From trash to treasure
There are thousands of different types of proteins— probably millions—collectively capable of carrying out a huge number of complex processes, and yet they are all made out of just 20 building blocks.
ANTONY said it of Cleopatra—but the same could be said of proteins—‘custom cannot stale their infinite variety’. There are thousands of different types of proteins— probably millions—collectively capable of carrying out a huge number of complex processes, and yet they are all made out of just 20 building blocks. “It’s like having a box of Lego with 20 building bricks, of all different shapes and sizes and with different properties,” says Juliet Gerrard, long-time protein nerd, professor of biochemistry at the University of Canterbury, Director of the Biomolecular Interaction Centre and Principal Investigator of The MacDiarmid Institute. “So if you really understand how those building blocks stick together you can make them do all sorts of things.” Understanding exactly how the building blocks of life interact is allowing scientists to manipulate those processes, which is opening up a plethora of potential and practical applications. “Proteins are interesting in the body, they are interesting in medicine, in making materials, in making electronics, all sorts of things. They are just so versatile, so if you have expertise in one area, you can then apply that knowledge to many different fields.” For her PhD, Gerrard looked at how manipulating a protein in a plant could create a herbicide. Later, at Crop and Food Research, she engineered the way proteins interacted within a food matrix to improve the texture of pastry—the result being fluffier, flakier croissants. Now she and her team are creating protein nanotubes, or nanofibres. “Like carbon nanotubes, but as they are made of protein, they have very different qualities.” They’re much more compatible with aqueous systems, for example, and more receptive to having new functions attached to them than carbon nanotubes. As such, they have a broader range of potential uses; for example, by sticking anti-microbial agents onto them, they can be used to create anti-microbial films. They could be used to create nanocages that could carry and release a cargo of drugs. They could also be used to create superstrong fibres. Think now, of a bullet proof vest made out of fish eyes—well, more precisely, a bullet-proof vest made of a strong nanofibre constructed out of proteins derived from the lenses of fish eyes. As Gerrard found, fish eye lenses are an excellent source of protein. “Because they are almost pure protein. If you use waste material from an abattoir, you get a whole mixture of different substances from hair and bone—all sorts of tissues and all sorts of proteins. But eye lenses are pure protein, and nearly all one type of protein, so they are a perfect starting material.” The obvious bonus is that fish waste is as cheap as chips. The process by which the proteins from eye lenses are encouraged to unravel and then regroup as nanofibres is commercially sensitive, so Gerrard can’t divulge the fine details. “But basically we take a lot of fish lenses, put them in a blender in the right sort of buffer—water and a few secret ingredients—and then we leave them. So we’ve worked out the very simple conditions, the pH, temperature and so on, and we can persuade them to assemble into these nanostructures. And then we centrifuge them and harvest them, and you’re ready to go.” Now they just have to figure out how to produce them at a commercial scale. “We’ve figured out how to make grams of nanofibres, but we’re scaling that up now, working out how to manufacture kilograms. All the arrangements are in place with fishermen who are getting the lenses for us … they are happy to generate a new market in waste products. If we make something valuable, they can start selling the lenses at a higher price, so they’re keen to support those sorts of initiatives.” While she and her team are mainly focusing on nanofibres as the commercially viable product to come out of this research, they are also looking at adding value to the product, such as finding a way of using it to make fibre structures of spider-silk strength. They are collaborating with researchers who understand better the potential applications of these materials—including bulletproof vests. They are also investigating ways of using engineered proteins as a nanoscaffold for the immobilisation of certain enzymes. This would be a boon to the food industry, which depends upon enzymes to produce or improve the qualities of different food. As Gerrard explains, commercially produced enzymes are extremely expensive. “A lot of processing needs are solved by them, but if you are a manufacturer you just put the enzyme into your product and you have then used it up. If you immobilise that enzyme, you can cover beads in that enzyme, fish the beads out at the end, send your product away and put the beads in the next batch.” This could give food manufacturers more bang for their enzyme buck, and would also be more environmentally sustainable. “There are already lots of ways of immobilising enzymes, but the clever bit about our method is that it involves a huge surface area, so you would get lots more enzymes per bead.” Science is a long game, so there are other projects in the pipeline, such as using proteins to create responsive materials. Imagine a material that could heal itself. Imagine surgical operations involving an implant in which the surgeon could forget about the scalpel but instead inject a protein solution into a patient and persuade the proteins to assemble in the body in the place and shape that you wanted. This really could be the future. “That’s a long way from commercial reality, but learning to understand how those building blocks behave means we might be able to persuade them to form these structures in response to a trigger.” Asked if that’s going to be likely to come to pass in her research career, she laughs. “I’ve probably got 20 years left, so maybe just.”