Azotosome

An azotosome (classical compound of "azote", French for nitrogen, and "soma", Greek for body[1][2]) is a theoretical membrane that could possibly serve as the basis for a cell membrane of a hypothetical methane–ethane-based living cell, analogous to the phospholipid bilayers found in all water-based life on Earth.[3] Unlike a phospholipid-based cell membrane, an azotosome is composed of chemicals found in the methane–ethane liquid seas and in the atmosphere of Saturn's moon Titan, and it is capable of functioning in these conditions as a membrane.[4]

Conceptualization

The azotosome was proposed in February 2015 by researchers at Cornell University based on computer modeling of theoretical membrane structures. The researchers claimed to be inspired in part by science fiction writer Isaac Asimov's 1962 essay about the concept of non-water based life, entitled "Not as we know it".[1]

Composition

Acrylonitrile, the primary (and only) component of one theorized azotosome.

In principle, the term azotosome refers to any membrane composed of nitrogen, carbon, and hydrogen. The most stable azotosome yet modeled is composed of acrylonitrile, a small molecule composed of three carbons, three hydrogens, and one nitrogen atom. Compared to phospholipids, which make up cell membranes found in life on Earth, acrylonitrile is very small and simple. In the proposed azotosome, acrylonitrile molecules are not arranged in two layers with a hydrophobic and hydrophilic side; rather, some of them are arranged with their nitrogen facing inward and others with their nitrogen facing outward. Despite these differences from phospholipid membranes, the acrylonitrile azotosome is stable, a strong barrier to decomposition, and has a flexibility similar to that of phospholipid membranes.[3][5] Acrylonitrile can self-assemble into azotosomes.[6] Life based on azotosome cells can survive and reproduce in the surface environment of Titan.[6]

The compound acrylonitrile occurs naturally in Titan's atmosphere,[7] so it is readily available for potential life on Titan.

See also

Look up azotosome in Wiktionary, the free dictionary.

References

  1. 1 2 Life 'not as we know it' possible on Saturn's moon Titan
  2. ↑ Extra-terrestrial life based on methane possible on Titan show cell models
  3. 1 2 Stevenson, James; Lunine, Jonathan; Clancy, Paulette (27 Feb 2015). "Membrane alternatives in worlds without oxygen: Creation of an azotosome". Science Advances 1 (1). doi:10.1126/sciadv.1400067.
  4. ↑ Stevenson, James; Lunine, Jonathan; Clancy, Paulette (2015-02-01). "Membrane alternatives in worlds without oxygen: Creation of an azotosome". Science Advances 1 (1): e1400067. doi:10.1126/sciadv.1400067. ISSN 2375-2548.
  5. ↑ Oxygen-free, methane-based life forms could exist on Titan, say scientists
  6. 1 2 How alien life might look on Saturn's moon Titan
  7. ↑ Toumi, A.; Couturier-Tamburelli, I.; Chiavassa, T.; Piétri, N. (2014). "Photolysis of astrophysically relevant acrylonitrile: A matrix experimental study" (PDF). The Journal of Physical Chemistry A 118 (13): 2453–2462. doi:10.1021/jp412481s.
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