Molecular Active Matter, Kinetic Asymmetry, and Non-Reciprocal Interactions

Viewing molecular active matter by analogy with micro- and mesoscopic scale active matter has led to confusion in the field regarding the importance of phoretic or hydrodynamic forces. Here we discuss how kinetic asymmetry and diffusion asymmetry combine with dissipation to provide the necessary time and space symmetry breaking to give rise to directional motion for nanoscale enzymes. Thus, this mechanism enables the generation of higher-order tensorial outputs from scalar energy input. Our model is sufficient to explain both positive and negative chemotaxis of molecular catalysts, as well as the emergence of non-reciprocal interaction between enzymes that share substrates and products. We end by speculating how non-reciprocal interaction at the molecular scale can lead to the generation of memory and order, ingredients that are key to the transition from matter to life.