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. Author manuscript; available in PMC: 2013 Aug 1.
Published in final edited form as: Peptides. 2012 May 15;36(2):251–256. doi: 10.1016/j.peptides.2012.05.003

Figure 2. Mass spectra confirm that the chemical form of the recombinant human insulin from Drosophila is authentic.

Figure 2

(A) Intact r-hINS (z=5) before reduction/alkylation. (B) r-hINS chain A (z=2) after reduction/alkylation (C, D) r-hINS chain B (z=5 and 4) after reduction/alkylation. The naturally occuring isotopic distributions found in these peptides results in multiple MS peaks for each peptide with an interval of 1/ z (charge) along the m/z axis. The measured peptide masses match expected masses at 200 ppm mass accuracy. (E) Tandem MS spectra of r-hINS chain B after reduction/alkylation (m/z 709.27, z=5), with the precursor ion mass-matching the expected peptide within 110 ppm, and assigned ions matching expected fragments within 0.3 Da. X=CH2CONH2. Here, peptide is mainly cleaved at peptide bonds (C-N bonds) with the formation of b and y ions, and the positions of cleavage have been indicated in the peptide sequence.