Supramolecular polymers (SPs) formed by self-assembly of peptide-based molecular units assume a variety of interesting one-dimensional (1D) morphologies. While the morphological complexity and phase behavior of self-assembling peptide conjugates bear some resemblance to those of low-molecular-weight and macromolecular surfactants, Y-junctions, or three-way connected constructs, a topological defect observed in traditional surfactants has not been identified, likely due to the intolerance of defective packing by the strong, associative interactions afforded by the peptide segments. Here we report our discovery of branched SPs with Y-junctions and occasionally enlarged spherical end-caps formed by micellization of a ferrocene-based peptide amphiphile in water. Our results suggest that the incorporation of two ferrocenes into the amphiphile design is key to ensure the formation of branched SPs. We hypothesize that the complex interplay of internal interactions limits the effective propagation of hydrogen bonding within the assemblies and, consequently, creates fragmented β-sheets that are more tolerant for supramolecular branching. Given the redox sensitivity of the ferrocene units, sequential addition of reductants and oxidants to the solution led the assemblies to reversibly transform between branched SPs and spherical aggregates.

中文翻译：

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在自组装肽两亲体系中发现 Y 形超分子聚合物

由基于肽的分子单元自组装形成的超分子聚合物 (SP) 呈现出各种有趣的一维 (1D) 形态。虽然自组装肽偶联物的形态复杂性和相行为与低分子量和大分子表面活性剂、Y 型连接或三向连接结构有些相似，但尚未发现在传统表面活性剂中观察到的拓扑缺陷，可能是由于肽段提供的强关联相互作用不能容忍缺陷包装。在这里，我们报告了我们发现的带有 Y 型连接的支链 SP，偶尔会通过基于二茂铁的肽两亲化合物在水中胶束化形成扩大的球形端帽。我们的结果表明，将两种二茂铁结合到两亲物设计中是确保支化 SP 形成的关键。我们假设内部相互作用的复杂相互作用限制了组装体中氢键的有效传播，因此产生了更能容忍超分子分支的碎片化 β-折叠。鉴于二茂铁单元的氧化还原敏感性，向溶液中顺序添加还原剂和氧化剂会导致组件在支化 SP 和球形聚集体之间可逆地转变。产生更能容忍超分子分支的片段化 β-折叠。鉴于二茂铁单元的氧化还原敏感性，向溶液中顺序添加还原剂和氧化剂会导致组件在支化 SP 和球形聚集体之间可逆地转变。产生更能容忍超分子分支的片段化 β-折叠。鉴于二茂铁单元的氧化还原敏感性，向溶液中顺序添加还原剂和氧化剂会导致组件在支化 SP 和球形聚集体之间可逆地转变。