Everything below concerns lactam bridge. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-03-16. Numbers and descriptions here follow the published literature rather than marketing material.
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
Lyophilised peptide powder is comparatively stable when kept dry, cold and protected from light. Once dissolved, the molecule is exposed to hydrolysis, oxidation and microbial growth, and degradation accelerates at higher temperatures and in alkaline solution. Repeated freeze-thaw cycles concentrate solutes and promote aggregation. Handling guidance for research peptides commonly clusters around freezer temperatures for powder and short refrigerated use for reconstituted solutions, with pH control and sterile technique applied throughout.
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white solid | Lyophilised cake or flake |
| Solubility class | Soluble in water and aqueous buffer | Also soluble in some polar organic solvents |
| Typical storage temperature | Minus 20 degrees Celsius or below | Desiccated and protected from light |
| Typical analytical method | LC-MS/MS | Reversed-phase separation with mass detection |
| Molecular formula | C50H69N15O9 | Free base; salt forms differ |
Melanotan II holds no marketing authorisation from the Food and Drug Administration, the European Medicines Agency, the UK Medicines and Healthcare products Regulatory Agency or Australia's Therapeutic Goods Administration. Products sold under that name are treated as unapproved new drugs, and their sale or import is prohibited in several jurisdictions. Other countries classify the peptide as a prescription-only medicine or place it among controlled substances, so the legal position changes with the destination market. No pharmacopoeial monograph supplies an official specification, because the material is not a licensed pharmaceutical. Consequently, products offered online are not manufactured to a shared public standard.
The peer-reviewed record is dominated by small early-phase studies, case reports and pharmacovigilance summaries rather than large randomised trials. Papers typically examine tanning response, receptor selectivity or patterns of reported adverse events. Many note that participants obtained the peptide outside a clinical setting, which limits verification of composition and administered amount. Reported events vary widely, and causality is frequently unclear because the identity and purity of self-sourced material are unknown. Open questions include whether repeated melanocortin receptor stimulation produces cumulative effects, and how often label claims match actual content.
Identification in laboratories relies on reversed-phase liquid chromatography coupled with tandem mass spectrometry, with product-ion spectra compared against a certified reference standard. High-resolution mass spectrometry supplies accurate mass confirmation, and peptide mapping after enzymatic digestion separates melanotan II from closely related analogues. Quantitation of seized material is complicated by unknown counter-ions and residual trifluoroacetate left from purification. Immunoassays raised against alpha-melanocyte-stimulating hormone can cross-react, so chromatographic confirmation is normally required. Urinary detection windows are short, and reported limits of detection differ substantially between laboratories.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
The most common cause of ketoacidosis is a deficiency of insulin in type 1 diabetes or late-stage type 2 diabetes. This is called diabetic ketoacidosis and is characterized by hyperglycemia, dehydration and metabolic acidosis. Other electrolyte disturbances such as hyperkalemia and hyponatremia may also be present. A lack of insulin in the bloodstream allows unregulated fatty acid release from adipose tissue which increases fatty acid oxidation to acetyl CoA, some of which is diverted to ketogenesis. This raises ketone levels significantly above what is seen in normal physiology.
== External links == Dhanvantari S. "Molecular and Cellular Mechanisms of Glucagon Synthesis and Secretion". lawsonimaging.ca. Archived from the original on 29 September 2007. "PC1 Cleavage Sites". phoenixpeptide.com. Archived from the original on 28 December 2005. "GLP-1 is Derived From Proglucagon". medscape.com. "Pro-glucagon". PDBe-KB Aggregated Views of Proteins. Wellcome Genome Campus, Hinxton, Cambridgeshire: EMBL-EBI.
. In multi-compartment pharmacokinetics, two operational half-lives are often distinguished: an early distribution (α) half-life governed by redistribution from the central to peripheral compartments, and a later elimination (β) half-life governed by metabolic clearance and excretion. This is used to measure the removal of things such as metabolites, drugs, and signalling molecules from the body. Typically, the biological half-life refers to the body's natural cleansing, the detoxification through liver metabolism and through the excretion of the measured substance through the kidneys and intestines. This concept is used when the rate of removal is roughly exponential. In a medical context, half-life explicitly describes the time it takes for the blood plasma concentration of a substance to halve (plasma half-life) its steady-state when circulating in the full blood of an organism. This measurement is useful in medicine, pharmacology and pharmacokinetics because it helps determine how much of a drug needs to be taken and how frequently it needs to be taken if a certain average amount is needed constantly. By contrast, the stability of a substance in plasma is described as plasma stability. This is essential to ensure accurate analysis of drugs in plasma and for drug discovery. The relationship between the biological and plasma half-lives of a substance can be complex depending on the substance in question, due to factors including accumulation in tissues, protein binding, active metabolites, and receptor interactions.
