Defying a central principle of chemistry

Steve Granick, Director of the IBS Soft and Live Matter Center and Dr. Huan Wang, Principal Investigator, report together with 5 interdisciplinary colleagues in the July 31 issue of the journal. Science that common chemical reactions accelerate Brownian diffusion by sending long-range waves to the surrounding solvent.

The findings violate a central dogma of chemistry, that molecular diffusion and chemical reaction are unrelated. Observing that molecules are energized by chemical reaction is “new and unknown,” said Granick. “When one substance transforms into another by breaking and forming bonds, this actually makes the molecules move faster. It is as if chemical reactions are naturally agitated.”

“Currently, nature does an excellent job of producing molecular machines, but in the natural world, scientists have not understood enough how to design this property,” said Wang. “Beyond curiosity about understanding the world, we hope that practically this it can be useful to guide the thought on the transduction of chemical energy for the molecular movement in liquids, for nanorobotics, precision medicine and synthesis of greener materials “.

The unexpected waves generated by chemical reactions, especially when catalyzed (accelerated by substances that are not consumed), propagate at a great distance. For chemists and physicists, this work challenges the textbook view that molecular motion and chemical reaction are decoupled, and that reactions affect only the close vicinity. For engineers, this work shows a powerful new approach to designing nanomotors at a truly molecular level.

By examining 15 organic chemical reactions, researchers study chemical reactions that are workhorses with wide application in the chemical, pharmaceutical, and organic materials industries. For example, “click” reactions assist in the assembly of biomedical compound libraries for detection, and the Grubbs reaction is used in the manufacture of plastics. Its economic impact is important. Estimates indicate that the majority of all manufactured products require catalysis somewhere in their production sequence.

Wang enthusiastically commented, “Now, we are like a baby taking his first steps, and there are many exciting opportunities to grow this baby.”

In designing their study, the researchers were biologically inspired to note that movement can be driven by enzymes and other molecular motors that are prevalent in living systems. Pioneering earlier work by Dr. Ah-Young Jee at the same research center showed this. But there was no consensus among scientists whether these reports could properly extend outside of biology. Analyzing the problem, the researchers made a high-risk, high-reward argument. They hypothesized that the phenomenon would form an approach to understanding molecular machines in the real world.

By testing their hypothesis, the team developed new analytical techniques. Professor Tsvi Tlusty, a theorist, predicted that catalysts in reaction gradients should migrate ‘uphill’ in the direction of least diffusivity. Professor Yoon-Kyoung Cho, a microfluidic expert, designed a custom microfluidic chip to test this idea. Dr. Ruoyu Dong, a researcher, performed computer numerical simulations. “Our interdisciplinary team responded incredibly quickly to research opportunities, thanks to the research freedom of the Korean Institute for Basic Sciences,” said Granick.

The team presents guidelines showing that the magnitude of the diffusion increase in different systems depends on the rate of energy release. These guidelines can be practically useful in estimating the effect on untested reactions. Beyond this, the study is very helpful in broadening the understanding of active materials, a collective term that traditionally refers to things like cells and microorganisms.

Granick concluded: “The fairly new and rapidly growing field of active materials is enriched by this discovery that chemical reactions behave like nano-swimmers made of individual molecules that stir the reaction soup. The concept of active materials it has proven its worth in challenging a central dogma of chemistry. “

These findings were published in the July 31, 2020 issue of Science magazine. The study was conducted at the SII Center for Soft and Living Matter by authors Huan Wang, Myeonggon Park, Ruoyu Dong, Junyoung Kim, Yoon-Kyoung Cho, Tsvi Tlusty, and Steve Granick.