Proforma v2
Protein and peptide sequences are usually represented using a string of amino acids using a well-known one letter code endorsed by the IUPAC. However, there is still no clear consensus about how to represent ‘proteoforms’ and ‘peptidoforms’, meaning all possible variations of a protein/peptide sequence, including protein modifications, both artefactual and post-translational modifications (PTMs). There are indeed multiple ways of encoding mass modifications and extended discussion has taken place to achieve a consensus.