Imagine you’re a chemist, and you’re holding a glass vial in your hand. You stir it, and you don’t see any visible reaction. You may not be surprised – being a chemist, you know that not all reactions are visible, and some require heat. However, then you shake the vial of liquid back and forth in your hand and suddenly, thin sheets of material begin to appear and float around in the liquid. What in the world is going on here?
This strange phenomenon is the result of research from the Berkley National Laboratory. Researchers were investigating how thin sheets of proteins self-assemble. Proteins are long chains of amino acids, and are found throughout our body. Because various parts of the chain are attracted to / repelled by other parts of the chain, proteins tend to “fold” into a specific shape. In the case of the proteins under study, under ideal conditions they formed thin sheets. It’s what chemists call “self-assembly” – the molecules just arrange themselves spontaneously into an ordered arrangement.
The strange result from this research is that stirring (the chemists first choice for agitating a solution) resulted in no protein folding at all. It was not until the vial of protein solution was gently shaked from side to side that the proteins self assembled into the sheets. These new “nanosheets” have a wide range of potential applications including sensing, filtrating, and acting as a growth template for other structures.
But why the shaking, why is that important as compared to the stirring? The researchers on the project believed that the careful motion of the shaking allowed the compression from the air-water interface to precisely fold the protein into the desired shape. During the shaking process, the proteins compress, pushing chains of the proteins together and squeezing them into a nanosheet. This process isn’t possible without the air-water interface, which is why stirring didn’t have the same effect.
Scientists are now investigating not only uses for these protein nanosheets but are also seeing if this process can be expanded to form nanosheets from other materials.
The source of this article can be found at:
Babak Sanii, Romas Kudirka, Andrew Cho, Neeraja Venkateswaran, Gloria K. Olivier, Alexander M. Olson, Helen Tran, R. Marika Harada, Li Tan, Ronald N. Zuckermann. “Shaken, Not Stirred: Collapsing a Peptoid Monolayer To Produce Free-Floating, Stable Nanosheets”. Journal of the American Chemical Society 2011, ASAP on Web.