Evaluation of double-tuned single-sided planar microcoils for the analysis of small 13C enriched biological samples using 1H-13C 2D heteronuclear correlation NMR spectroscopy |
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Authors: | Vincent Moxley-Paquette Bing Wu Daniel Lane Monica Bastawrous Paris Ning Ronald Soong Peter De Castro Ivan Kovacevic Thomas Frei Juerg Stuessi Danijela Al Adwan-Stojilkovic Stephan Graf Franck Vincent Daniel Schmidig Till Kuehn Rainer Kuemmerle Armin Beck Michael Fey Wolfgang Bermel Falko Busse Marcel Gundy Holger Boenisch Hermann Heumann Ben Nashman Rudraksha Dutta Majumdar Andressa Lacerda André J Simpson |
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Institution: | 1. Environmental NMR Center, University of Toronto, Toronto, Ontario, Canada;2. Magnetic Resonance Spectroscopy Division, Bruker BioSpin AG, Fällanden, Switzerland;3. Magnetic Resonance Spectroscopy Division, Bruker Corporation, Billerica, MA, USA;4. Magnetic Resonance Spectroscopy Division, Bruker Biospin GmbH, Rheinstetten, Germany;5. Research and Development, Silantes GmbH, Munich, Germany;6. Research and Development, Synex Medical, Toronto, Ontario, Canada |
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Abstract: | Microcoils provide a cost-effective approach to improve detection limits for mass-limited samples. Single-sided planar microcoils are advantageous in comparison to volume coils, in that the sample can simply be placed on top. However, the considerable drawback is that the RF field that is produced by the coil decreases with distance from the coil surface, which potentially limits more complex multi-pulse NMR pulse sequences. Unfortunately, 1H NMR alone is not very informative for intact biological samples due to line broadening caused by magnetic susceptibility distortions, and 1H-13C 2D NMR correlations are required to provide the additional spectral dispersion for metabolic assignments in vivo or in situ. To our knowledge, double-tuned single-sided microcoils have not been applied for the 2D 1H-13C analysis of intact 13C enriched biological samples. Questions include the following: Can 1H-13C 2D NMR be performed on single-sided planar microcoils? If so, do they still hold sensitivity advantages over conventional 5 mm NMR technology for mass limited samples? Here, 2D 1H-13C HSQC, HMQC, and HETCOR variants were compared and then applied to 13C enriched broccoli seeds and Daphnia magna (water fleas). Compared to 5 mm NMR probes, the microcoils showed a sixfold improvement in mass sensitivity (albeit only for a small localized region) and allowed for the identification of metabolites in a single intact D. magna for the first time. Single-sided planar microcoils show practical benefit for 1H-13C NMR of intact biological samples, if localized information within ~0.7 mm of the 1 mm I.D. planar microcoil surface is of specific interest. |
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Keywords: | 13C enriched mass limited biological samples heteronuclear 2D NMR metabolites surface microcoils |
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