Post-translational Modifications (PTMs)

Post-translational modifications (PTMs) are additional covalent changes to the protein’s amino acids following biosynthesis. Some proteins require PTMs to reach their mature, functional state. These modifications play an important role in enzyme activation, cell signalling, and protein stability, making PTMs an important and interesting aspect of protein research.

Common PTMs include disulphide bridges, phosphorylation, and glycosylation.


Disulphide Bridge Analysis

This technique is used to characterise disulphide folding pattern, i.e., an analysis of which Cys residues are linked.

Scope of work:

  • Confirmation of Protein identification by MS. We will provide unambiguous identification using our standard MS/MS sequencing service.
  • Identification of location of disulphide bonds. Full protein characterisation will be performed using our high-end LC-MS/MS instruments. The analysis will look for disulphide bonded peptide fragments following enzyme digestion of the protein.

For analysis we require the full theoretical protein sequence, and postulated S-S bridging patterns.

Request Form: Disulphide Bridge Analysis


Phosphorylation Detection

Identification of phosphorylation sites on protein and peptide samples is achieved through titanium dioxide enrichment of the phosphorylated peptides after digestion. This allows detection of just the phosphorylated peptides from a sample and allows identification of the phosphorylation site.

For phosphorylation detection we use a LC-MS/MS system (5600 Triple-TOF [Sciex]). Our approach is first to perform protein identification by tandem MS (as per our standard service). This enables confirmation of protein identity prior to detection of the phosphorylated peptides.

Request Form: Phosphorylation Detection


Frequently Asked Questions

How much protein do I need?

We recommend protein bands or spots are of sufficient concentration to be detected by Coomassie G250 staining. Two bands are required to enable the initial protein identification, although less material can be used for that process. Larger amounts of material increase the probability of achieving a successful result.



  • This field is for validation purposes and should be left unchanged.