The cell membrane is one of the most important components of a cell because it separates the interior from the environment and controls the movement of substances in and out of the cell. In a move that brings mankind another step closer to being able to create artificial life forms from scratch, chemists from the University of California, San Diego (UCSD), and Harvard University have created artificial self-assembling cell membranes using a novel chemical reaction. The chemists hope their creation will help shed light on the origins of life.
As the basic structural and functional unit of all known living organisms, the cell is the smallest unit of life that is classified as a living thing. Although there are various theories - meteorites, deep-sea vents, lightning - there is still no scientific consensus regarding the origin of the first cell.
"We don't understand this really fundamental step in our existence, which is how non-living matter went to living matter," said Neal Devaraj, assistant professor of chemistry at UCSD. "So this is a really ripe area to try to understand what knowledge we lack about how that transition might have occurred. That could teach us a lot - even the basic chemical, biological principles that are necessary for life."
Cell membranes are composed of a lipid bilayer usually made mostly of phosopholids that have heads that mix easily with water and tails that repel it. When exposed to water, they arrange themselves to form a double layer with heads out and tails in, forming a barrier that sequesters the contents of the cells. Devaraj and Itay Budin, a graduate student at Harvard University, created similar molecules with a novel reaction that joins two chains of lipids.
"In our system, we use a sort of primitive catalyst, a very simple metal ion," Devaraj said. "The reaction itself is completely artificial. There's no biological equivalent of this chemical reaction. This is how you could have a de novo formation of membranes."
The synthetic membranes were created from a watery emulsion of an oil and detergent that is, on its own, very stable. But the chemists say that adding copper ions results in sturdy vesicles and tubules beginning to bud off the oil droplets. After 24 hours, the oil droplets are gone, having been "consumed" by the self-assembling membranes.
Although a research team from the J. Craig Venter Institute (JVCI) had previously claimed to successfully produce the first self-replicating, synthetic bacterial cell, only its genome was artificial. To claim fully artificial life would also require a synthetic three-dimensional structure to house the information-carrying genome. Something that Deveraj says is, "trivial and can be done in a day. New people who join the lab can make membranes from day one."
Devaraj and Budin's research is published in the Journal of the American Chemical Society.
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