Phosphopeptide enrichment using microscale titanium dioxide solid phase extraction.

Area of Science:

• Proteomics
• Analytical Chemistry
• Biochemistry

Background:

• Phosphopeptide identification via mass spectrometry (MS) is difficult due to low abundance and ionization efficiency.
• Existing affinity enrichment methods include immobilized metal affinity chromatography (IMAC).
• Titanium dioxide (TiO2) solid-phase extraction (SPE) offers a potential alternative for phosphopeptide enrichment.

Purpose of the Study:

• To evaluate TiO2 SPE for phosphopeptide enrichment using a 96-well microscale extraction plate.
• To investigate the impact of loading conditions and organic additives on phosphopeptide recovery and selectivity.
• To compare the performance of TiO2 SPE with IMAC.

Main Methods:

• Phosphopeptide enrichment using TiO2 packed in a 96-well plate under vacuum.
• Investigation of various loading conditions and organic additives (e.g., dihydroxybenzoic acid derivatives).
• Comparison of TiO2 SPE with IMAC using yeast lysate digest.

Main Results:

• Organic additives improved enrichment selectivity by reducing acidic, nonphosphorylated peptide binding to TiO2.
• Additives also affected phosphopeptide interaction, leading to reduced recovery.
• TiO2 SPE, particularly with 2,5-dihydroxybenzoic acid, successfully extracted phosphopeptides from yeast lysate, minimizing interference.

Conclusions:

• TiO2 SPE is a viable method for phosphopeptide enrichment.
• Optimizing additive use is crucial for balancing selectivity and recovery.
• This method enhances phosphoproteomic analysis by reducing interference from nonphosphorylated peptides.