Fig. 1: Agent-based models are able to reproduce mass action kinetics.

Particles with diffusion coefficients of 1 μm²·s⁻¹ (blue), 5 μm²·s⁻¹ (green) and 10 μm²·s⁻¹ (red) were simulated (a) and the observed MSD was compared to the expected MSD (thick grey lines) (b). First order reactions with k values of 10⁻¹ s⁻¹, 10⁻² s⁻¹, 10⁻³ s⁻¹, 10⁻⁴ s⁻¹ and 10⁻⁵ s⁻¹ were simulated for 5 min with a time step of 0.05 s by ABM (thin lines) and compared to equivalent ODE models (thick grey lines) (c). The second order reactions of two soluble molecules (d), a soluble molecule with a membrane-bound molecule (e) and two membrane-bound molecules (f) were simulated with ABM and the ABM:ODE Score between the ABM simulations and equivalent ODE models were plotted for k_f values of 10⁴ M⁻¹·s⁻¹, 10⁵ M⁻¹·s⁻¹, 10⁶ M⁻¹·s⁻¹ and 10⁷ M⁻¹·s⁻¹ and different indicated concentration ratios of A to B ([A]:[B]). Dashed lines indicate the perfect agreement between ABM and ODE of 1. All simulations were for 5 min, the time step Δt for particle diffusion in all simulations was 0.0001 s and for reactions was 0.05 s. The diffusion coefficients used in d–f were 30 μm²·s⁻¹ for soluble molecules and 0.3 μm²·s⁻¹ for membrane-bound molecules.