Astrophysicists at the National Radio Astronomy Observatory have discovered a complex organic compound in interstellar space that is chiral. Scientists have proposed a synthesis mechanism for such a molecule that can help solve the problem of homochirality of life on Earth. The research is published in the journal Science.
Many organic molecules have their own mirror copies, with which they cannot be mentally combined. In this they resemble the right and left hand. Such a molecule is said to have chirality (from the ancient Greek χειρ - "hand"), and this property is characteristic of most biologically significant compounds. Similar forms have been found in meteorites that have fallen to Earth, as well as in comet matter, but they have not yet been found in interstellar space.
Image: eurekalert.org
Astrophysicists using the highly sensitive 100-meter Green Bank radio telescope were able to find the first complex organic molecule with chirality in space - propylene oxide. The substance lies near the center of the Milky Way in a star-forming cloud of dust and gas known as Sagittarius B2.
Complex organic molecules form in interstellar clouds in several ways. For example, individual compounds can collide with each other and merge to form more complex substances. However, when large molecules such as methanol appear, this process becomes less efficient. To go further and get propylene oxide, small pieces of ice, according to scientists, should serve as a kind of substrate on which small molecules are deposited. The latter can connect with each other, synthesizing more complex structures. The resulting compounds evaporate from the ice pellets and enter the space environment, where they enter into chemical reactions with other substances.
The data obtained, however, do not allow determining which of the chiral forms (enantiomers) of propylene oxide was found. Enantiomers have the same melting, boiling and freezing points and absorption spectra. However, astrophysicists believe that studying how polarized light rays interact with molecules will help to find out.
The discovery of propylene oxide paves the way for further experiments that should help to understand how and where chiral compounds are formed, as well as to solve the problem of homochirality. Since every living thing on Earth contains molecules of only one chiral form, it is not clear how the choice was made in its favor. At the same time, DNA, for example, could not be stable if it consisted of both "left-handed" and "right-handed" enantiomers. Scientists believe their discovery suggests that the formation of organics in outer space played an important role in homochirality.
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