The short version of research chemical fits in a sentence. The long version — which is the one that helps — is below.
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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.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
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.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
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.
Because the substance circulates mainly through informal markets, verification is a recurring theme in technical discussion. Independent analyses have found that labeled content and actual content can diverge, and that purity varies between samples. Analytical laboratories use reversed-phase chromatography to separate components and mass spectrometry to confirm identity. Isotope-labeled internal standards improve quantification in complex matrices. Such methods describe what a sample contains but say nothing about its sterility, lawful status, or suitability for any use. Open questions remain about how consistently testing is applied across the supply chain.
Regulatory treatment of this peptide varies by country. It holds no marketing authorization as a medicine in the United States, the European Union, or most other jurisdictions. Some countries classify products containing it as prescription-only or unlicensed medicines, which restricts lawful supply. Authorities have issued public notices warning that unregulated products may contain undeclared or incorrect ingredients. The molecule also appears on prohibited lists for competitive sport. These measures address supply oversight rather than any approved therapeutic role.
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.
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.
These time and length-scales can be used to understand the dependence of the conduction velocity on the diameter of the neuron in unmyelinated fibers. For example, the time-scale τ increases with both the membrane resistance rm and capacitance cm. As the capacitance increases, more charge must be transferred to produce a given transmembrane voltage (by the equation Q = CV); as the resistance increases, less charge is transferred per unit time, making the equilibration slower. In a similar manner, if the internal resistance per unit length ri is lower in one axon than in another (e.g., because the radius of the former is larger), the spatial decay length λ becomes longer and the conduction velocity of an action potential should increase. If the transmembrane resistance rm is increased, that lowers the average "leakage" current across the membrane, likewise causing λ to become longer, increasing the conduction velocity.
In 2014, the Party General Office and State Council issued guidance on strengthening ideological education in colleges and universities. During Xi Jinping's tenure, numerous colleges and universities have established schools of Marxism. Xi has implemented a number of education reforms. Schools are required to adjust their opening hours to be consistent with work hours in their area so that parents can pick-up their children directly after work (in order to reduce reliance on private classes for adult supervision after school hours). Schools must also promote health by requiring outdoor physical education classes daily and providing eye examinations twice per term. Educational reforms have also limited the amount of homework students can be assigned. In 2021, Xi enacted the Double Reduction Policy (reducing excessive off-campus tutoring and reducing homework burdens), mandating schools may not assign homework to children to grades one and two, homework is limited to no more than 60 minutes for children in grades three to six, and no more than 90 minutes for middle school children. In July 2021, China enacted a series of rules designed to shutdown the private tutoring sector as part of its common prosperity program. Rules issued in July 2021 prohibits new registration of private tuition tutoring centers and required existing centers to re-organize as non-profits. Tuition centers are prohibited from being listed on the stock market or receiving "excessive capital." They are no longer permitted to offer tutoring on the weekends or during public holidays.
== Terminology structure == Each NPU entry holds a structured definition of the 'result type' it identifies. The definitions are expressed using well established concepts and terms from the field of laboratory medicine. References to internationally acknowledged classifications, nomenclatures and terminologies are filed where possible. This ensures that the definitions are unambiguous, and that the meaning of each concept will remain stable and accessible over time. The definition structure is based on the scientific concept of 'examination' – an examination studies one or more properties of a system (a delimited part of the universe). In a clinical laboratory terminology such as the NPU terminology the system of interest is assumed to be (part of) the patient or the environment, and the NPU definition structure states:
The Bergmann azlactone peptide synthesis is a classic organic synthesis process for the preparation of dipeptides. In the presence of a base, peptides are formed by aminolysis of N-carboxyanhydrides of amino acids with amino acid esters (1).
With its weight rested on the pelvis, it may have been free to move the hindlimbs. Getting back up again might have involved some stabilization from the diminutive forelimbs. The latter known as Newman's pushup theory has been debated. Nonetheless, Tyrannosaurus was probably able to get up if it fell, which only would have required placing the limbs below the center of gravity, with the tail as an effective counterbalance. Healed stress fractures in the forelimbs have been put forward both as evidence that the arms cannot have been very useful and as evidence that they were indeed used and acquired wounds, like the rest of the body.
Sources: en.wikipedia.org
Diagnosis is typically based on medical imaging, such as plain X-rays, and symptoms. In severe OI, signs on medical imaging include abnormalities in all extremities and the spine. As X-rays are often insensitive to the comparatively smaller bone density loss associated with type I OI, DEXA scans may be needed. An OI diagnosis can be confirmed through DNA or collagen protein analysis, but in many cases, the occurrence of bone fractures with little trauma and the presence of other clinical features such as blue sclerae are sufficient for a diagnosis. A skin biopsy can be performed to determine the structure and quantity of type I collagen. While DNA testing can confirm the diagnosis, it cannot absolutely exclude it because not all mutations causing OI are yet known and/or tested for. OI type II is often diagnosed by ultrasound during pregnancy, where already multiple fractures and other characteristic features may be visible. Relative to control, OI cortical bone shows increased porosity, canal diameter, and connectivity in micro-computed tomography. OI can also be detected before birth by using an in vitro genetic testing technique such as amniocentesis.
=== Resilin and spider silk === Resilin is an elastomeric insect protein, consisting of both α-helices and β-sheets structure. It is one of the most resilient protein in nature. It has a low stiffness ~0.6MPa but a high energy restoring percentage ~98%, and efficiently helps flying insects to flap wings or fleas to jump. Spider silk fibril is composed of stiff crystallized β-sheets structure, responsible for strength, and amorphous matrix surrounding, improving toughness and elongation ability. It has exceptionally high tensile strength and ductility, with respectively low density, compared to other natural fibril. Its feature varies from different kinds of spider for different utility.
