Identification of In Vivo Phosphorylation Sites
The process of phosphorylation in the body involves transferring a phosphate group from adenosine triphosphate (ATP) to the side chain of an amino acid in a protein, catalyzed by a kinase. As a result, ATP is converted to adenosine diphosphate (ADP). Phosphorylation can occur on various amino acid residues, primarily focusing on tyrosine, serine, and threonine residues within the peptide chain. These residues have free hydroxyl groups and are uncharged. Upon phosphorylation, the protein gains a charge, which leads to a structural change and subsequently alters the protein's activity.
The identification of phosphorylation sites in vivo is primarily conducted through mass spectrometry analysis. This involves specific steps (such as antibody enrichment, metal enrichment, and lectin enrichment) to obtain enriched modified peptide segments, followed by tandem mass spectrometry analysis. In a single mass spectrometry identification, thousands of modified peptides can be reliably identified. However, the localization and recognition of phosphorylation sites in vivo remain relatively arbitrary, and identification of certain modification sites may be unreliable. Factors such as noise signals in the mass spectrometry, neutral loss of unmodified fragments in phosphorylation, and distinguishing between modified and non-modified amino acids with the same mass-to-charge ratio need to be considered during the processing of actual mass spectrometry spectra.
In addition, when processing phosphoprotein sample mass spectrometry data, it is necessary to control the false discovery rate (FDR) for modification sites. For peptide phosphorylation site identification, reliability of phosphorylation sites can be assessed using quality reliability algorithms, which mainly include probability-based scoring (such as building data models) and calculations based on false discovery rates (such as the Target-Decoy algorithm). For protein phosphorylation modifications, there is no well-implemented method for false localization rate (FLR), and it is usually evaluated by synthetic peptides or works better for peptides containing only one modification site. Currently, site localization software attempts to assess the probability of a given peak matching a specific site, such as the A-Score algorithm, or by calculating the score difference between two modification sites provided by the search engine. When selecting these algorithms, the type of mass spectrometry platform detection, the convenience of search algorithms, and software should be comprehensively considered to provide more reliable phosphorylation sites for subsequent analysis.
Biotech Pack uses Thermo Fisher's Q Exactive HF mass spectrometry platform, Orbitrap Fusion mass spectrometry platform, and Orbitrap Fusion Lumos mass spectrometry platform combined with Nano-LC to launchphosphorylation quantitative proteomics analysisservice package. Just tell us your experimental purpose and send the samples, Biotech Pack will handle all subsequent project matters, including protein extraction, protein digestion, phosphopeptide enrichment, peptide separation, mass spectrometry analysis, mass spectrometry raw data analysis, and bioinformatics analysis.
Related services:
multi-pathway phosphoproteomics
post-translational modification proteomics analysis
histone post-translational modification analysis
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