Abstract

Cell membranes are a paradigm of soft materials that have evolved to regulate essential biological processes with remarkable efficiency and precision—capabilities that scientists and engineers strive to emulate. Their functionality arises from the molecular architecture of lipids and sterols, which dynamically respond to environmental and dietary changes and offer versatile design elements for synthetic materials. Whether biological or artificial, membranes must balance competing material demands: they must be sufficiently rigid to serve as protective barriers, yet fluid enough to support the molecular mobility essential for function. Understanding how lipid–sterol interactions govern emergent elasticity is therefore central to both biological function and bioinspired technologies, including artificial cells, liposomal drug delivery, and biosensing platforms. Despite decades of research, measurements of membrane elasticity and structure have often yielded seemingly contradictory results, leading to interpretations that emphasize chemically specific effects. In this talk, I will show how neutron spin-echo spectroscopy, integrated with NMR relaxometry and molecular dynamics simulations, helps resolve this challenge. Our findings reveal that, at mesoscopic length and timescales bridging molecular and macroscopic behavior, membrane bending moduli follow a unified scaling relation with the lipid packing density across diverse molecular compositions. More recent studies of engineered lipid–sterol hybrids further demonstrate how molecular architecture can be leveraged to tune membrane dynamics and mechanics across scales. Together, these insights establish a foundation for predictive structure–property relationships in lipid-based materials, opening new opportunities to translate fundamental principles of biological membranes into bioinspired technologies and biomedical applications.

Bio

Rana Ashkar is the Patricia Caldwell Faculty Fellow and Associate Professor in the Department of Physics at Virginia Tech, where she serves as Director of the Center for Soft Matter and Biological Physics. Before joining Virginia Tech, she held a Clifford G. Shull Fellowship at Oak Ridge National Laboratory, following a joint postdoctoral appointment at NIST and the University of Maryland. She earned her Ph.D. in condensed matter physics from Indiana University, where her doctoral research received the Esther L. Kinsley Dissertation Award. Her research integrates experiment, theory, and advanced scattering methods to investigate how nanoscale structure and dynamics give rise to emergent mechanical and adaptive behavior in biological and soft materials. Her work spans biophysics, soft matter physics, and nanostructured materials, with applications in materials science, synthetic biology, and nanotechnology. Her honors include recognition as a 2021 Soft Matter Emerging Investigator and a 2025 Sloan Research Fellow.

website: https://ashkar.science/

Hosted by Angela Pitenis.