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pH-dependent fusion of liposomes using titratable polycations
Biochemistry
|January 1, 1985
Summary
Polyhistidine facilitates liposome fusion at acidic pH, offering a model for biological membrane fusion. This fusogen
Area of Science:
- Biochemistry
- Membrane Biophysics
- Lipid Bilayer Dynamics
Background:
- Polylysine-induced liposome fusion is pH-dependent, occurring below the lysyl residue pKa.
- This suggests pH-regulated fusion is achievable using alternative fusogens.
Purpose of the Study:
- To investigate polyhistidine as a pH-regulated fusogen for liposomes.
- To explore the kinetics and lipid mixing extent of polyhistidine-mediated fusion.
Main Methods:
- Liposomes composed of soybean phospholipids or phospholipid-cholesterol mixtures were used.
- Quantitative resonance energy transfer assay measured lipid phase mixing (fusion).
- Fusion extent was assessed across a range of pH values.
Main Results:
- Polyhistidine induced rapid and substantial liposome fusion at pH 6.5 and below, but not at pH 7.4.
- Fusion extent correlated with polyhistidine charge density and increased with acidification.
- Pre-acidification of vesicles slowed fusion kinetics, suggesting pre-aggregation enhances fusion.
Conclusions:
- Polyhistidine enables pH-regulated liposome fusion within a physiological range.
- The rapid kinetics and pH-dependence suggest relevance to biological fusion events.
- Charge density, not total charge, is critical for polyhistidine-mediated fusion.