title: The effects of alpha-helix on the stability of Asn residues: deamidation rates in peptides of varying helicity.
abstract: Asn deamidation was monitored in Ala-based octadecapeptides of varying alpha-helicity. Gly was substituted for Ala residues at positions 6 and 16 to create a peptide with less helicity. Ala --> Gly substitutions were made at three or more residues from the Asn to negate known primary sequence effects on deamidation rates. The extent of helicity and rate of Asn deamidation for alkaline aqueous solutions of each peptide was measured as a function of temperature by circular dichroism and reversed-phase high-performance liquid chromatography, respectively. The rate of deamidation in the peptides was inversely proportional to the extent of alpha-helicity. The results support the conclusion that Asn deamidation only occurs in the nonhelical population of conformers.
authors.affiliation: Amgen Inc., Thousand Oaks, California 91320, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Kosky
authors.forename: U O
authors.initials: UO
authors.lastname: Razzaq
authors.forename: M J
authors.initials: MJ
authors.lastname: Treuheit
authors.forename: D N
authors.initials: DN
authors.lastname: Brems
mesh_terms: D000409:Alanine; D000595:Amino Acid Sequence; D001216:Asparagine; D005998:Glycine; D007700:Kinetics; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D010455:Peptides; D001216:Asparagine; D000409:Alanine; D005998:Glycine