This application is submitted in accordance with PA-02-057, Fogarty International Research Collaboration Award (FIRCA).The research will be done primarily in Poland, at the Jagiellonian University in Krakow in collaboration with Prof. Wojciech Froncisz, PhD, DSc, who is the Foreign Collaborator. It is an extension of NIH grant R01 EB001417, which is the Parent Grant. This proposal is device-design driven. The goal of the proposed work is to improve sensitivity in electron paramagnetic resonance (EPR) spectroscopy of aqueous fluid-phase samples. The proposal is timely because of recent advances in software for finite-element modeling of electromagnetic fields, computers with greatly improved computing speeds, and computer- controlled electric discharge machining (EDM). Computer-aided design will be used for resonators, sample cells and field modulation coils, followed by experimental evaluation. There are three Specific Aims, each of which involves the construction and evaluation in Poland of a sample-containing microwave resonator for EPR spectroscopy: (1) Loop-Gap Resonators (LGR) for Aqueous Samples. An LGR will be developed with ultra-high efficiency. (2) Uniform Field Cavity Resonators for Aqueous Samples. A Q-band uniform field cavity resonator will be developed for use with a novel sample-cell geometry and (3) Aqueous Sample Cell Clusters. A new Multipurpose cavity will be developed for use with layered flat cells. A theme of all three designs is use of EDM graphite, which has recently been proposed by us for EPR resonator construction. The P.I. serves as Director of The National Biomedical EPR Center, P41 EB00198Q, which is a Research Resource. Resonators developed under this FIRCA proposal will enhance the large number of Collaborative and Service Research projects carried out at the Resource. EPR spectroscopy is an important modality in biomedical research. Studies of short-lived radicals detected by spin trapping, of molecular structure using site-directed spin labeling, of biological or model membranes using spin probes, and of cell or tissue preparations are usually carried out in an aqueous environment. Work proposed here will improve the quality of data obtained in these experiments. [unreadable] [unreadable] [unreadable]