Figure 1.

Illustration of the mass isotopomer distribution vector (MDV) of a three carbon compound, e.g. alanine. The signals with the grey background, the MDV, comprise the fractions of completely unlabeled (M+0), singly labeled (M+1), doubly labeled (M+2), and completely labeled (M+numC in general, i.e. M+3 in this example) analyte. The preceding (M-n) and following (M+numC+n) masses, which form a boundary around the analyte masses, are indicated.