Purity ≥97% as determined by RP-HPLC. Melanotan and Melanotan-II are both analogs of the peptide hormone alpha melanocyte stimulating hormone ( -MSH) that tend to induce skin tanning. Unlike Melanotan, Melanotan-II has the additional effect of increasing libido. Melanotan II has aphrodisiac properties. Molecular weight of 1024.2 dalton. Amino Acid Sequence: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2