Layer-by-layer assembled magnetic bimetallic metal-organic framework composite for global phosphopeptide enrichment

The highly selective enrichment of phosphopeptides is vital for the research of phosphorylated proteomics. Herein, a magnetic bimetallic metal-organic framework (MOF) with Zr-O and Ti-O clusters (denoted as Fe3O4@SiO2@(Zr-Ti-PTA)(15)) has been fabricated using a layer-by-layer assembly approach via the coordination of metal ions with carboxyl groups. The composite has large specific surface area (135.84 m(2)g(-1)) and superparamagnetism (62.03 emu g(-1)). Compared with single-metal cluster MOF, the Fe3O4 @SiO2 @(Zr-Ti-PTA)(15) showed higher binding capacity (100 mgg(-1)), enhanced affinity, better selectivity (n(beta-)(casein) : n(BSA) =1 : 2000) and sensitivity (0.3 fmol/mu L) towards phosphopeptides due to the combination of the dual metal clusters. Furthermore, the Fe3O4@SiO2 @ (Zr-Ti-PTA)is was successfully applied to extracting phosphopeptides from non-fat milk tryptic digest, and 10 monophosphopeptides and 22 multi-phosphopeptides were captured. As a result, 1294 phosphopeptides (476 multi-phosphopeptides and 818 mono-phosphopeptides) were selectively extracted and detected from tryptic digest of rat brain extract, indicating its great application potential in phosphorylated proteomics research. (C) 2019 Elsevier B.V. All rights reserved.