This is a working overview of alpha-MSH analogue, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-05-16. Anything still debated is marked as such rather than presented as settled.
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.
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.
Solid peptide material is generally stable when kept cold and dry. Common practice is storage at -20 degrees Celsius or lower, with desiccant and protection from light. Repeated freeze-thaw cycles and exposure to moisture are associated with degradation, aggregation, or loss of material. Once dissolved, stability depends on solvent, concentration, and temperature, and solutions are usually treated as short-lived unless stability data support longer periods. Handling notes typically emphasise minimising time at ambient temperature.
Identity and purity are assessed with chromatographic and mass spectrometric techniques. Reversed-phase high-performance liquid chromatography separates the target peptide from related impurities and degradation products, and the resulting retention time is compared against a reference standard. Mass spectrometry, often coupled to liquid chromatography, confirms molecular mass. Amino acid analysis or peptide mapping can provide additional sequence-level confirmation when required. Results are only as reliable as the reference materials used alongside them.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms add to total mass |
| Molecular mass | About 1024 daltons | Calculated for the free base |
| Structural class | Cyclic heptapeptide | Contains D-phenylalanine and norleucine |
| Parent hormone | Alpha-melanocyte-stimulating hormone | Endogenous tridecapeptide of 13 residues |
| Receptor profile | Non-selective melanocortin agonist | Interacts with MC1R, MC3R, MC4R and MC5R |
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.
Identity testing for a synthetic peptide relies on several complementary methods. Reversed-phase high-performance liquid chromatography separates the target from related impurities and reports purity as a percentage of total peak area. Mass spectrometry confirms molecular mass and can reveal deletions or truncations. Amino acid analysis and peptide mapping provide sequence-level confirmation, while counter-ion content and residual solvents are measured separately. A purity figure alone does not establish identity, so a complete dataset combines chromatographic and spectrometric evidence.
Lyophilized peptide powder is generally stored frozen, protected from light and moisture. Tryptophan residues are susceptible to oxidation, and the lactam bridge can hydrolyze under strongly acidic or basic conditions. Solutions prepared for laboratory work degrade faster than dry powder, and repeated freeze-thaw cycles accelerate loss. Common practice is to aliquot solutions before freezing and to avoid alkaline buffers. Reported stability windows vary with concentration, buffer, and temperature, so exact shelf lives are method-specific rather than universal.
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.
==== On Natural Amino Acids ==== Rh-catalyzed Trp and Cys alkylation Using in situ generated RhII-carbenoid by activation of vinyl-substituted diazo compounds with Rh2(OAc)4, tryptophans and cysteines were shown to be selectively alkylated in aqueous media. However, this method is limited to surface tryptophans and cysteines possibly because of steric constraints.
A continuity equation or transport equation is an equation that describes the transport of some quantity. It is particularly simple and powerful when applied to a conserved quantity, but it can be generalized to apply to any extensive quantity. Since mass, energy, momentum, electric charge and other natural quantities are conserved under their respective appropriate conditions, a variety of physical phenomena may be described using continuity equations. Continuity equations are a stronger, local form of conservation laws. For example, a weak version of the law of conservation of energy states that energy can neither be created nor destroyed—i.e., the total amount of energy in the universe is fixed. This statement does not rule out the possibility that a quantity of energy could disappear from one point while simultaneously appearing at another point. A stronger statement is that energy is locally conserved: energy can neither be created nor destroyed, nor can it "teleport" from one place to another—it can only move by a continuous flow. A continuity equation is the mathematical way to express this kind of statement. For example, the continuity equation for electric charge states that the amount of electric charge in any volume of space can only change by the amount of electric current flowing into or out of that volume through its boundaries.
Essendon Hall of Fame Legends (year inducted): Bill Brew (2013), Bill Busbridge (1996), Jack Clarke (1996), John Coleman (1996), Bill Cookson (1996), Wally Crichton (2010), Terry Daniher (1996), Barry Davis (2006), Ron Evans (2012), Tom Fitzmaurice (1996), Ken Fraser (1996), Allan Hird Sr (1996), James Hird (2011), Harry Hunter (2015), Bill Hutchison (1996), Matthew Lloyd (2013), Simon Madden (1996), Alex McCracken (1996), Michael Long (2010), Howard Okey (2012), Frank Reid (1996), Dick Reynolds (1996), Greg Sewell (2009), Kevin Sheedy (2008), Albert Thurgood (1996), Tim Watson (1998), Neale Daniher* (2018), Dustin Fletcher*, Dr Bruce Reid* (2014), Gavin Wanganeen* *denotes recent elevation to Legend status Essendon Hall of Fame members (year inducted): Noel Allanson (2015), Fred Baring (2013), John Birt (2010), Reg Burgess (2015), Wally Buttsworth (2010), Barry Capuano (2014), Kevin Egan (2015), Alec Epis (2014), Ken Fletcher (2011), Keith Forbes (2010), Garry Foulds (2010), Darryl Gerlach (2013), Mark Harvey (2014), Bruce Heymanson (2013), Jack Jones (2012), Ron Kirwan (2016), Harold Lambert (2018), Scott Lucas (2013), Roy McConnell (2013), Don McKenzie (2010), Roger Merrett (2018), Joe Misiti (2012), Hugh Mitchell (2012), Graham Moss (2012), Gary O'Donnell (2014), Dr Ian Reynolds (2018), Paul Salmon (2012), David Shaw (2011), Arthur Showers (2010), George Stuckey (2010), Hugh Torney (2011), Paul Vander Haar (2015)
Sources: en.wikipedia.org
Covalent interactions are those with the strongest association and are formed by disulphide bonds or electron sharing. While rare, these interactions are determinant in some posttranslational modifications, as ubiquitination and SUMOylation. Non-covalent bonds are usually established during transient interactions by the combination of weaker bonds, such as hydrogen bonds, ionic interactions, Van der Waals forces, or hydrophobic bonds.
