Researchers have discovered a new clue in the search for the origin of life by showing that peptides can form on dust under conditions such as those prevailing in outer space. These molecules, which are one of the basic building blocks of all life, may therefore not have originated on our planet at all, but possibly in cosmic molecular clouds.
Chains of amino acids
All life as we know it consists of the same chemical building blocks. These include peptides, which perform various completely different functions in the body — transporting substances, accelerating reactions or forming stabilising scaffolds in cells. Peptides consist of individual amino acids arranged in a specific order. The exact order determines a peptide’s eventual properties.
How these versatile biomolecules came into being is one of the questions about the origin of life. Amino acids, nucleobases and various sugars found in meteoroids, for example, show that this origin could be extraterrestrial in nature. However, for a peptide to be formed from individual amino acid molecules, very special conditions are required that were previously assumed to be more likely to exist on Earth.
The first step requires water, while for the second step, there must be no water
«Water plays an important role in the conventional way in which peptides are created,» says Dr Serge Krasnokutski of the Laboratory Astrophysics and Cluster Physics Group of the Max Planck Institute for Astronomy at the University of Jena. In this process, individual amino acids combine to form a chain. For this to happen, one water molecule must be removed each time. «Our quantum chemical calculations have now shown that the amino acid glycine can be formed through a chemical precursor — called an amino ketene — combining with a water molecule. Put simply: in this case, water must be added for the first reaction step, and water must be removed for the second.»
With this knowledge, the team led by the physicist Krasnokutski has now been able to demonstrate a reaction pathway that can take place under cosmic conditions and does not require water.
Story Source: Materials provided by Friedrich-Schiller-Universitaet Jena. Original written by Marco Korner. Note: Content may be edited for style and length.