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Theoretical models for the emergence of biomolecular homochirality.

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Call No.	QP517.C57 W55 2010
Author	Walker, Sara Imari.
Title	Theoretical models for the emergence of biomolecular homochirality.
Date	2010
Abstract	Little is known about the emergence of life from nonliving precursors. A key missing- piece is the origin of homochirality: nearly all life is characterized by exclusively dextrorotary sugars and levorotary amino acids. The research presented in this thesis addresses the challenge of uncovering mechanisms for chiral symmetry breaking in a prebiotic environment and implications for the origin of life on Earth. Expanding on a well-known model for chiral selection through polymerization, and modeling the spatiotemporal dynamics starting from near-racemic initial conditions, it is demonstrated that the net chirality of molecular building blocks grows with the longest polymer in the reaction network (of length N ) with critical behavior for the onset of chiral asymmetry determined by the value of N. This surprising result indicates that significant chiral asymmetry occurs only for systems which permit growth of long polymers. Expanding on this work, the effects of environmental disturbances on the evolution of chirality in prebiotic reaction-diffusion networks are studied via the implementation of a stochastic spatiotemporal Langevin equation. The results show that environmental interactions can have significant impact on the evolution of prebiotic chirality: the history of prebiotic chirality is therefore interwoven with the Earths early environmental history in a mechanism we call punctuated chirality. This result establishes that the onset of homochirality is not an isolated phenomenon: chiral selection must occur in tandem with the transition from chemistry to biology, otherwise the prebiotic soup is unstable to environmental events. Addressing the challenge of understanding the role of chirality in the transition from non-life to life, the diffusive slowdown of reaction networks induced, for example, through tidal cycles or evaporating pools, is modeled. The results of this study demonstrate that such diffusive slowdown leads to the stabilization of homochiral bounded structures as expected in the first self-assembled protocells.
Description	xiii, 131 leaves : ill. (some col.) ; 28 cm
Format	application/pdf
Advisor	Gleiser, Marcelo, Blencowe, Miles P., Caldwell, Robert R., Sasselov, Dimitar
Subject	Chirality. Biomolecules -- Mathematical models. Molecular evolution -- Mathematical models.
College	Dartmouth College. Dept. of Physics and Astronomy.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Copyright	All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means without permission in writing from the author.
DOI	http://dx.doi.org/10.1349/ddlp.374

Title	Page 1
Format	application/pdf
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Full Text	THEORETICAL MODELS FOR THE EMERGENCE OF BIOMOLECULAR HOMOCHIRALITY A Thesis Submitted to the Faculty in partial ful llment of the requirements for the degree of Doctor of Philosophy in Physics and Astronomy by Sara Imari Walker DARTMOUTH COLLEGE Hanover, New Hampshire 2 June 2010 Examining Committee: (chair) Marcelo Gleiser Robert Caldwell Miles Blencowe Dimitar Sasselov Brian W. Pogue, Ph.D Dean of Graduate Studies

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