Fab Fragment Monovalent Antibodies

    These reagents are prepared from stocks of our highest affinity antibodies by special papain digestion and subsequent purification to yield the approximately 50 kDa monovalent Fab antibody portion of the molecule. Fab antibody reagents are then coupled to reporter molecules. These reagents lack the F(c) portion of the molecule and will not interact with either in-vitro or cellular F (c) binding mechanisms. The relative low molecular weight of these reagents maximizes permeability for in-situ studies.


Fab fragment antibodies are useful in experiments where two primary antibodies from the same host species are used, such as two IgG-type mouse monoclonal antibodies, as an example, Cell Signaling or Phospho Specific Antibodies. A conjugated Fab fragment anti-Mouse IgG is applied which binds to the surface of the mouse IgG antibody molecule completely masking all sites for anti-Mouse IgG binding. In addition, the Fab fragment antibody, because of its monovalent properties, is not able to bind any additional Mouse IgG antibody if it were to be reintroduced into the system. At this point the second primary antibody, also Mouse IgG, is applied and subsequently detected with a second conjugated anti-Mouse IgG. Again, the masking properties of the conjugated Fab fragment antibody used to bind the first primary antibody shield the first Mouse IgG from detection by the second anti-Mouse antibody.


Please inquire for other reporter molecule conjugates, such as, DyLight and IRDye or for Fab fragments of any other antibody listed in our catalog. Note: Anti-IgG F(ab?)2 antibodies will recognize the Fab and F(ab')2 portions of the IgG molecule equally well.