Titanium dioxide as a chemo-affinity solid phase in offline phosphopeptide chromatography prior to HPLC-MS/MS...

Area of Science:

• Analytical Chemistry
• Biochemistry
• Proteomics

Background:

• Phosphorylated peptides are crucial biomarkers in cellular signaling.
• Selective enrichment of phosphopeptides is essential for mass spectrometry-based proteomics.
• Existing methods often face challenges in efficiency and compatibility with downstream analysis.

Purpose of the Study:

• To develop a new offline chromatographic method for selective phosphopeptide enrichment.
• To ensure compatibility of the enrichment method with online nano electrospray ionization tandem mass spectrometry.
• To optimize sample loading, washing, and elution steps for titanium dioxide (TiO2) based enrichment.

Main Methods:

• Developed a two-dimensional chromatography system utilizing a TiO2-packed pipette tip as an offline first-dimension separation.
• Employed ion-pairing agents (sodium salt of 1-octanesulfonic acid and 2,5-dihydroxybenzoic acid) to enhance selectivity for phosphopeptides.
• Integrated the offline enrichment with online nano reversed-phase high-performance liquid chromatography (HPLC) for tandem mass spectrometry analysis.

Main Results:

• Achieved selective enrichment of phosphorylated peptides using the TiO2-based trapping method.
• Optimized protocols for sample loading, washing, and elution from TiO2 tips.
• Demonstrated improved binding of phosphorylated peptides and blocking of non-phosphorylated peptides through the use of specific agents.

Conclusions:

• The developed offline chromatographic approach provides efficient and selective enrichment of phosphopeptides.
• The method is directly compatible with online nano electrospray ionization tandem mass spectrometry.
• This technique offers a valuable tool for advancing phosphoproteomic studies.