Molecular interactions are of key importance to many chemical and biological processes such as protein folding and function, peptide aggregation, enzymatic reactions, or the stabilization of reactive species, to name but a few. Intermolecular interactions between solvent (water in most cases of biological relevance) and solute molecules determine the aggregation of proteins into fibrils, enzyme catalysis, and other biological processes. In our group we use state of the art computational tools and the construction of new models of complex systems to investigate molecular interactions of proteins, organic molecules, solvents, co-solvents and lipid bilayers. The focus of our research is to explore the properties, reactivity, and applications of complex systems consisting of a large number of interacting molecules.