Cancellous bone, spongy bone, or trabecular bone is the internal tissue of the skeletal bone and is an open-cell porous network that follows the material properties of biofoams. Cancellous bone has a higher surface-area-to-volume ratio than cortical bone and it is less dense. This makes it weaker and more flexible. The greater surface area also makes it suitable for metabolic activities such as the exchange of calcium ions. Cancellous bone is typically found at the ends of long bones, near joints, and in the interior of vertebrae. Cancellous bone is highly vascular and often contains red bone marrow where hematopoiesis, the production of blood cells, occurs. The primary anatomical and functional unit of cancellous bone is the trabecula. The trabeculae are aligned towards the mechanical load distribution that a bone experiences within long bones such as the femur. As far as short bones are concerned, trabecular alignment has been studied in the vertebral pedicle. Thin formations of osteoblasts covered in endosteum create an irregular network of spaces, known as trabeculae. Within these spaces are bone marrow and hematopoietic stem cells that give rise to platelets, red blood cells and white blood cells. Trabecular marrow is composed of a network of rod- and plate-like elements that make the overall organ lighter and allow room for blood vessels and marrow. Trabecular bone accounts for the remaining 20% of total bone mass but has nearly ten times the surface area of compact bone.
In a 2014 paper detailing the experimental results of the chemical characterization of flerovium, the GSI group wrote: "[flerovium] is the least reactive element in the group, but still a metal." Nevertheless, in a 2016 conference about chemistry and physics of heavy and superheavy elements, Alexander Yakushev and Robert Eichler, two scientists who had been active at GSI and FLNR in determining flerovium's chemistry, still urged caution based on the inconsistencies of the various experiments previously listed, noting that the question of whether flerovium was a metal or a noble gas was still open with the known evidence: one study suggested a weak noble-gas-like interaction between flerovium and gold, while the other suggested a stronger metallic interaction. The longer-lived isotope 289Fl has been considered of interest for future radiochemical studies. Experiments published in 2022 suggest that flerovium is a metal, exhibiting lower reactivity towards gold than mercury, but higher reactivity than radon. The experiments could not identify if the adsorption was due to elemental flerovium (considered more likely), or if it was due to a flerovium compound such as FlO that was more reactive towards gold than elemental flerovium, but both scenarios involve flerovium forming chemical bonds.
Sources: en.wikipedia.org
The Slovak National Uprising ("1944 Uprising") was an armed struggle between German Wehrmacht forces and rebel Slovak troops August–October 1944. It was centered at Banská Bystrica. The rebel Slovak Army, formed to fight the Germans, had an estimated 18,000 soldiers in August, a total which first increased to 47,000 after mobilisation on 9 September 1944, and later to 60,000, plus 20,000 partisans. However, in late August, German troops were able to disarm the Eastern Slovak Army, which was the best equipped, and thus significantly decreased the power of the Slovak Army. Many members of this force were sent to Nazi concentration camps; others escaped and joined partisan units. The Slovaks were aided in the Uprising by soldiers and partisans from the Soviet Union, United Kingdom, US, France, the Czech Republic, and Poland. In total, 32 nations were involved in the Uprising.
=== Protection against colon cancer === Garlic can prevent colorectal cancer, and several studies revealed that diallyl disulfide is a major component responsible for this action. The effect is dose dependent as demonstrated on mice. Diallyl disulfide affects cancer cells much more strongly than normal cells. It also results in a strong and dose-dependent accumulation of several agents, such as reactive oxygen species, which activate enzyme and lead to destruction of cancer cells.
== Early life == Ada Esther Lifshitz was born in the Geula quarter of Jerusalem on 22 June 1939. Her parents, Hillel and Esther Lifshitz, were Zionist Jews who had immigrated to the British Mandate of Palestine (now Israel) from Zduńska Wola, Poland, in 1933 before the establishment of Israel. Her father was a rabbi and came from a rabbinical family. They settled in Jerusalem and ran a grocery store, but found it difficult to make ends meet while also sharing a small apartment space to live in. Despite her family's poverty, her parents sent her to school in the upscale Beit HaKerem neighborhood to assure her a good education. When her father died at the age of 42, the family moved to Tel Aviv. Yonath assisted her mother in bringing income by babysitting or tutoring children after her father's death.
If RF value of a solution is zero, the solute remains in the stationary phase and thus it is immobile. If RF value = 1 then the solute has no affinity for the stationary phase and travels with the solvent front. For example, if a compound travels 9.9 cm and the solvent front travels 12.7 cm, the RF value = (9.9/12.7) = 0.779 or 0.78. RF value depends on temperature and the solvent used in experiment, so several solvents offer several RF values for the same mixture of compound. A solvent in chromatography is the liquid the paper is placed in, and the solute is the ink which is being separated.
There are innumerable types of artifacts present in museum collections that include or are composed of human remains, some with great scientific or medical merit and others with great cultural importance. Not only do the body parts vary greatly, but so do their methods of preservation.
Sources: en.wikipedia.org
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.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
Low temperature slows hydrolysis and oxidation, the two main routes by which the peptide backbone and side chains are modified. A lyophilised powder stored at −20 °C is more stable than one kept at room temperature, and once the material is dissolved the degradation rate rises, making refrigeration more important.