Fig. 2.

Averaged MS-spectra of one peptide from the benzene-1,2 dioxygenase ferredoxin-NAD(+) reductase subunit protein (P. putida KT2440) measured by nano-LC LTQ Orbitrap-MS to demonstrate the differential isotopic pattern of ¹²C peptides and ¹³C-labeled peptides during the incorporation of different substrate ratios. The measured peptide with the sequence GIFAVGDVATWPLHSGGK has a mass charge of +2 and is also listed in supplemental Table 1. At all substrate ratios, the isotopomers changed from the natural monoisotopic mass of 906.476 (A) because of the incorporation of heavy isotopes. The highest ¹³C peak in the 10 atom % labeling experiment (B) with [MH+H]⁺² was 909.48621. The highest ¹³C peak in the 25 atom % labeling experiment (C) with [MH+H]⁺² was 915.00487. C, The highest ¹³C peak in the 25 atom % labeling experiment was [MH+H]⁺² 915.00487. D, the highest ¹³C peak in the 50 atom % labeling experiment was [MH+H]⁺² 927.04526. E, the highest ¹³C peak in the 100 atom % ¹³C labeling experiment was [MH+H]⁺² 947.61397.