Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61820, United States.
ACS Appl Mater Interfaces. 2017 Feb 1;9(4):3977-3984. doi: 10.1021/acsami.6b15068. Epub 2017 Jan 19.
Supramolecular assembly is a powerful method that can be used to generate materials with well-defined structures across multiple length scales. Supramolecular assemblies consisting of biopolymer-synthetic polymer subunits are specifically known to exhibit exceptional structural and functional diversity as well as programmable control of noncovalent interactions through hydrogen bonding in biopolymer subunits. Despite recent progress, there is a need to control and quantitatively understand assembly under nonequilibrium conditions. In this work, we study the nonequilibrium self-assembly of π-conjugated synthetic oligopeptides using a combination of experiments and analytical modeling. By isolating an aqueous peptide solution droplet within an immiscible organic layer, the rate of peptide assembly in the aqueous solution can be controlled by tuning the transport rate of acid that is used to trigger assembly. Using this approach, peptides are guided to assemble under reaction-dominated and diffusion-dominated conditions, with results showing a transition from a diffusion-limited reaction front to spatially homogeneous assembly as the transport rate of acid decreases. Interestingly, our results show that the morphology of self-assembled peptide fibers is controlled by the assembly kinetics such that increasingly homogeneous structures of self-assembled synthetic oligopeptides were generally obtained using slower rates of assembly. We further developed an analytical reaction-diffusion model to describe oligopeptide assembly, and experimental results are compared to the reaction-diffusion model across a range of parameters. Overall, this work highlights the importance of molecular self-assembly under nonequilibrium conditions, specifically showing that oligopeptide assembly is governed by a delicate balance between reaction kinetics and transport processes.
超分子组装是一种强大的方法，可用于生成具有多种长度尺度的明确定义结构的材料。由生物聚合物-合成聚合物亚基组成的超分子组装体特别表现出出色的结构和功能多样性，以及通过生物聚合物亚基中的氢键对非共价相互作用进行可编程控制。尽管最近取得了进展，但仍需要控制和定量理解非平衡条件下的组装。在这项工作中，我们使用实验和分析建模相结合的方法研究了π共轭合成寡肽的非平衡自组装。通过在不混溶的有机层内隔离水性肽溶液液滴，可以通过调节用于触发组装的酸的传输速率来控制水性溶液中肽的组装速率。使用这种方法，肽在反应控制和扩散控制条件下被引导组装，结果表明，随着酸传输速率的降低，从扩散受限的反应前沿到空间均匀组装的转变。有趣的是，我们的结果表明，自组装肽纤维的形态由组装动力学控制，使得使用较慢的组装速率通常可以获得自组装合成寡肽的越来越均匀的结构。我们进一步开发了一个分析反应-扩散模型来描述寡肽组装，并在一系列参数范围内将实验结果与反应-扩散模型进行了比较。总的来说，这项工作强调了非平衡条件下分子自组装的重要性，特别是表明寡肽组装受反应动力学和传输过程之间的微妙平衡控制。
