Journal
JOURNAL OF MAGNETIC RESONANCE
Volume 202, Issue 1, Pages 57-63Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jmr.2009.09.018
Keywords
Solid-state NMR; Magic angle spinning (MAS); N-14; HMQC; HSQC; Homonuclear dipolar decoupling; Symmetry-based pulse sequence
Funding
- Swiss National Science Foundation [200020-124694]
- Swiss Commission for Technology and Innovation [9991.1 PFIW-IW]
Ask authors/readers for more resources
In solids spinning at the magic angle, the indirect detection of single-quantum (SQ) and double-quantum (DQ) N-14 spectra (l = 1) via spy nuclei S = 1/2 such as protons can be achieved in the manner of heteronuclear single- or multiple-quantum correlation (HSQC or HMQC) spectroscopy. The HMQC method relies on the excitation of two-spin coherences of the type T-11(l) T-11(S) and T-21(l) T-11(S) at the beginning of the evolution interval t(1). The spectra obtained by Fourier transformation from t(1) to omega(1) may be broadened by the homogenous decay of the transverse terms of the spy nuclei S. This broadening is mostly due to homonuclear dipolar S-S' interactions between the proton spy nuclei. In this work we have investigated the possibility of inserting rotor-synchronized symmetry-based C or R sequences and decoupling schemes such as Phase-Modulated Lee-Goldburg (PMLG) sequences in the evolution period. These schemes reduce the homonuclear proton-proton interactions and lead to all enhancement of the resolution of both SQ and DQ proton-detected N-14 HMQC spectra. In addition, we have investigated the combination of HSQC with symmetry-based sequences and PMLG and shown that the highest resolution in the N-14 dimension is achieved by using HSQC in combination with symmetry-based sequences of the R-type. We show improvements in resolution in samples of L-alanine and the tripeptide ala-ala-gly (AAG). In particular, for L-alanine the width of the N-14 SQ peak is reduced from 2 to 1.2 kHz, in agreement with simulations. We report accurate measurements of quadrupolar coupling constants and asymmetry parameters for amide N-14 in AAG peptide bonds. (C) 2009 Elsevier Inc. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available