Internal standard for amino acid analysis.
A major metabolite of non-essential amino acid L-Cysteine.
L-cysteic acid is an oxidation product of L-cysteine. L-Cysteic acid, an analogue of cysteine sulfinic acid, may be used in studies of excitatory amino acids in the brain, such as those that bind to cysteine sulfinic acid receptors. L-Cysteic acid is a useful agonist at several rat metabotropic glutamate receptors (mGluRs).
Likely impurities are cystine and oxides of cysteine. Crystallise it from water by adding 2 volumes of EtOH. When recrystallised from aqueous MeOH it has m 264-266o, and the anhydrous acid has m ~260o(dec). [Chapeville & Formageot Biochim Biophys Acta 26 538 1957, Riordan & Giese Methods Enzymol 47 31 1977, Beilstein 4 IV 3296.]
