Chemical precursors of modern biomolecules may have arisen not only in deep-sea hydrothermal vents, but also in hot pools on the Earth's surface. A worldwide group of scientists led by academics from the Friedrich Schiller University in Jena, Germany, has successfully recreated the chemical reactions that may have taken place in this "primitive soup" in tests. They even discovered that one of the nucleobases representing the genetic code may have come from the surface of the planet.
Earth is about 4,6 billion years old, and life hasn't always thrived there. For the first 100 million years, our planet's atmosphere consisted predominantly of nitrogen, carbon dioxide, methane, hydrogen sulfide, and hydrogen cyanide, sometimes known as hydrocyanic acid. There was no free oxygen. Iron sulfide, which converts to iron oxide when exposed to oxygen, was stable under these conditions. However, biologically significant events could occur on the surface of iron sulfide, similar to those with various iron- and sulfur-based enzymes such as nitrogenases and hydrogenases.
Professor at the Institute of Inorganic and Analytical Chemistry, University of Jena. Wolfgang Weigand said, "We questioned ourselves: What happens when iron sulfide comes into contact with hydrocyanic acid in this primitive environment?"
“My colleague Prof. While working successfully with Christian Robl, we were lucky to accidentally find a highly reactive type of iron sulfide. This form had been discovered twice before in history, but was lost each time in the 1700s and 1920s. “Robert Bolney and Mario Grosch, two PhD students at the time, made a third discovery, in a sense,” he adds.
When iron powder is mixed with sulfur in water and slightly heated, the two chemists soon set off in an explosive reaction. mackinawite found that iron sulfide was formed. In the experiment with the "primitive soup", this mineral acted as a catalyst.
This method is likely to generate a letter from the genetic code.
“We added potassium cyanide, phosphoric acid and water to iron sulfide in a nitrogen atmosphere and heated the mixture to 80 degrees Celsius. Phosphoric acid converts potassium cyanide into hydrocyanic acid.
We then took gas samples from the atmosphere of the ships involved and analyzed them,” explains Weigand.
So the researchers found substances that may have served as chemical precursors for today's biomolecules.
The group publishes findings in the journal ChemSystemsChem, which include confirming the presence of acetaldehyde, a precursor to DNA building blocks, and thiols (called nucleosides) found as lipids in cell membranes.
According to Weigand, the discovery of adenine, a nucleobase, under these modest conditions, is one of the five letters of the genetic code of particular interest.
By isotope labeling, the team was able to show that the carbon of the compounds they discovered was actually given off by cyanide.
Weigand explains, “The carbon-98,9 isotope, which normally makes up 12% of the carbon that occurs in the environment, was absent in the potassium cyanide used in this experiment. It was actually the more stable and heavier isotope of carbon-13. We identified this isotope among the reaction products. This is how we were able to show with certainty that the carbon atoms in the compounds we found did indeed come from isotope-labeled potassium cyanide.”
Weigand expresses his gratitude for the help of the entire team around the world, saying that this type of job requires a lot of imagination and stamina. “And Mario Grosch and Robert Bolney showed that. Our collaboration with our colleagues at LMU Munich and the University of California, Irvine was equally excellent.”
Wolfgang Weigand is a prime example of the value of imagination and patience, especially in science.
Because in 2003, Prof. from the University of Jena. Günter Kreisel and Dr. from the Max Planck Institute for Biogeochemistry. Together with Willi Brand, he received the Thuringian Research Award for his paper entitled “A possible formation of prebiotic ammonia from molecular nitrogen on iron sulfide surfaces.”
Nearly two decades later, Weigand also showed that the first carbon molecules from which life finally emerged may have evolved under similar conditions from cyanide on the Earth's surface.