IMAC purification of scFv7F9Cys–PEG20K. A nickel affinity column was used. ScFv7F9Cys contains a poly-histidine tag which will bind the nickel on the column. Any bound protein was eluted using imidazole increasing in concentration over 6 steps (0, 5, 10, 15, 20, and 100%). A. Chromatogram of purification: solid line shows UV280 peaks, and dashed line shows the percent of imidazole. B. SDS-PAGE analysis of fractions from IMAC purification. Bars 1, 2, and 3, correspond to fractions analyzed from same section of the chromatogram. C. SDS-PAGE analysis of scFv7F9Cys-PEG40K IMAC purification.