Insights on the mechanical behavior of keratin fibrils

Supplementary data associated with this article can be found,in the online version, at http://dx.doi.org/10.1016/j.ijbiomac.2016.05.018.

A computational molecular model of a truncated keratin protofibril (8 chains of hair keratin, PDB provided in Supplementary Material) was used, to run a series of steered molecular dynamics simulations obtaining strain-stress curves. These results were compared with experimental mechanical data on hair fibers. Our data demonstrate that the molecular dynamics simulations can model hair mechanical properties. Simulations done in vacuum showed a better agreement with experimental Young's Modulus (YM) values. The role of hydrogen bonds and the secondary structure of keratin on the mechanical properties was evaluated in detail. The incubation with a fragment of one surfactant protein, the SPD-2 peptide (QAAFSQ), showed the improvement of YM of the hair keratin either by simulations and experimental data. For the first, our research provides mechanistic insights on mechanical microscopic properties of keratin protofibrils through molecular dynamics simulations.

The authors acknowledge the access of Minho University “SeARCH” (“Services and Advanced Research Computing with HTC/HPC clusters”) cluster. We also thank the Portuguese Foundation for Science and Technology (FCT) for providing Célia F. Cruz the grant for PhD studies (scholarship SFRH/BD/100927/2014).