The emergence of the first biochemical molecules on Earth was heavily influenced by the sun’s energy and catalysts that accelerated chemical reactions. A recent study published in the journal Angewandte Chemie reveals that a solid formed from ammonia and methane plasma can utilize light energy to facilitate amine-to-imine conversions. This process is believed to have played a crucial role in the creation of the earliest biomolecules.
Around three to four billion years ago, prior to the proliferation of life, the initial biomolecules were being synthesized. These chemical reactions relied on catalysts, and researchers, led by Xinchen Wang from Fuzhou University in China, have now discovered that the primordial atmosphere itself could have served as a source of these catalysts.
By employing methane and ammonia gases, which were likely abundant in the hot gas mixture enveloping the ancient Earth during the Archean era, the team employed chemical vapor deposition to generate nitrogenous carbon compounds with catalytic potential. They observed that, within a reaction chamber, molecules precipitated out of an ammonia and methane plasma onto a surface, rapidly growing and forming a solid nitrogenous carbon polymer resembling nitrogen-doped graphite.
The incorporation of nitrogen atoms in an irregular fashion provided catalytically active sites to this polymer, along with an electron structure that allowed it to be excited by light. To verify the substance’s ability to reduce or oxidize other substances under the influence of light, the researchers conducted further experiments.
During the early stages of Earth, one of the most significant reactions might have been the formation of imines. Imines, also known as Schiff bases, are dehydrogenated versions of amines—compounds comprising carbon, nitrogen, and hydrogen. It is widely speculated that imines may have played a role in the formation of the first hereditary molecules of ribonucleic acid (RNA) on primordial Earth. Wang and his team successfully demonstrated that their plasma-generated catalyst can convert amines to imines solely using sunlight.
The team suggests that carbon nitride-based photocatalysts, such as the substance generated from plasma, could have persisted for millions of years, producing crucial chemical intermediates. Moreover, they may have served as a source of carbon- and nitrogen-containing compounds. By establishing the possibility of creating such a catalyst using only the gases and conditions present in the early Earth’s atmosphere, this study sheds new light on the potential evolutionary pathway of biomolecules.