The existence of functional disordered (unstructured) proteins has been recognized for many years, and unstructured proteins were observed in intact cells in early proton NMR experiments. About 10% of all proteins are fully disordered and about 40% of eukaryotic proteins have at least one long disordered region. However, due to the classical structure-function paradigm, the functional role of intrinsically disordered proteins (IDP) has only recently been recognized. Biochemical evidence has since shown that these proteins are functional, and that the lack of a folded structure is related to their function. These proteins can also be found in saliva, where they play an important role in oral health, but also in milk products.
We would like to present results from a combined experimental and theoretical study, where the aim is to develop a model for flexible proteins and to relate the lack of structure of the proteins in solution with their function and structure when adsorbed to surfaces. For this purpose, we are combining atomistic and coarse-grained modelling, with simulation techniques such as molecular dynamics and Monte Carlo simulations. The bulk properties of proteins are studied by osmometry and DLS/SAXS, whereas surface adsorption properties are studied by ellipsometry. Statistical thermodynamics and polymer theory serves as a base for the model development.
As model proteins we are using one short cationic peptide (Histatin 5) and one longer anionic protein with amphiphilic character (beta-casein). Hence, thereby we are covering many different aspects of protein properties that can be found. For example, at physiological pH Histatin 5 is basic and has a positive charge, and due to its richness in histidins it has a high charge capacitance whereas beta-casein is a self-associating proline-rich phosphoprotein, with an amphiphilic character at neutral pH.
marie.skepo@teokem.lu.se
