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1.6 Ability of non-cellulose plant polysaccharides to adapt to cellulose conformation

Plant cell walls support the growing plant and enable transportation of water and nutrients between the roots and the shoots. Small plants rely mainly on flexible primary cell wall for this task, while others, such as trees, have developed a highly lignified secondary cell wall. Apart from the degree of lignification, the major difference in the composition of the aforementioned cell wall layers is the type of non-cellulosic polysaccharides that are present. How do these polysaccharides organize and interact with the cellulose surfaces and contribute to the properties of the cell wall layers?   Here we studied spontaneous adsorption of xylan, the main hardwood hemicellulose, onto cellulose microfibril by atomistic molecular dynamics simulations.  The main findings are that an antiparallel orientation is thermodynamically preferred over a parallel one, and that the adsorption is accompanied by conformational change from 3-fold to 2-fold screw, as well as by the formation of regular but orientation-dependent hydrogen bond patterns. Furthermore, xylan adsorption restricts the local dynamics of the surface glucose residues to a level of the crystalline core, which is manifested as a three-fold increase in their 13C NMR T1-relaxation time. [1] Next we will expand our scope to other non-cellulose polysaccharides that are commonly present in plant primary and secondary cell walls.  This study contributes to the fundamental understanding of the biological assembly and recalcitrance of plant cell walls, which will pave the way for an improved utilization of the lignocellulosic components in advanced materials.  [1] Heinonen et al. 2022. Carb. Pol. Vol 285