Compound profile

Melanotan II

Melanotan II (MT-II) is a synthetic cyclic heptapeptide analog of α-melanocyte-stimulating hormone (α-MSH) that acts as a non-selective agonist across the melanocortin receptor family (MC1R–MC5R). It is supplied as a reference compound for in-vitro melanocortin receptor pharmacology and biochemical research only.

View product · from $45

What it is

Melanotan II is a synthetic, conformationally constrained cyclic heptapeptide derived from the structure of native α-MSH. Its primary structure is Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, cyclized through a lactam bridge formed between the side-chain carboxyl of the aspartate residue (position 2) and the side-chain amine of the lysine residue (position 7), giving the (2→7) macrocycle. The peptide retains the conserved His-D-Phe-Arg-Trp pharmacophore core that mediates recognition at melanocortin G-protein-coupled receptors, while the cyclization and the D-phenylalanine substitution increase rigidity and resistance to enzymatic degradation relative to the linear α-MSH parent. The free base has the molecular formula C50H69N15O9 and an average molecular weight of approximately 1024.18 g/mol; it is most commonly handled in laboratory settings as the acetate salt. In research contexts it serves as a well-characterized non-selective melanocortin receptor probe.

Mechanism (in-vitro research context)

In vitro, Melanotan II binds the melanocortin receptor subtypes (MC1R, MC3R, MC4R, and MC5R), a family of class-A G-protein-coupled receptors that couple primarily to Gαs. Receptor engagement promotes activation of adenylate cyclase and an increase in intracellular cyclic AMP (cAMP), which is the standard functional readout in transfected cell-line assays. Radioligand competition binding and cAMP accumulation studies in membrane preparations and recombinant cell systems characterize MT-II as a potent, broadly non-selective agonist, with reported nanomolar to sub-nanomolar affinities and an affinity rank order generally placing MC1R and MC4R highest. The conserved His-D-Phe-Arg-Trp motif and the constrained macrocyclic backbone underlie its high binding affinity and agonist efficacy. These properties make it a frequently used positive-control or reference agonist for comparative melanocortin receptor pharmacology in vitro.

Research areas

Radioligand competition binding assays at recombinant MC1R, MC3R, MC4R, and MC5R subtypes
cAMP accumulation / adenylate cyclase activation assays in melanocortin-receptor-transfected cell lines
Structure-activity relationship (SAR) studies of cyclic α-MSH analogs and the His-Phe-Arg-Trp pharmacophore
Comparative GPCR agonist-efficacy and potency profiling as a non-selective reference agonist
Receptor-subtype selectivity and functional-selectivity (biased signaling) characterization in vitro
Analytical method development and reference-standard characterization (HPLC/MS) for melanocortin peptides

Chemistry

Molecular weight: 1024.18 g/mol (free base)
CAS: 121062-08-6
Formula: C50H69N15O9
Sequence: Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, cyclic (2→7) lactam (Asp2 side chain to Lys7 side chain)

Laboratory handling

For laboratory use, Melanotan II is typically supplied as a lyophilized powder and stored desiccated at -20 °C, where it is stable for extended periods; long-term archival storage at -80 °C is also suitable. The lyophilized solid should be protected from light, moisture, and repeated temperature cycling. Stock solutions are prepared in an appropriate solvent (e.g., deionized water or dilute aqueous buffer; small amounts of acetic acid or DMSO may aid solubility for certain analytical workflows) and should be aliquoted to minimize freeze-thaw cycles, which can degrade peptide integrity. Reconstituted solutions are generally held short-term at 2–8 °C and longer-term frozen. Analytical stability and purity are monitored by reversed-phase HPLC and mass spectrometry. This information addresses laboratory storage and analytical stability only.

FAQ

What is the amino acid sequence of Melanotan II?

It is a cyclic heptapeptide with the sequence Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, cyclized through a lactam bridge between the Asp (position 2) side chain and the Lys (position 7) side chain, i.e., the (2→7) lactam.

What are the molecular formula and molecular weight?

The free base has the molecular formula C50H69N15O9 and an average molecular weight of approximately 1024.18 g/mol. In practice it is often handled as the acetate salt, which has a correspondingly higher mass.

What is the CAS number?

The CAS Registry Number for Melanotan II (non-salt) is 121062-08-6.

How is purity verified in the laboratory?

Purity is typically assessed by reversed-phase high-performance liquid chromatography (RP-HPLC), with identity confirmed by mass spectrometry (e.g., ESI-MS or MALDI-TOF). Research-grade reference material is commonly characterized at ≥95% purity.

How should it be stored in the lab?

Store the lyophilized powder desiccated at -20 °C (or -80 °C for long-term archival), protected from light and moisture. Prepare solutions in an appropriate solvent, aliquot to avoid repeated freeze-thaw cycles, and keep reconstituted material frozen for longer-term storage.

What receptors does it act on in vitro?

Melanotan II is a non-selective agonist at the melanocortin receptor family (MC1R, MC3R, MC4R, and MC5R), Gαs-coupled GPCRs whose activation increases intracellular cAMP in receptor-expressing cell systems.

References

Research-use only

For laboratory research use only. Not for human or veterinary use. Not for diagnostic or therapeutic use. These products have not been approved or evaluated by the U.S. Food and Drug Administration. No statement on this site has been evaluated by the FDA. These products are not intended to diagnose, treat, cure, mitigate, or prevent any disease, and are not intended for human or veterinary use. See our research-use terms and terms of service.