This is a working overview of lactam bridge, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-08-07. Anything still debated is marked as such rather than presented as settled.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
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.
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.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
| 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 |
=== 2016–present: Move to Melbourne and suspension === Citing his friendship with incoming coach, Simon Goodwin, as the key reason for his move to Melbourne, Melksham noted the opportunity for a fresh start as another reason for his move. Melksham, along with 33 other Essendon players, were found guilty of using a banned performance-enhancing substance, thymosin beta-4, as part of Essendon's sports supplements program during the 2012 season. He and his teammates were initially found not guilty in March 2015 by the AFL Anti-Doping Tribunal, however, a guilty verdict was returned in January 2016 after an appeal by the World Anti-Doping Agency. He was suspended for two years which, with backdating, ended in November 2016; as a result, he served approximately fourteen months of his suspension and missed the entire 2016 season. After missing twelve months of football, Melbourne elected to ease Melksham back into training heading into the 2017 season, in which he did not join full training until January. With the intention to play the season on the half-back line and the wing, he played his first competitive match in Melbourne colours in the opening week JLT Community Series match against the Western Bulldogs at Whitten Oval playing as a defender. After playing all three matches in the JLT Community Series, he made his debut for Melbourne in the thirty point win against St Kilda at Etihad Stadium in round one.
Latin American leaders, including the presidents of Colombia, Guatemala and Mexico, have called for debate about legalizing and regulating aspects of drug production, trade or use. Some Latin leaders are discussing the need to experiment further with decriminalizing possession of drugs. Lawmakers are also proposing to scrap jail terms for growing coca and cannabis. As some Latin American leaders call for legalization of narcotics, Peru, a leading coca grower, remains opposed.
-direction. The drift velocity is perpendicular to the direction of the electric field. For the radial electric field produced by the electrodes in a Penning trap, the drift velocity will precess around the axial direction with some frequency
=== Nuclear testing and Use of Outer-Space treaties === The Partial Nuclear Test Ban Treaty was signed on August 5, 1963, by the United States, the Soviet Union, and over 100 other nations. This treaty banned nuclear weapons tests in the atmosphere, outer space, and underwater, restricting such tests to underground environments. The treaty followed heightened concerns over the militarization of space, amplified by the United States' Starfish Prime test in 1962, which involved the detonation of a nuclear device in the upper atmosphere. To further delineate the peaceful use of outer space, the United Nations facilitated the drafting of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, commonly known as the Outer Space Treaty. Signed on January 27, 1967, by the United States, the Soviet Union, and the United Kingdom, it entered into force on October 10, 1967. The treaty established space as a domain to be used exclusively for peaceful purposes, prohibiting the placement of nuclear weapons or any other weapons of mass destruction in orbit or on celestial bodies.
Sources: en.wikipedia.org
Buildings, operations, and management have become increasingly sophisticated since the mid-20th century, when international airports began to provide infrastructure for international civilian flights. Detailed technical standards have been developed to ensure safety, and common coding systems have been implemented to provide global consistency. The physical structures that serve millions of individual passengers and flights are among the most complex and interconnected in the world. By the second decade of the 21st century, there were over 1,200 international airports and almost two billion international passengers, along with 50 million metric tons (49,000,000 long tons; 55,000,000 short tons) of cargo passing through them annually. Border inspections are also meant to protect each country's agriculture from pests. National and international phytosanitary authorities maintain databases of border interceptions, occurrences, and establishments. Bebber et al., 2019 analyzes such records and finds that they underreport many important pest species, that island nations are more vulnerable because they have lower border-to-area ratios, and that pests are moving poleward to follow humans' crops as our crops follow global warming. A 'Quilantan' or 'Wave Through' entry is a phenomenon at American border checkpoints authorising a form of non-standard but legal entry without any inspection of travel documents. It occurs when border security personnel at a border crossing admit some individuals without conducting a standard interview or document review.
oxidative phosphorylation Also electron transport-linked phosphorylation or terminal oxidation. The process by which cells use chemical energy obtained by the oxidation of nutrients to power the production of adenosine triphosphate (ATP). Oxidative phosphorylation couples two related processes: in the electron transport chain, a series of enzyme-catalyzed redox reactions transfers electrons from energetic donors such as NADH and FADH through various intermediates and ultimately to a terminal electron acceptor such as molecular oxygen (O2); the energy liberated by these reactions is simultaneously used in chemiosmosis to move protons (H+) across a membrane and against their concentration gradient, generating an electrochemical potential which powers ATP synthase, an enzyme that catalyzes the phosphorylation of ADP into ATP. In eukaryotes, both of these processes are carried out by proteins embedded in the membranes of mitochondria and chloroplasts; in prokaryotes, they occur in the cell membrane.
