Condensed Matter Physics Seminar

2 p.m., Thursday, January 27, 2005
Room 1201, Physics Building

 Of polka dots and dumbbells: phase behavior and bending of biomembranes

Tobias Baumgart

(Cornell University)

Abstract:  One of the most important, yet unresolved questions in current cell membrane biology is how the plasma membrane and membranes bounding cellular organelles maintain their composition despite the vigorous intracellular transport between these entities. A lateral segregation of membrane components in terms of coexisting fluid domains with distinct composition has been suggested as part of a mechanism to maintain organelle integrities. Furthermore, a fundamental coupling between membrane composition and membrane curvature is assumed to be important in modulating biomembrane shape and composition specific membrane transport. These hypotheses warrant evaluation by biophysical experiments.  While biomembranes show an enormous complexity, model membranes with well defined composition can be formed that show two coexisting fluid phases. We characterized fluid phase coexistence in giant unilamellar vesicles with phase sensitive fluorescent lipid analogs and found fluid phase coexistence to couple to membrane curvature and tension. Membrane curvature in deformed vesicles with axial symmetry was analyzed in terms of a theoretical mechanical model, yielding estimates of the mechanical parameters.  Furthermore, our studies of low curvature membrane blebs from rat basophilic leukemia cells allowed confirming fluid phase coexistence in highly complex biological membranes.
Host:  Williams
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