MIDcor, an R-program for deciphering mass interferences in mass spectra of metabolites enriched in stable isotopes

Table 7 Accounting for the isotopic effect in data correction for C2-C4 and C2-C5 fragments of glutamine using the factor of 0.6 for the labeled isotopomers

¹³C-labeling	m0	m1	m2	m3	m4	fragment
natural	1	0	0	0	0	C2C4
natural	1	0	0	0	0	C2C5
3-¹³C-Gln	0.008	0.986	0.0	0.005	0	C2C4
3-¹³C-Gln	0.005	0.9895	0.001	0.003	0.001	C2C5
U-¹³C-Gln	0.004	0.005	0.018	0.973	0	C2C4
U-¹³C-Gln	0.003	0.003	0.01	0.022	0.959	C2C5
n:3:U_90:2:8	0.889	0.020	0.002	0.089	0	C2C4
n:3:U_90:2:8	0.888	0.021	0.001	0.002	0.088	C2C5
n:3:U_40:30:30	0.437	0.277	0.006	0.280	0	C2C4
n:3:U_40:30:30	0.436	0.277	0.003	0.007	0.276	C2C5
n:3:U_95:2:3	0.940	0.026	0.001	0.032	0.0	C2C4
n:3:U_95:2:3	0.940	0.027	0.0	0.001	0.032	C2C5

The calculated artificial labeling of naturally or artificially ¹³C labeled C2–C4 and C2–C5 fragments of glutamine was obtained by applying the algorithm modified to account for the isotopic effect. The samples were prepared either from unlabeled glutamine (natural), ¹³C- glutamine labeled at position 3 (3-¹³C-Gln), uniformly labeled glutamine (U-¹³C-Gln), or various ratios of these samples: natural : 3-¹³C-Gln : U-¹³C-Gln (n:3:U) as indicated