cyclic heptapeptide 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.
Updated 2026-07-28. Numbers and descriptions here follow the published literature rather than marketing material.
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 peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms differ |
| Molecular weight | Approximately 1024 g/mol | Calculated for the free base |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water and polar solvents | Poorly soluble in non-polar solvents |
| Typical storage | -20 degrees Celsius, dry, protected from light | Refers to the solid form |
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
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.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
==== Side reactions ==== When methionine is followed by serine or threonine, side reactions can occur that destroy the methionine without peptide bond cleavage. Normally, once the iminolactone is formed (refer to figure), water and acid can react with the imine to cleave the peptide bond, forming a homoserine lactone and new C-terminal peptide. However, if the adjacent amino acid to methionine has a hydroxyl or sulfhydryl group, this group can react with the imine to form a homoserine without peptide bond cleavage. These two cases are shown in the figure.
=== Truett's Grill === In 1996, the first Truett's Grill was opened in Morrow, Georgia. The second location opened in 2003 in McDonough, Georgia, and a third location opened in 2006 in Griffin, Georgia. Similar to the Chick-fil-A Dwarf Houses, these independently owned restaurants offer traditional, sit-down dining and expanded menu selections in a diner-themed restaurant. In 2017, Chick-fil-A demolished several Dwarf House locations to replace them with Truett's Grill locations.
Their mission, in their words "for the purpose of mutual aid in cases of sickness, accident and death of its members or their families". In 1923 it had 8,000 members in 60 subordinate societies; that year it had a capital of over $500,000, with a further $100,000 in sick benefit funds held by local societies. All policy decisions are determined by a "Central Society" made up of the officers, founders, and representatives of the subordinate lodges. A central society meets at stated intervals to elect officers to administer the group and make needed changes. Membership is open to men 18–50, of good moral character who have passed medical exams, regardless of religious or political creeds. Germania stated that it "is not a secret society. No pass-words or grips feature its work. In fact, any man is welcome to join its meetings." German Order of Harugari Greater Beneficial Union of Pittsburgh - Incorporated April 14, 1892 in Allegheny County, Pennsylvania, as the Deutscher Unter-stuetzungs-Bund, within a month had 243 members in 6 districts. Began the periodical, Union Reporter, the next year, now known as GBU Reporter. Rituals include the candidate signing an application and the president of the local lodge giving an address about the privileges of membership and how one should enter the lodge. Union claimed to be non-sectarian and had no secrets; open to all "well-meaning persons"; non-members accompanied by members allowed at meeting.
==== B. Aesthetics of the nose – nasal subunits and nasal segments ==== To plan, map, and execute the surgical correction of a nasal defect or deformity, the structure of the external nose is divided into nine aesthetic nasal subunits, and six aesthetic nasal segments, which provide the plastic surgeon with the measures for determining the size, extent, and topographic locale of the nasal defect or deformity.
Sources: en.wikipedia.org
== Social initiatives == IDLO is a long-time sponsor of various endurance and outdoor events, including Gorgany Race, the Night Chornohora Marathon, Stezhkamy Heroiv, and Spartan Race. The company also partners with educational camps organized by the Ukrainian national scouting organization Plast. Since 2020, IDLO has led an environmental program called “Leave No Trace”, to improve waste management in the Ukrainian mountains. The company accepts used doypacks for recycling, including those from other manufacturers. Following the full-scale Russian invasion of Ukraine in 2022, company co-founders Mykhaylo Temper and Serhii Andrieiev joined the Armed Forces of Ukraine.
1998 A record for the duration of life among males. The Danish-American Christian Mortensen lived 115 years and 252 days. 1998 Scientists managed to extend, in a laboratory environment, the life of normal human cells beyond the Hayflick limit using telomerase. 1999 Establishment of the Buck Institute for Research on Aging – the first institute originally established primarily to study intervention into the aging process. 1999 Sierra Sciences, a biotechnology company focused on aging research with the goal of curing human aging, was founded by William H. Andrews.
Albumin is a family of globular proteins, the most common of which are the serum albumins. All of the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins are commonly found in blood plasma and differ from other blood proteins in that they are not glycosylated. Substances containing albumins are called albuminoids. A number of blood transport proteins are evolutionarily related in the albumin family, including serum albumin, alpha-fetoprotein, vitamin D-binding protein and afamin. This family is only found in vertebrates. Albumins in a less strict sense can mean other proteins that coagulate under certain conditions. See § Other albumin types for lactalbumin, ovalbumin and plant "2S albumin".
Chip-on-board arrays Surface-mounted LEDs are frequently produced in chip on board (COB) arrays, allowing better heat dissipation than with a single LED of comparable luminous output. The LEDs can be arranged around a cylinder, and are called "corn cob lights" because of the rows of yellow LEDs.
=== Birds === Close to ninety percent of known avian species are monogamous, compared to five percent of known mammalian species. The majority of monogamous avians form long-term pair bonds which typically result in seasonal mating: these species breed with a single partner, raise their young, and then pair up with a new mate to repeat the cycle during the next season. Some avians such as swans, bald eagles, California condors, and the Atlantic Puffin are not only monogamous, but also form lifelong pair bonds. When discussing the social life of the bank swallow, Lipton and Barash state:
Sources: en.wikipedia.org
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==== Automation ==== An added benefit of using magnetic beads is that automated immunoprecipitation devices are becoming more readily available. These devices not only reduce the amount of work and time to perform an IP, but they can also be used for high-throughput applications.
=== Zinc and cadmium === Zinc and cadmium are both extracted by an ion exchange process, the N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) acts as a masking agent for the zinc and an extractant for the cadmium. In the modified Zincex process, zinc is separated from most divalent ions by solvent extraction. D2EHPA (Di (2) ethyl hexyl phosphoric acid) is used for this. A zinc ion replaces the proton from two D2EHPA molecules. To strip the zinc from the D2EHPA, sulfuric acid is used, at a concentration of above 170g/L (typically 240-265g/L).
Directed by Michael Proudfoot, made by Uden Associates 1 December A Setting for St Paul's, about a proposed office block development at Petershill, south of St Paul's Cathedral; Prince Charles' speech in October 1987; in 1956 architect William Holford, Baron Holford designed nearby buildings, built in the 1960s; Norman St John-Stevas, chairman of the Royal Fine Art Commission; William Whitfield; Christopher Mitchell on the planning committee of the City of London Corporation; James Tuckey and Rollin Schlicht, project managers of MEPC (Mitsubishi Estate); architects Ted Cullinan and Robin Nicholson; Hugh Pearman of the Sunday Times; George Cassidy; the architects visit Philip Whitbourn, chief architect at English Heritage; David Jenkin and Frank Duffy of DEGW; Martin Stancliffe, Surveyor of the Fabric of St Paul's Cathedral; painter Roger de Grey. Narrated by Penelope Wilton, produced by Mike Tomlinson and David Sharp, directed by Cathy Denford, made by Orlando Television Productions 8 December The Business of Bottled Water, the £300m bottled water industry.
Sources: en.wikipedia.org
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.
Both are synthetic analogues derived from the same parent hormone. Reference descriptions usually characterise afamelanotide as more selective for the MC1R subtype, whereas melanotan-2 is reported to interact with a wider range of melanocortin receptors.
Early studies explored melanocortin signalling and pigmentation, which later led to informal use of the label tanning peptide. That label is not a regulatory category and does not imply approved status for any purpose.
It is a synthetic cyclic heptapeptide and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.