Computer simulation of reaction-induced self-assembly of cellulose via enzymatic polymerization

We present a comparison between results of computer simulations and neutron scattering/electron microscopy observations on reaction-induced self-assembly of cellulose molecules synthesized via in vitro polymerization at specific sites of enzymes in an aqueous reaction medium. The experimental results, obtained by using a combined small-angle scattering (SAS) analysis of USANS (ultra-SANS), USAXS (ultra-SAXS), SANS (small-angle neutron scattering), and SAXS (small-angle x-ray scattering) methods over an extremely wide range of wavenumber q (as wide as four orders of magnitude) and of a real-space analysis with field-emission scanning electron microscopy elucidated that: (i)the surface structure of the self-assembly in the medium is characterized by a surface fractal dimension of D_s ≤ 2.3 over a wide length scale (∼30nm to ∼30νm); (ii)its internal structure is characterized by crystallized cellulose fibrils spatially arranged with a mass fractal dimension of D_m ≤ 2.1. These results were analysed by Monte Carlo simulation based on the diffusion-limited aggregation of rod-like molecules that model the cellulose molecules. The simulations show similar surface fractal dimensions to those observed in the experiments.