Molecular ordering of cellulose after extraction of polysaccharides from primary cell walls of Arabidopsis thaliana:: a solid-state CP/MAS 13C NMR study

Solid-state CP/MAS C-13 NMR spectroscopy was used to determine the effects of three different sequential extraction procedures, used to remove non-cellulosic polysaccharides, on the molecular ordering of cellulose in a cell-wall preparation containing mostly primary cell walls obtained from the leaves of the model dicotyledon, Arabidopsis thaliana. The extractions were 50 mM trans-1,2-diaminocyclohexane N,N,N',N'-tetraacetic acid (CDTA) and 50 mM sodium carbonate (giving Residue 1); 50 mM CDTA. 50 mM sodium carbonate and 1 M KOH (giving Residue 2); and 50 mM CDTA, 50 mM sodium carbonate and 4 M KOH (giving Residue 3). The molecular ordering of cellulose in Residue I was similar to that in unextracted walls: the cellulose was almost all crystalline, with 43% of molecules contained in crystallite interiors and similar proportions of the triclinic (I-alpha) and monoclinic (I-beta) crystal forms. Residue 2 was partly decrystallized and the remaining crystallites were mostly in the I-beta form. Residue 3 was a mixture of cellulose II. cellulose I and amorphous cellulose. The presence of signals at 100.0 and 102.3 ppm in the spectra of Residues 1 and 2, but not of unextracted cell walls, suggested that the extractions giving these residues caused some of the non-cellulosic polysaccharides. possibly xyloglucans and galactoglucomannans, to become relatively well ordered, for example through interactions with cellulose crystallite surfaces. (C) 2002 Elsevier Science Ltd. All rights reserved.