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

Abstract

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