Hydroxyapatite as a concentrating probe for phosphoproteomic analyses.

Area of Science:

• Biochemistry
• Analytical Chemistry
• Proteomics

Background:

• Phosphoproteomics is crucial for understanding cellular signaling.
• Selective enrichment of phosphoproteins/phosphopeptides (CPP) from complex biological matrices remains challenging.
• Existing methods often lack efficiency or require extensive sample preparation.

Purpose of the Study:

• To develop a novel, efficient method for selective enrichment of CPP from complex mixtures.
• To utilize ceramic hydroxyapatite (HA) as a solid-phase adsorbent for CPP capture.
• To validate the method using casein and eggshell phosphoproteins for mass spectrometry analysis.

Main Methods:

• Employed ceramic hydroxyapatite (HA) for selective capture of CPP.
• Performed in situ enzymatic digestion with trypsin on HA-bound casein.
• Utilized matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF) and LC-ESI-MS/MS for analysis.
• Applied alkaline phosphatase (AP)-assisted de-phosphorylation for phosphorylation level calculation.

Main Results:

• Successfully identified 32 casein CPP using the HA-based method.
• Achieved efficient isolation and detection of CPP directly from well plates.
• Demonstrated ~70% recovery of phosphoproteins from eggshell samples, identifying 5 phosphoproteins and 14 phosphopeptides.
• The analytical process required approximately 2 hours per sample.

Conclusions:

• The developed HA-based method provides a rapid and efficient approach for selective enrichment and analysis of CPP.
• This technique is effective for both model phosphoproteins (casein) and complex biological samples (eggshells).
• The method facilitates accurate identification and quantification of phosphoproteins and phosphopeptides, advancing phosphoproteomics research.