Extended Data Fig. 11: Stoichiometric characterization of Ancα/β containing historical substitutions.

a, SEC of Ancα/β5. Circles show stoichiometry associated with each peak’s elution volume. b, High-resolution accuracy mass spectrometry (HRA-MS) of Ancα/β5 + α. Purple circles, peaks associated with Ancα/β5; pink, Ancα. c, HRA-MS of tetramer-containing SEC fraction of Ancα/β4 + Ancα. d, HRA-MS of monomer-containing SEC fraction of Ancα/β4 + Ancα. *922 m/z calibration reference standard. e, HRA-MS of Ancα/β9 + Ancα. f, nMS of tetramer-containing SEC fraction of Ancα/β4 + Ancα (Fig. 3a, b). Black circle, most abundant peak used for tandem MS. g, Tandem MS of isolated most-abundant peak in f, showing trimer-containing peaks. Charge states and number of haems (h) in the 8+ peak are indicated. h, Monomer-containing (M) peaks. i–k, nMS (i) and tandem MS (j, k) of Ancα/β14 + Ancα (Fig. 3f) as in f–h. l–n, nMS and tandem MS of Ancα/β5 + Ancα (Fig. 3c, d) as in f–h. Black dots in n mark charge species produced by cleavage of Ancα/β5. All experiments were performed once.