The short version of melanocortin receptor fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-10-05. Anything still debated is marked as such rather than presented as settled.
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.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
Quality assessment of research-grade peptide rests mainly on reversed-phase high-performance liquid chromatography for purity and on mass spectrometry for identity confirmation. A single main peak above a stated threshold, commonly ninety-eight percent by peak area, is the usual release criterion applied by suppliers. Independent analyses commissioned by laboratories and consumer organisations have repeatedly reported discrepancies between label claims and measured content, including truncated sequences, residual trifluoroacetate, and lower-than-declared peptide mass. Those findings do not establish that every supplier is unreliable, but they indicate that purity figures printed on a vial are claims requiring verification rather than settled facts.
Regulatory treatment varies by jurisdiction and has changed over time. In several countries the peptide is handled as an unapproved prescription medicine, and import or sale for human use is restricted, while elsewhere it falls under poisons or controlled-substance schedules. Enforcement activity against online vendors has been reported in Australia, New Zealand, the United Kingdom and the United States. Scholarly writing discusses melanotan-2 chiefly as an experimental tool and as a case study in unregulated peptide supply, and its precise legal position in any given country should be checked against current national schedules.
Lyophilised melanotan-2 is comparatively robust when kept dry, cold and dark, and a desiccated powder stored at minus twenty degrees Celsius or below is generally expected to retain its chemical integrity for extended periods. In solution the peptide is far less stable, with degradation proceeding through oxidation of tryptophan and histidine residues, hydrolysis adjacent to the lactam bridge, and aggregation at higher concentrations. Repeated freeze-thaw cycling accelerates loss of the parent peak. Working aliquots are therefore prepared once, held cold, and used without letting the stock return to ambient temperature.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Alpha-MSH analogue with a lactam ring |
| Molecular formula | C50H69N15O9 | Commonly cited value for the neutral peptide |
| Molecular weight | 1024.18 g/mol | Calculated for the free molecule |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water, DMSO and ethanol | Dissolution in pure water is often slow |
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.
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.
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.
It is a protic solvent, capable of forming hydrogen bonds. It has a high donor number, making it a strong Lewis base. It has a high dielectric constant (relative permittivity), making it a good solvent for ionic species. pKa values of organic compounds are often obtained using the aprotic solvents dimethyl sulfoxide (DMSO) and acetonitrile (ACN).
=== Golgi tendon organs === Houk and Simon provided one of the first mathematical models of a Golgi tendon organ receptor, modeling the firing rate of the receptor as a function of the muscle tension force. Just as for muscle spindles, they find that, as the receptors respond linearly to sine waves of different frequencies and has little variance in response over time to the same stimulus, Golgi tendon organ receptors may be modeled as linear time-invariant systems. Specifically, they find that the firing rate of a Golgi tendon organ receptor may be modeled as a sum of 3 decaying exponentials:
==== Structural impacts on hydrogen storage capacity ==== To date, hydrogen storage in MOFs at room temperature is a battle between maximizing storage capacity and maintaining reasonable desorption rates, while conserving the integrity of the adsorbent framework (e.g., completely evacuating pores, preserving the MOF structure, etc.) over many cycles. There are two major strategies governing the design of MOFs for hydrogen storage:
In the city of Havana, which had a population of 200,000 people, less than 3,000 people regularly attended mass at the Catholic Church. In the wake of the declining Catholic Church, Freemasonry's impact on the island grew. Cuban Freemasons advanced scientific thought, modernized education, and provided an alternative Cuban identity in the vacuum of the Vatican's hegemony. In the main cities, Masonic Lodges created and maintained public schools, libraries, and lecture halls. The three most prominent Lodges in Cuba during this period were Logia Amor Fraternal, Logia San Andrés, and Logia Plus Ultra. Claudio Justo Vermay (son of Jean-Baptiste Vermay), José Antonio Cortina, Rafael Fernández de Castro, and Enrique José Varona were all Freemasons in this period. The journal Revista Cubana was edited by José Antonio Cortina, and Revista de Cuba was edited by Enrique José Varona, where, alongside literature and society essays, they published Spanish translations of Charles Darwin and Hegel. Joaquín Fabián Aenlle y Monjiotti, formerly the second-in-command at GOCA, became the Dean of the Faculty of Pharmacology at the University of Havana. Rafael María de Mendive became a personal mentor to a young man named José Martí. In 1886, Spain outlawed slavery in all of its territories. The United Grand Lodge maintained a regular and correct authority until the outbreak of the Cuban War of Independence.
