The harder you pull, the quicker it goes. At least, that used to be the rule in mechanochemistry, a method that researchers apply to set chemical reactions in motion by means of mechanical forces. However, as chemists led by Professor Dominik Marx, Chair of Theoretical Chemistry at the Ruhr-Universität Bochum now report in the journal “Nature Chemistry”, more force cannot in fact be translated one to one into a faster reaction.
The Janus nature of mechanochemistry: Mechanical forces normally accelerate chemical reactions. However, in the case of disulfide bonds, which are present in large numbers in proteins, force-induced structural changes result in a relative deceleration above a certain threshold. The force thus shows its Janus-faced nature. Illustration: P. Dopieralski, D. Marx
With complex molecular dynamic simulations on the Jülich supercomputer “JUQUEEN” they unmasked the Janus-faced nature of mechanochemistry. Up to a certain force, the reaction rate increases in proportion to the force. If this threshold is exceeded, greater mechanical forces speed up the reaction to a much lesser extent.Outdated view: mechanical force steadily reduces energy barrier
This can only be reduced again by an even greater mechanical force. In the next step, the researchers investigated the blockade mechanism on more complex models, including a large protein fragment, similar to previous experiments. “The Janus mechanism explains puzzling and controversial results of previous force-spectroscopy measurements on the protein titin, which is found in muscles”, says Prof. Marx.Role of the solvent decisive for successful simulation
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