This is a working overview of reversed-phase HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-10-19 and is reviewed periodically as new material appears.
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.
Routine characterisation relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, using a C18 column and a water-acetonitrile gradient containing trifluoroacetic acid. Electrospray ionisation mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidised by-products that co-elute poorly. Sequence and stereochemistry require additional work, such as peptide mapping or amino acid analysis, because a chromatographic purity figure alone does not distinguish a diastereomer from the target peptide. Independent testing of research-grade material frequently shows measured content below the stated label, so a certificate of analysis is best read together with the method that produced it.
Melanotan-2 is handled in the laboratory as a lyophilised powder that dissolves readily in water, dimethyl sulfoxide and dimethylformamide, with limited solubility in ethanol. Stock solutions prepared in an organic solvent often precipitate when diluted into aqueous buffer, so gradual dilution with mixing is standard practice. The peptide carries a tryptophan residue and a histidine residue, both sensitive to oxidation and to alkaline conditions. Working solutions are therefore kept near neutral to slightly acidic pH, protected from light, and consumed within the same working session whenever that is practical.
| 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 |
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.
Melanotan-2 appears on the World Anti-Doping Agency prohibited list within the peptide hormone class, and several national regulators treat it as an unapproved prescription substance. Some countries restrict importation or sale for personal use. Because the compound is widely traded as a research chemical, the practical legal picture differs between jurisdictions and shifts over time. Human safety data covering long periods are limited, and whether repeated pigmentation changes carry any lasting risk to melanocytes remains an open question.
Freeze-dried melanotan-2 is normally kept as a desiccated powder at minus twenty degrees Celsius or lower, shielded from light and moisture. Peptides of this size degrade through hydrolysis, oxidation and deamidation, and each pathway accelerates as temperature and water activity rise. Repeated freeze-thaw cycles promote aggregation and loss of material, so aliquoting a stock solution before freezing is standard laboratory practice. Once dissolved, the solution is markedly less stable than the powder. In laboratory work, solutions are generally refrigerated and used within days rather than kept for months.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
Melanotan II holds no marketing authorisation from the Food and Drug Administration, the European Medicines Agency, the UK Medicines and Healthcare products Regulatory Agency or Australia's Therapeutic Goods Administration. Products sold under that name are treated as unapproved new drugs, and their sale or import is prohibited in several jurisdictions. Other countries classify the peptide as a prescription-only medicine or place it among controlled substances, so the legal position changes with the destination market. No pharmacopoeial monograph supplies an official specification, because the material is not a licensed pharmaceutical. Consequently, products offered online are not manufactured to a shared public standard.
The peer-reviewed record is dominated by small early-phase studies, case reports and pharmacovigilance summaries rather than large randomised trials. Papers typically examine tanning response, receptor selectivity or patterns of reported adverse events. Many note that participants obtained the peptide outside a clinical setting, which limits verification of composition and administered amount. Reported events vary widely, and causality is frequently unclear because the identity and purity of self-sourced material are unknown. Open questions include whether repeated melanocortin receptor stimulation produces cumulative effects, and how often label claims match actual content.
In 2014, Buc-ee's filed a lawsuit against Texas-based convenience store chain "Frio Beaver". Frio Beaver, a company with a logo also depicting a beaver in a yellow circle with a black outline, was accused of copying the Buc-ee's beaver head logo, which the company is widely known for in Texas. The case was settled out of court in December 2014; B&B Grocery Inc. agreed to stop using the "Frio Beaver" logo and mascot. In 2016, Buc-ee's sued "Choke Canyon BBQ", another Texas convenience store, for copyright infringement and trade dressing. Choke Canyon used a logo of a grinning alligator in the middle of a yellow circle, which Buc-ee's claimed was an attempt by the chain to resemble the Buc-ee's logo. Choke Canyon was also calling its new stores "Bucky's". Choke Canyon lost the federal lawsuit in May 2018, with Choke Canyon changing its logo to a cowboy inside of an orange circle. In 2017, Buc-ee's again filed a lawsuit for breaking an agreement, this time against a Nebraska-based convenience store chain known as "Bucky's". The two companies had agreed to remain in their respective states and expand only to states where the other did not operate. The lawsuit was thrown out. A non-logo related lawsuit was filed in 2013 against "Chicks", a convenience store in Bryan, Texas, for trade dress violations by allegedly copying Buc-ee's mega convenience store designs and layout. The case was settled out of court.
