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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

Effects of lipid composition on the mechanical properties of liposomes. (a)–(d) Results obtained from liposomes made from PC and PG; mixing ratios (mol/mol) of PC and PG are 9:1 (a); 4:1 (b); 2:1 (c) and 1:1 (d). (e) Results obtained from liposomes made from PG alone. From (a) to (e), the average and S.D. of the positions of end points of the plots in each panel is also indicated. (f) In order to investigate the dependency of the mechanical properties of liposomes against the content of PG, the average and S.D. shown in panels (a) to (e) are redrawn together with different colors (also see Supplemental Figure S1). The correspondence of color and composition of PC and PG is indicated at the bottom left of the panel. Between the case when the mixing ratio of PC and PG was 9:1 and other cases, in the increasing distance required for the projection formation or the moving out of the bead, p-values of t-tests are <0.005. (g) In order to investigate the effect of liposome size, the results shown in (b) are redrawn. Each plot is colored according to the diameter of the corresponding liposome. The correspondence of color and the range of liposome diameter is indicated at the bottom of panel (h). (h) For each range of liposome diameter, the average and S.D. of the positions of end points of the plots shown in (g) are obtained and indicated by the different colors. In the case when the number of the plots is <3, only the average is indicated (also see Supplemental Figure S2). (i) Results obtained from liposomes made from PE and PG (1:1, mol/mol). (j) and (k) Results obtained from liposomes made from PC and PA; the mixing ratios (mol/mol) of PC and PA are 4:1 (j) and 1:1 (k). (l) and (m) Results obtained from liposomes made from PG and PA. Mixing ratios (mol/mol) of PG and PA are 2:1 (l) and 1:1 (m). In (i)–(m), the average and S.D. of the ending positions of plots shown in each panel are indicated. In each condition, the number of the plots (N) is 16 (a); 30 (b); 16 (c); 17 (d); 22 (e); 12 (i); 19 (j); 13 (k); 11 (l); or 17 (m). Milli-Q water was used to swell the lipid films to prepare liposomes. All phospholipids used were obtained from native sources [13,24,25]. Measurements were carried out at 25 °C. The average and S.D. of the ending positions of plots shown in all panels are shown in Supplemental Table S1.
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membranes-05-00022-f002: Effects of lipid composition on the mechanical properties of liposomes. (a)–(d) Results obtained from liposomes made from PC and PG; mixing ratios (mol/mol) of PC and PG are 9:1 (a); 4:1 (b); 2:1 (c) and 1:1 (d). (e) Results obtained from liposomes made from PG alone. From (a) to (e), the average and S.D. of the positions of end points of the plots in each panel is also indicated. (f) In order to investigate the dependency of the mechanical properties of liposomes against the content of PG, the average and S.D. shown in panels (a) to (e) are redrawn together with different colors (also see Supplemental Figure S1). The correspondence of color and composition of PC and PG is indicated at the bottom left of the panel. Between the case when the mixing ratio of PC and PG was 9:1 and other cases, in the increasing distance required for the projection formation or the moving out of the bead, p-values of t-tests are <0.005. (g) In order to investigate the effect of liposome size, the results shown in (b) are redrawn. Each plot is colored according to the diameter of the corresponding liposome. The correspondence of color and the range of liposome diameter is indicated at the bottom of panel (h). (h) For each range of liposome diameter, the average and S.D. of the positions of end points of the plots shown in (g) are obtained and indicated by the different colors. In the case when the number of the plots is <3, only the average is indicated (also see Supplemental Figure S2). (i) Results obtained from liposomes made from PE and PG (1:1, mol/mol). (j) and (k) Results obtained from liposomes made from PC and PA; the mixing ratios (mol/mol) of PC and PA are 4:1 (j) and 1:1 (k). (l) and (m) Results obtained from liposomes made from PG and PA. Mixing ratios (mol/mol) of PG and PA are 2:1 (l) and 1:1 (m). In (i)–(m), the average and S.D. of the ending positions of plots shown in each panel are indicated. In each condition, the number of the plots (N) is 16 (a); 30 (b); 16 (c); 17 (d); 22 (e); 12 (i); 19 (j); 13 (k); 11 (l); or 17 (m). Milli-Q water was used to swell the lipid films to prepare liposomes. All phospholipids used were obtained from native sources [13,24,25]. Measurements were carried out at 25 °C. The average and S.D. of the ending positions of plots shown in all panels are shown in Supplemental Table S1.

Mentions: It should be noted that the softness or hardness of liposomes is independent of their size as described later (see Figure 2g and h, and Supplemental Figure S2). Concerning the lipid compositions used for measurement in this study, the size distribution of liposomes prepared is not affected much by the lipid composition (e.g., mixing ratio of PC and PG). Moreover, for the measurements, we used liposomes of a specific size range (about 5–15 μm in diameter).


