This proposal seeks to gain insight into interactions between protein beta-sheets, with the broad long-term objective of developing new compounds that can control this important, but underappreciated, class of protein-protein interactions. Interactions between protein beta-sheets occur widely and are represented significantly in about 15% of the protein structures in the Protein Data Bank (PDB). Protein beta-sheet interactions play a critical role in many biological processes associated with normal healthy function and in diseases ranging from cancer and AIDS to anthrax and Alzheimer's disease. [unreadable] [unreadable] The investigators will gain insight into interactions between protein beta-sheets by developing and studying chemical models of beta-sheets that bind proteins by means of beta-sheet interactions. These chemical models will be cyclic compounds containing a new amino acid building block that the investigators invented (Hao) and a new turn unit that the investigators discovered (delta-linked ornithine). The investigators will study the binding of cyclic chemical models of the CH1 domain of Fab to protein G domain III, to gain insight into interactions between protein beta-sheets and to determine what is necessary to create relatively simple chemical compounds that participate in the same types of beta-sheet interactions as much larger proteins. The investigators will use these systems and the insights gained from these studies to develop compounds that block the aggregation of beta-amyloid and Huntington, which are associated with Alzheimer's and Huntington's diseases. [unreadable] [unreadable] By developing synthetic compounds that bind to a real protein domain and bind proteins associated with important neurodegenerative diseases, these studies will further the long-term objective of creating compounds that can control interactions between protein beta-sheets. These insights and new compounds may eventually pave the way to new drugs to treat diseases and improve human health. [unreadable] [unreadable]