cyclic heptapeptide comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-10-16. Numbers and descriptions here follow the published literature rather than marketing material.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Melanocortin receptor agonist |
| Molecular formula | C50H69N15O9 | Neutral form, mass near 1024.2 g/mol |
| Primary targets | MC1R, MC3R, MC4R, MC5R | Binding is non-selective across subtypes |
| Related compounds | Alpha-MSH, melanotan I, afamelanotide | Structurally or functionally related peptides |
| Common abbreviations | MT-II, MT-2 | Naming in the literature is not uniform |
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.
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.
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.
=== Post-translational modifications === C3orf62 possesses two post-translational modifications, both are phosphorylation sites with locations at amino acid 210 and 224. A natural variant is found at amino acid 110 (Glutamic acid (E)--> Lysine K). It appears as though C3orf62 may have a YinOYang site at residue 115, meaning that this Threonine residue is predicted to be O-GlycNAcylated as well as phosphorylated. This site may be reversibly and dynamically modified by O-GlcNAc or Phosphate groups at different times in the cell.
An aglycone (aglycon or genin) is the chemical compound remaining after the glycosyl group on a glycoside is replaced by a hydrogen atom. For example, the aglycone of a cardiac glycoside would be a steroid molecule. Samples of glycones and glycosides from limonoids can be simultaneously quantified through a high performance liquid chromatography (HPLC) method, where a binary solvent system and a diode array detector separate and detect them at a sensitivity of 0.25-0.50 μg. A study on molecular markers in human aortic endothelial cells published that urolithin A aglycone stopped cell migration but not monocyte adhesion, which is the initial step of atherosclerotic plaque formation. Another study exploring the benefits of extra virgin olive oil consumption in preventing age-related neurodegenerative diseases found oleuropein aglycone greatly increased the cognitive performance of mice. The aglycone-fed mice displayed strong autophagic reactions, mTOR regulation, and reduced plaque deposits and β-amyloid levels. Glucoside Media related to Glycoside aglycones at Wikimedia Commons
Moreover, the absolute uranium concentrations indicate that there was no contamination of the earthworm species studied." Though a more comprehensive assessment is possible, a 2011 update on a cancer scare regarding Italian soldiers who had served in the Balkans found lower than expected incidence rates for all cancers, a finding "consistent with lacking evidence of an increased cancer incidence among troops of other countries deployed in the areas of Iraq, Bosnia, and Kosovo, where armour-penetrating depleted uranium shells have been used." In 2018, Serbia set up a commission of inquiry into the consequences of the use of depleted uranium during the 1999 NATO bombing of Yugoslavia in southern Serbia and its link to the rise of diseases and tumors among citizens, particularly in young children born after 1999. Zoran Radovanovic, an epidemiologist and the chairman of the Serbian Medical Association's ethics committee, denied that there had been a rise in cancer cases in areas where bombings had taken place. He continued by saying that Serbians frequently worry about a cancer epidemic that does not exist. NATO has repeatedly claimed that depleted uranium found in the ammunition used in the 1999 bombardments cannot be linked to adverse health effects.
Sources: en.wikipedia.org
=== NEMS === Nanoelectromechanical systems (NEMS) can be designed and characterized by understanding the interaction and coupling between the mechanical, electrical, and the van der Waals energy domains. Quantum mechanical limit governed by Heisenberg uncertainty relation decides the ultimate precision of nanomechanical systems. Quantum squeezing can improve the precision by reducing quantum fluctuations in one desired amplitude of the two quadrature amplitudes. Traditional NEMS hardly achieve quantum squeezing due to their thickness limits. A scheme to obtain squeezed quantum states through typical experimental graphene NEMS structures taking advantages of its atomic scale thickness has been proposed.
=== Proximal TCR signaling === Phosphorylated ITAMs in the cytoplasmic tails of CD3 recruit protein tyrosine kinase Zap70 that can bind to the phosphorylated tyrosine residues with its SH2 domain. This brings Zap70 into close proximity to Lck which results to its phosphorylation and activation by Lck. Lck phosphorylates a number of different proteins in the TCR pathway. Once activated, Zap70 is able to phosphorylate multiple tyrosine residues of the transmembrane protein LAT. LAT is a scaffold protein associated with the membrane. It itself does not have any catalytic activity but it provides binding sites for signalling molecules via phosphorylated tyrosine residues. LAT associates with another scaffolding protein Slp-76 via the Grap2 adaptor protein, which provides additional binding sites. Together LAT and Slp-76 provide a platform for the recruitment of many downstream signaling molecules. By bringing these signalling molecules into close proximity, they can then be activated by Lck, Zap70 and other kinases. Therefore, the LAT/Slp76 complex act as a highly cooperative signalosome. Molecules that bind the LAT/Slp76 complex include: Phospholipase Cγ1 (PLCγ1), SOS via a Grb2 adaptor, Itk, Vav, Nck1 and Fyb.
== Works cited == Bertok L, Chow D (2005). Bertok L, Chow D (eds.). Natural Immunity. Vol. 5 (1st ed.). Elsevier Science. ISBN 978-0-44451-755-5. Breinstrup, Thomas (2006). "Un revolution in le mundo scientific" [A revolution in the scientific world]. Historia de interlingua (in Interlingua). Archived from the original on 2019-04-27. Retrieved 2025-01-14. Chung, Kyung Won (2005). Gross Anatomy (Board Review). Lippincott Williams & Wilkins. ISBN 0-7817-5309-0. Cook, Chad E. (2012). Orthopedic Manual Therapy: An Evidence Based Approach (2nd ed.). Upper Saddle River, NJ: Pearson Education. ISBN 978-0-13-802173-3. Breinstrup, Th.; Stenström, Ingvar; Olsson, Jesper, eds. (2007) [2001]. "Biographias: Ingvar Stenström". Interlingua (in Interlingua). Archived from the original on 2019-04-26. Retrieved 2025-01-15. Dinour, Lauren M. (2019). "Speaking Out on 'Breastfeeding' Terminology: Recommendations for Gender-Inclusive Language in Research and Reporting". Breastfeeding Medicine. 14 (8). Mary Ann Liebert: 523–532. doi:10.1089/bfm.2019.0110. PMID 31364867. Fielding, Lucie (2021). Trans Sex: Clinical Approaches to Trans Sexualities and Erotic Embodiments. New York: Routledge. ISBN 978-0-429-31829-0. Edwards, Heather. "Anatomy Talk". pp. 165–168. Gopsill, Frank Peter (1990). International languages: a matter for Interlingua. Sheffield, England: British Interlingua Society. ISBN 0-9511695-6-4. OCLC 27813762. Gopsill, Frank Peter (1994). Interlingua today: A course for beginners. Sheffield, England: British Interlingua Society. ISBN 978-1-898017-01-1.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide and a non-selective melanocortin receptor agonist. Structurally it is modelled on alpha-melanocyte-stimulating hormone, a peptide that occurs naturally in the body.
Activation of MC1R increases pigment synthesis independently of ultraviolet exposure, which is the mechanism usually cited for darkening without sun exposure. Ultraviolet light still influences skin response through separate biological pathways.
Because the peptide binds several melanocortin receptor subtypes, its effects are not confined to pigmentation. This complicates interpretation of both intended and unintended outcomes reported in studies.
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.