Send to

Choose Destination
J Magn Reson. 2004 May;168(1):8-17.

Towards quantitative measurements in solid-state CPMAS NMR: A Lee-Goldburg frequency modulated cross-polarization scheme.

Author information

Center for Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA.


A new scheme combining a Lee-Goldburg (LG) sequence with frequency modulation is proposed for cross-polarization (LG-FMCP) in solid-state magic-angle-spinning nuclear magnetic resonance. During the CP contact time, the (1)H magnetization is spin-locked along the magic angle by the LG sequence and the irradiation offset of the S spins (e.g., (15)N) is modulated sinusoidally with a constant RF amplitude. It is shown experimentally that the LG sequence significantly lengthens the proton spin-lattice relaxation time in the tilted rotating frame and that the frequency modulation shortens the cross-polarization time for non-protonated S spins. As a result of substantially increasing the difference in these relaxation rates, the non-protonated and protonated S spins can be more efficiently and more uniformly polarized with a relatively long CP contact time, making quantitative CP measurements possible. A sample of (15)N-delta 1-L-histidine lyophilized from a solution of pH 6.3 and a (15)N-delta 1-L-His labeled transmembrane helical peptide in hydrated lipid bilayers were used to illustrate the advantages of this scheme.


Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center