Abstract
How homochirality concerning biopolymers (DNA/RNA/proteins) could have originally occurred (i.e., arisen from a non-life chemical world, which tended to be chirality-symmetric) is a long-standing scientific puzzle. For many years, people have focused on exploring plausible physic-chemical mechanisms that may have led to prebiotic environments biased to one chiral type of monomers (e.g., D-nucleotides against L-nucleotides; L-amino-acids against D-amino-acids)-which should have then assembled into corresponding polymers with homochirality, but as yet have achieved no convincing advance. Here we show, by computer simulation-with a model based on the RNA world scenario, that the biased-chirality may have been established at polymer level instead, just deriving from a racemic mixture of monomers (i.e., equally with the two chiral types). In other words, the results suggest that the homochirality may have originated along with the advent of biopolymers during the origin of life, rather than somehow at the level of monomers before the origin of life.
Highlights
People have long been curious about the fact that central molecules in the living world, i.e., nucleic acids and proteins, are asymmetric in chirality, but as the relevant background, the chemical world is symmetric in chirality
That life should have originated from a prebiotic non-life background, how could this dissymmetry have occurred? Previous studies in this area focused their efforts on how the chiralitysymmetry may have been broken at the monomer level, but have achieved little advance over decades of years
The process is an issue of chemistry and an issue involving evolution– previously difficult to reveal by pure lab work in this area
Summary
In a prebiotic chemical world, the small molecules from which these macromolecules could be synthesized tend to have existed as racemic mixtures (that is, with equal quantities of the two chiral types) This brings up a significant sub-problem, i.e., the origin of homochirality, for the problem of the origin of life [1,2,3]. The origin of life is a field full of controversies, which is not surprising when considering we have not even reached a consensus on the definition of life [4,5,6]. In this field, relevant issues are often not clearly defined. Many years of efforts along this line have not led to any convincing conclusion–there are quite a lot of hypotheses or speculations; many of those experimental results are yet far from being relevant to the biomonomers (see [3,7,8] for recent reviews)
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