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Spin dynamics in the modulation frame : application to homonuclear recoupling in magic angle spinning solid-state NMR
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De Paëpe, Gaël, Lewandowski, Józef R. and Griffin, Robert G. (2008) Spin dynamics in the modulation frame : application to homonuclear recoupling in magic angle spinning solid-state NMR. The Journal of Chemical Physics, Vol.128 (No.12). p. 124503. doi:10.1063/1.2834732
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Official URL: http://dx.doi.org/10.1063/1.2834732
Abstract
We introduce a family of solid-state NMR pulse sequences that generalizes the concept of second averaging in the modulation frame and therefore provides a new approach to perform magic angle spinning dipolar recoupling experiments. Here, we focus on two particular recoupling mechanisms-cosine modulated rotary resonance (CMpRR) and cosine modulated recoupling with isotropic chemical shift reintroduction (COMICS). The first technique, CMpRR, is based on a cosine modulation of the rf phase and yields broadband double-quantum (DQ) (13)C recoupling using > 70 kHz omega(1,C)/2 pi rf field for the spinning frequency omega(r)/2=10-30 kHz and (1)H Larmor frequency omega(0,H)/2 pi up to 900 MHz. Importantly, for p >= 5, CMpRR recouples efficiently in the absence of (1)H decoupling. Extension to lower p values (3.5 <= p < 5) and higher spinning frequencies is possible using low power (1)H irradiation (<0.25 omega(r)/2 pi). This phenomenon is explained through higher order cross terms including a homonuclear third spin assisted recoupling mechanism among protons. CMpRR mitigates the heating effects of simultaneous high power (13)C recoupling and (1)H decoupling. The second technique, COMICS, involves low power (13)C irradiation that induces simultaneous recoupling of the (13)C DQ dipolar and isotropic chemical shift terms. In contrast to CMpRR, where the DQ bandwidth (similar to 30 kHz at omega(0,H)/2 pi=750 MHz) covers the entire (13)C spectral width, COMICS recoupling, through the reintroduction of the isotropic chemical shift, is selective with respect to the carrier frequency, having a typical bandwidth of similar to 100 Hz. This approach is intended as a general frequency selective method circumventing dipolar truncation (supplementary to R(2) experiments). These new gamma-encoded sequences with attenuated rf requirements extend the applicability of homonuclear recoupling techniques to new regimes-high spinning and Larmor frequencies-and therefore should be of major interest for high resolution biomolecular studies. (C) 2008 American Institute of Physics.
| Item Type: | Journal Article | ||||
|---|---|---|---|---|---|
| Subjects: | Q Science > QC Physics Q Science > QD Chemistry |
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| Divisions: | Faculty of Science > Chemistry | ||||
| Library of Congress Subject Headings (LCSH): | Rotational motion, Nuclear magnetic resonance spectroscopy, Nuclear spin, Angular momentum (Nuclear physics) -- Coupling and recoupling | ||||
| Journal or Publication Title: | The Journal of Chemical Physics | ||||
| Publisher: | American Institute of Physics | ||||
| ISSN: | 0021-9606 | ||||
| Official Date: | 28 March 2008 | ||||
| Dates: |
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| Volume: | Vol.128 | ||||
| Number: | No.12 | ||||
| Page Range: | p. 124503 | ||||
| DOI: | 10.1063/1.2834732 | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Access rights to Published version: | Restricted or Subscription Access |
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