Preliminary study of the enrichment and fractionation of REEs in a newly discovered REE hyperaccumulator Pronephrium simplex by SEC-ICP-MS and MALDI-TOF/ESI-MS

Abstract

Concentrations of rare earth elements (REEs) were determined in the laminae of 10 species of ferns and their acetone-extractable pigments, as well as their host soil and soil extract, by ICP-MS. A new REE hyperaccumulator, Pronephrium simplex, was discovered which could accumulate REEs up to 1.2 mg g(-1) dry mass under natural growth conditions. Three typical species of ferns chosen were divided into lamina, petiole, stem and root for the study of REE translocation and fractionation. A hyphenated technique, size exclusion HPLC coupled with online UV/ICP-MS, was developed to provide reliable evidence of the existence of REE-binding proteins in the fern's lamina. A new REE-binding protein was discovered and separated from the lamina of natural grown P. simplex. Further characterization of the protein showed that its molecular mass is 5068.4 Da by MALDI-TOF-MS and ESI-MS. Amino acid composition analysis by RP-HPLC indicated that the protein has relatively high contents of proline and glycin.