The CLIP/CLAP-HSQC: Pure absorptive spectra for the measurement of one-bond couplings

Enthart, Andreas; Freudenberger, J.; Furrer, Julien; Kessler, Horst; Luy, Burkhard

doi:10.1016/j.jmr.2008.03.009

Cited by 221 publications

(233 citation statements)

References 44 publications

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“…The 1 J CH values are obtained from a CLIP-HSQC experiment. [30] The number of scans required for obtaining an SNR of at least 10 for all resonances is also indicated, given that the SNR values shown have been obtained using 144 scans (the QDEPT scheme must be recorded using multiples of 48 scans). [6] ACCORDEPT spectra have been sampled using 16 been added for comparison purposes.…”

Section: Resultsmentioning

confidence: 99%

Accordion‐optimized DEPT experiments

Furrer

Guerra

Deschenaux

2010

Magnetic Reson in Chemistry

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In this contribution, a pulse sequence is described for recording accordion-optimized DEPT experiments. The proposed ACCORDEPT experiment detects a wide range of one-bond coupling constants using accordion optimization. As a proof of concept, this strategy has been applied to a mesogen containing a large range of one-bond 1 J CH coupling constants associated with the various structural elements. The ACCORDEPT experiment afforded significant enhancements for the resonances with the larger 1 J CH couplings, similar SNR for aliphatic resonances, but reduced SNR for aliphatic resonances as compared with the standard DEPT experiment. In addition, the ACCORDEPT is straightforward to implement, does not require any supplementary calibration procedures and can be used under automated conditions without difficulty by inexperienced users.Supporting information may be found in the online version of this article.

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Section: Resultsmentioning

confidence: 99%

Accordion‐optimized DEPT experiments

Furrer

Guerra

Deschenaux

2010

Magnetic Reson in Chemistry

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“…For their measurement we used the so-called CLIP-HSQC pulse sequence, a t 2 -coupled HSQC with pure absorption lineshapes [16]. Experiments for sucrose dissolved in the various gels were acquired on a Bruker DMX 600 MHz spectrometer, using the hard pulse version of the CLIP-HSQC as described in [16].…”

Section: Rdc Measurementmentioning

confidence: 99%

“…The pulse sequence was implemented using broadband excitation and inversion pulses as described in [16] (BEBOP and BIBOP pulses of 337.5 and 307.5 s and 10 kHz rf-amplitude [17]) on the carbon channel, allowing the center of the carbon spectrum to be set at 40 ppm with aromatic signals folded into the spectrum without loss in sensitivity. Depending on the degree of stretching, 72-104 scans per increment were recorded, leading to an overall experiment duration of 14-20 h per experiment.…”

Section: Rdc Measurementmentioning

confidence: 99%

“…Although the signal to noise ratio of the sucrose spectra seems to be sufficient for a highly accurate coupling measurement, extracted couplings deviate up to 2.6 Hz from the linear fit. For most deviations, the choice of 13 Cfrequency for the slice and the variation of line shapes within the multiplets (due to spectral artifacts or slight second order contributions [16]) seem to be responsible for the differences in individual coupling extractions. However, due to the linear relationship of RDCs with the quadrupolar splitting of the deuterated solvent, a linear fit through couplings measured at different stretchings leads to a slope that can be extracted with a significantly higher precision than would be possible from individual experiments.…”

Section: Rdc Measurementmentioning

confidence: 99%

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Precise Measurement of RDCs in Water and DMSO Based Gels Using a Silicone Rubber Tube for Tunable Stretching

Kummerlöwe¹,

Halbach²,

Laufer³

et al. 2008

TOSPECJ

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Abstract:Residual dipolar couplings (RDCs) are of great interest for the structure determination of biomacromolecules as well as of organic molecules like synthetic or natural products. Their accurate measurement requires a proper degree of alignment for the molecule under investigation. As has been shown recently, a stretching device based on a flexible silicone rubber tube provides an easy, rapid, and reversible variation of alignment strength. We show in this article that such an apparatus is not limited to gelatin, but can also be used with covalently cross-linked hydrogels and even gels with polar organic solvents like DMSO. Using sucrose and a cyclic hexapeptide, we were able to demonstrate that the approximately linear relation of alignment with the extension factor of the stretched gel allows the measurement of RDCs with high precision if corresponding spectra are acquired at various alignment strengths. The method seems to be widely applicable to the structure determination of molecules of arbitrary size using standard 5 mm NMR equipment.

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“…Therefore, NMR signals originating from GO are beyond the solution NMR detection limit. To acquire RDCs of sucrose, CLIP-HSQC spectra 11 were recorded in an isotropic solution as well as in the GO LC phase. 1 D C,H RDCs were extracted as the difference of the couplings measured under isotropic and anisotropic conditions.…”

mentioning

confidence: 99%

Graphene Oxide Liquid Crystals as a Versatile and Tunable Alignment Medium for the Measurement of Residual Dipolar Couplings in Organic Solvents

Lei

Sun

et al. 2014

J. Am. Chem. Soc.

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Residual dipolar couplings (RDCs) have proven to be an invaluable anisotropic NMR parameter for the structural elucidation of complex biopolymers and organic molecules. However, a remaining bottleneck limiting its wider use by organic and natural product chemists is the lack of a range of easily applicable aligning media for diverse organic solvents. In this study, graphene oxide (GO) liquid crystals (LCs) were developed to induce partial orientation of organic molecules to allow RDC measurements. These LCs were determined to be maintainable at very low concentrations (as low as 1 mg/ mL, corresponding to quadrupolar 2 H splittings ranging from 2.8 to 30 Hz and maximum 13 C− 1 H dipolar couplings of 20 Hz for camphor in a CH 3 COCH 3 /water system) and to be remarkably stable and broadly compatible with aqueous and organic solvents such as dimethyl sulfoxide, CH 3 COCH 3 , and CH 3 CN. Moreover, compared with those for other alignment media, very clean and high-quality NMR spectra were acquired with the GO molecules in solution because of their rigidity and high molecular weight. The developed medium offers a versatile and robust method for RDC measurements that may routinize the RDC-based structure determination of organic molecules. have been widely used to determine the 3D structures of biopolymers and organic molecules. Among these parameters, RDCs can reflect long-range structural restraints of global character and thus have been demonstrated to improve the precision and accuracy of NMR structures of biomolecules and to provide deeper insight into their internal dynamics. 4 In the past few years, RDC-enhanced structure analysis for organic molecules has attracted increasing attention because it allows the determination of the relative configuration of organic molecules in addition to constitution and conformation.

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The CLIP/CLAP-HSQC: Pure absorptive spectra for the measurement of one-bond couplings

Cited by 221 publications

References 44 publications

Accordion‐optimized DEPT experiments

Accordion‐optimized DEPT experiments

Precise Measurement of RDCs in Water and DMSO Based Gels Using a Silicone Rubber Tube for Tunable Stretching

Graphene Oxide Liquid Crystals as a Versatile and Tunable Alignment Medium for the Measurement of Residual Dipolar Couplings in Organic Solvents

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