As chemist and molecular gastronomy giant Hervé This discovered some years ago, it is, indeed, possible to unboil an egg.
When you put an egg in boiling water, the heat breaks the bonds that hold together the protein's amino acid strings. As the heat rises, these strings then form new, stronger bonds, forcing out the water and hardening the contents of the egg; though, because of differing fat content, the process takes slightly longer for the yolk than the albumen.
As This discovered, these proteins can once again become detached with the addition of a substance like sodium borohydride; applying it to the egg will cause it to reliquefy over the course of about three hours. Though interesting, this serves no practical purpose.
However, a new way to "unboil" a key protein in egg whites, discovered by researchers at the University of California, Irvine, and Flinders University in South Australia, could drastically reduce the costs of biotechnology.
"Yes, we have invented a way to unboil a hen egg," said Gregory Weiss, UCI professor of chemistry and molecular biology & biochemistry. "In our paper, we describe a device for pulling apart tangled proteins and allowing them to refold. We start with egg whites boiled for 20 minutes at 90 degrees Celsius and return a key protein in the egg to working order."
By "working order", he means molecular proteins that can be used for a wide variety of applications in chemistry and molecular biology. These proteins often "misfold" into unusable shapes when formed, rendering them useless; whereas the team's technique could recycle or create usable proteins quickly and easily.
"It's not so much that we're interested in processing the eggs; that's just demonstrating how powerful this process is," Professor Weiss said. "The real problem is there are lots of cases of gummy proteins that you spend way too much time scraping off your test tubes, and you want some means of recovering that material."
The technique -- which takes a matter of minutes, compared with about four days for dialysis, the current method of restoring denatured proteins -- involves adding urea to the albumen to restore a protein called lysozyme. The urea "chews" the proteins, liquefying the solid whites. However, this is only half the battle; at the molecular level the protein is still in unusable balls.
This is where Professor Colin Raston of Flinders University comes in -- and where the technique makes a pretty radical departure from that of This. The egg whites are then spun in a high-speed vortex fluid device designed by Professor Raston's laboratory. This process causes shear stress, which forces the amino acids back into their untangled form.
"The sodium borohydride approach (and likely Vitamin C) dissolves the proteins but changes their bonding patterns. So, the proteins no longer have the natural functions," Professor Weiss explained. "For example, lysozyme is an antibiotic protein charged with chewing up the cell walls of any bacteria that make it past the egg shell. After treatment, as Hervé This shows, lysozyme would be unlikely to return to normal."
The urea technique -- for which a patent has been filed -- would allow, for example, cancer antibodies to be manufactured much more cheaply. The current method involves using expensive hamster ovaries, which have a low rate of protein denaturing. The ability to make proteins quickly and cheaply from yeast or E.coli bacteria, for instance, could make cancer treatments much more affordable.
The full paper, "Shear-Stress-Mediated Refolding of Proteins from Aggregates and Inclusion Bodies", can be found online in the journal ChemBioChem.