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Post-synthesis of a titanium-rich magnetic COF nanocomposite with flexible branched polymers for efficient enrichment of phosphopeptides from human saliva and serum.

Luyan MengBing WangBaichun WangQuanshou FengSijia ZhangZi XiongShun ZhangTing CaiChuan-Fan DingChuan-Fan Ding
Published in: The Analyst (2023)
A Ti 4+ -functionalized magnetic covalent organic framework material with flexible branched polymers (mCOF@ε-PL@THBA-Ti 4+ ) built via an immobilized metal ion affinity chromatography (IMAC) enrichment strategy was proposed through post-synthesis modification. Hydrophilic ε-poly-L-lysine (ε-PL) rich in amino active groups was first introduced in the fabrication of the phosphopeptide enrichment material to increase the hydrophilicity while providing more functional modification pathways of the material. 2,3,4-Trihydroxy-benzaldehyde (THBA) provides abundant binding sites for the immobilization of numerous Ti 4+ , which is advantageous for the subsequent efficient phosphopeptide enrichment. The magnetic nanocomposite exhibited outstanding performance of phosphopeptide enrichment with good selectivity (1 : 5000), a low detection limit (2 fmol), and relatively high loading capacity (66.7 mg g -1 ). What's more, after treatment with mCOF@ε-PL@THBA-Ti 4+ , 16 endogenous phosphopeptides from fresh saliva of healthy people were recognized by MALDI-TOF MS, and 50 phosphopeptides belonging to 35 phosphoproteins from the serum of uremia patients were detected by nano-LC-MS/MS. Proteomics data analysis for the differential protein selection between uremia and normal controls was conducted using R software, and four down-regulated and three up-regulated proteins were obtained. The results suggested that the prepared material has potential applications in biomarker discovery.
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