Applications of Small Angle Neutron Scattering to Biological Systems

Abstract

The physics of neutron scattering experiments in biology has to be simple because the biochemistry and molecular biology involved are usually very difficult. A first aim of structural studies in biology could be called anatomy at the molecular level; it is to provide an image, always a necessary but seldom a sufficient step in understanding a biological system. Then, one should relate that image or structure to the physico-chemical properties of the system. The most ambitious aim is to relate the structure to biological function in a one-to-one correspondance. The chemical components of living material are relatively few and well-known. The central theme in molecular biology is the “structure-function” relationship, which states, essentially, that the diversity of biological function has its roots in the way the same few chemical components are put together in different molecular assemblies. When one talks of a protein, for example, one means a molecule of a certain chemical composition (a polymer of aminoacid residues), which performs a given biological function. There are two parts to that definition: the first tells us that all proteins are similar since they have similar compositions, and the second tells us that each protein is rather special, since it has a given specific biological function.