Panel a, two-pulse ESE field sweep spectra of myosin·Mn·AMPPNP (trace 1) and Mn·AMPPNP (trace 2). Panel b, central part of two-pulse ESE field sweep spectra of myosin·Mn·AMPPNP (trace 1) and MSL·myosin·Mn·AMPPNP (trace 2). Experimental conditions: νmw = 30.108 GHz; mw pulses, 10 and 15 ns; time interval between the mw pulses, τ = 200 ns; boxcar integration gate, 15 ns; temperature, 15 K. The resonance positions of the pumping (νpmp) and observation (νobs) mw frequencies as used in pulsed ELDOR experiments are indicated.