Purified IFNα2b is not aggregated and forms dimers at neutral pH independent of intermolecular cystine formation. Following a desalting step in neutral PBS, purified IFNα2b was analysed for dimer formation. A) Twenty mg of purified IFNα2b were analysed on a Superdex 75 HR16/60 column equilibrated with PBS at pH 7,0. The arrows and numbers above indicate the elution volumes of molecular weight standards eluted in the same conditions. Purified IFNα2b elutes in the same volume as ovalbumin, a 44 kDa globular protein. B) Coomassie-stained SDS-PAGE analysis of samples (20 μL) of each of the 10 fractions (4 mL) collected between elution volumes 40–80 mL. C) Coomassie-stained SDS-PAGE analysis of reduced and non-reduced IFNα2b from HEK293 cells.