Tuesday, 15 February 2011

Sunlight and Synchrotrons

The snow has started to melt. The temperature is beginning to rise above freezing in Philadelphia for the first time in weeks. Leaves are starting to shoot and the grass is turning from rust-brown back to green. The organic geochemistry of life is re-booting for Spring. Sunlight is doing its job on these new shoots, fuelling the photosynthetic pathways that convert carbon dioxide into carbs...sunlight is a powerful source for the essence of life, energy.

Palaeontology has also started using light, in ways that I would never have guessed early in my career. We too are relying upon an interaction with light, but not with sunlight and plant chlorophyl, but with the surface of beautifully preserved fossils and more invisible parts of the electromagnetic spectrum.

Todays blog I thought I might bring-up the subject of a more familier part of the electromagnetic spectrum to many of us, X-rays. For many, their first interaction with X-rays is not a pleasant memory...as hospitals tend to come to mind, along with broken limbs! However, since September 2007 I have been getting used to another, more intense source of X-rays...those generated by synchrotron radiation. The synchrotron at which my group and I work is based at Stanford University (California) and is called the SLAC National Accelerator Laboratory.
SLAC from the air
You may recall in an earlier blog I was working crazy hours (20+ days) along with the rest of the Manchester team, basting fossils with X-rays...this was at SLAC. Here synchrotron light (in our case X-rays) are generated when electrons traveling near the speed of light take a curved path around a storage ring (above left red ring on aerial shot of SLAC). The particles blasting around the storage ring emit electromagnetic light in X-ray through infrared wavelengths. The resulting light beam has characteristics that make it ideal for revealing the intricate architecture and composition of many kinds of matter—in our case fossils!
See Bergmann et al 2010 in PNAS for more gorgeous images!
The elemental composition of fossils and the matrix in which they sit can be spatially resolved to ridiculous levels of accuracy here at SLAC. Our team works closely with Dr Uwe Bergman (no less than Deputy Director of the SLAC facility) who helps our team recover these delicate chemical fossils from past eons. Lest we not forget, we are a bag of chemistry...at SLAC, we can start to unpick the remnants of this chemistry that has survived through the sands (muds and limestones) of time.
Synchrotron sheds light on 150 million year old feather biomolecules!
Fortunately for palaeontology (and also the oil industry) the organic building blocks of life can sometimes be stubborn. They do not like breaking down. One such major group of molecules that form the backbone of many organic molecules, goes by the name of functional groups.These groups of atoms are responsible for much of the reactivity of a given molecule as it plays its part in the processes of life. It is these potential 'biomarkers' from deep time that we are so interested in hunting down and mapping in fossils. In my next blog we will take closer look at these chemical flight-recorders...with both x-rays and infrared light. To do this, we will enter the inorganic and organic world of my good colleagues Dr Roy Wogelius and Dr Bart van Dongen from the University of Manchester.

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