Abstract
Rotating frame relaxation experiments in proteins are used to study slow motions on the microsecond to millisecond timescale. An on/off resonance rotating frame relaxation experiment (R1ρ) has been developed that incorporates adiabatic rotations into a R1ρ–R1 constant relaxation time experiment with weak radio frequency field strengths in order to effectively lock the magnetization over a wide range of 15N frequencies. The new pulse sequence allows the measurement of a wide range of chemical exchange timescales on the order of 1.0 to 0.05 ms over an asymmetric bandwidth from +1.7ω1 to −0.5ω1 in a single experiment. A total bandwidth of ±1.7ω1 is obtained by performing the experiment a second time with a reversed adiabatic rotation.