Electron microscopy study of the transformation of cellulose I into cellulose IIII in Valonia

Molecular dynamics (MD) simulations of cellulose III I crystal models have been carried out. The crystal models were composed by either 24 or 48 cellooligomers consisting of either 20 or 40 residues and were surrounded by waters in a periodic boundary box. Two base plane types differing in a constituent crystal lattice plane, (0 -1 0) 9 (0 1 0) and (1 0 0) 9 (0 1 0), were additionally considered. Among the resulting eight crystal models, an overall structure conversion was observed for the seven models. The final structures had a triclinic-like chain arrangement involving one-quarter staggering chains with respect to its axis. The successive, local transformation involving cooperative bends in cellooligomers was observed during the structure conversion. Only the 48 9 20-mer model having the (0 -1 0) lattice plane retained the original crystal structure throughout a 2.5-ns simulation. The MD simulations with an implicit solvent system and a vacuum system were also performed to asses a solvent effect on the structure conversion.

Section: Discussionmentioning

confidence: 99%

Structural stability of the solvated cellulose IIII crystal models: a molecular dynamics study

Yui

Hayashi

2008

“…Preparing cellulose III I from cellulose I involves fracturing of the crystal structure (Roche and Chanzy 1981), particularly between adjacent 1 " 10 ð Þ planes (Sugiyama et al 1987). Simulations were designed to test extreme cases, in which cellulose I b crystals were fractured all the way to nanocrystals comprising individual 1 " 10 ð Þ or (110) planes.…”

Section: Diffractograms From Single Planesmentioning

confidence: 99%

Simulation of X-ray diffractograms relevant to the purported polymorphs cellulose IVI and IVII

Newman

2008

Diffractograms were simulated for model nanocrystals of cellulose I b , using numerical summation of radiation scattered from all carbon and oxygen atoms in the nanocrystal. Diffractogram peaks were sometimes displaced by a few degrees from positions calculated by the Bragg equation, as predicted in a published study based on a different mathematical approach. Simulated diffractograms showed 2 or 3 peaks, depending on the crosssectional size and shape of the model nanocrystal. Some of the 2-peak diffractograms resembled published results for the purported polymorph cellulose IV I , or for cell-wall cellulose, supporting suggestions that cellulose IV I is simply cellulose I fragmented into nanocrystals with relatively small cross-sectional dimensions. A published diffractogram for cellulose IV II could not be simulated with acceptable precision, suggesting that this polymorph might have a crystal structure distinctly different from that of cellulose I b .

“…Although the diffraction patterns of cellulose III generated from cellulose I or cellulose II were found to be similar, infra-red spectroscopy was used to distinguish two forms: cellulose III I and III II (Marrinan and Mann 1956). Cellulose III I can be transformed back into the parent material, cellulose I b , by treatment in hot water (Segal et al 1954;Sueoka et al 1973a;Roche and Chanzy 1981;Chanzy et al 1987) or by a simple heat treatment (Wada 2001). Cellulose III II can be transformed into cellulose II or cellulose IV II by treatment in hot water or in glycerol at 260°C, respectively (Sueoka et al 1973b).…”

Section: Introductionmentioning

confidence: 99%

The thermal expansion of cellulose II and IIIII crystals

Hori

Wada

2006

Highly crystalline samples of cellulose II and III II have been prepared from repeated mercerization of ramie fibers and supercritical ammonia treatment of the mercerized ramie fibers, respectively. The thermal expansion behavior of cellulose II and III II was investigated using X-ray diffraction at temperatures ranging from room temperature to 250°C. With increasing temperature, the unit cell of cellulose II expanded in the lateral directions and contracted in the longitudinal direction, with the a and b axes increasing by 0.54 and 3.4%, respectively, and the c axis decreasing by 0.09%. The anisotropic thermal expansion in these three directions was closely related to the crystal structure and the hydrogen bonding in cellulose II. A similar anisotropic thermal expansion was also observed in cellulose III II . Cellulose III II expanded in the lateral direction but contracted in the longitudinal direction.