title: Direct determination of the hydrogen bonding arrangement in anhydrous β-chitin by neutron fiber diffraction.
abstract: The hydrogen bonding arrangement in anhydrous β-chitin, a homopolymer of N-acetylglucosamine, was directly determined by neutron fiber diffraction. Data were collected from a sample prepared from the bathophilous tubeworm  Lamellibrachia satsuma  in which all labile hydrogen atoms had been replaced by deuterium. Initial positions of deuterium atoms on hydroxyl and acetamide groups were directly located in Fourier maps synthesized using phases calculated from the X-ray structure and amplitudes measured from the neutron data. The hydrogen bond arrangement in the refined structure is in general agreement with predictions based on the X-ray structure: O3 donates a hydrogen bond to the O5 ring oxygen atom of a neighboring residue in the same chain; N2 and O6 donate hydrogen bonds to the same carbonyl oxygen O7 of an adjacent chain. The intramolecular O3···O5 hydrogen bond has the most energetically favorable geometry with a hydrogen to acceptor distance of 1.77 Å and a hydrogen bond angle of 171°.
authors.affiliation: Department of Biomaterial and Life Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sawada
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Nishiyama
authors.forename: Paul
authors.initials: P
authors.lastname: Langan
authors.forename: V Trevor
authors.initials: VT
authors.lastname: Forsyth
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kimura
authors.forename: Masahisa
authors.initials: M
authors.lastname: Wada
mesh_terms: D000818:Animals; D002686:Chitin / Q000737:chemistry*; D018360:Crystallography, X-Ray / Q000379:methods; D006860:Hydrogen Bonding; D033363:Neutron Diffraction / Q000379:methods*; D011077:Polychaeta / Q000737:chemistry*
chemical_list: D002686:Chitin