Heptapeptide is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-07-16. Numbers and descriptions here follow the published literature rather than marketing material.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
Melanotan-2, also written Melanotan II, is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and the lactam bridge between the aspartate and lysine side chains constrains the peptide into a ring. This structural change increases receptor affinity and metabolic stability relative to the native hormone. The compound was created in the 1980s as a research tool for studying pigmentation biology.
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.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
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.
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 II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
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.
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.
Chemicals Hydroxylamine Base analogues (e.g., Bromodeoxyuridine (BrdU)) Alkylating agents (e.g., N-ethyl-N-nitrosourea (ENU). These agents can mutate both replicating and non-replicating DNA. In contrast, a base analogue can mutate the DNA only when the analogue is incorporated in replicating the DNA. Each of these classes of chemical mutagens has certain effects that then lead to transitions, transversions, or deletions. Agents that form DNA adducts (e.g., ochratoxin A) DNA intercalating agents (e.g., ethidium bromide) DNA crosslinkers Oxidative damage Nitrous acid converts amine groups on A and C to diazo groups, altering their hydrogen bonding patterns, which leads to incorrect base pairing during replication. Radiation Ultraviolet light (UV) (including non-ionizing radiation). Two nucleotide bases in DNA—cytosine and thymine—are most vulnerable to radiation that can change their properties. UV light can induce adjacent pyrimidine bases in a DNA strand to become covalently joined as a pyrimidine dimer. UV radiation, in particular longer-wave UVA, can also cause oxidative damage to DNA. Ionizing radiation. Exposure to ionizing radiation, such as gamma radiation, can result in mutation, possibly resulting in cancer or death. Whereas in former times mutations were assumed to occur by chance, or induced by mutagens, molecular mechanisms of mutation have been discovered in bacteria and across the tree of life. As S.
Following this report, American neurologist Silas Weir Mitchell tried peyote and published his experience with it in December 1896. After reading Mitchell's article, others, including psychologist and sexologist Havelock Ellis and American psychologist William James tried peyote and described their experiences. The German chemist Arthur Heffter isolated and ingested mescaline from peyote, experiencing psychedelic effects with the pure compound, in 1897, and published his findings in 1898. Austrian chemist Ernst Späth synthesized mescaline for the first time in 1919. The German pharmaceutical company Merck then began distributing pharmaceutical mescaline in 1920. The German psychiatrist Kurt Beringer, a student of Lewin and an acquaintance of Hermann Hesse and Carl Jung, became the father of psychedelic psychiatry and conducted experiments with mescaline in more than 60 people starting in 1921. He published his monograph on the subject, Der Meskalinrausch (Mescaline Intoxication), in 1927. German–American psychologist Heinrich Klüver published his monograph, Mescal: The Divine Plant and Its Psychological Effects, in English in 1928. He is said to have been the first to attempt to provide a phenomenological description of the psychedelic experience. The French pharmacist Alexandre Rouhier also studied and published on peyote and mescaline with his book Le Peyotl: La Plante Qui Fait les Yeux Émerveillés (Peyote: The Plant That Fills the Eyes with Marvels) in 1927.
=== Major endocrine systems === The human endocrine system consists of several systems that operate via feedback loops. Several important feedback systems are mediated via the hypothalamus and pituitary.
=== Magnetic resonance imaging === Magnetic resonance imaging (MRI) is a non-invasive imaging technique that uses strong magnetic fields and radiofrequency pulses to generate detailed anatomical and functional images of the body. MRI provides excellent soft tissue contrast and is widely used in theranostics for its ability to visualize anatomical structures and assess physiological processes. In theranostics, MRI allows for the detection and characterization of tumors, assessment of tumor extent, and evaluation of treatment response. MRI can provide information on tissue perfusion, diffusion, and metabolism, aiding in the selection of appropriate therapies and monitoring their effectiveness. Advancements in MRI technology have expanded its capabilities in theranostics. Techniques such as functional MRI (fMRI) enable the assessment of brain activation and connectivity, while diffusion-weighted imaging (DWI) provides insights into tissue microstructure. The development of molecular imaging agents, such as superparamagnetic iron oxide nanoparticles, allows for targeted imaging and tracking of specific molecular entities.
Sources: en.wikipedia.org
== Adverse effects == Adverse effects of clorazepate include tolerance, dependence, withdrawal reactions, cognitive impairment, confusion, anterograde amnesia, falls in the elderly, ataxia, hangover effects, and drowsiness. It is unclear whether cognitive deficits resulting from the long-term use of benzodiazepines return to normal or persist indefinitely after withdrawal from benzodiazepines. Benzodiazepines are also known to cause or worsen depression. Paradoxical effects including excitement and paradoxical worsening of seizures can sometimes result from the use of benzodiazepines. Children, the elderly, individuals with a history of alcohol use disorder or a history of aggressive behavior and anger are at greater risk of developing paradoxical reactions to benzodiazepines. In September 2020, the U.S. Food and Drug Administration (FDA) required the boxed warning be updated for all benzodiazepine medicines to describe the risks of non-medical use, addiction, physical dependence, and withdrawal reactions consistently across all the medicines in the class.
