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IMPEACH-MBC experiment

In 2000, Krishnamurthy et al. have presented the 2/,3/-HMBC experiment (Figure 20), that affords for the first time the means of unequivocally differentiating between 2/ch from 3Jch correlations.59 Their approach is based on a further derivative of the constant-time variable delay introduced in the IMPEACH-MBC experiment. The user-definable /-scaling factor of the CIGAR-HMBC is used in the new experiment, the 2J,3J-HMBC experiment, to differentiate between 2/CH from 3Jch correlations. This new pulse sequence element has been given the acronym STAR (Selectively Tailored Accordion F1 Refocused) operator. [Pg.324]

Figure 5.9 Comparison plots of the downfield region of (a) an 8-Hz optimized HMBC and (b) a 2-10-Hz accordion-optimized IMPEACH-MBC experiment. Both spectra were acquired using a 1.7-mm SMIDG NMR probe for identical times at 600-MHz. Figure 5.9 Comparison plots of the downfield region of (a) an 8-Hz optimized HMBC and (b) a 2-10-Hz accordion-optimized IMPEACH-MBC experiment. Both spectra were acquired using a 1.7-mm SMIDG NMR probe for identical times at 600-MHz.
Fig. 14.2 Comparison traces for the N9 amide resonance of strychnine top) trace extracted from a 3-16 Hz optimized IMPEACH-HMBC experiment bottom) trace extracted from a conventional 8 Hz optimized GHMBC spectrum. Parameters were adjusted to give equivalent data matrices, the only difference being total acquisition time because of the difference between the statically optimized delay in the case of the GHMBC experiment and the accordion-optimized delay in the IMPEACH-MBC experiment [36]. While the... Fig. 14.2 Comparison traces for the N9 amide resonance of strychnine top) trace extracted from a 3-16 Hz optimized IMPEACH-HMBC experiment bottom) trace extracted from a conventional 8 Hz optimized GHMBC spectrum. Parameters were adjusted to give equivalent data matrices, the only difference being total acquisition time because of the difference between the statically optimized delay in the case of the GHMBC experiment and the accordion-optimized delay in the IMPEACH-MBC experiment [36]. While the...
Long-range heteronuclear shift correlation. Russell et al have demonstrated the viability of F-detected long-range IMPEACH-MBC experiments... [Pg.112]

In an effort to address the essentially uncontrolled F skew inherent to the ACCORD-HMBC, the author and co-workers next reported the development of the IMPEACH-MBC experiment, the pulse sequence for which is shown in Fig, 14. Recognizing that F skew arises due to homonuclear scalar coupling modulation for which the variable duration accordion-optimized delay serves as an evolution time, the variable delay, vd, was modified in the IMPEACH-MBC experiment. The variable delay can be made into a constant time delay for homonuclear components of magnetization by adding a new segment to the overall delay centered about a 180° X pulse to refocus heteronuclear magnetization. The thus modified constant time variable delay is given by... [Pg.68]

Retrospectively, after demonstrating in the implementation of the IMPEACH-MBC experiment that it is possible to suppress F skew, it was evident that the skew of responses in F, while a nuisance if uncontrolled, could serve as a useful means of response authentication if Fi skew was under user control. The CIGAR-HMBC experiment aeeomplishes this task. While the constant time variable delay of the IMPEACH-MBC experiment (see Eq. (8)) renders the duration of the variable delay constant, the CIGAR-HMBC pulse sequence modifies the variable delay interval of the experiment still further, as shown below the complete puLse sequence is shown in Fig. 17. [Pg.70]

Rather than incrementing the D/2 intervals flanking the 180° X pulse as in the IMPEACH-MBC experiment, D is Instead incremented by... [Pg.70]

While uncontrolled F response skew of the type encountered in the ACCORD-HMBC experiment is undesirable [145], user-defined Fj skew can be a useful determinant of response authenticity. A further generation accordion-optimized long-range experiment, CIGAR-HMBC, was developed to provide this flexibility. The constant time variable delay from the IMPEACH-MBC experiment was further modified as follows ... [Pg.247]

Fig. 8.27 F] skew inherent to responses in ACCORD-HMBC spectra is only partially user controllable. These properties prompted the development of the IMPEACH-MBC experiment [146], which suppresses F skew. Further modification to re-introduce user-controlled F skew was incorporated into the CIGAR-HMBC experiment using a parameter called jg aie [147]. The effect of adjusting the Js aie pai a-meter in the CIGAR-HMBC experiment is shown for the 3-methylene group of 2-penta-none over a range ofJscaie settings from 0 to 24. Fig. 8.27 F] skew inherent to responses in ACCORD-HMBC spectra is only partially user controllable. These properties prompted the development of the IMPEACH-MBC experiment [146], which suppresses F skew. Further modification to re-introduce user-controlled F skew was incorporated into the CIGAR-HMBC experiment using a parameter called jg aie [147]. The effect of adjusting the Js aie pai a-meter in the CIGAR-HMBC experiment is shown for the 3-methylene group of 2-penta-none over a range ofJscaie settings from 0 to 24.

See other pages where IMPEACH-MBC experiment is mentioned: [Pg.135]    [Pg.149]    [Pg.56]    [Pg.68]    [Pg.415]    [Pg.70]    [Pg.72]    [Pg.72]    [Pg.73]    [Pg.86]    [Pg.87]    [Pg.90]    [Pg.218]    [Pg.228]    [Pg.246]    [Pg.248]    [Pg.251]   
See also in sourсe #XX -- [ Pg.56 , Pg.68 , Pg.70 ]

See also in sourсe #XX -- [ Pg.57 , Pg.68 , Pg.69 , Pg.69 , Pg.71 , Pg.72 ]




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