Science News

Scientists "unboil" eggs

Fri, 30th Jan 2015

Chris Smith

Scientists in the US and Australia have developed a technique that has enabled them to reverse the cooking effects of boiling an egg. Raw eggs

Writing in ChemBioChem, University of California, Irvine, scientist Greg Weiss and his colleagues took eggs that had been boiled for 90 minutes and successfully returned proteins in the egg white to their former "unboiled" state.

Proteins are natural polymers and are formed by linking together building blocks called amino acids, which differ in their shapes, sizes and chemical compositions. This has the effect of causing the protein to fold up, like origami, into a very specific shape suited to its purpose.

But cooking, and exposure to harsh chemical environments, can cause the amino acids to rearrange themselves, adding the equivalent of extra folds in the origami model.This distorts the protein, totally changing its characteristics, which is why cooking eggs turns the white rubbery.

To see whether this could be reversed, the Irvine team extracted samples of this denatured protein and first mixed it with a strong solution of the chemical urea and then placed the samples into tiny tubes a fraction of a millimetre across.

These were spun in a centrifuge at an angle of about 45 degrees to apply a shear force along the protein. This treatment had the effect of gently pulling apart the misfolded, denatured egg protein, rather like flattening out an origami model into the starting sheet of paper again.

They then resuspended the protein in a salt solution and found that it refolded itself back into its original, healthy shape.

The findings are important because proteins are frequently used therapeutically, as in the case of insulin used to treat diabetics, but they are frequently very costly to produce. This is because they are produced in specialised cell culture systems.

Trying to use cheaper, bulk forms of preparation, such as growing the proteins in bacteria, fails because the conditions inside the bacteria cause the proteins to misfold - like cooked egg white - forming insoluble tangles that have no therapeutic value.

Processing these aggregates to refold them is preclusively expensive and very time-consuming. But if it can be done using the cheap and very fast "egg unboiling" technique, costs and delays could be cut considerably.

It's early days yet though. Researchers have only tried the technique on some relatively simple proteins in their egg white, so scientists can't count their chickens yet!

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