School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Science. 2016 Jun 24;352(6293):1555-9. doi: 10.1126/science.aaf3673.
Molecular knots occur in DNA, proteins, and other macromolecules. However, the benefits that can potentially arise from tying molecules in knots are, for the most part, unclear. Here, we report on a synthetic molecular pentafoil knot that allosterically initiates or regulates catalyzed chemical reactions by controlling the in situ generation of a carbocation formed through the knot-promoted cleavage of a carbon-halogen bond. The knot architecture is crucial to this function because it restricts the conformations that the molecular chain can adopt and prevents the formation of catalytically inactive species upon metal ion binding. Unknotted analogs are not catalytically active. Our results suggest that knotting molecules may be a useful strategy for reducing the degrees of freedom of flexible chains, enabling them to adopt what are otherwise thermodynamically inaccessible functional conformations.
分子纽结存在于 DNA、蛋白质和其他生物大分子中。然而，分子纽结可能带来的益处在很大程度上还不清楚。在这里，我们报告了一种合成的分子五角形纽结，它通过控制通过纽结促进的碳卤键裂解形成的碳正离子的原位生成，别构地引发或调节催化化学反应。纽结结构对于这个功能至关重要，因为它限制了分子链可以采用的构象，并防止在金属离子结合时形成无催化活性的物质。无纽结的类似物没有催化活性。我们的结果表明，分子纽结可能是一种有用的策略，可以减少柔性链的自由度，使它们能够采用否则热力学上无法达到的功能构象。
