D-Arg9 (r9) - Nona-D-Arginine

Nona-D-Arginine (r9, respective sequence: rrrrrrrrr) belongs to the group of cell penetrating peptide (CPPs) which are characterised by their ability to promote the receptor-independent cellular uptake of membrane-impermeable macromolecules, such as peptides, proteins, nucleic acids and nanoparticles. CPPs are usually short peptides with less than 30 amino acids. They are mostly amphipathic and highly cationic and usually rich of the amino acids arginine and lysine. Cellular internalisation of CPPs is observed for virtually all cells, although with different efficiencies that depend on the CPP, the cargo and the cell type (Verdurmen and Brock 2011, Trends Pharmacol. Sci. 32, 116-124).