Improvements, extensions, and practical aspects of rapid ASAP-HSQC and ALSOFAST-HSQC pulse sequences for studying small molecules at natural abundance

• DOI: 10.1016/j.jmr.2017.05.012
• Publication Date: 2017-05-24T13:48:29Z
• Authors: David Schulze-Sün...; Johanna Becker; Martin R.M. Koos; Burkhard Luy
• Keywords: Heteronuclear molecule; Decoupling (probability); Artifact (error); Pulse sequence

Previously we introduced two novel NMR experiments for small molecules, the so-called ASAP-HSQC and ALSOFAST-HSQC (Schulze-Sünninghausen et al., 2014), which allow the detection of heteronuclear one-bond correlations in less than 30s at natural abundance. We propose an improved symmetrized pulse scheme of the basic experiment to minimize artifact intensities and the combination with non-uniform sampling to enable the acquisition of conventional HSQC spectra in as short as a couple of seconds and extremely 13C-resolved spectra in less than ten minutes. Based on steady state investigations, a first estimate to relative achievable signal intensities with respect to conventional, ASAP-, and ALSOFAST-HSQC experiments is given. In addition, we describe several extensions to the basic pulse schemes, like a multiplicity-edited version, a revised symmetrized CLIP-ASAP-HSQC, an ASAP-/ALSOFAST-HSQC sequence with broadband BIRD-based 1H,1H decoupling, and a symmetrized sequence optimized for water suppression. Finally, RF-power considerations with respect to the high duty cycle of the experiments are given.