15 September 2020

Through computer simulations researchers at Linköping University have discovered a new way of building efficient molecular motors where weight differences between different isotopes of a hydrogen atom play a decisive role.

A chiral molecule has the particular characteristic of being different from its mirror image in the same way as a left hand is different from a right hand. Essentially, different forms of a chiral molecule have identical properties apart from how they react with other chiral molecules. This is of great importance in organic chemistry, especially in the development of medical drugs that interact with the human body’s biomolecules, which are almost always chiral.

In addition, the chirality of organic molecules can be used in molecular motors to convert light energy into rotary motion. In a recent study, published in Organic Letters, researchers at Linköping University have discovered that one can build efficient molecular motors using the chirality that comes from hydrogen atoms that are present in different isotopes.

- The question we asked ourselves was whether we can use isotopic chirality in the same way we use chemical chirality to design organic molecular motors, says Bo Durbeej, who is the head of the theoretical chemistry unit and professor in computational physics at the Department of Physics, Chemistry and Biology.

The difference between the two types of chirality is that a chemically chiral organic molecule typically requires that a specific carbon atom in the molecule is attached to two different chemical groups. But for a molecule with isotopic chirality, it is sufficient for the carbon atom to be attached to two different isotopes of a hydrogen atom.

- Isotopic chirality is a known concept since the 1930´s, but was long viewed as a curiosity and not very useful. Now we have shown that the concept can actually be used to design molecular motors that are as efficient as chemically chiral motors in transforming light energy into rotary motion, says Bo Durbeej.

Through advanced computer simulations at the National Supercomputer Centre at Linköping University, NSC, Bo Durbeej and his co-workers also show that isotopic chirality can even be advantageous, for one important reason.

- If you switch a chemical group for a hydrogen atom it lowers the weight of the molecule, which then leads to a faster rotation. Basically, there is more power in the motor, says Bo Durbeej.

Molecular motors is a field in fast expansion, basically for its great potential. The 2016 Nobel prize in chemistry was awarded to the pioneers of the field.
- Molecular motors are predicted to make way for new applications in both nanotechnology and medicine, for example in transportation and delivery of medical drugs. It is also really fun to have shown that an old concept like isotopic chirality can contribute to the field’s development, says Bo Durbeej.


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