Astrobiological implications of the stability and reactivity of peptide nucleic acid (PNA) in concentrated sulfuric acid

Abstract

Recent renewed interest regarding the possibility of life in the Venusian clouds has led to new studies on organic chemistry in concentrated sulfuric acid. However, life requires complex genetic polymers for biological function. Therefore, finding suitable candidates for genetic polymers stable in concentrated sulfuric acid is a necessary first step to establish that biologically functional macromolecules can exist in this environment. We explore peptide nucleic acid (PNA) as a candidate for a genetic-like polymer in a hypothetical sulfuric acid biochemistry. PNA hexamers undergo between 0.4 and 28.6% degradation in 98% (w/w) sulfuric acid at ~25°C, over the span of 14 days, depending on the sequence, but undergo complete solvolysis above 80°C. Our work is the first key step toward the identification of a genetic-like polymer that is stable in this unique solvent and further establishes that concentrated sulfuric acid can sustain a diverse range of organic chemistry that might be the basis of a form of life different from Earth’s.