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Physical Routes to Primitive Cells: An Experimental Model Based on the Spontaneous Entrapment of Enzymes inside Micrometer-Sized Liposomes.

D'Aguanno E, Altamura E, Mavelli F, Fahr A, Stano P, Luisi PL - Life (Basel) (2015)

Bottom Line: We have reported that proteins and ribosomes can be encapsulated very efficiently, against statistical expectations, inside a small number of liposomes.Moreover the transcription-translation mixture, which realistically mimics a sort of minimal metabolic network, can be functionally reconstituted in liposomes owing to a self-concentration mechanism.Here we firstly summarize the recent advancements in this research line, highlighting how these results open a new vista on the phenomena that could have been important for the formation of functional primitive cells.

View Article: PubMed Central - PubMed

Affiliation: Science Department, Roma Tre University, Viale G. Marconi 446, I-00146 Rome, Italy. Alfred.Fahr@uni-jena.de.

ABSTRACT
How did primitive living cells originate? The formation of early cells, which were probably solute-filled vesicles capable of performing a rudimentary metabolism (and possibly self-reproduction), is still one of the big unsolved questions in origin of life. We have recently used lipid vesicles (liposomes) as primitive cell models, aiming at the study of the physical mechanisms for macromolecules encapsulation. We have reported that proteins and ribosomes can be encapsulated very efficiently, against statistical expectations, inside a small number of liposomes. Moreover the transcription-translation mixture, which realistically mimics a sort of minimal metabolic network, can be functionally reconstituted in liposomes owing to a self-concentration mechanism. Here we firstly summarize the recent advancements in this research line, highlighting how these results open a new vista on the phenomena that could have been important for the formation of functional primitive cells. Then, we present new evidences on the non-random entrapment of macromolecules (proteins, dextrans) in phospholipid vesicle, and in particular we show how enzymatic reactions can be accelerated because of the enhancement of their concentration inside liposomes.

No MeSH data available.


Related in: MedlinePlus

Bright field (left) and fluorescence confocal images (center, right) of lipid vesicles prepared by the film hydration method (M1) starting from a FITC-dextran solution. Vesicles were made of POPC and 0.05 mol% DOPE-lissamine-rhodamine in order to be red-fluorescent (central image). Note that despite the abundant presence of vesicles, only few of them have encapsulated a high amount of green-fluorescent solute (right image) so to appear more fluorescent than the background.
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life-05-00969-f007: Bright field (left) and fluorescence confocal images (center, right) of lipid vesicles prepared by the film hydration method (M1) starting from a FITC-dextran solution. Vesicles were made of POPC and 0.05 mol% DOPE-lissamine-rhodamine in order to be red-fluorescent (central image). Note that despite the abundant presence of vesicles, only few of them have encapsulated a high amount of green-fluorescent solute (right image) so to appear more fluorescent than the background.

Mentions: Figure 6 shows a set of typical images obtained by confocal microscopy. Similar images have been obtained for all macromolecular solutes investigated in this work. The results can be summarized as follows. When solutes alone were imaged, a homogeneous fluorescence was always observed. Aggregates were observed only in very rare cases. When vesicles were prepared in the presence of solutes, in all methods and for all lipid concentrations, and for all solutes, we have always observed a small but significant number of vesicles (somehow visible also in bright field) whose fluorescence was higher than the background. If we call F0 the background fluorescence, and F the vesicle fluorescence, it is possible to define, for each visible vesicle, an in/out fluorescence ratio rF = F/F0 that indicates how many times intra-vesicle fluorescence is higher than background fluorescence, and therefore how many times solutes have been concentrated inside a certain vesicle. As evidenced by carrying out control experiments with fluorescent-labeled lipids (Figure 7), the great majority of vesicles are not visible because their internal fluorescence is very near F0 (indicating that they have encapsulated the expected number of solutes). On average, less than 1%–2% of vesicles were more fluorescent than the background.


