The self-assembly mechanism of fibril-forming silk-based block copolymers |
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Authors: | Schor Marieke Bolhuis Peter G |
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Institution: | Van 't Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands. |
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Abstract: | Triblock copolymers consisting of a silk-based ((Gly-Ala)(3)Gly-Glu) repeat flanked by hydrophilic outer blocks self-assemble into micrometer long fibrils in response to a trigger. Since the exact mechanism of the fibril formation remains unclear, we employ a multiscale modelling approach in combination with rare event simulations to elucidate key processes. Atomistic scale simulations on the silk-based block suggest a mechanism in which a polypeptide prefolded into a β-roll structure docks to the growing end of a fibril through the formation of Glu-Glu sidechain contacts. Subsequently it can slide to the optimal position before water is expelled to form a dry interface between the fibril end and the attaching block copolymer. In addition, we find that the folded state of the silk-based block is further stabilised through interactions with its neighboring block. Templated folding may also play a role in case a partially folded polypeptide attaches. The coarse-grained simulations indicate that the attachment and subsequent sliding is mediated by the hydrophilic flanks in a size dependent manner. The hydrophilic blocks prevent random aggregation and allow growth only at the end of the fibril. Our multiscale approach may be used for other fibril-forming peptides. |
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