Multiplet patterns, isotopomer

A measurement method that is often used to determine the C-labeling of metabolites is 2D [ C. H] correlation nuclear magnetic resonance spectroscopy (COSY). This method yields relative intensities of multiplets in the NMR spectra that correspond to the relative amounts of groups of isotopomers in which the observed atom is C-labeled and the adjacent carbon atoms in the carbon backbone are either C-labeled or not (Szyperski, 1995). If the compound of which the labeling pattern is measured was synthesized by a microorganism growing on a mixture of uniformly C-labeled and naturally labeled carbon substrate, then the relative intensities of NMR fine structures can be calculated from the fractions of molecules that stem from one or more substrate molecule(s) in the feed medium. This is done using so-called probability equations (Szyperski, 1995) that require as input the fraction of uniformly C-labeled medium substrate and the fraction of naturally C-labeled carbon. 

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