PHYS 22 |
| Dual-color fluorescence-burst analysis was used to probe the formation and size of two types of membrane pores, those formed by the lytic peptide melittin and the membrane tension-gated mechanosensitive channel of large conductance (MscL). To perform DCFBA, fluorescently-labeled size-marker molecules were encapsulated into liposomes, labeled with a second lipid-attached fluorophore. By correlating the fluorescence bursts, resulting from the liposomes diffusing through the detection volume of a dual-color confocal microscope, the distribution of size-marker molecules over the liposomes was determined. For melittin, we show that leakage occurs via two different mechanisms: (1) In liposomes composed of neutral bilayer-forming lipids, low concentrations induced pore formation with the pore-size depending on the melittin concentration. (2) In liposomes containing anionic and/or nonbilayer-forming lipids, melittin induced fusion of liposomes accompanied by a-specific leakage. For MscL, we demonstrate that proteins smaller than 6.5 kDa can pass through the pore, whereas larger macromolecules cannot. |
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Biological Ion Channels: From Molecular Structure to Cellular Function
8:15 AM-12:00 PM, Sunday, August 19, 2007 BCEC -- 157B, Oral
Division of Physical Chemistry |