The Elementary Cellulose Fibril in Picea abies: Comparison of Transmission Electron Microscopy, Small-Angle X-ray Scattering, and Wide-Angle X-ray Scattering Results

Abstract

The wood cell wall is built with elementary cellulose fibrils (ECF) having a uniform thickness of 25 ± 2 A. This was shown by investigating the same samples independently with three different experimental techniques, transmission electron microscopy (TEM), wide-angle X-ray scattering (WAXS), and small-angle X-ray scattering (SAXS). Discrepancies between results from these techniques discussed in many earlier studies did not appear in the present work. In particular, it was shown that the size distribution measured on TEM pictures is exactly the same as the one estimated from SAXS, if the statistical error introduced by the grain size of the contrasting medium is taken into account for the evaluation of the pictures. The fact that native cellulose fibrils have a uniform thickness in the wood cell wall-which is not the case in many other cellulose preparations-could indicate a biological regulation of the thickness, possibly to achieve better mechanical stability of the cell wall.

Nanostructure of cellulose microfibrils in spruce wood

“…X-ray diffraction patterns from wood with very well oriented microfibrils resemble the fiber diffraction pattern from crystalline cellulose Iα and Iβ but are much more diffuse (19,23,39). At such a low level of resolution it is not possible to distinguish the Iα and Iβ forms by crystallographic means (45) and for clarity all reflections are indexed here on the Iβ lattice.…”

“…X-ray scattering from wood in its native state is dominated by the form function. Jakob, et al (23) succeeded in extracting an interference contribution numerically, but it was small and difficult to characterize. From this observation it may be concluded that either the packing of wood microfibrils is too irregular to diffract strongly (42) or there is insufficient X-ray contrast between the microfibrils and any interstitial material (23).…”

“…Jakob, et al (23) succeeded in extracting an interference contribution numerically, but it was small and difficult to characterize. From this observation it may be concluded that either the packing of wood microfibrils is too irregular to diffract strongly (42) or there is insufficient X-ray contrast between the microfibrils and any interstitial material (23). Intriguingly, an equatorial X-ray diffraction peak like that from celery cellulose microfibrils was observed after spruce wood was vigorously oxidized by chlorite/acetic acid (42).…”

“…However each technique has drawbacks and agreement has not been generally good. Diameters suggested have ranged from 2.2 nm to 3.6 nm (20,23). These upper and lower limits correspond to about 12 and 32 chains (πr 2 ∕0.317) if it is assumed that the wood microfibrils are approximately circular in crosssection and each chain occupies 0.317 nm 2 as in cellulose Iβ (9).…”

CHITINASE-LIKE1/POM-POM1 and Its Homolog CTL2 Are Glucan-Interacting Proteins Important for Cellulose Biosynthesis in Arabidopsis

“…X-ray diffraction has previously been used for Arabidopsis samples (Fujita et al, 2011). With x-ray diffraction, information on crystallinity, crystallite size, and orientation of cellulose can be gained with very little sample preparation (Jakob et al, 1995). We analyzed intact stems rather than fractionated cellulose as cellulose crystallinity (Hermans and Weidinger, 1949) and crystallite size (Haase et al, 1976) are sensitive to acid treatments.…”