Peptides can be stable in concentrated sulphuric acid: study

Researchers have found that certain peptides — short chains of amino acids that make up proteins — are not only stable in 98% concentrated sulphuric acid but also fold into the complex 3D shapes required to perform the functions central to life.

Thus, the findings, published Proceedings of the National Academy of Sciences on September 4, defy the assumption that concentrated sulphuric acid is a bane for the building blocks of life. Scientists had previously found nucleic acid bases and amino acids to be stable in the same solvent; this is the first time a macromolecule important to biology has been shown to be capable of the same feat.

Normally, strong acids break down peptides in a process called hydrolysis; as the name suggests, water molecules break down one or more important bonds. Since 98% sulphuric acid contains almost no water, the reaction that would normally shred the peptide bonds can’t happen, allowing the peptides to remain  stable for several weeks at room temperature.

Using nuclear magnetic resonance spectroscopy, the researchers found that these peptides folded into a specific shape called an omega loop, using the sulphuric acid molecules themselves as a kind of scaffolding to help maintain the shape. This is however a significant departure from how proteins behave in water, where they typically form different structures like helices or sheets.

The findings are important for the search for life beyond the earth. For example, Venus is covered in clouds of concentrated sulphuric acid, which scientists previously assumed were too harsh an environment to host any complex chemistry. The new findings question this assumption.