Understanding of the structures of biomolecular complexes, their dynamics and roles at the molecular level requires knowledge of the physics and chemistry of the sunumits (proteins or lipids) involved and the interactions between them. This knowledge is emerging from methods of molecular crystallography, typically used for single protein structure determination with Å resolution and considered crucial for determining the structure-function relations of proteins. It is still, however, a challenge to produce a large number of crystalline samples needed for studying protein-protein and protein – lipid interactions. Kinetic and dynamic aspects of macromolecular assemblies and their dependence on solution conditions are unapproachable at the solid phase.
Solution X-ray scattering methods are non-invasive methods and do not require crystalline samples and thus offer unique advantages for studying protein-protein and protein – lipid interactions. The structural resolution, although lower than the crystallographic level, is sufficient for most investigations, where the focus is on the association of proteins and/or lipids to form higher order complexes, hence allowing a thorough investigation of the self-assembled structures under various solution conditions. This approach is particularly relevant for understanding the phase behavior of supramolecular and biological assemblies that are in aqueous environment and are controlled by various parameters. Of particular significance is the increasing capability of these methods to provide time-dependent structural information at the molecular level - a means for addressing dynamical aspects of molecular self-assembly. Apart from inherent scientific interest the knowledge gained in this research may ultimately lead to novel ways for rational design of drugs (antiviral drugs for example) or smart biomaterials for various applications, including drug delivery, controlled release, coatings and tissue engineering.