A Revised Structure and Hydrogen-Bonding System in Cellulose II from a Neutron Fiber Diffraction Analysis

作者：Paul A. Langan, Yoshiharu Nishiyama, H. Chanzy · 发表于：Journal of the American Chemical Society · 年份：1999 · DOI：10.1021/ja9916254 · 被引用次数：386 · 研究领域：Advanced Cellulose Research Studies、Cultural Heritage Materials Analysis、Lignin and Wood Chemistry

The crystal and molecular structure and hydrogen bonding system in cellulose II have been revised using new neutron diffraction data extending to 1.2 Å resolution collected from two highly crystalline fiber samples of mercerized flax. Mercerization was achieved in NaOH/H 2 O for one sample and in NaOD/D 2 O for the other, corresponding to the labile hydroxymethyl moieties being hydrogenated and deuterated, respectively. Fourier difference maps were calculated in which neutron difference amplitudes were combined with phases calculated from two revised X-ray models of cellulose II, A and B‘. The revised phasing models were determined by refinement against the X-ray data set of Kolpak and Blackwell, 8 using the LALS methodology. 37 Both models A and B‘ have two antiparallel chains organized in a P 2 1 space group and unit cell parameters: a = 8.01 Å, b = 9.04 Å, c = 10.36 Å, and γ = 117.1°. 15 Model A has equivalent backbone conformations for both chains but different conformations for the hydroxymethyl moieties: gt for the origin chain and tg for the center chain. Model B‘, based on the recent crystal structures of cellotetraose, 21 - 23 has different conformations for the two chains but nearly equivalent conformations for the hydroxymethyl moieties. On the basis of the X-ray data alone, model A and model B‘ could not be differentiated. From the neutron Fourier difference maps, possible labile hydrogen atom positions were identified for each model and refined using LALS. We wer...