Control of Peptide Secondary Structure and Dynamics in Poly(γ-benzyl-l-glutamate)-b-polyalanine Peptides

The stability, persistence and dynamics of the peptide secondary motifs are investigated in a series of poly(γ-benzyl- l -glutamate)- b -polyalanine (PBLG- b -PAla) polypeptides through a combination of structural (X-rays, NMR) and dynamic (Dielectric Spectroscopy, NMR) probes. The unfavorable enthalpic interactions between the unlike blocks give rise to nanophase separation that results in the destabilization of PAla β-sheets. Contrary to this, the overall helicity of PBLG α-helices is enhanced. The dynamics of the “defected” amorphous segments and of the more ordered segments are studied by DS and 13 C NMR, respectively. These probes provide information on the time scale and the mechanism of molecular and supramolecular motion.