Indian scientist proposes new 'origin of life'

How did life begin on Earth? While there are several theories, an Indian scientist working in the US has proposed a new set of “origins of life,” chemical reactions that could lead to the development of amino acids – the building blocks of protein and DNA – from chemicals and gases present on the ancient Earth.

Four billion years ago, Earth looked very different, lifeless and covered by a vast ocean. Over millions of years, in that primordial soup, life arose.

There are several hypotheses about how life arose from inorganic molecules. Now, a team led by Ramanarayanan Krishnamurthy at the Scripps Research Institute, La Jolla, California has discovered a new set of chemical reactions that use cyanide, ammonia, and carbon dioxide — all thought to be common on the early Earth — to produce amino and nucleic acids. acids, building blocks of protein and DNA.

“We came up with a new paradigm to explain the shift from pre-biotic to biotic chemistry,” said Krishnamurthy, lead author of the study.

“Experiments led to the formation of amino acids produced by the modern citric acid cycle – glycine, alanine, aspartic acid and glutamic acid. In modern biology, amino acids are converted into proteins through polymerization and also into nucleobases,” Krishnamurthy, who graduated from Vivekananda College in Chennai and M.Sc from IIT-Bombay, told DH.

The experiment also required water abundant in carth and a chemical called alpha keto acid, which may have been formed by the ultraviolet light-mediated chemical reaction of carbon dioxide.

Alpha keto acids are precursors from which amino acids are produced in cells in the presence of nitrogen and enzymes.

In the 1920s Russian scientist Aleksandr Oparin and British scientist JBS Haldane independently proposed that life on Earth could have arisen from non-living matter through a process of “gradual chemical evolution”.

Three decades later, Stanley Miller and Harold Urey demonstrated in 1953 that it was indeed possible to spontaneously create the organic molecules necessary for life on primordial earth.

In their quest for answers to one of the most fundamental questions, Krishnamurhty, colleagues Sunil Pulletikurti and Mahipal Yadav, and Greg Springsteen of the Georgia Institute of Technology, Atlanta decided to use cyanide to trigger a chemical reaction that could convert prebiotic molecules and water into compounds. basic organic matter necessary for life.

They got a hint from their previous success when they used cyanide to drive another chemical reaction. The plan is to try cyanide, without enzymes, and see if it helps convert alpha-keto acids into amino acids.

Because they knew nitrogen would be needed in some form, they added ammonia — a form of nitrogen that would have existed in the early earth. Then, through trial and error, they discovered a third main ingredient: carbon dioxide. With this mixture, the team began to look at the formation of amino acids.

Unlike the reaction proposed earlier, this reaction works at room temperature and over a wide acid-base range.

“We expected it to be quite difficult to figure out, but it turned out to be simpler than we thought,” Krishnamurthy said. “If you just mix a keto acid, cyanide and ammonia, it will just be there. As soon as you add carbon dioxide, even a small amount, the reaction rate increases.”

Because the new reaction is relatively similar to what’s happening today inside cells—except driven by cyanide, not protein—it seems more likely to be the source of early life, rather than a drastically different reaction, the researchers said.

The study — published in Nature Chemistry last week — also helped bring together the two sides of a longstanding debate about the importance of carbon dioxide for early life, concluding that carbon dioxide was key, but only in combination with other molecules.

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