reversed-phase HPLC raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-05-15 and is reviewed periodically as new material appears.
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.
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.
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 II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
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.
| Property | Value | Notes |
|---|---|---|
| Lyophilised storage | −20 °C, dry, protected from light | Vials are sealed and allowed to reach room temperature before opening |
| Reconstituted storage | 2 to 8 °C, protected from light | Short-term holding; avoid repeated freeze-thaw cycles |
| Reconstitution solvent | Water for injection or bacteriostatic water | Added slowly along the vial wall to reduce foaming and shear |
| Purity measurement | RP-HPLC with area normalisation | Acetonitrile-water gradient monitored at roughly 214 nm |
| Identity confirmation | Electrospray ionisation mass spectrometry | Observed mass compared against the calculated peptide mass |
Regulatory status varies by jurisdiction, and the substance is frequently described as unapproved for therapeutic use. Some authorities classify it alongside prescription-only medicines or controlled categories, while others address it through general consumer protection rules. Analytical surveys have reported mismatches between label claims and measured content in products sold online, although the scope of such testing is limited. Whether these discrepancies are widespread remains an open question. Discussion in the literature therefore tends to combine chemistry, supply-chain observation and policy analysis.
The material is commonly handled as a lyophilized powder in sealed vials. The solid dissolves readily in water and in polar organic solvents, producing a clear solution after reconstitution. Light, heat and repeated freeze-thaw cycles are the concerns most often raised in handling guidance, because peptide bonds and the constrained ring can degrade. Working solutions are generally prepared fresh, and material left in solution is treated as less stable than the dry form. These properties shape how laboratories store and aliquot reference material.
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.
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.
RDA = Recommended Dietary Allowance; AI = Adequate intake; UL = Tolerable upper intake level; Figures shown are for adults age 31–50, male or female neither pregnant nor lactating * One serving of seaweed exceeds the US UL of 1100 μg but not the 3000 μg UL set by Japan.
=== Threonine === In plants and microorganisms, threonine is synthesized from aspartic acid via α-aspartyl-semialdehyde and homoserine. Homoserine undergoes O-phosphorylation; this phosphate ester undergoes hydrolysis concomitant with relocation of the OH group. Enzymes involved in a typical biosynthesis of threonine include aspartokinase, β-aspartate semialdehyde dehydrogenase, homoserine dehydrogenase, homoserine kinase, threonine synthase. The biosynthesis of threonine is regulated via allosteric regulation of its precursor, homoserine, by structurally altering the enzyme homoserine dehydrogenase. This reaction occurs at a key branch point in the pathway, with the substrate homoserine serving as the precursor for the biosynthesis of lysine, methionine, threonin and isoleucine. High levels of threonine result in low levels of homoserine synthesis. The synthesis of aspartate kinase (AK), which catalyzes the phosphorylation of aspartate and initiates its conversion into other amino acids, is feed-back inhibited by lysine, isoleucine, and threonine, which prevents the synthesis of the amino acids derived from aspartate. So, in addition to inhibiting the first enzyme of the aspartate families biosynthetic pathway, threonine also inhibits the activity of the first enzyme after the branch point, i.e. the enzyme that is specific for threonine's own synthesis.
== June 17, 1915 (Thursday) == Second Battle of Artois — French forces launched a second attack on Vimy Ridge but failed to take it. British pilot Reginald Warneford died along with American journalist Henry Beach Newman after crashing a new Farman biplane during takeoff from Buc, France, just shortly after a ceremony in Paris in which he received the French Legion of Honour for shooting down a German airship. Former U.S. President William Howard Taft became president of the League to Enforce Peace when it was established during a peace convention at Independence Hall in Philadelphia. Other founding members of the organization included Elihu Root, Alexander Graham Bell, Rabbi Stephen Samuel Wise, U.S. Chamber of Commerce executives James Gibbons and Edward Filene, Harvard University President A. Lawrence Lowell, and former U.S. Cabinet member and diplomat Oscar Straus. The baseball stadium Bosse Field officially opened in Evansville, Indiana, the first municipally owned stadium in the United States. It is the third oldest operating ballpark after Fenway Park and Wrigley Field. Born: Mario Echandi Jiménez, 33rd President of Costa Rica from 1958 to 1962; in San José, Costa Rica (d. 2011) David "Stringbean" Akeman, American country musician, member of band for the TV variety show Hee Haw and a member of the Grand Ole Opry; in Annville, Kentucky, United States (d. 1973, murdered) Died: Thomas Jordan Jarvis, 79, American politician, 44th Governor of North Carolina (b. 1836)
== Processing == The processes by which nanoparticles self-assemble are widespread and important. Understanding why and how self-assembly occurs is key in reproducing and optimizing results. Typically, nanoparticles will self-assemble for one or both of two reasons: molecular interactions and external direction.
