A lanmodulin-based fluorescent assay for the rapid and sensitive detection of rare earth elements

Sensitive and rapid detection methods for rare earth elements (REEs), including lanthanides (Lns), will facilitate the mining and recovery of these elements. Here, we innovated a rapid, highly selective and sensitive fluorescence detection method for Lns, based on Hans-Lanmodulin, a newly discovered protein with high selectivity and binding affinity for rare earth elements. By labelling the fluorescein moiety FITC onto Hans-Lanmodulin, named as FITC-Hans-LanM. When rare earth ions are present in solution, FITC-Hans-LanM will specifically bind rare earth ions undergoing a conformational change from a disordered state to a dimer, in which the FITC molecules come close to each other, resulting in decreasing fluorescence intensity or even quenching. The assay was responsive to light, medium and heavy rare earth ions. The fluorescence signal has a good linear relationship with Nd³⁺ concentration in the range of 1-20 nM. The detection limit of the method was 0.512 nM, within 1 min. This method could become a useful technique for the detection and quantification of rare earth elements in environmental and industrial samples.