EPR Imaging in Biological Applications: Towards Microtomography

摘要

EPR imaging and microtomography promises to be a powerful tool for the EPR spectroscopist, but the expansion of this technique was hindered by the lack of commercial apparatus. A simple modification of an existing commercial system that can reach a resolution of the order of 75 μm with a gradient of 150 mT m~(-1) is described. This resolution can be increased by using larger field gradients. In many biological applications this resolution is significant. As an example, the distribution of a paramagnetic probe in an amphibious egg cell is presented that permits one to distinguish the nucleus of the cell. A summary of the mathematical techniques which enable one to account for the presence of a hyperfine structure in most EPR paramagnetic probes and to increase resolution is also presented.