The use of sulfosuccinimidyl-2-(p-azidosalicylamido)-1,3′-dithiopropionate as a crosslinking reagent to identify cell surface receptors

Conditions for solubilizing and iodinating the heterobifunctional thiol-cleavable photoreactive crosslinking reagent sulfosuccinimidyl-2-(p-azidosalicylamido)-1,3′-dithiopropionate which leave the ester moiety, disulfide bond, and azido group reactive are described. Iodination was performed in a mixture of dimethyl sulfoxide and bicarbonate, pH 9.0 (1:20, v v), as solubilizing agent and Iodogen as oxidant. The lectin phytohemagglutinin was derivatized with the iodinated crosslinker and the interaction between phytohemagglutinin and mononuclear cells was chosen as the model system to monitor the efficiency of sulfosuccinimidyl-2-(p-azidosalicylamido)-1,3′-dithiopropionate as a crosslinking reagent. Transfer of ¹²⁵I to the biologically significant T11 lymphocyte receptor in addition to ¹²⁵I labeling of other membrane proteins to which the lectin binds was detected by polyacrylamide gel electrophoresis under reducing conditions.