(ORDO NEWS) — Research has shown that amino acids can form peptides – the building blocks of life – in space, potentially explaining the origin of life.
According to previous theories, amino acids, brought by comets and meteorites, seeded the Earth in the early stages of its formation. Then the transformation of these acids into peptides occurred after their arrival, and not before. A new study refutes this notion, arguing that such a transformation can take place in space.
How did life begin? This is one of the most fundamental questions that has been asked throughout the history of mankind by religious figures, philosophers, and scientists. But as of 2022, there is no single answer to it.
For scientists, this question is primarily related to the origin of single-celled organisms, which, judging by the fossils, appeared several hundred million years after the formation of the planet.
This is mainly due to the fact that it was these single-celled organisms that laid the foundation for the evolutionary process based on natural selection, which led to the emergence of a wide range of complex life forms that we see today. However, the question of how these very first organisms originated remains unanswered.
Now a team of researchers from the Friedrich Schiller University of Jena and the Max Planck Institute for Astronomy have shown that in the harsh environment of space, amino acids can be converted into more complex peptides, a key component of life.
According to a press release announcing the new study, “Amino acids, nucleobases and various sugars found in meteoroids, for example, show that their origin may be extraterrestrial. However, the formation of a peptide from individual amino acid molecules requires special conditions, which, as previously thought most likely exist on Earth.”
Until now, these conditions have usually included the presence of water, primarily because every time a basic amino acid combines with another to form a peptide chain, a water molecule must be removed.
“Water plays an important role in the usual way to create peptides,” explained Dr. Serge Krasnokutsky of the Institute’s Laboratory Astrophysics and Cluster Physics group.
“Our quantum chemical calculations have shown that the amino acid glycine can be formed by combining a chemical precursor – aminoketone – with a water molecule. Simply put, in this case, water must be added for the first stage of the reaction, and water must be removed for the second.”
This contradictory set of circumstances forced researchers to look at the origin of peptides in a completely different, shockingly simpler way, by eliminating one of the two steps and water from the process altogether.
“Instead of going through the chemical pathway that produces amino acids, we wanted to find out if amino ketone molecules could instead be formed and connected directly to form peptides,” Krasnokutsky said.
“And we did it under the conditions that prevail in cosmic molecular clouds, that is, on dust particles in a vacuum, where the corresponding chemicals are abundant: carbon, ammonia and carbon monoxide.
To test this hypothesis, the team used an ultra-high vacuum chamber, which allowed them to simulate the environment of space, dropping it down to about one quadrillion normal air pressure and minus 263 degrees Celsius. Inside the chamber, they placed artificial substrates that served as models for dust particles like those found in interstellar space.
When the researchers injected molecules of carbon, ammonia, and carbon monoxide onto the surface of simulated dust particles, they observed a simultaneous conversion of individual glycine amino acids into a polyglycine peptide chain. And all this without the addition of water.
“Studies have shown that under these conditions, peptide polyglycine was formed from simple chemicals,” says Krasnokutsky. “So these are chains of the very simple amino acid glycine.”
“And we observed different lengths,” Krasnokutsky added of the complexity of the peptides observed in their experiments. “The longest samples consisted of eleven amino acid units.”
According to the research team, the success of this anhydrous, one-step conversion is based primarily on one “extremely reactive” amino acid, the amino ketone.
“The fact that the reaction can take place at such low temperatures is due to the fact that the aminoketone molecules are extremely reactive,” says Krasnokutsky. “They bond to each other in an efficient polymerization. The product of this is polyglycine.”
The researchers say they were surprised that this polymerization of aminoketone could occur under such extreme space-like conditions, primarily because of the energy barrier that must be overcome for this transformation.
However, they now suspect that something may be happening on a very small scale, a phenomenon known as quantum tunneling, which helps an amino acid bypass this energy barrier and form true peptide chains.
“Perhaps a special effect of quantum mechanics helps us with this,” says Krasnokutsky. “At this particular stage of the reaction, the hydrogen atom changes its place. However, it is so small that, being a quantum particle, it could not overcome the barrier, but simply was able to cross it, so to speak, with the help of a tunneling effect.”
Published in the journal Nature Astronomy, this is just one study. But if the results are confirmed, they will show that amino acids most likely did not need early Earth conditions to combine into complex molecules.
Instead, these conditions may already exist in interstellar space, and the early Earth just needed to cool (and calm down) enough for these building blocks of life to take hold. If this is true, then the question of the “origin of life” may remain open, but it also means that there may be a new place to look for an answer.
“Now that it has become clear that not only amino acids, but also peptide chains can be created in space conditions,” the press release says, “perhaps, when studying the origin of life, we will have to pay attention not only to the Earth, but also to space.”
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