Getting structures from data
To determine structures from increasingly complex systems is demanding computationally. The University of Copenhagen are developing tools to model complex macromolecules.
The LINX team at the University of Copenhagen (KU) uses small-angle X-ray and neutron scattering (SAXS and SANS). By recording how beams of X-rays or neutrons are scattered by materials, the LINX team can determine the nanoscale structure of many manmade and natural materials. The range of possible materials that can be studied is extremely broad and includes proteins of pharmaceutical relevance, artificial polymer materials like plastic, natural polymers (plant fibres, starch and cellulose), self-assembled systems membranes. The common property of all these systems is that they have structure on a length scale ranging from 1-1000 nm, which is precisely the range that can be studied under relevant conditions using small-angle scattering
Most materials of industrial relevance are organised over a range of length scales giving them hierarchical structure. The ramification of this is that there is a strong interplay between what happens at a local nanometre scale and the macroscopic behaviour of the bulk materials. Therefore, to fully understand the performance and properties of a material requires characterising the structures over all of these length scales.
Techniques and Methods
When studying a material with a hierarchical structure, it is not enough to know simply know the identity of the molecule(s) that a material is made of. The shape, internal organization, and collective behaviour play a crucial role for the materials’ properties and, therefore, must also be known. The small-angle scattering technique used by the LINX team at KU can obtain structural information over three orders of magnitude (from 1 to 1000 nm) and can do exactly that.
However, determining structure from small-angle scattering data is not a straightforward task. Unlike microscopy, it is not possible to obtain a simple picture of what your material looks like. Scattering data instead relies on software developed by various researchers around the world to fit models to experimental data. As part of their LINX activities, the LINX team at KU has advanced their software further so that it can be used to analyse more complex macromolecules, such as when different types are coupled to one another to form “hybrid” molecules. An example is when proteins are bound to carbohydrates. These kind of hybrid macromolecules are not just of academic concern; they are crucial components both in living organisms and in many pharmaceuticals.
Participants: University of Copenhagen.
Title: Software tools for small-angle scattering (KU GDP).