PANSY: Parallel Acquisition NMR Spectroscopy

Parallel Acquisition NMR Spectroscopy (PANSY) is an innovation that increases the amount of NMR data that can be collected in a given amount of time. PANSY experiments are possible with new spectrometer hardware that includes multiple receivers.

Typical NMR analysis requires recording both ¹H and ¹³C spectra. Due mainly to the low natural abundance of ¹³C, recording ¹³C spectra is time consuming. Simultaneously recording ¹H spectra while acquiring a ¹³C spectrum could result in significant time savings. This has now become possible with the introduction of multiple receivers in new NMR spectrometer hardware¹.

The most trivial use of multiple receivers would be to record 1D ¹H and ¹³C spectra at the same time, however, since the ¹³C spectrum normally requires much more scans than the ¹H, this would not be the most efficient use of NMR time. Greater efficiencies could be achieved by simultaneously recording, for example, 2D ¹H-¹H spectra and a ¹³C spectrum. The initial PANSY publication² reports just that. It describes pulse sequences for the collection of a COSY or TOCSY spectrum while simultaneously recording a ¹³C-¹H HETCOR spectrum. This publication also pointed out that it is theoretically possible to simultaneously collect spectra of three nuclei, but did not demonstrate doing so.

A following publication³ describes the acquisition of HSQC and HMBC PANSY spectra that correlate ¹H or ¹⁹F with ¹³C or ¹⁵N. These experiments require a probe that can be simultaneously tuned to ¹H and ¹⁹F and an X nucleus, in addition to the multiple receiver console. While these experiments demonstrate the collection of spectra on four different nuclei, only two nuclei were used in each experiment. The simultaneous collection of spectra on three different nuclei was eventually demonstrated with an isotopically labelled protein used to simultaneously collect 2D ¹H-¹⁵N and ¹⁵N-¹³C spectra⁴.

The PANACEA experiment uses the PANSY concept to provide all the information necessary for structure elucidation in a single experiment. The initially published sequence⁵ provides a 1D ¹³C spectrum, a 2D ¹³C-¹³C INADEQUATE, multiplicity edited ¹H-¹³C HSQCs, and a 3D ¹H-¹³C J-HMBC. In addition to multiple receivers, this experiment required at least 10 mg of sample, nine hours of data collection and a cryogenically cooled probe optimised for ¹³C detection. A later publication⁶ optimised the PANACEA experiment for use on neat oils, emphasising the poor sensitivity of this experiment. Further publications from the same group that attempted to provide all the data for structure elucidation in a single experiment abandoned the PANACEA approach to return to an experiment that provides COSY, TOCSY and HETCOR spectra⁷.

At present the spectrometers in the Skaggs NMR Facility are not capable of PANSY experiments, but if we are able to upgrade to a new instrument PANSY experiments will be implemented and their utility tested.

References

1. Kupče Ē.
NMR with Multiple Receivers.
Top Curr Chem. 2013;335:71-96.

2. Kupče Ē, Freeman R, John BK.
Parallel Acquisition of Two-Dimensional NMR Spectra of Several Nuclear Species.
J Am Chem Soc. 2006 Aug;128(30):9606–9607.

3. Kupče E, Cheatham S, Freeman R.
Two-dimensional spectroscopy with parallel acquisition of ¹H-X and ¹⁹F-X correlations.
Magn Reson Chem. 2007 May;45(5):378–380.

4. Kupče Ē, Kay LE.
Parallel acquisition of multi-dimensional spectra in protein NMR.
J Biomol NMR. 2012 Sep;54(1):1–7.

5. Kupče E, Freeman R.
Molecular Structure from a Single NMR Experiment.
J Am Chem Soc. 2008 Aug 13;130(32):10788–10792.

6. Kupče Ē, Freeman R.
Molecular structure from a single NMR sequence (fast-PANACEA)
J Magn Reson. 2010 Sep;206(1):147–153.

7. Gierth P, Codina A, Schumann F, Kovacs H, Kupče Ē.
Fast experiments for structure elucidation of small molecules: Hadamard NMR with multiple receivers.
Magn Reson Chem. 2015 Nov;53(11):940–944.