When chemists wish to produce a large amount of a substance - as in the case of a new drug - they often turn to catalysts, compounds that speed up chemical reactions
Catalysts with high specificity are required for many tasks, and finding the one whose structure is exactly suitable for linking with certain compounds is complex. Natural catalysts, such as enzymes in the human body that help us digest food, manage to act by changing their structure to fit the task. Chemists have not been able to make much progress in preparing synthetic compounds that can mimic this important behavior - until now.
Chemists from Ohio University have prepared a synthetic catalyst capable of adapting its molecular structure to a specific structure required for a specific task, similar to natural catalysts. In laboratory experiments, the researchers were able to cause a synthetic catalyst - an enzyme-like compound that performs hydrogenation, a reaction used in the processing of oils in the food industry - to fold into a specific structure, or its mirror image (the enantiomer).
The ability to quickly produce a catalyst with a required structure would be a boon to the chemical and pharmaceutical industries, says Jonathan Parquette, a professor of chemistry at Ohio State University. The way a compound folds determines its structure and function, the professor explains. Natural catalysts change their structure repeatedly in response to different chemical signals - just like the enzymes in the body do.
When the scientists need a catalyst with a unique structure or function, they synthesize it through a process consisting of many trials and errors. "It is not unusual to synthesize dozens of different catalysts before obtaining the necessary structure," says the lead researcher. "The most important contribution of this research lies in the fact that it will provide them with a simple and fast way to obtain the required catalyst."
The catalyst in this study is only a prototype for all the other compounds that the chemists hope to produce, says one of the research colleagues. "Ultimately, we are interested in producing catalysts for many other reactions using the basic principles we uncovered in this study," says the researcher. In this study, the researchers synthesized a series of hydrogenation catalysts in the laboratory and forced the compounds to change their structure. The method that the chemists developed is based on pushing certain atoms that are in the scope of the catalyst compound in the right direction in order to start the changes in the structure. The change proceeds towards an important chemical bond through the compound. The bond oscillates like a pivot and leads to a twist in one particular direction that spreads towards the rest of the compound.
In the experiments, the chemists caused the catalysts to twist to one side or the other to form a certain chemical product or its mirror image (the corresponding enantiomer). The different structures in each phase were confirmed using advanced measurement methods such as nuclear magnetic resonance (NMR). The most fascinating finding of the chemists was that the compounds do not adopt a single structure - they arrange themselves according to their immediate environment, that is, the chemical signal received from the outside.
"For many chemical reactions to work, the compounds must fit the catalyst like a hand fits a glove," says the researcher. "Our synthetic compounds are special due to their flexibility. It does not matter, similar to the simplistic image, if the hand is small or large - the "glove" will change its shape to fit it, as long as there is little chemical preference in relation to one of the hands. The "flexible glove" will find a way to fit more, thus assisting in the production of only one of the required buildings."
Despite decades of research, scientists aren't sure exactly how this proliferation occurs. It is possible that it is related to the polarity of different parts of the compound, or to the chemical environment surrounding the edges of the compound. But the lead researcher claims that the new study demonstrates that this expansion can be used to make synthetic catalysts that can change their shape quickly and efficiently - a scientific idea that has not been explored before. The use of adaptive synthetic compounds could even accelerate the discovery and development of new catalysts.
