Hi

first you most treat your proteins with 6 N HCl at 110 C for 24 h under vacuum after that you can use RP-HPLC after drevitization of your hydrolysis protein with reagents like OPA or PITC.

Perform LC-MS analysis of your aminoacid derivatives. You may use a kit such as Kairos, from Waters.

Mr. Abdelkader,

By soft ionization mass spectrometric methods, both using MALDI and ESI; furthermore the quantification is absolute by means of the methodology and the methods discussed here:

1. Stochastic dynamic electrospray ionization mass spectrometric diffusion parameters and 3D structural analysis of coordination species of copper(II) ion with glycylhomopentapeptide and its dimeric associates, Journal of Molecular Liquids, Volume 282, 15 May 2019, Pages 70-87, Bojidarka Ivanova, Michael Spiteller

2. 3D structural analysis of copper(II) complex of glycine – Experimental mass spectrometric and theoretical quantum chemical approach, Journal of Molecular Structure, Volume 1179, 5 March 2019, Pages 192-204, Bojidarka Ivanova, Michael Spiteller

3. Experimental and theoretical mass spectrometric quantification of diffusion parameters and 3D structural determination of ions of L-tryptophyl-l-tryptophan in electrospray ionization conditions in positive operation mode, Journal of Molecular Structure, Volume 1173, 5 December 2018, Pages 848-864, Bojidarka Ivanova, Michael Spiteller.

Currently, this is the only universally applicable method to the APCI, ESI, MALDI and CID MS approaches, thus enshuring validation of the protocols across different ionization methods.

thank you very much for the answers