Single crystals of amylose V complexes. III. Crystals with 8₁ helical configuration

Abstract

synopsisSingle crystals of amylose V complexes with the 8, helical configuration can be obtained from aqueous solutions of amylose by using a-naphthol as a complexing agent. Morphological observations suggest that the differences in crystallization behavior among the a-naphthol complex and other complexes with alcohols are due to differences in solubility of the complexes in water. Electron diffraction studies indicate a two-dimensional tetragonal unit cell with a = b = 22.9 A. It is deduced that the space group providing a satisfactory arrangement of two helices is one of the enantiomorphs P4,bI8and P4&%. From x-ray diffraction it was found that the c axis spacing of the a-naphthol complex is equivalent to that in 6, and 7, helical amylose crystals. Consequently, the geometry of the helical configuration requires an integral number of glucose residues per turn. The true helical diameters of the n-butanol, isopropanol, and a-naphthol complexes were calculated from experimental data. The ratio was 6:7:8 and indicated that the helix of the a-naphthol complex has eight glucose residues per turn. The diversity of helical configurations in V amylose crystals is discussed.

Helical Conformation in Crystalline Inclusion Complexes of V‐Amylose: A Historical Perspective

“…As proposed by Yamashita and Monobe [53] and Helbert, [10] the tetragonal unit cell of V-amylose complexed with a-naphthol or quinoline would contain 8-fold helices with an external diameter of 1.62 nm. The helical repeat is still around 0.8 nm, identical to the one measured for 6-and 7-fold V-helices.…”

“…During the following years, numerous images and base-plane electron diffraction patterns of V-amylose single crystals prepared with various complexing agents were published. [7,44,[51][52][53] One of the main difficulties to unambiguously characterize the structure of Vamylose complexes was that, although it was known that the X-ray diffraction patterns of wet and dry specimens were often different, the electron diffraction diagrams were recorded from crystals that had lost part or all of the volatile guest molecules in the vacuum of the microscope. One typical paradox was that, at room temperature, hexagonal electron diffraction patterns were recorded from rectangular V n-butanol crystals.…”

The impact of heat-moisture treatment on the molecular structure and physicochemical properties of normal and waxy potato starches

“…The inner diameter of the amylose helix is controlled by the size of the complexing agent. Predominant in the V amylose family is the common form ofV6 amylose, characterized by six glucose units per turn (Cardoso el al., 2007: Jouquand et aI., 2006: Yamashita, et al, 1971. However, for some guest molecules (e.g., iso-and tertiary butyl alcohols,benzoicacid, dimethyl sulphoxide, I-napthol) the helix exhibits a different structure (e.g., V7 [7 glucose residues per turn] and Vg [8 glucose residues per turnJ) (Helbert el al., 1994;Shogrenelal., 2006).…”

Effect of pH on complex formation between debranched waxy rice starch and fatty acids

“…For example, amylose forms helical complexes of six glucose-residues per turn with linear guest molecules, such as normal butanol, fatty acids (FA), and monoglycerides [3][4][5][6]. Amylose also forms helical complexes of seven or eight glucose-residues per turn with branched or bulkier guest molecules, such as iso-butanol, tert-butanol, and ␣-napthol [7][8][9]. During complex formation, the hydrophobic part of the guest molecule is incorporated inside of the amylose helix because the interior surface of the helix is hydrophobic [10].…”