Penetratin-Arg is a cell penetrating peptide with a large amount of Arg in its sequence. Penetratin-Arg has a high similarity to the Penetratin sequence, but the lysine in the Penetratin sequence is replaced by arginine. Penetratin-Arg easily forms an α-helical structure under certain conditions and penetrates the cell membrane at a low micromolar concentration without significantly affecting the cell membrane. Penetratin-Arg can also be combined with macromolecules and used as a drug delivery carrier.