The short version of melanogenesis fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-12-02. Anything still debated is marked as such rather than presented as settled.
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, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
| 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. 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.
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.
Ultralente insulin was a long-acting form of medical insulin, but not a true analogue. It had an onset of 4 to 6 hours, a peak effect between 14 and 24 hours, and a duration of 28 to 36 hours. In the mid-2000s, ultralente insulin, along with lente insulin, was discontinued in the United States due to decreasing use in favor of NPH insulin and newer insulin products. By 2011, the U.S. Food and Drug Administration (FDA) had officially withdrawn approval for ultralente insulin products.
=== Tumis tempe or oseng tempe === Stir-fried tempeh with vegetables such as green bean, basil, or onion, with spices. Other recipes might add coconut milk for a milky-colored, and rather moist, stir-fried tempeh.
Tartaric acid, an acid that forms diastereomeric salts with chiral amines Antimony potassium tartrate, an anion, that forms diastereomeric salts with chiral cations. Mandelic acid, an acid that forms diastereomeric salts with chiral amines. Camphorsulfonic acid, an acid that forms diastereomeric salts with chiral amines. Also 3-bromocamphor-8-sulfonic acid 1-Phenylethylamine, a base that forms diastereomeric salts with chiral acids. Many related chiral amines have been demonstrated.
Sources: en.wikipedia.org
Report ITU-R BT.2246-3 (2014) The present state of ultra-high definition television Draft New Report ITU-R BT.[UHDTV-DTT TRIALS] (Sub-Working Group 6A-1) Collection of field trials of UHDTV over DTT networks
is the packing fraction of the particles. This model is not very accurate for nanoparticles for it does not take into account the interfacial layer formed by the fluid around a nanoparticle. In 2006 K. C. Leong et al proposed a new model, one which took into account the existence of an interfacial layer. They did so by considering the area around a nanoparticle and stating it exists of three separate regions. Each of them with a specific but different thermal conductivity. This resulted in the following model:
== Metabolism and survival == The metabolism of endolithic microorganisms is versatile; genes involved in sulphur metabolism, iron metabolism and carbon fixation have been found in many endolithic communities. Whether they metabolize directly from the surrounding rock, or excrete an acid to dissolve it first is yet undetermined. According to Meslier & DiRuggiero there are genes found in the endolithic community involved in nitrogen fixation. The Ocean Drilling Program found microscopic trails in basalt from the Atlantic, Indian, and Pacific oceans that contain DNA. Photosynthetic endoliths have also been discovered. As water and nutrients are sparse in the endolith's surrounding environment, water limitation is a key factor in the capacity of survival of many endolithic microorganisms. Many of those microorganisms have adaptations to survive in low concentrations of water. Additionally, pigments such as beta carotenes and chlorophyll, especially in cyanobacteria and some algae, help to protect against dangerous radiation and act as a way to obtain energy. Another characteristic is the presence of a very slow reproduction cycle. Early data suggest some only engage in cell division once every hundred years. In August 2013, researchers reported evidence of endoliths in the ocean floor, perhaps millions of years old and reproducing only once every 10,000 years. Most of their energy is spent repairing cell damage caused by cosmic rays or racemization, and very little is available for reproduction or growth.
Sources: en.wikipedia.org
=== Emerging or aspirational technologies === Fruit juices contain compounds that can be undesirable to consumers. Apple juices can be cloudy, and grapefruit juices can be bitter. Enzymatic technologies, involving respectively pectinases and naringinase, address these problems.
Zinder's fadas were mixed-gender, and some had as many as 200 members. They were largely led by youths with successful occupations, while most also appointed adults as counselors, who helped with meetings without participating. They met weekly and collected weekly membership fees along with a fee to join. This money went partly toward radio greetings, which allowed emerging fadas to make themselves known and large fadas to highlight individual members; some purchased over 100 greetings per week, each listing five names. The largest fadas performed large projects; for example, the White House fada helped to build a school, and the Club Maxi fada hosted a performance by a theater troupe from Nigeria. The mayor of Zinder attended most fada activities to build support, but his attempt to organize a rally of fadantchés failed. To faciliate collaboration between fadas and the government, he proposed the Fédération des Fada, des Clubs de Jeunes et Associations Assimilée (FFCJA; transl. Federation of Fadas, Youth Clubs, and Affiliated Associations), which was established in 1998 with the membership of 80 fadas, while 9 declined. They elected the leader of the federation, and the losing candidate founded a smaller, competing federation, the Union des Fadas Zindirma (transl. Union of Fadas of Zinder). The federations were not very active, but their regulations led fadas to gain formal recognition as organizations. Fadas remained largely independent of politics.
Natural hafnium (72Hf) consists of five observationally stable isotopes (176Hf, 177Hf, 178Hf, 179Hf, and 180Hf) and one very long-lived radioisotope, 174Hf, with a half-life of 3.8×1016 years. The next most stable radioisotope is 182Hf with a half-life of 8.90 million years, an extinct radionuclide used in hafnium–tungsten dating to study the chronology of planetary differentiation. Other isotopes have been synthesized running from 153Hf to 192Hf, but none of the 33 others has a half-life over 1.87 years, and most have half-lives under five minutes. There are also at least 41 nuclear isomers, the most stable of which is 178m2Hf with a half-life of 31 years. All isotopes of hafnium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.
== Medical uses == In the United States empagliflozin/linagliptin is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus and to reduce the risk of cardiovascular death in adults with type 2 diabetes mellitus and established cardiovascular disease. In the European Union empagliflozin/linagliptin is indicated in adults aged 18 years and older with type 2 diabetes mellitus:
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 analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.