Single crystals of V-amylose complexed with bicyclic organic compounds.

Cong Anh Khanh Le (1) , Luc Choisnard (2) , Denis Wouessidjewe (2) , Jean-Luc Putaux (1)

1 CERMAV - Centre de Recherches sur les Macromolécules Végétales
2 DPM - Département de pharmacochimie moléculaire

Lamellar single crystals of V-amylose were prepared from dilute aqueous solutions in the presence of selected bicyclic compounds. Transmission electron microscopy images as well as electron and X-ray diffraction patterns revealed that two allomorphs containing 7-fold amylose single helices were formed depending on the complexing agent. On the one hand, trans-decalin and (-)-b-pinene induced the crystallization of an orthorhombic unit cell isomorphous to that of V2-propanol crystals reported in the literature (referred to as V7II). On the other hand, (+)-camphor and (-)-borneol yielded a new compact pseudo-hexagonal structure (referred to as V7I). Cisdecahydro-1-naphthol and decahydro-2-naphthol induced the formation of both allomorphs. V7I was favored at a higher crystallization temperature compared to V7II. Upon drying in vacuum, both V7I and V7II converted into the hexagonal anhydrous allomorph V7a but the initial structures were recovered by rewetting the crystals in water at room temperature. In addition, washing the crystals with methanol resulted in a transition from a 7-fold to a 6-fold helical conformation of amylose. The results suggest that both water and complexing agent play an important role on the formation and stability of V-amylose crystals.

Domaines: Polymères

Cong Anh Khanh Le, Luc Choisnard, Denis Wouessidjewe, Jean-Luc Putaux. Single crystals of V-amylose complexed with bicyclic organic compounds.. 12th International IUPAC Conference on Polymer-Solvent Complexes and Intercalates (POLYSOLVAT-12), Sep 2018, 386, pp.190007, 2019, ⟨10.1021/masy.2019000007⟩. ⟨hal-02314449⟩