Molecules (Jun 2023)

Exploring Proton-Only NMR Experiments and Filters for Daphnia In Vivo: Potential and Limitations

  • Kiera Ronda,
  • Katelyn Downey,
  • Amy Jenne,
  • Monica Bastawrous,
  • William W. Wolff,
  • Katrina Steiner,
  • Daniel H. Lysak,
  • Peter M. Costa,
  • Myrna J. Simpson,
  • Karl J. Jobst,
  • Andre J. Simpson

DOI
https://doi.org/10.3390/molecules28124863
Journal volume & issue
Vol. 28, no. 12
p. 4863

Abstract

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Environmental metabolomics provides insight into how anthropogenic activities have an impact on the health of an organism at the molecular level. Within this field, in vivo NMR stands out as a powerful tool for monitoring real-time changes in an organism’s metabolome. Typically, these studies use 2D 13C-1H experiments on 13C-enriched organisms. Daphnia are the most studied species, given their widespread use in toxicity testing. However, with COVID-19 and other geopolitical factors, the cost of isotope enrichment increased ~6–7 fold over the last two years, making 13C-enriched cultures difficult to maintain. Thus, it is essential to revisit proton-only in vivo NMR and ask, “Can any metabolic information be obtained from Daphnia using proton-only experiments?”. Two samples are considered here: living and whole reswollen organisms. A range of filters are tested, including relaxation, lipid suppression, multiple-quantum, J-coupling suppression, 2D 1H-1H experiments, selective experiments, and those exploiting intermolecular single-quantum coherence. While most filters improve the ex vivo spectra, only the most complex filters succeed in vivo. If non-enriched organisms must be used, then, DREAMTIME is recommended for targeted monitoring, while IP-iSQC was the only experiment that allowed non-targeted metabolite identification in vivo. This paper is critically important as it documents not just the experiments that succeed in vivo but also those that fail and demonstrates first-hand the difficulties associated with proton-only in vivo NMR.

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