NOAH (NMR by Ordered Acquisition using 1H detection) supersequences are specially designed experiments which produce multiple 2D spectra in the time required for one.
This is accomplished by separately manipulating different isotopologues present within a typical natural-abundance sample. As a simple example, 1H–13C spin pairs can be used to record an HSQC spectrum while leaving 1H–12C spin pairs untouched. These can then be used to record a COSY spectrum without having to wait for them to relax. The removal of separate recovery delays for both 1H–13C and 1H–12C spin pairs (d1 in the graphic below) is what leads to the time savings in NOAH supersequences.
In the above depiction, two different experiments (“modules”) are combined leading to an approximate twofold speedup in data acquisition. As of the time of writing (2022), the maximum number of experiments which can be combined is five; this typically yields around 4× reductions in experiment time.
A huge variety of 2D experiments can be combined to form NOAH supersequences, including (but not limited to) HMBC, HSQC, HMQC, COSY, TOCSY, NOESY, and ROESY. With very few exceptions, the resulting spectra are identical to standard 2D experiments which chemists are familiar with.
For more information, please visit the GENESIS website https://nmr-genesis.co.uk which contains:
- automatic pulse programme generation for Bruker spectrometers depending on which experiments are to be combined
- thorough instructions on how to acquire and process NOAH experiments
- all requisite acquisition and processing scripts
and/or check out some of the following papers:
- Kupče, Ē.; Claridge, T. D. W. NOAH: NMR Supersequences for Small Molecule Analysis and Structure Elucidation. Angew. Chem. Int. Ed. 2017, 56 (39), 11779–11783. DOI: 10.1002/anie.201705506.
- Kupče, Ē.; Frydman, L.; Webb, A.; Yong, J. R. J.; Claridge, T. D. W. Parallel nuclear magnetic resonance spectroscopy. Nat. Rev. Methods Primers 2021, 1, No. 27. DOI: 10.1038/s43586-021-00024-3.
- Yong, J. R. J.; Kupče, Ē.; Claridge, T. D. W. Modular Pulse Program Generation for NMR Supersequences. Anal. Chem. 2022, 94 (4), 2271–2278. DOI: 10.1021/acs.analchem.1c04964.