Identification of isolated ATI tetramers. SDS-PAGE of ATI tetramer isolates in the presence of 2% (m/v) dithiothreitol. (1) Molecular weight standard, (2) Commercial Sigma ATI control, containing mainly monomeric and dimeric ATI 0.19, 0.28, and 0.53 [14], and (3) ATI tetramer isolate. Size-exclusion chromatogram of ATI tetramer isolate (line) and Sigma ATI (broken line). Elution volume of molecular standard bovine serum albumin 66 kDa (8.6 mL), chymotrypsinogen 25.6 kDa (9.9 mL), and lysozyme 14 kDa (11.4 mL). As determined by mass spectrometry, Band 1 consists of the ATI tetramer CM3 subunit and Band 2 of the ATI tetramer CM2 subunit.