Solid state dynamic properties have been investigated for the racemic (DL) and enantiomerically pure Q crystalline forms of the amino acid serine [HO center dot CH(2)center dot CH(NH3+)center dot CO2-] using H-2 NMR line shape analysis and H-2 NMR spin-lattice relaxation time measurements for samples of DL-serine and L-serine deuterated in the NH3+ and OH groups. 2 H NMR line shape analysis indicates that, for both L-serine and DL-serine, the ND3+ group undergoes a 3-site 120 degrees jump motion, with jump frequencies in the intermediate motion regime (10(3) s(-1) to 10(8) s(-1)) in the temperature range 153-313 K. However, at a given temperature, the jump frequency is substantially higher for L-serine (e.g., at 233 K, the jump frequency is 5.0 x 10(6) s(-1) for L-serine and 6.0 x 10(4) s(-1) for DL-serine). The OD group is not dynamic on the 1H NMR time scale within the temperature range studied. The results from both H-2 NMR line shape analysis (LA) and H-2 NMR spin-lattice relaxation time measurements (SLR) indicate that the activation energy for the 3-site 120 degrees jump motion of the ND3+ group is significantly higher for DL-serine [38.0 +/- 1.0 kJ mol(-1) (LA); 39.7 +/- 0.8 kJ mol(-1) (SLR)] than for L-serine [23.4 +/- 0.8 kJ mol(-1) (LA); 23.8 +/- 0.3 kJ mol(-1) (SLR)]. The difference in activation energies between DL-serine and L-serine is substantially greater than any reported previously for an amino acid in different crystal forms.