modified residue that can arise from different natural residues crosslinked residues with loss of water L-lanthionine -18.010564804077148438 -18.020000457763671875 172.0306549072265625 172.1999969482421875 A protein modification that effectively cross-links either two L-cysteine residues, or an L-cysteine residue and an L-serine residue by a thioether bond to form L-lanthionine. C 0 H -2 N 0 O -1 S 0 C 6 H 8 N 2 O 2 S 1 C, X Cross-link 2. For the natural form of the lanthionine cross-link see MOD:00120 meso-lanthionine [JSG]. MOD:01839 PSI-MOD artifact lanthionine