Synthesis and application of cleavable photoactivable heterobifunctional reagents.

Three different cleavable photoactivable heterobifunctional reagents have been synthesized and characterized by proton NMR, 13C NMR, mass spectroscopy, infrared spectroscopy, and thin-layer chromatography. They are the N-hydroxysuccinimide ester of 3-[(4-azidophenyl)dithio]-propionic acid, methyl 3-[(4-azidophenyl)dithio]propionimidate, and N-[(4-azidophenyl)thio]phthalimide. Concanavalin A was coupled with one of the reagents, the N-hydroxysuccinimide ester of 3-[(4-azidophenyl)dithio]propionic acid, and radioiodinated. The [125I]lectin derivative and [125I]lectin showed similar specific binding to the receptors on the human erythrocyte membrane. Upon photolysis, subunits of the [125I]lectin derivative were cross-linked to produce dimer, trimer, and tetramer. These cross-linked complexes were readily cleaved by reducing the disulfide bond of the reagent.