Macromolecular condensation is unlikely to buffer intracellular osmolality

The flux of water across biological membrane is determined by gradients in transmembrane osmolality and the water permeability of membranes. Watson et al. (2023) have proposed that the reversible formation and disassembly of molecular condensates could act as the primary buffer of cytoplasmic osmolality in the face of changes in extracellular osmolality. In this communication, we show using well-established membrane biophysics, that the water permeability of plasma membranes is likely to overwhelm any cytoplasmic water buffers.