When scientists prepare a batch of proteins to study, such as antibodies that detect cancer, they lose some of the precious product in a tangled, gummy snarl. Unwinding those proteins and then letting them refold in their proper shapes is a tedious, sometimes days-long process, and it usually salvages only some of the material. It’s as hard as, say, unboiling an egg.
But now, with actual snarled proteins from boiled egg whites, Gregory Weiss’s lab can do exactly that—unboil or untangle proteins—in just minutes. Recovering such molecules would be a powerful boost for biotech research and the manufacturing industry, which rely on proteins for everything from therapeutic drugs to laundry detergent to biofuels. “When you go to make proteins, you find very quickly it often doesn’t come out as this beautiful, crystal clear, well folded sample,” says Weiss, a biochemical researcher at the University of California, Irvine. “You get this gunky mess that actually looks a lot like egg whites.”
Weiss’s group revitalized proteins with a specialized machine called a vortex fluid device. They described the process in a paper released online in ChemBioChem. Weiss first saw the machine on a visit to Flinders University in Australia. Researchers there, led by Colin Raston, built the device to control a variety of complicated chemical reactions at the molecular level. The device places molecules in a liquid and sends it through a spinning, open-ended test tube. The liquid spreads out into a thin layer, just a few hundred microns thick, and the forces in the rapidly moving tube transfer energy into the molecules in a controlled way. (A micron is one millionth of a meter.)
When Weiss saw data showing the device peeling tightly bound graphene—sheets of carbon only a few atoms thick—off of a block of graphite, he immediately thought it could be the solution to his protein tangles. He turned to an easy protein source: the egg. An egg white is made of water containing a variety of proteins, including lysozyme, which plays a part in the immune system. When the white is boiled, the heat breaks some structural bonds in the proteins, making them lose their precise, folded forms. The proteins clump together and fold into a solid mass.
To recover the lysozyme the researchers start by dissolving the egg white overnight in a solution that breaks the clumps apart. They come back the next day to a clear solution full of unfolded proteins.
Refolding is the real challenge. Usually the solution is slowly pulled away and diluted bit by bit until the proteins can refold without crashing back together into a tangle. Other methods use heat or pressure to help the process along but they take a lot of energy and can damage the proteins.
Instead, Weiss’s group whirls the unfolded proteins through the vortex fluid device, where they fan out in a thin layer and separate from their neighbors. This allows the molecules to refold without retangling. By adjusting the speed and rotation, scientists can fine-tune the force of the vortex, making it strong enough to pull proteins apart from one another but gentle enough to let them refold into their natural shapes.
Different proteins call for different procedures. When the scientists first tried restoring a protein produced by Escherichia coli bacteria that was three times larger than the egg protein, it would not refold. They managed to coax it into action by binding one end of the protein to a heavy bead, so that end would be more fixed in place. This mimicked the way the protein naturally folds bit by bit as it is produced in the cell, by a protein-making organelle called a ribosome.
The researchers now plan to build a larger-scale vortex machine and explore the different solutions, levels of force and settings that allow different proteins to refold, many of which are not currently cost-effective to purify. If it is effective on different molecules, the vortex approach could make a big difference in biotechnology, says David Rabuka, a chemical biologist with California-based Catalent Pharma Solutions, which helps develop and analyze drugs. “I work with many, many proteins that drive me nuts,” he says. “We’re always bumping up against the technical hurdles of being able to produce useful amounts.” This type of machine might be able to surmount those obstacles, he thinks.
Weiss anticipates that the vortex will catch the interest of many different disciplines. After all, proteins are used as medicine, research tools and industrial catalysts. “If we have ways of accelerating the production of proteins—making it easier, making it faster, requiring less water—all those things will have the effect of dropping the costs,” he says. Making this happen will take longer than boiling an egg but a lot of manufacturers and scientists will be watching closely.