two protein-binding moieties. The DTPA moiety [13] shown in Figure 2 was used instead of the monoamide, because the GdDTPA complex has a more favorable water-exchange rate and the thermodynamically stable GdDTPA core is already present in several clinically approved contrast agents.[14] Human serum albumin (HSA) was chosen as the protein target for proof of principle and MS-325 (Figure 2) was used as a benchmark compound. ...