Magic angle Lee-Goldburg frequency offset irradiation improves the efficiency and selectivity of SPECIFIC-CP in triple-resonance MAS solid-state NMR.

 In
by Chin H Wu, Anna A De Angelis, Stanley J Opella
Abstract:
The efficiency and selectivity of SPECIFIC-CP, a widely used method for selective double cross-polarization in triple-resonance magic angle spinning solid-state NMR, is improved by performing the tangential-shaped (13)C irradiation at an offset frequency that meets the Lee-Goldburg condition (LG-SPECIFIC-CP). This is demonstrated on polycrystalline samples of uniformly (13)C, (15)N labeled N-acetyl-leucine and N-formyl-Met-Leu-Phe-OH (MLF) at 700MHz and 900MHz (1)H resonance frequencies, respectively. For the single (13)C$alpha$ of N-acetyl-leucine, relative to conventional broad band cross-polarization, the SPECIFIC-CP signal has 47% of the intensity. Notably, the LG-SPECIFIC-CP signal has 72% of the intensity, essentially the theoretical maximum. There were no other changes in the experimental parameters. The three (13)C$alpha$ signals in MLF show some variation in intensities, reflecting the relatively narrow bandwidth of a frequency-offset procedure, and pointing to future developments for this class of experiment.
Reference:
Magic angle Lee-Goldburg frequency offset irradiation improves the efficiency and selectivity of SPECIFIC-CP in triple-resonance MAS solid-state NMR. (Chin H Wu, Anna A De Angelis, Stanley J Opella), In Journal of magnetic resonance (San Diego, Calif. : 1997), volume 246, 2014.
Bibtex Entry:
@article{Wu2014,
abstract = {The efficiency and selectivity of SPECIFIC-CP, a widely used method for selective double cross-polarization in triple-resonance magic angle spinning solid-state NMR, is improved by performing the tangential-shaped (13)C irradiation at an offset frequency that meets the Lee-Goldburg condition (LG-SPECIFIC-CP). This is demonstrated on polycrystalline samples of uniformly (13)C, (15)N labeled N-acetyl-leucine and N-formyl-Met-Leu-Phe-OH (MLF) at 700MHz and 900MHz (1)H resonance frequencies, respectively. For the single (13)C$alpha$ of N-acetyl-leucine, relative to conventional broad band cross-polarization, the SPECIFIC-CP signal has 47{%} of the intensity. Notably, the LG-SPECIFIC-CP signal has 72{%} of the intensity, essentially the theoretical maximum. There were no other changes in the experimental parameters. The three (13)C$alpha$ signals in MLF show some variation in intensities, reflecting the relatively narrow bandwidth of a frequency-offset procedure, and pointing to future developments for this class of experiment.},
author = {Wu, Chin H and {De Angelis}, Anna A and Opella, Stanley J},
doi = {10.1016/j.jmr.2014.06.012},
issn = {1096-0856},
journal = {Journal of magnetic resonance (San Diego, Calif. : 1997)},
keywords = {LG-SPECIFIC-CP,Lee–Goldburg,Magic angle spinning,Peptides,SPECIFIC-CP,Triple-resonance},
month = {sep},
pages = {1--3},
pmid = {25051542},
title = {{Magic angle Lee-Goldburg frequency offset irradiation improves the efficiency and selectivity of SPECIFIC-CP in triple-resonance MAS solid-state NMR.}},
url = {http://linkinghub.elsevier.com/retrieve/pii/S1090780714001815 http://www.ncbi.nlm.nih.gov/pubmed/25051542 http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC4165850},
volume = {246},
year = {2014}
}

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