Peptides adopt stable omega-loop structures in concentrated sulfuric acid
TL;DR
Using NMR spectroscopy, it is shown that three peptides adopt stable, well-defined folded structures in concentrated sulfuric acid, an extreme solvent environment that has been long assumed to be incompatible with biomolecules.
Abstract
Significance Concentrated sulfuric acid is widely regarded as destructive to Earth-like biochemistry. Recent studies, however, show that an increasing number of biomolecules, including nucleic acid bases, amino acids, and lipids, remain stable in this solvent. A central question is whether such stability extends to macromolecules that require persistent three-dimensional structures for function. Using NMR spectroscopy, here we show that three peptides adopt stable folded structures in concentrated sulfuric acid. With only trace water present, acid-catalyzed hydrolysis is suppressed. The peptides form compact Ω-loop conformations stabilized by solvent-mediated interactions and intramolecular hydrogen bonding. The persistence of folded peptides in concentrated sulfuric acid expands the range of liquid environments that may support macromolecular structure and function, including Venus clouds and exoplanets.