Thiol detection, derivatization and tagging at micromole to nanomole levels using propiolates

Thiols, simple and complex, including polypeptide and protein thiols, react rapidly and selectively with esters of propiolic acid under very mild conditions (aqueous buffer, room temperature, pH 7) to give thioacrylates. These stable derivatives exhibit strong, characteristic ultraviolet spectra, maximal at 280–290 nm, molar absorbance ca 12,500. In a single, simple experiment the thiol is detected, its amount is estimated, it is stabilized against oxidation and disulfide scrambling, it is converted into a derivative amenable to isolation and structure elucidation procedures, and it is tagged with recognizable ultraviolet and NMR characteristics generated de novo. The reagents are stable and inexpensive and the procedures are quick, easy, sensitive and selective.