Events Calendar

USC Physical Sciences and Oncology Center

Speaker: Michelle Povinelli, PhD, Assistant Professor, Department of Electrical Engineering

Talk Title: Stretching of Lipid Membranes Using Optical Forces

Abstract: Membrane bending and stretching control key aspects of cellular function, and changes in chemical composition alter membrane mechanical properties. GUVs are model lipid bilayer systems that have become popular for investigating membrane mechanical properties. The ability of membranes to bend under low stress is characterized by the bending modulus (κB). We show that the optical stretcher, or dual-beam optical trap (DBOT), provides a method for non-invasive application of time-dependent forces on a GUV, allowing rapid measurement of the bending modulus.The applied stress in a DBOT elongates the GUV, increasing its eccentricity. We increase the optical power in the DBOT as a function of time and extract the resulting surface area strain (percent change in surface area) from analysis of microscope video images. The lateral tension on the membrane at each power level is calculated from the surface stress. The bending modulus can be extracted from the slope of the area strain vs. surface stress plot.We compare the bending modulus values obtained from a lipid bilayer in liquid phase, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and bilayer in gel phase, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). We observe that the bending modulus of gel phase bilayer is larger than the lipid phase bilayer. We then show that we can use our high-throughput setup to measure the bending modulus of populations of GUVs and obtain ensemble statistics. We compare the bending modulus of POPC lipid bilayer with and without cholesterol and show that the addition of cholesterol does not significantly affect the bending modulus.

Biography: USC was selected to establish a $16 million cancer research center as part of a new strategy against the disease by the U.S. National Institutes of Health and its National Cancer Institute. The new center is one of 12 in the nation to receive the designation. During the five-year initiative, the Physical Sciences-Oncology Centers will take new, nontraditional approaches to cancer research by studying the physical laws and principles of cancer; evolution and the evolutionary theory of cancer; information coding, decoding, transfer and translation in cancer; and ways to de-convolute cancer's complexity. As part of the outreach component of this grant, the Center for Applied Molecular Medicine is hosting a monthly seminar series.

Host: USC Physical Sciences in Oncology Center

Location: Clinical Science Center (CSC) - Harkness Auditorium

Audiences: Everyone Is Invited

Contact: Kristina Gerber