Three synthesized peptides folded into omega loops in concentrated sulfuric acid

Hydrolysis needs water. Concentrated sulfuric acid holds very little free water, and that scarcity is the reason Seager's group has given for why bonds in amino acids and nucleic acid bases hold up in the medium ^[5][4]. The earlier claim was survival. Folding is a bigger claim, because a fold is a specific geometry and survival is only the absence of damage.

The experiment behind it is small and controlled. The team synthesized three peptides and put each into water and into concentrated sulfuric acid; in water they laid out as flat sheets and did not fold, and in the acid all three folded ^[7]. Three of three in acid, none of three in water ^[22]. The structural claim rests on three molecules.

"This shouldn't even be happening, and yet it does," said Janusz Petkowski, a coauthor and astrobiologist at Wroclaw University of Science and Technology ^[9].

The structures come from nuclear magnetic resonance, in which a magnetic field is applied to the sample and the realignment of the atoms is recorded; the modeling software the team used to interpret those measurements was not designed for sulfuric acid media ^[14]. Martin Rahm, a quantum chemist and astrobiologist at Chalmers University of Technology who was not involved in the work, still describes the spectra as showing something ordered. "Seemingly, this is not like a random coil," he said ^[12]. He also put the weight on the split outcome: "The cool part is they find some peptides are stable, some are not" ^[11]. Petkowski, who calls concentrated sulfuric acid a "severely understudied" solvent, said the team adopted controls to avoid bias in its structural models, and that loops of slightly different curvature turned up in all three peptides under every assumption the team varied ^[15][16].

Whether the loops do anything biochemically is a separate question, and the study does not point that way ^[19]. Rahm treats the sameness of the result as a possible problem. "If they all fold into the same thing (omega loops), that might actually be bad for life," he said, since none of the peptides took up the other structures life as we know it uses, such as sheets and helices ^[17][18].

Venus's surface sits near 467 C at about 93 times Earth's sea-level pressure ^[1]. The clouds are the part astrobiologists keep coming back to, and they are made almost entirely of sulfuric acid ^[2]; in their upper reaches, liquids and organic molecules delivered by meteorite showers can persist ^[3]. The question some in the field want tested there is whether an organism could depend on concentrated sulfuric acid in place of water ^[21]. "There is a lot of work ahead of us," Petkowski said ^[20].