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. Author manuscript; available in PMC: 2017 May 1.
Published in final edited form as: Free Radic Biol Med. 2016 Feb 10;94:161–173. doi: 10.1016/j.freeradbiomed.2016.01.020

Table 1.

Potential tryptic and Asp-N peptide and identification of compounds and their molecular mass observed by LC-Q-TOF-MS peptide mapping of Asc/Cu(II) treated bSOD1

Enzyme Potential Peptide Mol Mass Calculated Compound Mol Mass Observed
Trypsin T4-NX G24-T30-amide derivative 688.36 688.37
T4-CY N-α-ketoacyl-G31-K67 3905.77 3905.74
T4-N G24-T30 689.36 689.37
T4-C S32-K67 3849.76 3849.76
T4-CZ isocyanate-S32-K67 3875.75 3875.73
Asp-N D3-NX D25-T30-amide derivative 631.34 631.35
D3-CY N-α-ketoacyl-G31-G39 832.41 832.39
D3-N D25-T30 632.34 632.39
D3-C S32-G39 776.39 776.39
D3-CZ isocyanate-S32-G39 802.40 802.37
X

The C-terminus amino acid of this peptide is an amide derivative

Y

The N-terminus amino acid is a N-α-ketoacyl derivative

Z

The N-terminus amino acid is an isocyanate derivative

Note: T4-NX and T4-N and D3-NX and D3-N were indistinguishable as the molecular mass difference between them is 1 Da which coincides with the difference of 12C and 13C isotope.