Tension Effects on Phase Transitions in Biomimetic Bilayer Membranes

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The research objective of this award is to determine the phase diagram of biomimetic membranes under tension. Membranes in eukaryotic cells are mixtures of hundreds of lipid species. The lipid diversity enables membranes to phase separate and form domains, called rafts, which play a critical role in cell functions such as signaling and trafficking. The phase transitions underlying raft formation have been extensively studied as a function of temperature and composition. However, the third dimension of the phase diagram, i.e., the tension, is still unexplored because membrane tension is difficult to control and quantify. To overcome this challenge, the PI will develop two novel approaches, capillary micromechanics and electrodeformation, in which the tension is regulated by the area dilation accompanying deformation of a vesicle (a closed membrane). These experimental tools will be applied to study the tension?induced domain formation and evolution.If successful, the new tension-control techniques would allow to determine the complete phase-diagram of ternary biomimetic lipid bilayers. The knowledge gained from this work could lead to potentially transformative insights into the biomechanical signal transduction mechanisms that couple changes in membrane tension to changes in cell shape and motility. This will benefit the development of bioengineering applications that exploit the cell signaling and trafficking machinery, e.g., targeted drug delivery. The educational component of this award will involve the introduction of membrane biophysics topics into the traditional engineering curriculum. In particular, the PI will incorporate the results from this research in the graduate course Complex Fluids and Interfaces. The PI will also leverage successful outreach programs at Brown University to communicate the relevance and significance of the work to the general public and attract students from underrepresented groups in science and engineering.