Protein fractionation analysis of scFv. (A): 12% SDS-PAGE of the gel was stained with 0.25% Coomassie Brilliant Blue R-250. (B): Western blot. A fusion protein was probed with mouse anti-His Ab, followed by goat anti-mouse alkaline phosphatase conjugated Ab. Color was developed by using NBT/BCIP alkaline phosphatase substrate. Lane M, protein molecular weight marker; lane 1, total cells sample (without IPTG induction); lane 2, total cells sample (under IPTG induction) ; lane 3, culture supernatant; lane 4, insoluble fraction; lane 5, soluble fraction. The scFv (27 kD) is denoted by an arrow.