Tiny synthetic helices with outstanding mechanical properties
A study conducted by Floriane Devaux, a doctoral student at the NanoChem Laboratory (MolSys / Faculty of Science) has made it possible to decode the exceptional mechanical performance of helical molecules that are much smaller than proteins. These unprecedented performances could have applications in various fields such as molecular machines or elastomeric materials. This study was published in the journal Chem.
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hemistry excels in the design and control of molecular structures. Beyond structure, programming molecular dynamics is one of the next big challenges. The conformational dynamics of natural elastomeric proteins, for example, are responsible for their ability to behave either as purely elastic, spring-like molecules that can be reversibly stretched, or as energy-dissipating shock absorbers, depending on their biological role in tissues. For example, muscle proteins are constantly under high mechanical load during muscle operation. Alpha-helices, a secondary structure present in proteins, have been identified as crucial components that reversibly unwind to protect these proteins from mechanical rupture.
Because of protein’s many degrees of conformational freedom, programming protein folding dynamics, and the overall elasticity, rigidity, and motor functions that result, remains an elusive objective," explains Floriane Devaux, a PhD student at the NanoChem lab - headed by Pr Anne-Sophie Duwez -and first author of the article published in Chem (1). On the other hand, smaller and simpler objects such as synthetic foldamers (i.e. a chain molecule that folds into a conformationally ordered state) may be amenable to design. Chemistry excels in designing and controlling molecular structures. Numerous artificial helices based on backbones other than peptides have been developed, yet little is known about their mechanical performance.”
As part of her doctoral thesis, Floriane Devaux studied the mechanics of synthetic helices made of aromatic oligoamides and was able to synthesize the molecules in the group of Prof. Ivan Huc at the IECB Bordeaux and the LMU Munich. The aromatic oligo amide molecules were designed to be interfaced with a force spectroscopy set-up based on atomic force microscopy (AFM) in order to study them one by one, a real achievement for such tiny objects! “We were able to show the exceptional mechanical performance of these helical molecules, which are much smaller than proteins," continues the researcher. And we have been able to show that the elastic response of helices as small as 1 nm is among the fastest and most robust ever described. "The properties of these helices outperform most natural helices such as DNA, polysaccharides and peptides. After being fully stretched, up to 3.8 times their original length, these helices are able to rewind against considerable external forces on a time scale of microseconds.
Principle of force spectroscopy experiments on a single aromatic oligoamide helix. Schematic representation of the unfolding of the helix under the action of a mechanical force applied by the tip of the AFM microscope. Pulling-relaxing cycles are performed at the maximum speed of the instrumentation and show that the molecule refolds in a few microseconds without defect and without energy loss.
This unprecedented elastic behaviour suggests that various applications may arise from their use as building blocks in molecular machines or in new classes of artificial elastomeric materials with tailored mechanical properties.
Scientific Reference
Devaux, X. Li, D. Sluysmans, V. Maurizot, E. Bakalis, F. Zerbetto, I. Huc, et A.-S. Duwez. Single-molecule mechanics of synthetic aromatic amide helices : ultrafast and robust non-dissipative winding, Chem (2021), https://doi.org/10.1016/j.chempr.2021.02.030.
