A 2H NMR spin-lattice relaxation study of -NH+3 group dynamics in polycrystalline L-alanine

The 2H spin-lattice relaxation times T1Z and T1Q of the -ND+3 group in polycrystalline L-alanine were measured over the temperature ranges 250-425 K and 300-425, respectively. The relaxation data were fitted to analytical expressions for three-fold reorientation, giving a correlation time tau(c) = 1.5 x 10(-14) s exp(40.2 kJ mol-1/RT), which is in good agreement with the results of a limited lineshape study. T 1Z values derived from numerical simulations, taking into consideration geometrical distortion of the -ND+3 group and experimental imperfections, are compared with values given by an analytical expression for three-fold jumps and with the experimental results. The extraction of average site quadrupolar coupling constants is discussed.