# What Is Melanotan 2? The Melanocortin Peptide Explained > What is Melanotan 2? A plain-English explainer of the synthetic melanocortin peptide — its structure, where it came from, its names (MT2, Melanotan II), and what it does. A clear, cited walk-through of what the molecule is, where it came from, and what those receptor names actually mean. ## The gist So, **what is melanotan 2**? It's a lab-made peptide — a short chain of amino acids, the building blocks of proteins — designed to copy and outperform a natural body hormone called alpha-MSH. Alpha-MSH is the signal your body uses to tell pigment cells to darken your skin. Melanotan 2 is a tougher, longer-lasting version that locks onto the same receptors and turns the dial up hard. Scientists at the University of Arizona built it in the late 1980s. The point was to trigger a protective tan without sun, and maybe cut skin-cancer risk. It darkens skin without UV, and it also acts in the brain to curb appetite and trigger erections. It is not approved as a medicine or a tanning product anywhere. Below: the structure, the names you'll see it called, and how it differs from its better-known relatives. ## The molecule itself Melanotan 2 is a cyclic (ring-shaped) heptapeptide — seven amino acids closed into a loop by an internal bond called a lactam bridge. That ring is the trick: it makes the molecule resist the enzymes that would chew up a normal linear peptide, so it lasts longer and hits harder than alpha-MSH [50]. Its full chemical sequence is Ac-Nle4-cyclo[Asp5-His6-D-Phe7-Arg8-Trp9-Lys10]-NH2, with a molecular weight of about 1024 daltons and the formula C50H69N15O9. It was characterized in early studies as a superpotent cyclic analog of alpha-MSH being evaluated for skin-cancer chemoprevention, with measured properties like an octanol/water log partition coefficient of 2.82 [43]. In short: a small, sturdy, ring-shaped copy of a pigment hormone, engineered to be more powerful than the original. ## Melanotan, MT2, and Melanotan ii — the name soup The names cause real confusion, so here's the map. **Melanotan** on its own is ambiguous — it can mean either of two related peptides. **Melanotan I** (now the approved drug afamelanotide) is the linear analog with relatively MC1R-selective, mostly-pigment activity. **Melanotan II** is the cyclic, non-selective one this site is about [3]. **MT2** is just shorthand for Melanotan 2 (you'll also see MT-2, MT-II, and MTII). **Melanotan ii** is the same compound written with Roman numerals. They all point to the identical molecule: the non-selective melanocortin agonist with broad activity across MC1R-MC5R. When someone online says "melanotan" and means the tanning injection, they almost always mean Melanotan 2. ## Why it does so many different things Because Melanotan 2 is non-selective, it hits all five melanocortin receptors, and each one runs a different job [1]. MC1R sits on skin pigment cells and controls tanning. MC4R sits in the brain and controls appetite and sexual function. MC3R handles energy balance. MC5R works in oil glands. One molecule, five switches — which is exactly why a tanning peptide also suppresses hunger and triggers erections. Its relatives split those jobs up. Afamelanotide (Melanotan I) leans toward pigment and is approved for a rare light-sensitivity disease. A separate, approved sexual-function agonist developed from this scaffold was tuned toward the brain receptor with less pigment activity [3]. Melanotan 2 is the unselective parent that does all of it at once — and carries the broad side-effect profile to match. For the receptor-by-receptor detail, head to the [melanotan 2 mechanism of action](/mechanism-of-action) page. --- Bright, plain-English digests of the Melanotan 2 literature — the science and the risks, never a sales pitch or a prescription.