N-[6-(Biotinamido)hexyl]-3’-(2’-pyridyldithio)-propionamide(Biotin-HPDP) is a sulfhydryl reactive biotinylation reagent with a long chain,cleavable spacer arm. Biotin-HPDP biotinylation occurs between pH 6-9 throughits pyridyldithiol group reacting with sulfhydryls to form a stable disulfidebond. The 29.2 angstrom spacer arm prevents steric hindrance and may also becleaved at the disulfide bond using TCEP-HCl, DTT or ß-Mercaptoethanol.Biotin-HPDP must be dissolved in an organic solvent, such as DMSO or DMF, thenadded to an aqueous biotinylation reaction. The resulting biotinylated proteincan then be detected when used in conjunction with streptavidin or ImmobilizedStreptavidin.