Single-molecule mechanics of synthetic aromatic amide helices: Ultrafast and robust non-dissipative winding

Side chain interactions govern the response of polypeptide alpha-helices under mechanical stress and prevent the formation of beta-sheets

“…We previously showed that this approach, based on the physisorption of caught PEG tethers onto the tip, provides a sufficiently strong and stable attachment of the molecule onto the tip to obtain reliable information on the system grafted on the surface. [14][15][16][17][18][19] As a result of the different side chains (Figure 1), the ahelices form under opposite pH conditions, pH > 11 for PLys and pH < 4 for PGA. Immediately prior to performing single-molecule force spectroscopy experiments, the gold substrates were dipped in a diluted solution of the molecules and a passivating agent PEG6-SH was added, to enable single molecules to be individually distributed and immobilized onto the cleaned surface (see Methods section).…”

“…This approach, combined with the small size of the molecules, also prevents the unspecific adsorption of the polymer chains onto the surface and gives rise to very clean force curves without unspecific peaks. 14,16,[18][19][20][21] Poly(L-lysine) mechanical unfolding. The typical forceextension profile for PLys in a-helix conformation at pH 12 shows a plateau at 34 ± 4 pN (Figure 2).…”

Steering the Mechanism of the Furan-Maleimide Retro-Diels-Alder Reaction to a Sequential Pathway with an External Mechanical Force

“…4,5,29,30 Recently, a stepwise mechanism was evidenced upon the action of an electric field 52 , see also ref 6 for a theoretical investigation. Here, we systematically modeled the response of the four DA adducts shown in Figure 1, proximal endo (Pendo), proximal exo (Pexo), distal endo (Dendo) and distal exo (Dexo), to an external force applied on the anchoring atoms used to tether them to a polymer linker (like the linkers used in ultrasound-induced mechanochemistry 4 or in AFM-based SMFS [53][54][55][56][57] ) using isometric 22,58 and isotensional 47 approaches. For each force value, we characterized the strain energy redistribution using the JEDI method 59 and the stationary points (equilibrium geometry and transition state (TS)).…”

Structural adaptations of electrosprayed aromatic oligoamide foldamers on Ag(111)

“…18 These helices also feature strong resistance to mechanical extension. 19 No experimental conditions have been found to date under which unfolded (extended) or misfolded conformations would be significantly populated.…”

“…Extended aromatic oligoamide ribbons were hitherto reported to form solely under a stretching force. 19 Nevertheless, less stable polyacetylene helices have also been shown to unfold into ribbons on graphite. 32 In fact, the conformational flexibility and unfolding of ribbons on surfaces may control their self-assembly, as exemplified recently by diene surface folding in open chains and shape-persistent macrocycles.…”