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  • Title: Structure determination of the 1/1 alpha/beta mixed lactose by X-ray powder diffraction.
    Author: Lefebvre J, Willart JF, Caron V, Lefort R, Affouard F, Danède F.
    Journal: Acta Crystallogr B; 2005 Aug; 61(Pt 4):455-63. PubMed ID: 16041096.
    Abstract:
    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.
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