Women in Science: Goo and the physics of the everyday stuff that surrounds us

Athene Donald
protein 300x225 Women in Science: Goo and the physics of the everyday stuff that surrounds us


Given recent press coverage, you might be forgiven for thinking that all physicists were interested in was the Higgs Boson. But our research fields extend much further than the ultra-small particles under study at Geneva in the Large Hadron Collider or, at the other extreme, the enormous distances of remote galaxies and stars studied by astrophysicists. Physicists study the behaviour and interactions of systems (including particles, stars and molecules) across the entire range of distances.  My own particular field of research is concerned with materials familiar to us from the everyday scale of our world; materials that are soft, as opposed to things like metals or diamonds, such as foods, ointments and creams, paint and the cells within our bodies. This world of soft matter physics – where the materials appear squidgy or gooey and can be readily squeezed, compressed or stretched by our own hands at speeds that are easily achievable – holds many fascinations.

At the heart of many of these materials are a class of molecules known as polymers, long chain molecules that can consist of millions of atoms in total. A polythene bag, for instance, consists of polythene (or more accurately polyethylene) molecules which are simply thousands or millions of repeats of a so-called monomer motif consisting of one carbon and two hydrogen atoms, where the carbon atoms are strung together to make a very long molecule rather like a string of beads.

In proteins the repeating monomer is much more complex, consisting of one of the 20 naturally occurring amino acid residues, but these are similarly strung together to make long molecules but with very specific sequencing. In polythene, the overall shape of the individual molecule is simply a random coil, but the functionality of a protein depends on it folding into a very specific shape, typically approximately globular. If this folding goes wrong, perhaps due to a genetic mutation or as a consequence of ageing, then function is lost and disease may result. Such diseases are often associated with the protein molecules sticking together in inappropriate ways that damage normal processes within the body. This is thought to be what underpins many of the catastrophic diseases of old age such as Alzheimer’s and Parkinson’s Diseases.

But as a physicist I can start to think about those proteins which have lost their native globular shape as simply being long chain molecules akin to synthetic ones such as polythene, where it is the stringiness that matters not the specific sequence of amino acid residues. Equally, one sort of unfolded protein now looks like any other one, where what matters is how neighbouring molecules come together to stick in clumps or crystals; ideas developed during the study of one, perhaps simpler, molecule can help to inform the study of another.  This is the approach I have been using to look at similarities between protein aggregation occurring after artificially-induced unfolding using heat to ‘denature’ the milk protein beta-lactoglobulin (a procedure used when milk is processed to make cheese or yogurt) and what may be happening in our brains as we age; the former may be able to give us clues about the latter.

What about the gooiness? Long chain molecules have other interesting properties when dissolved in a liquid such as water. Small molecules such as salt or sugar dissolve but don’t then physically interact at normal dilutions: the consistency of water or tea is very little altered by adding a few spoonfuls of sugar.

However, long molecules such as starch (which is simply a long chain molecule of repeating sugars) or gelatin (which is a denatured protein) when dissolved – typically heat may be required – can get tangled up together, like strands of spaghetti or skeins of wool. The resultant network of tangled chains means that the flow of the fluid is significantly modified and the viscosity is very different – the liquid has become gooey. This underpins the making of white sauce with cornstarch; the same effect is used to thicken water in shampoos or shower gels, although other polymers are then typically used. In the case of gelatin a further change happens, as will be familiar if you’ve made a jelly mould. After heating the gelatin to dissolve it, first the liquid thickens as it is cooled but ultimately the jelly ‘sets’. This again is due to the protein molecules clumping together into organised regions, knitting the tangled chains together into a more permanent network which can support its own weight – at least for a while.

Foods, shampoo and brain disease all come together in soft matter physics. It’s an exciting and rather young branch of physics which touches all our lives and opens up intriguing questions. Just because the materials are visible all around us, doesn’t mean the physics is mundane. I’ll be talking about some of these aspects of ‘goo’ and the underlying physics on my soapbox at Soapbox Science today at the South Bank.  This event is a wonderful occasion for us to share the excitement we each feel about our very different types of science, but also a time to celebrate women’s contributions. Don’t let the weather put you off!  I’m sure we’ll all have a great time exchanging ideas with anyone willing to stop by and listen and – I hope – inspiring some of the next generation.

Dame Professor Athene Donald is speaking at ZSL and L’Oréal-UNESCO’s Soapbox Science on  Southbank, 16 July 2012

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  • Insomnus

    Good luck with the speech.
    Ever since I discovered it was Rosalind Franklin who discovered the shape of DNA while Crick and Watson took the credit and peace prize I have been disgusted with masculine attitudes in science.
    Fortunately we are in a more enlightened era and it is people like yourself who encourage more women into science (and hopefully get the credit they deserve).
    Well done.

  • Flacksteen

    This is not quite true. Franklin’s work was an essential precursor of Crick and Watson’s discovery, but they saw what it meant, and she did not. Franklin’s real problem was her suspicion (possibly justified,but hard to live with nonetheless) of everyone else. She battled everyone in the Physics Department at King’s College, and then moved to Birkbeck College where she managed to repeat her performance, with the exception of Sage Bernal, who saw how good she was.

    She was a brilliant researcher, but she did not make the intellectual leap needed to see how DNA worked. Crick and Watson deserved their Nobel, which they shared with Wilkins, whose contribution was arguably smaller and more like Franklin’s.

    Watson was always the villain of the piece, as he unkindly and unnecessarily belittled Franklin for no good reason. If she had not died in 1958 she would probably have given Watson as good as she got.

  • ScaaarBeeek

    Athene — you KNOW you’re not as good as the guys.

    And you know Marie Curie was no Einstein.

    In fact, the idea of a naturally occurring radioactive metal was an idea of Pierre Curie’s. Marie was his assistant. Then he died, and she continued his work. Nowadays she’s given the credit for it.

    Back to Einstein though, his work took major leaps of imagination. From simultaneity being relative to curved space-times describing gravity: I mean seriously, how can a woman conceive of ideas like these?

    It’s now well known that men have a far superior visuo-spatial perception to women. And that this lasts the lifetime. Researchers in the universities of Vancouver, Stockholm and Barclelona have found conclusive evidence of this (and all of these researchers are women!).

    So let’s come off this one. Yes, there are female physicists, mathematicians and engineers who might be better than AVERAGE men. But they still cannot touch men in their same fields. Nor are they as numerous.

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