Facilities Home Tour Our Facilities X-Ray Crystallography Nuclear Magnetic Resonance Electron Paramagnetic Resonance Laser Spectroscopy Muscle Mechanics Basic Sciences Computing Laboratory Electron Paramagnetic Resonance Electron Paramagnetic Resonance is a powerful, versatile, nondestructive and nonintrusive analytical method. EPR can yield meaningful structural and dynamical information, even from ongoing chemical or physical processes without influencing the process itself. Conventional EPR can be used to measure orientation and rotational motions in the time range from picoseconds to nanoseconds, while saturation transfer EPR extends this to the microsecond time scale. Site-directed spin labeling (SDSL), in which Cys mutagenesis is used to place Cys-reactive spin labels at desired sites on a protein, can be used to determine protein secondary and tertiary structure, and to measure structural changes that are inaccessible to conventional structural techniques. Bruker Elexsys E 500 EPR X-band spectrometer.