The short version of reference standard fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-06-21 and is reviewed periodically as new material appears.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Analogue of alpha-melanocyte-stimulating hormone |
| Common synonyms | MT-II; melanotan 2 | No internationally accepted non-proprietary name |
| Typical presentation | Lyophilised powder in a sealed vial | Often supplied alongside a separate diluent |
| Regulatory status | Unapproved therapeutic substance | Customs seizure reported in several jurisdictions |
| Reported route in use | Subcutaneous injection | Self-administered outside clinical settings |
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.
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.
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.
In the US, an increase in gross income will never reduce a taxpayer's post-tax earnings (net income) by putting them in a higher tax bracket. Tax brackets specify marginal tax rates: only income earned in the higher tax bracket is taxed at the higher rate. An increase in gross income can reduce net income in a welfare trap, however, when benefits are withdrawn when passing a certain income threshold. Prevalence of the misconception varies by political party affiliation. Constructing new housing decreases the cost of rent and the price of homes in both the immediate neighborhood and in the city as a whole. In real estate economics, "supply skepticism" leads many Americans to misunderstand the effect of increasing the supply of housing on housing costs. The misconception is unique to the housing market. Businesses do not get a tax benefit by collecting charitable donations from their customers. Corporation taxes are based on profit; the customer's donation would not change the amount of profit and therefore the tax payable. A business would need to donate its own money to receive a tax break. Import tariffs are taxes paid to the government by importers, not by exporting countries or manufacturers as is claimed by some, including Donald Trump. There is a near-unanimous consensus among economists that tariffs have a net-negative effect on economic growth and welfare, and harm consumers through higher prices by more than they benefit domestic producers and governments.
According to Bucknell, SN 35.106 describes a non-linear "branched version" of dependent origination in which consciousness is derived from the coming together of the sense organs and the sense objects (and thus represents sense perception). The Mahānidānasutta (DN 15) describes a "looped version", in which consciousness and nama-rupa condition each other. It also describes consciousness descending into the womb. According to Bucknell, "some accounts of the looped version state explicitly that the chain of causation goes no further back than the loop. Waldron also mentions idea that in early Buddhism, consciousness may have been understood as having these two different aspects (basic consciousness or sentience and cognitive sense consciousness). While these two aspects were largely undifferentiated in early Buddhist thought, these two aspects and their relation was explicated in later Buddhist thought, giving rise to the concept of alaya-vijñana. In yet another linear version, dubbed the "Sutta-nipata version", consciousness is derived from avijja ("ignorance") and saṅkhāra ("activities" also translated as "volitional formations").
Federal agencies in the United States, such as the National Institute of Health (NIH) and National Science Foundation (NSF), have also funded research that pertains to best practices in teaching and learning of neuroscience concepts.
Sources: en.wikipedia.org
== Function == NAXE binds to APOA1, APOA2, and high-density lipoprotein (HDL). In addition, APOA1BP appears to play a role in sperm capacitation. It has been demonstrated that APOA1BP is involved in angiogenesis regulation, by accelerating cholesterol efflux from endothelial cells to HDL. It is known that zebrafish NAXE ortholog Aibp is involved in angiogenesis regulation. The protein was also shown to be involved in atherosclerosis protection.
The hydrocarbon-generating potential and thermal maturity of petroleum source rocks are commonly evaluated using Rock-Eval pyrolysis and vitrinite reflectance measurements, which provide quantitative indicators of organic matter type, maturation level, and the likelihood of oil or gas generation. Catagenesis was pyrolytic despite the fact that it happened at relatively low temperatures (when compared to commercial pyrolysis plants) of 60 to several hundred °C. Pyrolysis was possible because of the long reaction times involved. Heat for catagenesis came from the decomposition of radioactive materials of the crust, especially 40K, 232Th, 235U and 238U. The heat varied with geothermal gradient and was typically 10–30 °C per km of depth from the Earth's surface. Unusual magma intrusions, however, could have created greater localized heating.
Like eukaryotic protein kinases (ePKs) the different isoforms of the CK1 family consist of a N-terminal and a C-terminal lobe (N- and C-lobe, respectively), which are connected via a hinge region. While the N-lobe is mainly composed by β-sheet strands, the larger C-lobe predominantly consists of α-helical and loop structures. Between both lobes a catalytic cleft is formed, accommodating substrates and ATP for the kinase reaction.
Sources: en.wikipedia.org
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.
It was developed in the 1980s by researchers investigating analogues of alpha-melanocyte-stimulating hormone for pigmentation and related endpoints. Early work included small human studies during the 1990s. Development did not progress to licensing, and the compound remained a research and grey-market item.
Peptides are prone to truncation, oxidation and aggregation during synthesis and handling. Without independent testing, a buyer cannot confirm the identity or the content of a vial. Analytical surveys of unapproved peptide products have repeatedly found discrepancies between label claims and measured composition.
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.