Page 222 - Neutrons for Sciences and Society

Neutrons for Science
In biology the record of the ILL is very favourable. The principal tool is so-called contrast variation. This method uses the vast difference in scattering powers of hydrogen and deuterium, and therefore between ordinary and heavy water. Small-angle neutron scattering which is only sensitive to the shape of the object can use a solvent mixture of light and heavy water and render invisible a molecule or part of molecule with the same scattering power.
In a compound consisting of a nucleic acid and a protein (which have different average scattering densities) one or other of the two components can be measured depending on the solvent mixture used. This has found many applications in enzymology and virology. Another area in which inelastic neutron scattering has provided useful information is in protein dynamics. An excellent review122 on this subject was published by G. Zaccai.
Most of these measurements would be impossible with other techniques, and difficult if not impossible to perform with beams from a medium flux reactor. Some of these applications arise in unexpected fields. For example Artioli123 and his colleagues have used neutrons to understand how an axe was forged in the Bronze Age. They studied the texture of the bronze axe using neutron diffraction, which has the advantage of being a non-destructive method for testing within a thick sample. The results found no texture, which showed that these ancestors were alternating cold working and prolonged annealing which removed the stresses induced by the cold working. This is an example of applying a technique widely used by engineers to a problem of interest to historians of technology.
122 Giuseppe Zaccai, “How soft is a protein? A Protein Dynamics Force Constant Measured by Neutron Scatter- ing”, Science, (2000), 288 p1604-1607, DOI 10.1126/science.288.5471.1604
123 Artioli et al., ILL Annual Report 2003, page 50.
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