Fusion competence of phosphatidylserine-containing liposomes quantitatively measured by a fluorescence resonance energy transfer assay
| Autor: | David W. Deamer, Paul S. Uster |
|---|---|
| Rok vydání: | 1981 |
| Předmět: |
chemistry.chemical_classification
Phosphatidylethanolamine Liposome Chromatography Chemistry Phosphatidylethanolamines Vesicle Biophysics Ionophore chemistry.chemical_element Phosphatidylserines Phosphatidylserine Calcium Biochemistry Divalent chemistry.chemical_compound Cholesterol Spectrometry Fluorescence Förster resonance energy transfer Energy Transfer Liposomes Phosphatidylcholines Molecular Biology |
| Zdroj: | Archives of Biochemistry and Biophysics. 209:385-395 |
| ISSN: | 0003-9861 |
| DOI: | 10.1016/0003-9861(81)90296-4 |
| Popis: | A sensitive, quantitative assay has been developed which measures the extent of liposome fusion by monitoring fluorescence resonance energy transfer between two lipid analogs originally in separate membranes. This transfer of photon energy from donor to acceptor molecules occurs only if both probes are in the same membrane. Energy transfer is measured as quenching of the donor probe's fluorescence emission. The extent of fusion was estimated by comparing the quenching due to the fusion protocol with the maximum quenching from “mock-fused” vesicles. This assay was used to investigate the effects of calcium ion concentration, calcium ion permeability, and lipid composition on fusion competence. The calcium concentration threshold and extent of fusion was a function of lipid composition. At a given molar percentage of phosphatidylserine, increasing the phosphatidylcholine content raised the threshold. The extent of fusion decreased when the molar percentage of phosphatidylserine was decreased. The inclusion of either cholesterol or phosphatidylethanolamine facilitated fusion competence, but the latter was more effective. Increasing the calcium ion permeability by adding the ionophore X-537a moderately enhanced the extent of fusion in most cases, although it never appreciably affected the threshold. X-537a did not enhance fusion in the presence of unsaturated phosphatidylethanolamine. Liposomes containing unsaturated phosphatidylethanolamine had an optimum calcium ion concentration for fusion in the mid-range of the divalent cation concentrations. We conclude that it is possible for large, unilamellar vesicles with near physiological molar percentages of phosphatidylserine and phosphatidylethanolamine to undergo divalent cation-induced fusion at calcium ion concentrations in the millimolar range. This finding provides a useful model system for investigating mechanisms of such phenomena as exocytosis and cell-cell fusion. |
| Databáze: | OpenAIRE |
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