== Medical relevance == Genetic PGLYRP2 variants or changed expression of PGLYRP2 are associated with some diseases. Patients with inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, have significantly more frequent missense variants in PGLYRP2 gene (and also in the other three PGLYRP genes) than healthy controls. These results suggest that PGLYRP2 protects humans from these inflammatory diseases, and that mutations in PGLYRP2 gene are among the genetic factors predisposing to these diseases. PGLYRP2 variants are also associated with esophageal squamous cell carcinoma and Parkinson's disease. Increased serum PGLYRP2 levels are present in patients with systemic lupus erythematosus (and correlate with disease activity index, renal damage, and abnormal lipid profile), chronic hepatitis B virus infection, myocardial infarction, and coronary artery disease (and correlate with the severity of the disease). Decreased expression of PGLYRP2 is found in HIV-associated tuberculosis, drug-sensitive tuberculosis, Lyme disease, hepatocellular carcinoma, and polyarteritis nodosa. Autoantibodies to PGLYRP2 are significantly increased in patients with rheumatoid arthritis.
electric dipole moment A measure of the separation of positive and negative electric charges within an electrical system, i.e. a measure of the system's overall electrical polarity. The SI unit for measuring electric dipole moment is the coulomb-metre (C⋅m), but the debye (D), a non-SI unit, is also widely used in chemistry and atomic physics.
The description of feathered dinosaurs has not been without controversy in general; perhaps the most vocal critics have been Alan Feduccia and Theagarten Lingham-Soliar, who have proposed that some purported feather-like fossils are the result of the decomposition of collagenous fiber that underlaid the dinosaurs' skin, and that maniraptoran dinosaurs with vaned feathers were not actually dinosaurs, but convergent with dinosaurs. However, their views have for the most part not been accepted by other researchers, to the point that the scientific nature of Feduccia's proposals has been questioned. Archaeopteryx was the first fossil found that revealed a potential connection between dinosaurs and birds. It is considered a transitional fossil, in that it displays features of both groups. Brought to light just two years after Charles Darwin's seminal On the Origin of Species (1859), its discovery spurred the nascent debate between proponents of evolutionary biology and creationism. This early bird is so dinosaur-like that, without a clear impression of feathers in the surrounding rock, at least one specimen was mistaken for the small theropod Compsognathus. Since the 1990s, a number of additional feathered dinosaurs have been found, providing even stronger evidence of the close relationship between dinosaurs and modern birds. Many of these specimens were unearthed in the lagerstätten of the Jehol Biota.
Capillary electrophoresis–mass spectrometry (CE-MS) is a technique that combines the liquid separation process of capillary electrophoresis with mass spectrometry. CE-MS is typically coupled to electrospray ionization.
Sources: en.wikipedia.org
Some scholars suggest that early Christian Gnostic beliefs might have influenced Druze theology, particularly in concepts of divine knowledge and reincarnation. Some suggest that the Druze practice of religious secrecy and asceticism may have been influenced by the monastic traditions of Christianity, particularly Eastern Christian monasticism prevalent in the Levant region. These influences and incorporations of Christian elements encompass the adoption of the concept of Christianizing al-Mahdi's persona among the Druze, as well as the integration of verses from the Bible concerning the Messiah by certain Druze preachers. Modern Western scholars such as de Sacy, van Vloten, and Goldziher have highlighted the Messianic tendencies and the influence of Christian incarnation in the theology of early Druze founders as fundamental aspects of their doctrine. Scholar Rami İbrahim Mahmut from Istanbul University argues that early Christian elements are clearly evident in the Druze faith. For instance, the concept of a Christian-Mahdi figure was adopted by the Druze, and some Gospel citations originally referring to Jesus were applied to the Druze preacher Hamza ibn Ali. These texts were used to claim that he is the Messiah to be obeyed by Christians. This belief also extends to al-Hakim, whom some Druze believe will return as Christ to initiate the resurrection. The Druze deify al-Hākim bi-Amr Allāh, attributing to him divine qualities similar to those Christians attribute to Jesus.
