Do I Use Streptavidin or Goat anti-Biotin?
For the indirect detection of a biotinylated primary antibody or nucleic acid probe there is a choice of Streptavidin or Goat anti-Biotin gold conjugates. Historically, Streptavidin has been the most frequently used detector for biotin because of the very high affinity constant between them. Most recently, however, Goat anti-Biotin has been shown to be a rather more sensitive detector of biotin compared to Streptavidin when conjugated to gold particles. This is because of the relatively large molecule size of the antibiotin molecule (160,000 Daltons) compared to Streptavidin (40,000 Daltons) and the distance between the binding of the gold on the Fc, from binding region of the antibody F(ab’). This is especially so when using larger gold particles but becomes insignificant for 5nm and 1nm gold conjugates. On occasions where background from non-specific attraction of goat antibodies may cause a problem, Streptavidin may provide a cleaner result. We recommend beginning with a Goat anti-B
