Structure determination of the 1/1 alpha/beta mixed lactose by X-ray powder diffraction.
The mixed form of alpha/beta lactose was obtained by heating amorphous alpha-lactose at 443 K. NMR spectroscopy determined the stoichiometry of this mixed compound to be 1/1. The X-ray powder diffraction pattern was recorded at room temperature with a sensitive curved detector (CPS 120). The structure was solved by real-space methods (simulated annealing) followed by Rietveld refinements with soft constraints on bond lengths and bond angles. The H atoms of the hydroxyl groups were localized by minimization of the crystalline energy. The cell of 1/1 alpha/beta lactose is triclinic with the space group P1 and contains two molecules (one molecule of each anomer). The crystalline cohesion is achieved by networks of O-H...O hydrogen bonds. The width of the Bragg peaks is interpreted through a microstructural approach in terms of isotropic strain effects and anisotropic size effects.
Lefebvre
Jacques
J
Laboratoire de Dynamique et Structure des Matériaux Moléculaires, UMR CNRS 8024, UFR de Physique, Bâtiment P5, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq CEDEX, France. jacques.lefebvre@univ-lille1.fr
Willart
Jean François
JF
Caron
Vincent
V
Lefort
Ronan
R
Affouard
Frédéric
F
Danède
Florence
F
D002236:Carbohydrate Conformation; D006860:Hydrogen Bonding; D007785:Lactose / Q000737:chemistry*; D008958:Models, Molecular; D033362:Powder Diffraction; D014961:X-Ray Diffraction
D007785:Lactose