Quantification of phosphoproteins with global internal standard technology

Area of Science:

• Biochemistry
• Proteomics
• Analytical Chemistry

Background:

• Accurate quantification of protein variants is crucial in proteomics.
• Post-translational modifications like phosphorylation significantly impact protein function.
• Existing methods for phosphopeptide quantification have limitations.

Purpose of the Study:

• To develop and validate Global Internal Standard Technology (GIST) for quantifying phosphopeptides.
• To analyze serine and threonine phosphorylation in protein samples.
• To establish a robust method for comparative phosphoproteomics.

Main Methods:

• Proteins were digested into peptides.
• Peptides were derivatized with isotopically coded reagents (light/heavy).
• Phosphopeptides were enriched using Ga(III) immobilized metal affinity chromatography (IMAC).
• Peptides were analyzed by reversed-phase chromatography (RPC) and mass spectrometry (MS).

Main Results:

• Relative phosphopeptide concentrations were determined by measuring isotope ratios in MS.
• The GIST method demonstrated accurate quantification with model peptides.
• The approach allows for the analysis of phosphorylation at the proteome level.

Conclusions:

• GIST provides a reliable method for quantifying phosphopeptides.
• This technology facilitates comparative analysis of phosphorylation across samples.
• GIST holds promise for comprehensive proteome-wide analysis of protein variants.