DTPA anhydride

Open-chain ligands were the first evaluated for complexation studies with indium and yttrium. The use of diethylenetriaminepentaacetic acid (DTPA) anhydride permitted early evaluation of labeled chelate-conjugates (Figure 2).80 The use of this activated chelating agent was quite popular, until the drawbacks associated with its crosslinking of proteins became apparent. 

To an aliquot of 10-20 mg PL/mL in 0.1 MNaHC03, aliquots of 10% by volume of mixed anhydride of DTPA (50 mg/mL) are added with continuous stirring. For optimal substitution with DTPA, five additions of the anhydride are applied. With each addition of DTPA anhydride, the pH of the reaction is monitored with pH paper, and the pH is maintained above 7.0 without precipitation of the modified polylysine. It appears that when substantial number of lysine residues have been covalently linked with DTPA, the polymers tend to form precipitates, probably because of polymerization by ionic interaction. Lowering the pH iesolublized the precipitate. 

Indium-lU labelling of antibodies using cyclic DTPA anhydride ... 

Cyclic DTPA anhydride (CDTPAA, Sigma-Aldiich Chemical Company)... 

Dissolve cyclic DTPA anhydride in diy DMSO to a concentration of 2-10 mg/ml. 

Some other BFCs overcome both of these disadvantages of the DTPA anhydride (see Figure lb). These have a single reactive group which is situated in the ethylene backbone of the DTPA molecule and thus leave all five carboxylic acid groups free for complexation of the metal (14). The synthesis of these BFCs is however, relatively complex and they are not currently commercially available. 

Indium-lll labelling of antibodies using cyclic DTPA anhydride 221 Reduction-mediated technetium-99m labelling of antibodies with 2-mercaiJtoethanol 226... 

Organic transformations can be used to prepare architectures from stable starting components. We initially used this approach in the first controlled preparation of/-/ heterometallic systems, using stable 4-aminobenzylD03A as building block complexes and reacting them with DTPA anhydride (Fig. 9.10), before adding a second lanthanide ion which binds in the DTPA diamide pocket [54]. 

---