A-type crystals from dilute solutions of short amylose chains.
Model A-type amylose single crystals were prepared by recrystallizing dextrins from acid-hydrolyzed native starch and narrow fractions of short chains of enzymatically synthesized amylose, in dilute water/acetone solutions. In most cases, spindle-shaped crystals with a sharp, round or flat apical end were formed, organized in rosettes or fan-like assemblies. The morphology and crystal size were shown to strongly depend on the average degree of polymerization (DP), distribution width (DW), and degree of branching of the chains. The largest and most clearly faceted single crystals were prepared using fractions of synthetic amylose. Typically, 5-10 μm long crystals were obtained from fractions with 17 ≤ DP ≤ 20 and DW ≤ 8. Chains with DP > 40 and a high polydispersity formed ill-defined networks of smaller crystallites. Fractions of branched and more polydisperse limit dextrins yielded crystals smaller than those obtained from narrow fractions of synthetic amylose. The morphological analysis of faceted single crystals combined with electron diffraction data confirmed that the double helices were oriented along the long dimension of the crystal and packed into lamellae with a parallelogram cross section defined by the a and b directions of the monoclinic unit cell of A-amylose. The lamellae are stacked along the c-axis that is oriented parallel but opposite to the growth direction of the crystal.
Montesanti
Nicole
N
Centre de Recherches sur les Macromolécules Végétales (CERMAV-CNRS), BP 53, F-38041 Grenoble Cedex 9, France, Université de Toulouse, INSA-UPS-INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France, UMR 5504, UMR 792 Ingénierie des Systèmes Biologiques et des Procédés, CNRS, INRA, F-31400 Toulouse, France, Unité Biopolymères Interactions Assemblages, Institut National de la Recherche Agronomique, Rue de la Géraudière, BP 71627, F-44316 Nantes Cedex 3, France, and Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
Véronèse
Gabrielle
G
Buléon
Alain
A
Escalier
Pierre-Claude
PC
Kitamura
Shinichi
S
Putaux
Jean-Luc
JL
D000688:Amylose / Q000737:chemistry*; D010316:Particle Size; D033362:Powder Diffraction; D012996:Solutions; D013499:Surface Properties
D012996:Solutions; D000688:Amylose