Polypeptide derivatives and nucleic acid carriers containing the same

A peptide derivative represented by formula (1):

• 13
• wherein R1 is derived from one member selected from the group consisting of a monosaccharide, an oligosaccharide, a polysaccharide, a peptide, an oligopeptide, a polypeptide, an antibody and a cell-specific ligand, or is selected from the group consisting of an optionally substituted C1-C20 alkyl, an optionally substituted C1-C20 alkenyl, an optionally substituted C7-C45 aryl, an optionally substituted C7-C45 alkylaryl, an optionally substituted C7-C45 alkenylaryl, and an optionally substituted amino group wherein the substituent may be a moiety of the one member selected from the group consisting of a monosaccharide, an oligosaccharide, a polysaccharide, a peptide, an oligopeptide, a polypeptide, an antibody and a cell-specific ligand;
• “p” represents an integer of 1-5;
• “m” represents an integer of 2 or more;
• and “n” represents an integer of 2 or more, provided that “m+n” represents an integer of 300 or less,
• or a pharmaceutically acceptable salt thereof.