PACE REPORT

In our efforts to understand the dynamic properties of self assembled matter applied towards creating a protocell, we discovered a very simple chemical system that exhibits movement. The movement presents itself as autonomous or directional depending on the experimental conditions. In this way our simple artificial system displays a critical feature of living systems, namely chemotaxis.

In our system, an oil droplet that contains the chemistry for a one-step hydrolysis reaction is placed in an aqueous environment that contains surfactant. Symmetry of the oil droplet is broken by thermal fluctuations and the droplet begins to move autonomously. The droplet moves because of a self-generated local pH gradient that is produced by the hydrolysis reaction at the oil water interface. This local gradient can be overridden by an imposed external pH gradient and the droplet then exhibits chemotaxis (2). In this simple protocell model a positive feedback loop between the droplet and the environment results in sustained movement. This is the first step to understand how to develop a protocell that can sense and respond to the environment. This principle can now be used to program protocells that respond dynamically to various environmental tasks.