07 January 2011
Analysing crystals "As costly as old cognac"
A new grant forces X-ray crystallographers to purchase a fluid as costly as cognac.By Jes Andersen
Anyone who really wants to study the atomic structure in a chemical compound needs to transform the compound into a crystal and irradiate it with X-rays. But in order for that little trick to work, the entire arrangement needs to be frozen. Even in a crystal the atoms will vibrate and that disturbs the signal. Previously the chemists at the Department of Chemistry have been able to cool crystals as far as minus 173 centigrade using liquid nitrogen. But that is far too toasty if you want to establish the electron density of the crystals as well. Now thanks to a 200.000 DKK grant from the Carlsberg foundation Anders Østergaard Madsen of the Biophysical Chemistry Group will be able to invest in new equipment cooled by helium. This will allow Madsen and his crystallofile colleagues to cool crystals to an icy minus 263 centigrade. But there's a catch. Liquid helium is not part of the grant. And that is unbelievably expensive says Madsen.
"By the litre helium costs about as much as cognac. And during just one experiment we use as much as 15 litres. So we're pouring a lot of cognac onto our crystals," smiles the crystallographer.
With his new cooling equipment Anders Østergaard Madsen will be able to examine crystals at ever increasing temperatures and he expects this to give him insight into how atoms in a structure start vibrating after having been cooled down. Madsen expects his heliumcooled equipment to be up and running sometime during spring.