The elementary cellulose fibril in Picea abies: Comparison of transmission electron microscopy, small-angle X-ray scattering, and wide-angle X-ray scattering results

The wood cell wall is built with elementary cellulose fibrils (ECF) having a uniform thickness of 25 +/- 2 Angstrom. 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.