Physics Colloquium: “How Self-Assembly and Phase Separation Work Together To Build Biological Structures”

The Syracuse University Department of Physics is pleased to welcome LaNell Williams, Associate Research Scholar/CPBF Fellow at Princeton University, for her talk titled, “How self-assembly and phase separation work together to build biological structures.”

Abstract: How does nature build complex structures from repetitive strands of nucleic acid, lipids, and proteins? Furthermore, how does nature decide upon what physical principles to use to build these structures? We hope to explore these questions at the mesoscopic scale and make parallels to macromolecular assembly in soft-condensed matter by studying a membrane-less organelle called the pyrenoid found in a photosynthetic algae named Chlamydomonas reinhardtii (Chlamy). The pyrenoid is made up of three major components; a phase-separated matrix of carbon-fixing enzymes called rubisco, a tubule membrane network that traverses the matrix, and starch that binds the outside of this matrix. How a single pyrenoid forms from all of these components is not well understood. Like other membrane-less organelles such as the nucleolus, the pyrenoid relies on phase separation to build and maintain its structure. During cell division, these components must dissolve and reassemble to deliver essential components to their daughter cells. However, our current work has shown in the absence of the tubule network, the pyrenoid is still unable to assemble into its original structure. This leads us to hypothesize that self-assembly – specifically heterogeneous nucleation and growth on the surface of the tubule membrane- also contributes to the formation of a single pyrenoid. By taking lessons from colloidal self-assembly and applying light microscopy and spectroscopy methods, we hope to understand how phase separation and self-assembly work together to build the pyrenoid found in Chlamydomonas reinhardtii in addition to other complex structures in biology.