Poly(L-glutamic acid) (PLGA) derivatives PTPALG and PTPOLG, which contain 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radicals linked to PLGA via amide and ester bonds, respectively, were synthesized by the dehydration-condensation reaction. The main chains of both PTPALG and PTPOLG were found to adopt the right-handed a-helical conformation, and accordingly, the terminal side-chain nitroxide radicals adopted the spiral configuration synchronized with the helical conformation of the main chain. Polarized microscopy observations reveal that PTPALG exhibited the lyotropic liquid, crystalline (LC) phase at greater than 7.5 wt % concentration in chlorinated solvents, whereas PTPOLG kept the anisotropic liquid phase at up to 10 wt % concentration. From the analysis of superconducting quantum interference device (SQUID) magnetometer and electron spin resonance (ESR) data, the magnetic properties of PTPALG and PTPOLG appeared to result from interchain spin spin interactions between nitroxide radicals rather than intrachain interactions. Interestingly, observation of the double quantum vertical bar Delta m(s)vertical bar = 2 line in a half-field region (g = 4.015) in the case of PTPALG revealed the doublet (S = 1/2) to triplet (S = 1) state conversion at around 6 K, exhibiting to be shifted the critical temperature in the sample evaporated the solvents from the LC phase. In contrast, PTPOLG retained its paramagnetic properties in the temperature range 4-200 K.