How to unboil an egg
Eggs are a familiar symbol of Easter, both chocolate and boiled. Many people celebrate Easter Sunday with a boiled egg with a face on it. The familiar change that takes place when we boil an egg - the runny egg white goes rubbery and becomes opaque- occurs because heat causes the proteins that make up the egg white to change their shape - or denature. Now, University of California, Irvine, scientist Greg Weiss has found a way to reverse the process or "unboil" an egg. And this could be a very useful technique for mass-producing proteins that we need to study, or for medical use, as he explained to Chris Smith...
Kat - To start off, one of our producer Georgia's favourite Easter traditions is to draw happy faces on her soft-boiled eggs before ruthlessly decapitating them and dipping toast in their brains.
Chris - Yumyum! Now, the familiar change that takes place when we boil an egg - that runny white going rubbery and becoming white - it occurs because heat causes the proteins that make up the egg white to change their shape or do what we call denature. Now, University of California Irvine scientist Greg Weiss has found a way to reverse this process, or as he puts it, "unboil" an egg. This could be very useful for mass-producing proteins that we need to study, or for medical uses.
Greg - We didn't originally set out to unboil eggs. Originally, I just wanted some way of untangling proteins that get mashed together and folded up and agregated. So, I was in the lab one day and we had this new method of yanking on the protein chains and forcing them into their correct shapes. I realised that no one on the planet would believe how cool this was until I could demonstrate this on a problem that everyone acknowledges as hard. And then suddenly, I realised, that egg that I had for breakfast would be perfect.
Chris - First of all, tell us what is a protein and why is this important?
Greg - Proteins are the workhorses of your cells. They're the things that make you do the things you do, that raise your arms, that provide the muscles, that run around the body and do all kinds of things. Those proteins are absolutely fascinating little machines that scientists like myself want to study. So, when we start looking at them in detail and start examining their functions and how they work, oftentimes, we have to produce them in big quantities because only small quantities are available inside the cells. So, we produce a big batch of these things and start examining them in detail. But the problem is, when you're making these big batch of stuff, it's kind of like making a big batch of chocolate chip cookies or something. It doesn't come out the way the small batch did. They come out messed up, tangled together, just like egg whites after you boil them.
Chris - So, when I do boil my egg, the runny stuff, the white becomes white, doesn't it? So, what's actually happened to make a cooked egg go white like that?
Greg - The boiled egg, proteins inside the egg white are slipping apart. And so, instead of being like neatly folded up sheets, let's say, just sheets that you put on your bed, instead of being nicely folded, they get thrown around the room inside the eggshell. You get a big pile of them that are tangled together and that tangled mass appear white to us.
Chris - But the bottom line is that the proteins that were in the egg white when it was in the runny, uncooked state, and now, in a very different shape and state once we have boiled the egg.
Greg - Eggs-actly!
Chris - The pun didn't escape me there, Greg.
Greg - Sorry.
Chris - So, what has happened?
Greg - So, the proteins get tangled together and then that's what appears white to us. In that state though of tangled up, those proteins are useless. You know that because even if we fertilised the boiled egg, nothing would happen, right? When proteins are tangled up, they're not in their natural shapes and they can't do their natural functions. We needed a way of getting them out of that tangled up shape so that we can look at them in greater detail in laboratories like my own which focuses for example on cancer research.
Chris - So, how did you get the egg to unboil itself then?
Greg - We started with eggs that were purchased from the local grocery store, brought them home and then separated out the yolks from the whites - using of course, Julia Child's classic methods - boiled the egg for a good 10 to 20 minutes so a really long time. So, these were hardboiled eggs, like hard, hardboiled eggs. And then we took the hardboiled egg, dissolved it in a chemical called urea. So, urea is this fascinating chemical that gets into the protein tangles and starts breaking apart the little tiny contacts they have with each other. At that point, the proteins are still totally useless. They're like a tangled mass of sheets that have been thrown on the ground. We then put them in a special device called the vortex fluid device. The proteins are subject to tremendously high shear stress as they're whirled in a tiny mini centrifuge. In this shear stress, the proteins are pulled and unpulled like rubber bands. And then spontaneously, they start folding up into their correct shapes.
Chris - So, when you put them into the laboratory equivalent of a food mixer - that centrifuge essentially - you're putting them under a shear stress or you're pulling on the proteins and that makes them sort of untangle, unthread themselves from this bundle that you had before. And then they're given the opportunity to put themselves back to the shape they had before we boiled the eggs.
Greg - That's correct.
Chris - How do you know that the proteins do go back to their egg unboiled state?
Greg - Yes, good question. So, there are a very large number of proteins inside an egg white, but we examined the abilities of one protein that's a champion at chewing on any bacteria that happen to get pass the eggshell. Normally, after you boil eggs, this protein is totally messed up. But after our unboiling experiment, the protein returns to 80% or so of it normal activity. To demonstrate that, we basically fed it these bacteria cells and then watched it chewing on their cell walls.
Chris - Goodness! So that suggests that it would actually work for a whole range of different proteins in the egg but then also, potentially other tangled up denatured proteins in other circumstances in the laboratory for example.
Greg - Yes. That's precisely what we want to do, is to apply this now to proteins that are associated with cancer, proteins that we'd like to use as flags for cancer to develop better diagnostics, proteins that we want to study their structures and understand how mutations to these proteins drive cancer and drive tumour formation.
Chris - Does it work on chocolate eggs?
Greg - You're the very first person to ask. I'm tempted to go back to the lab right now, but that's only because I just want to purchase a large amount of Cadbury eggs and claim that it's a lab expense.
Chris - Sounds like a very fun experiment. Greg Weiss, unboiling eggs including possibly, chocolate ones. And on the subject of experimenting, over to Kat...