Owing to its distance from open sea and its position on the southeastern portion of the European continent, Romania has a climate that is continental, with four distinct seasons. The average annual temperature is 11 °C (52 °F) in the south and 8 °C (46 °F) in the north. In summer, average maximum temperatures in Bucharest rise to 28 °C (82 °F), and temperatures over 35 °C (95 °F) are fairly common in the lower-lying areas of the country. In winter, the average maximum temperature is below 2 °C (36 °F). Precipitation is average, with over 750 mm (30 in) per year only on the highest western mountains, while around Bucharest it drops to approximately 570 mm (22 in). There are some regional differences: in western sections, such as Banat, the climate is milder and has some Mediterranean influences; the eastern part of the country has a more pronounced continental climate. In Dobruja, the Black Sea also exerts an influence over the region's climate.
Dickinsonia fossils are another notable fossil from the Ediacaran period, found in Southern Australia and Russia. It remains unknown what type of organism Dickinsonia was; however, it has been considered a polychaete, turbellarian/annelid worm, jellyfish, polyp, protist, lichen or mushroom. They were preserved in quartz sandstones, and date back to around 550 million years ago. Dickinsonia were soft-bodied organisms, that show some evidence of very slow movement. There are faint, circular imprints in the rock which follow a path, and then following the same path there is a more definite circular imprint of the same size. This indicates that the organism probably moved slowly from one feeding area to the next and absorbed nutrients. It is speculated that the organism probably had very small appendages that allowed it to move much like starfish do today.
In a short period of time, the seventeen-year-old went from open-mic nights at the club to regular paid shows, building his reputation in the process. Parallel to his increasing local Toronto-area popularity as an impressionist stand-up comic, Carrey tried to break into sketch comedy, auditioning to be a cast member for the 1980–81 season of NBC's Saturday Night Live. Carrey ended up not being selected by the show's new executive producer Jean Doumanian who picked thirty-one-year-old Charles Rocket instead. Decades later, after establishing himself as a Hollywood film star, Carrey would host the show in May 1996, January 2011, and October 2014. After not getting Saturday Night Live, Carrey took a voice acting job performing Clutch Cargo-inspired bits on The All-Night Show, an overnight program airing locally on the CFMT-TV channel branded as Multilingual Television (MTV). Continuing to perform his stand-up act of contortionist impressions in the city of Toronto and surrounding towns, in February 1981, nineteen-year-old Carrey was booked as the opening act for the rock band Goddo at The Roxy Theatre in Barrie for two shows on consecutive nights; the rock crowd booed him offstage and he refused to return for the second night. Two weeks later, however, a review of one of Carrey's spots at Yuk Yuk's—alongside a sizable photo of him doing a stage impression of Sammy Davis Jr.—appeared in the Toronto Star on the front page of its entertainment section with the writer Bruce Blackadar raving about "a genuine star coming to life".
Sources: en.wikipedia.org
=== Bernot et al. (2023) === In recent study, Bernot et al. placed Copepoda as a sister group to Branchiopoda in Allotriocarida, which result in the recovery of clade Communostraca. Multicrustacea was not found. There are some major changes within class Malacostraca.
Be in the region of the binding energy curve where a fission chain reaction is possible (i.e., above radium) Have a high probability of fission on neutron capture Release more than one neutron on average per neutron capture. (Enough of them on each fission, to compensate for non-fissions and absorptions in non-fuel material) Have a reasonably long half-life Be available in suitable quantities.
The decline of the Roman Empire led to the disappearance or destruction of much knowledge, though physicians still incorporated many aspects of the Greek tradition into training and practice. In Byzantium and the Islamic world, many of the Greek works were translated into Arabic and many of the works of Aristotle were preserved.
=== Signs and symptoms === The classic clinical syndrome for vitamin B6 deficiency is a seborrheic dermatitis-like eruption, atrophic glossitis with ulceration, angular cheilitis, conjunctivitis, intertrigo, abnormal electroencephalograms, microcytic anemia (due to impaired heme synthesis), and neurological symptoms of somnolence, confusion, depression, and neuropathy (due to impaired sphingosine synthesis). In infants, a deficiency in vitamin B6 can lead to irritability, abnormally acute hearing, and convulsive seizures. Less severe cases present with metabolic disease associated with insufficient activity of the coenzyme pyridoxal 5' phosphate (PLP). The most prominent of the lesions is due to impaired tryptophan–niacin conversion. This can be detected based on urinary excretion of xanthurenic acid after an oral tryptophan load. Vitamin B6 deficiency can also result in impaired transsulfuration of methionine to cysteine. The PLP-dependent transaminases and glycogen phosphorylase provide the vitamin with its role in gluconeogenesis, so deprivation of vitamin B6 results in impaired glucose tolerance.
== Education == Lee received a B.A. degree in chemistry from the University of Utah in 1971 and a Ph.D. in analytical chemistry from Indiana University Bloomington in 1975, after which he spent one year (1975–76) at the Massachusetts Institute of Technology as a postdoctoral research associate. Upon leaving MIT, he accepted a faculty position in the Chemistry Department at Brigham Young University, where he is the H. Tracy Hall Professor of Chemistry.
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.
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.