Title
POSS semitelechelic Aβ17–19 peptide initiated helical polypeptides and their structural diversity in aqueous medium
Author
Ujjal Haldar, Abhishek Pan, Ishita Mukherjee, Priyadarsi De
Year
2016
Journal
Polymer Chemistry
Abstract
Biomolecule promoted helical polypeptides and their structural diversity towards external/internal stimuli is an interesting research area to the material science community. In this report, we have synthesized sequence registered peptide–polypeptide conjugates via ring opening polymerization (ROP) of γ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) employing two amine terminated peptide initiators, namely H-Phe-Val-Leu-POSS (POSS: polyhedral oligomeric silsesquioxane; Leu: leucine; Val: valine; Phe: phenylalanine) and H-Phe-Val-Leu-OMe. Main chain POSS semitelechelic or POSS free tripeptide containing poly(γ-benzyl-L-glutamate) (PBLG) homopolymers adopted α-helical conformation in both solution and the solid state, because of intramolecular hydrogen bonding and π–π aromatic interactions between side chain phenyl groups. POSS/OMe tripeptide conjugated PBLG segments self-assembled into hierarchical ordered helical entangled nanofibres, revealed by tapping mode atomic force microscopy (AFM) and field emission-scanning electron microscopy (FE-SEM). Expulsion of side chain benzyl groups (crucial for π–π aromatic interaction and stabilizing groups for the secondary structure scaffold) produced pH-sensitive amphiphilic anionic homopolymers, which exhibited diverse self-assembled nanoparticles in aqueous medium at pH 8.0. Interestingly, a morphological switch from sphere to square shaped micelles could be achieved simply by adjusting the net fraction of POSS moiety and/or the length of the benzyl deprotected segment.
Instrument
J-815
Keywords
Circular dichroism, Secondary structure, Polymers, Biochemistry