Patent ID: 8853167

Claim:
A cationic polyamino acid capable of associating with a nucleic acid, the cationic polyamino acid comprising: 1 to 20 units of one or more cationic amino acid residue(s) having a cationic group in a side chain; and a plurality of hydrophobic amino acid residues having a hydrophobic group in a side chain, wherein the cationic polyamino acid has the following formula (1): where: R 1 is a hydroxyl group or an unsubstituted or substituted linear or branched alkyloxy group having 1 to 12 carbon atoms, an unsubstituted or substituted linear or branched alkenyloxy group having 2 to 12 carbon atoms, an unsubstituted or substituted linear or branched alkynyloxy group having 2 to 12 carbon atoms, or an unsubstituted or substituted linear or branched alkyl-substituted imino group having 1 to 12 carbon atoms; R 2 is a hydrogen atom, an unsubstituted or substituted linear or branched alkyl group having 1 to 12 carbon atoms, or an unsubstituted or substituted linear or branched alkylcarbonyl group having 1 to 24 carbon atoms; R 3a , R 3b , R 4a , and R 4b are each independently a methylene group or an ethylene group; R 5a and R 5b are each independently —O— or —NH—; R 6a and R 6b are each independently a saturated or unsaturated linear or branched aliphatic hydrocarbon group having 6 to 27 carbon atoms, an aromatic hydrocarbon group having 6 to 27 carbon atoms, or a sterol group derived from a sterol; R 7a and R 7b are each independently selected from the group consisting of: —NH—(CH 2 ) p1 —[NH—(CH 2 ) q1 —] r1 NH 2 (i); —NH—(CH 2 ) p2 —N[—(CH 2 ) q2 —NH 2 ] 2 (ii); —NH—(CH 2 ) p3 —N{[—(CH 2 ) q3 —NH 2 ][—(CH 2 ) q4 —NH—] r2 H} (iii); and —NH—(CH 2 ) p4 —N{—(CH 2 ) q5 —N[—(CH 2 ) q6 —NH 2 ] 2 } 2 (iv), where: p1 to p4, q1 to q6, and r1 and r2 are each independently an integer of 1 to 5; R 8 is a side chain of an amino acid selected from the group consisting of lysine, ornithine, arginine, homoarginine, and histidine; m is an integer of 5 to 80; n is an integer of 0 to m; x is an integer of 1 to 20; y is an integer of 0 to x; and z is an integer of 0 to 20, with the proviso that: 1≦x+z≦20, repeating units having the groups R 6a , R 6b , R 7a , and R 7b and R 8 may be bound to each other in any order, and each of R 6a , R 6b , R 7a , R 7b and R 8 is arbitrarily selectable for each respective amino acid residue of the cationic polyamino acid.