Soft matter and Biology

Neutron beams are particularly well suited for soft matter and biology research. They can be generated with energies and wavelengths appropriate for probing a range of structures, from small molecules such as lipids or peptides, to larger molecules and molecular assemblies including viruses. Being electrically neutral, neutrons can travel deep into materials and are non-destructive.

The expression "soft matter" was first used by 1991 Nobel prize in Physics Pierre-Gilles de Gennes to define “molecular systems giving a strong response to a very weak command signal”. The field is very broad involving polymers, proteins, colloids, lipids, liquid crystals and any systems easily deformed by small external fields, including thermal stresses and thermal fluctuations. The relevant energy scale (comparable to room temperature, ~KBT) and the structures size (in the range of nanometers to a few micrometers) make neutron scattering ideal to study these systems.

One of the great advantanges of neutrons is that, in contrast with X-rays, they interact quite strongly with light elements, in particular hydrogen. Soft matter and biological systems are rich in light elements, and determining the precise location and orientation of the hydrogen atoms in a molecule is usually crucial to understanding its biological behaviour. In addition, such systems can be deuterated (i.e. hydrogen can be replaced by its isotope deuterium) to improve contrants and the quality of information that neutrons can provide.

At the ILL the structure of soft matter abd biological systems is probed by large-scale structures instruments, namely small-angle scattering instruments, reflectometers, small-angle diffractometers, while their dynamics is studied by neutron scattering spectroscopy with motions probed from the fs time scale (eV) to ~100ns (neV), using inelastic scattering, backscattering, and spin-echo instruments. Soft matter and Biology represents about 1/3 of the ILL output in terms of beam-time use and publications, and benefits from a vibrant scientific environment and facilities available through the Biology, Deuteration, Chemistry and Soft Matter Group and the EPN campus partnernships  Partnership for Soft Condensed Matter and Partnership for strucutral Biology.