Minimizing the effects of RF inhomogeneity and phase transients allows resolution of two peaks in the 1H CRAMPS NMR spectrum of adamantane

Brouwer, Darren H.; Horvath, Matthew

doi:10.1016/j.ssnmr.2015.10.005

Cited by 12 publications

(8 citation statements)

References 53 publications

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“…One-dimensional solidstate CP/MAS 13 C NMR spectra were obtained on this instrument using similar conditions as for the HETCOR experiment, but with a contact time of 5.0 ms. Solid-state 1 H NMR spectra were acquired on this instrument with a Bruker 1.3 mm H/X MAS probe using a rotorsynchronized echo pulse sequence (i.e., 90°−τ−90°−τ−acquire, where τ is the interpulse delay) with a recycle delay of 30 s and a 90°pulse of 2.0 μs, at a MAS frequency of 50 kHz. The 1 H and 13 C spectra were referenced to TMS (δ iso = 0 ppm) by setting the isotropic 1 H peak of adamantane to 1.8 ppm 52 and the isotropic 13 C carbonyl peak of glycine to 176.5 ppm. 53 GIPAW DFT Calculations.…”

Section: ■ Introductionmentioning

confidence: 99%

Capturing Elusive Polymorphs of Curcumin: A Structural Characterization and Computational Study

Matlinska

Wasylishen

Bernard

et al. 2018

Crystal Growth & Design

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Curcumin, a compound derived from the herb turmeric, has gained considerable attention because of its purported pharmacological activity, but its poor water solubility and low bioavailability impedes its therapeutic potential. In addition to the frequently studied curcumin polymorph, referred to as form I, another polymorph with enhanced water solubility, referred to as form II, or red curcumin, has also been reported. We discuss experimental challenges in isolating the red curcumin polymorph. In the course of our studies, we were unable to obtain a third reported polymorph, form III. We redetermined crystal structures of forms I and II of curcumin and present 13 C and 1 H solid-state nuclear magnetic resonance (NMR) spectra for these two forms, as well as 13 C− 1 H two-dimensional heteronuclear correlation (HETCOR) data. The experimental 1 H and 13 C nuclear magnetic resonance (NMR) chemical shifts are compared with GIPAW density functional theory values computed using CASTEP. Our research illustrates the utility of NMR spectroscopy in characterization of polymorphism in bulk samples.

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Section: ■ Introductionmentioning

confidence: 99%

Capturing Elusive Polymorphs of Curcumin: A Structural Characterization and Computational Study

Matlinska

Wasylishen

Bernard

et al. 2018

Crystal Growth & Design

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“…Despite the increased spinning speed, higher external magnetic fields and many different CRAMPS techniques, the resolution did not significantly increase in recent years and obtaining 1 H resolution remains an active field of research. [17][18][19][20] Earlier experiments have shown that the use of microcoils is especially suitable for homonuclear decoupling. 21 Compared to conventional NMR, microNMR (coil diameter o 1 mm) benefits from higher B 1 homogeneity over the sample and higher sensitivity since the signal to noise ratio is inversely proportional to the coil diameter.…”

Section: Introductionmentioning

confidence: 99%

High resolution triple resonance micro magic angle spinning NMR spectroscopy of nanoliter sample volumes

Brauckmann

Janssen

Kentgens

2016

Phys. Chem. Chem. Phys.

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To be able to study mass-limited samples and small single crystals, a triple resonance micro-magic angle spinning (μMAS) probehead for the application of high-resolution solid-state NMR of nanoliter samples was developed. Due to its excellent rf performance this allows us to explore the limits of proton NMR resolution in strongly coupled solids. Using homonuclear decoupling we obtain unprecedented (1)H linewidths for a single crystal of glycine (Δν(CH2) = 0.14 ppm) at high field (20 T) in a directly detected spectrum. The triple channel design allowed the recording of high-resolution μMAS (13)C-(15)N correlations of [U-(13)C-(15)N] arginine HCl and shows that the superior (1)H resolution opens the way for high-sensitivity inverse detection of heteronuclei even at moderate spinning speeds and rf-fields. Efficient decoupling leads to long coherence times which can be exploited in many correlation experiments.

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“…for the improvement of the performance of the pulse sequence (Vega, 2004). It was shown that changing the phase transients by changing the tuning of the probe can be used to improve the spectral quality obtained by an S2-DUMBO sequences (Brouwer and Horvath, 2015).…”

Section: Open Accessmentioning

confidence: 99%

Origin of the Residual Linewidth Under FSLG-Based Homonuclear Decoupling in MAS Solid-State NMR

Hellwagner

Grunwald

Ochsner

et al. 2019

Preprint

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Abstract. Homonuclear decoupling sequences in solid-state NMR under magic-angle spinning (MAS) show experimentally significantly larger residual linewidth than expected from Floquet theory to second order. We present an in-depth theoretical and experimental analysis of the origin of the residual linewidth in frequency-switched Lee-Goldburg (FSLG) based decoupling sequences. We analyze the effect of experimental pulse-shape errors (e.g. pulse transients and B1-field inhomogeneities) and use a Floquet-theory based description of higher-order error terms that arise from the interference between the MAS rotation and the pulse sequence. It is shown that the magnitude of the third-order auto term of a single homo- or heteronuclear coupled spin pair is important and leads to significant line broadening under FSLG decoupling. Furthermore, we show the dependence of these third-order error terms on the angle of the effective field with the B0 field. An analysis of second-order cross terms is presented that shows that the influence of three-spin terms is small since they are averaged by the pulse sequence. The importance of the static rf-field inhomogeneity is discussed and shown to be the main source of residual line broadening while pulse transients do not seem to play an important role. Experimentally, the influence of the combination of these error terms is shown by using restricted samples and pulse-transient compensation. The results show that all terms are additive but the major contribution to the residual linewidth comes from the rf-field inhomogeneity for the standard implementation of FSLG sequences, which is significant even for samples with a restricted volume.

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Minimizing the effects of RF inhomogeneity and phase transients allows resolution of two peaks in the 1H CRAMPS NMR spectrum of adamantane

Cited by 12 publications

References 53 publications

Capturing Elusive Polymorphs of Curcumin: A Structural Characterization and Computational Study

Capturing Elusive Polymorphs of Curcumin: A Structural Characterization and Computational Study

High resolution triple resonance micro magic angle spinning NMR spectroscopy of nanoliter sample volumes

Origin of the Residual Linewidth Under FSLG-Based Homonuclear Decoupling in MAS Solid-State NMR

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