Removal of Zero-Quantum Coherence in Protein NMR Spectra Using SESAM Decoupling and Suppression of Decoupling Sidebands
✍ Scribed by Johan Weigelt; Anna Hammarström; Wolfgang Bermel; Gottfried Otting
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 198 KB
- Volume
- 110
- Category
- Article
- ISSN
- 1064-1866
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✦ Synopsis
Time-shared homonuclear decoupling during acquisition to the spectral region 3.0 to 6.0 ppm during data acquisition.
Because the water signal is within the irradiated spectral was demonstrated by Jesson et al. more than 20 years ago (1). Recently, it has been shown that a train of semi-selec-range, intense decoupling artifacts from the water line would spread far into the amide-proton region. For maximum water tive-shaped inversion pulses, termed SESAM decoupling, can be used for the selective decoupling of broader spectral suppression, selective preirradiation of the water signal was combined with a WATERGATE ( 16) sequence using a regions in 1 H NMR experiments (2, 3). In the following, we show how SESAM decoupling can be used for the sup-semi-selective 180Њ refocusing pulse applied to the amide protons. The gradient echo of the WATERGATE sequence pression of J cross peaks in NOESY and ROESY experiments. In addition, a method for the suppression of decou-also defocuses all a-proton coherences. Any scalar couplings evolving with the amide protons during the WATERGATE pling sidebands resulting from SESAM decoupling is presented.
sequence are refocused by the semi-selective 180Њ pulse which ensures a pure lineshape during signal detection. The J cross peaks originate from zero-quantum coherences present during the mixing time (4, 5). They are particularly relevant product operator terms (17) left after the WA-TERGATE sequence are I Ny , 2I Nx I az and 4I Ny I a1z I a2z , where detrimental in NOESY and ROESY experiments recorded with short mixing times, where they may totally obscure the I N and I a denote amide-and a-proton spins, respectively, and the three-spin operator pertains to glycyl residues. SESAM NOE and ROE cross peaks between scalar-coupled protons. Complete suppression of zero-quantum coherences has decoupling applied to the a protons perfectly suppresses the term 2I Nx I az . proven difficult. They are neither suppressed by phase-cycling schemes nor by z-field gradients. A number of different