The short version of lactam bridge fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-09-20. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
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.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
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.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
==== India ==== Hitchens wrote on India across multiple decades, addressing Hindu nationalism, the legacy of Gandhi, religious violence, and the country's relationship with Pakistan. Writing for Vanity Fair from Amritsar in August 1997, Hitchens condemned the 1992 demolition of the Babri Masjid in Ayodhya as "a crowning disgrace," and characterised the growing Hindu nationalist movement in India as "quasi-fascist" and "semi-criminal." In God Is Not Great (2007), Hitchens used Bombay (now Mumbai) as a case study of how religion fuels communal violence, listing it alongside Belfast, Beirut, Belgrade, Bethlehem, and Baghdad. In Chapter 14, titled "There Is No 'Eastern' Solution," he argued that Hinduism and Buddhism were equally vulnerable to irrationality and violence as the Abrahamic religions, rejecting the notion of an enlightened "Eastern" alternative to Western religion. In a 2011 essay for The Atlantic titled "The Real Mahatma Gandhi," written as a review of Joseph Lelyveld's biography Great Soul, Hitchens critically re-examined Gandhi's legacy. He questioned the universality of Gandhi's doctrine of nonviolence, citing Gandhi's letters to Adolf Hitler during World War II in which Gandhi urged the application of satyagraha against the Nazi regime. Hitchens argued that Gandhi's religious and ascetic worldview was fundamentally incompatible with secular and democratic politics.
== Diagnosis == Myiasis is often misdiagnosed in the United States because it is rare and its symptoms are not specific. Intestinal myiasis and urinary myiasis are especially difficult to diagnose. Clues that myiasis may be present include recent travel to an endemic area, one or more non-healing lesions on the skin, itchiness, movement under the skin or pain, discharge from a central punctum (tiny hole), or a small, white structure protruding from the lesion. Serologic testing has also been used to diagnose the presence of botfly larvae in human ophthalmomyiasis.
Foodborne diseases, emerging, WHO, Fact sheet N°124, revised January 2002 Foodborne illness information pages Archived December 30, 2019, at the Wayback Machine, NSW Food Authority Food safety and foodborne illness, WHO, Fact sheet N°237, revised January 2002 UK Health protection Agency US PulseNet Food poisoning from NHS Direct Online Food Safety Network hosted at the University of Guelph, Canada. Food Standard Agency website
=== Health and accident === On the evening of August 3, 2008, Freeman was injured in an automobile crash when his 1997 Nissan Maxima was involved in a rollover near Ruleville, Mississippi. He and his passenger, Demaris Meyer, had to be cut free from the vehicle with hydraulic tools. Freeman was conscious after the crash and joked with a photographer at the scene. He was taken via helicopter to The Regional Medical Center (The Med) hospital in Memphis. His left shoulder, arm, and elbow had been broken, and he received surgery on August 5. Doctors operated on him for four hours to repair nerve damage in his shoulder and arm. His publicist announced he was expected to make a full recovery. Although alcohol was not considered a factor in the crash, Meyer sued Freeman for negligence, claiming that he had been consuming alcohol, but the suit was eventually settled for an undisclosed amount. Freeman developed fibromyalgia following the incident, and had to switch dominant hands as his left was paralyzed. In 2010, he was diagnosed with stage 1 colon cancer and underwent a successful surgery to remove the tumor.
Assist with Post Mortem Examinations Preparation and Operation of a Mortuary Prepare for Post Mortem Examinations Team Working Viewing of the Deceased In addition to formal training, dieners learn how to do basic tasks through shadowing a mentor.
