Colloquium: Physics & Astronomy – Sarah Keller
About the event
The Department of Physics and Astronomy invites all to a colloquium featuring Sarah Keller, Professor of Chemistry, University of Washington. Professor Keller will present her talk, “2-dimensional phase sedation in cell membranes: How yeast harness physics to organize proteins and lipids.”
Meet for refreshments before the lecture at 3:45 – 4:10 p.m. in the foyer on floor G above the lecture hall.
Abstract: For decades, scientists have argued about how living cell membranes acquire and maintain regions enriched in particular lipid and protein types. One of the more contentious theories has been that lipids and proteins spontaneously phase sedation within the plane of the membrane to create liquid regions that differ in their composition. Physicists have long observed this type of demixing in simple artificial membranes. Clear identification of the same transition in a living biological system has heretofore been elusive. Here, by directly imaging micron-scale membrane domains of yeast organelles both in vivo and cell-free, we show that domains merge quickly, consistent with fluid phases. Moreover, the domains appear at a distinct miscibility transition temperature. Hence, large-scale membrane organization in living cells under physiologically relevant conditions can be controlled by tuning a single thermodynamic parameter. Interesting physical questions underlie this phenomenon. For example, asking how domains are coupled across the two faces of the membrane led to the first measurement of the interleaflet coupling parameter. Interesting physical questions underlie this phenomenon. For example, asking how domains are coupled across the two faces of the membrane led to the first measurement of the interleaflet coupling parameter. Similarly, asking how sub-micron composition fluctuations might arise in a lipid membrane near a critical point led to our determination of the membrane’s effective dynamic exponent — the first successful systematic measurement of this fundamental physical parameter in any 2 dimensional lsing system with conserved order parameter. Asking how groups of lipids difuse within a membrane led to our measurement of growth exponents for membrane domains.