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.
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Host: Williams
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