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)

Effects of lipid composition on the mechanical properties of liposomes. (a)–(d) Results obtained from liposomes made from PC and PG; mixing ratios (mol/mol) of PC and PG are 9:1 (a); 4:1 (b); 2:1 (c) and 1:1 (d). (e) Results obtained from liposomes made from PG alone. From (a) to (e), the average and S.D. of the positions of end points of the plots in each panel is also indicated. (f) In order to investigate the dependency of the mechanical properties of liposomes against the content of PG, the average and S.D. shown in panels (a) to (e) are redrawn together with different colors (also see Supplemental Figure S1). The correspondence of color and composition of PC and PG is indicated at the bottom left of the panel. Between the case when the mixing ratio of PC and PG was 9:1 and other cases, in the increasing distance required for the projection formation or the moving out of the bead, p-values of t-tests are <0.005. (g) In order to investigate the effect of liposome size, the results shown in (b) are redrawn. Each plot is colored according to the diameter of the corresponding liposome. The correspondence of color and the range of liposome diameter is indicated at the bottom of panel (h). (h) For each range of liposome diameter, the average and S.D. of the positions of end points of the plots shown in (g) are obtained and indicated by the different colors. In the case when the number of the plots is <3, only the average is indicated (also see Supplemental Figure S2). (i) Results obtained from liposomes made from PE and PG (1:1, mol/mol). (j) and (k) Results obtained from liposomes made from PC and PA; the mixing ratios (mol/mol) of PC and PA are 4:1 (j) and 1:1 (k). (l) and (m) Results obtained from liposomes made from PG and PA. Mixing ratios (mol/mol) of PG and PA are 2:1 (l) and 1:1 (m). In (i)–(m), the average and S.D. of the ending positions of plots shown in each panel are indicated. In each condition, the number of the plots (N) is 16 (a); 30 (b); 16 (c); 17 (d); 22 (e); 12 (i); 19 (j); 13 (k); 11 (l); or 17 (m). Milli-Q water was used to swell the lipid films to prepare liposomes. All phospholipids used were obtained from native sources [13,24,25]. Measurements were carried out at 25 °C. The average and S.D. of the ending positions of plots shown in all panels are shown in Supplemental Table S1.
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membranes-05-00022-f002: Effects of lipid composition on the mechanical properties of liposomes. (a)–(d) Results obtained from liposomes made from PC and PG; mixing ratios (mol/mol) of PC and PG are 9:1 (a); 4:1 (b); 2:1 (c) and 1:1 (d). (e) Results obtained from liposomes made from PG alone. From (a) to (e), the average and S.D. of the positions of end points of the plots in each panel is also indicated. (f) In order to investigate the dependency of the mechanical properties of liposomes against the content of PG, the average and S.D. shown in panels (a) to (e) are redrawn together with different colors (also see Supplemental Figure S1). The correspondence of color and composition of PC and PG is indicated at the bottom left of the panel. Between the case when the mixing ratio of PC and PG was 9:1 and other cases, in the increasing distance required for the projection formation or the moving out of the bead, p-values of t-tests are <0.005. (g) In order to investigate the effect of liposome size, the results shown in (b) are redrawn. Each plot is colored according to the diameter of the corresponding liposome. The correspondence of color and the range of liposome diameter is indicated at the bottom of panel (h). (h) For each range of liposome diameter, the average and S.D. of the positions of end points of the plots shown in (g) are obtained and indicated by the different colors. In the case when the number of the plots is <3, only the average is indicated (also see Supplemental Figure S2). (i) Results obtained from liposomes made from PE and PG (1:1, mol/mol). (j) and (k) Results obtained from liposomes made from PC and PA; the mixing ratios (mol/mol) of PC and PA are 4:1 (j) and 1:1 (k). (l) and (m) Results obtained from liposomes made from PG and PA. Mixing ratios (mol/mol) of PG and PA are 2:1 (l) and 1:1 (m). In (i)–(m), the average and S.D. of the ending positions of plots shown in each panel are indicated. In each condition, the number of the plots (N) is 16 (a); 30 (b); 16 (c); 17 (d); 22 (e); 12 (i); 19 (j); 13 (k); 11 (l); or 17 (m). Milli-Q water was used to swell the lipid films to prepare liposomes. All phospholipids used were obtained from native sources [13,24,25]. Measurements were carried out at 25 °C. The average and S.D. of the ending positions of plots shown in all panels are shown in Supplemental Table S1.
Mentions: It should be noted that the softness or hardness of liposomes is independent of their size as described later (see Figure 2g and h, and Supplemental Figure S2). Concerning the lipid compositions used for measurement in this study, the size distribution of liposomes prepared is not affected much by the lipid composition (e.g., mixing ratio of PC and PG). Moreover, for the measurements, we used liposomes of a specific size range (about 5–15 μm in diameter).

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