Sources: en.wikipedia.org
=== Alternative x-axis notations === There are several alternatives to the standard m/z notation that appear in the literature; however, these are not currently accepted by standards organizations and most journals. m/e appears in older historical literature. A label more consistent with the IUPAC green book and ISO 31 conventions is m/Q or m/q where m is the symbol for mass and Q or q the symbol for charge with the units u/e or Da/e. This notation is not uncommon in the physics of mass spectrometry but is rarely used as the abscissa of a mass spectrum. It was also suggested to introduce a new unit thomson (Th) as a unit of m/z, where 1 Th = 1 u/e. According to this convention, mass spectra x axis could be labeled m/z (Th) and negative ions would have negative values. This notation is rare and not accepted by IUPAC or any other standards organisation.
This is mathematically incorrect (if the rule was precisely accurate the required temperature increase would be about 15.8 °C (28.4 °F)), and in any case the rule is only a rough approximation and cannot always be relied on. Chemists often use the more comprehensive Arrhenius equation for better estimations. The same is true, up to a point, of the chemical reactions of living things. They are usually catalyzed by enzymes which change reaction rates, but with no variation in catalytic action, the rule of thumb is still mostly applicable. In the case of bacteria and fungi, the reactions needed to feed and reproduce speed up at higher temperatures, up to the point that the proteins and other compounds in their cells themselves begin to break down, or denature, so quickly that they cannot be replaced. This is why high temperatures kill bacteria and other micro-organisms: 'tissue' breakdown reactions reach such rates that they cannot be compensated for and the cell dies. On the other hand, 'elevated' temperatures short of these result in increased growth and reproduction; if the organism is harmful, perhaps to dangerous levels. Just as temperature increases speed up reactions, temperature decreases reduce them. Therefore, to make explosives stable for longer periods, or to keep rubber bands springy, or to force bacteria to slow down their growth, they can be cooled. That is why shelf life is generally extended by temperature control: (refrigeration, insulated shipping containers, controlled cold chain, etc.) and why some medicines and foods must be refrigerated.
=== Brazil === The R2 Combat Operation Ration (Portuguese: Ração Operacional de Combate – R2) is the current field & combat ration for the Brazilian Army. It is based on the earlier, but similar, Alternative Combat Ration for 24 Hours (Portuguese: Ração Alternativa de Combate, 24 horas) developed by the Brazilian Navy for use by Naval Infantry units. It contains the food and supplemental items needed by 1 soldier for 24 hours. It is to be used in situations where no other type of ration is available. All foods are packed inside 4-ply plastic and aluminum polylaminate retort pouches and are ready to eat without further preparation. The ration is packed inside a heavy-duty (.25 mm thick) matte green or olive drab polyethylene bag measuring 300 mm wide by 400 mm long. It is printed with the logo of the Brazilian Army, the name of the ration, and menu information. Inside are 5 thinner (.10 mm) semi-transparent plastic bags, one for each meal and one for the accessories. Each bag is printed with meal information and contents.
== Safety considerations == Inhalation of crystalline silica harms the lungs, causing silicosis. Amorphous silica is considered to have low toxicity, but prolonged inhalation causes lung changes. Diatomaceous earth is mainly amorphous silica but contains some crystalline silica, especially in the saltwater forms. In a 1978 study of workers, those exposed to natural diatomaceous earth for over five years had no significant lung changes while 40% of those exposed to the calcined form had developed pneumoconiosis. Today's standard diatomaceous earth formulations are safer to use, as they are predominantly made of amorphous silica and contain little or no crystalline silica. The crystalline silica content of diatomaceous earth is regulated in the United States by the Occupational Safety and Health Administration (OSHA). There are guidelines from the National Institute for Occupational Safety and Health that set maximum amounts allowable in the product (1%) and in the air near the breathing zone of workers, with a recommended exposure limit at 6 mg/m3 over an 8-hour workday. OSHA has set a permissible exposure limit for diatomaceous earth as 20 mppcf (80 mg/m3/%SiO2). At levels of 3,000 mg/m3, diatomaceous earth is immediately dangerous to life and health. In the 1930s, workers with long-term occupational exposure in the cristobalite diatomaceous earth industry who were exposed to high levels of airborne crystalline silica over decades were found to have an increased risk of silicosis.
Sources: en.wikipedia.org
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.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
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.