Gas-phase intermolecular phosphate transfer within a phosphohistidine phosphopeptide dimer

Area of Science:

• Biochemistry
• Analytical Chemistry
• Mass Spectrometry

Background:

• Hydrogen bonds and electrostatic interactions influence peptide dissociation pathways under collision-induced dissociation (CID).
• Understanding phosphoramidate peptides (phosphohistidine, phospholysine, phosphoarginine) in tandem mass spectrometry is crucial.
• These peptides present challenges in mass spectrometry analysis.

Purpose of the Study:

• To investigate the behavior of phosphoramidate-containing peptides during low-energy CID.
• To elucidate the dissociation pathways of phosphohistidine (pHis) and phospholysine (pLys) peptides.

Main Methods:

• Analysis of synthetic peptides containing pHis or pLys using Electrospray Ionization Mass Spectrometry (ESI-MS).
• Utilized a Paul-type ion trap (AmaZon, Bruker) and traveling wave ion mobility-mass spectrometry (Synapt G2-Si, Waters).
• Examined products of low-energy CID.

Main Results:

• Observed the formation of a doubly phosphorylated product ion.
• This ion resulted from intermolecular gas-phase phosphate transfer within a phosphopeptide dimer.
• Evidence suggests the formation of a homodimeric phosphohistidine peptide non-covalent complex (NCX).

Conclusions:

• The study reports the first instance of intermolecular gas-phase phosphate transfer between phosphopeptides.
• This transfer leads to the formation of doubly phosphorylated peptide product ions.
• Electrostatic interactions likely stabilize the observed phosphopeptide complexes.