The sample undergoes acid hydrolysis, which breaks every peptide bond. The released amino acids are separated by chromatography and quantified. The result is a list of how many units of each amino acid are present, which is compared with the composition expected from the sequence.
It has two uses. The first is to support identity: if the peptide should have two lysines and one valine, the measured ratio must match. The second, and in practice the most important, is to measure peptide content: the absolute amount of amino acids recovered makes it possible to calculate how much of the weighed powder is really peptide, discounting water and counter-ions.
The technique has limitations: some amino acids (tryptophan, cysteine) are partly destroyed during hydrolysis and others (asparagine and glutamine) are converted into their acidic forms, so results are interpreted with corrections.
A certificate that reports peptide content measured by amino acid analysis provides a more useful figure for calculating real concentrations than HPLC purity alone.
Related terms
Learn it in depth at the Peptide University
- Mass spectrometry and identity · Module 7
Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).