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Where Ion Mobility and Molecular Dynamics Meet To Unravel the (Un)Folding Mechanisms of an Oligorotaxane Molecular Switch
ACS Nano ( IF 15.8 ) Pub Date : 2017-09-13 00:00:00 , DOI: 10.1021/acsnano.7b04833 Emeline Hanozin , Benoit Mignolet , Denis Morsa , Damien Sluysmans , Anne-Sophie Duwez , J. Fraser Stoddart 1 , Françoise Remacle , Edwin De Pauw
ACS Nano ( IF 15.8 ) Pub Date : 2017-09-13 00:00:00 , DOI: 10.1021/acsnano.7b04833 Emeline Hanozin , Benoit Mignolet , Denis Morsa , Damien Sluysmans , Anne-Sophie Duwez , J. Fraser Stoddart 1 , Françoise Remacle , Edwin De Pauw
Affiliation
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At the interface between foldamers and mechanically interlocked molecules, oligorotaxanes exhibit a spring-like folded secondary structure with remarkable mechanical and physicochemical properties. Among these properties, the ability of oligorotaxanes to act as molecular switches through controlled modulations of their spatial extension over (un)folding dynamics is of particular interest. The present study aims to assess and further characterize this remarkable feature in the gas phase using mass spectrometry tools. In this context, we focused on the [4]5NPR+12 oligorotaxane molecule complexed with PF6– counterion and probed its co-conformational states as a function of the in-source-generated charge states. Data were interpreted in light of electronic secondary structure computations at the PM6 and DFT levels. Our results highlight two major co-conformational groups associated either with folded compact structures, notably stabilized by intramolecular π–π interactions and predominant for low charge states or with fully stretched structures resulting from significant Coulombic repulsions at high charge states. Between, the oligorotaxane adopts intermediate folded co-conformations, suggesting a stepwise unfolding pathway under increasing repulsive Coulombic constraints. The reversibility of this superstructural transition was next interrogated under electron-driven (nondissociative electron transfer) and heat-driven (collision-induced unfolding) activation stimuli. The outcomes support the feasibility to either unfold or (partially) refold the oligorotaxane foldamer on purpose in the gas phase. Our results show that the balance between the stabilizing π–π interactions and the versatile Coulomb interactions dictates the elongation state of the foldamer in the gas phase and emphasizes the adequacy of mass spectrometry tools for the superstructural characterization of desolvated prototypical artificial molecular machines.
中文翻译：
离子淌度和分子动力学相遇的地方，揭示了低聚轮烷分子开关的（Un）折叠机制
在折叠剂和机械互锁的分子之间的界面处，低聚轮烷显示出类似弹簧的折叠二级结构，具有显着的机械和物理化学特性。在这些性质中，低聚轮烷通过在（未）折叠动力学上的空间扩展的受控调节而充当分子开关的能力是特别令人关注的。本研究旨在使用质谱分析工具评估并进一步表征气相中的这一显着特征。在此背景下，我们重点研究了与PF 6络合的[4] 5NPR +12低聚轮烷分子–抗衡离子，并根据源内产生的电荷状态探究其共构象状态。根据PM6和DFT级别的电子二级结构计算来解释数据。我们的结果强调了两个主要的共构象群，它们与折叠的紧密结构相关，尤其是通过分子内π-π相互作用而稳定，并且主要用于低电荷状态，或者由于在高电荷状态下显着的库伦斥力而具有完全拉伸的结构。两者之间，低聚轮烷采用中间折叠的共构象，表明在斥力库仑约束增加的情况下，逐步展开的路径。接下来，在电子驱动（非解离电子转移）和热驱动（碰撞诱导的展开）激活刺激下，对这种超结构转变的可逆性进行了研究。结果证明了有意在气相中展开或（部分）重新折叠低聚轮烷折叠剂的可行性。我们的结果表明，稳定的π-π相互作用与通用的库仑相互作用之间的平衡决定了气相中折叠剂的伸长状态，并强调了质谱分析工具对于溶剂化原型人工分子机器的超结构表征的充分性。
更新日期：2017-09-14
中文翻译：
离子淌度和分子动力学相遇的地方，揭示了低聚轮烷分子开关的（Un）折叠机制
在折叠剂和机械互锁的分子之间的界面处，低聚轮烷显示出类似弹簧的折叠二级结构，具有显着的机械和物理化学特性。在这些性质中，低聚轮烷通过在（未）折叠动力学上的空间扩展的受控调节而充当分子开关的能力是特别令人关注的。本研究旨在使用质谱分析工具评估并进一步表征气相中的这一显着特征。在此背景下，我们重点研究了与PF 6络合的[4] 5NPR +12低聚轮烷分子–抗衡离子，并根据源内产生的电荷状态探究其共构象状态。根据PM6和DFT级别的电子二级结构计算来解释数据。我们的结果强调了两个主要的共构象群，它们与折叠的紧密结构相关，尤其是通过分子内π-π相互作用而稳定，并且主要用于低电荷状态，或者由于在高电荷状态下显着的库伦斥力而具有完全拉伸的结构。两者之间，低聚轮烷采用中间折叠的共构象，表明在斥力库仑约束增加的情况下，逐步展开的路径。接下来，在电子驱动（非解离电子转移）和热驱动（碰撞诱导的展开）激活刺激下，对这种超结构转变的可逆性进行了研究。结果证明了有意在气相中展开或（部分）重新折叠低聚轮烷折叠剂的可行性。我们的结果表明，稳定的π-π相互作用与通用的库仑相互作用之间的平衡决定了气相中折叠剂的伸长状态，并强调了质谱分析工具对于溶剂化原型人工分子机器的超结构表征的充分性。
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