If you have been reading about cyclic heptapeptide and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-11-22. Where a claim depends on a specific study, the study is described rather than over-claimed.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
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controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports.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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Alpha-MSH analogue with a lactam ring |
| Molecular formula | C50H69N15O9 | Commonly cited value for the neutral peptide |
| Molecular weight | 1024.18 g/mol | Calculated for the free molecule |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water, DMSO and ethanol | Dissolution in pure water is often slow |
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.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
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.
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.
The presence of radiologically opaque breast implants (either saline or silicone) might interfere with the radiographic sensitivity of the mammograph, that is, the image might not show any tumor(s) present. In this case, an Eklund view mammogram is required to ascertain either the presence or the absence of a cancerous tumor, wherein the breast implant is manually displaced against the chest wall and the breast is pulled forward, so that the mammograph can visualize a greater volume of the internal tissues; nonetheless, approximately one-third of the breast tissue remains inadequately visualized, resulting in an increased incidence of mammograms with false-negative results. The breast cancer studies Cancer in the Augmented Breast: Diagnosis and Prognosis (1993) and Breast Cancer after Augmentation Mammoplasty (2001) of women with breast implant prostheses reported no significant differences in disease-stage at the time of the diagnosis of cancer; prognoses are similar in both groups of women, with augmented patients at a lower risk for subsequent cancer recurrence or death. Conversely, the use of implants for breast reconstruction after breast cancer mastectomy appears to have no negative effect upon the incidence of cancer-related death. That patients with breast implants are more often diagnosed with palpable—but not larger—tumors indicates that equal-sized tumors might be more readily palpated in augmented patients, which might compensate for the impaired mammogram images.
When making transmission measurements, the spectrophotometer quantitatively compares the fraction of light that passes through a reference solution and a test solution, then electronically compares the intensities of the two signals and computes the percentage of transmission of the sample compared to the reference standard. For reflectance measurements, the spectrophotometer quantitatively compares the fraction of light that reflects from the reference and test samples. Light from the source lamp is passed through a monochromator, which diffracts the light into a "rainbow" of wavelengths through a rotating prism and outputs narrow bandwidths of this diffracted spectrum through a mechanical slit on the output side of the monochromator. These bandwidths are transmitted through the test sample. Then the photon flux density (watts per meter squared usually) of the transmitted or reflected light is measured with a photodiode, CCD or other light sensor. The transmittance or reflectance value for each wavelength of the test sample is then compared with the transmission or reflectance values from the reference sample. Most instruments will apply a logarithmic function to the linear transmittance ratio to calculate the 'absorbency' of the sample, a value which is proportional to the 'concentration' of the chemical being measured. In short, the sequence of events in a scanning spectrophotometer is as follows:
==== Obsessive–compulsive disorder ==== Psilocybin has been studied for the treatment of obsessive–compulsive disorder. It is formally under development for treatment of OCD by multiple pharmaceutical companies. These include candidates with the developmental code names SYNP-101 (Ceruvia Lifesciences) and MLS-101 (MycoMedica Life Sciences).
One-third of all indigenous inhabitants of Sub-Saharan Africa carry the allele, because, in areas where malaria is common, there is a survival value in carrying only a single sickle-cell allele (sickle cell trait). Those with only one of the two alleles of the sickle-cell disease are more resistant to malaria, since the infestation of the malaria Plasmodium is halted by the sickling of the cells that it infests. Antibiotic resistance: Practically all bacteria develop antibiotic resistance when exposed to antibiotics. In fact, bacterial populations already have such mutations that get selected under antibiotic selection. Obviously, such mutations are only beneficial for the bacteria but not for those infected. Lactase persistence. A mutation allowed humans to express the enzyme lactase after they are naturally weaned from breast milk, allowing adults to digest lactose, which is likely one of the most beneficial mutations in recent human evolution.
Sources: en.wikipedia.org
Numerous Jamaicans migrated mainly to the islands of San Andres and Providencia. A number of other Europeans and North Americans migrated to the country in the late 19th and early 20th centuries, including people from the former USSR during and after the Second World War. Many immigrant communities have settled on the Caribbean coast, in particular recent immigrants from the Middle East and Europe. Barranquilla (the largest city of the Colombian Caribbean) and other Caribbean cities have the largest populations of Lebanese, Palestinian, and other Levantines. There are also important communities of Romanis and Jews. There is a major migration trend of Venezuelans, due to the political and economic situation in Venezuela. In August 2019, Colombia offered citizenship to more than 24,000 children of Venezuelan refugees who were born in Colombia.
