Cyanide could play a key role in the emergence of life on Earth
Yesterday, a chemical compound known as cyanide (although it would be more correct to talk about a group of substances - cyanides containing the CN group) is associated by many with a very toxic colorless gas, a deadly poison and even chemical weapons. Indeed, many cyanides are toxic. Cyanides, as well as their derivatives, were used during the Second World War as a chemical warfare agent, and they still help in the fight against many pests: mice, rats, coyotes, opossums, ants.
However, it seems that cyanide can not only bring death, but also contribute to the origin of life. At least that's what chemists at The Scripps Research Institute think. In a new study published in the journal Nature Chemistry, scientists have shown how cyanide could have contributed to the synthesis of organic compounds from carbon dioxide four billion years ago, in the time of the early Earth.
When we look for signs of life — whether on early Earth or on other planets — we base our search on biochemistry, which we know exists in modern organisms. The fact that the same metabolic reactions can catalyze cyanide shows that life can take many different forms," says Ramanarayanan Krishnamurthy, Ph.D., assistant professor of chemistry at the Scripps Institute and lead author of the new paper.
Some modern bacteria, such as green sulfur bacteria, use a series of chemical reactions known as the reverse cycle of tricarboxylic acids (aka the reverse Krebs cycle or the Arnon cycle) to synthesize organic compounds from carbon dioxide and water. At the same time, for the course of all reactions, a dozen enzymes are needed that catalyze the transformations of tricarboxylic acids. Many scientists believe that the reverse Krebs cycle took place on the early Earth when the first organic substances were created. But this hypothesis has a serious problem: at the time of the early Earth (more than 3.5 billion years ago), there were no complex proteins that catalyze today the reactions of the reverse cycle of tricarboxylic acids.
Krishnamurti and his colleagues at the Scripps Institute decided to find out whether any simple molecule present in the atmosphere of the early Earth could catalyze the same reactions. And it was found — a cyanide molecule. The scientists hypothesized what reactions cyanide might catalyze, and then tested their guesses in an experiment. As a result, everything turned out: reactions similar to the reactions of the krebs reverse cycle took place in the presence of cyanide, which played the role of an electron carrier between molecules. At the same time, everything worked in a wide range of temperatures (from room to 80 ° C) and pH values (3-9).
"It was scary how easy it was," Krishnamurti said. "We really didn't need to do anything special: we mixed these molecules, waited, and the reaction happened spontaneously."
The author adds that it is impossible to know exactly what chemical processes really took place on the early Earth. Nevertheless, the discovery of new pathways of reactions will expand the understanding of the potential chemistry of life on our and other planets.
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