from the surprising-reactions dept.
Four billion years ago, the Earth looked very different than it does today, devoid of life and covered by a vast ocean. Over the course of millions of years, in that primordial soup, life emerged. Researchers have long theorized how molecules came together to spark this transition. Now, scientists at Scripps Research have discovered a new set of chemical reactions that use cyanide, ammonia and carbon dioxide—all thought to be common on the early earth—to generate amino acids and nucleic acids, the building blocks of proteins and DNA.
"We've come up with a new paradigm to explain this shift from prebiotic to biotic chemistry," says Ramanarayanan Krishnamurthy, Ph.D., an associate professor of chemistry at Scripps Research, and lead author of the new paper, published July 28, 2022 in the journal Nature Chemistry. "We think the kind of reactions we've described are probably what could have happened on early earth."
In addition to giving researchers insight into the chemistry of the early earth, the newly discovered chemical reactions are also useful in certain manufacturing processes, such as the generation of custom labeled biomolecules from inexpensive starting materials.
Earlier this year, Krishnamurthy's group showed how cyanide can enable the chemical reactions that turn prebiotic molecules and water into basic organic compounds required for life. Unlike previously proposed reactions, this one worked at room temperature and in a wide pH range. The researchers wondered whether, under the same conditions, there was a way to generate amino acids, more complex molecules that compose proteins in all known living cells.
[...] "We were expecting it to be quite difficult to figure this out, and it turned out to be even simpler than we had imagined," says Krishnamurthy. "If you mix only the keto acid, cyanide and ammonia, it just sits there. As soon as you add carbon dioxide, even trace amounts, the reaction picks up speed."
Because the new reaction is relatively similar to what occurs today inside cells—except for being driven by cyanide instead of a protein—it seems more likely to be the source of early life, rather than drastically different reactions, the researchers say. The research also helps bring together two sides of a long-standing debate about the importance of carbon dioxide to early life, concluding that carbon dioxide was key, but only in combination with other molecules.
Pulletikurti, Sunil, Yadav, Mahipal, Springsteen, Greg, et al. Prebiotic synthesis of α-amino acids and orotate from α-ketoacids potentiates transition to extant metabolic pathways, Nature Chemistry, 2022. DOI: 10.1038/s41557-022-00999-w