title: Dimerization of a PACAP peptide analogue in DMSO via asparagine and aspartic acid residues.
abstract: To optimize the stability of a peptide development candidate for the treatment of type II diabetes, formulation studies were initiated in organic solvents and compared to results obtained in aqueous solutions. Stability was assessed by reversed phase liquid chromatography (RPLC) and electrospray ionization mass spectrometry (ESI-MS). Previous studies had shown deamidation and hydrolysis to be the primary mechanisms of degradation in aqueous formulations. Surprisingly, the use of an organic solvent did not decrease the rate of degradation and, as presented here, produced degradation products including dimers. We propose here that deamidation can readily occur in polar anhydrous organic solvents such as DMSO and that the dimer forms through intermolecular nucleophilic attack of an amino acid side chain on a stabilized cyclic imide intermediate.
authors: Analytics Department, Process Sciences, Bayer Healthcare, 800 Dwight Way, Berkeley, CA 94710, USA. joanne.severs.b@bayer.com
authors: Joanne C
authors: JC
authors: Severs
authors: Wayne A
authors: WA
authors: Froland
mesh_terms: D000595:Amino Acid Sequence; D001216:Asparagine / Q000737:chemistry*; D001224:Aspartic Acid / Q000737:chemistry*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D019281:Dimerization; D004121:Dimethyl Sulfoxide / Q000737:chemistry*; D008969:Molecular Sequence Data; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D001224:Aspartic Acid; D001216:Asparagine; D004121:Dimethyl Sulfoxide