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Chemists find cyanide may have helped develop early life on Earth

The discovery sheds light on how life may have formed on Earth and could help scientists looking for life on other planets.

(CN) — The deadly gas known as cyanide may have played a significant role in the evolution of early life on Earth, according to new research.

A study published Thursday in Nature Chemistry details how the colorless deadly gas might have aided and kickstarted a process which is needed to create life as we know it.

Certain types of bacteria on Earth perform a set of chemical reactions called the reverse tricarboxylic acid cycle, or r-TCA cycle. This cycle metabolizes carbon dioxide and water into chemical compounds needed for life.

Many scientists believe that the molecules needed for early life were created by this process on the surface of Earth. However, the problem researchers have cited is that the r-TCA cycle uses a set of complex proteins that are not believed to have existed before life evolved.

This quandary spurred Ramanarayanan Krishnamurthy and his colleagues at Scripps Research Institute to look for an answer.

Other research has shown that specific metals can cause the needed reactions without the need for today’s proteins, but only under acidic and hot conditions that are not believed to have been common during the early days of Earth.

The Scripps Research chemists zeroed in on cyanide because the gas would have been present in the atmosphere of an early Earth, and the team began to think of ways that the gas could create the reactions needed to make organic molecules from carbon dioxide.

The team theorized a set of these reactions kicked off by cyanide instead of metal or proteins and tested their reactions in a test tube.

“It was scary how simple it was,” Krishnamurthy said in a statement. “We really didn’t have to do anything special, we mixed together these molecules, waited and the reaction happened spontaneously.”

One of the key findings of the study was that the reactions the team produced with cyanide were successful at room temperature and in a pH range that could have existed on an early Earth.

These findings broaden the scope of knowledge and insight into the chemistry that formed life on Earth and perhaps elsewhere in the galaxy.

“When we look for signs of life—either on the early Earth or on other planets—we base the search on the biochemistry we know exists in life today. The fact that these same metabolic reactions can be driven by cyanide shows that life can be very different,” Krishnamurthy said.

While it cannot be proven exactly what chemical procedures formed life on this planet, the cyanide reactions demonstrate a new and simpler set of theoretical conditions that could be consistent with the formation of life.

“It frees us up from saying there must be these metals and these extreme conditions,” Krishnamurthy said. “There could be life that evolves from this cyanide-based chemistry.”

Krishnamurthy and his colleagues with Scripps Research were joined in the study by Jayasudhan Yerabolu from the National Cancer Institute. The research was supported by a NASA exobiology grant, the Simons Foundation and a joint grant from the NSF and NASA Astrobiology Program under the Center for Chemical Evolution.

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