NMR

Nuclear Magnetic Resonance Spectroscopy (NMR)

Nuclear Magnetic Resonance Spectroscopy
Source: Helmholtz Zentrum München

NMR spectroscopy is a powerful tool for detecting, identifying and quantifying a wide range of high and low molecular weight compounds without any prior selection and with little sample preparation. Furthermore, it provides invaluable information about the detailed molecular and chemical structure of the measured compounds. NMR can be quantitative, if the experiment is carried out appropriately.

We apply this technique to complex organic mixtures, such as human and animal biofluids or tissues and samples from various environmental fields involving pristine environments (e.g. marine or natural waters).

Metabolomics & small molecules

1H NMR-based metabolomics has shown its usefulness in analyzing a variety of biofluids and tissue extracts. The absence of analytical suppression effects allows a quantitative and therefore inter-sample comparison of main metabolite quantities. Through the availability of high-field instruments and the use of cryogenic probes sensitivity increases and 2-dimensional experiments are possible in a feasible time. Especially 2D experiments (e.g. 1H-13C-HSQC, 1H-1H-TOCSY, J-resolved) are necessary to aid and confirm signal annotation to metabolites.
Our equipment and developments ensure the management of large biofluids sample sets, i.e. automated sample preparation and cooled autosampler for sample stability while 24-7 measurement. Our high-resolution NMR spectrometer enables the elucidation of new molecules and constantly expands the number of metabolites detectable and identifiable in various biosamples.

NMR characterization of biogeochemical materials

High-field NMR spectroscopy enables quantitative and non-destructive de novo determination of chemical environments from polydisperse and molecularly heterogeneous environmental samples, such as natural organic matter (NOM). In all ecosystems, the quantity as well as the molecular diversity of NOM exceeds that of all living matter by several orders of magnitude.
Quantitative relationships between number of spins and area (1D NMR) and volume (2D NMR) of NMR resonances operate in absence of differential NMR relaxation which is more pronounced in 2D NMR than in 1D NMR experiments. This key feature implies the use of NMR spectroscopy as a quantitative reference for complementary structure-selective analytical methods, like mass spectrometry (which detects gas phase ions and is subject to ionization selectivity in case of complex mixtures) and fluorescence spectroscopy (which selectively detects fluorescent chemical environments of sp2-hybridized carbon).
NMR spectroscopy is particularly informative in the description of aliphatic chemical environments which are based on sp3-hybridized carbon. These are inactive in fluorescence spectroscopy, and difference in size of aliphatic groups will cause rather inconspicuous mass shifts in FT-ICR mass spectra: more expansive aliphatic systems will result in higher mass molecules, with somewhat larger H/C and lower O/C elemental ratios. This characteristic is however insufficient to allow reliable conclusions about chemical structures. NMR spectroscopy enables distinction of the size of aliphatic units but also allows for in-depth assessment of its intrinsic chemical environments, like open chain and cyclic arrangements of carbon.
In general, NMR spectroscopy of NOM of atmospheric, soil, freshwater, marine and extraterrestrial origin has fundamentally redefined our perception of its molecular arrangements.

Selected publications:

Kamjunke, N., Nimptsch, J., Harir, M., Herzsprung, P., Schmitt-Kopplin, P., Neu, T. R., ... & Woelfl, S. (2017). Land-based salmon aquacultures change the quality and bacterial degradation of riverine dissolved organic matter. Scientific Reports, 7.

Gil, R. B., Lehmann, R., Schmitt-Kopplin, P., & Heinzmann, S. S. (2016). 1H NMR-based metabolite profiling workflow to reduce inter-sample chemical shift variations in urine samples for improved biomarker discovery. Analytical and bioanalytical chemistry, 408(17), 4683-4691.

Li, Y., Harir, M., Lucio, M., Kanawati, B., Smirnov, K., Flerus, R., ... & Hertkorn, N. (2016). Proposed guidelines for solid phase extraction of Suwannee River dissolved organic matter. Analytical chemistry, 88(13), 6680-6688.

Hertkorn, N., Harir, M., Cawley, K. M., Schmitt-Kopplin, P., & Jaffé, R. (2016). Molecular characterization of dissolved organic matter from subtropical wetlands: a comparative study through the analysis of optical properties, NMR and FTICR/MS. Biogeosciences, 13, 2257-2277.

Lagkouvardos, I., Kläring, K., Heinzmann, S. S., Platz, S., Scholz, B., Engel, K. H., ... & Clavel, T. (2015). Gut metabolites and bacterial community networks during a pilot intervention study with flaxseeds in healthy adult men. Molecular nutrition & food research, 59(8), 1614-1628.

Hertkorn, N., Harir, M., & Schmitt‐Kopplin, P. (2015). Nontarget analysis of Murchison soluble organic matter by high‐field NMR spectroscopy and FTICR mass spectrometry. Magnetic Resonance in Chemistry, 53(9), 754-768.

Heinzmann, S. S., & Schmitt-Kopplin, P. (2015). Deep metabotyping of the murine gastrointestinal tract for the visualization of digestion and microbial metabolism. Journal of proteome research, 14(5), 2267-2277.

Hertkorn, N., Harir, M., & Schmitt‐Kopplin, P. (2015). Nontarget analysis of Murchison soluble organic matter by high‐field NMR spectroscopy and FTICR mass spectrometry. Magnetic Resonance in Chemistry, 53(9), 754-768.

Zhang, F., Harir, M., Moritz, F., Zhang, J., Witting, M., Wu, Y., ... & Hertkorn, N. (2014). Molecular and structural characterization of dissolved organic matter during and post cyanobacterial bloom in Taihu by combination of NMR spectroscopy and FTICR mass spectrometry. Water research, 57, 280-294.

Hertkorn, N., Harir, M., Koch, B., Michalke, B., & Schmitt-Kopplin, P. (2013). High-field NMR spectroscopy and FTICR mass spectrometry: powerful discovery tools for the molecular level characterization of marine dissolved organic matter. Biogeosciences, 10, 1583-1624.

Hertkorn, N., Benner, R., Frommberger, M., Schmitt-Kopplin, P., Witt, M., Kaiser, K., ... & Hedges, J. I. (2006). Characterization of a major refractory component of marine dissolved organic matter. Geochimica et Cosmochimica Acta, 70(12), 2990-3010.

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