=== Notable users === József Knoll, one of the developers of selegiline, began taking a low 1 mg daily dose of selegiline on January 1, 1989, at the age of 64. He reported in 2012 that this had continued for 22 years uninterrupted. Knoll stated that he had become so fascinated with the possible longevity-promoting effects of selegiline that he had decided to start taking it as a self-experiment. Knoll later died in 2018 at the age of 93. David Pearce, a British transhumanist philosopher, wrote his self-published book-length internet manifesto The Hedonistic Imperative six weeks after starting to take selegiline. Hamilton Morris, a psychoactive drug journalist and researcher, appears to have used selegiline. Sam Bankman-Fried, the founder and former CEO of the FTX cryptocurrency exchange, is known to have used selegiline for depression in the form of the Emsam patch for at least 5 to 10 years. He is also known to have simultaneously taken Adderall for treatment of attention deficit hyperactivity disorder (ADHD) and to have possessed non-pharmaceutical adrafinil, a prodrug of modafinil.
In 1956, Tsung-Dao Lee and Chen Ning Yang noticed that there was no evidence that parity was conserved in weak interactions, and so they postulated that this symmetry may not be preserved by the weak force. They sketched the design for an experiment for testing conservation of parity in the laboratory. Later that year, Chien-Shiung Wu and coworkers showed experimentally that an asymmetrical beta emission from 60Co proved that parity is not conserved in beta decay. This surprising result overturned long-held assumptions about parity and the weak force. In recognition of their theoretical work, Lee and Yang were awarded the Nobel Prize for Physics in 1957. However Wu, who was female, was not awarded the Nobel prize.
The last scene of the commercial showed Ivana asking for the last slice, to which Donald replied, "Actually, you're only entitled to half", a play on the couple's recent divorce. In 1995, Ringo Starr appeared in a Pizza Hut commercial that teased to a Beatles reunion, but featured three members of the Monkees. A commercial with Rush Limbaugh dates from the same year, in which he boasts "nobody is more right than me", yet he states for the first time he will do something wrong, which was to participate in Pizza Hut's then "eating pizza crust first" campaign regarding their stuffed crust pizzas. In 1999, the announcer says, "The best pizzas under one roof" in the Big New Yorker pizza commercial seen on the PlayStation Pizza Hut Demo Disc 1. Also, in 1999, the game Crazy Taxi for the Dreamcast featured Pizza Hut as one of the locations to which players were able to drive and drop off customers. However, in the game's 2010 re-release for Xbox Live and PlayStation Network, all of the product placement, including the Pizza Hut locations, were removed and replaced with generic locations. Early 2007 had Pizza Hut move into several more interactive ways of marketing to the consumer. Using mobile-phone SMS technology and their MyHut ordering site, they aired several television commercials (commencing just before the Super Bowl) containing hidden words that viewers could type into their phones to receive coupons.
=== Other research === In 2001, Sachs led a research team at UB which found that a chemical isolated from the venom of the Chilean tarantula could calm abnormal rhythms induced in rabbit hearts. Sachs said the result of this study showed that the protein could herald a new class of compounds that could be targeted at treating the causes, rather than the symptoms, of atrial fibrillation. Following this discovery, Sachs was named a UB Distinguished Professor and honored by Buffalo Business First for his invention. In 2013, Sachs and his research team identified that familial xerocytosis causes symptoms, such as the shortness of breath seen in anemic patients. This identification marked the first time defects in a mechanosensitive ion channel were implicated as the cause of a disease. Beyond spider venom, Sachs also conducted the first voltage clamp studies of isolated adult heart cells. He was also responsible for the first single-channel recording from tissue cultured cells.
Sources: en.wikipedia.org
In males, testicular enlargement is the first physical manifestation of puberty (and is termed gonadarche). Testes in prepubertal males change little in size from about 1 year of age to the onset of puberty, averaging about 2–3 cm in length and about 1.5–2 cm in width. The size of the testicles is among the parameters of the Tanner scale for male genitals, from stage I which represents a volume of less than 1.5 ml, to stage V which represents a testicular volume of greater than or equal to 20 ml. Testicular size reaches maximal adult size about 6 years after the onset of puberty. While 18–20 cm3 is an average adult size, there is wide variation in testicular size in the normal population. After the male's testicles have enlarged and developed for about one year, the length and then the breadth of the shaft of the penis will increase and the glans penis and corpora cavernosa will also start to enlarge to adult proportions.
RU-24213, also known as 3-hydroxy-N-propyl-N-(phenylethyl)phenethylamine, is a dopamine receptor agonist of the phenethylamine family related to dopamine. It is a selective dopamine D2-like receptor agonist. Subsequently, however, RU-24213 was found to also act as a potent κ-opioid receptor (KOR) antagonist. It led to the development of the diphenylethylamine series of KOR ligands. RU-24213 was first described in the scientific literature in 1978.
Pre-adipocytes are undifferentiated fibroblasts that can be stimulated to form adipocytes. Studies have shed light into potential molecular mechanisms in the fate determination of pre-adipocytes although the exact lineage of adipocyte is still unclear. The variation of body fat distribution resulting from normal growth is influenced by nutritional and hormonal status dependent on intrinsic differences in cells found in each adipose depot. Mesenchymal stem cells can differentiate into adipocytes, connective tissue, muscle or bone. The precursor of the adult cell is termed a lipoblast, and a tumor of this cell type is known as a lipoblastoma.
In very general terms, the viscous stresses in a fluid are defined as those resulting from the relative velocity of different fluid particles. As such, the viscous stresses must depend on spatial gradients of the flow velocity. If the velocity gradients are small, then to a first approximation the viscous stresses depend only on the first derivatives of the velocity. (For Newtonian fluids, this is also a linear dependence.) In Cartesian coordinates, the general relationship can then be written as
Sources: en.wikipedia.org
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
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.