Direct detection of nitrogen-14 in solid-state NMR spectroscopy

O’Dell, Luke A.

doi:10.1016/j.pnmrs.2011.04.001

Cited by 73 publications

(23 citation statements)

References 216 publications

(192 reference statements)

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“…For each pair, the separation is equal to 0.75C Q (1 - η Q ), thus leading to 36 and 120 kHz in the figure. [18] However, when the 2 nd -order quadrupolar terms are taken into account, the spectrum becomes asymmetric (Fig.1c), as always observed experimentally, especially at low magnetic fields.…”

Section: Simulationssupporting

confidence: 72%

Revisiting NMR composite pulses for broadband 2 H excitation

Shen

Roopchand

Mananga

et al. 2015

Solid State Nuclear Magnetic Resonance

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Quadrupolar echo NMR spectroscopy of static solids often requires RF excitation that covers spectral widths exceeding 100 kHz, which is difficult to obtain due to instrumental limitations. In this work we revisit four well-known composite pulses (COM-I, II, III and IV) for broadband excitation in deuterium quadrupolar echo spectroscopy. These composite pulses are combined with several phase cycling schemes that were previously shown to decrease finite pulse width distortions in deuterium solid-echo experiments performed with two single pulses. The simulations and experiments show that COM-II and IV composite pulses combined with an 8-step phase cycling aid in achieving broadband excitation with limited pulse width distortions.

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Section: Simulationssupporting

confidence: 72%

Revisiting NMR composite pulses for broadband 2 H excitation

Shen

Roopchand

Mananga

et al. 2015

Solid State Nuclear Magnetic Resonance

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“…[11][12][13] Current methods for solid-state 14 N NMR spectroscopy rely on (i) piecewise acquisition 14 or frequency-swept excitation [15][16][17] in static samples, (ii) magic angle spinning (MAS) spectra utilizing small flip angle pulses so as to achieve broad excitation profiles, 18,19 (iii) overtone irradiation, [20][21][22][23][24][25][26][27][28] or (iv) heteronuclear multiple-quantum correlation (HMQC) experiments for the indirect detection of 14 N spectra via "spy" nuclei such as 1 H or 13 C. [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] The HMQC approach offers advantages in terms of sensitivity as magnetization on the target spin 14 N is created initially by transfer from 1 H and 13 C nuclei. Detailed reviews are available of both direct 44 and indirect 45 methods for the acquisition of nitrogen-14 NMR spectra. In this letter, we investigate the use of double cross polarization (DCP) 1 H → 14 N → 1 H for the indirect detection of nitrogen-14 spectra in powdered samples under MAS conditions.…”

Section: Introductionmentioning

confidence: 99%

Double cross polarization for the indirect detection of nitrogen-14 nuclei in magic angle spinning NMR spectroscopy

Carnevale

Bodenhausen

2017

The Journal of Chemical Physics

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Nitrogen-14 NMR spectra at fast magic-angle spinning rates can be acquired indirectly by means of two-dimensional techniques based on double cross polarization transfer H →N →H. Experimental evidence is given for polycrystalline samples of glycine, l-histidine, and the dipeptide Ala-Gly. Either one-bond or long-range correlations can be favored by choosing the length of the cross polarization contact pulses. Longer contact pulses allow the detection of unprotonated nitrogen sites. In contrast to earlier methods that exploited second-order quadrupolar/dipolar cross-terms, cross polarization operates in the manner of the method of Hartmann and Hahn, even for N quadrupolar couplings up to 4 MHz. Simulations explain why amorphous samples tend to give rise to featureless spectra because theN quadrupolar interactions may vary dramatically with the lattice environment. The experiments are straightforward to set up and are shown to be effective for different nitrogen environments and robust with respect to the rf-field strengths and to the N carrier frequency during cross polarization. The efficiency of indirect detection ofN nuclei by double cross polarization is shown to be similar to that of isotopically enriched C nuclei.

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“…The direct NMR detection of 14 N nuclei is challenging for several reasons [4][5][6]. First, it has a spin-1 value and hence no central transition between energy levels mN = ±1/2.…”

Section: Direct Detectionmentioning

confidence: 99%

Evaluation of excitation schemes for indirect detection of 14N via solid-state HMQC NMR experiments

Rankin

Trébosc

Paluch

et al. 2019

Journal of Magnetic Resonance

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It has previously been shown that 14 N NMR spectra can be reliably obtained through indirect detection via HMQC experiments. This method exploits the transfer of coherence between single-(SQ) or double-quantum (DQ) 14 N coherences, and SQ coherences of a suitable spin-1/2 'spy' nucleus, e.g., 1 H. It must be noted that SQ-SQ methods require a carefully optimized setup to minimize the broadening related to the first-order quadrupole interaction (i.e., an extremely well-adjusted magic angle and a highly stable spinning speed), whereas DQ-SQ ones do not. In this work, the efficiencies of four 14 N excitation schemes (DANTE, XiX, Hard Pulse (HP), and Selective Long Pulse (SLP)) are compared using J-HMQC based numerical simulations and either SQ-SQ or DQ-SQ 1 H-{ 14 N} D-HMQC experiments on Lhistidine HCl and N-acetyl-L-valine at 18.8 T and 62.5 kHz MAS. The results demonstrate that both DANTE and SLP provide a more efficient 14 N excitation profile than XiX and HP. Furthermore, it is shown that the SLP scheme: (i) is efficient over a large range of quadrupole interaction, (ii) is highly robust to offset and rf-pulse length and amplitude, and (iii) is very simple to set up. These factors make SLP ideally suited to widespread, non-specialist use in solid-state NMR analyses of nitrogen-containing materials.

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Direct detection of nitrogen-14 in solid-state NMR spectroscopy

Cited by 73 publications

References 216 publications

Revisiting NMR composite pulses for broadband 2 H excitation

Revisiting NMR composite pulses for broadband 2 H excitation

Double cross polarization for the indirect detection of nitrogen-14 nuclei in magic angle spinning NMR spectroscopy

Evaluation of excitation schemes for indirect detection of 14N via solid-state HMQC NMR experiments

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