Homopolypeptide Vesicles Triggered by Side-Chain Hydration

The formation of homopolypeptide vesicles and the identification of their self-assembly mechanism have been challenging issues in the field of polymer self-assembly. Using complementary circular dichroism(CD), Fourier transform infrared(FTIR) and low-field nuclear magnetic resonance(LF-NMR) spectroscopies, in this study we show that the higher hydrophilic ability of side-chains is a key factor for the formation of homopolypeptide vesicles from homo poly(Nε-carbobenzoxy-L-lysine)(PZlys), in which the vesicular structures are confirmed by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and atomic force microscopy(AFM) measurements. Poly(γ-benzyl-Lglutamate-co-Nε-carbobenzoxy-L-lysine) [P(BLG-co-Zlys)] containing different molar ratios of BLG to Zlys units with the same peptide backbone as PZlys are used as the controls. The copolypeptides can only form micelles under the same conditions, due to the more hydrophobic nature of their side-chains. These results show that the specific side-chain structure of the polypeptides plays a fundamental role in the self-assembly of homopolypeptides. These findings can be useful to understand how the hydrophilicity of the side chains of amino acid residues on the surface of a protein affects its structures.