Light, X-rays and Protein Structure

My husband talks about light and perception a lot, and gets very excited whenever a James Turrell piece is on show. Not surprisingly, therefore, another of the shows that I visited last week was ‘Light Show’ at the Hayward Gallery.

You might have noticed, light is not something I am concerned with in my work; I like things (objects, ideas, concepts) to be solid and tangible. I carry out some microscopy in the lab, but it is the solid, photographed image that excites me, not the differential absorbance of light by the specimen. I’m more likely to speak about light fittings (e.g. Cerith Wyn Evans’ columns of ‘S=U=P=E=R=S=T=R=U=C=T=U=R=E’ (2010)) than the light itself. Randomness, chance, waiting, and artworks that change over time (including performance art) make me feel uncomfortable; allow me to take a photograph or make a drawing, to solidify a moment in time, and I’ll find it much easier to cope. I spent time with some of Anthony McCall’s ‘Vertical Works’ a couple of years ago at the Ambika P3 exhibition space at the University of Westminster, and so ‘You and I, Horizontal’ (2005) was a good starting point for me.

Anthony McCall’s works are ‘solid-light’ installations that directly involve the viewer. He uses a video projector and haze machine to create large moving sculptures of light that can be walked around, into and through. The artificial mist created by the haze machine makes the light appear as though it is tangible: the smell of the mist evokes a chalky, powdery substance like talcum powder. So strong was the sense that the light was something that could be touched and felt that upon actually putting my hand into the path of the light and feeling no difference to the darkness before, I experienced a surreal sense of loss for a sensation that was promised but wasn’t received.

I wasn’t expecting to see work directly inspired by science in this exhibition. Conrad Shawcross’ ‘Slow Arc Inside a Cube IV‘ (2009), at first sight, presents itself as a metal cage containing a small halogen lamp at the end of a robotic arm, moving in a narrow ellipse. The cage is positioned in the centre of a small room and is patterned with stacked cubes –

Cubes

– so that when the moving light is projected through the cage, the perspective in the room shifts, challenging one’s perception of the space. This was the first piece in the exhibition that skewed my sense of reality such that I left feeling my exit with my hand on the wall.

It wasn’t until afterwards that I read the description in the gallery guide. It seems that Shawcross describes ‘Slow Arc inside a Cube IV’ as a “metaphor for the discipline of science”. The guide goes on to state that the work “owes its genesis to an anecdote about the immensely complicated process of mapping the molecular structure of insulin by means of crystal radiography” (X-ray crystallography). He cites Dorothy Hodgkin, who won the Nobel Prize in Chemistry in 1964 for her work in determining the structures of important biochemical substances, including insulin and vitamin B12, as his main influence for this work.

X-ray crystallography is a technique used to determine the structure of all manner of substances; all that is required is for the substance to form a crystal. (Crystallographers will scoff at my use of ‘all that is required’ since they can spend many years trying to determine the correct conditions for making a substance crystallise.) X-rays are fired at the crystal, and it is the unique diffraction pattern of the X-rays rebounding off of the crystal that provides the information about the substance’s structure. Hodgkin is said to have likened the process to “decoding the shape of a tree from the shadows cast by its leaves”.

The diffraction pattern produced by firing X-rays at the main protease (protein that chops up other proteins) of the Severe Acute Respiratory Syndrome (SARS) Coronavirus (3CLpro)

I then (perhaps wrongfully) assumed that the installation is a direct interpretation of the the process of crystallography. I felt that whereas Shawcross places a moving light source at the centre of his installation, seemingly inside the rudimentary crystal, it would have been more fitting to have a multi-faceted, crystalline object at the centre with the light moving around it. Shawcross’ shadows alter the perspective of the room, but the shadows themselves do not alter or merge, which could have produced a more revealing interplay of light and shadow.

I was encouraged to read further about Conrad Shawcross and his work, and it seems that he talks a lot about “relinquishing control and the unattainability of knowledge“. Whereas I was so quick to dismiss the notion that ‘Slow Arc inside a Cube IV’ is a metaphor for the discipline of science as being a rather huge statement, it seems that he does speak about an earlier version of this installation, ‘Slow Arc Inside a Cube II’ (2008), in this regard:

It’s a metaphor for the discipline of science because we’re always trying to see around that corner. We’ve got such limited information as to what’s really there – we’ll never fully grasp it… I suppose it’s also kind of similar to our condition in the universe, as we are looking from inside the self, outward towards the edges of space. So we’re seeing space from within itself, rather than from an objective point of view.

I think that this is quite an interesting observation, and an important concept to bear in mind when carrying out scientific research.

With regards to X-ray crystallography, when I was carrying out a bit of research for this post I came across some photographs of the first models made to describe some solved biochemical structures. They were made by the scientists themselves and are wonderfully creative in terms of the materials used. All are on display at the Science Museum in London, which is currently hosting an exhibition celebrating 100 years of X-ray crystallography, ‘Hidden Structures’. Unfortunately, I was not aware of the exhibition when I was in London last week, but am delighted to see that it runs until January 2014.

John Kendrew was awarded the Nobel Prize in Chemistry in 1962 along with Max Perutz (the same year as Watson, Crick and Wilkins won theirs in Physiology or Medicine for the structure of DNA). Kendrew solved the structure of myoglobin, the protein which stores oxygen in muscle cells. His model of myoglobin, made in 1957 and reported to be the first ever model to be made of a protein molecule, was constructed in plasticine and is supported by wooden rods protruding from a pegboard base.

This model was made by Dorothy Hodgkin in 1967 to describe the structure of the hormone insulin from pigs. The larger metal balls in this model represent zinc, which was chemically introduced into the protein in order to understand the rest of the structure. Lastly, but by no means least, this is Hodgkin’s model of the antibiotic penicillin (1945), with a background drawing likely denoting the compound’s electron density.

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Featured image: the diffraction pattern produced by firing X-rays at a crystal of lysozyme from hen eggs. Lysozyme is a protein also found in human secretions, including tears, milk, saliva and mucus. It attacks a substance found in bacterial cell walls causing their destruction, in this way performing an antibacterial, defensive action.

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