Four billion years ago, Earth looked very different than it does today. It was lifeless and covered by an immense sea. Over millions of years, life emerged from this primordial soup. For a long time, researchers have theorized how the molecules came together to give rise to this transition.
Now, scientists at Scripps Research have discovered a new set of chemical reactions that use ammonia, cyanide, and carbon dioxide — all thought to be common on early Earth — to make amino acids and nucleic acids, proteins and D. to generate the building blocks of NA.
“We came up with a new model to explain this shift from prebiotic to biotic chemistry,” says Raman Narayan Krishnamurthy, PhD, and an associate professor of chemistry at Scripps Research.
“We think the type of reaction we’ve described is probably what could have happened on the early Earth.” Krishnamurthy is lead author of the new paper, which was published July 28, 2022, in the journal Nature Chemistry.
In addition to giving scientists insight into the chemistry of early Earth, the newly discovered chemical reactions are also useful in some manufacturing processes. For Example, in the age of exceptionally marked bio molecules from cheap beginning materials.
Earlier this year, Krishnamurthy’s team showed how cyanide can activate chemical reactions that turn prebiotic molecules and water into the basic organic compounds needed for life.
It worked at room temperature and over a wide pH range, unlike previously proposed reactions. The scientists wondered if there was a way to produce amino acids, the more complex molecules that make up proteins in all living cells, under the same conditions.
In cells today, amino acids are produced from precursors called α-keto acids using both nitrogen and special proteins called enzymes. Scientists have discovered evidence that α-keto acids may have existed early in Earth’s history.
However, many researchers have hypothesized that before the advent of cellular life, amino acids may have been formed from a completely different precursor, aldehydes, rather than α-keto acids, since the catalysts to do the change didn’t yet exist.
But this idea has sparked a debate about how and when the transition from aldehydes to α-keto acids as the key building blocks of amino acids occurred.
Following their success in using cyanide to drive other chemical reactions, Krishnamurthy’s group suspected that cyanide, even without enzymes, could help convert α-keto acids to amino acids. Because they knew that nitrogen would be needed in some form, they added ammonia—a form of nitrogen that would have been present on the early Earth.
Then, at that point, through experimentation, they found a third key fixing: carbon dioxide. With this compound, they immediately started to notice the amino corrosive theme.
“We were anticipating that it should be very hard to sort out, and it ended up being simpler than we naturally suspected,” says Krishnamurthy. “In the event that you simply blend keto corrosive, cyanide and smelling salts, it stays there. As you add carbon dioxide, even trace amounts, the reaction speeds up.”
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Because the new reaction is relatively similar to what happens inside cells today—except powered by cyanide instead of protein—it seems more likely to be the source of early life than a vastly different reaction, the scientists say.
The research also helps bring together two sides of a long-running debate about the importance of carbon dioxide in early life, concluding that carbon dioxide was key, but only in combination with other molecules.
do In the process of studying their chemical soup, Krishnamurthy and his colleagues discovered that a byproduct of this reaction is orotate, a precursor to the nucleotides that make up DNA and RNA.
This shows that the same primordial soup, under the right conditions, could have given rise to a large number of the molecules that are needed for the essential elements of life.
“What we keep up with that ought to do next is continue to investigate what kind of science this mix could make,” says Krishnamurthy. Can amino acids start making small proteins? Could one of these proteins come back and start acting as an enzyme to make more of these amino acids?
