This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-01-13 and is reviewed periodically as new material appears.
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.
Analytical confirmation of identity relies on mass spectrometry, most often coupled to liquid chromatography. Reversed-phase high-performance liquid chromatography separates the peptide from related impurities and provides a purity estimate based on peak area. Electrospray ionization mass spectrometry then confirms the expected molecular mass, while tandem mass spectrometry can map the fragment sequence. For research-grade material, these two techniques together form the standard minimum. Purity figures reported by vendors are frequently not traceable to an independent laboratory.
Independent verification is central to quality control because the compound is not produced under pharmaceutical manufacturing standards. Third-party laboratories can measure purity, identity, residual solvents, and microbial contamination, though the scope of testing varies between services. Reported analyses of vendor samples have shown batch-to-batch variation in peptide content and the presence of truncated or oxidized species. How much of this variation reflects synthesis conditions versus storage and shipping is not well characterized. No harmonized reference standard exists for the material as sold.
| 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 |
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.
Verification of a purchased sample requires documentation linking a batch to a certificate of analysis, and that document should be read for the methods used rather than the headline purity figure. A single chromatographic percentage does not establish identity. Independent laboratories can perform identity and content assays, but no such test establishes that a product is suitable for human use. Claims about efficacy rest largely on small, early studies rather than on replicated controlled trials, and that gap remains open.
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
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.
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.
Routine characterisation relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, using a C18 column and a water-acetonitrile gradient containing trifluoroacetic acid. Electrospray ionisation mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidised by-products that co-elute poorly. Sequence and stereochemistry require additional work, such as peptide mapping or amino acid analysis, because a chromatographic purity figure alone does not distinguish a diastereomer from the target peptide. Independent testing of research-grade material frequently shows measured content below the stated label, so a certificate of analysis is best read together with the method that produced it.
Melanotan-2 is handled in the laboratory as a lyophilised powder that dissolves readily in water, dimethyl sulfoxide and dimethylformamide, with limited solubility in ethanol. Stock solutions prepared in an organic solvent often precipitate when diluted into aqueous buffer, so gradual dilution with mixing is standard practice. The peptide carries a tryptophan residue and a histidine residue, both sensitive to oxidation and to alkaline conditions. Working solutions are therefore kept near neutral to slightly acidic pH, protected from light, and consumed within the same working session whenever that is practical.
Solid peptide kept dry at minus twenty degrees Celsius, shielded from light and moisture, is generally considered stable for extended periods. Solutions are divided into single-use aliquots and held at minus twenty or minus eighty degrees Celsius, because repeated freeze-thaw cycles promote aggregation and loss of material to container surfaces. Hydrolysis of the backbone and oxidation of tryptophan are the principal degradation routes in aqueous solution, and both accelerate at ambient temperature. Hygroscopic uptake after a vial is opened can also shift the actual mass weighed, which affects any concentration calculated from it.
There are three main aims to agricultural advancement; increased production, improved conditions for agricultural workers and sustainability. GM crops contribute by improving harvests through reducing insect pressure, increasing nutrient value and tolerating different abiotic stresses. Despite this potential, as of 2018, the commercialized crops are limited mostly to cash crops like cotton, soybean, maize and canola and the vast majority of the introduced traits provide either herbicide tolerance or insect resistance. Soybeans accounted for half of all genetically modified crops planted in 2014. Adoption by farmers has been rapid, between 1996 and 2013, the total surface area of land cultivated with GM crops increased by a factor of 100. Geographically though the spread has been uneven, with strong growth in the Americas and parts of Asia and little in Europe and Africa. Its socioeconomic spread has been more even, with approximately 54% of worldwide GM crops grown in developing countries in 2013. Although doubts have been raised, most studies have found growing GM crops to be beneficial to farmers through decreased pesticide use as well as increased crop yield and farm profit. The majority of GM crops have been modified to be resistant to selected herbicides, usually a glyphosate or glufosinate based one. Genetically modified crops engineered to resist herbicides are now more available than conventionally bred resistant varieties; in the USA 93% of soybeans and most of the GM maize grown is glyphosate tolerant.
=== Aqueous state and biochemical work === In 1972, along with Raj V. Gupta, Redfield found a way to cancel out the overwhelming signature spectrum of H₂O in biological samples, which allowed the visualization of molecular biological structure in blood cells, nucleic acids, enzymes, and phospholipids.
