Can polarity-inverted membranes self-assemble on Titan?

• Published in: Science advances Vol. 6; no. 4; p. eaax0272
• Main Authors: Sandström, H, Rahm, M
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 01.01.2020
• Subjects: Astrobiology; Chemistry; Cytology; Molecular dynamics; Planetary Science; Quantum theory; SciAdv r-articles; Temperature
• ISSN: 2375-2548; 2375-2548
• DOI: 10.1126/sciadv.aax0272

The environmental and chemical limits of life are two of the most central questions in astrobiology. Our understanding of life's boundaries has implications on the efficacy of biosignature identification in exoplanet atmospheres and in the solar system. The lipid bilayer membrane is one of the central prerequisites for life as we know it. Previous studies based on molecular dynamics simulations have suggested that polarity-inverted membranes, azotosomes, made up of small nitrogen-containing molecules, are kinetically persistent and may function on cryogenic liquid hydrocarbon worlds, such as Saturn's moon Titan. We here take the next step and evaluate the thermodynamic viability of azotosome formation. Quantum mechanical calculations predict that azotosomes are not viable candidates for self-assembly akin to lipid bilayers in liquid water. We argue that cell membranes may be unnecessary for hypothetical astrobiology under stringent anhydrous and low-temperature conditions akin to those of Titan.