Biotin may be conjugated to many proteins while maintaining the biological activity. The biotinylated probe is usually detected by avidin, streptavidin due to their effective binding which is used in various applications such as affinity chromatography, ELISA and Western Blot, fluorescence-activated cell sorting (FACS), intracellular labeling.
Biotin-XX-NHS ester is a derivative with long spacer to reduce steric effect when binding amino acids, peptides, or proteins by reacting with primary amines. This compound is used to attach biotin to primary amines under alkaline conditions (pH 8-9).