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See detailSynthetic oligorotaxanes exert high forces when folding under mechanical load
Sluysmans, Damien ULiege; Hubert, Sandrine ULiege; Bruns, Carson et al

in Nature Nanotechnology (in press)

Folding is a ubiquitous process that nature uses to control the conformations of its molecular machines, allowing them to perform chemical and mechanical tasks. Over the years, chemists have synthesized ... [more ▼]

Folding is a ubiquitous process that nature uses to control the conformations of its molecular machines, allowing them to perform chemical and mechanical tasks. Over the years, chemists have synthesized foldamers that adopt well-defined and stable folded architectures, mimicking the control expressed by natural systems. Mechanically interlocked molecules, such as rotaxanes and catenanes, are prototypical molecular machines that enable the controlled movement and positioning of their component parts. Recently, combining the exquisite complexity of these two classes of molecules, donor–acceptor oligorotaxane foldamers have been synthesized, in which interactions between the mechanically interlocked component parts dictate the single-molecule assembly into a folded secondary structure. Here we report on the mechanochemical properties of these molecules. We use atomic force microscopy-based single-molecule force spectroscopy to mechanically unfold oligorotaxanes, made of oligomeric dumbbells incorporating 1,5-dioxynaphthalene units encircled by cyclobis(paraquat-p-phenylene) rings. Real-time capture of fluctuations between unfolded and folded states reveals that the molecules exert forces of up to 50 pN against a mechanical load of up to 150 pN, and displays transition times of less than 10 μs. While the folding is at least as fast as that observed in proteins, it is remarkably more robust, thanks to the mechanically interlocked structure. Our results show that synthetic oligorotaxanes have the potential to exceed the performance of natural folding proteins. [less ▲]

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See detailDynamic force spectroscopy of synthetic oligorotaxane foldamers
Sluysmans, Damien ULiege; Devaux, Floriane ULiege; Bruns, Carson J. et al

in Proceedings of the National Academy of Sciences of the United States of America (in press)

Wholly synthetic molecules involving both mechanical bonds and a folded secondary structure are one of the most promising architec- tures for the design of functional molecular machines with un ... [more ▼]

Wholly synthetic molecules involving both mechanical bonds and a folded secondary structure are one of the most promising architec- tures for the design of functional molecular machines with un- precedented properties. Here, we report dynamic single-molecule force spectroscopy experiments that explore the energetic details of donor–acceptor oligorotaxane foldamers, a class of molecular switches. The mechanical breaking of the donor–acceptor interactions responsible for the folded structure shows a high constant rupture force over a broad range of loading rates, covering three orders of magnitude. In comparison with dynamic force spectroscopy performed during the past 20 y on various (bio)molecules, the near-equilibrium regime of oligorotaxanes persists at much higher loading rates, at which bio- molecules have reached their kinetic regime, illustrating the very fast dynamics and remarkable rebinding capabilities of the intramolecular donor–acceptor interactions. We focused on one single interaction at a time and probed the stochastic rupture and rebinding paths. Using the Crooks fluctuation theorem, we measured the mechanical work produced during the breaking and rebinding to determine a free- energy difference, ΔG, of 6 kcal·mol−1 between the two local confor- mations around a single bond. [less ▲]

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See detailWhere Ion Mobility and Molecular Dynamics Meet to Unravel the (Un)Folding Mechanisms of an Oligorotaxane Molecular Switch
Hanozin, Emeline ULiege; Mignolet, Benoît ULiege; Morsa, Denis ULiege et al

in ACS Nano (2017), 11(10), 10253-10263

At the interface between foldamers and mechanically interlocked molecules, oligorotaxanes exhibit a spring-like folded secondary structure with remarkable mechanical and physicochemical properties. Among ... [more ▼]

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. © 2017 American Chemical Society. [less ▲]

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See detailMechanochemical Unfolding of Artificial Helical Foldamers by Single-Molecule Force Spectroscopy
Devaux, Floriane ULiege; Li, Xuesong; Huc, Ivan et al

Poster (2017, June 15)

