PFG-ω1-Filtered TOCSY Experiments for the Determination of Long-Range Heteronuclear and Homonuclear Coupling Constants and Estimation ofJ-Coupling “Crosstalk” Artifacts in 2-D ω1-Filtered “E. COSY-Style” Spectra
✍ Scribed by Guangzhao Xu; Bo Zhang; John Spencer Evans
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 243 KB
- Volume
- 138
- Category
- Article
- ISSN
- 1090-7807
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✦ Synopsis
We present novel one-and two-dimensional versions of the 1 -filtered TOCSY experiment. These experiments utilize pulsedfield gradient techniques and INEPT-reverse INEPT magnetization transfer to generate heteronuclear filtering by means of coherence pathway selection. The major advantages of this approach are twofold: first, each experiment requires a reasonable number of transmitter pulses, gradient pulses, and delays to implement. Second, the use of z-axis gradients at the beginning and termination of the pulse sequences prevents the recovery of dephased magnetization prior to FID detection. This technique was incorporated into 1-D and 2-D 1 -filtered J XH -and J HH -TOCSY-style experiments. As demonstrated on 15 N-enriched peptide samples, the use of the pulsed-field-gradient coherence selection scheme effectively filters out unwanted magnetization components, thereby improving the overall sensitivity of the experiments. In addition to this suite of pulse sequences, we also present a method for correcting the reduction in J-coupling that results from crosspeak shifting in 2-D 1 -filtered E. COSY-style spectra. This correction is applicable to both Lorentzian and Gaussian 2-D crosspeak lineshapes.