Synthesis and Characterization of Mal2Sar-(Exendin-4)2

Mal₂Sar was prepared as previously reported28 (link). Cys⁴⁰-exendin-4 (3.3 mg, 0.8 µmol) was added to phosphate buffer (pH 7.0) containing Mal₂Sar (0.3 mg, 0.36 µmol) (Fig. 1B). The solution was stirred at room temperature and the product was purified by HPLC (Rt: 13.08 min). At a flow rate of 1 mL/min, the mobile phase was maintained at 70% solvent A [0.1% TFA) in water] and 30% B [0.1% TFA in MeCN] from 0-2 min and was changed to 35% solvent A and 65% solvent B through 2-37 min. The product was characterized by LTQ FT mass spectrometry (Thermo, Waltham, MA) (Mal₂Sar-(exendin-4)₂: m/z 9402.64 for [MH]⁺, C₄₁₆H₆₃₀N₁₁₂O₁₃₀S₄, calculated[MH]⁺: 9402.50).