Secondary structures glucan

Submicrofibril and triple-stranded left-hand helical microfibrils are found in tobacco primary cell wall and bacterial A. xylinum cellulose. We suspect from our results and the literature survey outlined in reference (1) that the triple stranded structures are prominent in the primary plant cell wall. The highly crystalline cellulose of plant and algae secondary cell wall appears by X-ray fiber diffraction (18,19) and TEM lattice imaging (20-23) to be largely crystalline arrays of planar straight chains of (l-4)-/3-D-glucan chains. 

The observation47 that the stability of the secondary-ordered structure of xanthan (and as a consequence, its susceptibility to hydrolysis by cellulase) is a function of temperature, pH, and ionic strength has allowed the application of enzymic techniques to structural analysis. Xanthan is hydrolyzed in salt-free, aqueous solutions at elevated temperatures that is, hydrolysis occurs if the chain is unordered. It was proposed that, at lower temperatures and in the presence of salt, the small side-chains organize around the (1 ->4)-/3-D-glucan backbone and protect it from hydrolysis. 

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