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From vesicles to protocells: the roles of amphiphilic molecules.

Sakuma Y, Imai M - Life (Basel) (2015)

Bottom Line: It is very challenging to construct protocells from molecular assemblies.Here, we show that simple binary phospholipid vesicles have the potential to reproduce the relevant functions of adhesion, pore formation and self-reproduction of vesicles, by coupling the lipid geometries (spontaneous curvatures) and the phase separation.This achievement will elucidate the pathway from molecular assembly to cellular life.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Tohoku University, Aoba, Sendai 980-8578, Japan. sakuma@bio.phys.tohoku.ac.jp.

ABSTRACT
It is very challenging to construct protocells from molecular assemblies. An important step in this challenge is the achievement of vesicle dynamics that are relevant to cellular functions, such as membrane trafficking and self-reproduction, using amphiphilic molecules. Soft matter physics will play an important role in the development of vesicles that have these functions. Here, we show that simple binary phospholipid vesicles have the potential to reproduce the relevant functions of adhesion, pore formation and self-reproduction of vesicles, by coupling the lipid geometries (spontaneous curvatures) and the phase separation. This achievement will elucidate the pathway from molecular assembly to cellular life.

No MeSH data available.


Related in: MedlinePlus

A series of snapshots of the budding process of a binary vesicle composed of DLPE/DPPC = 2/8. The budding cycle consists of four steps: (1) sphere; (2) budding; (3) complete budding; and (4) recovery of the spherical shape. The green and red pathways show the budding of the second daughter vesicle and the granddaughter vesicle, respectively. The scale bar indicates 5 μm.
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life-05-00651-f021: A series of snapshots of the budding process of a binary vesicle composed of DLPE/DPPC = 2/8. The budding cycle consists of four steps: (1) sphere; (2) budding; (3) complete budding; and (4) recovery of the spherical shape. The green and red pathways show the budding of the second daughter vesicle and the granddaughter vesicle, respectively. The scale bar indicates 5 μm.

Mentions: Through temperature changes, DPPC lipids undergo the main chain transition, i.e., change of the cross-section area, whereas DLPE retains a constant area. This asymmetry is the key to the observed self-reproduction. Thus, the control parameter is the composition of the binary vesicle. When the composition of the GUV was changed to DLPE/DPPC = 2/8, the GUVs showed the budding pathways depicted in Figure 21. Again, the experiment was started from a spherical vesicle at 35 °C (Step 1). By increasing the temperature of the GUV above the Tm, GUVs showed outer budding deformations (Step 2), and then, the buds were completely pinched off; i.e., daughter vesicles were produced by the budding pathway (Step 3). Through decreases in the temperature, the mother and the daughter vesicles recovered a spherical shape (Step 4). During the second temperature cycling, the mother GUV repeated the budding pathway and produced a second daughter vesicle (green pathway), and the first daughter vesicle produced a granddaughter vesicle (red pathway) by the budding mechanism. Again, the budding ability was maintained in the next generation. During multi-temperature cycling, the vesicles consistently divided through the budding mechanism, not via the birthing pathway, which suggests conservation of the composition of the binary GUV. It should be noted that in the self-reproduction of vesicles, membrane molecules that are supplied from the metabolic pathway or the external environment are incorporated into the vesicle membrane, which increases the membrane area. Using this excess area, vesicles deform to the limiting shape and then produce a daughter vesicle. Unfortunately, at present, it is very difficult to couple the model vesicle with the metabolic pathway. Thus, in this model system, the change in the cross-section area due to the main chain transition of the lipid is used to increase the membrane area. The shape deformation pathway observed in this model system is identical with that observed in the reported self-reproduction system [31,32]. Through decreases in the temperature, the area of the model vesicle returns to the initial area, i.e., the system is cyclic. Thus, this model system captures the heart of self-reproduction.


From vesicles to protocells: the roles of amphiphilic molecules.

Sakuma Y, Imai M - Life (Basel) (2015)

A series of snapshots of the budding process of a binary vesicle composed of DLPE/DPPC = 2/8. The budding cycle consists of four steps: (1) sphere; (2) budding; (3) complete budding; and (4) recovery of the spherical shape. The green and red pathways show the budding of the second daughter vesicle and the granddaughter vesicle, respectively. The scale bar indicates 5 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390873&req=5

life-05-00651-f021: A series of snapshots of the budding process of a binary vesicle composed of DLPE/DPPC = 2/8. The budding cycle consists of four steps: (1) sphere; (2) budding; (3) complete budding; and (4) recovery of the spherical shape. The green and red pathways show the budding of the second daughter vesicle and the granddaughter vesicle, respectively. The scale bar indicates 5 μm.
Mentions: Through temperature changes, DPPC lipids undergo the main chain transition, i.e., change of the cross-section area, whereas DLPE retains a constant area. This asymmetry is the key to the observed self-reproduction. Thus, the control parameter is the composition of the binary vesicle. When the composition of the GUV was changed to DLPE/DPPC = 2/8, the GUVs showed the budding pathways depicted in Figure 21. Again, the experiment was started from a spherical vesicle at 35 °C (Step 1). By increasing the temperature of the GUV above the Tm, GUVs showed outer budding deformations (Step 2), and then, the buds were completely pinched off; i.e., daughter vesicles were produced by the budding pathway (Step 3). Through decreases in the temperature, the mother and the daughter vesicles recovered a spherical shape (Step 4). During the second temperature cycling, the mother GUV repeated the budding pathway and produced a second daughter vesicle (green pathway), and the first daughter vesicle produced a granddaughter vesicle (red pathway) by the budding mechanism. Again, the budding ability was maintained in the next generation. During multi-temperature cycling, the vesicles consistently divided through the budding mechanism, not via the birthing pathway, which suggests conservation of the composition of the binary GUV. It should be noted that in the self-reproduction of vesicles, membrane molecules that are supplied from the metabolic pathway or the external environment are incorporated into the vesicle membrane, which increases the membrane area. Using this excess area, vesicles deform to the limiting shape and then produce a daughter vesicle. Unfortunately, at present, it is very difficult to couple the model vesicle with the metabolic pathway. Thus, in this model system, the change in the cross-section area due to the main chain transition of the lipid is used to increase the membrane area. The shape deformation pathway observed in this model system is identical with that observed in the reported self-reproduction system [31,32]. Through decreases in the temperature, the area of the model vesicle returns to the initial area, i.e., the system is cyclic. Thus, this model system captures the heart of self-reproduction.

Bottom Line: It is very challenging to construct protocells from molecular assemblies.Here, we show that simple binary phospholipid vesicles have the potential to reproduce the relevant functions of adhesion, pore formation and self-reproduction of vesicles, by coupling the lipid geometries (spontaneous curvatures) and the phase separation.This achievement will elucidate the pathway from molecular assembly to cellular life.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Tohoku University, Aoba, Sendai 980-8578, Japan. sakuma@bio.phys.tohoku.ac.jp.

ABSTRACT
It is very challenging to construct protocells from molecular assemblies. An important step in this challenge is the achievement of vesicle dynamics that are relevant to cellular functions, such as membrane trafficking and self-reproduction, using amphiphilic molecules. Soft matter physics will play an important role in the development of vesicles that have these functions. Here, we show that simple binary phospholipid vesicles have the potential to reproduce the relevant functions of adhesion, pore formation and self-reproduction of vesicles, by coupling the lipid geometries (spontaneous curvatures) and the phase separation. This achievement will elucidate the pathway from molecular assembly to cellular life.

No MeSH data available.


Related in: MedlinePlus