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Dissipative systems showing signs of life
Complex networks of chemical reactions together define how life works. We are familiar with the metabolic networks studied in biochemistry, and in recent decades many regularly recurring network motifs have been uncovered that are responsible for much of the functional behaviour in signalling or genetic networks. However, molecular "circuits" are very delicate, and sensitive to changes in concentration, temperature, and so on. I believe we need a new direction in chemistry to provide a truly molecular level insight into how molecules create life. Recently, we presented a versatile strategy for "synthesizing" programmable enzymatic reaction networks in microfluidic flow reactors that exhibit sustained oscillations. I will show how small molecules with subtly different functional groups offer tuning of the properties of the network and how we can explore the dynamics (i.e. robustness and resilience) of these reaction networks in response to global perturbations. Furthermore, I will discuss recent work on the dissipative self-assembly of FtsZ protein (a bacterial homologue of tubulin) within coacervate droplets. More specifically, we show how barrier-free compartments govern the local availability of the energy-rich building block GTP, yielding highly dynamic fibrils. The increased flux of FtsZ monomers at the tips of the fibrils results in localized FtsZ assembly, elongation of the coacervate compartments, followed by division of the fibrils into two. We rationalize the directional growth and division of the fibrils using dissipative reaction-diffusion kinetics and capillary action of the filaments as main inputs. I will discuss these results, in which open compartments are used to modulate the rates of dissipative self-assembly by restricting the absorption of energy from the environment, in the context of a general route to dissipatively adapting nanosystems exhibiting life-like behaviour.