Sources: en.wikipedia.org
Brain natriuretic peptide (BNP), also known as B-type natriuretic peptide, is a peptide hormone secreted by cardiomyocytes in the heart ventricles in response to stretching caused by increased ventricular blood volume. BNP is one of the three natriuretic peptides, in addition to atrial natriuretic peptide (ANP) and C-type natriuretic peptide (CNP). BNP was first discovered in porcine brain tissue in 1988, which led to its initial naming as "brain natriuretic peptide", although subsequent research revealed that BNP is primarily produced and secreted by the ventricular myocardium (heart muscle) in response to increased ventricular blood volume and stretching. To reflect its true source, BNP is now often referred to as "B-type natriuretic peptide" while retaining the same acronym. The 32-amino acid polypeptide BNP-32 is secreted attached to a 76–amino acid N-terminal fragment in the prohormone called NT-proBNP (BNPT), which is biologically inactive. Once released, BNP binds to and activates the atrial natriuretic factor receptor NPRA, and to a lesser extent NPRB, in a fashion similar to atrial natriuretic peptide (ANP) but with 10-fold lower affinity. The biological half-life of BNP, however, is twice as long as that of ANP, and that of NT-proBNP is even longer, making these peptides better targets than ANP for diagnostic blood testing. The physiologic actions of BNP are similar to those of ANP and include decrease in systemic vascular resistance and central venous pressure as well as an increase in natriuresis.
Since their conceptualization in 1998, several advances have been made in terms of the variety of types of microneedles that can be fabricated. The 5 main types of microneedles are solid, hollow, coated, dissolvable/dissolving, and hydrogel-forming. The distinct characteristic of each type of MNs allow a variety of clinical applications, including diagnosis and treatment. Micro-sized needles in a microneedles (MNs) device can be as short as 25μm or even 2000μm in length depending on their types.
The (off-label) upper daily limits for other serotonin-reuptake inhibitors used in the treatment of OCD, by analogy, are 400 mg for sertraline, 100 mg for paroxetine, 120 mg for both fluoxetine and citalopram, 60 mg for escitalopram and 300 mg for clomipramine. In any case with fluvoxamine, treatment is generally begun at 50 mg and increased in 50 mg increments every 4 to 7 days until a therapeutic optimum is reached.
== Isolation and synthesis == Vinblastine may be isolated from the Madagascar Periwinkle (Catharanthus roseus), its only known biological producer, along with several of its precursors, catharanthine and vindoline. Extraction is costly and yields of vinblastine and its precursors are low, although procedures for rapid isolation with improved yields avoiding auto-oxidation have been developed. Enantioselective synthesis has been of considerable interest in recent years, as the natural mixture of isomers is not an economical source for the required C16'S, C14'R stereochemistry of biologically active vinblastine. Initially, the approach depends upon an enantioselective Sharpless epoxidation, which sets the stereochemistry at C20. The desired configuration around C16 and C14 can then be fixed during the ensuing steps. In this pathway, vinblastine is constructed by a series of cyclization and coupling reactions which create the required stereochemistry. The overall yield may be as great as 22%, which makes this synthetic approach more attractive than extraction from natural sources, whose overall yield is about 10%. Stereochemistry is controlled through a mixture of chiral agents (Sharpless catalysts), and reaction conditions (temperature, and selected enantiopure starting materials). Due to difficulty of stereochemical restraints in total synthetic processes, other semi-synthetic methods from precursors, catharanthine and vindoline, continue to be developed.
2 December – Neville Callaghan, 77, racehorse trainer. 5 December – Rosemary Smith, 86, rally driver. 7 December – Thomas Kilroy, 89, playwright and novelist. 10 December Jonathan Irwin, 82, blood stock agent, auctioneer, stud owner, publisher and founder of the Jack and Jill Foundation. Syd Millar, 89, rugby union player (Ballymena, national team), coach (British & Irish Lions) and International Rugby Board chairman (2003–2007). Born in Northern Ireland. Bill McCarthy, 87, hurler (St Brendan's, Ardfert, Kerry junior team, Munster). 11 December – Frank Twomey, 68, children's television entertainer and comedian (Bosco, Bull Island). 16 December – Joseph Finnegan, 81, judge. 17 December – Maureen Flavin Sweeney, 100, postmistress and formerly a weather forecaster notable for advising on the D-Day landings. 20 December – Johnny Flaherty, 76, hurler (Kinnitty, Offaly senior team, Leinster). 21 December – Martin Feeley, 73, Olympic rower (1976) and surgeon. 27 December – Éamonn Draper, 83, actor and director. 28 December – Patrick Walsh, 92, Roman Catholic prelate, bishop of Down and Connor (1991–2008). 30 December – Paddy Murphy, 89, Gaelic footballer (Dromtarriffe, Duhallow, Cork senior team.
Sources: en.wikipedia.org
The Dorothy Hodgkin Quarter, a student accommodation block at Somerville, is named after Hodgkin. British commemorative stamps - Hodgkin was one of five 'Women of Achievement' selected for a set issued in August 1996. The others were Marea Hartman (sports administrator), Margot Fonteyn (ballerina/choreographer), Elisabeth Frink (sculptor) & Daphne du Maurier (writer). All except Hodgkin were Dames Commander of the Order of the British Empire (DBEs). In 2010, during the 350th anniversary of the founding of the Royal Society, Hodgkin was the only woman in a set of stamps celebrating ten of the Society's most illustrious members, taking her place alongside Isaac Newton, Edward Jenner, Joseph Lister, Benjamin Franklin, Charles Babbage, Robert Boyle, Ernest Rutherford, Nicholas Shackleton and Alfred Russel Wallace. The Royal Society awards the Dorothy Hodgkin Fellowship (named in her honour) "for outstanding scientists at an early stage of their research career who require a flexible working pattern due to personal circumstances, such as parenting or caring responsibilities or health-related reasons." The Council offices in the London Borough of Hackney and buildings at University of York, Bristol University and Keele University are named after her, as is the science block at Sir John Leman High School, her former school. In 2012, Hodgkin was featured in the BBC Radio 4 series The New Elizabethans to mark the diamond Jubilee of Queen Elizabeth II.
