Novel Approach Enables Tailor-Made Mirror Molecules

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Researchers from Deutsches Elektronen-Synchrotron (DESY) devised a new experimental scheme to develop custom-made mirror molecules for analysis

A team of researchers from DESY, University of Hamburg, and University College London devised a new experimental scheme to develop custom-made mirror molecules for analysis. According to the researchers, the technique is capable of rapidly spinning ordinary molecules that cause them to lose their normal symmetry and shape to form mirrored versions of each other. The research was published in the journal Physical Review Letters on November 08, 2018.

Several molecules in nature exist in two versions that are mirror images of each other. According to Andrey Yachmenev, who led this theoretical work in Küpper’s group at the Center for Free-Electron Laser Science (CFEL), cells in organisms prefer left-handed proteins, whereas the genome is organized as right-handed double helix. However, the mechanism behind the variation is not yet understood. Moreover, mirror versions of certain molecules tend to change chemical reactions and the behavior of materials. According to co-author Alec Owens from the Center for Ultrafast Imaging (CUI), although chirality only occurs naturally in some types of molecules, it can be artificially induced in symmetric-top molecules. When these molecules are stirred with significant speed, they lose their symmetry to form two mirror forms that depend on direction of rotation. However, Owens stated that this phenomenon of rotationally-induced chirality is less understood as no scheme for its generation that can be followed experimentally exists.

The team computationally devised an approach to achieve this rotationally-induced chirality with realistic parameters in the lab. The approach uses optical centrifuges that are corkscrew-shaped laser pulses. The team studied phosphine (PH3) and their quantum-mechanical calculations at rotation rates of trillions of times per second and found that the phosphorus-hydrogen bond, which the molecule rotates about becomes shorter than the other two of these bonds. Moreover, two chiral forms of phosphine emerge depending on the sense of rotation. According to Yachmenev, the left-handed or right-handed version of the spinning phosphine can be selected with the help of a strong static electric field. However, the corkscrew-laser needs to be fine-tuned at realistic parameters to achieve the ultra-fast unidirectional rotation.

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