Within the seek for life past Earth, scientists have lengthy targeted on one key ingredient: liquid water. However astrobiologist Sara Seager and her workforce on the Massachusetts Institute of Expertise aren’t satisfied that water is the one solvent capable of hosting life. They’ve simply proven that peptides—quick chains of amino acids—not solely survive in highly concentrated sulfuric acid however tackle steady 3D conformations too (Proc. Natl. Acad. Sci. U.S.A. 2026, DOI: 10.1073/pnas.2618039123). Their findings may have implications for the seek for biomolecules in Venus’s acidic clouds and past.
The challenge began with a brand new collaboration between Seager and the MIT chemist Mei Hong. Within the years since discovering phosphine signals in Venusian clouds, Seager had been working her method by the constructing blocks of life—nucleic acids, amino acids, and lipids—to see if any survived concentrated acid publicity. She was excited by the outcomes; a variety of these compounds are steady within the resolution.
Then she hit a wall. Seager was utilizing polarized gentle to attempt to perceive the 3D construction of an artificial analog of DNA in acid. “Then we went to small peptides to crack that,” she says. However the spectra weren’t what she anticipated. “We wanted Mei’s experience to determine what was actually happening.”
Hong was wanting to collaborate. Her group has solved quite a few protein constructions utilizing nuclear magnetic resonance (NMR) spectroscopy. Hong additionally had the proper take a look at topic: a brief peptide she had analyzed intimately for a earlier origins-of-life examine. She says she thought, “I’ve the high-resolution construction [in water]. Let me put it in sulfuric acid and simply see the way it behaves.”
The prevailing knowledge is that peptides are incompatible with acidic options as a result of acids catalyze hydrolysis of peptide bonds, thus shortly breaking the polymer chain right into a slurry of amino acid hyperlinks.
So it was one thing of a shock when the reference peptide remained utterly intact in a 98% sulfuric acid resolution. Utilizing 2D NMR, Hong decided the chain’s 3D form. “It’s an Ω-loop in concentrated sulfuric acid, and it’s an amyloid fiber in water,” she says. And it’s steady. For 2 weeks, Hong’s workforce continued to take NMR measurements. The peptide’s spectrum by no means modified, indicating that the polymer’s form was steady. Different peptide sequences adopted the identical pattern.
Scientists on the Massachusetts Institute of Expertise used nuclear magnetic resonance spectroscopy to develop a structural mannequin of the Ω-loop 3D conformation adopted by a brief peptide chain solvated by 98% sulfuric acid. Credit score:
Courtesy of the researchers/Massachusetts Institute of Expertise
However how may these peptides survive such a harshly acid atmosphere?
“When you have no water, or very restricted water, there’s no hydrolysis. So there’s no acid-catalyzed hydrolysis in any respect,” Seager says. The answer additionally dictates the peptide’s twisted, horseshoe-like form. She likens the sulfuric acid to sticky tape holding the peptide residues in place by electrostatic interactions.
When the paper got here throughout Ad Bax’s desk to evaluation earlier than publication, he was impressed by the findings. Bax constructed his profession on the Nationwide Institutes of Well being utilizing NMR to review protein constructions and would have anticipated hydrolysis to quickly destroy peptides in such acidic options.
“The truth that they reported proof for a reasonably well-ordered construction for every of these peptides is sort of exceptional,” he says. Although Bax can’t say what it means for the seek for alien life, he thinks it’s extraordinary that any protein-like construction would be capable of exist in an atmosphere removed from something seen on Earth.
These outcomes intrigue Stuart Bartlett, an astrobiologist who has researched prebiotic peptide constructions. “This opens the door to exploring a sulfuric-acid-solvent-based biochemistry,” he says. Bartlett is to see what occurs to the construction of longer peptides or when the scientists “simply randomly scramble the sequence,” for instance, to higher perceive if the solvent or the amino acid sequence has extra affect on the ultimate construction.
It’s attainable “that there’s lots of life on the market, but it surely’s simply onerous to acknowledge as a result of it’s totally different from life on Earth,” Bartlett says. This type of analysis may also help us perceive the breadth of life’s potentialities, he provides.
With further reporting by Ana Georgescu.
