Biochemistry & Organic Chemistry

Origin of Biological Homochirality by Crystallization of an RNA Precursor on a Magnetic Surface

By Keith Cowing
Status Report
physics.bio-ph
June 16, 2023
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Origin of Biological Homochirality by Crystallization of an RNA Precursor on a Magnetic Surface
The mechanism of spin-selective crystallization due to the CISS effect and the experimental setup. a. As molecules approach a surface, they transiently acquire an induced charge polarization. Due to the CISS effect, transient charge polarization of a chiral molecule is accompanied by spin polarization. The spin state associated with the charge poles is determined by the handedness of the chiral molecule. Because the magnetic surface itself is spin polarized it kinetically favors (akin to a seed crystal) the enantiomer whose transient spin state results in a lower energy spin-exchange interaction. The lower energy overlap with the magnetic surface is singlet-like (red, ↑↓) and the higher energy overlap is triplet-like (blue, ↑↑). The energy difference between these two configurations is higher than the room temperature, kBT, therefore the effect robustly manifests itself. b. Schematic of the setup used in the crystallization experiments and a sample microscope image of the RAO crystals on a magnetite surface from a direct crystallization experiment. The image shows the magnetite surface as the black background and the needle-shaped conglomerate crystals of RAO formed on the surface, as well as the twinned crystals with stochastically arranged needles of D and L-RAO, and racemic RAO in the form of a flaky powder suspended in the water column above the surface. — physics.chem-ph

Homochirality is a signature of life on Earth yet its origins remain an unsolved puzzle. Achieving homochirality is essential for a high-yielding prebiotic network capable of producing functional polymers like ribonucleic acid (RNA) and peptides.

However, a prebiotically plausible and robust mechanism to reach homochirality has not been shown to this date. The chiral-induced spin selectivity (CISS) effect has established a strong coupling between electron spin and molecular chirality and this coupling paves the way for breaking the chiral molecular symmetry by spin-selective processes. Magnetic surfaces can act as chiral agents due to the CISS effect and they can be templates for the enantioselective crystallization of chiral molecules.

Here we studied the spin-selective crystallization of racemic ribo aminooxazoline (RAO), an RNA precursor, on magnetite (Fe3O4) surfaces, achieving an unprecedented enantiomeric excess of about 60%. Following the initial enrichment, we then obtained homochiral crystals of RAO after a subsequent crystallization. Our work combines two necessary features for reaching homochirality: chiral symmetry-breaking induced by the magnetic surface and self-amplification by conglomerate crystallization of RAO. Our results demonstrate a prebiotically plausible way of achieving systems level homochirality from completely racemic starting materials.

S. Furkan Ozturk, Ziwei Liu, John D. Sutherland, Dimitar D. Sasselov

Comments: 12 pages, 5 figures
Subjects: Biological Physics (physics.bio-ph); Chemical Physics (physics.chem-ph); Biomolecules (q-bio.BM)
Cite as: arXiv:2303.01394 [physics.bio-ph] (or arXiv:2303.01394v1 [physics.bio-ph] for this version)
https://doi.org/10.48550/arXiv.2303.01394
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Submission history
From: Sukru Furkan Ozturk
[v1] Thu, 9 Feb 2023 20:44:38 UTC (8,624 KB)
https://arxiv.org/abs/2303.01394
Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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