"Giant Vesicles: Mixing Water, Transducing Energy, Shaping membranes"
A fundamental consequence of cellular organization of living systems is that the aqueous milieu, bathing the cell, is also compartmentalized. Although water equilibrates readily across the elastic cellular boundary, passive permeation of solutes is strongly hindered. As a result, gradients of concentrations of ions, salt, and soluble biomolecules are readily established across the cellular boundary, producing osmotic activity of water. Drawing from recent experiments in our labs employing simple models for the cellular chassis (i.e., giant vesicles), this talk considers how the osmotic activity of water is transduced across cell-like compartments. It highlights how the non-equilibrium activity of water couples with the compartmental boundary, spatially reorganizing membrane components and mechanically remodeling the vesicle shape. Comparing these processes as elemental events in the homeostatic working of a living cell, these findings support the idea that water is not a mere solvent for life – a blank canvas on which biomolecules become animated – but an active medium that guides organization and dynamics of biomolecules in complex, subtle, and essential ways.