For infant circumcision, devices such as the Gomco clamp, Plastibell and Mogen clamp are commonly used in the USA. These follow the same basic procedure. First, the amount of foreskin to be removed is estimated. The practitioner opens the foreskin via the preputial orifice to reveal the glans underneath and ensures it is normal before bluntly separating the inner lining of the foreskin (preputial epithelium) from its attachment to the glans. The practitioner then places the circumcision device (this sometimes requires a dorsal slit), which remains until blood flow has stopped. Finally, the foreskin is amputated. For older babies and adults, circumcision is often performed surgically without specialized instruments, and alternatives such as Unicirc, Shang ring or stapler circumcision are available.Depending on the specific surgical technique or anatomical requirements, the frenulum—an elastic band of tissue on the underside of the penis—may be either preserved or excised during the surgery. If this tissue is removed concurrently, the adjunctive procedure is known as a penile frenulectomy.
Illinois Central Railroad number 51000 was built in the McComb, Mississippi shops with an aluminum superstructure to reduce weight with steel where required for strength and provided the standard dimensions, cushioned draft gear, easy-riding trucks, minimum 4 inches (10 cm) of insulation, adjustable ice bunker bulkheads and half-stage icing racks with forced air circulation through side wall flues and floor racks recommended by UFF&VA. Santa Fe Refrigerator Despatch number 13000 was built of stainless steel by the Consolidated Steel Corporation of Wilmington, California with convertible ice bunkers, side ventilation ducts, and axle-driven circulation fans. It was thought that stainless steel would better resist the corrosive deterioration resulting from salting the ice. The one-of-a-kind unit entered service as #13000, but was subsequently redesignated as #1300, and later given #4150 in 1955. The car spent most of its life in express service. Cost was cited as the reason no additional units were ordered. The car was dismantled at Clovis, New Mexico in February 1964. Pacific Fruit Express rebuilt two steel-sided ventilator refrigerator cars in their Los Angeles shops with aluminum car bodies to test the durability of lightweight alloys versus that of steel. It was hoped that weight savings (the units weighed almost 10,000 lb (4,536 kg) less than a like-sized all-steel car) and better corrosion resistance would offset the higher initial cost. Alcoa provided the body for number 44739, and Reynolds Aluminum Company provided number 45698.
Hydrazine reflux is commonly used for reducing SLGO to SLG(R), but titrations show that only around 20–30% of the carboxylic groups are lost, leaving a significant number available for chemical attachment. Analysis of SLG(R) generated by this route reveals that the system is unstable and using a room temperature stirring with hydrochloric acid (< 1.0 M) leads to around 60% loss of COOH functionality. Room temperature treatment of SLGO with carbodiimides leads to the collapse of the individual sheets into star-like clusters that exhibited poor subsequent reactivity with amines (c. 3–5% conversion of the intermediate to the final amide). It is apparent that conventional chemical treatment of carboxylic groups on SLGO generates morphological changes of individual sheets that leads to a reduction in chemical reactivity, which may potentially limit their use in composite synthesis. Therefore, chemical reaction types have been explored. SLGO has also been grafted with polyallylamine, cross-linked through epoxy groups. When filtered into graphene oxide paper, these composites exhibit increased stiffness and strength relative to unmodified graphene oxide paper. Full hydrogenation from both sides of the graphene sheet results in Graphane, but partial hydrogenation leads to hydrogenated graphene. Similarly, both-side fluorination of graphene (or chemical and mechanical exfoliation of graphite fluoride) leads to fluorographene (graphene fluoride), while partial fluorination (generally halogenation) provides fluorinated (halogenated) graphene.
Sources: en.wikipedia.org
The longest word in Spanish is esternocleidomastoideitis (inflammation of the sternocleidomastoid muscle, 30 letters). Runners-up are anticonstitucionalmente ([proceeding in a manner that is] contrary to the constitution (anticonstitutionally)) and electroencefalografistas (specialists that do electrical scans on brains (electroencephalographists)), both 23 letters. The word anticonstitucionalmente is usually considered the longest word in general use. This word can be made even longer by the addition of the absolute superlative suffix, rendering anticonstitucionalísimamente (i.e.: "very strongly against the constitution"). Some dictionaries (but not the RAE dictionary) removed its root word (anticonstitucional) in 2005, causing comments about it not "being a valid word anymore" and suggesting the use of inconstitucional as a replacement.
