MC1R comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-06-23. Where a claim depends on a specific study, the study is described rather than over-claimed.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
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.
Freeze-dried melanotan-2 is normally kept as a desiccated powder at minus twenty degrees Celsius or lower, shielded from light and moisture. Peptides of this size degrade through hydrolysis, oxidation and deamidation, and each pathway accelerates as temperature and water activity rise. Repeated freeze-thaw cycles promote aggregation and loss of material, so aliquoting a stock solution before freezing is standard laboratory practice. Once dissolved, the solution is markedly less stable than the powder. In laboratory work, solutions are generally refrigerated and used within days rather than kept for months.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, which separates the target peptide from truncated or oxidised impurities. Mass spectrometry, most often coupled to liquid chromatography, confirms molecular mass and detects substitutions that chromatography alone may miss. Amino acid analysis and peptide mapping supply additional structural evidence, while nuclear magnetic resonance is reserved for full structural confirmation. Laboratories that examine samples sold online report wide variation in actual content, with some vials containing little or none of the labelled material.
| 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-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
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.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
== Corporate structure == In the financial year 2023, Basilea Pharmaceutica AG, Allschwil generated company sales of CHF 157.6 million and employed 147 people. Since the 2022 financial year, Basilea has consistently been generating operating and net profits. In addition to its headquarters in Allschwil, Switzerland, Basilea is represented by subsidiaries in the UK and Germany. Basilea cooperates with licence and distribution partners in over 100 countries.
This reacts up to 400 fold faster than the original pair with a rate constant of 5.5 ± 0.6 × 105 M−1 s−1. This version is back reactive with the two previous generations of SpyTag/SpyCatcher reagents. SpyTag/SpyCatcher react with specificity even when in the presence of bacterial and mammalian cell environments.
=== Definitions === Normal serum potassium levels are generally considered to be between 3.5 and 5.3 mmol/L. Levels above 5.5 mmol/L generally indicate hyperkalemia, and those below 3.5 mmol/L indicate hypokalemia.
Sources: en.wikipedia.org
Once across the interface, the tails and loops form whatever bonds are favorable. In the case of polymer-on-polymer surfaces, this means more van der Waals forces. While these may be brittle, they are quite strong when a large network of these bonds is formed. The outermost layer of each surface plays a crucial role in the adhesive properties of such interfaces, as even a tiny amount of interdigitation – as little as one or two tails of 1.25 angstrom length – can increase the van der Waals bonds by an order of magnitude.
== Clinical significance == 11-Deoxycortisol in mammals has limited glucocorticoid activity, but it is the direct precursor of the major mammalian glucocorticoid, cortisol. As a result, the level of 11-deoxycortisol is measured to diagnose impaired cortisol synthesis, to find out the enzyme deficiency that causes impairment along the pathway to cortisol, and to differentiate adrenal disorders. In 11β-hydroxylase deficiency, 11-deoxycortisol and 11-deoxycorticosterone levels increase, and excess of 11-deoxycorticosterone leads to mineralocorticoid-based hypertension (as opposed to 21-hydroxylase deficiency, in which patients have low blood pressure from a lack of mineralocorticoids). Low levels of cortisol can affect blood pressure by causing a decrease in sodium retention and volume expansion. This effect occurs because cortisol regulates the balance of water and electrolytes in the body. When cortisol levels are low, there is less sodium reabsorption by the kidneys, leading to increased excretion of sodium through urine. This ultimately reduces blood volume and lowers blood pressure. On the other hand, high levels of cortisol can also affect blood pressure by causing an increase in sodium retention and volume expansion. Cortisol-induced hypertension is accompanied by significant sodium retention, leading to an increase in extracellular fluid volume and exchangeable sodium. This expansion results in an increase in blood volume and subsequently increases blood pressure.
Flutamide acts as a selective, competitive, silent antagonist of the androgen receptor (AR). Its active form, hydroxyflutamide, has between 10- and 25-fold higher affinity for the AR than does flutamide, and hence is a much more potent AR antagonist in comparison. However, at high concentrations, unlike flutamide, hydroxyflutamide is able to weakly activate the AR. Flutamide has far lower affinity for the AR than do steroidal antiandrogens like spironolactone and cyproterone acetate, and it is a relatively weak antiandrogen in terms of potency by weight, but the large dosages at which flutamide is used appear to compensate for this. In accordance with its selectivity for the AR, flutamide does not interact with the progesterone, estrogen, glucocorticoid, or mineralocorticoid receptor, and possesses no intrinsic progestogenic, estrogenic, glucocorticoid, or antigonadotropic activity. However, it can have some indirect estrogenic effects via increased levels of estradiol secondary to AR blockade, and this involved in the gynecomastia it can produce. Because flutamide does not have any estrogenic, progestogenic, or antigonadotropic activity, the medication does not cause menstrual irregularities in women. This is in contrast to steroidal antiandrogens like spironolactone and cyproterone acetate. Similarly to nilutamide, bicalutamide, and enzalutamide, flutamide crosses the blood–brain barrier and exerts central antiandrogen actions.
Sources: en.wikipedia.org
The training of internists is solely focused on adults and does not typically include surgery, obstetrics, or pediatrics. According to the American College of Physicians, internists are defined as doctors "who specialize in the prevention, detection, and treatment of illnesses in adults." While there may be some overlap in the patient population served by both internal medicine and family medicine doctors, internists primarily focus on adult care with an emphasis on diagnosis, whereas family medicine incorporates a holistic approach to care for the entire family unit. Internists also receive substantial training in various recognized subspecialties within the field and are experienced in both inpatient and outpatient settings. On the other hand, family doctors receive education covering a wide range of conditions and typically train in an outpatient setting with less exposure to hospital settings. The historical roots of internal medicine can be traced back to the incorporation of scientific principles into medical practice in the 1800s, while family medicine emerged as part of the primary care movement in the 1960s.
Oligonucleotides remain permanently attached to the solid phase, which requires the use of linkers that are stable under the conditions of the final deprotection procedure. The absence of physical dividers between the sites occupied by individual oligonucleotides, a very limited space on the surface of the microarray (one oligonucleotide sequence occupies a square 25×25 μm) and the requirement of high fidelity of oligonucleotide synthesis dictate the use of site-selective 5'-deprotection techniques. In one approach, the removal of the 5'-O-DMT group is effected by electrochemical generation of the acid at the required site(s). Another approach uses 5'-O-(α-methyl-6-nitropiperonyloxycarbonyl) (MeNPOC) protecting group, which can be removed by irradiation with UV light of 365 nm wavelength.
=== Use by right-to-die societies === High toxicity and relatively easy availability made propoxyphene a drug of choice for right-to-die societies. It is listed in Dr. Philip Nitschke's The Peaceful Pill Handbook and Dr. Pieter Admiraal's Guide to a Humane Self-Chosen Death. "With the withdrawal of the barbiturate sleeping tablets from the medical prescribing list, propoxyphene has become the most common doctor-prescribed medication used by seriously ill people to end their lives."
== Adverse effects == Common side effects include pneumonia and urinary tract infections. Severe side effects may include blood clots or cardiac arrest. Andexanet alfa has a boxed warning that it is associated with arterial and venous blood clots, ischemic events, cardiac arrest, and sudden deaths.
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 lyophilised solid is best kept cold, dry and dark, typically at minus twenty degrees Celsius. Moisture and repeated warming cycles are the main causes of degradation. Solutions prepared from the powder are less stable and are normally used quickly.