=== EC 1.7.3 With oxygen as acceptor === EC 1.7.3.1: nitroalkane oxidase EC 1.7.3.2: acetylindoxyl oxidase EC 1.7.3.3: factor-independent urate hydroxylase EC 1.7.3.4: Now covered by EC 1.7.2.6, hydroxylamine dehydrogenase, and EC 1.7.3.6, hydroxylamine oxidase (cytochrome) EC 1.7.3.5: 3-aci-nitropropanoate oxidase EC 1.7.3.6: hydroxylamine oxidase (cytochrome)
== Criticism == Critics, such as Drug Free America Foundation and other members of network International Task Force on Strategic Drug Policy, state that a risk posed by harm reduction is by creating the perception that certain behaviours can be partaken of safely, such as illicit drug use, that it may lead to an increase in that behaviour by people who would otherwise be deterred. The signatories of the drug prohibitionist network International Task Force on Strategic Drug Policy stated that they oppose drug use harm reduction "...strategies as endpoints that promote the false notion that there are safe or responsible ways to use drugs. That is, strategies in which the primary goal is to enable drug users to maintain addictive, destructive, and compulsive behavior by misleading users about some drug risks while ignoring others." In 2008, the World Federation Against Drugs stated that while "...some organizations and local governments actively advocate the legalization of drugs and promote policies such as "harm reduction" that accept drug use and do not help people who use substances to become free from substance use. This undermines the international efforts to limit the supply of and demand for drugs." The Federation states that harm reduction efforts often end up being "drug legalization or other inappropriate relaxation efforts, a policy approach that violates the UN Conventions." Critics furthermore reject harm reduction measures for allegedly trying to establish certain forms of drug use as acceptable in society.
Sources: en.wikipedia.org
Fasting blood glucose test A method for finding out how much glucose (sugar) is in the blood, at a time when recent food intake does not affect glucose levels. The test can aid in diagnosis; a single reading of 126 mg/dL (7 mmol/L) is diagnostic except in newborns or pregnant women or in some unusual other conditions. A blood sample is often taken in a lab or doctor's office. The test is often done in the morning before the person has first eaten. The normal, nondiabetic range for fasting blood glucose is between 70 and 110 mg/dL (5 – 7 mmol/L), depending on the person (there is some variations between individuals), whether the blood is from a vein or a capillary, and depending on how the measurement is made (e.g., on whole blood or just the plasma). It can also be done by anyone with a blood glucose meter, proper supplies, and an understanding of how to test using them. Fats food substances which are the chief energy storage mechanism in organisms such as plants and animals. Fat molecules are composed of fatty acid chains attached to a glycerol backbone, usually in threes. Fats vary in the details of just which fatty acid variants are attached. Possibilities include saturated (the usual case in animal source fats), mono or poly unsaturated (from many plant oils, have one (mono) or more (poly) double carbon bonds in the fatty acid chain), and in where the double bond is (at the omega carbon in the 3 position, or the 6 position or ...). Some fats are required in the human diet, they are the 'essential oils'.
APHL works with public health partners to build the foundation for quality testing, comprehensive standards and integrated public health laboratory systems. One of the initiatives, the Laboratory System Improvement Program, provides individual assessments of public health laboratory systems that include engaging stakeholders for system improvement, performance, implementation of strategies and continual evaluation. APHL also collaborates on the National Laboratory System project to build a public-private network of laboratories nationwide. APHL monitors trends in public health laboratory diagnostics, personnel and infrastructure in order to create quality assurance standards. By using these data points to benchmark individual labs against national norms, APHL is able to home in on key issues and help raise the standard of laboratory systems. Member labs have access to research and survey data online, which enables them to leverage new information quickly to identify promising strategies and practices.
On March 28, 2013, a team of bioengineers from Stanford University led by Drew Endy announced that they had created the biological equivalent of a transistor, which they named a "transcriptor". That is, they created a three-terminal device with a logic system that can control other components. The transcriptor regulates the flow of RNA polymerase across a strand of DNA using special combinations of enzymes to control movement. According to project member Jerome Bonnet, "The choice of enzymes is important. We have been careful to select enzymes that function in bacteria, fungi, plants and animals, so that bio-computers can be engineered within a variety of organisms." Transcriptors can replicate traditional AND, OR, NOR, NAND, XOR, and XNOR gates with equivalents, which Endy dubbed "Boolean Integrase Logic (BIL) gates", in a single-layer process (i.e., without requiring multiple instances of the simpler gates to build up more complex ones). Like a traditional transistor, a transcriptor can amplify an input signal. A group of transcriptors can do almost any type of computing, including counting and comparison.
Although the 5f orbitals are unoccupied in an actinium atom, it can be used as a valence orbital in actinium complexes and hence it is generally considered the first 5f element by authors working on it. Ac3+ is the largest of all known tripositive ions and its first coordination sphere contains approximately 10.9 ± 0.5 water molecules.
=== Violent Crime and Law Enforcement Act === Clinton signed the 1994 Crime Bill, which was written by Senator Joe Biden of Delaware. It included 30 billion dollars' worth of federal anticrime funding. Specific to the war on drugs, Clinton included the three-strikes law, which required a mandatory life sentence for any felony violent crime conviction after two other prior convictions. Some social justice critics argue that the law disproportionately affected criminals in urban neighborhoods hurt by policing the war on drugs, rather than white-collar criminals. The bill also authorized $16 million in new funding for the development of federal prisons and state and local police forces. The Justice Policy Institute stated in 2008 that the administration's "tough on crime" policies caused larger increases in federal and state inmate populations than for any other president in American history. The act also saw the expansion of the federal death penalty. Sixty new capital punishment charges were created including non-homicidal narcotics offenses, drive-by shootings resulting in death, and carjackings relating to death. Between 1994 and 1999, nearly two thirds of people sentenced to the federal death penalty were black during Clinton's presidency, nearly seven times that of their representation in the US population. During his two terms, the federal prison population increased from 1.3 million to 2 million inmates. The law featured a provision that removed the approval of Pell Grants for low-income inmates in federal prison.
