If you have been reading about melanocortin 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 2026-07-21. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
The peer-reviewed record is dominated by small early-phase studies, case reports and pharmacovigilance summaries rather than large randomised trials. Papers typically examine tanning response, receptor selectivity or patterns of reported adverse events. Many note that participants obtained the peptide outside a clinical setting, which limits verification of composition and administered amount. Reported events vary widely, and causality is frequently unclear because the identity and purity of self-sourced material are unknown. Open questions include whether repeated melanocortin receptor stimulation produces cumulative effects, and how often label claims match actual content.
Identification in laboratories relies on reversed-phase liquid chromatography coupled with tandem mass spectrometry, with product-ion spectra compared against a certified reference standard. High-resolution mass spectrometry supplies accurate mass confirmation, and peptide mapping after enzymatic digestion separates melanotan II from closely related analogues. Quantitation of seized material is complicated by unknown counter-ions and residual trifluoroacetate left from purification. Immunoassays raised against alpha-melanocyte-stimulating hormone can cross-react, so chromatographic confirmation is normally required. Urinary detection windows are short, and reported limits of detection differ substantially between laboratories.
| 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 |
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
Melanotan II is a synthetic cyclic heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, corresponding to a molecular formula of C50H69N15O9 and a monoisotopic mass near 1024 daltons. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, a peptide hormone produced by cleavage of proopiomelanocortin. A lactam bridge between the aspartate and lysine side chains closes the ring, and the C-terminal amide removes a free carboxyl group. Both modifications increase resistance to enzymatic degradation compared with the linear parent hormone. Four substitutions distinguish it from afamelanotide, the linear analogue studied under the name melanotan I.
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
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.
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 club ended 2012 in 11th place. A spate of soft-tissue injuries accompanied the decline, as did noticeable fatigue in other players, leading to criticism of the club's fitness and conditioning coach Dean Robinson and, indirectly, Hird and his assistant Thompson for having overseen Robinson's program. The 2013 season was initially a good one for Hird and the football club, during which the team was second on the AFL ladder with a 13–3 win–loss record after 17 rounds. However, internal pressure on the club finally took its toll on the players and coach when the AFL banned Essendon from participating in the 2013 finals series. The club on-field performances fell away and lost five of their last six games. In August 2013, he was suspended from coaching for 12 months when he was charged by the AFL with conduct prejudicing the game in relation to his role in the Essendon Football Club supplements controversy. Banned from coaching in 2014, Hird spent several months living in France attending an exclusive business school, INSEAD, near Paris. He returned to the club following the 2014 season. Shortly after returning from his suspension, on 2 October 2014, it was reported that Hird was to be sacked by Essendon due to his determination to lodge an appeal against the Federal Court decision handed down the previous month when the club had chosen not to.
== Applications of LTLs in medicine == Ligand-targeted liposomes are used for a variety of applications depending on the liposome, ligand, and liposome contents. Ligand-targeted liposomes can be used for diagnostics through imaging. The liposomes can contain imaging agents to aid in visualization such as fluorescent dyes, labeling probes, and contrast agents. Commonly, a radioactive gamma-emitter, fluorescent marker, or magnetic resonance imaging (MRI) agent is encapsulated in the liposome for this application. The active targeting mechanism of LTLs allows the target tissue to retain the imaging agent while the remaining agent is cleared from circulation. The ligand-targeted liposomes increase the specificity and sensitivity of the images taken through positron emission tomography (PET), single-photon emission computed tomography (SPECT), and MRI techniques through the ligand localization to receptors of interest. Biotinylated liposomes containing [67Ga] coupled with a later injection of avidin have been shown to reduce background signal and produce the needed contrast for imaging while reducing the circulation time of radioactive imaging agent. Molecular imaging of processes over time in vivo is also made possible using ligand-targeted nanoparticles. As of 2015, many ligand-targeted imaging agents such as MIP-1404, MIP-1405, MIP-1072, MIP-109, and 18F-DCFBC were undergoing clinical trials. The ability of a liposome to encapsulate these imaging agents and deliver them to specific regions through ligand targeting is helpful for precision detection.
Active esters are prominent in biochemistry. Glutamine synthetase is an enzyme that forms an active ester from the terminal carboxylate of glutamic acid. This activation, imparted by phosphorylation, facilitates the conversion of the carboxylate to an amide called glutamine.