== Mechanical properties == The ongoing research has shown that mechanical properties can vary significantly in nanomaterials compared to bulk material. Nanomaterials have substantial mechanical properties due to the volume, surface, and quantum effects of nanoparticles. This is observed when the nanoparticles are added to common bulk material, the nanomaterial refines the grain and forms intergranular and intragranular structures which improve the grain boundaries and therefore the mechanical properties of the materials. Grain boundary refinements provide strengthening by increasing the stress required to cause intergranular or transgranular fractures. A common example where this can be observed is the addition of nano Silica to cement, which improves the tensile strength, compressive strength, and bending strength by the mechanisms just mentioned. The understanding of these properties will enhance the use of nanoparticles in novel applications in various fields such as surface engineering, tribology, nanomanufacturing, and nanofabrication. Techniques used: Steinitz in 1943 used the micro-indentation technique to test the hardness of microparticles, and now nanoindentation has been employed to measure elastic properties of particles at about 5-micron level. These protocols are frequently used to calculate the mechanical characteristics of nanoparticles via atomic force microscopy (AFM) techniques. To measure the elastic modulus; indentation data is obtained via AFM force-displacement curves being converted to force-indentation curves.
=== Da–Di === Jeff Dahn (born 1957), Canadian materials chemist noted for significant contributions to lithium-ion batteries John Dalton (1766–1844), British chemist, physicist and meteorologist, whose work laid the foundations of modern atomic theory and stoichiometric chemistry Marie Maynard Daly (1921–2003), American biochemist who studied the chemistry of histones, protein synthesis, the relationships between cholesterol and hypertension, and uptake of creatine by muscle cells Carl Peter Henrik Dam (1895–1976), Danish biochemist, winner of the 1943 Nobel Prize in Physiology or Medicine for discovering vitamin K and its role in human physiology Samuel J. Danishefsky (born 1936), American organic chemist, natural product total synthesis, 1995/6 Wolf Prize in Chemistry Raymond Davis, Jr.
Sources: en.wikipedia.org
=== COVID-19 pandemic === On 20 January 2020, Xi commented for the first time on the emerging COVID-19 pandemic in Wuhan, and ordered "efforts to curb the spread" of the virus. He gave premier Li Keqiang some responsibility over the COVID-19 response, in what has been suggested by The Wall Street Journal was an attempt to potentially insulate himself from criticism if the response failed. The government initially responded to the pandemic with a lockdown and censorship, with the initial response causing widespread backlash within China. Xi met with Tedros Adhanom Ghebreyesus, the director-general of the World Health Organization (WHO), on 28 January. Der Spiegel reported that in January 2020 Xi pressured Tedros Adhanom to hold off on issuing a global warning about the outbreak of COVID-19 and hold back information on human-to-human transmission of the virus, allegations denied by the WHO. On 5 February, Xi met with Cambodian prime minister Hun Sen in Beijing, the first foreign leader allowed into China since the outbreak. After the COVID-19 outbreak got under control in Wuhan, Xi visited the city on 10 March. After getting the outbreak in Wuhan under control, Xi has favoured what has officially been termed "dynamic zero-COVID policy" that aims to control and suppress the virus as much as possible within the country's borders. This has involved local lockdowns and mass-testing.
== Relative bioavailability and bioequivalence == In pharmacology, relative bioavailability measures the bioavailability (estimated as the AUC) of a formulation (A) of a certain drug when compared with another formulation (B) of the same drug, usually an established standard, or through administration via a different route. When the standard consists of intravenously administered drug, this is known as absolute bioavailability (see above).
characterizes the potential for initial spread of an infectious person in a naive population, assuming the change in the susceptible population is negligible during the initial spread. A linear system of ODEs can always be described by a matrix. So, the next step is to construct a linear positive operator that provides the next generation of infected people when applied to the present generation. Note that this operator (matrix) is responsible for the number of infected people, not all the compartments. Iteration of this operator describes the initial progression of infection within the heterogeneous population. So comparing the spectral radius of this operator to unity determines whether the generations of infected people grow or not.
Sources: en.wikipedia.org
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.
Melanotan-1, also called afamelanotide, is a linear analogue with greater selectivity for MC1R and has received approval in some jurisdictions for a specific photosensitivity disorder. Melanotan-2 is cyclic, less selective, and reaches central receptors more readily. The two are often confused in online discussion despite different pharmacology and regulatory status.
Alpha-MSH is an endogenous tridecapeptide derived from pro-opiomelanocortin. Melanotan-2 reproduces its core receptor-binding sequence inside a shortened, stabilised ring. The result is a molecule with a longer effective half-life and higher potency than the parent hormone.
Laboratory confirmation typically combines retention time matching on a chromatographic system with mass measurement. A reference standard of known identity is needed for a meaningful comparison. Sequence-level techniques can add further confirmation.