The short version of peptide purity fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-03-21 and is reviewed periodically as new material appears.
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.
Melanotan II is a synthetic cyclic heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, corresponding to a molecular formula of C50H69N15O9 and a monoisotopic mass near 1024 daltons. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, a peptide hormone produced by cleavage of proopiomelanocortin. A lactam bridge between the aspartate and lysine side chains closes the ring, and the C-terminal amide removes a free carboxyl group. Both modifications increase resistance to enzymatic degradation compared with the linear parent hormone. Four substitutions distinguish it from afamelanotide, the linear analogue studied under the name melanotan I.
Regulatory status differs by country, and in many places supplying the compound for human consumption is unlawful. Vendors frequently label material as intended for research use only, a designation that shifts stated purpose but does not create a legal pathway for personal use. Certificates of analysis accompanying such products vary widely in detail and provenance. Third-party testing exists but is voluntary, and results are rarely linked to a specific lot in a publicly verifiable way.
Identity testing for a synthetic peptide relies on several complementary methods. Reversed-phase high-performance liquid chromatography separates the target from related impurities and reports purity as a percentage of total peak area. Mass spectrometry confirms molecular mass and can reveal deletions or truncations. Amino acid analysis and peptide mapping provide sequence-level confirmation, while counter-ion content and residual solvents are measured separately. A purity figure alone does not establish identity, so a complete dataset combines chromatographic and spectrometric evidence.
Lyophilized peptide powder is generally stored frozen, protected from light and moisture. Tryptophan residues are susceptible to oxidation, and the lactam bridge can hydrolyze under strongly acidic or basic conditions. Solutions prepared for laboratory work degrade faster than dry powder, and repeated freeze-thaw cycles accelerate loss. Common practice is to aliquot solutions before freezing and to avoid alkaline buffers. Reported stability windows vary with concentration, buffer, and temperature, so exact shelf lives are method-specific rather than universal.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
Regulatory treatment varies by country. In the United States, melanotan-2 is not approved for any indication, and products marketed for human use fall outside the approved drug framework. Some other jurisdictions have placed it under prescription controls or listed it as a prohibited or restricted substance. Online listings frequently describe the material as a research chemical, a category that does not carry the same manufacturing and labelling requirements as approved medicines.
Solid peptide material is generally stable when kept cold and dry. Common practice is storage at -20 degrees Celsius or lower, with desiccant and protection from light. Repeated freeze-thaw cycles and exposure to moisture are associated with degradation, aggregation, or loss of material. Once dissolved, stability depends on solvent, concentration, and temperature, and solutions are usually treated as short-lived unless stability data support longer periods. Handling notes typically emphasise minimising time at ambient temperature.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
=== Insulin signaling === IGF-1 binds to at least two cell surface receptors: the IGF1 Receptor (IGFR), and the insulin receptor. The IGF-1 receptor seems to be the "physiologic" receptor—it binds IGF-1 at significantly higher affinity than it binds insulin. Like the insulin receptor, the IGF-1 receptor is a receptor tyrosine kinase—meaning it signals by causing the addition of a phosphate molecule on particular tyrosines. IGF-1 activates the insulin receptor at approximately 10% the potency of insulin. Part of this signaling may be via IGF1R/insulin receptor heterodimers (the reason for the confusion is that binding studies show that IGF-1 binds the insulin receptor 100-fold less well than insulin, yet that does not correlate with the actual potency of IGF-1 in vivo at inducing phosphorylation of the insulin receptor, and hypoglycemia).
==== Inert ==== Inert IUDs are not approved for use in the United States, the UK, or Canada. Inert IUDs do not have a bioactive component. They are made of inert materials such as stainless steel or plastic. Their primary mechanism of action is to cause a local foreign body reaction, which makes the uterine environment hostile to both sperm and implantation. They may have higher rates of preventing pregnancy after fertilization, instead of before fertilization, compared to copper or hormonal IUDs.
