If you have been reading about cyclic heptapeptide 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.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Lyophilised melanotan-2 is comparatively robust when kept dry, cold and dark, and a desiccated powder stored at minus twenty degrees Celsius or below is generally expected to retain its chemical integrity for extended periods. In solution the peptide is far less stable, with degradation proceeding through oxidation of tryptophan and histidine residues, hydrolysis adjacent to the lactam bridge, and aggregation at higher concentrations. Repeated freeze-thaw cycling accelerates loss of the parent peak. Working aliquots are therefore prepared once, held cold, and used without letting the stock return to ambient temperature.
Quality assessment of research-grade peptide rests mainly on reversed-phase high-performance liquid chromatography for purity and on mass spectrometry for identity confirmation. A single main peak above a stated threshold, commonly ninety-eight percent by peak area, is the usual release criterion applied by suppliers. Independent analyses commissioned by laboratories and consumer organisations have repeatedly reported discrepancies between label claims and measured content, including truncated sequences, residual trifluoroacetate, and lower-than-declared peptide mass. Those findings do not establish that every supplier is unreliable, but they indicate that purity figures printed on a vial are claims requiring verification rather than settled facts.
| 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 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.
Scientific discussion of Melanotan-2 spans pharmacology, dermatology, and public-health literature. Laboratory studies examine its receptor binding and cellular effects, while clinical reports describe outcomes observed after unregulated use. These two bodies of work differ in rigour and intent. Peer-reviewed trials of the compound as a medicine are limited, so much of the available information comes from case reports and surveillance data. Authors frequently note the gap between experimental findings and real-world use.
Reported observations after unregulated use include shifts in skin pigmentation and, in some accounts, unintended changes to moles and other lesions. Whether these outcomes are causally linked to the compound, and how often they occur, remain open questions because controlled data are scarce. The absence of standardised dosing and verified product purity complicates interpretation. Researchers have called for better surveillance and analytical characterisation of samples obtained outside regulated channels. Conclusions drawn from anecdotal evidence should be treated as provisional.
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.
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.
20th century In the 1920s, the Canadian Pacific and Canadian National Railways cooperated together to lay an elaborate system of 4,500 metre pneumatic tubing between four of their offices to Postal Station A at Union Station in Toronto, Canada. There was also a connection to the mail room at the Royal York Hotel. The newspapers the Star and Telegram joined into the system, laying pipes. In the 1960s, Lockheed and MIT with the United States Department of Commerce conducted feasibility studies on a vactrain system powered by ambient atmospheric pressure and "gravitational pendulum assist" to connect cities on the country's East Coast. They calculated that the run between Philadelphia and New York City would average 174 meters per second, that is 626 km/h (388 mph). When those plans were abandoned as too expensive, Lockheed engineer L.K. Edwards founded Tube Transit, Inc. to develop technology based on "gravity-vacuum transportation". In 1967 he proposed a Bay Area Gravity-Vacuum Transit for California that would run alongside the then-under construction BART system. It was never built.
=== Glands === Both the thyroid and adrenal glands can be infiltrated. It is estimated that 10–20% of people with amyloidosis have hypothyroidism. Adrenal infiltration may be harder to appreciate given that its symptoms of orthostatic hypotension and low blood sodium concentration may be attributed to autonomic neuropathy and heart failure. "Amyloid deposits occur in the pancreas of people who also have diabetes mellitus, although it is not known if this is functionally important. The major component of pancreatic amyloid is a 37-amino acid residue peptide known as islet amyloid polypeptide or 'amylin.' This is stored with insulin in secretory granules in [beta] cells and is co secreted with insulin." (Rang and Dale's Pharmacology, 2015.)
== Composition == The characteristic substances inside the extracellular matrix of soft tissue are the collagen, elastin and ground substance. Normally the soft tissue is very hydrated because of the ground substance. The fibroblasts are the most common cell responsible for the production of soft tissues' fibers and ground substance. Variations of fibroblasts, like chondroblasts, may also produce these substances.
Sources: en.wikipedia.org
TikTok was downloaded over 104 million times on Apple's App Store during the first half of 2018, according to data provided to CNBC by Sensor Tower. After merging with musical.ly in August, downloads increased and TikTok subsequently became the most downloaded app in the US in October 2018, which musical.ly had done once before. In February 2019, TikTok, together with Douyin, hit one billion downloads globally, excluding Android installs in China. In 2019, media outlets cited TikTok as the 7th-most-downloaded mobile app of the decade, from 2010 to 2019. It was also the most-downloaded app on Apple's App Store in 2018 and 2019, surpassing Facebook, YouTube and Instagram. In September 2020, a deal was confirmed between ByteDance and Oracle in which the latter will serve as a partner to provide cloud hosting. In November 2020, TikTok signed a licensing deal with Sony Music. In December 2020, Warner Music Group signed a licensing deal with TikTok. The advertising revenue of short video clips is lower than other social media: while users spend more time, American audience is monetized at a rate of $0.31 per hour, a third the rate of Facebook and a fifth the rate of Instagram, $67 per year while Instagram will make more than $200. In July 2023, Iranian Mehr News Agency reported "experts from Douyin" will meet Iranian business in Tehran to enable Iranian exports to China. In 2023, several high-level executives transferred from ByteDance to TikTok to focus on moneymaking operations. Some moved from Beijing to the US.
