Ferritin heteropolymer production in Rosetta gami B. transformed with the pWUR-FTH-tetO-FTL plasmid. 7.5% native-PAGE and 12% SDS–PAGE of homopolymer H- and L-ferritin (1 μg) used as a reference (labeled H and L on top of each gel), and different ferritin samples induced with indicated IPTG and Tet concentrations (4 hrs induction time). Cell cultures of 20 mL (A, B), 200 mL (C, D) and 1000 mL (E, F) are displayed. Gels were stained with Coomassie blue. All preparations were performed in LB media from Teknova.