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Mechanically Induced Homochirality in Nucleated Enantioselective Polymerization.
Celia Blanco1, Michael Stich2, David Hochberg3
1Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9510, United States.
The Journal of Physical Chemistry. B
|January 11, 2017
Summary
This study models cooperative enantioselective polymerization, demonstrating how spontaneous mirror symmetry breaking and chiral amplification can emerge from statistical fluctuations in closed systems, offering insights into the origin of homochirality.
Area of Science:
- Origin of Life Research
- Chemical Evolution
- Biochemistry
Background:
- Biological homochirality is a fundamental property of life, yet its emergence during early chemical evolution remains poorly understood.
- Existing models often require specific chiral catalysts or autocatalysis, which may not represent early Earth conditions.
Purpose of the Study:
- To develop and numerically solve a kinetic model for nucleated cooperative enantioselective polymerization in closed systems.
- To investigate the spontaneous emergence of homochirality and chiral amplification without external chiral agents or autocatalysis.
Main Methods:
- Numerical solution of a kinetic rate equation model.
- Incorporation of monomer racemization, linear chain growth (nucleation and elongation), and homochiral chain annealing/fusion.
- Inclusion of mechanically induced chain breakage to maintain a non-equilibrium state and drive a breakage-fusion recycling mechanism.
Main Results:
- Demonstrated spontaneous mirror symmetry breaking from small initial enantiomeric excesses, driven by statistical fluctuations.
- Observed significant chiral amplification, indicating the model's capacity for absolute asymmetric synthesis.
- Showcased a functional breakage-fusion recycling mechanism that maintains the system out of equilibrium.
Conclusions:
- The model successfully explains the emergence of homochirality through cooperative polymerization and a breakage-fusion mechanism.
- Absolute asymmetric synthesis is achievable without chiral cross-inhibition or explicit autocatalysis, providing a plausible pathway for prebiotic chiral selection.
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