FIGURE 8.

MS² analysis of the hinge peptide derivatives H12a, -d, and -e from Lys-C and Asp-N peptide maps. A, H12a, hinge peptide (2,837.3 Da) comprising sulfonic acid-oxidized Cys²³¹ (²²⁸THTC²³¹(–SO₃H)PPCAPELLGGPSVFLFPPKPK). B, H12e-1, hinge peptide (2,893.8 Da) with a +45-Da adduct (–COOH) at the Thr²²⁸ residue of ²²⁸THTCPPCAPELLGGPSVFLFPPKPK. C, H12d, hinge peptide (2,679.9 Da) with a +71-Da adduct at the Thr²³⁰ residue of ²³⁰TCPPCAPELLGGPSVFLFPPKPK. D, peptide ²²⁵CDKTHTCPPCAPELLGGPSVFLFPPKPK (3,241 Da) from the Asp-N peptide map with Cys²²⁵–SO₃H and ∼RC=O rather than ∼RNH₂ at the N terminus. Some ions were always present in each figure, such as y5, y6, y8, y13, y14, y15, y17, and y19, and thus these peaks were only labeled in Fig. 6A and were not labeled in the following figures.