modified residue with a secondary neutral loss modified L-methionine residue methionine oxidation with neutral loss of 64 Da -63.998287200927734375 -64.09999847412109375 83.03711700439453125 83.089996337890625 C -1 H -4 N 0 O -1 S -1 C 4 H 5 N 1 O 1 S 0 M MOD:00935 Originally created from Unimod:507 that was later deleted. Oxidation of methionine to methionine sulfoxide with neutral loss of CH3SOH. PSI-MOD artifact