Distance measurements in the nanometer range by pulse EPR.

Distances of 1.5 to 8 nm in macromolecules and supramolecular assemblies can be measured by pulse electron paramagnetic resonance (EPR) experiments. In conjunction with site-directed spin labeling or the use of paramagnetic tracers this opens up a new method for the structure determination of complex systems such as biomacromolecules or nanostructured polymer materials. The extent of information obtained from such measurements crucially depends on the proper choice of the pulse sequence, on optimization of temperature, concentration, and matrix and on the procedure used for data analysis.