ABSTRACT: An administrative supplement is requested to purchase Bruker E500 CW Electron Paramagnetic Resonance (EPR) spectrometer to support P20 GM104316: Discovery of Chemical Probes and Therapeutic Leads. The goal of this COBRE is to continue our efforts to develop molecular approaches for probing biology, to discover and apply new chemical biology tools for the study of biological pathways associated with disease, and to develop computational approaches for understanding small molecule interactions with complex macromolecular targets. The goal of this administrative supplement is to request funds for the upgrade of a Bruker E500 CW Electron Paramagnetic Resonance (EPR) spectrometer with both X-band and Q-band capabilities. The upgrade will support purchase of a Microwave Bridge Controller, Digital Ultra High Resolution Hall Field Controller, and Dual Channel Signal Processing Unit (SPU) and a SuperX selected ultra low noise CW X-band microwave bridge. The spectrometer will interface with our existing magnet, Q-band bridge and our existing He VT-unit. The upgrade will replace an old EMX-EPR instrument that has been non- functional for more than 10 years. Currently, there is no functioning EPR instrument on the UD campus. The availability of EPR will support current COBRE researchers and will be important for the recruitment of new faculty to the UD campus in COBRE-related research areas.