What is Melanotan 2?
Melanotan 2 is a synthetic cyclic heptapeptide studied in research for its pharmacological activity at melanocortin receptors, a family of class A G-protein-coupled receptors (GPCRs). It is catalogued under CAS number 121062-08-6 with a molecular formula of C₅₀H₆₉N₁₅O₉ and a molecular weight of 1024.18 g/mol (free base). The compound is supplied as a lyophilized powder for laboratory research and is intended solely for research purposes, not for human use.
Within GPCR pharmacology, Melanotan 2 is studied as a high-affinity agonist at multiple melanocortin receptor subtypes—specifically MC1R, MC3R, MC4R, and MC5R. Its significance as a research tool comes from the combination of its non-selective melanocortin receptor binding profile and its constrained cyclic structure, which confers greater metabolic stability than linear alpha-MSH analogs. These properties make it useful for studying melanocortin receptor activation and downstream signaling in research models where a stable, high-affinity agonist is required.
Research interest in Melanotan 2 spans receptor pharmacology, signal transduction, energy homeostasis models, and structure-activity relationship (SAR) studies of the melanocortin peptide family. It is catalogued separately from its structural relatives alpha-MSH and MT-1 because its pharmacological and structural profile is distinct from both.
What is the molecular structure of Melanotan 2?
Melanotan 2 has a molecular weight of 1024.18 g/mol (free base) and the molecular formula C₅₀H₆₉N₁₅O₉. It is a truncated, cyclized analog of alpha-melanocyte-stimulating hormone (alpha-MSH), incorporating two key structural modifications that define its pharmacological profile.
The first modification is truncation. Melanotan 2 is derived from the 7–13 fragment of alpha-MSH rather than the full 13-amino-acid parent peptide. This truncation retains the pharmacophoric core sequence critical for melanocortin receptor engagement while reducing the overall peptide chain length.
The second modification is cyclization via a lactam bridge between the ε-amino group of lysine and the carboxylate of aspartate within the peptide ring. This intramolecular cyclization constrains the conformation of the peptide backbone into a bicyclic structure, locking the pharmacophoric residues into a geometry that favors receptor binding. The cyclic lactam structure is the primary reason Melanotan 2 exhibits greater proteolytic stability in research assays than linear analogs—constrained conformations present fewer accessible peptide bonds to enzymatic cleavage and maintain receptor-preferred geometry without conformational flexibility.
The research-grade material is characterized to a purity specification of 99.0% by HPLC, with mass spectrometry identity confirmation, and is supplied as a lyophilized white to off-white powder stored at −20°C.
What melanocortin receptors does Melanotan 2 engage in research models?
Melanotan 2 is studied as a non-selective agonist at four of the five melanocortin receptor subtypes: MC1R, MC3R, MC4R, and MC5R. It does not engage MC2R, which is the adrenocorticotropic hormone (ACTH)-specific receptor and is selective for the full POMC-derived peptide ACTH rather than alpha-MSH analogs.
MC1R. Expressed in multiple cell types, MC1R is a canonical melanocortin receptor studied in the context of GPCR signaling and cAMP-mediated signal transduction research. It couples primarily through Gαs to activate adenylyl cyclase, increasing intracellular cAMP.
MC3R. Expressed in the central nervous system and peripheral tissues, MC3R is studied in research models of energy balance signaling. Its role in feeding behavior circuitry and energy homeostasis research makes it a target of interest in neuroendocrine pharmacology.
MC4R. Among the most extensively studied melanocortin receptors, MC4R is expressed in the hypothalamus and has a well-characterized role in energy homeostasis and satiety signaling pathways. It is a significant target in metabolic research programs examining central regulation of energy intake and expenditure in preclinical models.
MC5R. Expressed in peripheral tissues including various exocrine glands, MC5R is studied in the context of secretory function research and peripheral melanocortin signaling.
The multi-subtype binding profile of Melanotan 2 is what distinguishes it from more selective melanocortin research tools and is a primary variable in experimental design when receptor subtype specificity is required.
What is the melanocortin receptor system studied in research?
The melanocortin system is a GPCR signaling network defined by five receptor subtypes (MC1R–MC5R), endogenous ligands derived from pro-opiomelanocortin (POMC), and endogenous antagonists including agouti signaling protein (ASIP) and agouti-related protein (AgRP). Melanotan 2 is studied as a pharmacological tool within this system, primarily because it provides a stable, high-affinity agonist probe for multiple receptor subtypes.
POMC is a precursor protein cleaved in a tissue-specific manner to produce multiple bioactive peptides including alpha-MSH, beta-MSH, gamma-MSH, and ACTH. Each of these endogenous peptides has a distinct receptor subtype preference profile. Alpha-MSH is the reference agonist most closely related to Melanotan 2 structurally, engaging MC1R, MC3R, MC4R, and MC5R through the shared His-Phe-Arg-Trp pharmacophore sequence conserved across melanocortin ligands.
