Figure 2.

Natalizumab sequence validation based on subunit MWs. (A) MALDI-TOF spectrum obtained without prior chromatographic separation showing M²⁺ molecular ions. (B) Isotopically resolved UHR-QTOF spectrum of the natalizumab Fd (black) overlaid against the theoretical isotope pattern (red) calculated from Seq. S1-A showing a clear shift in the patterns and a 2 Da/78 ppm mass error. (C) The same spectrum (black) was matched against the isotopic pattern calculated from the sequence Seq. S1-B - Wang et al. 2009; red- established by MALDI-ISD providing a good match and 0.83 ppm mass accuracy.²⁴.