Wednesday , May 5 2021

Innovative experimental system can create mirror molecules



When rotated rapidly, symmetrical molecules like phosphine (PH) lose their symmetry: The bond between phosphorus and hydrogen along the axis of rotation is shorter than the other two such bonds. Depending on the direction of rotation, two mirror-inverse versions of the molecule are formed. Credit: DESY, Andrey Yachmenev

To explore molecular handedness mystery in nature, researchers have suggested a new experimental system for creating customized mirror molecules for analysis. The technique can make common molecules spin as fast as they lose their normal symmetry and shape and form mirrored versions of each other. The research group from DESY, Universität Hamburg and University College London led by Jochen Küpper describes the innovative method in the journal Physical review letter. The further investigation of handedness or chirality (from the old Greek word by hand, "cheir") not only improves the insight into the effects of nature but can also pave the way for new materials and methods.


As your hands there are many molecules in nature in two versions that are mirror images of each other. "For unknown reasons, life, as we know it on earth, predominates almost exclusively left-handed proteins, while the genome is organized as the famous right-handed double helix," explains Andrey Yachmenev, who leads this theoretical work in the Küppers group at the Free-Electron Laser Science Center CFEL). "For more than a century, scientists have been unraveling the secrets of this handedness in nature, which not only affects the living world mirror versions of some molecules alters chemical reactions and changes the behavior of the material." For example, the right hand version of the caravone (C10hrs14O) gives the kargen its distinct flavor, while the left-handed version is a key factor for the taste of spearmint.

Handedness, or chirality, occurs only naturally in certain types of molecules. "However, it can be artificially induced in so-called symmetric molecules," said co-author Alec Owens of the Center for Ultrafast Imaging (CUI). "If these molecules move fast enough, they lose their symmetry and form two mirror shapes, depending on their rotation. So far, little is known about this phenomenon of rotational induced chirality, as hardly any systems of its generation exist that can be followed experimentally."

The Küppers team has now calculated a way to achieve this rotation-induced chirality with realistic parameters in the laboratory. It uses corkscrew-shaped laser pulses called optical centrifuges. For the example of phosphine (PH3) shows their quantum mechanical calculations that at rotational speeds of trillions times per second, the phosphorus hydrogen bond that the molecule rotates around becomes shorter than the other two of these bonds and depending on the mode of rotation two chiral forms of phosphine appear. "Using a strong static electric field, the left or right handed version of the spinning phosphine can be selected," explains Yachmenev. "In order to still achieve the ultrasound rotational rotation, the corkscrew must be fine-tuned, but to realistic parameters."

This system promises a whole new way through the glass in the mirror world, as it would in principle also work with other heavier molecules. In fact, these would actually require weaker laser pulses and electric fields, but were just too complex to be solved in these first stages of the survey. However, since phosphine is highly toxic, such heavier and even slower molecules would be preferred for experiments.

The proposed method could deliver tailor-made mirror molecules and the study of their interaction with the environment, for example with polarized light, would help further penetrate into the mystery's handedness in nature and investigate its possible utilization, expects Küpper, who is also a professor of physics and chemistry at the University of Hamburg: "To facilitate a deeper understanding of the phenomenon of handedness in this way can also contribute to the development of chirality based tailored molecules and materials, new material states and the potential utilization of rotational induced chirality in new metamaterials or optical devices."


Explore further:
Modified optical centrifuges have the potential to open new ways of studying super rotors

More information:
Alec Owens et al., Climbing the rotation steps to chirality, Physical review letter (2018). DOI: 10,1103 / PhysRevLett.121.193201

Journal reference:
Physical review letter

Provided by:
Deutsches Elektronen-Synchrotron


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