Cyanide and carbon monoxide are poisonous to humans but could have been the ideal tools for our own existence, and new evidence suggests that both were transported to Earth in meteorites.
Scientists have found in a type of carbon-rich meteorite calledcondrita carbonosa,that bombarded our planet before the appearance of life, compounds that contain cyanide, carbon monoxide and iron.
Not the first time cyanide and CO have been discovered in meteorites; but it is the first time that the two have been found to bind to iron to form stable compounds.It’s compelling proof that these compounds were present on Earth before the first single-celled organism transformed into the primordial ocean.And that means they could have contributed to the mysterious process that allowed life to emerge on Earth.
“When most people think of cyanide, they think of spy movies: a guy who swallows a pill, foams at the mouth, and dies, but cyanide is probably an essential compound for building the molecules necessary for it. life, “Boise State University biochemist Karen Smith told the journal Nature Communications published by the study.
Cyanide has been thought for years to play an important role in the production of organic compounds found in organisms, andHarvard scientists last year showed that cyanide can produce the simple sugars that make up RNA nucleotides, the building blocks of life.
But where did cyanide come from in Earth’s early days?
To try to solve this conundrum, the researchers devised a new method for extracting and measuring cyanide from ancient meteorites, and they used it on a variety of meteorite samples. They found that cyanide compounds were only present in a particularly organic-rich class of carbonaceous chondrites called CM chondrites. Others, including a meteorite from Mars, contained no detectable cyanide.
Using high-performance liquid chromatography-mass spectrometry, they analyzed the chemical composition of their samples and found two different compounds of iron, cyanide, and carbon monoxide, called iron cyano-carbonyl complexes.
“One of the most interesting observations from our study is that these complex iron cyano-carbonyl compounds resemble parts of the active sites of hydrogenases, which have a very different structure,” said biochemist Mike Callahan of Boise State University. (USA).
Hydrogenases are enzymes found in most modern bacteria and archaea that break down hydrogen. They are believed to date back to the dawn of life, when Earth’s atmosphere was possibly much richer in hydrogen than it is now.
Although the enzymes themselves are quite large in size, the active region within them where chemical reactions take place forms a much smaller organic-metal compound. This is what meteor cyanide compounds look like, the authors point out.
“Cyanide and carbon monoxide bound to a metal are unusual and rare in enzymes. Hydrogenases are the exception. When the structure of these iron cyano-carbonyl complexes in meteorites is compared to these active sites in hydrogenases, It makes you wonder if there was a link between the two, “says Karen Smith.
“It is possible that the iron cyano-carbonyl complexes were a precursor to these active sites and were later incorporated into proteins billions of years ago. These complexes probably also acted as sources of cyanide on early Earth,” continues the expert.
Thus, millions of years ago, when the Earth was in the process of cooling after having formed , it was subjected to a constant shower of meteorites that contained small cyanide compounds inside them, which served as a key piece for the formation of the ecosystem. of the atmosphere.
NASA currently has a spacecraft visiting the asteroid Bennu far from Earth. As part of your study, you will collect a sample and return it to Earth. The team hopes they can use the same technique to determine if Bennu could be linked to those CM chondrites for a long time.
Referencia: Karen E. Smith et al. Organometallic compounds as carriers of extraterrestrial cyanide in primitive meteorites, Nature Communications (2019). DOI: 10.1038/s41467-019-10866-x
