(740d) Rapid Conformational Fluctuations in a Model of Methylcellulose

Methylcellulose is a biopolymer derived from cellulose that is widely used in the food, construction, cosmetic and pharmaceutical industries. An important feature of methylcellulose is that it can form a hydrogel upon heating. The gel morphology has recently been studied by Lott et al. [Macromolecules 2013, 46, 9760], who demonstrated that methylcellulose forms a fibrillar structure with a uniform diameter of around 14 nm. The detailed gelation mechanism, however, remains unknown. We have investigated the formation of fibrils using the coarse-grained simulation model proposed by Huang et al. [Macromolecules 2016, 49, 1490], wherein an isolated methylcellulose chain collapses into a ring-like structure with an outer diameter consistent with the experimental result. Although this ring-like structure appears to be a precursor to a high-aspect ratio fibril, the model also leads to many “misfolded” shapes, such as bundles and hairpins. Using Langevin dynamics simulation with the LAMMPS package, we found that “flipping events”, characterized by a rapid conformational fluctuation, play an important role in rearranging the shape of the collapsed states, which are essential to fibril formation. We further found that the frequency of flipping events depends strongly on the dihedral potential. We will discuss the implication of these rapid conformational fluctuations on fibril formation.