TABLE 2.

Mass isotopomer distribution in alanine, serine, glutamate, proline, aspartate, and threonine in S. acidocaldarius

The data are from 100% [1-¹³C] and [2-¹³C]xylose experiments.

Fractional label	m0a	m1	m2	m3	m4	m5
100% [1-13C]Xylose
Serine (M-57)+b	0.962c	0.032	0.001	0.002
Serine (M-85)+	0.996	0.006	0.000
Alanine (M-57)+	0.475	0.512	0.011	0.000
Alanine (M-85)+	0.984	0.017	0.000
Glutamate (M-57)+	0.457	0.512	0.023	0.002	0.000	0.000
Glutamate (M-85)+	0.966	0.034	0.000	0.000	0.000
Proline (M-57)+	0.425	0.550	0.020	0.000	0.000	0.000
Proline (M-85)+	0.961	0.035	0.000	0.000	0.000
Aspartate (M-57)+	0.961	0.032	0.002	0.001	0.000
Aspartate (M-85)+	0.988	0.011	0.000	0.002
Threonine (M-57)+	0.959	0.039	0.000	0.001	0.000
Threonine (M-85)+	0.986	0.017	0.000	0.001
100% [2-13C]Xylose
Alanine (M-57)+	0.309	0.659	0.026	0.004
Alanine (M-85)+	0.456	0.536	0.006
Glutamate (M-57)+	0.140	0.711	0.140	0.004	0.000	0.000
Glutamate (M-85)+	0.209	0.776	0.012	0.000	0.000
Proline (M-57)+	0.120	0.755	0.118	0.002	0.000	0.001
Proline (M-85)+	0.216	0.754	0.027	0.000	0.000
Aspartate (M-57)+	0.227	0.735	0.032	0.002	0.000
Aspartate (M-85)+	0.609	0.383	0.004	0.001
Threonine (M-57)+	0.223	0.756	0.015	0.001	0.001
Threonine (M-85)+	0.608	0.385	0.004	0.000

^am₀ is the fractional abundance of the fragments with the lowest mass, and m_i>0 is the abundance of molecules with higher masses.

^b Cracking of the derivatized amino acids leads to the following fragments: (M-57)⁺ with loss of a tert-butyl group; (M-85)⁺, with loss of the CO of the amino acid (C-1 position) and a tert-butyl group. Thus, (M-57)⁺ and (M-85)⁺ correspond to the 1–3, 1–4 or 1–5, and the 2–3, 2–4 or 2–5 fragments, respectively.

^c Abundances are from triplicate experiments and generally with <5% deviation.