(R)-5-oxo-1,4-tetrahydrothiazine-3-carboxylic acid (R)-5-oxoperhydro-1,4-thiazine-3-carboxylic acid 144.0119171142578125 144.1699981689453125 39.994915008544921875 40.020000457763671875 5-oxothiomorpholine-3-carboxylic acid A protein modification that effectively converts an L-cysteine residue to (R)-5-oxo-1,4-tetrahydrothiazine-3-carboxylic acid. C C 2 H 0 N 0 O 1 S 0 C 5 H 6 N 1 O 2 S 1 From DeltaMass: A secondary modification affecting peptides with S-carbamoylmethyl-L-cysteine (CamC) at the N-terminus. These exist in enzymatic digests of proteins that have been S-alkylated with iodoacetamide. Cyclization of N-terminal CamC gives a residue of (R)-5-oxoperhydro-1,4-thiazine-3-carboxylic acid. Peptides in which this has occurred become more hydrophobic, and lose 17 Da from the N-terminal residue. MOD:00419 N-term Otc PSI-MOD Pyro-carbamidomethyl S-carbamoylmethylcysteine cyclization (N-terminus) S-carbamoylmethylcysteine cyclization (N-terminus) Unimod:26 artifact cyclized residue modified L-cysteine residue