The big challenge for the production of synthetic cells is that they must be able to divide in order to have offspring. In the magazine Applied Chemistry, a team from Heidelberg introduced a repeatable mechanism for the division of synthetic vesicles. It is based on osmosis and can be controlled by an enzymatic reaction or light.
Organisms cannot simply arise from inanimate material (“abiogenesis”), cells always come from already existing cells. The prospects for newly built synthetic cells are shifting this paradigm. However, one of the obstacles on this path is the issue of controlled division – a condition for the existence of “offspring”.
A team from the Max Planck Institute for Medical Research in Heidelberg, Heidelberg University, Max Planck School Matter to Life and Exzellenzcluster 3D Matter Made to Order, led by Kerstin Göpfrich, has now reached a milestone by achieving complete control over vesicle division. To achieve this, they produced “giant unilamellar vesicles,” which are micrometer-sized bubbles with a shell of a lipid bilayer that resembles a natural membrane. Various lipids are combined to form phase-separated vesicles – vesicles with membrane hemispheres of different composition. When the concentration of solutes in the surrounding solution increases, osmosis causes water to come out of the vesicles through the membrane. This reduces the volume of the vesicles, and at the same time keeps the surface of the membrane equal. The resulting tension on the phase surface deforms the vesicles. They narrow along their “equator” – more and more with an increase in osmotic pressure – until the two halves separate completely and form two (now single-phase) “daughters” with different membrane compositions. When separation occurs depends only on the ratio of the concentration of osmotically active particles (osmolarity) and is independent of the size of the vesicles.
The method of raising osmolarity also does not play a role. The methods used by the team included the use of a sucrose solution and the addition of an enzyme that separates glucose and fructose to slowly increase the concentration. The use of light to initiate the cleavage of molecules in solution has given researchers complete spatial and temporal control over separation. The use of strictly controlled local radiation allowed a selective increase in concentration around a single vesicle, which triggered its selective division.
The team is also able to grow single-phase cells back into phase-separated vesicles by merging them with tiny vesicles that have a different type of membrane. This is made possible by attaching individual strands of DNA to both different types of membranes. They bind to each other and bring the daughter’s membranes and mini-vesicles into very close contact so that they can merge. The resulting giant vesicles can then undergo further cycles of division.
“Although these mechanisms of synthetic division differ significantly from the mechanisms of living cells,” says Göpfrich, “the question arises as to whether similar mechanisms played a role in the beginnings of life on earth or were involved in the formation of intracellular vesicles.”
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Yannik Dreher et al. Division and regrowth of phase-separated giant unilamellar vesicles **, Applied Chemistry International Edition (2020). DOI: 10.1002 / anie.202014174
Citation: Division and growth of synthetic vesicles (2021, March 25) retrieved 25 March 2021 from https://phys.org/news/2021-03-division-growth-synthetic-vesicles.html
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