Researchers from Italy were able to assemble a photosynthesis apparatus in an artificial cell. This opens up fundamentally new opportunities for researchers.
As we know, photosynthesis is a reaction that converts the energy of light into the energy of chemical bonds. It is through photosynthesis that plants, using quanta of light, convert carbon dioxide and water into organic compounds and oxygen. All this allows not only the plants themselves to survive, but also millions of other microorganisms that inhabit our world. Note that in plants, the photosynthetic apparatus is located in the membranes of special organelles called chloroplasts. As a result of the work of chloroplasts, a flux of protons is generated through the membrane, due to which a proton gradient arises. Because of this, cells have the ability to store energy by synthesizing high-energy ATP molecules.
Note that some bacteria are capable of photosynthesis. In their case, the location of the photosynthetic apparatus is the cytoplasmic membranes, and the proton gradient is formed between the cytoplasm and the external environment.
Now scientists have paid attention to the photosynthetic apparatus of purple bacteria. The researchers decided to create an artificial photosynthesis system. For this purpose, only the main transmembrane protein of the reaction center of the bacterium Rhodobacter sphaeroides was used, while no auxiliary molecules were used. Similar experiments were carried out earlier: only often scientists faced the problem of protein orientation in membranes. When they were embedded, they "looked" in different directions, which did not allow creating the correct proton gradient. However, now scientists have been able to achieve the creation of a real protocell - a giant lipid vesicle - with reaction centers built into the membrane, oriented in the right direction.
Micelle assembly principle with selective orientation of reaction centers / © Emiliano Altamura et al., PNAS, 2017
To achieve the desired effect, the droplet transfer method was applied. The reaction centers were turned in the required directions due to hydrophobic interactions. The vesicles obtained by the scientists had a diameter of about 20 microns, were stable and had a fairly high density of proteins - they contained approximately one reaction center for 2200 lipid molecules. Due to short flashes of light, scientists were able to find out that photosynthetic proteins in such vesicles are active. The results obtained open up new possibilities for researchers when it comes to artificial photosynthesis.