Fig. 8.

Assessment of the molecular mass of the RAIDD-DD (E188K):PIDD-DD complex in solution by (a) SEC-MALS and (b) nanoESI-MS. In (a), the overall protein loading concentration was 1.5 mg/mL (magenta), 12 mg/mL (blue) and 24 mg/mL (red). In (b), mass spectrum of 15 μM complex in 50 mM ammonium acetate buffer (pH 7.8) and ion series corresponding to the major RAIDD-DD:PIDD-DD species with 5:5 stoichiometry are labeled with charge states, indicated with blue circles. The presence of a low concentration consistent with 5:4 stoichiometry is indicated (green stars).