Because the use of broad-spectrum antibiotics encourages the spread of multidrug-resistant strains and the development of Clostridioides difficile infections, treatment guidelines often recommend minimizing the use of fluoroquinolones and other broad-spectrum antibiotics in less severe infections and in those in which risk factors for multidrug resistance are not present. It has been recommended that fluoroquinolones not be used as a first-line agent for community-acquired pneumonia, instead recommending macrolide or doxycycline as first-line agents. The Drug-Resistant Streptococcus pneumoniae Working Group recommends fluoroquinolones be used for the ambulatory treatment of community-acquired pneumonia only after other antibiotic classes have been tried and failed, or in cases with demonstrated drug-resistant Streptococcus pneumoniae. Resistance to quinolones can evolve rapidly, even during a course of treatment. Numerous pathogens, including Escherichia coli, commonly exhibit resistance. Widespread veterinary usage of quinolones, in particular in Europe, has been implicated. Fluoroquinolones had become the class of antibiotics most commonly prescribed to adults in 2002. Nearly half (42%) of these prescriptions were for conditions not approved by the U.S. FDA, such as acute bronchitis, otitis media, and acute upper respiratory tract infection, according to a study supported in part by the Agency for Healthcare Research and Quality.
Hemoglobin C/ beta thalassemia: common in Mediterranean and African populations generally results in a moderate form of anemia with splenomegaly. Hemoglobin D/ beta thalassemia: common in the northwestern parts of India and Pakistan (Punjab region). Hemoglobin E/ beta thalassemia: common in Cambodia, Thailand, and parts of India, it is clinically similar to β thalassemia major or β thalassemia intermedia. Hemoglobin S/ beta thalassemia: common in African and Mediterranean populations, it is clinically similar to sickle-cell anemia. Delta-beta thalassemia is a rare form of thalassemia in which there is a reduced production of both the delta and beta globins. It is generally asymptomatic.
=== Immunoprecipitation === The liquid-phase ligand binding assay of immunoprecipitation (IP) is a method that is used to purify or enrich a specific protein, or a group of proteins, using an antibody from a complex mixture. The extract of disrupted tissue or cells is mixed with an antibody against the antigen of interest, which produces the antigen-antibody complex. When antigen concentration is low, the antigen-antibody complex precipitation can take hours or even days and becomes hard to isolate the small amount of precipitate formed. The enzyme-linked immunosorbent assay (ELISA) or Western blotting are two different ways that the purified antigen (or multiple antigens) can be obtained and analyzed. This method involves purifying an antigen through the aid of an attached antibody on a solid (beaded) support, such as agarose resin. The immobilized protein complex can be accomplished either in a single step or successively. IP can also be used in conjunction with biosynthetic radioisotope labeling. Using this technique combination, one can determine if a specific antigen is synthesized by a tissue or by a cell.
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses. DNA and ribonucleic acid (RNA) are nucleic acids. Alongside proteins, lipids and complex carbohydrates (polysaccharides), nucleic acids are one of the four major types of macromolecules that are essential for all known forms of life. The two DNA strands are known as polynucleotides as they are composed of simpler monomeric units called nucleotides. Each nucleotide is composed of one of four nitrogen-containing nucleobases (cytosine [C], guanine [G], adenine [A] or thymine [T]), a sugar called deoxyribose, and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds (known as the phosphodiester linkage) between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone. The nitrogenous bases of the two separate polynucleotide strands are bound together, according to base pairing rules (A with T and C with G), with hydrogen bonds to make double-stranded DNA. The complementary nitrogenous bases are divided into two groups, the single-ringed pyrimidines and the double-ringed purines. In DNA, the pyrimidines are thymine and cytosine; the purines are adenine and guanine. Both strands of double-stranded DNA store the same biological information. This information is replicated when the two strands separate.
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.
Purity is normally stated as an area percentage from high-performance liquid chromatography, for example ninety-five or ninety-eight percent. That figure describes the proportion of ultraviolet-absorbing material eluting as the main peak. It says nothing about water content, counterions, residual solvents or mass fraction of the peptide itself.