cyclized residue modified L-methionine residue dehydromethionine (3S)-3-carboxy-1-methylisothiazolidin-1-ium -1.0083739757537841797 -1.0099999904632568359 1+ 131.0399322509765625 131.19000244140625 A protein modification that effectively converts an L-methionine residue to dehydromethionine. C 0 H -1 N 0 O 0 S 0 C 5 H 9 N 1 O 1 S 1 L-dehydromethionine M MOD:01906 N-term PSI-MOD artifact