In Vitro: Biotin-C2-maleimide can act bioconjugation with 5 eq. SUMO-1 probes. 1. Biotin C2 maleimide (ATT Bioquest, dissolved in DMSO) is performed in Tris buffer (50 mM Tris, 300 mM NaCl; pH 7.0) after 15 min reduction with Tris (2-carboxyethyl)phosphine (TCEP, 120 μM) at room temperature. 2. After 1 h incubation, the unreacted Biotin is separated by Ni-NTA affinity chromatography followed by dialysis against PBS buffer (pH 7.4).