<p>Nature Chemical Biology, Published online: 18 March 2026; <a href="https://www.nature.com/articles/s41589-026-02176-3">doi:10.1038/s41589-026-02176-3</a></p>Proteins are promising ligands for selective metal capture, but low-throughput assays limit their discovery and design. Now, a high-throughput platform for quantifying the rare earth selectivity of lanmodulin (LanM) proteins has been developed. The SpyCI-LAMBS platform enabled the identification of a set of LanMs capable of separating light rare-earth elements in a single step.