On the relationship between concentration buffering and noise reduction in phase separating systems

Abstract

Biomolecular condensates have been proposed to buffer intracellular concentrations and reduce noise. Recent results demonstrate that concentrations need not be buffered in multicomponent systems, leading to a non-constant saturation concentration ( csat ) when individual components are varied. Simplified equilibrium considerations suggest that noise reduction might be closely related to concentration buffering and that a fixed saturation concentration is required for noise reduction to be effective. Here we present a theoretical analysis to demonstrate that these suggestions do not apply to mesoscopic fluctuating systems. We show that concentration buffering and noise reduction are distinct concepts, which cannot be used interchangeably. We further demonstrate that concentration buffering - and a constant csat - are neither necessary nor sufficient for noise reduction to be effective. Clarity about these concepts is important for studying the role of condensates in controlling cellular noise and for the interpretation of concentration relationships in cells.