title: Controlling deamidation rates in a model peptide: effects of temperature, peptide concentration, and additives.
abstract: The rate of deamidation of the Asn residue in Val-Tyr-Pro-Asn-Gly-Ala (VYPNGA), a model peptide, was determined at pH 9 (400 mM Tris buffer) as a function of temperature and peptide concentration. Over the temperature range 5-65 degrees C, deamidation followed Arrhenius behavior, with an apparent activation energy of 13.3 kcal/mol. Furthermore, increasing the peptide concentration slows the rate of deamidation. Self-stabilization with respect to deamidation has not been reported previously. The rate of deamidation was also determined in the presence of sucrose and poloxamer 407 (Pluronic F127). In both cases, the rate of deamidation was retarded by up to 40% at 35 degrees C. In aqueous solutions containing poloxamer 407, the degree of stabilization is independent of formation of a reversible thermosetting gel. With sucrose, maximum reduction in the deamidation rate was attained with as little as 5% (w/v). Addition of sucrose results in a greater conformational preference for a type II beta-turn structure, which presumably is less prone to intramolecular cyclization and subsequent deamidation.
authors.affiliation: Center for Pharmaceutical Biotechnology and Department of Pharmaceutical Sciences, School of Pharmacy, Campus Box C238, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
authors.forename: L P
authors.initials: LP
authors.lastname: Stratton
authors.forename: R M
authors.initials: RM
authors.lastname: Kelly
authors.forename: J
authors.initials: J
authors.lastname: Rowe
authors.forename: J E
authors.initials: JE
authors.lastname: Shively
authors.forename: D D
authors.initials: DD
authors.lastname: Smith
authors.forename: J F
authors.initials: JF
authors.lastname: Carpenter
authors.forename: M C
authors.initials: MC
authors.lastname: Manning
mesh_terms: D000577:Amides; D001216:Asparagine / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D005079:Excipients / Q000737:chemistry; D008956:Models, Chemical; D010455:Peptides / Q000737:chemistry*; D020442:Poloxamer / Q000737:chemistry; D011487:Protein Conformation; D013395:Sucrose / Q000737:chemistry; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000577:Amides; D005079:Excipients; D010455:Peptides; D020442:Poloxamer; D013395:Sucrose; D001216:Asparagine