The short version of cyclic heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-09-03. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic cyclic heptapeptide | Analog of alpha-MSH with an internal lactam bridge |
| Molecular weight | Approximately 1024 daltons | Free base value; salt forms differ |
| Appearance | White to off-white powder | Usually supplied as a lyophilized solid |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar solvents |
| Typical storage | −20 °C, dry, protected from light | Repeated freeze-thaw cycles degrade peptides |
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
The relationship later improved starting from 2024. While China has historically been wary of getting closer to the Middle East countries, Xi has changed this approach, getting closer to both Iran and Saudi Arabia.
=== 1996–2000 === On December 31, 1996, Quest Diagnostics became an independent company as a spin-off from Corning. Kenneth W. Freeman was appointed as CEO during this transition. Over the next year, Quest acquired a clinical laboratory division of Branford, Connecticut–based Diagnostic Medical Laboratory, Inc. (DML). Two years later in 1999, Quest added SmithKline Beecham Clinical Laboratories to their subsidiaries; which includes a joint venture ownership with CompuNet Clinical Laboratory. The purchase of SmithKline Beecham also included the lab's medical sample transport airline (ICAO: LBQ, call sign: LABQUEST) originally founded in 1988. In 1997, Quest and Banner Health formed a joint venture creating the Arizona based Sonora Quest laboratory, a business unit of Laboratory Sciences of Arizona. This entity represents the operations of Quest Diagnostics in the Arizona regional market.
"I called this idea the central dogma, for two reasons, I suspect. I had already used the obvious word hypothesis in the sequence hypothesis, and in addition I wanted to suggest that this new assumption was more central and more powerful. ... As it turned out, the use of the word dogma caused almost more trouble than it was worth. Many years later Jacques Monod pointed out to me that I did not appear to understand the correct use of the word dogma, which is a belief that cannot be doubted. I did apprehend this in a vague sort of way but since I thought that all religious beliefs were without foundation, I used the word the way I myself thought about it, not as most of the world does, and simply applied it to a grand hypothesis that, however plausible, had little direct experimental support."
=== Central post-stroke pain === Amitriptyline has also been reported to be effective in treating central post-stroke pain following lateral medullary infarction (Wallenberg Syndrome), particularly in patients with thermal dysesthesia. In a long-term observational study of 63 patients with brainstem stroke, 16 developed central pain, and all responded to amitriptyline, often relapsing when treatment was discontinued.
Sources: en.wikipedia.org
=== Amino acid composition === Plant OTCs have the largest difference from other OTCs. There are 50 to 70% less Leu residues, while there are twice as many Arg residues. The number of subunits in OTCs vary from 322 to 340 residues. Animals have the highest density of Leu. This residue breakdown causes a pI for the animal enzyme of 6.8 while the plant enzyme has a pI of 7.6. Rat, bovine, and human OTC have the same C terminal residue of phenylalanine. Their N-terminal residues on the other hand differ. Rat ends with Ser, bovine with aspartate, and human with glycine.
== See also == Torricelli's law Coandă effect Euler equations – for the flow of an inviscid fluid Hydraulics – applied fluid mechanics for liquids Navier–Stokes equations – for the flow of a viscous fluid Teapot effect Terminology in fluid dynamics
Most tests will incorporate a second line which contains a further antibody (one which is not specific to the analyte) that binds some of the remaining colored particles which did not bind to the test line. This confirms that fluid has passed successfully from the sample-application pad, past the test line. By giving confirmation that the sample has had a chance to interact with the test line, this increases confidence that a visibly-unchanged test line can be interpreted as a negative result (or that a changed test line can be interpreted as a negative result in a competitive assay).
Soybean meal is used in food and animal feeds, principally as a protein supplement, but also as a source of metabolizable energy. Typically 1 bushel (i.e. 60 lbs. or 27.2 kg) of soybeans yields 48 lbs. (21.8 kg) of soybean meal. Most soybean meal is defatted, produced as a co-product of soybean oil extraction. Some, but not all, soybean meal contains ground soybean hulls. Soybean meal is heat-treated during production, to denature the trypsin inhibitors of soybeans, which would otherwise interfere with protein digestion.
== Aftermath == In the aftermath of the incident, security protocols at the facility were strengthened, including tighter restrictions on tool access. The North Carolina prison system also improved safety by equipping guards with body armor and providing supervisors with tasers. On October 12, 2022—the fifth anniversary of the failed escape—staff at Pasquotank held a moment of silence and released balloons in remembrance.
Sources: en.wikipedia.org
=== R139w === One further single nucleotide polymorphism, found homozygous in 0% to 5% of different ethnic population, is leading to an amino acid exchange on position 139 from arginine to tryptophane. Furthermore, an alternative RNA splicing site is created leading to a loss of the quinone binding site. The variant protein of NQO1*3 has similar stability as its wild-type counterpart. The variation between the two is substrate specific and it has reduced activity for some substrates. It has been recently shown that the NQO1*3 polymorphism may also lead to reduced NQO1 protein expression.
