Development of Gd 3+ -immobilized glutathione-coated magnetic nanoparticles for highly selective enrichment of phosphopeptides.

In this study, we designed a gadolinium-based immobilized metal ion affinity chromatography material for the selective enrichment of phosphopeptides. Gadolinium ion was immobilized on the surface of glutathione-coated magnetic nanoparticles through a facile and effective synthetic route. The adsorbent integrated the advantages of superparamagnetism of Fe3 O4 core, good biological compatibility of glutathione, and strong interaction between gadolinium ion and phosphopeptides. It was employed to enrich phosphopeptides from standard protein digests coupled with MALDI-TOF MS. Results demonstrated that the adsorbent possessed high selectivity for phosphopeptides, good reusability and reproducibility. Moreover, the material provided selective enrichment of phosphopeptides from real samples including non-fat milk digests and human serum. The developed method exhibited high sensitivity (detection limit of 10 fmol), showing great potential in the detection of low-abundance phosphopeptides in biological samples.