The first key stages of the origin of life occur under various conditions

The potential precursors of life on Earth come from a variety of complex mixtures. According to a team of scientists, this could indicate the development of building blocks essential for the formation of genetic molecules for the origins of life on Earth.

Genetic molecules can store and reproduce information and may have been decisive for the origin of life, but we do not know how they came from the complex chemical environments that existed at the beginning of the Earth. New results, published this week in the journal Scientific reports, suggest that the answer could begin with nitrogen heterocycles, ringed molecules that are thought to be common on young Earth and elsewhere in the solar system. Several types of heterocycles serve as nucleotide bases, or subunits, for DNA and RNA, genetic molecules used by life as we know it.

"One of the challenges of studying the origins of life is to decipher what reactions were key steps," said Christopher House, professor of geoscience at Penn State. "Our work here has identified the next most likely steps that these molecules could and should take."

A team of researchers has found that nitrogenous heterocycles may have been the basis for life in a series of tests that have generated complex chemical mixtures, such as those possibly created by flashes crossing the primitive earth's atmosphere. Dozens of different heterocycles produced similar primitive genetic precursors, even when the composition of the atmosphere was modified as part of the study.

"The real surprises were that so many different molecules of this type proved to be reactive and that they formed the same stage, regardless of the simulated atmosphere we used," House said. is also director of the Penn State Astrobiology Research Center. the NASA Pennsylvania Space Grant consortium.

The results support the hypothesis that simpler genetic structures could precede the formation of DNA and RNA and suggest that similar prebiotic reactions could occur elsewhere in the solar system.

Unlike previous studies, which had explored similar reactions in isolated conditions, the team used organically complex mixtures that better simulate early Earth chemistry, without knowing whether the reactions would represent a constructive step towards life or a dead end.

In the study, the heterocycles reacted in the complex mixture to form chemically reactive side chains, structures connecting heterocycles to each other and facilitating the formation of more complex molecules, the researchers said.

These modified heterocycles could serve as peptide nucleic acid subunits (PNA), a proposed RNA precursor. The fact that they formed so easily under different atmospheric conditions supports the theory that PNAs may have formed on the prebiotic Earth.

"Our results suggest the possibility of ANP on the Early Earth since we have observed many robust synthetic pathways for some of its components," said Mike Callahan, assistant professor of chemistry at Boise State University.

The results also have implications for similar genetic precursors on other worlds.

"Organic substances reacting with heterocycles and forming these side chains have also been identified in the interstellar medium, comets and even in Titan's atmosphere," said Laura Rodriguez, who led the research as a PhD student. in geosciences at Penn State. "And since the reactions were robust in complex mixtures in a wide range of conditions, our results could have implications for the formation of ANP beyond the Earth."

Karen Smith, Principal Investigator, and Melissa Roberts, a graduate student at Boise State, also contributed to this research.

This program was funded by the exobiology program of NASA, NASA's Astrobiology Institute through the Goddard Center for Astrobiology and the Penn Astrobiology Research Center. State.