Artificial Life VI


Computational Models for the Formation of Protocell Structures

Linglan Edwards
Computer Science and Electrical Engineering Dept., U. of Maryland, Baltimore County
http://www.cs.umbc.edu/~linglan

Yun Peng
Computer Science and Electrical Engineering Dept., U. of Maryland, Baltimore County
http://www.cs.umbc.edu/~ypeng


Abstract

It is generally believed that during prehistoric evolution phospholipid molecules first self-assembled into protocell structures such as micelles, monolayer and bilayer structures, some of which eventually evolved into cell membranes. There have been various attempts to simulate the self-assembly process by computer. However, due to the computationally complex nature of the problem, previous simulations were often conducted with unrealistic simplifications of the molecules' morphology, intermolecular interaction, and the environment in which the molecules interact. In this paper, we present a new computational model to simulate the self-assembly of lipid aggregates. In this model, each lipid is simulated by a more realistic amphiphilic particle consisting of a hydrophilic head and a long hydrophobic tail. The intermolecular interactions are approximated by a set of simple forces reflecting physical and chemical properties (e.g., hydrophobicity and electrostatic) of lipids believed to be crucial for the formation of various aggregates. Special efforts have been made to reduce the model's computational complexity. With a set of carefully selected parameters, this model is able to successfully simulate the formation of micelles in an aqueous environment and reverse micelle structures in an oil solvent from an initially randomly distributed set of lipid-like particles. We believe that, compared with previous works, this model provides a more accurate computer simulation of the self-assembly of lipids in a more realistic prebiologic setting. This model can be used to study, at the microscopic level, the self-assembly of different protocell structures in the evolutionary process and the impact of environmental conditions on the formation of these structures. It may be further generalized to simulate the formation of other, more complex structures of amphiphilic molecules such as monolayer and bilayer aggregates.


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