Macrocrystalline aqueous suspensions of progesterone as well as microspheres of progesterone were investigated as potential progestogen-only injectable contraceptives and combined injectable contraceptives (with estradiol) by the late 1980s and early 1990s but were never marketed. Aqueous solutions of water-insoluble steroids were first developed via association with colloid solubility enhancers in the 1940s. An aqueous solution of progesterone for use by intravenous injection was marketed by Schering AG under the brand name Primolut Intravenous by 1962. One of its intended uses was the treatment of threatened abortion, in which rapid-acting effect was desirable. An aqueous solution of progesterone complexed with cyclodextrin to increase its water solubility was introduced for use by once-daily subcutaneous injection in Europe under the brand name Prolutex in the mid-2010s. In the 1950s, long-acting parenteral progestins such as hydroxyprogesterone caproate, medroxyprogesterone acetate, and norethisterone enanthate were developed and introduced for use by intramuscular injection. They lacked the need for frequent injections and the injection site reactions associated with progesterone by intramuscular injection and soon supplanted progesterone for parenteral therapy in most cases.
=== Videos === 2010: Comedy Central Presents – DVD/download/streaming 2013: Mostly Sex Stuff (Comedy Central 2012) – DVD/download/streaming 2015: Live at the Apollo (HBO Home Video) – DVD/download/streaming 2017: The Leather Special (Netflix) – Streaming 2019: Growing (Netflix) – Streaming
Sources: en.wikipedia.org
==== Eukaryotic algae ==== In nearly all species of eukaryotic algae (Chloromonas being one notable exception), upon induction of the CCM, ~95% of RuBisCO is densely packed into a single subcellular compartment: the pyrenoid. Carbon dioxide is concentrated in this compartment using a combination of CO2 pumps, bicarbonate pumps, and carbonic anhydrases. The pyrenoid is not a membrane-bound compartment but is found within the chloroplast, often surrounded by a starch sheath (which is not thought to serve a function in the CCM).
== Cause == Scleroderma is caused by genetic and environmental factors. Mutations in HLA genes seem to play a crucial role in the pathogenesis of some cases. Many experts believe that early endothelial cell injury and micro-vascular damage act as a key trigger in the disease cascade, linking genetic susceptibility and environmental exposure to immune activation and fibrosis. Likewise silica, aromatic and chlorinated solvents, ketones, trichloroethylene, welding fumes, and white spirits exposure seems to contribute to the condition in a small proportion of affected persons.
== Clinical trials == Clinical trials for muscular dystrophy have not proven successful in generating functional improvements compared to placebo. Gains of muscle mass were small to non-existent in this population. Research is ongoing on the potential use of myostatin inhibitors for motor neuron diseases like spinal muscle atrophy and amyotrophic lateral sclerosis. Due to myostatin's effect as a negative regulator of bone, its inhibition has also been considered for orthopedic diseases such as rheumatoid arthritis. Myostatin inhibitors were generally able to increase lean body mass and reduce body fat in people with sarcopenia, but the extent to which this translated into functional improvements varied. Bimagrumab showed effectiveness in increasing lean mass and reducing fat mass in obese individuals in a clinical trial.
One of the 4th Panzer Army commanders, Erich Hoepner, was executed for his role in the 20 July plot. Following the end of the war, one of the 4th Panzer Army former commanders, Hermann Hoth, was tried in the High Command Trial, one of the Subsequent Nuremberg Trials. Explaining his harsh measures against Jews and other civilians, he claimed that "it was a matter of common knowledge in Russia that it was the Jew in particular who participated in a very large extent in sabotage, espionage, etc." Hoth was found guilty of war crimes and crimes against humanity. On 27 October 1948, he was sentenced to 15 years in prison. In January 1951, the sentence was reviewed with no changes. Hoth was released on parole in 1954; his sentence was reduced to time served in 1957. None of the other commanders ever faced charges.
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.
Solutions are best kept cold, protected from light, and buffered to a pH that limits hydrolysis. Dividing a stock into single-use aliquots avoids repeated freeze-thaw cycles, which measurably reduce the intact parent peak over time.