Effects of Nanometer Confinement on the Self-Assembly and Dynamics of Poly(γ-benzyl‑l‑glutamate) and Its Copolymer with Poly(isobutylene)

Poly­(γ-benzyl-l-glutamate) (PBLG) and its copolymer with poly­(isobutylene) (PIB) are studied in the bulk and under nanometer confinement in pores with emphasis on the self-assembly and dynamics, respectively, with X-ray diffraction, 13C NMR, dielectric spectroscopy, and differential scanning calorimetry. PBLG segments located within the α-helical and amorphous regions have distinct dielectric fingerprints. We have analyzed the dielectric signal from the segmental and α-helical segments to show that the α-helices are short and, furthermore, interrupted by amorphous segments. The effect of confinement is twofold: first, to speed up the segmental process and, second, to destabilize, in part, the secondary structure. The block copolymer architecture combined with confinement further destabilizes the α-helical secondary structure by introducing phase mixing. The results on the synthetic polypeptide demonstrate that both the chain configurations and the associated dynamic processes are affected when the PBLG chains are entering narrow pores. These results could pave the way for a better understanding of the behavior of more complex proteins in confined space.