SAXS STUDIES OF SILK FIBERS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 丝绸是一种由蛋白质组成的生物聚合物。它是由蜘蛛和一些昆虫幼虫合成的，以完成各种功能。根据用途的不同，纤维的蛋白质组成、结构和机械性能也不同。某些真丝纤维，如棒状新丝绸，其拉伸性能可与高性能人造纤维媲美，甚至更好。然而，蚕丝纤维的自然形成过程是在常压和常温下进行的，不涉及任何污染的溶剂，与生产高性能纤维相反。此外，这些人造纤维大多有毒，极难降解，而丝绸是可生物降解的。对自然丝形成过程的详细了解将使我们能够模仿它，从而达到同样的裁剪能力和环保特性。从直接测量可知，蚕丝蛋白溶液的pH值和离子含量随着其向固体纤维的转变而变化，并且施加剪切力。非常低的pH或非常高的剪切力本身就能够触发纤维中最终结构的蛋白质淀粉样折叠和聚集特征。用SAXS研究了1~1 mM的钠、钾、钙、铜、锌、镁等阳离子对蚕丝蛋白的影响。众所周知，所有这些离子的浓度都会随着天然丝绸的形成过程而变化。这项研究涉及微流控芯片在使用不同盐组成的缓冲液生产纤维方面的应用。下一步是在不同阳离子存在的情况下原位观察纤维的形成过程。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Silk is a biopolymer made of protein. It is synthesized by spiders and some insect larvae to fulfill various functions. According to its use, the protein composition, the structure and the mechanical properties of the fiber vary. Certain silk fibers, such as the Nephila clavipes dragline, display tensile properties comparable or even better than those of high-performance man-made fibers. However, the natural process of silk fiber formation occurs at ambient pressure and temperature and does not involve any polluting solvent, contrarily to the production of high-performance fibers. Moreover, most of these man-made fibers are toxic and extremely difficult to degrade whereas silk is bio-degradable. A detailed understanding of the natural silk formation process will enable us to mimic it so as to reach the same tailoring capabilities and environment-friendly properties. It is known from direct measurement that the pH and the ionic content of the silk protein solution changes along its transformation to a solid fiber, and that shear forces are applied. Very low pH or very high shear forces alone are able to trigger the protein amyloidal folding and aggregation characteristic of its final structure in the fiber. SAXS is used to study the effect of several cations on silk protein, such as 1 ¿M to 1 mM of sodium, potassium, calcium, copper, zinc and magnesium. The concentration of all these ions is known to vary along the natural silk formation process. This study involved the application of microfluidic chips to produce fibers using buffers of different salt composition. The next step is to follow in situ the fiber formation process in presence of different cations.