Volume profile of biochemically responsive interfaces

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Some proteins undergo major conformational changes upon ligand binding, such as calmodulin. This functionality shall be transferred to interfacial structures in this proposed project. Aqueous-solid interfaces are modified by multilayers or brushes of polyelectrolytes incorporating calmodulin or by covalent bonding of calmodulin mutants to the solid phase. In this way, novel biochemically responsive interfacial structures are formed, in contrast to well-known pH or temperature sensitive interfacial architectures. Such interfaces are relevant for many applications, where, for example, the immobilization of enzymes, the cell growth or the release of drugs needs to be regulated. Main goals of the proposed project are the controlled build-up of such interfacial layers and the characterization of the calmodulin functionality in these layers. Pressure is used as key variable to determine the volume changes associated with the build-up of the interfacial layers, the adsorption of protein and the ligand binding to calmodulin. Furthermore, the functionality of the biochemically responsive interfaces is investigated as a function of pressure, because pressure allows for tuning intermolecular interactions between protein and polyelectrolyte and modulating the packing density of the interfacial layers. The achievements and the methods used in the first funding period, where pressure effects on enzyme reactions in similar systems have been investigated, will be a helpful basis for the new proposed experiments. High-pressure surface-sensitive analytical tools will be applied, and similar interfacial modifications are prepared, complemented by covalent binding of calmodulin mutants. Moreover, surface modifications, which are biocompatible for enzyme reactions, have been identified in the first round of experiments. The results of this new project will describe the build-up, the thermodynamic and dynamic properties as well as the biochemical functionality of calmodulin-modified interfacial structures in detail, which is important for the understanding of these systems and their biotechnological and biomedical applications.