=== Australia === In-N-Out Burger has also had other similarly named imitators in Australia that confuse consumers into thinking that the businesses is associated with the Californian-based chain. The company would take the imitators to court for trademark infringement and has opened one-day pop-ups in Sydney in 2012, 2013, 2016, 2017, 2019, and 2022; Brisbane in 2020; Melbourne in 2014 and 2018; and Perth in 2018 and 2022 to preserve their trademark rights. Customers may wait for several hours before the doors open, but the food would run out very quickly, sometimes in less than hour after opening. Although In-N-Out may not have plans to open a permanent location outside its current operating region, the business strategy of having one-day pop-ups is to maintain a business presence in the country under Australian trademark law without opening a permanent restaurant. In-N-Out successfully defended their trademarks and intellectual property rights in Australia in 2020 against Hashtag Burgers Pty Ltd, formerly doing business as "Funk N Burgers" and "Down-N-Out Burger". In 2021, In-N-Out filed a lawsuit against Queensland-based Rich Asians Pty Ltd doing business as "In & Out Aussie Burgers".
=== Role in peripheral nerve repair === Laminins are enriched at the lesion site after peripheral nerve injury and are secreted by Schwann cells. Neurons of the peripheral nervous system express integrin receptors that attach to laminins and promote neuroregeneration after injury.
intermolecular force Any force that mediates interaction between molecules, e.g. electromagnetic forces of attraction or repulsion, hydrogen bonding, and the van der Waals force, all of which act between the atoms of one molecule and the atoms or ions of nearby molecules. Intermolecular forces are weak compared to intramolecular forces such as covalent bonds, which hold individual molecules together.
Sources: en.wikipedia.org
No experimental values can be taken at negative 1/[S]; the lower limiting value 1/[S] = 0 (the y-intercept) corresponds to an infinite substrate concentration, where 1/v=1/Vmax thus, the x-intercept is an extrapolation of the experimental data taken at positive concentrations. More generally, the Lineweaver–Burk plot skews the importance of measurements taken at low substrate concentrations and thus can yield inaccurate estimates of Vmax and KM. A more accurate linear plotting method is the Eadie–Hofstee plot. In this case, v is plotted against v/[S]. In the third common linear representation, the Hanes–Woolf plot, [S]/v is plotted against [S]. In general, data normalisation can help diminish the amount of experimental work and can increase the reliability of the output, and is suitable for both graphical and numerical analysis.
He named this the "asteroid hypothesis" as an astronomical analogy: just as there is an asteroid belt instead of a single planet between Mars and Jupiter, so the place below yttrium was thought to be occupied by all the lanthanides instead of just one element.
"The terms mental health promotion and prevention have often been confused. Promotion is defined as intervening to optimize positive mental health by addressing determinants of positive mental health (i.e. protective factors) before a specific mental health problem has been identified, with the ultimate goal of improving the positive mental health of the population. Mental health prevention is defined as intervening to minimize mental health problems (i.e. risk factors) by addressing determinants of mental health problems before a specific mental health problem has been identified in the individual, group, or population of focus with the ultimate goal of reducing the number of future mental health problems in the population." In order to improve mental health, the root of the issue has to be resolved. "Prevention emphasizes the avoidance of risk factors; promotion aims to enhance an individual's ability to achieve a positive sense of self-esteem, mastery, well-being, and social inclusion." Mental health promotion attempts to increase protective factors and healthy behaviors that can help prevent the onset of a diagnosable mental disorder and reduce risk factors that can lead to the development of a mental disorder. Yoga is an example of an activity that calms one's entire body and nerves.
=== Consumer use as normal === Some consumers can face the difficult position of being unable to afford their medication, and choosing between using expired medication or forgoing medication. An epipen is an example of an expensive medication which someone might consider using after expiration because of inability to purchase newer medication. Some common drugs which authorities say are always unsafe if expired include nitroglycerin, insulin, and liquid antibiotics. Consumers sometimes store drugs which they ought not use, regardless of being expired. People who have leftover antibiotics might feel that they can use them safely if they are not expired, or even if they are expired. Medical authorities recommend that no one use prescription drugs except under a physician's care. Authorities also encourage care in storing over-the-counter drugs, discarding them on a regular schedule, and using them as directed when appropriate.
Sources: en.wikipedia.org
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.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
Dry powder is usually held frozen, shielded from light, and kept away from moisture. Desiccant packaging limits hydrolysis during storage. Solutions are typically aliquoted and frozen once, because repeated thawing shortens useful life.