Blackledge Todd A, Swindeman John E, Hayashi Cheryl Y
Department of Biology, University of California, Riverside, CA 92521, USA.
J Exp Biol. 2005 May;208(Pt 10):1937-49. doi: 10.1242/jeb.01597.
Spider silks are among the strongest and toughest known materials, but investigation of these remarkable properties has been confined largely to orb-weaving spiders. We investigated the mechanical performance of silk from the cobweb-weaving spider Latrodectus hesperus. Both silk from the scaffolding region of the web and sticky gumfooted capture lines had material properties similar to the major ampullate silk that orb weavers use as the framework for their orb webs. Major ampullate fibers obtained from anaesthetized Latrodectus spiders were similar, but exhibited increased stiffness and reduced extensibility. Novel continuous dynamic analysis of the silks revealed that the loss tangent (tandelta) increased rapidly during the first 2-3% of extension and reached a maximum near the yield point of fibers. The loss tangent then rapidly declined at an ever-decreasing rate until failure. We suggest that these data support molecular models for the mechanics of spider silk. We also demonstrate that the addition of sticky aggregate glue to the ends of the gumfooted lines modulates their mechanical performance--reducing stiffness and increasing extensibility. The storage modulus of viscid regions of the gumfooted lines was much lower than dry regions. This may be explained by disruption of hydrogen bonding within the amorphous regions of the fibers due to hydration from the glue.
蜘蛛丝是已知最强韧的材料之一，但对这些非凡特性的研究主要局限于结圆网的蜘蛛。我们研究了结网蜘蛛西方黑寡妇（Latrodectus hesperus）的丝的力学性能。蛛网的脚手架区域的丝和粘性的缠足式捕获丝的材料特性都与圆网织网蜘蛛用作圆网框架的主要壶腹状丝相似。从麻醉后的西方黑寡妇蜘蛛获得的主要壶腹状纤维也相似，但表现出更高的刚度和更低的延展性。对这些丝进行的新型连续动态分析表明，在拉伸最初的2 - 3%过程中，损耗角正切（tanδ）迅速增加，并在纤维的屈服点附近达到最大值。随后，损耗角正切以不断降低的速率迅速下降，直至纤维断裂。我们认为这些数据支持了蜘蛛丝力学的分子模型。我们还证明，在缠足丝的末端添加粘性聚集胶水会调节其力学性能——降低刚度并增加延展性。缠足丝粘性区域的储能模量远低于干燥区域。这可能是由于胶水的水化作用破坏了纤维非晶区的氢键所致。
