The goal of this proposal is to establish experimental techniques and develop foundational experimental data describing how general integral membrane proteins affect the mechanical properties of biomembranes. These tools and results will have a transformative effect on our understanding of biomembranes as continuum materials. Most contemporary research in bilayer-protein interactions focuses either on how specific proteins (SNARE complexes, viral fusion proteins) exert force on lipid bilayers or how forces in the lipid bilayer can modulate integral membrane protein function. The PI is looking at the membrane as a continuum material in which the mechanical properties are determined by both the lipids and the integral membrane proteins. Given the high concentration of proteins in the membrane, such a view is necessary in order to fully understand how biomembranes move and deform. Membrane deformation is a central phenomenon in biology, underlying such processes as cell division, viral infection, and neurotransmitter release. This proposal includes a comprehensive educational plan for outreach to high school students. The primary objective of this outreach program is to facilitate intensive research experiences for students drawn from the diverse population of the Los Angeles Unified School District. This will be accomplished by cooperating with an established outreach program at the Engineering for Health Academy at Francisco Bravo Medical Magnet High School to bring grade-12 students into the laboratory for yearlong internships. Interns will be mentored by the graduate student funded by this award and will undertake their own small, independent research projects.
The PI will use standard methods for measuring the mechanical properties of lipid bilayers in giant unilamellar lipid vesicles (GUVs). The key innovative aspect of this research is enabled by a technology that the PI's laboratory recently developed to incorporate integral membrane proteins into GUVs at relatively high concentrations. This will allow the PI to examine the mechanical properties on GUVs with controlled concentrations of membrane proteins. The PI will investigate proteins with a variety of transmembrane motifs to discover how the structure of the transmembrane domains affects how proteins are mechanically coupled to the bilayer. The two properties that will be measured for each protein at a range of concentrations are: 1.) The tendency of a membrane to bend when no external forces are applied. This is described by the spontaneous (or intrinsic) curvature JSB. 2.) The amount of energy required to bend the membrane away from its intrinsic curvature. This is described by the bending modulus kc. These two parameters are central to describing the energetics of membrane deformation during biological processes. The PI will use a combination of micropipette aspiration and vesicle fluctuation analysis to independently determine the value of each parameter for a given set of conditions.
This project is being jointly supported by the Physics of Living Systems program in the Division of Physics and the Molecular Biophysics program in the Division of Molecular and Cellular Biosciences.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
