Synthesis of anxA5-DTPA 6. 1) Excess of cyclic DTPA anhydride 1 was reacte d with N-(2-aminoethyl) maleimide trifluoroacetate 2 in half-saturated sodium bicabonate solution. 2) Reaction product 4 was regiospecifically coupled with the thiol group of cys-anxA5, 5. Due to complete hydrolysis of excess anhydride 1 during a 2-h reaction, the reaction solution from the first step could be used directly without purification. The conjugate 6 was purified by gel filtration.