Eq. 2 The SIMS-SS age equation in years before present Where, Ci is the intrinsic concentration of water, Cs is the saturation concentration, dC/dx is the diffusion coefficient for depth x=0, k is derived from a family of Crank's theoretical diffusion curves, and
Sources: en.wikipedia.org
== Overdose == Enobosarm has been assessed in clinical trials at doses ranging from 0.1 to 18 mg/day. However, most research has been done at doses of 0.1 to 3 mg/day, with two phase 3 clinical trials using a dosage of 3 mg/day. A few small phase 1 and phase 2 trials of enobosarm for breast cancer have employed doses of 9 to 18 mg/day. Larger, phase 3 trials of enobosarm at a dose of 9 mg/day for breast cancer (e.g., ARTEST, n=210) are now underway. Doses of up to 100 mg have been assessed in single-dose pharmacokinetic studies and doses of up to 30 mg/day have been given in short 14-day pharmacokinetic studies. Enobosarm sold via black-market Internet suppliers and used non-medically is often taken at much higher doses than those used widely in clinical trials (e.g., 10–30 mg/day), with unknown adverse effects and risks.
The organization of solvent systems into "families" has greatly facilitated the choice of solvent systems as well. A solvent system can be tested with a one-flask partitioning experiment. The measured partition coefficient from the partitioning experiment will indicate the elution behavior of the compound. Typically, it is desirable to choose a solvent system where the target compound(s) have a partition coefficient between 0.25 and 8. Historically, it was thought that no commercial countercurrent chromatograph could cope with the high viscosities of ionic liquids. However, modern instruments that can accommodate 30 to 70+ % ionic liquids (and potentially 100% ionic liquid, if both phases are suitably customized ionic liquids) have become available. Ionic liquids can be customized for polar / non-polar organic, achiral and chiral compounds, bio-molecule, and inorganic separations, as ionic liquids can be customized to have extraordinary solvency and specificity. After the biphasic solvent system has been chosen a batch of is formulated and equilibrated in a separatory funnel. This step is called pre-equilibration of the solvent system. The two phases are separated. Then the column is filled with stationary with a pump. Next, the column is set an equilibration conditions, such as the desired rotation speed, and the mobile phase is pumped through the column. The mobile phase displaces the a portion of the stationary phase until column equilibration is achieved and the mobile phase elutes from the column.
=== Etymology === Mocro maffia: The name "Mocro maffia" is given by the Dutch-speaking authorities in the Netherlands and Belgium, who refer to Moroccan criminal organisations operating in the Benelux. The term was made public by author Martijn Schrijver in 2013, following the publication of his book Mocro Maffia, released in 2014. However, the term "Mocro" has existed since the 1990s, and is a Moroccan-Dutch slang term that describes someone with a Moroccan immigrant background, in both Belgium and the Netherlands. The term "Mocro Maffia" does not make a distinction between the various organisations that rival each other, but instead describes a network of all Moroccan criminal organisations that are active in the Benelux. Although the majority of members are of Moroccan descent, there are also some members who are from Dutch, Antillean, or Surinamese background. Mocro-oorlog or Mocro-War (Moroccan war): The name by which the media and journalists refer to the Mocro mafia conflict that began in 2012. Borgerokko Maffia: The name by which politicians, media outlets, and journalists refer to the Moroccan criminal networks that are active in Antwerp. The term was adopted by the Belgian writer Raf Sauviller in his book Borgerokko Maffia, which was released in 2017. The term quickly appeared on the front pages of Belgian newspapers.
Sources: en.wikipedia.org
Mass spectrometry combined with liquid chromatography provides both molecular weight confirmation and a measure of related impurities. Tandem mass spectrometry adds sequence information. A purity percentage reported without a mass measurement does not confirm what the material is.
No. Lyophilisation slows degradation rather than stopping it, and the rate depends on residual moisture, temperature and light exposure. Freezer storage extends useful life but does not make the material permanent.
A certificate is only as good as its traceability to a specific batch and a named laboratory. Documents lacking batch numbers, method descriptions or laboratory identifiers carry little weight. Confirming what was actually received generally requires a separate test of the material in hand.
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.