Biophysical Society Thematic Meeting - October 25-30, 2015

Polymers and Self Assembly: From Biology to Nanomaterials Poster Session II

19-POS Board 19 Self-Assembly of Silk Proteins Under a Uniform Flow Ana Herrera 1,2 , Frauke Gräter 1,2 , Eduardo Cruz-chu 1 . 1 Heidelberg Institute for theoretical Studies, Heidelberg, Germany, 2 Universität Heidelberg, Heidelberg, Baden-württemberg, Germany. Natural spider’s silk fibers have unique properties such as high strength, extensibility and biocompatibility. The arrangement of the proteins subunits into crystalline and non-crystalline phases determines the performance of these fibers. The tendency of silk proteins to aggregate increases under flow. It is believed that shear forces guide fiber assembly on a molecular level, by stretching and aligning the protein chains such that the formation of crystalline regions is enhanced. However, the molecular mechanism of shear-induced assembly of silk is unknown. We performed atomistic molecular dynamics (MD) simulations of fragments of the repetitive unit of silk peptides in explicit water under elongational flow. For single peptides, we examined the dependence of peptide extension on the flow velocity. We recovered a worm-like chain behavior, which reflects the intrinsic stiffness and coiling propensity of silk in water. To analyze the assembly pathway, MD simulations of a set of aligned silk peptides (3x3 and 5x5 arrays) with starting configurations obtained from the single peptides stretching stage were performed. On this basis, we were able to quantify the role of the crystal-forming poly-alanine repeats and their elongation by flow for silk beta-stack formation. Our results help to guide experimental attempts to assemble silk and other polymers into tough fibers.

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