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Effects of lipid composition and solution conditions on the mechanical properties of membrane vesicles.

Kato N, Ishijima A, Inaba T, Nomura F, Takeda S, Takiguchi K - Membranes (Basel) (2015)

Bottom Line: Liposomes prepared with a synthetic dimyristoylphosphatidylcholine, which has uniform hydrocarbon chains, were transformed easily compared with liposomes prepared using natural phosphatidylcholine.Surprisingly, bovine serum albumin or fetuin (soluble proteins that do not bind to membranes) decreased liposomal membrane rigidity, whereas the same concentration of sucrose showed no particular effect.These results show that the mechanical properties of liposomes depend on their lipid composition and environment.

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan. k614899x@m2.aichi-c.ed.jp.

ABSTRACT
The mechanical properties of cell-sized giant unilamellar liposomes were studied by manipulating polystyrene beads encapsulated within the liposomes using double-beam laser tweezers. Mechanical forces were applied to the liposomes from within by moving the beads away from each other, which caused the liposomes to elongate. Subsequently, a tubular membrane projection was generated in the tip at either end of the liposome, or the bead moved out from the laser trap. The force required for liposome transformation reached maximum strength just before formation of the projection or the moving out of the bead. By employing this manipulation system, we investigated the effects of membrane lipid compositions and environment solutions on the mechanical properties. With increasing content of acidic phospholipids, such as phosphatidylglycerol or phosphatidic acid, a larger strength of force was required for the liposome transformation. Liposomes prepared with a synthetic dimyristoylphosphatidylcholine, which has uniform hydrocarbon chains, were transformed easily compared with liposomes prepared using natural phosphatidylcholine. Surprisingly, bovine serum albumin or fetuin (soluble proteins that do not bind to membranes) decreased liposomal membrane rigidity, whereas the same concentration of sucrose showed no particular effect. These results show that the mechanical properties of liposomes depend on their lipid composition and environment.

No MeSH data available.


Related in: MedlinePlus

Dark-field images of liposomes prepared in the presence (right column) or absence (left column) of BSA. The lipid composition is indicated on the left of each row. HEPES-buffer with or without 2.0 mg/mL (30 μM) BSA was used for swelling the lipid films to prepare liposomes. All phospholipids used here were obtained from native sources. Bar indicates 10 μm. Observations were carried out at 25 °C.
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membranes-05-00022-f006: Dark-field images of liposomes prepared in the presence (right column) or absence (left column) of BSA. The lipid composition is indicated on the left of each row. HEPES-buffer with or without 2.0 mg/mL (30 μM) BSA was used for swelling the lipid films to prepare liposomes. All phospholipids used here were obtained from native sources. Bar indicates 10 μm. Observations were carried out at 25 °C.

Mentions: Liposomes made from PG alone, PG and PA, PE and PG, PC and PG, and PC and PA (1:1 mol/mol) prepared using HEPES-buffer were spherical and stable (Figure 6, left column). When liposomes with the same lipid compositions were prepared using HEPES-buffer with 2.0 mg/mL BSA, in cases where the lipid composition contained PA, liposomes kept their stable spherical shape, but in the other cases, liposomes tended to show elongated unstable shapes and the majority of them were fluctuating their shapes (Figure 6, right column). Following the addition of BSA to the solution, liposomes were softened (Figure 7). That observation suggests that if the surrounding solution contains a protein, the behavior of liposomes will be affected even though the protein does not bind directly to the membrane. The difference in liposomal behavior between the cases of lipid compositions with or without PA may be attributable to the effect of PA that slightly hardens the membranes as described above (see Section 2.1.2, Figure 2e, and j–m).


Effects of lipid composition and solution conditions on the mechanical properties of membrane vesicles.

Kato N, Ishijima A, Inaba T, Nomura F, Takeda S, Takiguchi K - Membranes (Basel) (2015)

Dark-field images of liposomes prepared in the presence (right column) or absence (left column) of BSA. The lipid composition is indicated on the left of each row. HEPES-buffer with or without 2.0 mg/mL (30 μM) BSA was used for swelling the lipid films to prepare liposomes. All phospholipids used here were obtained from native sources. Bar indicates 10 μm. Observations were carried out at 25 °C.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4384090&req=5

membranes-05-00022-f006: Dark-field images of liposomes prepared in the presence (right column) or absence (left column) of BSA. The lipid composition is indicated on the left of each row. HEPES-buffer with or without 2.0 mg/mL (30 μM) BSA was used for swelling the lipid films to prepare liposomes. All phospholipids used here were obtained from native sources. Bar indicates 10 μm. Observations were carried out at 25 °C.
Mentions: Liposomes made from PG alone, PG and PA, PE and PG, PC and PG, and PC and PA (1:1 mol/mol) prepared using HEPES-buffer were spherical and stable (Figure 6, left column). When liposomes with the same lipid compositions were prepared using HEPES-buffer with 2.0 mg/mL BSA, in cases where the lipid composition contained PA, liposomes kept their stable spherical shape, but in the other cases, liposomes tended to show elongated unstable shapes and the majority of them were fluctuating their shapes (Figure 6, right column). Following the addition of BSA to the solution, liposomes were softened (Figure 7). That observation suggests that if the surrounding solution contains a protein, the behavior of liposomes will be affected even though the protein does not bind directly to the membrane. The difference in liposomal behavior between the cases of lipid compositions with or without PA may be attributable to the effect of PA that slightly hardens the membranes as described above (see Section 2.1.2, Figure 2e, and j–m).

Bottom Line: Liposomes prepared with a synthetic dimyristoylphosphatidylcholine, which has uniform hydrocarbon chains, were transformed easily compared with liposomes prepared using natural phosphatidylcholine.Surprisingly, bovine serum albumin or fetuin (soluble proteins that do not bind to membranes) decreased liposomal membrane rigidity, whereas the same concentration of sucrose showed no particular effect.These results show that the mechanical properties of liposomes depend on their lipid composition and environment.

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan. k614899x@m2.aichi-c.ed.jp.

ABSTRACT
The mechanical properties of cell-sized giant unilamellar liposomes were studied by manipulating polystyrene beads encapsulated within the liposomes using double-beam laser tweezers. Mechanical forces were applied to the liposomes from within by moving the beads away from each other, which caused the liposomes to elongate. Subsequently, a tubular membrane projection was generated in the tip at either end of the liposome, or the bead moved out from the laser trap. The force required for liposome transformation reached maximum strength just before formation of the projection or the moving out of the bead. By employing this manipulation system, we investigated the effects of membrane lipid compositions and environment solutions on the mechanical properties. With increasing content of acidic phospholipids, such as phosphatidylglycerol or phosphatidic acid, a larger strength of force was required for the liposome transformation. Liposomes prepared with a synthetic dimyristoylphosphatidylcholine, which has uniform hydrocarbon chains, were transformed easily compared with liposomes prepared using natural phosphatidylcholine. Surprisingly, bovine serum albumin or fetuin (soluble proteins that do not bind to membranes) decreased liposomal membrane rigidity, whereas the same concentration of sucrose showed no particular effect. These results show that the mechanical properties of liposomes depend on their lipid composition and environment.

No MeSH data available.


Related in: MedlinePlus