Système modèle de cristallisation de l'amylose A

Abstract : Starch, the main carbohydrate reserve of higher plants and one of the major sources of calories in the human diet, occurs in the form of microscopic granules (1-100 μm) consisting of a mixture of two homopolymers of glucose, namely linear amylose and branched amylopectin. The crystallinity of native starch (about 35%) results from the cluster organization of amylopectin. The short branches of the macromolecule form double helices that associate laterally to form crystalline lamellae. The characterization of these crystallites in the granule at a local scale remains problematic. To study the crystallization of starch, one can also develop simplified or "model" in vitro systems and focus on the behavior of short chains with a degree of polymerization that is is similar to that of the short branches of amylopectin. During this work, we have prepared fractions of short amylose chains by hydrolyzing native starch granules and by in vitro enzymatic synthesis. These fractions have been crystallized in dilute aqueous solutions by slow diffusion of a precipitant. We have studied the influence of various parameters (degree of polymerization, polydispersity, concentration, temperature) on the mode of crystallization and morphology of the products. A detailed crystallographic analysis of single crystals by diffraction and a description of their lamellar structure are presented as well.
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Nicole Montesanti. Système modèle de cristallisation de l'amylose A. Polymères. Université Joseph Fourier (Grenoble I), 2008. Français. ⟨tel-02263603⟩



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