This is a peptide comprising of 9 Arginine residues and is synthesized with an activated cysteine residue C(Npys), wherein Npys is 3-Nitro-2-pyridinesulfenyl group protects cysteine..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. Coupling of sulfhydrils has been studied as an effective means to deliver/release therapeutics such as siRNA in the reducing environment within the cell.