Single Crystals of V-Amylose Complexed with α-Naphthol

Lamellar square single crystals of V-amylose were obtained by adding α-naphthol to metastable dilute aqueous solutions of synthetic amylose chains with an average degree of polymerization of 100. The morphology and structure of the crystals were studied using low-dose transmission electron microscopy including high-resolution imaging, as well as electron and X-ray diffraction. The crystals are crystallized in a tetragonal P41212 or P43212 space group with unit cell parameters, calculated from X-ray diffraction data, a = b = 2.2844 nm (±0.0005) and c = 0.7806 nm (±0.001), implying the presence of two amylose chains per unit cell. High-resolution lattice images of the crystals confirmed that the amylose chains were crystallized as 8-fold helices corresponding to the repeat of four maltosyl units.