Direct detection of scFv binding by using the alkaline phosphatase fusion partner. A. Direct detection in western-blot using scFv-AP expressed from pSANG14-3F. Recombinant human desmin directly detected with scFv-AP from bacterial cell extract diluted 1:5 using NBT/BCIP. B: Direct detection of collagen VI in immunohistochemical staining of acetone-fixed frozen mouse bladder using 0.2 μg/ml scFv-AP detected by NBT/BCIP (upper panel). The lower panel shows the same tissue incubated with NBT/BCIP in the absence of an scFv-AP.