== Responses to lipid environment == When hydrophobic mismatch occurs, WALPs are known to tilt in the bilayer. The extent of this tilt is affected up to a certain point by an entropy contribution that arises from the helix's presence in the bilayer and then by more specific helix-lipid interactions. When charged residues are substituted for the anchoring residues, these charged amino acids prefer a higher position, farther from the interior of the lipid bilayer, in order to maintain their energetically favorable interaction with water. This interaction thus promotes a smaller angle of tilt.
Incidences of partial recoil occurred at 1-week post-procedure, with no further, significant, breast volume decrease afterwards, nor at the follow-up treatment at 30-weeks post-procedure. The stable, long-term increase in breast size was 55 percent (range 15–115%). The MRI visualizations of the breasts showed no edema, and confirmed the proportionate enlargement of the adipose and glandular components of the breast-tissue matrices. Furthermore, a statistically significant decrease in body weight occurred during the study, and self-esteem questionnaire scores improved from the initial-measure scores. Because external vacuum expansion of the recipient-site tissues permits injecting large-volume fat grafts (+300 cc) to correct defects and enhance the bust, the histologic viability of the breast filler (adipocyte fat) and its volume must be monitored and maintained. The long-term, volume maintenance data reported in Breast Augmentation using Pre-expansion and Autologous Fat Transplantation: a Clinical Radiological Study (2010) indicate the technical effectiveness of external tissue expansion of the recipient site for a 25-patient study group, who had 46 breasts augmented with fat grafts. The indications included micromastia (underdevelopment), explantation deformity (empty implant pocket), and congenital defects (tuberous breast deformity, Poland's syndrome).
Docetaxel (DTX or DXL), sold under the brand name Taxotere among others, is a chemotherapy medication used to treat a number of types of cancer. This includes breast cancer, head and neck cancer, stomach cancer, prostate cancer and non-small-cell lung cancer. It may be used by itself or along with other chemotherapy medication. It is given by slow injection into a vein. Common side effects include hair loss, cytopenia (low blood cell counts), numbness, shortness of breath, nausea, vomiting, and muscle pains. Other severe side effects include allergic reactions and future cancers. Docetaxel-induced pneumotoxicity is also a well recognized adverse effect which has to be identified timely and treated after withholding the drug. Side effects are more common in people with liver problems. Use during pregnancy may harm the fetus. Docetaxel is in the taxane family of medications. It works by disrupting the normal function of microtubules and thereby stopping cell division. Docetaxel was patented in 1986 and approved for medical use in 1995. It is on the World Health Organization's List of Essential Medicines. Docetaxel is available as a generic medication.
Silent mutations alter the secondary structure of mRNA. Secondary structure of proteins consists of interactions between the atoms of the backbone of a polypeptide chain, excluding the R-groups. One common type of secondary structures is the alpha helix, which is a right-handed helix that results from hydrogen bonds between the nth amino acid residue and the n+4th amino acid residue. The other common type of secondary structure is the beta sheet, which displays a right-handed twist, can be parallel or anti-parallel depending on the direction of the direction of the bonded polypeptides, and consists of hydrogen bonds between the carbonyl and amino groups of the backbone of two polypeptide chains. mRNA has a secondary structure that is not necessarily linear like that of DNA, thus the shape that accompanies complementary bonding in the structure can have significant effects. For example, if the mRNA molecule is relatively unstable, then it can be rapidly degraded by enzymes in the cytoplasm. If the RNA molecule is highly stable, and the complementary bonds are strong and resistant to unpacking prior to translation, then the gene may be under expressed. Codon usage influences mRNA stability. Furthermore, since all organisms contain a slightly different genetic code, their mRNA structures differ slightly as well, however, multiple studies have been conducted that show that all properly folded mRNA structures are dependent on the primary sequence of the polypeptide chain and that the structure is maintained by dinucleotide relative abundances in the cell matrix.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide modelled on alpha-melanocyte-stimulating hormone. A lactam bridge links two side chains, forming a ring that stabilises the molecule against proteolysis. It belongs to the broader melanocortin peptide family.
No national medicines agency has approved melanotan-2 for clinical use. Afamelanotide, a related but distinct peptide, holds a marketing authorisation in the European Union for a rare photosensitivity disorder. Melanotan-2 itself is handled as a laboratory chemical.
Its broad activity across melanocortin receptors makes it a tool for probing pigmentation, appetite and vascular signalling. Early trials recorded skin darkening and other effects that were not the original focus of the work. Those observations generated hypotheses that later studies have examined.
Solutions are best kept cold, protected from light, and buffered to a pH that limits hydrolysis. Dividing a stock into single-use aliquots avoids repeated freeze-thaw cycles, which measurably reduce the intact parent peak over time.