Selective Enrichment of Endogenous Serum Phosphopeptides with Ultrafiltration Membrane Intercept-Titanium Dioxide Chromatography Coupled with Nano Ultra-High-Pressure Liquid Chromatography-Quadrupole-Time of Flight Mass Spectrometry

A novel method coupling ultrafiltration membrane with titanium dioxide (TiO2) chromatography was developed to remove large amounts of high-molecular-weight compounds and enrich endogenous serum phosphopeptides. The enriched endogenous serum phosphopeptides were characterized by nano ultra-high-pressure liquid chromatography-quadrupole-flight time mass spectrometry (nano UPLC-Q-TOF MS). Up to 18 endogenous phosphopeptides could be successfully identified from the serum of lung cancer. The established method improved the sensitivity and efficiency of detection of serum phosphopeptides, which might be considered a milestone in tumour biomarker discovery.