The self-assembly of plant cell wall components by single-molecule force spectroscopy and Monte Carlo modelling

The nature of the interaction between plant cell wall polysaccharides was investigated by force spectroscopy and computer simulations. Single xyloglucan molecules were tethered between a cellulose substrate and an atomic force microscope tip, which was cycled at rates from 0.1 to 7 Hz. The force–extension curves showed force plateaux of tens of piconewtons, in some cases multiple, with no clear rate dependence. Similar force plateaux were predicted by simulations of polymer chains adsorbed to a flat surface and a virtual cantilever, using a coarse-grained Monte Carlo approach. The simulated plateaux were five to ten times smaller than those obtained by experiment. The experimental plateau energies suggest that at least one hydrogen bond per backbone glucose residue is involved in the interaction. Multiple plateaux always decrease in height with extension, implying a self-tensioning system. This behaviour in a biological nanocomposite could have applications in the manufacture of novel synthetic nanocomposites.