Structure and Dynamics

The structural role of cellulose in plant cell walls is directly linked to its rigidity. By combining molecular dynamics simulations with quasi-elastic neutron scattering we found that cellulose hydrated at 20% w/w (similar to the water content of secondary plant cell walls) has increased hydrogen atom fluctuations and surface conformational disorder than drier cellulose hydrated to 5% w/w, yet is more rigid (>240 K). A detailed description is provided of how hydration-dependent fluctuations (structure) and disorder (dynamics) at the cellulose surface lead to enhancement of cellulose microfibril rigidity (mechanics). This result adds novel insights into the complex action of moisture on plant cell wall structure and strength (https://pubs.acs.org/doi/abs/10.1021/bm5011849).
 
 
Our collaborators successfully expressed and purified the catalytic domain of an Arabidopsis CesA and obtained a low-resolution structure of trimers by small-angle neutron scattering (SANS) and X-ray scattering (SAXS). We built high-resolution atomic-detailed computational models consistent with the scattering data that explore possible arrangement of the monomers in the trimers. The presence of trimeric lobes is consistent with a total of 18 CesA subunits per Cellulose Synthase Complex (CSC). The results support the “hexamer of trimers” model for the CSC, synthesizing an 18-chain cellulose microfibril as its fundamental product (http://www.plantphysiol.org/content/early/2015/11/10/pp.15.01356). 
 

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