== History == In 2013 the company entered an agreement with GlyTech Inc. to cooperate on the production of glycosylated proteins and peptides. In 2015 it bought American Peptide, a bio-technology company in Sunnyvale, California. In the 2020s, Bachem announced and began construction of additional production capacity, including large-scale peptide manufacturing facilities in Bubendorf and the United States.
Sources: en.wikipedia.org
During charging these reactions and transports go in the opposite direction: electrons move from the positive electrode to the negative electrode through the external circuit. To charge the cell the external circuit has to provide electrical energy. This energy is then stored as chemical energy in the cell (with some loss, e. g., due to coulombic efficiency lower than 1). Both electrodes allow lithium ions to move in and out of their structures with a process called insertion (intercalation) or extraction (deintercalation), respectively. As the lithium ions "rock" back and forth between the two electrodes, these batteries are also known as "rocking-chair batteries" or "swing batteries" (a term given by some European industries). The following equations exemplify the chemistry (left to right: discharging, right to left: charging). The negative electrode half-reaction for the graphite is
=== Physical examination === Inspection of the patient's skin, particularly on the lower extremities, in conjunction with a thorough medical history, can provide valuable information regarding the possible presence of sudomotor dysfunction. Evidence of altered skin hydration, such as hyperkeratosis, excessive skin dander, rhagades, and ulcers, can be suggestive of sudomotor dysfunction. Presence of intense foot odor may be another presentation.
She also created the Nutshell Studies of Unexplained Death, intricate crime scene dioramas used to train investigators, which are still in use today. Mary Louisa Willard, a chemistry professor at Pennsylvania State University (Penn State) from the 1920s through early 1960s, used her expertise in microscopy and chemical forensics to assist local and international criminal investigations.
John Stewart debuted in Green Lantern vol. 2 #87 (December 1971/January 1972) when artist Neal Adams came up with the idea of a substitute Green Lantern. The decision to make the character African American-descent resulted from a conversation between Adams and editor Julius Schwartz, in which Adams recounts saying that given the racial makeup of the world's population, "we ought to have a black Green Lantern, not because we're liberals, but because it just makes sense." Adams created John Stewart as "a college graduate who has a profession", wanting to avoid the prevailing depictions of black people at the time who he stated "don't represent the aspirations of every Black person in America", such as gangbangers. Dennis O'Neil wrote the script for Stewart's debut issue in line with Adams' intention for the character, making him a college graduate and an architect, unemployed because of the significant percentage of unemployment for black people in America in the time period. In the original script, the character's name was Lincoln Washington, which was chosen by Schwartz. Adams confronted Schwartz about the name being a slave name, after which Schwartz told Adams to choose the character's new name, and Adams chose "John Stewart". Adams intentionally colored the character a darker brown, rather than the usual lighter, khaki-like coloring done on black characters at the time. DC production manager Sol Harrison asked Adams about his divergence from the usual colors for black characters, to which he replied, "Most Black people I know are pretty dark.
=== Official discovery === Roentgenium was first synthesized by an international team led by Sigurd Hofmann at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany, on December 8, 1994. The team bombarded a target of bismuth-209 with accelerated nuclei of nickel-64 and detected three nuclei of the isotope 272111:
Sources: en.wikipedia.org
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.
Liquid chromatography coupled to mass spectrometry is the most common approach because it combines a retention time with a mass measurement. A chromatographic peak alone cannot establish which peptide is present, so mass determination or amino acid analysis is used as an orthogonal confirmation alongside the separation.
This depends on buffer, pH, and concentration, and published stability data for this peptide are limited. In practice laboratories work through a refrigerated solution within a few weeks and discard samples that show cloudiness or visible particles. Freezing and thawing repeatedly is generally discouraged.
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.