OPEN-CHAIN PEPTIDES OBTAINED BY ACIDIC HYDROLYTIC CLEAVAGE OF CYCLOSPORINE-A

Hydrolysis of cyclosporin A (CsA) was studied in order to clarify the still undefined point of attack of the acidic degradation. Among ether extractable and water-soluble products formed from CsA in HCl, two op en-chain peptides were isolated by high-performance liquid chromatogra phy which were identified as the deca- and nonapeptides deriving from CsA through the hydrolytic cleavage of amino acid residue 11 and both residues 11 and 10, respectively. Identification was carried out by fa st atom bombardment tandem mass spectrometry.