This is a peptide composed of 9 D-Arginine residues and an activated cysteine residue C(Npys), wherein Npys is 3-Nitro-2-pyridinesulfenyl group protects cysteine. This kind of modification has been used to render this peptide as a carrier peptide applicable in conjugation and cell permable studies. The S(Npys) group of this cysteine-containing 9R is capable of reacting selectively with the free thiol group of another cysteine-containing peptide to form an unsymmetrical disulfide bond.