Piecing together the story of life’s origin just got more colorful. (I couldn’t help using this trite journalistic phrase, sorry.) Prussian blue, the famous blue color used in dyes and blueprints, is also one of the oldest complex organic compounds known. Now, thanks to recent research at the Astrobiology Centre (INTA-CSIC, Madrid, Spain), it appears Prussian blue may have been involved with the creation of life on Earth.
The substance Prussian blue is an intense dark blue, but to think about its role in organic chemistry – forget the color. In fact, call it by another name: hexacyanoferrate, an inorganic compound of iron and cyanide. Other studies (prior to this one) have shown that Prussian blue can be formed by the conditions that supposedly existed on pre-biotic Earth: A hot, methane atmosphere, charged with frequently lightning strikes. Working the other way around, scientists at the Astrobiology Centre exposed Prussian blue to high acidity (ammoniac at ph12), warm temperature (70-150C), in a damp anoxic environment (moist but without oxygen) – also conditions believed to have been common in the early stages of Earth’s history.
“We have shown that when Prussian blue is dissolved in ammoniac solutions it produces hydrogen cyanide, a substance that could have played a fundamental role in the creation of the first bio-organic molecules, as well as other precursors to the origin of life, such as urea, dimethylhydantoin and lactic acid”, said Marta Ruiz Bermejo, lead author of the study…
Urea is considered to be an important reagent in synthesising pyrimidines (the derivatives of which form part of the nucleic acids DNA and RNA), and it has been suggested that hydantoins could be the precursors of peptides and amino acids (the components of proteins), while lactic acid is also of biological interest because, along with malic acid, it can play a role in electron donor-recipient systems.
Ruiz Bermejo concludes that Prussian blue “could act as a carbon concentrator in the prebiotic hydrosphere, and that its wet decomposition in anoxic conditions could liberate hydrogen cyanide and cyanogen, with the subsequent formation of organic molecules and iron oxides”.
There are obviously many more pieces of the ‘chain of development’ for the beginning of life to be discovered, but the Prussian blue research provides a plausible hypothesis for the formation of at least some of the essential organic compounds.