From Stanford University: “Cosmic rays may have left indelible imprint on early life, Stanford physicist says”

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From Stanford University

May 20, 2020
Taylor Kubota
Stanford News Service
(650) 724-7707
tkubota@stanford.edu

Physicists propose that the influence of cosmic rays on early life may explain nature’s preference for a uniform “handedness” among biology’s critical molecules.

Before there were animals, bacteria or even DNA on Earth, self-replicating molecules were slowly evolving their way from simple matter to life beneath a constant shower of energetic particles from space.

Cosmic rays produced by high-energy astrophysics sources (ASPERA collaboration – AStroParticle ERAnet)

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Magnetically polarized radiation preferentially ionized one type of “handedness” leading to a slightly different mutation rate between the two mirror proto-lifeforms. Over time, right-handed molecules out-evolved their left-handed counterparts. (Image credit: Simons Foundation)

In a new paper, [Astrophysical Journal Letters], a Stanford professor and a former postdoctoral scholar speculate that this interaction between ancient proto-organisms and cosmic rays may be responsible for a crucial structural preference, called chirality, in biological molecules. If their idea is correct, it suggests that all life throughout the universe could share the same chiral preference.

Chirality, also known as handedness, is the existence of mirror-image versions of molecules. Like the left and right hand, two chiral forms of a single molecule reflect each other in shape but don’t line up if stacked. In every major biomolecule – amino acids, DNA, RNA – life only uses one form of molecular handedness. If the mirror version of a molecule is substituted for the regular version within a biological system, the system will often malfunction or stop functioning entirely. In the case of DNA, a single wrong handed sugar would disrupt the stable helical structure of the molecule.

Louis Pasteur first discovered this biological homochirality in 1848. Since then, scientists have debated whether the handedness of life was driven by random chance or some unknown deterministic influence. Pasteur hypothesized that, if life is asymmetric, then it may be due to an asymmetry in the fundamental interactions of physics that exist throughout the cosmos.

“We propose that the biological handedness we witness now on Earth is due to evolution amidst magnetically polarized radiation, where a tiny difference in the mutation rate may have promoted the evolution of DNA-based life, rather than its mirror image,” said Noémie Globus, lead author of the paper and a former Koret Fellow at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC).

See the full article here .


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