Research in the project area D focuses on investigations of interactions of biomolecules, their non covalent bound complexes, as well as their structures. The investigation of non covalently bound complexes has advanced to a rapidly expanding interdisciplinary research field. This trend has been fueled by new and powerful developments in instrumental analytics (mass spectrometry, NMR, X-ray crystallography, etc.), as well as efficient (bio)chemical strategies and techniques for synthesis of biopolymers. The function of a biomolecule usually depends on its specific, non-covalent interactions with another molecule. For example, proteins interact with other proteins, peptides, small molecules, metal ions, lipids, polysaccarides, nucleic acids and oligonucleotides and these interactions drive critically important biological processes. The solvent water may also play a decisive role for the conformation and the function of biopolymers. The systems under investigation are often not commercially available such that efficient strategies and techniques for the synthesis of biopolymers have to be applied or developed within the framework of the graduate school. Several well established analytical techniques are used to study biomolecular interactions including circular dichroism, fluorescence, infrared and ultraviolet spectroscopy, nuclear magnetic resonance, mass spectrometry, and X-ray crystallography. Within the graduate school NMR, chromatography, UV- and CD-spectroscopy, and mass spectrometry are the key technologies for the investigation of macromolecular systems of biological relevance. The investigation and synthesis of specific non covalently bound complexes has several interesting aspects. First, the development of powerful analytical techniques is of interest to applied medicine and pharmacology for the development and optimization (screening) of drugs. Also the synthesis of new compounds having the potential of becoming new drugs with unknown features is very attractive and fuels the activities of both fundamental as well as applied research. The interplay of groups that synthesize systems and groups that analyze them is of crucial importance because powerful analytical techniques can screen families of biomolecules derived from one main structure via powerful combinatorial techniques and help to find potential candidates for new and improved drugs. Finally, the potential of the approach in the future will depend critically upon the understanding of specific interactions of biomolecules on a molecular level, which may be achieved employing powerful methods and approaches from theoretical chemistry and physics (e.g. MD calculations, molecular modeling). In the Project area D (Biomolecules and their aggregates) we strongly favor interdisciplinary work and complementary approaches for the synthesis and the investigation and analysis of biomolecular systems. In project area D currently six groups from the Max-Planck and University institutes (Abel, Buck, Diederichsen, Griesinger, Tietze, Zeeck) participate which offer a large number of interesting and interdisciplinary PhD-projects.