Analysis of Phosphopeptide Using TOF-TOF
Phosphorylation is a type of post-translational modification of proteins that is used for the intracellular signal transduction in a wide range of living species. For this reason, it is very important to determine where the protein (amino acid) is phosphorylated. In this work, we measure a monophosphopeptide (FQ pS EEQQQTEDELQDK) that was obtained from the tryptic digestion of β-casein (Bovine) using the TOF-TOF option that is available for the JEOL Spiral- TOF™ system.
The monophosphopeptide sample was dissolved in water containing 0.1% trifluoroacetic acid at a concentration of 10 pmol/μL. The matrix for this analysis was made by mixing 150 μL of CHCA (Methanol) at a concentration 30 mg/mL with 35 mg of 3-Aminoquinoline. Next, the monophosphopeptide sample solution and matrix solution were mixed together 1:1 by volume. Afterwards, 0.5 μL of this mixture was placed on the MALDI target plate (2.5 pmol/spot). Finally, the sample spot was measured using the TOFTOF option available on the JMS-S3000 SpiralTOF MS system.