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See detailProbing single molecules with the AFM: Force, motion, dynamics, and function
Duwez, Anne-Sophie ULiege

Conference (2017, June 14)

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See detailMechanochemical Unfolding of Artificial Helical Foldamers by Single-Molecule Force Spectroscopy
Devaux, Floriane ULiege; Li, Xuesong; Huc, Ivan et al

Poster (2017, June 11)

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See detailProbing Single Molecules with the AFM: Force, Motion, Dynamics, and Function
Duwez, Anne-Sophie ULiege

Conference (2017, June 07)

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See detailReal-time capture of the folding-unfolding transitions in a single oligorotaxane foldamer
Sluysmans, Damien ULiege; Hubert, Sandrine ULiege; Bruns, Carson et al

Poster (2017, June)

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See detailCoulombic driven multi-conformational aspects of oligorotaxane switches studied by ion mobility mass spectrometry and molecular dynamics
Hanozin, Emeline ULiege; Mignolet, Benoît ULiege; Morsa, Denis ULiege et al

Conference (2017, June)

Introduction Artificial Molecular Machines (AMMs), such as Mechanically Interlocked Molecules (MIMs) and foldamers, have recently raised tremendous interest due to their unique properties. Under the ... [more ▼]

Introduction Artificial Molecular Machines (AMMs), such as Mechanically Interlocked Molecules (MIMs) and foldamers, have recently raised tremendous interest due to their unique properties. Under the influence of an appropriate stimuli (pH, redox potential, light…), such molecules are able to reversibly switch between distinct conformational states. Scientists may capitalize on such exclusive properties to get a better understanding of the biomacromolecular level or to design innovative “smart” materials. At the interface between foldamers and MIMs, oligorotaxanes exhibit a spring-like folded secondary structure with remarkable mechanical and physicochemical properties. In the present study, we use ion mobility coupled with mass spectrometry (IM-MS) to probe the conformational states of differentially charged oligorotaxanes in the gas phase. Method Oligorotaxanes are donor-acceptor polymers composed of a π electron-donating dumbbell over which a discrete number of π electron-accepting tetracationic cyclophanes are threaded. The numerous intra-molecular interactions provide them a highly-stabilized rigid rod-like structure in solution. We use IM-MS as implemented in the Synapt G2 HDMS (Waters, Manchester, UK) to investigate the structure of the ionized oligorotaxanes. Our purposes are to probe (i) the different populations of stable conformers generated according to the charge state z and (ii) the reversibility of an electron-driven or thermal-driven conformational change in the gas phase implemented via an electron transfer or collisional activation process prior to the mobility separation. Our experimental observations are supported by electronic structure optimizations at the PM6 and DFT levels coupled with Born-Oppenheimer Molecular Dynamics simulations. Preliminary data Our results highlight a progressive elongation of the oligorotaxane structure with increasing charge numbers until it reaches a maximum extension state. Matching the experimental data with theoretical simulations, we find that the oligorotaxanes adopt an entropically-favored globular shape at low z. As z increases, coulombic repulsions occurring between the cyclophanes gradually outweigh the stabilizing π-stacking interactions and force the structure to elongate. This process occurs in a multistep fashion, each corresponding to a distinct group of helical-shaped conformers, before it eventually results in a fully stretched structure. On the other hand, our results also highlight that a charge reduction driven by a non-dissociative electron transfer process leads to a refolding of the structure so that it adopts a size similar to its electrospray-generated counterpart when the appropriate number of electrons is added. This observation may be imparted to the gradual decrease of the Coulomb repulsions between the cyclophanes mediated through increasing numbers of transferred electrons. These results suggests that the transition from one conformer to another is reversible so that the electrostatic balance between the cyclophanes may be used to further tune the structural state adopted by this artificial molecular switch. The second stimulus relied on collisional activation whose inelastic component provides a way to build up energy into the accessible vibrational degrees of freedom. The conformational landscapes of such-activated oligorotaxanes ions were found unchanged in term of collision cross section position but the repartition of population was altered with a promotion of the most elongated conformer, provided the absence of selective fragmentation. Altogether, these results highlight the feasibility of handling the elongation state of oligorotaxanes in the gas phase through appropriate inputs and underline its conformational reversibility properties. Novel aspect Stimuli-induced reversible conformational rearrangements of innovative AMMs studied by IM-MS and molecular dynamics in the gas phase. [less ▲]

