Astrochemistry

The Chiral Puzzle Of Life

By Keith Cowing
q-bio.OT
July 11, 2022
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The Chiral Puzzle Of Life
The figure shows the 3D structure of the RNA molecule and its mirror image. The direction of the helical conformation of the nucleic acids derives from the underlying chemical chirality of the sugar backbone. The nucleic acids contain only right-handed sugars (D-ribose in RNA, D-deoxyribose in DNA), shown in the right-hand side of the figure. They naturally assume a right-handed helical conformation. In the mirror world (left-hand side in the figure), the nucleic acids would contain only left-handed sugars (L-ribose or L-deoxyribose) and would assume a predominantly left-handed helical conformation.

Biological molecules chose one of two structurally, chiral systems which are related by reflection in a mirror. It is proposed that this choice was made, causally, by magnetically polarized and physically chiral cosmic-rays, which are known to have a large role in mutagenesis.

It is shown that the cosmic rays can impose a small, but persistent, chiral bias in the rate at which they induce structural changes in simple, chiral monomers that are the building blocks of biopolymers.

A much larger effect should be present with helical biopolymers, in particular, those that may have been the progenitors of RNA and DNA. It is shown that the interaction can be both electrostatic, just involving the molecular electric field, and electromagnetic, also involving a magnetic field.

It is argued that this bias can lead to the emergence of a single, chiral life form over an evolutionary timescale. If this mechanism dominates, then the handedness of living systems should be universal. Experiments are proposed to assess the efficacy of this process.

Noemie Globus, Roger D. Blandford

Comments: 18 pages, 6 figures, accepted for publication in The Astrophysical Journal Letters. arXiv admin note: text overlap with arXiv:1911.02525
Subjects: Other Quantitative Biology (q-bio.OT); High Energy Astrophysical Phenomena (astro-ph.HE)
Cite as: arXiv:2002.12138 [q-bio.OT] (or arXiv:2002.12138v2 [q-bio.OT] for this version)
https://doi.org/10.48550/arXiv.2002.12138
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Related DOI:
https://doi.org/10.3847/2041-8213/ab8dc6
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Submission history
From: Noemie Globus
[v1] Sun, 23 Feb 2020 20:02:56 UTC (3,986 KB)
[v2] Fri, 1 May 2020 18:13:41 UTC (3,994 KB)
https://arxiv.org/abs/2002.12138
Astrobiology, Astrochemistry,

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