Antioxidant Activity of Linear and Star-shaped Poly(L-glutamic acid) Polypeptides Modified with Dopamine and Glutathione

Abstract

The aim of this study was to investigate the effects of topology and antioxidants on the antioxidant-grafted polypeptides The linear and star-shaped poly(L-glutamic acid) (PLG) polypeptides were synthesized by N-carboxyanhydrides (NCAs) ring opening polymerization (ROP) using primary amine and polyols as initiators followed by deprotection Graft copolypeptides (PLG-Dopa PLG-GSH and PLG-Dopa-GSH) were obtained by EDC/NHS coupling chemistry using dopamine (Dopa) and glutathione (GSH) Successful synthesis of these polypeptides was confirmed by 1H NMR MALDI TOF GPC UV-vis and IR spectra analyses The conformation of polypeptides was investigated by circular dichroism (CD) spectroscopy demonstrating the grafting of Dopa and GSH onto PLG was accompanied by a conformational change from a random coil to ?–helical structure The results showed that the antioxidant activities of PLG-Dopa and PLG-Dopa-GSH were ascribed to Dopa instead of GSH Our experimental data showed that multi-armed polypeptides exhibited better antioxidant activity than linear ones which could be attributed that they could form a dense structure with higher local antioxidant concentration It was found that both PLG-Dopa and PLG-Dopa-GSH exhibited low hemolysis suggesting good hemocompatibility These graft copolypeptides with a given concentration to inhibit 50% free radicals would not cause cytotoxicity

Date of Award	2020
Original language	English
Supervisor	Jeng-Shiung Jan (Supervisor)