| A robust technique for two-dimensional separation of undistorted chemical-shift anisotropy powder patterns in magic-angle-spinning NMR. | |
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MedLine Citation:
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PMID: 11945029 Owner: NLM Status: PubMed-not-MEDLINE |
Abstract/OtherAbstract:
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A robust magic-angle-spinning experiment for separating undistorted, quasi-static chemical-shift powder patterns is presented. It is derived from the technique of R. Tycko, G. Dabbagh, and P. Mirau (1989, J. Magn. Reson. 85, 265), but uses 360 degrees instead of 180 degrees pulses. In combination with a suitable phase sequence, this makes the spectral patterns very insensitive to pulse-length errors and other imperfections, as demonstrated both experimentally and theoretically. This method, termed separation of undistorted powder patterns by effortless recoupling (SUPER), can be used at standard spinning speeds, between 2.5 and 5 kHz, and with standard radiofrequency power levels (in particular, for protons, a decoupling field strength gammaB(1)/2pi of less than 80 kHz). No significant artifacts are observed even for samples extending to the ends of the radiofrequency coil. The method has been applied to samples containing various sp(2)- and sp(3)-hybridized carbon sites. Even for the methylene groups in polyethylene, a system with very strong C-H and H-H dipolar couplings and only moderate chemical-shift anisotropy (CSA), a useful CSA powder pattern has been obtained. With a CSA scaling factor of 0.155, accuracies of +/-5, +/-3, and +/-1 ppm of the principal values can be achieved for protonated aromatic carbons, unprotonated sp(2)-hybridized groups, and aliphatic sites, respectively. Examples of CSA-based assignment of COOC vs other COO or CON groups, and of aromatic vs olefinic C=C carbons are shown, for both small molecules and polymers. |
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Authors:
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S-F Liu; J-D Mao; K Schmidt-Rohr |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Journal of magnetic resonance (San Diego, Calif. : 1997) Volume: 155 ISSN: 1090-7807 ISO Abbreviation: J. Magn. Reson. Publication Date: 2002 Mar |
Date Detail:
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Created Date: 2002-04-11 Completed Date: 2002-06-12 Revised Date: 2003-11-03 |
Medline Journal Info:
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Nlm Unique ID: 9707935 Medline TA: J Magn Reson Country: United States |
Other Details:
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Languages: eng Pagination: 15-28 Citation Subset: - |
Copyright Information:
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(c) 2002 Elsevier Science (USA). |
Affiliation:
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Department of Chemistry and Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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