We report on a DNA-based model system for studying weak dipole-dipole and exchange interactions between a paramagnetic metal ion and a stable radical. The goal is to use the information gained from studying the electron spin-spin interactions in this model system to measure distances and electronic couplings in large protein complexes. Molecular modeling studies, spectroscopic measurements of the thermodynamic stability of the DNA duplex, and electron paramagnetic resonance (EPR) measurements of the spin-label dynamics are used to generate a picture of the model system's structure when dysprosium (III) is the paramagnetic metal ion. Electron spin-spin interactions are observed by both continuous wave and pulsed EPR over distances as large as 5 nm. Pulsed EPR experiments suggest that the exchange interaction makes a significant contribution to the spin-lattice relaxation of the spin-label at low temperatures (T < 77 K).