The protein Absolute QUAntification (AQUA) is a targeted proteomics strategy that enables robust protein quantification at very low concentration in complex protein mixtures.

AQUA relies on the synthesis of stable isotope labeled native peptides of a protein of interest and their use as internal standards during the LC-MS/MS analysis. Labeled tryptic peptides incorporate heavy amino acids (typically 13C and 15N enriched Lysine or Arginine) that create a slight molecular weight difference with the original peptides without modifying their chemical properties. AQUA peptides can be prepared with covalent modifications such as phosphorylation, methylation or acetylation. The addition of a controlled amount of labeled peptide in the protein sample before digestion and Selected Reaction Monitoring (SRM) analysis enables a precise determination of the quantity of native peptide in the sample.

AQUA workflow

Peptides used in the protein AQUA approach can be prepared using solid phase peptide synthesis or cellular biology.

Cortec Isotope offers a selection of protected labeled amino acids for peptide synthesis, allowing straightforward incorporation of 13C, 15N labeled amino acids to the peptide chain.

For flexible incorporation of heavy isotopes, non-natural amino acids and specific tags into the peptides, trust our expertise with cell-free expression. Our cell-free expression kits employ cellular extracts that exploits the transcription and translation mechanisms of E. coli to produce peptides or proteins in a defined chemical environment.

Cortec Isotope proposes to help you label your protein. For inquiry, please contact our labeled protein expression platform.