Kinetic isotope effects for fast deuterium and proton exchange rates

By monitoring the effect of deuterium decoupling on the decay of transverse N-15 magnetization in D-N-15 spin pairs during multiple-refocusing echo sequences, we have determined fast D-D exchange rates k(D) and compared them with fast H-H exchange rates k(H) in tryptophan to determine the kinetic isotope effect as a function of pH and temperature.