Molecular dynamics and magic angle spinning NMR

Deuterium NMR line shape experiments and molecular dynamics simulations help evaluate the influence of temperature on the rate of 3-fold hopping of the ammonium group in L-alanine. Theoretical studies and use of two techniques, continuous wave proton decoupling and multiple phase homonuclear decoupling, confirm that a decoupling field-induced coherent spin motion interferes with the incoherent hoping of the protons of the ammonium group. When the rate of 3-fold hopping is similar to the cycle time of the multiple pulse trains or the reciprocal of the decoupling field, the interference induces significant broadening of NMR lines.