Volume 86 Issue 31 | p. 10 | News of The Week
Issue Date: August 4, 2008

Panacea For NMR

Combining pulse sequences into a single experiment cuts instrument time
Department: Science & Technology
Kupče loads a sample into an NMR spectrometer.
Credit: Dimitris Argyropoulos
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Kupče loads a sample into an NMR spectrometer.
Credit: Dimitris Argyropoulos

ONE EXPERIMENT now can yield the same information that previously required separate runs to acquire one-, two-, and three-dimensional nuclear magnetic resonance spectra. Recording several NMR spectra in parallel rather than in series cuts down on instrument time and ensures that any changes to the sample composition register in all spectra, say the researchers who figured out how to do it.

NMR experts Ériks Kupče at Oxford-based Varian and Ray Freeman at Jesus College, Cambridge, both in England, combined established protocols for acquiring data, called pulse sequences, into one "super sequence." They call their new scheme PANACEA—parallel acquisition NMR, an all-in-one combination of experimental applications (J. Am. Chem. Soc., DOI: 10.1021/ja8036492).

Just to acquire data from the natural isotopic abundance of a 10–15-mg sample can easily take a weekend's worth of instrument time, says Eugene P. Mazzola, an NMR specialist and adjunct chemistry professor at the University of Maryland. PANACEA could cut experiment time to an overnight run, he adds.

PANACEA takes advantage of recent advances in NMR instrumentation that made possible the parallel acquisition of signals from up to four nuclei. To test their new super sequence, Kupče and Freeman ran samples of melatonin and quinine through a commercially available 500-MHz NMR spectrometer equipped with a cryogenically cooled probe and receivers for three nuclei: 1H, 13C, and 15N. Their method, which combined a standard 13C experiment along with 2- and 3-D 13C–13C, 13C –1H, and 15N–1H correlation experiments, provided spectra that the researchers used to piece together structures that match the established ones, including stereochemistry.

The researchers acknowledge that the PANACEA protocol is not currently designed for determining structures of large molecules, but that may be possible in the future. Kup??e adds that he and Freeman have recorded preliminary data on NMR systems with receivers for four nuclei, such as 1H, 13C, 15N, and 19F, as well as 1H, 15N, 19F, and 31P.

 
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ISSN 0009-2347
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