New insights into the structure of cellulose in plant cell walls

The structure of native plant cellulose, despite its abundance and utility in industry, remains elusive. The cellulose structure of several species was studied using 2D solid-state Nuclear Magnetic Resonance (NMR) of ¹³ C labelled plants. Six major glucose environments were resolved which are common to the cellulose of poplar wood, spruce wood and grasses. The cellulose structure was maintained in isolated holo-cellulose nanofibrils, allowing more detailed characterisation. There are just two glucose environments within the fibril core which have the same NMR ¹³ C chemical shifts as tunicate cellulose Iβ. The third major glucose site with a carbon 4 shift near 89 ppm, previously assigned to the fibril interior, is one of four surface glucose environments. These advances allowed us to obtain a more accurate measure of the interior to surface ratio for poplar wood fibrils of 0.5, consistent with an 18 chain microfibril structure having 6 core and 12 surface chains.