Chemists have induced uniform chirality

Date:
June 8, 2020
Source:
Martin-Luther-Universita"t Halle-Wittenberg
Summary:
Chirality is a fundamental property of many organic molecules
and means that chemical compounds can appear in not only one
form, but in two mirror-image forms as well. Chemists have now
found a way to spontaneously induce chirality in crystalline,
liquid-crystalline and liquid substances, without requiring any
external influence. The findings could be significant for the
development of new active substances and for materials science.



FULL STORY ========================================================================== Chirality is a fundamental property of many organic molecules and
means that chemical compounds can appear in not only one form, but in
two mirror-image forms as well. Chemists at Martin Luther University Halle-Wittenberg have now found a way to spontaneously induce chirality in crystalline, liquid- crystalline and liquid substances, without requiring
any external influence.

The findings could be significant for the development of new active
substances and for materials science. The study was recently published
in Chemical Science an international journal published by the Royal
Society of Chemistry.


========================================================================== Chirality is found in almost all molecules occurring in nature. "Molecules
are spatial arrangements of interconnected atoms. Many molecules, however,
have not only one form, but at least two," explains Professor Carsten Tschierske, a chemist at MLU. When these forms are mirror images of each
other it is called chirality.

Both mirror-image forms are produced in equal numbers during normal
chemical reactions in the laboratory. "However, things occur differently
in nature: carbohydrates, amino acids and nucleic acids only have one
dominant form," explains Tschierske. And with good reason: for example,
nucleic acids carry information about our DNA. Even the slightest changes
to our genetic material can lead to serious diseases. "If each nucleic
acid had two forms, the structure of our DNA would be chaotic because
there would be too many possible variations. Life as we know it would
be impossible," states Tschierske.

The exact process that once created the uniform chirality in these
molecules is still unknown. Furthermore, it was long assumed that mixtures
of mirror-image molecules can only separate spontaneously in crystalline materials. However, in a study published in Nature Chemistry in 2014, Tschierske's team was able to show that this phenomenon of chiral cleavage
can also be observed in liquids.

"This is significant because the origins of life are found in liquid
aqueous systems," explains the chemist.

In this new study, his team went one step further. The researchers found a
way to not only generate chirality in liquids, but also to specifically transfer it to liquid-crystalline and crystalline materials without
incurring any losses.

To do this, the scientists used benzil, a molecule that is normally
achiral, in other words, has no mirror image, but can be twisted in such
a way to make it chiral. "We already knew that benzil could crystallize
in a uniform chiral shape," says Tschierske. By modifying this molecule,
the researchers were able to spontaneously generate molecules with
uniform chirality even in a liquid state -- and to maintain this state
during conversions. "These findings contribute to our understanding of
the formation of uniform biochirality. At the same time, our approach
can also be used to synthesize chiral molecules and materials -- without requiring expensive chiral precursors," explains Tschierske.

The study conducted in Halle contributes to our understanding of how
uniform biochirality might have developed millions of years ago. At
the same time, it provides new insights into how chirality can be
spontaneously generated. There is a broad range of applications:
for example, chiral substances can be used as active ingredients in
medicine. The research findings could also be used in a wide variety of materials, for example in optical information processing.


========================================================================== Story Source: Materials provided by Martin-Luther-Universita"t_Halle-Wittenberg. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Tino Reppe, Silvio Poppe, Xiaoqian Cai, Yu Cao, Feng Liu, Carsten
Tschierske. Spontaneous mirror symmetry breaking in benzil-based
soft crystalline, cubic liquid crystalline and isotropic liquid
phases.

Chemical Science, 2020; DOI: 10.1039/D0SC01396J ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200608104733.htm

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