Mechanical Activation Drastically Accelerates Amide Bond Hydrolysis, Matching Enzyme Activity.

Amide bonds, which include peptide bonds connecting amino acids in proteins and polypeptides, give proteins and synthetic polyamides their enormous strength. Although proteins and polyamides sustain mechanical force in nature and technology, how forces affect amide and peptide bond stability is still unknown. Using single-molecule force spectroscopy, we discover that forces of only a few hundred pN accelerate amide hydrolysis 10 -fold, an acceleration hitherto only known from proteolytic enzymes.

Mechanochemical Cycloreversion of Cyclobutane Observed at the Single Molecule Level.

Mechanochemical cycloreversion of cyclobutane is known from ultrasound experiments. It is, however, not clear which forces are required to induce the cycloreversion. In atomic force microscopy (AFM) experiments, on the other hand, it is notoriously difficult to assign the ruptured bond.

A density functional theory model of mechanically activated silyl ester hydrolysis.

To elucidate the mechanism of the mechanically activated dissociation of chemical bonds between carboxymethylated amylose (CMA) and silane functionalized silicon dioxide, we have investigated the dissociation kinetics of the bonds connecting CMA to silicon oxide surfaces with density functional calculations including the effects of force, solvent polarizability, and pH. We have determined the activation energies, the pre-exponential factors, and the reaction rate constants of candidate reactions. The weakest bond was found to be the silyl ester bond between the silicon and the alkoxy oxygen atom.

Mechanically induced silyl ester cleavage under acidic conditions investigated by AFM-based single-molecule force spectroscopy in the force-ramp mode.

AFM-based dynamic single-molecule force spectroscopy was used to stretch carboxymethylated amylose (CMA) polymers, which have been covalently tethered between a silanized glass substrate and a silanized AFM tip via acid-catalyzed ester condensation at pH 2.0. Rupture forces were measured as a function of temperature and force loading rate in the force-ramp mode.