[Chemical stability of salmon calcitonin (sCT) analogues in aqueous solution].

Calcitonin is a peptide hormone with 32 amino acids. Natural calcitonins are presumably quite unstable in solution and numerous analogues of calcitonin had been synthesized to improve the stability. In the present paper, we report the investigation of the chemical stability of salmon calcitonin (sCT) analogues [Val1, Ala7]sCT, [Val1, Ala7, Ala30]sCT and [D-Ala30]sCT in aqueous solutions by reversed phase high-performance liquid chromatography (RP-HPLC) and fast atom bombardment mass spectrometry (FAB-MS) methods. The degradation patterns of the sCT analogues showed a marked dependence on pH and temperature. Most of the degradation products in pH 9.0 solution of sCT and its analogues were identified by FAB-MS analysis. Results showed that the sCT analogues are more stable at pH 3.3 and pH 3.7 than at pH 6.0 and pH 9.0. Analogues without disulfide bridge [Val1, Ala7]sCT and [Val1, Ala7, Ala30]sCT showed higher chemical stability than sCT while [D-Ala30]sCT showed lower chemical stability than the native sCT.