Doubly compensated multiplicity‐edited HSQC experiments utilizing broadband inversion pulses

Abstract

We propose a family of doubly compensated multiplicity-edited heteronuclear single quantum coherence (HSQC) pulse sequences. The key difference between our proposed sequences and the compensation of refocusing inefficiency with synchronized inversion sweeps (CRISIS)-HSQC experiments they are based on is that the conventional rectangular 180 degrees pulses on the proton channel in the latter have been replaced by the computer-optimized broadband inversion pulses (BIPs) with superior inversion performance as well as much improved tolerance to B(1) field inhomogeneity. Moreover, all adiabatic carbon 180 degrees pulses during the INEPT and reverse-INEPT periods in the CRISIS-HSQC sequences have also been replaced with the much shorter BIPs, while the adiabatic sweeps during the heteronuclear spin echo for multiplicity editing are kept in place in order to maintain the advantage of the CRISIS feature of the original sequences, namely J-independent refocusing of the one-bond (1)H--(13)C coupling constants. These modifications have also been implemented to the preservation of equivalent pathways (PEP)-HSQC experiments. We demonstrate through a detailed comparison that replacing the proton 180 degrees pulses with the BIPs provide additional sensitivity gain that can be mainly attributed to the improved tolerance to B(1) field inhomogeneity of the BIPs. The proposed sequences can be easily adapted for (19)F--(13)C correlations.

Suppressing One‐Bond Correlations in HMBC Spectra: Improved Performance for the BIRD–HMBC Pulse Sequence

“…[33] The phase error induced by the first BIP is then exactly compensated by that of the second, leading to optimum performance. [30,33,34] The 180…”

“…[29] In this report we investigate the implementation of a double tuned G-BIRD filter in the original BIRD-HMBC pulse sequence. We also investigate the implementation of the broadband inversion pulses BIPs and carefully optimized adiabatic 13 C inversion pulses for replacing the 13 [30] With the proposed modified version, the weaknesses of the original BIRD-HMBC experiment are expected to be eliminated, and the overall performance of the pulse sequence improved significantly.…”

Application of CRAFT in two‐dimensional NMR data processing

“…demonstrates the improvement in the quality of the 2D spectrum when the data are processed by CRAFT. The c2hsqc 2D spectrum of gibberellic acid obtained using 128 t 1 increments and conventionally processed after 2× linear prediction (blue contours) is overlaid with the CRAFT 2D spectrum of the same dataset (red contours). The 1D traces compare the F 1 projections of conventionally processed datasets with increasing number of t 1 increments with the corresponding projection of the CRAFT 2D spectrum.…”

Quantitative two-dimensional HSQC experiment for high magnetic field NMR spectrometers

“…Another technique specifically designed for uniform manipulation of magnetization over a wide chemical shift range utilizes adiabatic fast passages [24,25]. The broadband pulses have been successfully applied to compensate the off-resonance effects in 2D 1 H-13 C correlation experiments [26][27][28][29] and 2D 1 H-15 N correlation experiments [30], but their application in quantitative 2D NMR needs some consideration. The main focus in our study was to find suitable 13 C pulse elements for HSQC-type experiments in order to develop a quantitative 2D proton-carbon correlation experiment usable in high magnetic field strengths.…”