Department of Physics, University of York, Heslington, York YO10 5DD, UK.
Department of Materials Science and Engineering, The University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK.
Molecules. 2021 Mar 16;26(6):1663. doi: 10.3390/molecules26061663.
The flow-induced self-assembly of entangled silk proteins is hypothesised to be aided by the 'registration' of aligned protein chains using intermolecularly interacting 'sticky' patches. This suggests that upon chain alignment, a hierarchical network forms that collectively stretches and induces nucleation in a precisely controlled way. Through the lens of polymer physics, we argue that if all chains would stretch to a similar extent, a clear correlation length of the stickers in the direction of the flow emerges, which may indeed favour such a registration effect. Through simulations in both extensional flow and shear, we show that there is, on the other hand, a very broad distribution of protein-chain stretch, which suggests the registration of proteins is not directly coupled to the applied strain, but may be a slow statistical process. This qualitative prediction seems to be consistent with the large strains (i.e., at long time scales) required to induce gelation in our rheological measurements under constant shear. We discuss our perspective of how the flow-induced self-assembly of silk may be addressed by new experiments and model development.
纤维蛋白的流致自组装假设是通过使用分子间相互作用的“粘性”补丁来“注册”对齐的蛋白质链来辅助的。这表明，在链对齐后，会形成一个分层网络，以协同的方式拉伸并以精确控制的方式诱导成核。从聚合物物理学的角度来看，我们认为如果所有的链都能伸展到相似的程度，那么在流动方向上的粘性剂的相关长度就会变得清晰，这确实可能有利于这种注册效应。通过在拉伸流和剪切两种情况下的模拟，我们发现，另一方面，蛋白质链的拉伸存在非常广泛的分布，这表明蛋白质的注册并不是直接与施加的应变相关，而是一个缓慢的统计过程。这种定性预测似乎与我们在恒剪切流变学测量中诱导凝胶所需的大应变（即在长时间尺度上）一致。我们讨论了如何通过新的实验和模型开发来解决丝的流致自组装问题。
