Figure 6.

Concomitant N-terminal c-ions and bridged z-ions produced in the native top-down ECD spectra of the anti-CD20 IgA1 Fab precursor, revealing that the inter- and intrachain disulfide bonds remain intact. (A) Most c-ions (< m/z 3500, red) are well separated in the m/z window from their concomitant bridged z-ions (> m/z 3500, blue) which overlap with the charged reduced precursors in the native ECD-MS spectrum of the IgA1 anti-CD20 Fab molecule. The purple regions correspond to the spectral region with overlapping c-ions and bridged z-ions. (B) Alignment of the c- and z-ion pairs, in red and blue, respectively, after charge deconvolution, reveals that their summed-up masses precisely add up to that of the intact 48618 Da Fab precursor for each detected (c, bridged z) ion pair.