Citrate boosts the performance of phosphopeptide analysis by UPLC-ESI-MS/MS

Area of Science:

• Proteomics
• Analytical Chemistry
• Biochemistry

Background:

• Poor detection efficiency of phosphopeptides in LC-MS/MS is often caused by incomplete recovery from the LC column.
• Metal ions on the stationary phase can interact with phosphopeptides, leading to retention issues via an ion-pairing mechanism similar to immobilized metal ion affinity chromatography (IMAC).

Purpose of the Study:

• To investigate methods for overcoming phosphopeptide suppression during gradient LC-MS/MS analysis.
• To enhance the detection sensitivity and recovery of phosphopeptides, especially multiply phosphorylated ones.

Main Methods:

• Testing additives like phosphate, EDTA, and citrate in the phosphopeptide sample during UPLC-MS/MS analysis.
• Comparing the effectiveness and operational stability of different additives for phosphopeptide analysis.
• Analyzing commercial phosphopeptide mixtures, beta-casein digests, and SETDB1 digests with and without citrate additive.

Main Results:

• Citrate additive was highly effective in increasing phosphopeptide detection sensitivity in UPLC-MS/MS.
• EDTA enhanced sensitivity but caused precipitation, leading to equipment damage.
• Citrate addition enabled the identification of 27 phosphorylation sites in SETDB1, including multiply phosphorylated peptides, compared to 10 sites without citrate.
• Citrate is compatible with stable, long-term routine operation.

Conclusions:

• Citrate is a superior additive for improving phosphopeptide recovery and detection sensitivity in LC-MS/MS.
• The use of citrate extends the scope of phosphopeptide analysis, particularly for multiply phosphorylated peptides.
• Citrate offers a practical solution for enhancing phosphoproteomic studies using LC-MS/MS.