1-thioglycine (internal) 15.977156639099121094 16.06999969482421875 72.99861907958984375 73.12000274658203125 O -1 S 1 MOD_RES 1-thioglycine aminoethanethioic O-acid This modification occurs naturally in two forms. At an interior peptide location it exists as aminoethanethionic acid (or aminoethanethioic O-acid). At the carboxyl-terminal it exists as aminoethanethiolic acid (or aminoethanethioic S-acid). A protein modification that effectively converts a glycine residue to an internal 1-thioglycine. G 1-thioglycine MOD:00270 aminothioacetic acid natural PSI-MOD aminoethanethioic acid thiocarboxylic acid none C 2 H 3 N 1 S 1 aminoethanethionic acid S(O)Gly Carboxy->Thiocarboxy 2-amino-1-sulfanylethanone 1-thioglycine