Cell membranes are able to withstand high levels of stretching and bending, but only recently have scientists begun to properly appreciate the organization and beneficial functions contained within these membranes. An interdisciplinary research group is trying to exploit these principles to develop synthetic systems consisting of simple membranes and complex fluids
![The molecules that make up a liquid crystal face the same direction when in the right position [Courtesy: UW-Madison Materials Research Science and Engineering Center]](https://www.hayadan.org.il/images/content3/2016/05/LiqCrystalVesicles-500x3171-500x317.jpg)
[Translation by Dr. Nachmani Moshe]
Cell membranes are able to withstand high levels of stretching and bending, but only recently have scientists begun to properly appreciate the organization and beneficial functions contained within these membranes. An interdisciplinary research group is trying to exploit these principles to develop synthetic systems consisting of simple membranes and complex fluids.
All cells in the living world actually consist of soft "balloons" filled with water, proteins and DNA, surrounded by oily membranes. These membranes withstand high levels of stretching and bending, but only recently have scientists begun to properly appreciate the organization and useful functions contained within these membranes. A research group from the University of Wisconsin-Madison is trying to utilize these principles in synthetic systems consisting of simple membranes and complex fluids. The research findings, recently published in the scientific journal Proceedings of the National Academy of Sciences, reveal that previously unappreciated parameters can shape soft materials such as biological membranes. "What we are trying to do is take advantage of design principles contained within bacteria and see if they can be translated into synthetic systems," says the lead researcher.
Researchers previously believed that the pressure under which the membranes stand plays an important role in the way organisms control the compositions of substances found in different areas on the surface of their cells. For example, one paper investigated how membrane elastic energies might drive defined cellular components to the edges of bacterial cells. As part of their research, the scientists created a tiny synthetic shell known as a vesicle, which consists of materials similar to the membranes that surround living cells. The tiny spheres are an approximation of biological membranes, without the complex internal mechanisms or the external components distorting the research results. In order to shrink, press and exert effort on the membrane spheres, the researchers immersed the materials in a special liquid crystal liquid. Liquid crystals, such as those commonly used in digital watch displays, can exist in different states. Like most liquids, the components within them move freely in all directions. At the same time, at certain temperatures or electromagnetic conditions, the molecules that make up the liquid crystal adopt the same orientation, which leads to a situation where they all face the same direction.
The researchers discovered that the change in the state of the liquid crystal, in which were the oily globules that simulated the biological membranes, caused deformations in those globules. However - not all spheroids reacted in the same way. While the larger spheres remained in their original shape, smaller spheres shrank and became flatter, similar to a football. "In general, when we think of membranes, we mainly refer to forces related to elasticity," notes the lead researcher. "However, it turns out that the curvature ability of the membranes has nothing to do with their shapes." Contrary to expectations, competition between the surface tension and the elasticity of the liquid crystal causes the deformation of the spherules, regardless of the original stiffness or flexibility of the cell membranes. "At no point until now did we think that surface tension would be relevant as part of solving this puzzle." The researchers hope to continue to find out what is the source of the surface tension of the system being tested. In addition, they intend to investigate whether similar forces can affect the components inside the membranes.
