PM Q-probe: A fluorescent binding protein that converts many antibodies to a fluorescent biosensor.

Quenchbody (Q-body) is a fluorescent biosensor in which a fluorescent dye is tagged near the antigen binding site of an antibody. The fluorescence of the dye is quenched by the tryptophan residues present in the variable region of the antibody, and is recovered when the antigen binds. Q-bodies have been prepared using recombinant DNA technology by introducing one or more tag sequence(s) at either the N-terminal of the Fab or the single chain variable region fragment of the antibody, and labeling the tag with a fluorescent dye.