Cellulose Microfibril Twist, Mechanics, and Implicationfor Cellulose Biosynthesis.

All-atommolecular dynamics simulations with explicit water solvent were usedto investigate the microstructure and conformational dynamics of celluloseIβ microfibrils as a function of microfibril length and cross-sectionalsize and shape. Cellulose microfibrils quickly develop a right-handedtwist, which then remains stable over the entire 10 ns simulationtime. The helical angle is independent of microfibril length and inverselyproportional to its cross-sectional area, in accord with the expectationsof continuum theory for an intrinsic chiral twist that is opposedby torsional shear. These calculations provideto our knowledgethefirst estimates of the shear modulus of a cellulose microfibril fromMD simulations. The internal strains caused by this helical twist,propagated indefinitely along the microfibril axis, could be relaxedby periodic regions of amorphous structure along the axis of the cellulosemicrofibrils. [ABSTRACT FROM AUTHOR]