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Unraveling the Molecular Requirements for Macroscopic Silk Supercontraction
ACS Nano ( IF 15.8 ) Pub Date : 2017-09-19 00:00:00 , DOI: 10.1021/acsnano.7b01532 Tristan Giesa 1 , Roman Schuetz 2 , Peter Fratzl 2 , Markus J. Buehler 1 , Admir Masic 1, 2
ACS Nano ( IF 15.8 ) Pub Date : 2017-09-19 00:00:00 , DOI: 10.1021/acsnano.7b01532 Tristan Giesa 1 , Roman Schuetz 2 , Peter Fratzl 2 , Markus J. Buehler 1 , Admir Masic 1, 2
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Spider dragline silk is a protein material that has evolved over millions of years to achieve finely tuned mechanical properties. A less known feature of some dragline silk fibers is that they shrink along the main axis by up to 50% when exposed to high humidity, a phenomenon called supercontraction. This contrasts the typical behavior of many other materials that swell when exposed to humidity. Molecular level details and mechanisms of the supercontraction effect are heavily debated. Here we report a molecular dynamics analysis of supercontraction in Nephila clavipes silk combined with in situ mechanical testing and Raman spectroscopy linking the reorganization of the nanostructure to the polar and charged amino acids in the sequence. We further show in our in silico approach that point mutations of these groups not only suppress the supercontraction effect, but even reverse it, while maintaining the exceptional mechanical properties of the silk material. This work has imminent impact on the design of biomimetic equivalents and recombinant silks for which supercontraction may or may not be a desirable feature. The approach applied is appropriate to explore the effect of point mutations on the overall physical properties of protein based materials.
中文翻译：
揭示宏观丝超缩的分子要求
蜘蛛式拉铲丝是一种蛋白质材料，经过数百万年的发展，已经实现了微调的机械性能。某些拉延丝纤维的鲜为人知的特征是，当暴露于高湿度下时，拉丝纤维会沿着主轴收缩多达50％，这种现象称为超收缩。这与许多其他材料在暴露于湿气时膨胀的典型行为形成对比。分子水平的细节和超收缩效应的机制受到了激烈的争论。在这里，我们报告结合原位机械测试和拉曼光谱结合纳米结构重组到序列中的极性和带电氨基酸的纳米分子锁骨丝超收缩的分子动力学分析。我们将在计算机上进一步展示通过这种方法，这些基团的点突变不仅抑制了超收缩作用，而且甚至将其逆转，同时保持了真丝材料的卓越机械性能。这项工作对仿生等效物和重组丝的设计具有迫在眉睫的影响，对于这些仿丝和重组丝而言，超收缩可能是或可能不是理想的功能。所采用的方法适用于探索点突变对基于蛋白质的材料的整体物理特性的影响。
更新日期：2017-09-19
中文翻译：
揭示宏观丝超缩的分子要求
蜘蛛式拉铲丝是一种蛋白质材料，经过数百万年的发展，已经实现了微调的机械性能。某些拉延丝纤维的鲜为人知的特征是，当暴露于高湿度下时，拉丝纤维会沿着主轴收缩多达50％，这种现象称为超收缩。这与许多其他材料在暴露于湿气时膨胀的典型行为形成对比。分子水平的细节和超收缩效应的机制受到了激烈的争论。在这里，我们报告结合原位机械测试和拉曼光谱结合纳米结构重组到序列中的极性和带电氨基酸的纳米分子锁骨丝超收缩的分子动力学分析。我们将在计算机上进一步展示通过这种方法，这些基团的点突变不仅抑制了超收缩作用，而且甚至将其逆转，同时保持了真丝材料的卓越机械性能。这项工作对仿生等效物和重组丝的设计具有迫在眉睫的影响，对于这些仿丝和重组丝而言，超收缩可能是或可能不是理想的功能。所采用的方法适用于探索点突变对基于蛋白质的材料的整体物理特性的影响。
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