STRUCTURAL STUDIES OF SPIDER-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。 蜘蛛丝是一种生物聚合物，由长的螺旋状纤维结构组成。蜘蛛拖丝具有无与伦比的机械强度，结合了非常高的弹性和拉伸强度[1，2]。了解丝纤维的微观结构对于理解其独特的机械性能至关重要。这些知识将有助于设计新的智能生物材料，用于从安全气囊到传感器到微缝合线到人工韧带和肌腱到药物输送涂层的众多应用[3]。典型的蜘蛛网由几种不同的丝构成，每一种丝都是在不同的腺体中产生的[2]。 由于它们的大尺寸和易于研究，大壶腹腺（MA）受到了最多的关注。 先前对拖丝进行的衍射研究表明，MA丝是一种半结晶生物聚合物，由嵌入富含甘氨酸的无定形基质中的<$-（L-聚丙氨酸）片组成的结晶域组成[4-6]。 相对而言，很少有人知道其他丝，例如，丝的小壶状腺（MI），往往伴随着MA丝。超收缩：向Nephila Clavipes MA丝或拖丝中加入水会导致纤维收缩至其初始长度的50%，并显著改变丝的机械性能[7]。这种现象被称为超收缩。目前对MA丝的一些研究表明，湿丝中的-片区域或多或少是完整的[8-9]。据我们所知，没有对MA和MI丝上的干和湿超收缩纤维进行系统的衍射研究。纤维衍射是在分子水平上确定这些组装体结构的唯一实用方法[10，我们建议在干丝和超浓缩湿丝上对从棒柄络新妇中提取的大壶腹丝和小壶腹丝进行纤维衍射实验。

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. pider silk is a bio-polymer comprised of long, helical, fibrous structure. Spider dragline silks have unsurpassed mechanical strength, a combination of very high elasticity and tensile strength [1,2]. A knowledge of the micro-structure of the silk fibers is crucial in understanding their unique mechanical properties. This knowledge would help in the design of new smart bio-materials for numerous applications ranging from airbags to sensors to micro-sutures to artificial ligaments and tendons to drug delivery coatings [3]. Typical spider webs are constructed from several different silks, each of which is produced in a different gland [2]. Due to their large size and ease of study, major ampullate (MA) glands have received the most attention. Previous diffraction studies have been done on dragline silk indicate that the MA silk is a semicrystalline biopolymer composed of crystalline domains consisting of ¿-(L-polyalanine) sheets embedded in a glycine rich amorphous matrix [4-6]. Comparatively little is known about other silks, eg, the silk of the minor ampullate (MI) glands, which often accompanies MA silk. Supercontraction: Addition of water to Nephila Clavipes MA silk or dragline silk results in fiber contraction to 50% its initial length, and significant changes to the mechanical properties of the silk [7]. This phenomenon has been termed supercontraction. Current understanding from a few studies on the MA silk indicate that the crystalline ¿-sheet regions in the wet silk are more or less intact [8-9].To the best of our knowledge, there is no systematic diffraction studies on the dry and wet-supercontracted fiber on both the MA and the MI silks.Fiber diffraction is the only practical method of structure determination at the molecular level for these assemblies [10, 11].We propose to carry out fiber diffraction experiments on both major and minor ampullate silks extracted from Nephila clavipes on the dry and supercontratcted-wet silks.