Page 179 - Neutrons for Sciences and Society

comprising 21 proteins and one chain of RNA, the second 34 proteins and two fragments of RNA. Single crystals have been obtained of each of the sub-units, and even the complete ribosome. These single crystals can be used to obtain an electron density
map at high resolution. In order to best interpret these maps it is necessary to use knowledge of the topology of the sub-units. This topology is a structure at low resolution wherein each of the proteins is localised. This result was obtained with the help of neutrons (principally at Brookhaven). We know how to reconstruct these ribosomes in a test-tube from the components. If two proteins are replaced by their deuterated analogues, it is possible to determine the distance separating them due to the large difference in scattering powers of deuterium and normal hydrogen. Progressive replacement of different pairs of proteins allows triangulation of the proteins
in the ribosome. This is a good example of the complementarity between X-rays and neutrons.
With such needs for deuterated proteins, produced by growing bacteria in heavy water, the ILL in collaboration with the EMBL has established a deuteration unit. These collaborations between three partners, (ILL, EMBL, ESRF) have led to the construction of a joint laboratory, under construction as this is being written (2005). The Institute de Biologie Structurale (IBS) in Grenoble, a joint enterprise between the CNRS and CEA, is associated with this operation,
as is the virology laboratory of the University Joseph Fourier of Grenoble. [2018 addition: The Partnership for Structural Biology was launched in 2002, it is still active and hosted in the Carl-Ivar Brändén Building.]
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Chapter 7 - Maturity