Crystal structure and hydrogen bonding system in cellulose I(alpha) from synchrotron X-ray and neutron fiber diffraction.
The crystal and molecular structure, together with the hydrogen-bonding system in cellulose I(alpha), has been determined using atomic-resolution synchrotron and neutron diffraction data recorded from oriented fibrous samples prepared by aligning cellulose microcrystals from the cell wall of the freshwater alga Glaucocystis nostochinearum. The X-ray data were used to determine the C and O atom positions. The resulting structure is a one-chain triclinic unit cell with all glucosyl linkages and hydroxymethyl groups (tg) identical. However, adjacent sugar rings alternate in conformation giving the chain a cellobiosyl repeat. The chains organize in sheets packed in a "parallel-up" fashion. The positions of hydrogen atoms involved in hydrogen-bonding were determined from a Fourier-difference analysis using neutron diffraction data collected from hydrogenated and deuterated samples. The differences between the structure and hydrogen-bonding reported here for cellulose I(alpha) and previously for cellulose I(beta) provide potential explanations for the solid-state conversion of I(alpha) --> I(beta) and for the occurrence of two crystal phases in naturally occurring cellulose.
Nishiyama
Yoshiharu
Y
Department of Biomaterial Sciences, Graduate School of Agriculture and Life Science, the University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan.
Sugiyama
Junji
J
Chanzy
Henri
H
Langan
Paul
P
D002482:Cellulose / Q000737:chemistry*; D018360:Crystallography, X-Ray; D056890:Eukaryota / Q000737:chemistry; D005583:Fourier Analysis; D006860:Hydrogen Bonding; D008958:Models, Molecular; D033363:Neutron Diffraction; D017356:Synchrotrons; D014961:X-Ray Diffraction
D002482:Cellulose