A reception with light refreshments will be held in the B10 lobby before each seminar from 1-1:30 p.m.

Metabolic activity to animate coacervate materials

Allie Obermeyer is an Associate Professor of Chemical Engineering at Columbia University. The Obermeyer Group harnesses the biological and polymeric properties of proteins to create new materials. These studies blend approaches from chemical and synthetic biology, protein engineering, and polymer physics. Allie obtained her undergraduate degree in Chemistry from Rice University and performed undergraduate research in the laboratory of Seiichi P.T. Matsuda. She then joined the Department of Chemistry at UC Berkeley and earned a PhD degree under the guidance of Matthew Francis as a part of the Chemical Biology Graduate Program. She subsequently conducted postdoctoral training in the Chemical Engineering department at MIT as an Arnold Beckman postdoctoral fellow in the laboratory of Bradley Olsen. In 2017, she started her independent career at Columbia University. She has been the recipient of an NSF CAREER and NIH MIRA award as well as a Camille Dreyfus Teacher Scholar Award and a Teaching Award from the Columbia Engineering Alumni Association.

Protein de-mixing is essential to the organization of cellular components. These phase separated membraneless organelles, termed biomolecular condensates, create distinct environments that are essential to cellular processes ranging from signaling to gene expression and stress response. Equilibrium theories reasonably describe the formation of and biomolecule partitioning in these biomolecular condensates, but cellular activities regularly create unstable nonequilibrium compositions. Here I share our efforts to understand how model biomolecular condensates respond when forced out of equilibrium. We create model condensates via the complex coacervation of an enzyme and a polyion. The phase behavior of the resulting liquid-like drops is coupled to their catalytic activity via the local pH. Reaction with chemical “fuel” lowers the pH, creating unstable nonequilibrium conditions, ultimately triggering the formation of internal vacuoles and size dependent droplet dissolution. These responses depend on the rate of reaction-induced pH changes relative to relaxation mechanisms inside the drops. Slow changes are controlled by equilibrium thermodynamics; faster pH changes couple to macromolecule transport on the drop scale. Finally, we demonstrate that these findings translate to more biologically relevant condensates.