Quantitative Reaction-Diffusion Dynamics in Liquid Condensates*

Liquid droplets have been hypothesized as reaction compartments in cell biology, which can, for example, locally increase or decrease biochemical reaction rates. Providing direct evidence of spatially varying reaction rates provides a formidable challenge in biophysics. We recently introduced a precise way of measuring intra-droplet diffusion rates based on a spatially resolved phase separation model. By extending this framework to chemical reactions, we enable data analysis of phase-separating reaction-diffusion systems. We showcase the applicability of our theoretical method by measuring reaction rates in a system with an enzymatic reaction. 

To eventually enable measuring reaction-diffusion rates in vivo, where droplets are small and approaches based on fully bleaching a condensate are set to fail, we show different fluorescence recovery after photo-bleaching (FRAP) geometries can be used to quantify molecular dynamics in small condensates reliably.