=== Further discoveries of the therapeutic potential of GLP-1 at University of Toronto === In 1987 Drucker returned to Toronto, taking on the position of Assistant Professor of Medicine at the University of Toronto and continuing his research on the glucagon-like peptides while also working as a physician. In 1996, Drucker was one of several investigators who demonstrated that GLP-1 reduced food intake in preclinical studies. Notably, the experiments in the Drucker lab demonstrated that this action of GLP-1 in the brain required the functional canonical GLP-1 receptor. Drucker, together with colleagues at Tufts Universities, filed multiple patents describing the utility of targeting the DPP-4 enzyme, and published studies demonstrating that genetic or chemical inactivation of DPP-4 prevented degradation of GLP-1 and GIP, supporting the development of DPP-4 inhibitors for the treatment of type 2 diabetes. In all, Drucker's discovery science has led to 33 issued US patents supporting translational drug development efforts in the field of peptide based therapeutics. Collectively, the body of work from multiple investigators and companies led to the development of two leading classes of diabetes medications: GLP-1 receptor agonists and DPP4 inhibitors.
=== Linus Pauling and the molecular clock hypothesis === Zuckerkandl's first project under Pauling (working with graduate student Richard T. Jones) was the application of new protein identification techniques—a combination of paper chromatography and electrophoresis that produced a two-dimensional pattern—to hemoglobin. The peptide fragments of hemoglobin samples from different species, partially broken apart by digestive enzymes, would produce unique patterns that could be used to estimate differences of protein structure. Zuckerkandl, Jones and Pauling published a comparison of several species' hemoglobin identification patterns in 1960, observing that the degree of dissimilarity of protein patterns corresponded approximately to the phylogenetic distance between source species. However, the method was not conducive to quantitative comparisons, so Zuckerkandl began working on the determination of the actual peptide sequence of the α and β chains of human and gorilla hemoglobin. In 1962, Pauling and Zuckerkandl published their first paper using the molecular clock concept (though not yet by that name). Like a number subsequent collaborative papers, it was not peer-reviewed—it was an invited paper in honor of Albert Szent-Györgyi—and they intentionally took the opportunity to "say something outrageous". The paper used the number of differences in the α and β chains of hemoglobin to infer the time since the last common ancestor for a number of species, calibrated based on paleontological evidence for humans and horses.
== James Bond films == The former War Office building served as the filming location for the MI6 headquarters (M's office) in five James Bond 007 movies. The landmark building appears in Octopussy (1983), A View to a Kill (1985), The Living Daylights (1986), Licence to Kill (1989), Skyfall (2012), and Spectre (2015).
==== Inhalation ==== Outdoor air may contain low levels of benzene from automobile service stations, wood smoke, tobacco smoke, the transfer of gasoline, exhaust from motor vehicles, and industrial emissions. About 50% of the entire nationwide (United States) exposure to benzene results from smoking tobacco or from exposure to tobacco smoke. After smoking 32 cigarettes per day, the smoker would take in about 1.8 mg of benzene. This amount is about 10 times the average daily intake of benzene by nonsmokers. Inhaled benzene is primarily expelled unchanged through exhalation. In a human study 16.4 to 41.6% of retained benzene was eliminated through the lungs within five to seven hours after a two- to three-hour exposure to 47 to 110 ppm and only 0.07 to 0.2% of the remaining benzene was excreted unchanged in the urine. After exposure to 63 to 405 mg/m3 of benzene for 1 to 5 hours, 51 to 87% was excreted in the urine as phenol over a period of 23 to 50 hours. In another human study, 30% of absorbed dermally applied benzene, which is primarily metabolized in the liver, was excreted as phenol in the urine.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide modelled on alpha-melanocyte-stimulating hormone. A lactam bridge links two side chains, forming a ring that stabilises the molecule against proteolysis. It belongs to the broader melanocortin peptide family.
No national medicines agency has approved melanotan-2 for clinical use. Afamelanotide, a related but distinct peptide, holds a marketing authorisation in the European Union for a rare photosensitivity disorder. Melanotan-2 itself is handled as a laboratory chemical.
Its broad activity across melanocortin receptors makes it a tool for probing pigmentation, appetite and vascular signalling. Early trials recorded skin darkening and other effects that were not the original focus of the work. Those observations generated hypotheses that later studies have examined.
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.