Biotin-SP is our trade name for biotin with a long spacer, which is positioned between biotin and the protein to which it is conjugated. When Biotin-SP-conjugated antibodies are used in enzyme immunoassays, there is a significant increase in sensitivity compared to biotinylated antibodies without a spacer. This is especially notable when Biotin-SP-conjugated antibodies are used with alkaline phosphatase-conjugated streptavidin. Apparently, the long spacer extends the biotin moiety away from the protein surface, reducing steric hindrance.

Biotinylated antibodies require an additional reagent for visualization. We offer streptavidin and Mouse Anti-Biotin conjugated to a variety of probes.