Homochirality

Homochirality through Photon-Induced Melting of RNA/DNA: the
Thermodynamic Dissipation Theory of the Origin of Life
K. Michaelian
The homochirality of the molecules of life has
been a vexing problem with no generally accepted solution to
date. Since a racemic mixture of chiral nucleotides frustrates
the extension and replication of RNA and DNA, understanding
the origin of homochirality has important implications to
the investigation of the origin of life. Theories on the origin
of life have generally elected to presume an abiotic mechanism
giving rise to a large prebiotic enantiomer enrichment.

Although a number of such mechanism have been suggested,
none has enjoyed sufficient plausibility or relevance to be
generally accepted. Here we suggest a novel solution to the
homochirality problem based on a recently proposed thermodynamic
dissipation theory for the origin of life. The ultraviolet
absorption and dissipation characteristics of RNA/DNA
point to their origin as photoautorophs, their replication assisted
by UV light and temperature, and acting as catalysts
for the global water cycle. Homochirality is suggested to
have been incorporated gradually into the emerging life as a
result of asymmetric right- over left-handed photon-induced
denaturation of RNA/DNA occurring when Archean sea surface
temperatures became close to the denaturing temperatures
of RNA/DNA.

This differential denaturing success would have been promoted by the somewhat right-handed circularly polarized submarine light of the late afternoon
when surface water temperatures are highest, and a negative
circular dichroism band extending from 220 nm up to 260
nm for small segments of RNA/DNA. A numerical model
is presented demonstrating the efficacy of such a mechanism
in procuring 100% homochirality of RNA or DNA
from an original racemic solution in less than 500 Archean
years assuming a photon absorption threshold for replication
representing the hydrogen bonding energy between complementary
strands. Because cholesteric D-nucleic acids have
greater affinity for L-amino acids due to a positive structural
complementarity, and because D-RNA/DNA+L-amino acid
complexes also have a negative circular dichroism band between
200 – 300 nm, the homochirality of amino acids can
also be explained by the theory.

For complete details, see K. Michaelian, Homochirality through Photon-induced melting of RNA/DNA: Thermodynamic Dissipation Theory of the Origin of Life, WebmedCentral BIOCHEMISTRY 2010;1(10):WMC00924 http://www.webmedcentral.com/article_view/924

and;

Michaelian, K., Homochirality through Photon-Induced Denaturing of RNA/DNA at the Origin of Life, Life 2018, 8, 21. https://www.mdpi.com/2075-1729/8/2/21

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