Monday, January 28, 2008

JMR, February 2008

Literature review, January 28, 2008 - JMR up to February 2008
33S NMR (Jakobsen)
17O NMR (Asakura)

Journal of Magnetic Resonance
Vol: 190, Issue: 2, February, 2008
pp. 316-326

Title: Sensitivity enhancement in natural-abundance solid-state ^3^3S MAS NMR spectroscopy employing adiabatic inversion pulses to the satellite transitions
Authors: Hansen, M.R.; Brorson, M.; Bildsoe, H.; Skibsted, J.; Jakobsen, H.J.
Keywords: 33S MAS NMR; Sensitivity enhancement; WURST and hyperbolic secant inversion pulses; Population transfer; Inorganic sulfates; Tetrathiometallates

Abstract (English): The WURST (wideband uniform rate smooth truncation) and hyperbolic secant (HS) pulse elements have each been employed as pairs of inversion pulses to induce population transfer (PT) between the four energy levels in natural abundance solid-state ^3^3S (spin I=3/2) MAS NMR, thereby leading to a significant gain in intensity for the central transition (CT). The pair of inversion pulses are applied to the satellite transitions for a series of inorganic sulfates, the sulfate ions in the two cementitious materials ettringite and thaumasite, and the two tetrathiometallates (NH4)2WS4 and (NH4)2MoS4. These materials all exhibit ^3^3S quadrupole coupling constants (CQ) in the range 0.1-1.0MHz, with precise CQ values being determined from analysis of the PT enhanced ^3^3S MAS NMR spectra. The enhancement factors for the WURST and HS elements are quite similar and are all in the range 1.74-2.25 for the studied samples, in excellent agreement with earlier reports on HS enhancement factors (1.6-2.4) observed for other spin I=3/2 nuclei with similar CQ values (0.3-1.2MHz). Thus, a time saving in instrument time by a factor up to five has been achieved in natural abundance ^3^3S MAS NMR, a time saving which is extremely welcome for this important low-g nucleus.
# Item Identifier: S1090-7807(07)00354-0
Publication Type: Article ISSN: 1090-7807

Journal of Magnetic Resonance
Vol: 190, Issue: 2, February, 2008
pp. 327-332

Title: High field 17O solid-state NMR study of alanine tripeptides
Authors: Yamauchi, K.; Okonogi, M.; Kurosu, H.; Tansho, M.; Shimizu, T.; Gullion, T.; Asakura, T.
Keywords: Anti-parallel b-sheet; Parallel b-sheet; ^1^7O chemical shift; Ala-Ala-Ala; DFT
Abstract (English): 17O chemical shifts of Ala-Ala-Ala, with parallel and anti-parallel b-sheet structures, are observed using a 930-MHz high-resolution solid-state NMR spectrometer. Ala-Ala-Ala serves as a model sheet-forming peptide because it can be easily prepared as either a parallel or an anti-parallel b-sheet structure. Spectral differences between the two samples are observed which arise from molecular packing differences between the two sheet structures. DFT chemical shift calculations are performed for the two samples, and the calculated spectra are in good agreement with the experimental spectra. The DFT calculations provide insight into the nature of the chemical shift differences observed between the two sheet structures.
# Item Identifier: S1090-7807(07)00346-1
Publication Type: Miscellaneous ISSN: 1090-7807

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