This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-07-22. Anything still debated is marked as such rather than presented as settled.
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.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
== Function == M-protein exhibits a different pattern of expression in cardiac and skeletal muscle, as well as fast- versus slow-skeletal muscle during development, suggesting different regulatory mechanisms for expression quantity and temporal appearance. In cardiac muscle, expression of M-protein continues to increase from neonatal to adult; however, in skeletal muscle, M-protein mRNA expression is biophasic. M-protein is initially present in both slow- and fast-skeletal muscle embryonic fibers, then M-protein is suppressed in slow fibers. The embryonic splice variant of myomesin, termed EH-myomesin, is expressed in a complementary pattern with M-protein during development in higher vertebrates. It was also shown that the mRNA expression of M-protein is exquisitely sensitive to thyroid hormone (T3); M-protein expression, but not MYOM1 or its variant, EH-myomesin, was rapidly reduced by T3 in vivo and in vitro. The M-protein promoter is responsive to T3, and was suggested to contain thyroid hormone response elements near the transcriptional start point. The giant protein titin, together with its associated proteins, interconnects the major structure of sarcomeres, the M bands and Z discs. The C-terminal end of the titin string extends into the M line, where it binds tightly to M-band constituents MYOM1 and M-protein, of apparent molecular masses of 190 kD and 165 kD, respectively.
Joy Stevenson Heeley, lately Revenue Officer, Board of Inland Revenue. Thomas William Heler, Member, Staffordshire Parish Councils Association. For services to Local Government. Mabel Evelyn Jeanette Henderson. For services to the Guide Association in Shetland. Joan Elizabeth Hetherington. For public service. Major John Wilfred Barratt Hext, , Voluntary Observer, Meteorological Office, Cumbria. Sheila Jean Hibbert. For services to Young People in London. Herbert Vincent Higgins. For services to the Retired and Senior Volunteer Programme. Eileen Jeanne Hodder. For services to the community in Richmond upon Thames, Surrey. Eileen Hodgkinson. For political and public service Marjone Hodgson. For services to the community in York. Mavis Ruth Hogg. For services to Lawn Tennis. Olive Holden. For services to the Cancer Relief Macmillan Fund in Perthshire. David George Holland, Senior Road Safety Officer, Durham County Council. For services to Road Safety. John Kenneth Hollis. For charitable services in Kent. Thomas Holmes, lately Assistant Director, Environmental Services, Trafford Metropolitan Borough Council. For services to the Environment. Albert Joseph Thomas Honey. For services to Animal Welfare in Oxfordshire. James William Hopkins, lately Manager, District Office, East Midlands Electricity plc. For services to the Electricity Industry. Robert Hopper, Road Worker, Highways Division, Northumberland Contracting. For services to Highways Maintenance. Olive Mary Hopton. For services to the community in Irlam, Manchester. Beve Hornsby. For services to People with Dyslexia.
The full-length version with an ATA start, which is transcribed at only 1% the level of other animals with the normal ATG start. A severely truncated version beginning at methionine-76 (Met-76). This version has no predicted signal peptide required for transport out of cytoplasm. A mass spectrometry study reported irisin levels ~3 ng/ml in human plasma, a level on par with other key human hormones, such as insulin. The same study reports that the main form in plasma is the ATA form, as expected for signal peptide presence. There is no comparable study of irisin levels in other animals. In a more recent study, Witmer et al. provide complementary genomic and molecular evidence to demonstrate that Fndc5 (irisin myokine precursor protein) is translated in humans and mice from an overlooked upstream ATG start codon. These findings lend further support to the likely existence of irisin in humans, revealing more plausible mechanisms of Fndc5 protein translation and processing as compared to possible expression from an inefficient mutated ATA start codon.