=== List of side effects === Cardiovascular: Myocardial infarction; stroke; heart block; arrhythmias; hypotension, particularly orthostatic hypotension; hypertension; tachycardia; palpitation. Psychiatric: Confusional states (especially in the elderly) with hallucinations, disorientation, delusions, anxiety, restlessness, agitation; hypomania; exacerbation of psychosis; insomnia, panic, and nightmares. Neurological: Seizures; incoordination; ataxia; tremors; peripheral neuropathy; numbness, tingling, and paresthesias of extremities; extrapyramidal symptoms; drowsiness; dizziness; weakness and fatigue; headache; syndrome of inappropriate ADH (antidiuretic hormone) secretion; tinnitus; alteration in EEG patterns. Anticholinergic: Paralytic ileus; hyperpyrexia; urinary retention, delayed micturition, dilatation of the urinary tract; constipation; blurred vision, disturbance of accommodation, increased intraocular pressure, mydriasis; dry mouth and rarely associated sublingual adentitis. Allergic: Drug fever; petechiae, skin rash, urticaria, itching, photosensitization (avoid excessive exposure to sunlight); edema (general, or of face and tongue). Hematologic: Agranulocytosis; bone marrow depression; leukopenia;thrombocytopenia; purpura; eosinophilia. Gastrointestinal: Nausea and vomiting; anorexia; epigastric distress; diarrhea; peculiar taste; stomatitis; abdominal cramps; black tongue.
Although an estimated 43,000 species of bacteria have been named, most of them have never been studied. In fact, just 10 bacterial species account for half of all publications, whereas nearly 75% of all named bacteria have no academic research devoted to them. The best-studied species, Escherichia coli, has more than 300,000 studies published on it, but many of these papers likely use it only as a cloning vehicle to study other species, without providing any insight into its own biology. 90% of scientific studies on bacteria focus on less than 1% of species, mostly pathogenic bacteria relevant to human health. While E. coli is probably the best-studied bacterium, a quarter of its 4000 genes are poorly studied or remain uncharacterized. Some bacteria with minimal genomes (< 600 genes, e.g. Mycoplasma) usually have a large fraction of their genes functionally characterized, given that most of them are essential and conserved in many other species.
The chemistry of calcium is that of a typical heavy alkaline earth metal. For example, calcium spontaneously reacts with water more quickly than magnesium but less quickly than strontium to produce calcium hydroxide and hydrogen gas. It also reacts with the oxygen and nitrogen in air to form a mixture of calcium oxide and calcium nitride. When finely divided, it spontaneously burns in air to produce the nitride. Bulk calcium is less reactive: it quickly forms a hydration coating in moist air, but below 30% relative humidity it may be stored indefinitely at room temperature. Besides the simple oxide CaO, calcium peroxide, CaO2, can be made by direct oxidation of calcium metal under a high pressure of oxygen, and there is some evidence for a yellow superoxide Ca(O2)2.Calcium hydroxide, Ca(OH)2, is a strong base, though not as strong as the hydroxides of strontium, barium or the alkali metals. All four dihalides of calcium are known. Calcium carbonate (CaCO3) and calcium sulfate (CaSO4) are particularly abundant minerals. Like strontium and barium, as well as the alkali metals and the divalent lanthanides europium and ytterbium, calcium metal dissolves directly in liquid ammonia to give a dark blue solution. Due to the large size of the calcium ion (Ca2+), high coordination numbers are common, up to 24 in some intermetallic compounds such as CaZn13. Calcium is readily complexed by oxygen chelates such as EDTA and polyphosphates, which are useful in analytic chemistry and removing calcium ions from hard water.
== Examples == Numerous endogenous compounds – including hormones, catecholamines such as dopamine and noradrenaline, and many trace amines (e.g. adrenaline, phenethylamine itself, tyramine, thyronamine, and iodothyronamine) – are substituted phenethylamines. Several notable recreational drugs, such as MDPV (Monkey Dust), MDMA (ecstasy), mescaline, methamphetamine, and cathinone, are also members of the class. Many well-known prescription drugs are from the phenylethylamine class such as Adderall which uses Amphetamine, Desoxyn which uses methamphetamine, and Sudafed which uses pseudoephedrine.
Sources: en.wikipedia.org
It is a synthetic seven-amino-acid peptide modeled on alpha-melanocyte-stimulating hormone. It carries two non-natural substitutions and a cyclic bridge that increase its stability relative to the natural hormone. It circulates as a research chemical and is not an approved medicine.
Melanotan-1, also called afamelanotide, is a shorter linear analog with a different amino acid sequence and no lactam ring. It has been evaluated in formal clinical programs, while melanotan-2 has not. The two are distinct molecules and are not interchangeable.
No. Bremelanotide is a related but distinct cyclic peptide that reached approved status for one specific clinical indication. Melanotan-2 is a separate molecule with its own sequence and properties. Shared ancestry in the melanocortin family does not make them the same substance.
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.