Abstract：
:We have investigated, both experimentally and theoretically, the efflux of carboxyfluorescein (a self-quenching fluorescent dye) from vesicles of different sizes and lipid species (POPC, DOPC) after having added the bee venom peptide melittin. This comprises quantitative analyses regarding the extent of lipid-associated peptide, the mode as well as the temporal progress of dye release and the possible leakage mechanism. Our results indicate a graded efflux characterized by a single-pore retention factor reflecting the formation of pores whose lifetimes are rather small (millisecond range). The observed fluorescence signal arising from the dequenching of effluent dye has been converted to the number of pore openings over the course of time. All the resulting curves exhibit a pronounced slowing down of the pore formation rate revealing two distinct relaxation steps at about 20 and 200 s, respectively, being largely independent of vesicle type and peptide to lipid ratio. The pore formation rate itself increases in proportion to the amount of membrane bound peptide. We give a quantitative account of our experimental findings based on a novel reaction scheme applicable to any of our various liposome systems. It implies that the pore formation rate is controlled by a passage through two intermediate monomeric peptide states. These states are thought to become well populated in the initial stage of lipid bilayer perturbation, but would practically die out after some time owing to a restabilization of the membrane system.
journal_name
Biochemistryjournal_title
Biochemistryauthors
Rex S,Schwarz Gdoi
10.1021/bi971009psubject
Has Abstractpub_date
1998-02-24 00:00:00pages
2336-45issue
8eissn
0006-2960issn
1520-4995pii
bi971009pjournal_volume
37pub_type
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