The (Lys) 9 peptide, which is formed by the condensation of 9 lysines, is a peptide that can penetrate the cell membrane. (Lys) 9 peptide is often used as a primer. The continuous synthesis of 9 identical amino acids is rarely seen in peptide synthesis, but the peptide synthesis process of (Lys)9 peptide is not complicated. (Lys) 9 peptide has very good hydrophilicity.