Figure 5

Mass spectrum of TBDMS₃-alanine derived by electron impact ionization in GC-MS analysis: Naturally labeled alanine with a mass isotopomer distribution resulting from the nautrally occurring isotopes (A), alanine from the cell protein of S. cerevisiae cultivated on [1-¹³C] glucose (B), alanine from the cell protein of lysine producing C. glutamium cultivated on [1-¹³C] glucose (C). The monoisotopic mass of the molecular ion, which itself is not detected, is 317. The structures of valuable ion clusters for labeling analysis in metabolic flux studies (m/z 260, m/z 232) are additionally.