Reagent of the Preparation for Water-Soluble Labels

Sodium 2,3,5,6-tetrafluoro-4-hydroxybenzenesulfonate (1) is a water-soluble active ester synthetic reagent developed by Gee and co-workers. It can convert hydrophobic labeling reagents with carboxyl groups to water-soluble reactive esters under mild conditions.¹⁾ For instance, Suzuki and co-workers synthesized a water-soluble reactive ester (3) from an Hydrophobic fluorescent probe (2) with carboxyl groups by using 1. Amino groups of bovine serum albumin were labeled with 3 in aqueous media.²⁾ For labeling of biomolecules, 1 is a useful reagent to increase water solubility of hydrophobic labels.