Traditional hydrophobic biotinylation reagents used for conjugating biotin to the free amines of biomolecules include biotin alone, with or without activation of the carboxylic acid, biocytin (biotin bound to lysine), and biotin conjugated to aminocaproic acid (most frequently represented by the abbreviation “LC”). The active ester known as Sulfo-NHS is used to make these hydrophobic compounds somewhat water soluble. The non-sulfonated NHS esters are not water soluble at all.
