93245-71-7Relevant academic research and scientific papers
Chemical stability of peptides in polymers. 2. Discriminating between solvent and plasticizing effects of water on peptide deamidation in poly(vinylpyrrolidone)
Lai, Mei C.,Hageman, Michael J.,Schowen, Richard L.,Borchardt, Ronald T.,Laird, Brian B.,Topp, Elizabeth M.
, p. 1081 - 1089 (1999)
The mechanistic role of water in the deamidation of a model asparagine- containing hexapeptide (Val-Tyr-Pro-Asn-Gly-Ala) in lyophilized formulations containing poly(vinylpyrrolidone) (PVP) and glycerol was investigated. Glycerol was used as a plasticizer to vary formulation glass transition temperature (T(g)) without significantly changing water content or activity. Increases in moisture and glycerol contents increased the rate of peptide deamidation. This increase was strongly correlated with T(g) at constant water content and activity, suggesting that increased matrix mobility facilitates deamidation. In rubbery systems (T > T(g)), deamidation rates appeared to be independent of water content and activity in formulations with similar T(g)s. However, in glassy formulations with similar T(g)s, deamidation increased with water content, suggesting a solvent/medium effect of water on reactivity in this regime. An increase in water content also affected the degradation product distribution; less of the cyclic imide intermediate and more of the hydrolytic products, isoAsp- and Asp- hexapeptides, were observed as water content increased. Thus, residual water appears to facilitate deamidation in these solid PVP formulations both by enhancing molecular mobility and by solvent/medium effects, and also participates as a chemical reactant in the subsequent breakdown of the cyclic imide.
Effect of pH on the rate of asparagine deamidation in polymeric formulations: pH -rate profile
Song, Yuan,Schowen, Richard L.,Borchardt, Ronald T.,Topp, Elizabeth M.
, p. 141 - 156 (2001)
The rate of Asn deamidation of a model hexapeptide (L-Val-L-Tyr-L-Pro-L-Asn-Gly-L-Ala) was measured as a function of effective pH ('pH') in glassy and rubbery polymeric solids containing poly(vinyl pyrrolidone) (PVP) and in solution controls at 70°C. The reaction exhibited pseudo-first-order kinetics in all samples over a wide 'pH' range (0.5 a >10,000-fold difference in the basic range ('pH'>8). Specific base catalysis was observed in solution and in the polymeric solids under neutral conditions (6 8, whereas the reaction was 'pH'-independent in the polymeric solids in this range. The 'pH' - rate profile and supporting buffer catalysis data are consistent with a change in the rate-determining step in the basic range from 'pH'-dependent attack of the deprotonated backbone amide nitrogen on the Asn side chain in solution to 'pH'-independent ammonia expulsion in the polymeric solids. The results suggest that polymer matrix incorporation not only affects the magnitude of the deamidation rate constant but also the 'pH' dependency of the reaction and the rate-determining step in the basic 'pH' range.
Chemical stability of peptides in polymers. 1. Effect of water on peptide deamidation in poly(vinyl alcohol) and poly(vinyl pyrrolidone) matrixes
Lai, Mei C.,Hageman, Michael J.,Schowen, Richard L.,Borchardt, Ronald T.,Topp, Elizabeth M.
, p. 1073 - 1080 (1999)
This paper examines the effect of water content, water activity, and glass transition temperature (T(g)) on the deamidation of an asparagine- containing hexapeptide (VYPNGA; Asn-hexapeptide) in lyophilized poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) at 50 °C. The rate of Asn- hexapeptide deamidation increases with increasing water content or water activity and, hence, decreasing T(g). The rate of deamidation is more sensitive to changes in these parameters in PVA than in PVP. Deamidation is clearly evident in the glassy state in both formulations. In the glassy state, the peptide is more stable in PVA than in PVP formulations but is less stable in the rubbery state. No single variable (water content, water activity, or T(g)) could account for the variation in deamidation rates in PVA and PVP formulations. Deamidation rates were correlated with the degree of plasticization by water (distance of T(g) from the dry intrinsic glass transition temperature); coincident curves for the two polymers were obtained with this correlation. Deamidation in PVA and PVP was closely correlated with the extent of water-induced plasticization experienced by the formulation relative to its glass transition at 50 °C, suggesting that the physical state of formulations could be used to predict chemical stability.
Controlling deamidation rates in a model peptide: Effects of temperature, peptide concentration, and additives
Stratton, Lewis P.,Kelly, R. Michael,Rowe, Jared,Shively, Jesse E.,Smith, D. David,Carpenter, John F.,Manning, Mark C.
, p. 2141 - 2148 (2001)
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°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°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 β-turn structure, which presumably is less prone to intramolecular cyclization and subsequent deamidation.
