Short Peptide synthesis, Fmoc-SPPS wth citrullin, why can it show a different mass?

I tried Fmoc-SPPS with short cyclicPeptides (12 aa length, Brom-Acetyl at the start for cyclization), for the first time containing citrollin. Many of the petides show a main Peak at the MALDI MS...

01 April 2020 4,120 3 View