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See detailMechanochemical Unfolding of Artificial Helical Foldamers
Devaux, Floriane ULiege; Li, Xuesong; Ivan, Huc et al

Poster (2017, May 19)

Detailed reference viewed: 28 (1 ULiège)
See detailSynthetic Helical Nanoarhitectures: Mechanochemical study and synthesis
Devaux, Floriane ULiege; Li, Xuesong; Huc, Ivan et al

Conference (2017, March 31)

Detailed reference viewed: 20 (1 ULiège)
See detailSMFS on synthetic helical foldamers
Devaux, Floriane ULiege; Li, Xuesong; Huc, Ivan et al

Poster (2016, October 13)

Detailed reference viewed: 21 (1 ULiège)
See detailReal-time capture of the folding-unfolding transitions in a single oligorotaxane foldamer
Sluysmans, Damien ULiege; Hubert, Sandrine ULiege; Bruns, Carson et al

Poster (2016, October 13)

Detailed reference viewed: 13 (0 ULiège)
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See detailSingle-Molecule Force Spectroscopy on Synthetic Helical Nanoarchitectures
Devaux, Floriane ULiege; Li, Xuesong; Huc, Ivan et al

Poster (2016, September)

Inspired by the many folded conformations of the molecular machineries in nature, chemists have been developing the syntheses of artificial folded molecular architectures, namely foldamers. The ... [more ▼]

Inspired by the many folded conformations of the molecular machineries in nature, chemists have been developing the syntheses of artificial folded molecular architectures, namely foldamers. The investigation of these molecules using AFM-based Single Molecule Force Spectrosocopy (SMFS) allows the elucidation of both mechanochemical properties and conformational dynamics on the unimolecular scale in solution. The stepwise synthesis of aromatic oligoamide-based foldamers was designed to produce well-defined helically-folded molecular architectures. A PEO tether was coupled to one end of the foldamer. SMFS pulling experiments on this system yielded specific and reproducible force-extension patterns characteristic of single foldamers. Those patterns were further analyzed to determine unfolding forces and dynamics as well as to propose mechanistics hypotheses of the unfolding process. Several helical foldamers presenting variable lengths were considered. The force values measured for those foldamers are higher than those previously measured in natural biopolymers showing a high stability under a load and a propensity for the development of emergent properties. In addition, the increased stability of these aromatic oligoamide foldamers was confirmed by the observation of almost instantaneous reversibility of the unfolding under load. [less ▲]

Detailed reference viewed: 19 (2 ULiège)
See detailProbing single molecules with the AFM: Force, motion, dynamics, and function
Duwez, Anne-Sophie ULiege

Conference (2016, July 18)

Detailed reference viewed: 14 (3 ULiège)
Peer Reviewed
See detailSingle Molecule force spectroscopy on helical foldamers
Devaux, Floriane ULiege; Li, Xuesong; Huc, Ivan et al

Conference (2016, July 07)

Detailed reference viewed: 11 (4 ULiège)
See detailReal-time capture of the folding-unfolding transitions in a single oligorotaxane foldamer
Sluysmans, Damien ULiege; Hubert, Sandrine ULiege; Bruns, Carson et al

Poster (2016, July)

Detailed reference viewed: 25 (4 ULiège)
See detailReal-time capture of the folding-unfolding transitions in a single oligorotaxane foldamer
Sluysmans, Damien ULiege; Hubert, Sandrine ULiege; Bruns, Carson et al

Scientific conference (2016, July)

Detailed reference viewed: 9 (4 ULiège)
See detailProbing single molecules with AFM: force, movement, dynamics, and function
Duwez, Anne-Sophie ULiege

Conference (2016, July)

Detailed reference viewed: 11 (1 ULiège)