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Resolution enhancement in 13C and 15N magic-angle turning experiments with TPPM decoupling
G McGeorge1, D W Alderman, D M Grant
1Department of Chemistry, University of Utah, Salt Lake City, Utah, 84112-0850, USA.
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|March 4, 1999
Summary
Two-pulse phase-modulation (TPPM) decoupling improves solid-state NMR spectra by enhancing proton decoupling for carbon and nitrogen nuclei, especially in methylene and NH2 groups, even at low magic-angle turning speeds.
Area of Science:
- Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
- Materials Science
- Organic Chemistry
Background:
- Poor proton decoupling of carbon nuclei in methylene groups under slow magic-angle turning conditions affects solid-state NMR spectra.
- Similar issues arise when observing the 15N nucleus, particularly in NH2 groups.
Purpose of the Study:
- To evaluate the effectiveness of two-pulse phase-modulation (TPPM) decoupling in improving solid-state NMR spectra.
- To compare TPPM decoupling with conventional continuous wave (CW) decoupling at various magic-angle turning rates.
Main Methods:
- Utilized the 2D PHORMAT chemical shift separation experiment.
- Applied two-pulse phase-modulation (TPPM) decoupling.
- Observed 15N resonances in fully labeled l-arginine hydrochloride.
Main Results:
- TPPM decoupling proved more effective than conventional CW decoupling at higher spin rates.
- Significant line narrowing (approximately a factor of two) was observed for 15N resonances in l-arginine hydrochloride.
- These advantages were achieved at moderate rotation rates and turning frequencies as low as 500 Hz.
Conclusions:
- TPPM decoupling effectively overcomes limitations in proton decoupling for solid-state NMR, particularly for methylene and NH2 groups.
- This technique offers substantial spectral improvements at lower magic-angle turning frequencies, enhancing spectral resolution and sensitivity.