@pavel-shliaha could you please double check the calculation of the 6 lines above. These are the different values which are added to the residual mass of the amino acids. A proton is added to all of them later.

I already checked the sequences `PQR` and `ACE` (Carbamidomethyl) against this tool http://db.systemsbiology.net:8080/proteomicsToolkit/FragIonServlet.html