The self-diffusion coefficients (D) and H-1 spin-spin relaxation times (T-2) of poly(gamma -oleyl L-glutamate)(POLLG) with long oleyl side chains and poly(gamma -n-octadecyl L-glutamate)(POLG) with n-alkyl side chains have been measured by the pulse field-gradient spin-echo H-1 nuclear magnetic resonance (NMR) method and the Carr-Purcell/Meiboom-Gill (CPMG) H-1 NMR method, respectively, over a wide range of temperatures from 30 to 80 degreesC, in order to elucidate the dynamic behavior of polypeptides in the thermotropic liquid crystalline state, which take the alpha -helical conformation. From these experiments, it was found that the diffusion coefficients of POLLG and POLG chains in the thermotropic liquid crystalline state at 60 degreesC are 9.97x10(-7) and 3.53x10(-7) cm(2)/s, respectively, and the former diffuses faster than the latter. The diffusion coefficients of POLG in the directions parallel (D-parallel to) and perpendicular (D-perpendicular to) to the alpha -helical chain axis were determined over a wide range of temperatures, and the D-parallel to value was found to be much larger than the D-perpendicular to value. Further, from the H-1 T-2 experiments, it was suggested that the mobility of the side chains relates closely to the diffusion process.