The short version of cyclic heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-11-17 and is reviewed periodically as new material appears.
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 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 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.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Belongs to the melanocortin agonist family |
| Key substitutions | Nle4 and D-Phe7 | Improve resistance to enzymatic degradation |
| Molecular formula | C50H69N15O9 | Approximately 1024 g/mol |
| Regulatory status | Not approved as a medicine | Distributed as a research chemical |
| Common synonyms | Melanotan II, MT-II, MT-2 | Spelling varies across sources |
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.
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.
After the Rollercoaster Tour to support the album, the band concentrated on cracking the United States' market, with an appearance on David Letterman's show, and a tour as part of the Lollapalooza line-up, which William later described as "the worst experience of our lives," followed by their own headlining tour. In December 1992, the Reids again lost their rhythm section, with Ben Lurie returning and Steve Monti joining on drums. Another compilation was released in 1993, The Sound of Speed, before they returned to the studio to record their fifth album proper, Stoned & Dethroned which would see release in 1994, and featured guest appearances from Shane MacGowan and William's then-girlfriend Hope Sandoval. The album was originally planned as an acoustic album, but this idea was abandoned because, in Jim's words, "We couldn't do enough interesting things with acoustic guitars to make an album". In the 1995 EP released under American Records, a number of new works and B-sides were published which were later collected in the album Munki. After the release of the 1995 compilation Hate Rock 'N' Roll, the Mary Chain parted ways with Blanco y Negro, their record label of over a decade, and re-signed to their original label Creation Records, and Sub Pop in America. The band now included former Lush bassist Phil King. They then recorded 1998's Munki album, which would turn out to be their last before splitting the following year. Munki was commercially the least successful album the band released, peaking at number forty-seven in the UK Album Chart.
== Alternative for specimen transport == One common alternative to dry shippers is using dry ice. This method reduces package weight and costs since there's no need for return shipping, unlike with dry shippers. However, at -80 °C (176 °F), dry ice might not provide a temperature low enough for all specimens. For instance, while cryopreserved mouse spermatozoa can handle this temperature for short periods without losing their fertilization capacity, cryopreserved mouse embryos require colder environments, such as those below -150 °C (302 °F) in dry shippers, to maintain their quality. Another method is shipping freeze-dried samples at ambient temperatures, as seen with freeze-dried mouse spermatozoa. This can be more cost-effective, but many samples, when freeze-dried, experience a notable decline in quality, limiting its applicability.
At this point, it was known that organic molecules could be formed from inorganic starting materials, as Friedrich Wöhler had described the Wöhler synthesis of urea from ammonium cyanate in 1828. Several other early seminal works in the field of organic synthesis followed, including Alexander Butlerov's synthesis of sugars from formaldehyde and Adolph Strecker's synthesis of the amino acid alanine from acetaldehyde, ammonia, and hydrogen cyanide. In 1913, Walther Löb synthesized amino acids by exposing formamide to silent electric discharge, so scientists were beginning to produce the building blocks of life from simpler molecules, but these were not intended to simulate any prebiotic scheme or even considered relevant to origin of life questions. But the scientific literature of the early 20th century contained speculations on the origin of life. In 1903, physicist Svante Arrhenius hypothesized that the first microscopic forms of life, driven by the radiation pressure of stars, could have arrived on Earth from space in the panspermia hypothesis. In the 1920s, Leonard Troland wrote about a primordial enzyme that could have formed by chance in the primitive ocean and catalyzed reactions, and Hermann J. Muller suggested that the formation of a gene with catalytic and autoreplicative properties could have set evolution in motion. Around the same time, Alexander Oparin's and J. B. S.
Sources: en.wikipedia.org
Increases cardiac output Increases heart rate Increases ventilation rate Increases basal metabolic rate Potentiates the effects of catecholamines (i.e. increases sympathetic activity) Potentiates brain development Thickens endometrium in females Increases catabolism of proteins and carbohydrates
== Contraindications == In the case of oral minoxidil, absolute contraindications include pheochromocytoma, history of pericardial effusion or cardiac tamponade, history of pericarditis, history of pulmonary hypertension associated with mitral stenosis, hypersensitivity, and pregnancy and breastfeeding, whereas relative contraindications or precautions include hypotension (<90/60 mm hg), kidney impairment or failure, dialysis, history of heart attack, and history of tachycardia or other arrhythmia. Congestive heart failure is an absolute or relative contraindication according to different sources.
=== Ojibwe === The longest word in the Ojibwe language is miinibaashkiminasiganibiitoosijiganibadagwiingweshiganibakwezhigan (66 letters), meaning "blueberry pie". This literally translates to "blueberry cooked to jellied preserve that lies in layers in which the face is covered in bread".
Sources: en.wikipedia.org
== Biochemistry == Tetrodotoxin binds to what is known as site 1 of the fast voltage-gated sodium channel. Site 1 is located at the extracellular pore opening of the ion channel. Any molecule bound to this site will block sodium ions from going into the nerve cell through this channel (which is ultimately necessary for nerve conduction). Saxitoxin, neosaxitoxin, and several of the conotoxins also bind the same site. The use of this toxin as a biochemical probe has elucidated two distinct types of voltage-gated sodium channels (VGSCs) present in mammals: tetrodotoxin-sensitive voltage-gated sodium channels (TTX-s Na+ channels) and tetrodotoxin-resistant voltage-gated sodium channels (TTX-r Na+ channels). Tetrodotoxin inhibits TTX-s Na+ channels at concentrations of around 1–10 nM, whereas micromolar concentrations of tetrodotoxin are required to inhibit TTX-r Na+ channels. Nerve cells containing TTX-r Na+ channels are located primarily in cardiac tissue, while nerve cells containing TTX-s Na+ channels dominate the rest of the body. TTX and its analogs have historically been important agents for use as chemical tool compounds, for use in channel characterization and in fundamental studies of channel function. The prevalence of TTX-s Na+ channels in the central nervous system makes tetrodotoxin a valuable agent for the silencing of neural activity within a cell culture.
=== 6 October === At least 13 people were killed by RSF shelling in El Fasher. The RSF was accused of summarily executing three people at the Abu Talib school shelter in the Abu Shouk neighborhood of El Fasher. It was also accused of carrying out chemical attacks on the city using drones. The UNHRC voted 24–11 with 12 abstentions to extend the mandate of the Independent International Fact-Finding Mission investigating atrocities during the civil war until October 2026.
Diabetic retinopathy is an ocular pathology in diabetics which results in weakening of the retinal blood vessels. The initial nonproliferative stage is characterised by leaky vessels. As the vessel damage is repaired over time, they eventually become occluded, leading to proliferative diabetic retinopathy. The occluded capillaries create areas of ischemic retina and trigger the release of angiogenic growth factors. These growth factors stimulate the proliferation of new blood vessels from pre-existing retinal venules. It is the leading cause of blindness of working age adults.
Sources: en.wikipedia.org
It is a synthetic cyclic peptide designed as an analog of alpha-melanocyte-stimulating hormone. It acts on melanocortin receptors and is best known from research into pigmentation. It is not an approved pharmaceutical product.
No regulatory agency has approved it for any indication. It is encountered as a research chemical sold outside pharmaceutical supply chains. Products marketed this way are not subject to the manufacturing and labeling requirements that apply to approved drugs.
Reports describe increased skin pigmentation as well as side effects such as nausea, flushing, and changes to existing moles. Much of the evidence comes from small studies and case reports rather than large trials. The long-term safety profile is therefore uncertain.
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.