Efficient extraction of low-abundance peptides from digested proteins and simultaneous exclusion of large-sized proteins with novel hydrophilic magnetic zeolitic imidazolate frameworks.

Zeolitic imidazolate frameworks (ZIFs) are composed of tetrahedral transition metal ions and imidazolate type organic linkers. This kind of metal organic frameworks (MOFs) combines the unique properties of both zeolites and MOFs. Furthermore, ZIFs can be assembled under mild biocompatible conditions. These advantages make them be primarily studied for biochemical analysis. In this work, polydopamine-modified hydrophilic magnetic ZIFs were synthesized in a simple and mild way for the efficient extraction of low-abundance peptides. Thanks to the low-coordinated Zn2+ ions, the Fe3 O4 @PDA@ZIF-8 composites showed strong affinity towards low-abundance peptides, especially those with histidine residues. After enrichment, the sequence coverage of BSA and HSA tryptic digest got a significant increase. The solid phase method based on the magnetic ZIFs exhibited size-exclusion effect towards large-sized proteins, and proved to be effective even under the 200-fold dilution with BSA protein solution.