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14N–1H heteronuclear multiple-quantum correlation magic-angle spinning NMR spectroscopy of organic solids
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Tatton, Andrew S., Bradley, Jonathan P., Iuga, Dinu and Brown, Steven P. (2012) 14N–1H heteronuclear multiple-quantum correlation magic-angle spinning NMR spectroscopy of organic solids. Zeitschrift für Physikalische Chemie, Volume 226 (Number 11-12). pp. 1187-1204. doi:10.1524/zpch.2012.0308 ISSN 0942-9352.
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Official URL: http://dx.doi.org/10.1524/zpch.2012.0308
Abstract
14N-1H heteronuclear multiple-quantum correlation (HMQC) solid-state magic-angle spinning (MAS) NMR spectra recorded at a 1H Larmor frequency of 850MHz are presented for the dipeptide β-AspAla. A modified version of the pulse sequence presented by Gan et al. (Chem. Phys. Lett. 435 (2007) 163) that utilises rotary resonance recoupling (R3) at the n = 2 condition (ν1 = 2νR) is employed. Spectra recorded with a short recoupling period (under 200 μs) show two correlation peaks corresponding to the NH and NH3 moieties in the dipeptide. The quadrupolar product, PQ = CQ [1+(η2 Q/3)], is determined experimentally as 3.1MHz (NH) and 1.0MHz (NH3) by a comparison of the 14N and 15N isotropic chemical shifts which differ due to the isotropic second-order quadrupolar shift for the spin I = 114N nucleus. It is shown that the peak sensitivities increase markedly upon increasing the MAS frequency from 30 to 45 to 60 kHz due to a combination of the reduced residual dipolar broadening of the 1H resonances and a lengthening of the coherence lifetimes under R3 recoupling. Increasing the recoupling period leads to the observation of additional peaks corresponding to longer range intra- and intermolecular NH proximities. Reasonable agreement is evident upon comparing the experimental build-up of correlation peak intensity to that observed for eight-spin density-matrix simulations
Item Type: | Journal Article | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
Journal or Publication Title: | Zeitschrift für Physikalische Chemie | ||||
Publisher: | Oldenbourg Wissenschaftsverlag GmbH | ||||
ISSN: | 0942-9352 | ||||
Official Date: | November 2012 | ||||
Dates: |
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Volume: | Volume 226 | ||||
Number: | Number 11-12 | ||||
Page Range: | pp. 1187-1204 | ||||
DOI: | 10.1524/zpch.2012.0308 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access |
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