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Cornell University

Post-translational modifications (PTM)

This analysis attempts to identify the location of PTMs on the protein. It can also measure the proportion of proteins in a sample that carry a certain modification. In this case, it is necessary to quantify the proteins themselves first (by quantitative proteomics) to be able to measure an increase or decrease of proteins carrying the PTM.

We identify and quantify a variety of post-translational modifications (PTMs) including:

  • Phosphorylation: Ser/Thr, Tyr

  • Glycosylation: N-linked; O-linked including hydroxyproline-based glycosylation

  • Deamidation: Asn and Gln; Arg

  • Ubiquitination and SUMOylation: Lys, Gln
  • Oxidation: His, Trp and Met
  • Methylation: Glu, Lys
  • Acylation: acetylation, malonylation, succinylation, myristoylation and palmitoylation
  • Amino acid mutation: Selenocysteine to dehydroalanine etc.
  • ADP ribosylation: Asp, Gln and Lys
  • N-/C-terminal sequence determination
  • Nitration: Tyr
  • Unnatural amino acid substitution and other chemical modifications

Due to an inherent nature of most PTMs with generally low occupancy rate in biological samples, successful identification and quantitation of PTMs usually relies on sample enrichment of the specific modified peptides prior to nanoLC-MS/MS analysis.

For quantitative PTMs, it is often necessary to quantify the global proteome in parallel between the groups of samples. Either labeled or unlabeled samples will be prepared in two aliquots, where the major aliquot will be used for enrichment of specific targeted PTMs, and the minor aliquot will be used for global quantitative proteome. The parallel analyses allow for dissecting the observed changes of PTMs from the changes of global protein abundance.

To order a PTM analysis, visit our Proteomics and Metabolomics Facility page and request a project consultation.