17 research outputs found
Determination of diffusion coefficients of glycerol and glucose from starch based thermoplastic compounds on simulated physiological solution
Blends of corn starch with poly(ethylene-vinylalcohol) copolymer (SEVA-C) have been
studied and reported as biodegradable. These materials are known to be sensitive to
enzymatic action, evidencing a degradation of the starch phase in α-amylase assays.
However, from the physical-chemical point of view the degradation of the blend is mainly
associated with the leaching of glycerol, since other compounds are not released and no
carbohydrates were found in the degradation solution. Based on these results, the present
work attempts to determinate the respective diffusion coefficients. Four different
experiments were performed, using samples with different thicknesses that were
immersed in a simulated physiological solution. High performance liquid chromatography
(HPLC) was used to separate the sugar derivatives and glycerol from the degradation
solutions. The obtained data were fitted to an empirical model to allow the estimation of
the diffusion coefficient for glycerol and glucose, based on the analytical solution for Fick’s
law of diffusion, and a good agreement was found (R² ≈ 1). The glycerol leaches quickly
out during the first few days of immersion, stabilizing thereafter, presenting greater
diffusion coefficients for thicker samples. As the quantity of saccharides in the solution
remains almost invariable along the experiments, this work also confirms that the
degradation process is difficult without the action of enzymes
Methods for converting cysteine to dehydroalanine on peptides and proteins
Dehydroalanine is a synthetic precursor to a wide array of protein modifications. We describe multiple methods for the chemical conversion of cysteine to dehydroalanine on peptides and proteins. The scope and limitations of these methods were investigated with attention paid to side reactions, scale, and aqueous- and bio-compatibility. The most general method investigated - a bis-alkylation-elimination of cysteine to dehydroalanine - was applied successfully to multiple proteins and enabled the site-selective synthesis of a glycosylated antibody. © The Royal Society of Chemistry 2011