Heptapeptide is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-03-18. 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.
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.
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.
| 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 |
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.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
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.
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.
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.
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.
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 declaration's first safeguard clause referred to protecting the civil and religious rights of non-Jews in Palestine. The clause had been drafted together with the second safeguard by Leo Amery in consultation with Lord Milner, with the intention to "go a reasonable distance to meeting the objectors, both Jewish and pro-Arab, without impairing the substance of the proposed declaration". Arabs constituted around 90% of the population of Palestine, but – as stated by Ronald Storrs, Britain's Military Governor of Jerusalem between 1917 and 1920 – they were "not so much [named but] lumped together under the negative and humiliating definition of 'Non-Jewish Communities'". Additionally, there was no reference to protecting the political rights of this group, as there was regarding Jews in other countries. This lack of interest was frequently contrasted against the commitment to the Jewish community, with various terms used over subsequent years to regard the two obligations as linked. A heated question was whether the status of both groups had "equal weight", which the British government and the Permanent Mandates Commission held to be the case in the 1930 Passfield white paper. Balfour stated in February 1919 that Palestine was considered an exceptional case in which, referring to the local population, "we deliberately and rightly decline to accept the principle of self-determination," although he considered that the policy provided self-determination to Jews. Avi Shlaim considers this the declaration's "greatest contradiction".
== Clinical significance == The amount of expression of adiponectin has been observed to be related to diseases such as insulin resistance, obesity, and type 2 diabetes. Decreased amounts of the protein indicates that there is a higher probability of receiving said diseases. Because the GSTK1 is seen to play a role in the multimerization of adiponectin, this enzyme can regulate the concentration of adiponectin and thus enhance insulin sensitivity and protect against diabetes. Also, the GSTK1 gene is unregulated when it is inflicted with oxidative stress and are over expressed in many tumors leading to difficulties during cancer chemotherapy. Moreover, GSTK1 gene expression has been seen to increase significantly in correlation to drug resistance in tumor cells such as erythroleukemia and mammary adenocarcinoma suggesting that it, along with GSTP1 and GSTA4, could be responsible for the drug resistance. GSTK1 can also be a potential tool to help investigate cancer. Tyrosine phosphorylated proteins are responsible for many of the cell functions such as the cell’s growth, division, adhesion, and motility. These activities are also very related to cancer and thus studying this protein could allow access to information which could classify tumors for prognosis and prediction. Due to GSTK1’s C-terminal SH2 domain, tyrosine phosphorylated proteins can bind to it and allow for easier detection to which the protein can be studied.
The 3C-like protease (3CLpro) or main protease (Mpro), formally known as C30 endopeptidase, is the main protease found in coronaviruses. It cleaves the coronavirus polyprotein at eleven conserved sites. It is a cysteine protease and a member of the PA clan of proteases. It has a cysteine-histidine catalytic dyad at its active site and cleaves a Gln–(Ser/Ala/Gly) peptide bond. The Enzyme Commission refers to this family as SARS coronavirus main proteinase (Mpro; EC 3.4.22.69). The 3CL protease corresponds to coronavirus nonstructural protein 5 (nsp5). The "3C" in the common name refers to the 3C protease (3Cpro) which is a homologous protease found in picornaviruses.
=== First term (2018–2019) === Talarico launched his campaign for the Texas House shortly after incumbent state legislator Larry Gonzales chose not to run for reelection. He won the concurrent special and general elections against Republican nominee Cynthia Flores, garnering media attention for walking the full length of the district. He was sworn into the Texas House of Representatives on November 20, 2018, and appointed to the Public Education and Juvenile Justice Committees. In the 86th Texas Legislature, Talarico filed the Whole Student Agenda, a 24-bill public education policy legislative package. The legislature passed two bills from this list. The first, HB 3012, required that students suspended from school have an alternative means to receive coursework. HB 455, also sponsored by Talarico, was written to provide a standardized school recess policy. Governor Greg Abbott vetoed the bill.
