Developing a molecular blueprint for mechanical response

为什么橡皮筋是有弹性的？ 是什么让绳子变硬？ 当我们跑步时，我们的肌腱是如何吸收力量的？ 这些问题与这些材料的弹性和粘性（“粘弹性”）有关，也就是说，当施加和释放应力时，它们会变形多少，然后恢复到原来的形状。 大自然已经利用蛋白质的能力来形成非常不同的机械结构。 例如，我们身体中许多结构组织的分子构建块是蛋白质胶原蛋白和弹性蛋白，它们组装（有时彼此或其他分子）形成肌腱，动脉，皮肤和许多其他组织。 基于胶原蛋白的组织往往是相当僵硬的，而弹性蛋白在数十亿次拉伸-放松循环中提供延展性。 要用合理的工程改造版本取代这些天然蛋白质，需要了解哪些力对这些生物材料的稳定性和粘弹性负责。 我们建议通过减少材料的尺寸和复杂性来简化问题-而不是检查整个组织，我们首先拉伸这些蛋白质，一次一个，然后在它们组装成更复杂的结构时拉伸它们。 通过研究这些不同的尺寸尺度（层次结构），我们希望我们对胶原蛋白和弹性蛋白的机械响应的研究将有助于更好地理解粘弹性的因素，并有助于设计通用的替代品。

Why is an elastic band elastic? What makes a rope stiff? How do our tendons absorb forces when we run? These questions relate to the elasticity and viscosity ("viscoelasticity") of these materials, that is, how much they deform and then return to their original shape when stress is applied and released. Nature has exploited the ability of proteins to form very different mechanical structures. For example, the molecular building blocks for many of the structural tissues in our bodies are the proteins collagen and elastin, which assemble (sometimes with each other or other molecules) to form tendons, arteries, skin and many other tissues. Collagen-based tissues tend to be quite stiff, while elastin provides extensibility over billions of stretch-relax cycles. To replace these natural proteins with rationally engineered versions requires understanding what forces are responsible for the stability and viscoelasticity of these biomaterials. We propose to simplify the problem by reducing the size and complexity of the material - instead of examining whole tissues, we are first stretching these proteins, one at a time, and then stretching them as they undergo assembly into more complex structures. By looking at these different size scales (hierarchies), we hope our studies on the mechanical response of collagen and elastin will lead to a greater understanding of the factors responsible for viscoelasticity and will help in efforts to design versatile alternatives.