Fig. 4. Influence of structural features on ECD fragmentation of F(ab′)2 from the four subclasses of IgGs (anti-CD20). (A) Structures of F(ab′)2 comparatively modelled against available structures of IgG subclasses, IgG1: ; 1HZH, IgG2: ; 1IGT, IgG3: ; 5A16, IgG4: ; 5DK3. The disulfide bridges are displayed as paired yellow spheres. (B and C) The number of disulfide bonds that span each sequence position of (B) the LC and (C) the HC in different subclasses of IgG anti-CD20 overlaid with detected ECD fragments. (D) Fractions of ECD fragment ion intensities originating from the LC or HC for the different subclasses of IgG anti-CD20. (E) Fractions of the 500 most compact conformations of each subclass in which either the LC or HC is most solvent-exposed following collapse.31 See Fig. S7† for a more detailed description of the estimated chain relative exposure based on center-of-mass calculations. (F) Sampling of Fab arm movements displayed as spheres representing the center-of-mass of (purple) LCs and (red) HCs, showing remarkable differences in between the different subclasses.
