An unusual type of chemical reaction can give rise to peptides in space. These are short chains of amino acids from which proteins are also constructed. The study, published in Nature Astronomy, shows a new way in which cosmic dust grains can form relatively complex precursors of biomolecules for the origin of life at very low temperatures. As the team led by Serge Krasnokutski from the Max Planck Institute for Astronomy reports, individual carbon atoms serve as a "molecular glue" between carbon monoxide and ammonia, two of the most common molecules in interstellar molecular clouds. This produces the molecule aminoketene – which differs from the amino acid glycine only by a missing water molecule. Simple peptides from several glycine molecules were then formed directly from this molecule in the experiment of the experts.
Above all, the new reaction solves the problem that amino acids do not easily get together to peptides. To do this, a water molecule must be split off, which requires energy that is not available in the cold of space. This hurdle falls away when the forerunner, here the aminecot, does not contain the water molecule at all. With the help of quantum chemical invoices, the working group showed that aminecets are also created in two steps under the conditions on the surface of dust grains without additional energy supply. First, the isolated, very aggressive carbon atom with ammonia reacts to the reactive intermediate product H2NCH, which spontaneously combines with carbon monoxide to the amo -cuckled H2NCH = CO.
In an experiment, Krasnokutski's team then steamed the three reaction partners onto a test surface cooled to ten degrees above absolute zero, which simulates a grain of dust in interstellar space. Using an infrared spectrograph that identifies molecules based on the light they absorb, it showed that aminokets are indeed formed under these conditions. However, as it turned out, it is still too cold for the molecules to combine further to form peptides. Only when the working group had slowly heated the sample to 110 Kelvin did the typical signals of peptides become apparent in the instrument. This warming could, for example, be caused by a nearby star.
The new reaction extends the list of well -known mechanisms that can create complex molecules for the origin of life in interstellar space. In addition, it shows that well -known building blocks of life may be available in large quantities on interstellar dust grains and that amino acids do not have to arise so that peptides arise. The work of the team also fits into a growing series of evidence that the splitting of water when connecting smaller precursor modules is not the great obstacle to the formation of larger biomolecules in the origin of life than it was long. There have also been concepts for a while for the nucleic acids, the building blocks of the genetic material, how they could have been created without splitting up water. However, the study does not answer the question of the "handling" of amino acids and proteins - the amino acid glycin does not appear in two mirror -image forms.