Physical Routes to Primitive Cells: An Experimental Model Based on the Spontaneous Entrapment of Enzymes inside Micrometer-Sized Liposomes.

D'Aguanno E, Altamura E, Mavelli F, Fahr A, Stano P, Luisi PL - Life (Basel) (2015)

Bright field (left) and fluorescence confocal images (center, right) of lipid vesicles prepared by the film hydration method (M1) starting from a FITC-dextran solution. Vesicles were made of POPC and 0.05 mol% DOPE-lissamine-rhodamine in order to be red-fluorescent (central image). Note that despite the abundant presence of vesicles, only few of them have encapsulated a high amount of green-fluorescent solute (right image) so to appear more fluorescent than the background.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390888&req=5

life-05-00969-f007: Bright field (left) and fluorescence confocal images (center, right) of lipid vesicles prepared by the film hydration method (M1) starting from a FITC-dextran solution. Vesicles were made of POPC and 0.05 mol% DOPE-lissamine-rhodamine in order to be red-fluorescent (central image). Note that despite the abundant presence of vesicles, only few of them have encapsulated a high amount of green-fluorescent solute (right image) so to appear more fluorescent than the background.
Mentions: Figure 6 shows a set of typical images obtained by confocal microscopy. Similar images have been obtained for all macromolecular solutes investigated in this work. The results can be summarized as follows. When solutes alone were imaged, a homogeneous fluorescence was always observed. Aggregates were observed only in very rare cases. When vesicles were prepared in the presence of solutes, in all methods and for all lipid concentrations, and for all solutes, we have always observed a small but significant number of vesicles (somehow visible also in bright field) whose fluorescence was higher than the background. If we call F0 the background fluorescence, and F the vesicle fluorescence, it is possible to define, for each visible vesicle, an in/out fluorescence ratio rF = F/F0 that indicates how many times intra-vesicle fluorescence is higher than background fluorescence, and therefore how many times solutes have been concentrated inside a certain vesicle. As evidenced by carrying out control experiments with fluorescent-labeled lipids (Figure 7), the great majority of vesicles are not visible because their internal fluorescence is very near F0 (indicating that they have encapsulated the expected number of solutes). On average, less than 1%–2% of vesicles were more fluorescent than the background.

Bottom Line: We have reported that proteins and ribosomes can be encapsulated very efficiently, against statistical expectations, inside a small number of liposomes.Moreover the transcription-translation mixture, which realistically mimics a sort of minimal metabolic network, can be functionally reconstituted in liposomes owing to a self-concentration mechanism.Here we firstly summarize the recent advancements in this research line, highlighting how these results open a new vista on the phenomena that could have been important for the formation of functional primitive cells.

View Article: PubMed Central - PubMed

Affiliation: Science Department, Roma Tre University, Viale G. Marconi 446, I-00146 Rome, Italy. Alfred.Fahr@uni-jena.de.

ABSTRACT
How did primitive living cells originate? The formation of early cells, which were probably solute-filled vesicles capable of performing a rudimentary metabolism (and possibly self-reproduction), is still one of the big unsolved questions in origin of life. We have recently used lipid vesicles (liposomes) as primitive cell models, aiming at the study of the physical mechanisms for macromolecules encapsulation. We have reported that proteins and ribosomes can be encapsulated very efficiently, against statistical expectations, inside a small number of liposomes. Moreover the transcription-translation mixture, which realistically mimics a sort of minimal metabolic network, can be functionally reconstituted in liposomes owing to a self-concentration mechanism. Here we firstly summarize the recent advancements in this research line, highlighting how these results open a new vista on the phenomena that could have been important for the formation of functional primitive cells. Then, we present new evidences on the non-random entrapment of macromolecules (proteins, dextrans) in phospholipid vesicle, and in particular we show how enzymatic reactions can be accelerated because of the enhancement of their concentration inside liposomes.

No MeSH data available.


Related in: MedlinePlus