== Presentation == Phenotypes of spondyloepiphyseal dysplasia congenita vary. Defining features include short stature, with a short spine and neck, a barrel chest, and normal-sized hands and feet. This type of dwarfism is characterized by a normal spinal column length relative to the femur bone. Adult height ranges from 0.9 meters (35 inches) to just over 1.4 meters (55 inches). Curvature of the spine (such as kyphoscoliosis and lordosis) progresses during childhood and can cause problems with breathing. Changes in the spinal bones (vertebrae) in the neck may also increase the risk of spinal cord damage. Other skeletal signs include flattened vertebrae (platyspondyly), a hip joint deformity in which the upper leg bones turn inward (coxa vara), and an inward- and downward-turning foot (called clubfoot). Decreased joint mobility and arthritis often develop early in life. Medical texts often state a mild and variable change to facial features, including cheekbones close to the nose appearing flattened, although this appears to be unfounded. Some infants are born with a cleft palate. Severe nearsightedness (high myopia) is sometimes present, as are other eye problems that can affect vision such as detached retinas. About one-quarter of people with this condition have mild to moderate hearing loss.
Sources: en.wikipedia.org
== Medical uses == Lisinopril is typically used for the treatment of high blood pressure, congestive heart failure, and diabetic nephropathy and after acute myocardial infarction (heart attack). Lisinopril is part of the ACE inhibitors drug class. Lisinopril is indicated for the treatment of hypertension, adjunctive therapy for heart failure, and acute myocardial infarction.
=== Aryl cyclooctynes === Fusion of a cyclooctyne to two aryl rings increases the reaction rate, and the cyclooctyne reagents of the Bertozzi group proceeded through a series of fusions that sought to increase the ring strain even further. DIBO (dibenzo cyclooctyne) was developed as a precursor to BARAC (biarylazacyclooctynone), although calculations had predicted that a single fused aryl ring would be optimal. Attempts to make a difluoro benzo cyclooctyne (DIFBO) were unsuccessful due to the instability of the compound. The reason for the instability of DIFBO is that it is so reactive that it spontaneously trimerizes to form two asymmetric products that can be characterized by X-ray crystallography. To stabilize the DIFBO, it is trapped by forming a stable inclusion complex with β-cyclodextrin in aqueous media. This complex, formed with the β-cyclodextrin, can then be stored as a lyophilized powder. To obtain the free DIFBO, the lyophilized powder is dissociated with organic solvents to produce the free DIFBO for in situ kinetic and spectroscopic analysis. Problems with DIFO with in vivo mouse studies illustrate the difficulty of producing bioorthogonal reactions.
Chiang's general He Yingqin then proposed building a highway from Kangding to Xining through Yushu, but Liu once again blocked Nationalist attempts to introduce its soldiers in Xikang. Kim Hee-shin argues that Liu, in his dealings with various political factions, was mainly driven by political survival, with ideology playing little to no role in his considerations. This meant that although Xikang cooperated with the central government, he maintained ties with anti-Chiang factions and refused to let Nationalist garrisons into his province. An attempt by the Nationalist official H. H. Kung to more closely oversee Xikang's affairs in 1939 ended in failure after the representative he sent, Peter Goullart, was placed under house arrest by Liu's forces. To prevent the CC Clique from taking control of his province, Liu used his position as head of the provincial government to block their influence.
=== Locating trials === Depending on the kind of participants required, sponsors of clinical trials, or contract research organizations working on their behalf, try to find sites with qualified personnel as well as access to people who could participate in the trial. Working with those sites, they may use various recruitment strategies, including patient databases, newspaper and radio advertisements, flyers, posters in places the patients might go (such as doctor's offices), and personal recruitment of trial participants by investigators. Volunteers may search directly to locate trials using a registry run by the U.S. National Institutes of Health and National Library of Medicine to identify studies that are currently recruiting participants, offering simplified navigation and real-time enrollment trial information. Software exists to enable clinicians to find trial options for a possible participant based on genomic data for people with cancer.
Klaus H. Hofmann (February 21, 1911 – December 25, 1995) was an American biological chemist and medical researcher. The New York Times called Hofmann an "expert on synthesis of body compounds". His career was highlighted by synthesis of a prototype birth control pill, isolation and structural characterization of biotin (vitamin H), determination of the lysine specificity of the pancreatic protease trypsin (an attribute that made it the enzyme of first choice in protein sequence determinations), the first chemical synthesis of a fully biologically-active portion of the peptide hormone (adrenocorticotopic hormone - ACTH), and structure-function studies on ribonuclease (RNase).
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.
Regulatory treatment varies by country. In the United States, the European Union and Australia it is an unapproved drug and its sale is restricted, while some other jurisdictions list it as prescription-only or controlled. The applicable rules depend on the country of import.