Sources: en.wikipedia.org
Ketones in the urine or blood, as detected by urine strips or a blood ketone testing meter, may indicate the beginning of diabetic ketoacidosis (DKA), a dangerous and often quickly fatal condition caused by high glucose levels (hyperglycemia) and low insulin levels combined with certain other systemic stresses. DKA can be arrested if caught quickly. Ketones are produced by the liver as part of fat metabolism and are normally not found in sufficient quantity to be measured in the urine or blood of non-diabetics or well-controlled diabetics. The body normally uses glucose as its fuel and is able to do so with sufficient insulin levels. When glucose is not available as an energy source because of untreated or poorly treated diabetes and some other unrelated medical conditions, it begins to use fat for energy instead. The result of the body turning to using fat instead of glucose for energy means ketone production that is measurable when testing either urine or blood for them. Ketone problems that are more serious than the "trace or slight" range need immediate medical attention; they cannot be treated at home. Veterinary care for ketosis/ketoacidosis can involve intravenous (IV) fluids to counter dehydration, when necessary, to replace depleted electrolytes, intravenous or intramuscular short-acting insulin to lower blood glucose levels, and measured amounts of glucose or force feeding, to bring the metabolism back to using glucose instead of fat as its source of energy.
==== Low-level laser therapy (LLLT) ==== Low-level laser therapy or photobiomodulation is also referred to as red light therapy and cold laser therapy. It is a non-invasive treatment option. LLLT is shown to increase hair density and growth in both genders. The types of devices (hat, comb, helmet) and duration did not alter the effectiveness, with more emphasis to be placed on lasers compared to LEDs. Ultraviolet and infrared light are more effective for alopecia areata, while red light and infrared light is more effective for androgenetic alopecia. Medical reviews suggest that LLLT is as effective or potentially more than other non invasive and traditional therapies like minoxidil and finasteride but further studies such as RCTs, long term follow up studies, and larger double blinded trials need to be conducted to confirm the initial findings.
A study by Latinobarómetro in 2023 estimates that 50.3% of the population are Mestizo, 26.4% are White, 9.5% are Indigenous, 9.0% are Black, 4.4% are Mulatto, and 0.4% are Asian, these estimates would equate to around 26 million people being Mestizo, 14 million being White, 5 million being Indigenous, 5 million being Black, 2 million being Mulatto, and 200k being Asian.
== Deaths == 3 January – Derek Draper, 56, lobbyist and political adviser. 15 January – James Masih Shera, 77, Pakistani-born British politician and educationist. 17 January – Sir Tony Lloyd, 73, British politician, MP (1983–2012, since 2017) and mayor of Greater Manchester (2015–2017), leukemia. 19 January – Sir Graham Bright, 81, British politician, MP (1979–1997) and Cambridgeshire police and crime commissioner (2012–2016). 20 January – John Tomlinson, Baron Tomlinson, 84, British politician, MP (1974–1979) and MEP (1984–1999). 6 February – Shreela Flather, Baroness Flather, 89, British-Indian politician, Life peer (since 1990). 23 February – Ronnie Campbell, 80, British politician, MP (1987–2019). 25 February – Patrick Cormack, Baron Cormack, 84, British politician, MP (1970–2010) and member of the House of Lords (since 2010). (death announced on this date) 26 February – Jacob Rothschild, 4th Baron Rothschild, 87, British investment banker and peer, member of the House of Lords (1991–1999). 29 February – Ruth Henig, Baroness Henig, 80, historian and politician, member of the House of Lords (since 2004), Deputy Speaker of the House of Lords (since 2018). 8 March – Tommy McAvoy, Baron McAvoy, 80, British politician, MP (1987–2010) and member of the House of Lords (since 2010). (death announced on this date) 6 April – Doug Hoyle, Baron Hoyle, 98, British politician, MP (1974–1979, 1981–1983) and member of the House of Lords (1997–2023). 10 April – Richard Rosser, Baron Rosser, 79, British trade unionist and politician, member of the House of Lords (since 2004).
== Bibliography == Bagnall, K. W. (1962) [1962]. "The Chemistry of Polonium". Advances in Inorganic Chemistry and Radiochemistry. Vol. 4. New York: Academic Press. pp. 197–226. doi:10.1016/S0065-2792(08)60268-X. ISBN 978-0-12-023604-6. Retrieved 14 June 2012. {{cite book}}: ISBN / Date incompatibility (help) Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth–Heinemann. ISBN 978-0080379418.
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.
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.