Reaction networks of precise topology and kinetic features underlie all cellular functions and computations. Reproducing these non-linear chemical systems in vitro requires a programmable chemical toolbox: a set of generic reactions that can be rewired, cascaded, looped at will, so as to fulfill a particular dynamical function.

I will discuss such a set, based on small synthetic DNA strands used to constrain enzymatic reactivity along user-defined kinetic paths. Bi- and multi-stable, relaxation oscillators or the first predator-prey chemical ecosystem have been experimentally constructed. These systems use mild chemical conditions and can be used as modular building blocks to build larger molecular organizations. For example, in a spatially extended reactor, we observe traveling fronts and waves of DNA species; in emulsion of micro-droplets we can directly visualize the full bifurcation diagram of a particular design or circuit.

We anticipate that this approach will open new avenues for the bottom-up construction of dissipative chemical behaviors in both time and space and the study of their feature-function relationships.

Figure caption: fluorescently barcoded micro-droplets running DNA molecular programs.