| Electron paramagnetic resonance (EPR) is an established and powerful tool for studying atomic-scale biomolecular structure and dynamics. Yet it requires a homogeneous sample size of approximately 1015 spin-labeled biomolecules. In contrast, single molecule measurements provide improved insights into heterogeneous behaviors that can be masked by ensemble measurements and are often essential for illuminating the molecular mechanisms behind the function of a biomolecule. In this dissertation, I report EPR measurements of a single labeled biomolecule demonstrating the merging of these two powerful techniques. We have selectively labeled individual double-stranded DNA molecules with nanodiamonds containing nitrogen-vacancy (NV) centers, and optically detected the paramagnetic resonance of the NV nanodiamond probe. Analysis of the spectrum reveals that the characteristic time scale for reorientation of the labeled molecule relative to the applied magnetic field is slow compared to the spin relaxation time of the nanodiamond probe. This demonstration of EPR spectroscopic determination of the dynamics of an individual labeled biomolecular construct provides the foundation for single molecule magnetic resonance studies of complex biomolecular systems.;In addition to this single-molecule EPR study, I report on the use of the NV center in diamond as a probe for in-vivo magnetometry, in-vivo fluorescence imaging and temperature sensing, and a tool for the measure of spin resonances in neighboring systems. The NV center in diamond has proven to be powerful tool for sensing and imaging in various systems, with a broad array of undeveloped or underdeveloped applications. The studies included in this dissertation provide a brief overview of a select few experiments that explore these capabilities. |
