Recently,polypeptides have been extensively researched as gene/drug delivery system for its similar structure to natural proteins,good biocompatibility and low cytotoxicity.Herein,we synthesized total-polypeptide copolymers azobenzene-modified polysarcosine-b-polylysine (ASL) by a-amino acid N-carboxyanhydride polymerization (Fig.1) [1].Polylysine (PLL),a commonly used cationic polypeptide,was designed to bind DNA.Polysarcosine (PSAR) was used as PEG alternative to enhance in vivo circulation time for its outstanding hydrophilicity and protein resistance ability [2].