Eric Dufresne - Kavli Distinguished Lecture

Title: Living Droplets Get to Work

Abstract: 

A simple drop of water is held together by weak attractive interactions.  It can coexist with its low density vapor phase or with a bath of oil with traces of water. These familiar liquid phases have huge contrast in their compositions.  However, liquids can be much more subtle.  For example, a semi-dilute aqueous solution of two macromolecules at room temperature can spontaneously form coexisting liquid phases.  Near a critical composition, the two phases have nearly identical compositions and include more than 90% water. 

It was recently discovered that living cells possess similar distinct liquid phases, characterized by enrichment with different macromolecules.  These liquids are thought to play an essential biological role by compartmentalizing and controlling chemical reactions. 

In this talk, I will introduce one of these liquid phases, whose droplets are called stress granules.  Adapting classical analytical tools from statistical physics, we infer attractive interactions of stress granules with microtubules, an important type of supramolecular filament.  We validate this finding with a simplified in vitro system, and introduce a thermodynamic model that captures the essential physics.  These findings suggest an additional mechanical role for liquid phases within the cell.

With further in vitro experiments, I will demonstrate that these phases are remarkably efficient at localizing chemical reactions.  When driven far from equilibrium, concentration fields around microscopic droplets spontaneously break symmetry and create stunning fluid motion, characterized by persistent cell-like motility and long-range interactions.  This simple coupling of chemical reactions to phase separation is a promising new class of active matter, with close ties to the physiology of living cells.