*Department of Integrative Biology, University of Guelph, Guelph, ON N1G-2W1, Canada; Hatsopoulos Microfluids Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Integr Comp Biol. 2009 Jul;49(1):32-9. doi: 10.1093/icb/icp007. Epub 2009 Apr 17.
Intermediate filaments are filaments 10 nm in diameter that make up an important component of the cytoskeleton in most metazoan taxa. They are most familiar for their role as the fibrous component of α-keratins such as skin, hair, nail, and horn but are also abundant within living cells. Although they are almost exclusively intracellular in their distribution, in the case of the defensive slime produced by hagfishes, they are secreted. This article surveys the impressive diversity of biomaterials that animals construct from intermediate filaments and will focus on the mechanisms by which the mechanical properties of these materials are achieved. Hagfish slime is a dilute network of hydrated mucus and compliant intermediate filament bundles with ultrasoft material properties. Within the cytoplasm of living cells, networks of intermediate filaments form soft gels whose elasticity arises via entropic mechanisms. Single intermediate filaments or bundles are also elastic, but substantially stiffer, exhibiting modulus values similar to that of rubber. Hard α-keratins like wool are stiffer still, an effect that is likely achieved via dehydration of the intermediate filaments in these epidermal appendages. The diverse mechanisms described here have been employed by animals to generate materials with stiffness values that span an impressive eleven orders of magnitude.
中间丝是直径为 10nm 的丝，构成大多数后生动物分类群细胞骨架的重要组成部分。它们最常见的作用是作为α-角蛋白的纤维成分，如皮肤、头发、指甲和角，但也在活细胞中大量存在。尽管它们在分布上几乎完全是细胞内的，但在盲鳗产生的防御性黏液中，它们是被分泌出来的。本文调查了动物从中间丝构建的令人印象深刻的生物材料多样性，并将重点介绍这些材料的机械性能是如何实现的。盲鳗黏液是一种由水合黏液和柔软中间丝束组成的稀网，具有超柔软的材料特性。在活细胞的细胞质中，中间丝网络形成柔软的凝胶，其弹性通过熵机制产生。单个中间丝或束也是有弹性的，但刚性明显更大，表现出类似于橡胶的模量值。像羊毛一样坚硬的α-角蛋白则更硬，这种效果可能是通过这些表皮附属物中的中间丝脱水来实现的。这里描述的各种机制被动物用来产生具有令人印象深刻的十一阶数量级的刚度值的材料。