Research programs studying this system use Melanotan 2 in contexts where a chemically stable, non-selective melanocortin agonist is needed for in vitro receptor binding assays, functional cAMP signaling assays, or in vivo pharmacological studies in preclinical models. Its stability advantage over alpha-MSH is the main reason it is catalogued as a distinct research compound rather than treated as interchangeable with its endogenous counterpart.
How does Melanotan 2 compare to alpha-MSH as a research tool?
Alpha-MSH is the endogenous reference ligand for the melanocortin receptor system and is the structural parent of Melanotan 2. The two compounds differ in chain length, structural conformation, and proteolytic stability—all of which affect how they are used in research settings.
| Property | Alpha-MSH | Melanotan 2 |
|---|---|---|
| Sequence length | 13 amino acids (linear) | 7 amino acids (truncated, cyclic) |
| Structure type | Linear peptide | Cyclic lactam heptapeptide |
| Receptor profile | MC1R, MC3R, MC4R, MC5R | MC1R, MC3R, MC4R, MC5R |
| Structural stability | Conformationally flexible linear chain | Lactam-constrained rigid conformation |
| Proteolytic stability | Moderate — susceptible to peptidase cleavage | Higher — cyclic structure limits enzyme access |
| Research role | Endogenous reference ligand | High-affinity synthetic agonist probe |
The conformational rigidity introduced by the cyclic lactam structure in Melanotan 2 is both a structural advantage and a pharmacological variable. The constrained geometry pre-organizes the pharmacophoric residues for receptor engagement, which is the mechanistic basis for its high binding affinity across the MC1R, MC3R, MC4R, and MC5R subtypes. For research designs requiring longer assay windows or conditions where linear peptide stability is limiting, Melanotan 2 is the standard alternative to alpha-MSH in the published melanocortin receptor literature.
For a related compound with a distinct receptor binding profile and longer chain length, see the full AminoZone compound catalog.
What does published research describe about concentration-response characteristics at melanocortin receptors?
Published receptor pharmacology research characterizes Melanotan 2 as a high-affinity agonist at each of its four target receptor subtypes, with binding affinities (reported as Ki values in displacement assays) in the low-nanomolar range for MC1R and MC4R. Functional potency in cAMP accumulation assays—measured as EC50—follows a similar pattern, with the compound showing robust concentration-response relationships at physiologically relevant receptor expression levels in standard cell-based assay formats.
Research on the selectivity profile documents that Melanotan 2 engages MC3R and MC5R with somewhat lower affinity than MC1R and MC4R, making it a useful pharmacological comparator when studying receptor subtype contributions in mixed receptor expression systems. This selectivity gradient has been exploited in SAR studies comparing the pharmacophoric requirements across melanocortin receptor subtypes.
The concentration-response behavior is studied primarily in recombinant receptor expression systems and primary cell cultures where receptor subtype expression can be controlled. AminoZone makes no therapeutic or outcome claims regarding Melanotan 2; it is studied solely for its GPCR pharmacological properties at melanocortin receptor subtypes in research settings.
What handling and storage requirements apply to Melanotan 2?
Melanotan 2 is supplied as a lyophilized powder and is stored at −20°C to maintain structural integrity. As a cyclic peptide, it is more stable than linear analogs under equivalent conditions, but the lyophilized material remains sensitive to moisture, oxidation, and repeated freeze-thaw exposure. Research handling practices that support reproducibility include maintaining consistent cold storage, limiting freeze-thaw cycles, and protecting the lyophilized material from humidity during handling.
Cold-chain shipping conditions are relevant for the same reason. The structural integrity of the peptide at the point of synthesis and purification—where the 99.0% purity specification is established—depends on temperature-controlled transit to preserve that specification through to the researcher. Thermal excursion during shipping is one of the more common sources of specification drift for lyophilized peptides.
This article does not provide reconstitution or preparation instructions. Handling and preparation protocols are determined by the researcher according to their experimental requirements and applicable regulations.
How does AminoZone supply Melanotan 2?
AminoZone supplies Melanotan 2 as a research-grade compound held to a minimum purity specification of 99.0% by HPLC, with mass spectrometry identity confirmation. Every order ships with a batch-specific Certificate of Analysis, and all shipments are cold-chain packaged as standard to protect the lyophilized material in transit.
For context on what these analytical specifications mean in practice—what HPLC purity quantifies, what MS identity confirms, and why batch-specific documentation matters—see our overview of research peptide purity standards. For the full catalog of melanocortin-related and other research peptides available, browse all compounds. Melanotan 2 specifications, available sizes, and pricing are detailed on the Melanotan 2 product page. All material is intended for laboratory research use only. Not for human use.
This compound is a research chemical intended for laboratory and scientific research purposes only. It is not a drug, supplement, or food product, and is not intended to diagnose, treat, cure, or prevent any disease. AminoZone does not sell products for human consumption. Researchers are responsible for compliance with all applicable local, state, and federal regulations governing the purchase and use of research materials.