title: Crystal analysis and high-resolution imaging of microfibrillar α-chitin from Phaeocystis.
abstract: The ultrastructure of α-chitin microfibril produced by marine alga Phaeocystis was investigated by FT-IR spectroscopy, X-ray diffraction and electron microscopy. The average size of the microfibril was 17.1±1.8 μm in length and 39.8±8.8 nm in width. The FT-IR spectrum shows typical α-chitin pattern, and each band was sharper than crustacean chitin's, indicating higher crystallinity of the Phaeocystis chitin. The X-ray diffraction gave crystallite size more than twice of crustacean tendon's. The fiber diffraction pattern is consistent with previous studies with two-chains orthorhombic unit cell (Minke and Blackwell, 1978; Sikorski et al., 2009), and refined unit cell dimensions are a=4.742 Å, b=18.871 Å, c=10.338Å. High-resolution electron microscopy of ultrathin sections gave the cross-sectional shape of microfibril as hexagon. The lattice images of (020) plane (d=0.94 nm) were frequently observed extending the entire cross-section of microfibril, indicating its single crystalline nature. These results allowed construction of a molecular packing model for α-chitin crystal.
authors.affiliation: Department of Biomaterials Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kimura
authors.forename: Masahisa
authors.initials: M
authors.lastname: Wada
authors.forename: Shigenori
authors.initials: S
authors.lastname: Kuga
mesh_terms: D002686:Chitin / Q000737:chemistry*; D003460:Crystallization; D058087:Haptophyta / Q000737:chemistry; D020894:Microfibrils / Q000737:chemistry*; D008854:Microscopy, Electron; D008958:Models, Molecular; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D002686:Chitin