Biotin HPDP (CAS 129179-83-5)

Biotin HPDP (N-[6-(Biotinamido)hexyl]-3′-(2′-pyridyldithio)propionamide) is a very useful biotinylating reagent that reacts specifically with thiol groups. Many Biotin derivatives react with primary amine groups and consequently can interfere with antigen binding. Biotin HPDP is reactive towards sulfhydryls, and by reducing the immunoglobulin under mild conditions, biotinylation can be isolated to the hinge region. This approach preserves the antigen binding site of the immunoglobulin. Biotin/Avidin binding is reported to have a 9 Å distance and is subject to steric hinderance when the biotin binding site is near certain amino acids or glycosylation sites. Antigen binding capabilities are improved by using a Biotin derivative that has an extended spacer arm, thus reducing steric hindrance. Biotin HPDP has a spacer arm to give a span of 29.2 Å between the reacted sulfhydryl and the attached Biotin group. When using traditional amine reactive biotinylation reagents such as NHS-SS-Biotin, each original reacted -NH2 group will be changed to a -NH2-(CH2)2-SH residue, and the original protein (or peptide) can not be regenerated after cleavage from Biotin. This is where Biotin HPDP truly shines. A unique advantage of Biotin HPDP is the Biotin can be cleaved away completely and the original protein (or peptide) can be regenerated to its original form.