Development of lanthanide-labeled human INSL3 as an alternative probe to radioactively labeled INSL3 for use in bioassays.

The use of radioisotope-labeled peptides and proteins in bioassays is diminishing as a consequence of the emergence of fluorescent lanthanide-labeled probes. We describe a simple, single-step labeling of synthetic human insulin-like peptide 3 (INSL3) with a commercially available activated europium chelator. The labeled peptide was then used for the development of a robust and highly reproducible receptor-binding assay which is amenable to automated high-throughput screening of ligands. Europium-labeled INSL3 showed a similar binding profile to radioactively labeled INSL3.