Sources: en.wikipedia.org
== American Red Cross Blood Bank == Drew's work led to his appointment as director of the first American Red Cross Blood Bank in February 1941. He also invented what would be later known as bloodmobiles, mobile donation stations that could collect the blood and refrigerate it; this allowed for greater mobility in terms of transportation and increased prospective donations. The blood bank supplied blood to the U.S. Army and Navy, who initially rejected the blood of African-Americans and later accepted it only if it were stored separately from that of white people. Drew objected to the exclusion of African-Americans' blood from plasma-supply networks, and in 1942 he resigned in protest.
A tablet of micronized progesterone which is marketed under the brand name Luteina is indicated for sublingual administration in addition to vaginal administration and is available in Poland and Ukraine. A progesterone suppository which is marketed under the brand name Cyclogest is indicated for rectal administration in addition to vaginal administration and is available in Cyprus, Hong Kong, India, Malaysia, Malta, Oman, Singapore, South Africa, Thailand, Tunisia, Turkey, the United Kingdom, and Vietnam. An aqueous solution of progesterone complexed with β-cyclodextrin for subcutaneous injection is marketed under the brand name Prolutex in the Czech Republic, Hungary, Italy, Poland, Portugal, Slovakia, Spain, and Switzerland. A non-systemic topical gel formulation of progesterone for local application to the breasts to treat breast pain is marketed under the brand name Progestogel and is available in Belgium, Bulgaria, Colombia, Ecuador, France, Georgia, Germany, Hong Kong, Lebanon, Peru, Romania, Russia, Serbia, Switzerland, Tunisia, Venezuela, and Vietnam. It was also formerly available in Italy, Portugal, and Spain, but was discontinued in these countries. A progesterone intrauterine device was previously marketed under the brand name Progestasert and was available in Canada, France, the United States, and possibly other countries, but was discontinued. Progesterone vaginal rings are marketed under the brand names Fertiring and Progering and are available in Chile, Ecuador, and Peru.
The names of those members of the Regular SAS who have died on duty were inscribed on the regimental clock tower at Stirling Lines. Originally funded by contributions of a day's pay by members of the regiment and a donation from Handley Page in memory of Cpl. R.K. Norry who was killed in a freefall parachuting accident, this was rebuilt at the new barracks at Credenhill. Those whose names are inscribed are said by surviving members to have "failed to beat the clock". At the suggestion of the then Commanding Officer, Dare Wilson, inscribed on the base of the clock is a verse from The Golden Journey to Samarkand by James Elroy Flecker:
=== Precursor to the antioxidant glutathione === Due to the ability of thiols to undergo redox reactions, cysteine and cysteinyl residues have antioxidant properties. Its antioxidant properties are typically expressed in the tripeptide glutathione, which occurs in humans and other organisms. The systemic availability of oral glutathione (GSH) is negligible; so it must be biosynthesized from its constituent amino acids, cysteine, glycine, and glutamic acid. While glutamic acid is usually sufficient because amino acid nitrogen is recycled through glutamate as an intermediary, dietary cysteine and glycine supplementation can improve synthesis of glutathione.
An isopeptide bond is a type of amide bond formed between a carboxyl group of one amino acid and an amino group of another. An isopeptide bond is the linkage between the side chain amino or carboxyl group of one amino acid to the α-carboxyl, α-amino group, or the side chain of another amino acid. In a typical peptide bond, also known as eupeptide bond, the amide bond always forms between the α-carboxyl group of one amino acid and the α-amino group of the second amino acid. Isopeptide bonds are rarer than regular peptide bonds. Isopeptide bonds lead to branching in the primary sequence of a protein. Proteins formed from normal peptide bonds typically have a linear primary sequence. Amide bonds, and thus isopeptide bonds, are stabilized by resonance (electron delocalization) between the carbonyl oxygen, the carbonyl carbon, and the nitrogen atom. The bond strength of an isopeptide bond is similar to that of a peptide due to the similar bonding type. The bond strength of a peptide bond is around 300 kJ/mol, or about 70 kcal/mol. Amino acids such as lysine, glutamic acid, glutamine, aspartic acid, and asparagine can form isopeptide bonds because they all contain an amino or carboxyl group on their side chain. For example, the formation of an isopeptide bond between the sidechains of lysine and glutamine is as follows:
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.
The lyophilized powder is generally held at minus twenty degrees Celsius or below, away from light and moisture. Reconstituted solutions are typically refrigerated and used quickly. These practices derive from general peptide handling rather than a formal stability study.