This is a synthetic peptide based on the sequence corresponding to residues 359 to 374 of α1-antitrypsin. C105Y can penetrate cell membrane rapidly, enter the cytoplasm, and localize to the nucleus and nucleolus of live culture cells. C105Y peptide is routed to the nucleolus very rapidly in an energy-dependent fashion; whereas membrane translocation and nuclear localization are energy-independent. It enhances gene expression from DNA nanoparticles.