Engineering Magnetic Guanidyl-Functionalized Supramolecular Organic Framework for Efficient Enrichment of Global Phosphopeptides

Comprehensive
mass spectrometry-based proteomics analysis is currently
available but remains challenging, especially for post-translational
modifications of phosphorylated proteins. Herein, multifunctional
magnetic pillar[5]­arene supramolecular organic frameworks were fabricated
and immobilized with arginine (mP5SOF-Arg) for highly effective enrichment
of global phosphopeptides. The specific phosphate-P5/phosphate-guanidine
affinities and large surface area with regular porosity contribute
to the high enrichment capacity. By coupling with mass spectrometry,
high detection sensitivity (0.1 fmol), excellent selectivity (1:5000
molar ratios of β-casein/cytochrome c), and
high recyclability (seven cycles) were achieved for phosphopeptide
analysis. mP5SOF-Arg can efficiently enrich phosphopeptides from practical
samples, including defatted milk, egg yolk, and human saliva. Notably,
a total of 450 phosphopeptides were explored for highly selective
identification from A594 cells and 1445 phosphopeptides were identified
from mouse liver tissue samples. mP5SOF-Arg exhibited great potential
to serve as the basis for peptidomic research to identify phosphopeptides
and provided insight for biomarker discovery.