This is a working overview of MC1R, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-04-12 and is reviewed periodically as new material appears.
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
Handling guidance for melanotan II follows general practice for small synthetic peptides rather than a product-specific monograph. Lyophilized powder is typically kept at minus twenty degrees Celsius or colder, protected from light and moisture, because warmth and humidity accelerate degradation. Once reconstituted, solutions are usually refrigerated and used within a short window, as hydrolysis and microbial growth both become concerns. Repeated freeze-thaw cycles are generally avoided. These conventions come from laboratory peptide chemistry and not from formal stability studies on this specific compound.
Analytical confirmation of identity relies on mass spectrometry, most often coupled to liquid chromatography. Reversed-phase high-performance liquid chromatography separates the peptide from related impurities and provides a purity estimate based on peak area. Electrospray ionization mass spectrometry then confirms the expected molecular mass, while tandem mass spectrometry can map the fragment sequence. For research-grade material, these two techniques together form the standard minimum. Purity figures reported by vendors are frequently not traceable to an independent laboratory.
Independent verification is central to quality control because the compound is not produced under pharmaceutical manufacturing standards. Third-party laboratories can measure purity, identity, residual solvents, and microbial contamination, though the scope of testing varies between services. Reported analyses of vendor samples have shown batch-to-batch variation in peptide content and the presence of truncated or oxidized species. How much of this variation reflects synthesis conditions versus storage and shipping is not well characterized. No harmonized reference standard exists for the material as sold.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Melanocortin receptor agonist |
| Molecular formula | C50H69N15O9 | Neutral form, mass near 1024.2 g/mol |
| Primary targets | MC1R, MC3R, MC4R, MC5R | Binding is non-selective across subtypes |
| Related compounds | Alpha-MSH, melanotan I, afamelanotide | Structurally or functionally related peptides |
| Common abbreviations | MT-II, MT-2 | Naming in the literature is not uniform |
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.
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.
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.
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.
=== I-Port === The I-Port, manufactured and distributed by Patton Medical Devices, is a domed shaped device with a cannula inserted at a 90° angle. The i-port Advance combines an i-port with an insertion device.
==== Neurological model ==== The theoretical underpinnings of Moniz's psychosurgery were largely commensurate with the nineteenth-century ones that had informed Burckhardt's decision to excise matter from the brains of his patients. Although in his later writings, Moniz referenced both the neuron theory of Ramón y Cajal and the conditioned reflex of Ivan Pavlov, in essence he simply interpreted this new neurological research in terms of the old psychological theory of associationism. He differed significantly from Burckhardt, however in that he did not think there was any organic pathology in the brains of the mentally ill, but rather that their neural pathways were caught in fixed and destructive circuits leading to "predominant, obsessive ideas". As Moniz wrote in 1936:
Mercenaries and multinational corporations such as Chiquita Brands International are some of the international actors that have contributed to the violence of the conflict. Beginning in the mid-1970s Colombian drug cartels became major producers, processors and exporters of illegal drugs, primarily marijuana and cocaine. On 4 July 1991, a new Constitution was promulgated. The changes generated by the new constitution are viewed as positive by Colombian society.
Sources: en.wikipedia.org
A dosage of 1 mg/day oral estradiol is considered to be roughly equivalent to 25 or 50 μg/day transdermal estradiol and a dosage of 2 mg/day oral estradiol is considered to be equivalent to 50 or 100 μg/day transdermal estradiol depending on the source. Estradiol patches delivering a daily dosage of 0.05 mg (50 μg) achieve mean estradiol and estrone levels of 30 to 65 pg/mL and 40 to 45 pg/mL, respectively, while a daily dosage of 0.1 mg (100 μg) attains respective mean levels of 50 to 90 pg/mL and 30 to 65 pg/mL of estradiol and estrone. In general, Climara-type estradiol transdermal patches have an approximate 1:1 ratio of estradiol delivered in μg/day relative to circulating estradiol concentration in pg/mL. In other words, a 100 μg/day Climara estradiol patch may be expected to produce circulating estradiol levels of around 100 pg/mL. Transdermal estradiol patches produce an estradiol to estrone ratio of about 1:1. Following removal of an estradiol patch, circulating estradiol levels decrease to baseline within 24 hours. Typical dosages of estradiol patches are intended to provide the minimum amount of estrogen replacement necessary for the effective alleviation of menopausal symptoms, and for this reason, they achieve relatively low levels of estradiol.
=== Metabolism and body weight === As of 2017, reviews of clinical trials showed that using aspartame (or other non-nutritive sweeteners) in place of sugar reduces calorie intake and body weight in adults and children. A 2017 review of metabolic effects by consuming aspartame found that it did not affect blood glucose, insulin, total cholesterol, triglycerides, calorie intake, or body weight. While high-density lipoprotein levels were higher compared to control, they were lower compared to sucrose. In 2023, the World Health Organization recommended against the use of common non-sugar sweeteners (NSS), including aspartame, to control body weight or lower the risk of non-communicable diseases, stating: "The recommendation is based on the findings of a systematic review of the available evidence which suggests that use of NSS does not confer any long-term benefit in reducing body fat in adults or children. Results of the review also suggest that there may be potential undesirable effects from long-term use of NSS, such as an increased risk of type 2 diabetes, cardiovascular diseases, and mortality in adults."
From late May 1900, the first successes of the Boer guerrilla strategy were at Lindley (where 500 Yeomanry surrendered), and at Heilbron (where a large convoy and its escort were captured) and other skirmishes resulting in 1,500 British casualties in less than ten days. In December 1900, De la Rey and Christiaan Beyers attacked and mauled a British brigade at Nooitgedacht, inflicting 650 casualties. As a result, the British, led by Lord Kitchener, mounted extensive searches for Christiaan de Wet, but without success. However, Boer raids on British army camps and other targets were sporadic and poorly planned, and the nature of the Boer guerrilla war itself had no long-term objectives, with the exception to harass the British. This led to a disorganised pattern of scattered engagements between the British and Boers.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide and a non-selective melanocortin receptor agonist. Structurally it is modelled on alpha-melanocyte-stimulating hormone, a peptide that occurs naturally in the body.
Activation of MC1R increases pigment synthesis independently of ultraviolet exposure, which is the mechanism usually cited for darkening without sun exposure. Ultraviolet light still influences skin response through separate biological pathways.
Because the peptide binds several melanocortin receptor subtypes, its effects are not confined to pigmentation. This complicates interpretation of both intended and unintended outcomes reported in studies.
The lyophilized powder is generally held at minus twenty degrees Celsius or below, away from light and moisture. Reconstituted solutions are typically refrigerated and used quickly. These practices derive from general peptide handling rather than a formal stability study.