This victory contributed to a general Allied breakthrough in the area, and by 19 April, the 6th Division's armour was moving towards Lombardy and Venetia as part of the Fifth Army's vanguard. American and Polish troops entered Bologna on 21 April. The South Africans and Rhodesians advanced north-west towards the Panaro river. The Special Service Battalion's Rhodesian squadron, moving forward alongside the Cape Town Highlanders, and the Rhodesians of Prince Alfred's Guard took part in numerous engagements with the retreating German rearguard, and suffered several fatalities. The 6th Division crossed the Po near Ostiglia on 25 April and, after resupplying for a week, began a speedy advance towards Venice, aiming to cut off the retreat of elements of the German Fourteenth Army. The South Africans and Rhodesians advanced through Nogara and Cerea, crossed the Adige early on 29 April, and then made for Treviso, 19 kilometres (12 mi) north of Venice. The retreating German forces were by this time in such disarray that, during its advance from the Po, the 11th South African Armoured Brigade took prisoners from eight German divisions. On 30 April, the 6th Division joined up with British and American forces south of Treviso, and cut off the Germans' last escape route from Italy. The German forces in Italy surrendered unconditionally on 2 May 1945, while the 6th Division was moving north-west; at the time of the announcement it was near Milan.
=== Endocrine role === Adipocytes can synthesize estrogens from androgens, potentially being the reason why being underweight or overweight are risk factors for infertility. Additionally, adipocytes are responsible for the production of the hormone leptin. Leptin is important in regulation of appetite and acts as a satiety factor.
Sources: en.wikipedia.org
=== Endocrine === Dexamethasone is the treatment for the very rare disorder of glucocorticoid resistance. In adrenal insufficiency and Addison's disease, dexamethasone is prescribed when the patient does not respond well to prednisone or methylprednisolone. It can be used in congenital adrenal hyperplasia in older adolescents and adults to suppress adrenocorticotropic hormone (ACTH) production. It is typically given at night.
Sioux Nation of Indians and was involved in the Black Hills Land Claim John Lowenthal (1947), lawyer and documentary filmmaker known for his defense of Alger Hiss Norman Dorsen (1950), professor at the New York University School of Law and former president of the American Civil Liberties Union Robert O. Harris (1951), labor lawyer and chairman of the National Mediation Board Norman Marcus (1953), New York City Planning Commission general counsel and zoning expert Richard H. Stern (1953), attorney and law professor David Braun (1954), music industry lawyer, former president of PolyGram Records Alvin Hellerstein (1954), US federal judge Isaac Shapiro (1954), head of international practice at Skadden, Arps, Slate, Meagher & Flom, former president of Japan Society Clarence Benjamin Jones (1956), attorney and advisor to Martin Luther King Jr. Jerome H. Kern (1957), founder of Wachtell, Lipton, Rosen & Katz, former CEO of Playboy and Colorado Symphony Bernard Nussbaum (1958), White House counsel under Bill Clinton Ezra G. Levin (1959), lawyer, co-chair of international law firm Kramer Levin Naftalis & Frankel David G. Trager (1959), judge on the United States District Court for the Eastern District of New York Robert Abrams (1960), Bronx borough president and New York state attorney general Frank Tuerkheimer (1960), Watergate prosecutor and former U.S. attorney for the Western District of Wisconsin José A. Cabranes (1961), judge of the U.S. Court of Appeals; first Puerto Rican to sit in a U.S. District Court; current trustee of Columbia University Michael B.
In Africa, European colonial governments and European Christian missionaries criminalized and stigmatized the cultural practices of tattooing and scarification; consequently, the practices underwent decline, ended, or continued to be performed as acts of resistance. Among the ethnic groups in sub-Saharan Africa that traditionally practice scarification are the Gonja, Dagomba, Frafra, Mamprusi, Nanumba, Bali, Tɔfin, Bobo, Montol, Kofyar, Yoruba, and Tiv people of West Africa, and the Dinka, Nuer, Surma, Shilluk, Toposa, Moru, Bondei, Shambaa, Barabaig, and Maasai people of East Africa.
Adrenodoxin reductase: This enzyme is present ubiquitously in most organisms. It transfers two electrons from NADPH to FAD. In vertebrates, it serves as the first enzyme in the chain of mitochondrial P450 systems that synthesize steroid hormones.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
No. Melanotan-2 is manufactured synthetically. The naturally occurring peptide in the same family is alpha-melanocyte-stimulating hormone, which the body produces as part of normal endocrine and neural signalling.