Specificity of sdAbs selected on cell surface antigens by homogeneous time resolved fluorescence (HTRF) technology.
A, Analysis of anti-HER2 sdAbs. Cells transfected by SNAP-tag HER2 and labeled with donor fluorophore were incubated with sdAbs and acceptor-labeled anti-6his mAb. sdAb binding, detected by FRET, is expressed as HTRF ratio to normalize results for the HER2 receptor density (see Materials and Methods). Anti-Fc: anti human Fc sdAb used as negative control. B, Analysis of anti-mGluR4 sdAbs. (sdAb binding was followed as described in A). C, Analysis of anti-CXCR4 sdAbs (sdAb binding was followed as described in A).