-blind solution of the structure of jaborosalactol 24 (1), a new withanolide isolated from Jaborosa parviflora (Phil.) A. T. Hunziker et Barboza, by RDCs and PXRD, since conventional NMR spectroscopy experiments such as nuclear Overhauser effect (NOE) and 3 J analysis did not provide a unique solution.NOE, [1] frequently combined with 3 J coupling constants analysis, [2] is one of the most powerful tools for structural and conformational analysis by solution NMR spectroscopy. Unfortunately, the determination of relative stereochemistry between remotely located stereocenters becomes problematic arising from the limitations imposed by the 1/r 6 dependence of NOE (where r = internuclear distance). However, when molecules are forced to adopt a minor degree of alignment in solution and no longer tumble isotropically, a measurable fraction of the dipolar coupling (0.01-0.1 %) can be observed in the NMR spectrum. These so called residual dipolar couplings [3][4][5][6][7] (RDCs) contain important structural information of non-local character, since their values depend not only on the internuclear distances but also on the angles between the internuclear vectors and the external magnetic field. Hence, they provide information about the relative orientation between the internuclear vectors (e.g., H-H, H-C, H-N, C-C, etc.), regardless of the distance between them. Since the pioneering work by Courtieu and co-workers on the determination of relative configuration by RDCs using poly-gbenzyl-l-glutamate (PBLG)/CDCl 3 , [8,9] more alignment media compatible with organic solvents are now available. [10][11][12][13][14][15][16][17][18][19][20][21][22] In natural products in particular, the power of RDCs for the resolution of configurational problems has been tested against known molecules such as menthol, [23] cyclosporin, [15] ludartin, [22] strychnine, [21,24] sphaeropsidin A, [11] sagittamide A, [25] archazolid A, [26] sodium cholate, [27] and even used, in the case of the novel glycoside sucro-neo-lambertellin [28] for the determination of the unknown configuration in several stereocenters. Another case is the configuration of a synthetic a-methylene-g-butyrolactone that could not be resolved by conventional means. [29] At present, PXRD analysis can be used to determine the crystal structures of small organic molecules. [30] One fruitful technique is realspace simulated annealing, in which trial structures are generated and optimized using a set of structural parameters that define the location, orientation, and conformation of the molecules in the solid, consistent with bond lengths and angles from the known (or hypothesized) molecular stru...

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RDC as a New NMR-Parameter for Peptides

Cited by 2 publications

References 10 publications

Broadband excitation pulses with variable RF amplitude‐dependent flip angle (RADFA)

Broadband excitation pulses with variable RF amplitude‐dependent flip angle (RADFA)

Stereochemistry Determination by Powder X‐Ray Diffraction Analysis and NMR Spectroscopy Residual Dipolar Couplings

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