Overview of Radionuclide Peptide Conjugation Peptides are widely used as targeting molecules in RDC. Compared to antibodies, peptides are relatively small in size (about 0.5 to 10 kDa) and are comparatively short in vivo circulation times (minutes to hours) with similar binding affinities. Besides, the production and modification of peptides, an effective strategy to improve affinity, selectivity, stability, and pharmacokinetic properties, is easier than that of antibodies. Notably, the biological half-life of peptides ideally matches that of radioactive particles currently used in radiopharmaceuticals.