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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

(a) Plotted results (left) and dark-field images (right) of liposomes prepared from PC and PG (1:1, mol/mol). The condition of solution, the solute and its concentration is indicated at the top of each row. HEPES-buffer with or without BSA, fetuin, Histone H1 or sucrose was used for swelling the lipid films to prepare liposomes. The PC and PG used were obtained from native sources. In each plot, the average and S.D. of the ending positions of plots are indicated (N is 14 (HEPES-buffer alone, control), 15 (2.0 mg/mL (5.8 mM) sucrose), 11 (0.2 mg/mL (3 μM) BSA), 14 (2.0 mg/mL (30 μM) BSA), 13 (0.2 mg/mL (4 μM) fetuin) and 13 (0.01 mg/mL (0.5 μM) Histone H1)). The numerical of the average and S.D. is shown in Supplemental Table S3. Between the control and the cases of liposomes with 2.0 mg/mL BSA or 0.2 mg/mL fetuin, p-values are <0.001 for the maximum force and <0.005 for the increasing distance required for formation of the projection or the moving out of the bead. Bar indicates 10 μm. Observations and measurements were carried out at 25 °C. Note that the dark-field image of liposomes with 2.0 mg/mL BSA is the same photograph used in Figure 6. (b) Average values of the maximum force and increase in separation are summarized against the BSA concentration. The data shown in graphs of the first, third and fourth panels of (a) are used.
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membranes-05-00022-f007: (a) Plotted results (left) and dark-field images (right) of liposomes prepared from PC and PG (1:1, mol/mol). The condition of solution, the solute and its concentration is indicated at the top of each row. HEPES-buffer with or without BSA, fetuin, Histone H1 or sucrose was used for swelling the lipid films to prepare liposomes. The PC and PG used were obtained from native sources. In each plot, the average and S.D. of the ending positions of plots are indicated (N is 14 (HEPES-buffer alone, control), 15 (2.0 mg/mL (5.8 mM) sucrose), 11 (0.2 mg/mL (3 μM) BSA), 14 (2.0 mg/mL (30 μM) BSA), 13 (0.2 mg/mL (4 μM) fetuin) and 13 (0.01 mg/mL (0.5 μM) Histone H1)). The numerical of the average and S.D. is shown in Supplemental Table S3. Between the control and the cases of liposomes with 2.0 mg/mL BSA or 0.2 mg/mL fetuin, p-values are <0.001 for the maximum force and <0.005 for the increasing distance required for formation of the projection or the moving out of the bead. Bar indicates 10 μm. Observations and measurements were carried out at 25 °C. Note that the dark-field image of liposomes with 2.0 mg/mL BSA is the same photograph used in Figure 6. (b) Average values of the maximum force and increase in separation are summarized against the BSA concentration. The data shown in graphs of the first, third and fourth panels of (a) are used.

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)

(a) Plotted results (left) and dark-field images (right) of liposomes prepared from PC and PG (1:1, mol/mol). The condition of solution, the solute and its concentration is indicated at the top of each row. HEPES-buffer with or without BSA, fetuin, Histone H1 or sucrose was used for swelling the lipid films to prepare liposomes. The PC and PG used were obtained from native sources. In each plot, the average and S.D. of the ending positions of plots are indicated (N is 14 (HEPES-buffer alone, control), 15 (2.0 mg/mL (5.8 mM) sucrose), 11 (0.2 mg/mL (3 μM) BSA), 14 (2.0 mg/mL (30 μM) BSA), 13 (0.2 mg/mL (4 μM) fetuin) and 13 (0.01 mg/mL (0.5 μM) Histone H1)). The numerical of the average and S.D. is shown in Supplemental Table S3. Between the control and the cases of liposomes with 2.0 mg/mL BSA or 0.2 mg/mL fetuin, p-values are <0.001 for the maximum force and <0.005 for the increasing distance required for formation of the projection or the moving out of the bead. Bar indicates 10 μm. Observations and measurements were carried out at 25 °C. Note that the dark-field image of liposomes with 2.0 mg/mL BSA is the same photograph used in Figure 6. (b) Average values of the maximum force and increase in separation are summarized against the BSA concentration. The data shown in graphs of the first, third and fourth panels of (a) are used.
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membranes-05-00022-f007: (a) Plotted results (left) and dark-field images (right) of liposomes prepared from PC and PG (1:1, mol/mol). The condition of solution, the solute and its concentration is indicated at the top of each row. HEPES-buffer with or without BSA, fetuin, Histone H1 or sucrose was used for swelling the lipid films to prepare liposomes. The PC and PG used were obtained from native sources. In each plot, the average and S.D. of the ending positions of plots are indicated (N is 14 (HEPES-buffer alone, control), 15 (2.0 mg/mL (5.8 mM) sucrose), 11 (0.2 mg/mL (3 μM) BSA), 14 (2.0 mg/mL (30 μM) BSA), 13 (0.2 mg/mL (4 μM) fetuin) and 13 (0.01 mg/mL (0.5 μM) Histone H1)). The numerical of the average and S.D. is shown in Supplemental Table S3. Between the control and the cases of liposomes with 2.0 mg/mL BSA or 0.2 mg/mL fetuin, p-values are <0.001 for the maximum force and <0.005 for the increasing distance required for formation of the projection or the moving out of the bead. Bar indicates 10 μm. Observations and measurements were carried out at 25 °C. Note that the dark-field image of liposomes with 2.0 mg/mL BSA is the same photograph used in Figure 6. (b) Average values of the maximum force and increase in separation are summarized against the BSA concentration. The data shown in graphs of the first, third and fourth panels of (a) are used.
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