Structure and Mechanical Properties of Spider Silk Films at the Air鈥揥ater Interface
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- 作者：Anne Renault ; Jean-Fran莽ois Rioux-Dub茅 ; Thierry Lef猫vre ; Sylvie Beaufils ; V茅ronique Vi茅 ; Fran莽ois Paquet-Mercier ; Michel P茅zolet
- 刊名：Langmuir
- 出版年：2013
- 出版时间：June 25, 2013
- 年：2013
- 卷：29
- 期：25
- 页码：7931-7938
- 全文大小：429K
- 年卷期：v.29,no.25(June 25, 2013)
- ISSN：1520-5827
文摘
The kinetics of adsorption of solubilized spider major ampullate (MA) silk fibers at the air鈥搘ater interface and the molecular structure and mechanical properties of the interfacial films formed have been studied using various physical techniques. The data show that Nephila clavipes MA proteins progressively adsorb at the interface and ultimately form a highly cohesive thin film. In situ infrared spectroscopy shows that as soon as they reach the interface the proteins predominantly form 尾 sheets. The protein secondary structure does not change significantly as the film grows, and the amount of 尾 sheet is the same as that of the natural fiber. This suggests that the final 尾-sheet content is mainly dictated by the primary structure and not by the underlying formation process. The measure of the shear elastic constant at low strain reveals a very strong, viscous, cohesive assembly. The 尾 sheets seem to form cross-links dispersed within an intermolecular network, thus probably playing a major role in the film strength. More importantly, the molecular weight seems to be a crucial factor because interfacial films made from the natural proteins are 7 times stronger and 3 times more viscous than those obtained previously with shorter recombinant proteins. Brewster angle microscopy at the air鈥搘ater interface and transmission electron microscopy of transferred films have revealed a homogeneous organization on the micrometer scale. The images suggest that the structural assembly at the air鈥搘ater interface leads to the formation of macroscopically solid and highly cohesive networks. Overall, the results suggest that natural spider silk proteins, although sharing similarities with recombinant proteins, have the particular ability to self-assemble into ordered materials with exceptional mechanical properties.