A team of Penn State researchers has developed a simple artificial cell with which to investigate the organization and function of two of the most basic cell components: the cell membrane and the cytoplasm--the gelatinous fluid that surrounds the structures in living cells. The work could lead to the creation of new drugs that take advantage of properties of cell organization to prevent the development of diseases.
The model cell uses as the cytoplasm a solution of two different polymers, PEG and dextran (Panel A). The image in Panel B is the image in Panel A highlighted with fluorescent dyes. The blue region is PEG, which is concentrated in the outer polymer solution; the green area is the portion of the membrane that contains PEG groups, which interact with the contents of the cell; and the red area is the portion of the membrane with fewer PEG groups, which interact with the contents of the cell to a lesser extent. After exposure to a concentrated solution of sugar, the cell converted to a budded form (Panel C). A dextran-rich mixture filled the bud, while a PEG-rich mixture remained inside the body of the cell. Panel D shows the image in Panel C highlighted with fluorescent dyes. The blue area is the PEG-rich region. This new structure exhibits polarity both in the membrane and in the aqueous interior of the model cell. (Credit: Christine Keating, Penn State)
The team's next step is to create a cascade in polarity. "By creating a model cytoplasm with different compositions, we demonstrated that we can control the behavior of cell membranes," said Keating. "Now we want to find out what will happen if, for example, we add an enzyme whose activity depends on the compositions of the cytoplasm and cell membrane."
Although Keating and her colleagues plan to continue adding components to their model cell, they don't expect to make a real cell. "We aren't trying to generate life here. Rather, we want to understand the physical principles that govern biological systems," said Keating. "For me the big picture is trying to understand how the staggering complexity observed in biological systems might have arisen from seemingly simple chemical and physical principles."