To a 19 µM sample of DBCO-JVZ007 was delivered 10 equivalents of dansylated azide probe S9 and an appropriate volume of 5 × concentrated reducing buffer (10% SDS, 10 mM 2-mercaptoethanol, 20% glycerol, 200 mM Tris-HCl pH 6.8, 0.05% bromophenol blue). The resulting sample was boiled for 5 minutes prior to analysis via SDS-PAGE, during which time strain-promoted azide-alkyne cycloaddition between the DBCO motif of DBCO-JVZ007 and the azide motif of S9 can be assumed to have reached completion.