Proton nuclear magnetic resonance studies of myoglobin in H2O.

Exchangeable hydrogens in proteins can be identified by comparison of nuclear magnetic resonance spectra obtained in H(2)O and in D(2)O. In oxymyoglobin and myoglobin we have been able to observe resonances of the NH protons of the two tryptophans, as well as one resonance from arginine and one from histidine in the range -10 to -15 ppm downfield from 3-(trimethylsilyl)propanesulfonic acid (sodium salt). These resonances have been identified by chemical modifications coupled with considerations of crystallographic structure and the dependence of the resonances on the species (sperm whale, porpoise, horse) from which the myglobin was obtained and on spin, pH, and temperature.