SAXS STUDIES OF SILK FIBERS

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 蚕丝是由蛋白质制成的生物聚合物。它由蜘蛛和一些昆虫幼虫合成，以实现各种功能。根据其用途，纤维的蛋白质组成、结构和机械性能各不相同。某些丝纤维，如Nephila clavipes拖丝，显示出与高性能人造纤维相当或甚至更好的拉伸性能。然而，与高性能纤维的生产相反，丝纤维形成的自然过程发生在环境压力和温度下，并且不涉及任何污染溶剂。此外，这些人造纤维中的大多数是有毒的，并且极难降解，而蚕丝是生物可降解的。对天然丝形成过程的详细了解将使我们能够模仿它，从而达到相同的剪裁能力和环境友好特性。从直接测量可知，丝蛋白溶液的pH和离子含量随着其向固体纤维的转变而沿着变化，并且施加剪切力。非常低的pH或非常高的剪切力单独能够触发蛋白质淀粉样折叠和其在纤维中的最终结构的聚集特征。SAXS用于研究几种阳离子对丝蛋白的影响，例如1 μ M至1 mM的钠、钾、钙、铜、锌和镁。已知所有这些离子的浓度沿着天然丝形成过程变化。本研究涉及微流控芯片的应用，以生产纤维使用不同的盐组成的缓冲液。下一步是在不同阳离子存在下原位跟踪纤维形成过程。

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.