Long‐Range Distance Measurements on Nucleic Acids in Cells by Pulsed EPR Spectroscopy

There-fore, it is important to investigate whether the in vitrodetermined NA structure reflects the intracellular (in vivo)conformation.BecauseofthehighsensitivityofEPRspectroscopy,itcanalso be applied to in vivo systems. In the past, nitroxide labelshave been used for in vivo EPR applications to determine theoxygen concentration, pH value, redox state, molecularmobility, and polarity of the local environment, and forspatial mapping of the free-radical metabolism.