I have a recombinant peptide with MW of 4564 (41 AA). Recently I tried to kill my peptide by autoclave at 120C for 20 min, however, surprisingly the auclaved peptide becomed even more active!!! The autoclaved peptide had a longer retention time in rpHPLC chromatograph, indicating it is more hydrophobic. LC/MS indicating its MW is 4547, 17 dalton less than expected, like loss of a NH3 molecule from the peptide. What happened there?
I am aware that if a Gln at the N-terminus of a peptide, its side chain will naturally cyclize with the free Amine and cause loss of a NH3. But the N-terminus of my peptide is Gly. What else could happen to cause a 17 dalton less in the peptide?
Thank you for your help and I am looking forward to solving this mistery.