This is a peptide comprising of 9 arginine residues. It has been shown that poly-Arg peptides composed of 9 arginine residues are able to efficiently translocate across cells. It has also been shown in model systems that Arg-9 translocation involves nucleation of transient pores enabling flow of ions across the membrane. and that it's electrostatic attraction to the phosphate groups of membranes is a key property for its translocation.
Proteins and peptides
1, Wender PA. et al.PNAS USA. 97(24):13003-13008 (2000). 2, Herce HD. et al. Biophys J. 97(7): 1917-1925 (2009).