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NMR Spectrum and 13C Label

I need some help with this challenging question:
13C-NMR spectroscopy was used to detect (13)C-label accumulation in cerebral metabolites following the intravenous infusion of [1,6-(13)C]-glucose (Glc). The (1)H- [(13)C]-NMR method yielded high-quality (1)H-[(13)C]-NMR spectra. As a result, the (13)C labeling of [4-(13)C]-glutamate (Glu) and [4-(13)C]-glutamine (Gln) could be detected. The formation of [n-(13)C]-Glu, [n-(13)C]-Gln (n = 2 or 3), [2-(13)C]-aspartate
(Asp), [3-(13)C]-Asp, [3-(13)C]-alanine (Ala), and [3-(13)C]-lactate (Lac) was also
observed to be reproducible. For 2 of the above metabolites (your choice), show by means of tracing the path of the 13C label, that the NMR results are biochemically plausible.

Reference for this Problem: (Magn. Reson. Med., 49(1):37-46, 2003 - available online as a tool. I found this to help explain NMR spec).

Solution Preview

13C-NMR spectroscopy was used to detect (13)C-label accumulation in cerebral
metabolites following the intravenous infusion of [1,6-(13)C]-glucose (Glc).

The (1)H- [(13)C]-NMR method yielded high-quality (1)H-[(13)C]-NMR spectra. As a result, the (13)C labeling of [4-(13)C]-glutamate (Glu) and [4-(13)C]-glutamine (Gln) could be detected.

The formation of [n-(13)C]-Glu, [n-(13)C]-Gln (n = 2 or 3), [2-(13)C]-aspartate
(Asp), [3-(13)C]-Asp, [3-(13)C]-alanine (Ala), and [3-(13)C]-lactate (Lac) was also
observed to be reproducible.

For 2 of the above metabolites (your choice), show by means of tracing the path of the 13C label, that the NMR results are biochemically plausible.

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Response:

First of all, this question is a lot simpler than it looks. All the nmr mumbo-jumbo is not all that relevant. The real issue is the labelling and tracing of labelled carbons. That's what's relevant. Therefore, that's all we focus on, okay?

Let's start with a simple one.

How to go from glucose to ...

Solution Summary

This in-depth solution explains the transformation of glucose to alanine and glucose to lactate through the labeling of 13C in cerebral metabolites. All steps are clearly explained.

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