Effect of N-1 and N-2 residues on peptide deamidation rate in solution and solid state
Journal Title: The AAPS Journal - Year 2006, Vol 8, Issue 1
Abstract
The deamidation kinetics of 7 model peptides (VYPNGA, VYGNGA, VFGNGA, VIGNGA, VGGNGA, VGPNGA, and VGYNGA) were studied at 70°C in pH 10 buffer solutions and at 70°C and 50% relative humidity in lyophilized solid formulations containing polyvinyl pyrrolidone (PVP). The disappearance of the model peptides from solution and solid-state formulations followed apparent first-order kinetics, proceeding to completion in solution. In the solid state, the reactions showed plateaus with ≈10% to 30% of the model peptides remaining; this was thought to be due to reversible complexation of the peptides and the PVP followed by slow dissociation of the complexes. The residues immediately N-terminal to asparagine (N-1, N-2) influenced the rate of deamidation significantly in the solid state but had minimal effect in solution. Increases in the volume and hydrophobicity of the N-1 and N-2 residues decreased the rate of deamidation in the solid state, but neither parameter alone adequately accounted for the observed effects. An empirical model using a linear combination of volume and hydrophobicity was developed; it showed that the influences of the volume and the hydrophobicity of the residues in the N-1 and N-2 positions are approximately equally important for the N-1 and N-2 residues.
Authors and Affiliations
Bei Li, Richard L. Schowen, Elizabeth M. Topp, Ronald T. Borchardt
Keywords
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- EP ID EP681651
- DOI 10.1208/aapsj080120
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