MC4 receptor is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2025-09-26. Numbers and descriptions here follow the published literature rather than marketing material.
Across literature and commercial listings, the substance appears under several names, including bremelanotide, PT-141, and various brand designations. A CAS registry number provides a unique identifier for the compound, aiding retrieval from chemical databases. Synonym lists may also contain early development codes and descriptive chemical names. When consulting sources, researchers need to confirm that the cited names refer to the same molecular structure to avoid confusion. Naming consistency matters especially when comparing analytical data across publications.
PT-141 is a synthetic cyclic heptapeptide whose development code is bremelanotide. It belongs to the class of melanocortin receptor agonists and acts by mimicking endogenous peptide hormones. The compound originated from research on melanotan II, where investigators exploring derivatives found distinct pharmacological features. Unlike the parent compound, PT-141 showed effects on pathways related to sexual desire and function in early studies, prompting its development as a separate candidate. Its molecular design aimed to separate receptor activity from pigmentary effects.
Whether the behavioral effect originates centrally, peripherally, or through both remains an active question. Animal experiments using receptor antagonists and site-specific injections point toward hypothalamic melanocortin circuits as a key locus, but translating those findings to humans is not straightforward. Blood pressure changes observed in trials suggest a vascular component that may be peripherally mediated. The relationship between receptor occupancy and reported effect has not been mapped in humans, and no validated biomarker predicts response. This gap makes it difficult to explain individual variability on pharmacological grounds alone.
Bremelanotide acts as an agonist at melanocortin receptors, a family of five G-protein-coupled receptors labeled MC1 through MC5. Binding studies indicate activity at several of these subtypes rather than strict selectivity for one. Signalling proceeds mainly through Gs-mediated activation of adenylyl cyclase, raising intracellular cyclic AMP. The MC4 receptor, expressed in hypothalamic and limbic circuits, is widely regarded as the subtype most relevant to sexual response. Because the molecule is not subtype-selective, effects at other melanocortin receptors are expected and are used to explain some observed side effects.
The peptide contains seven amino acids arranged in a ring, closed by a lactam bridge between a side-chain acid and an amine. This cyclic constraint holds the backbone in a defined conformation and increases resistance to enzymatic breakdown relative to linear analogs. N-terminal acetylation and a C-terminal amide further protect the molecule from exopeptidases. The result is a compound with a comparatively long circulation time for a small peptide. Structural modification of the bridge alters receptor affinity, which is one reason analogs in this family differ in their subtype preferences.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Cyclic peptide | Melanocortin receptor agonist family |
| Molecular weight | Approximately 1025 Da | Free base form |
| Appearance | White to off-white powder | Lyophilized product |
| Solubility | Soluble in water | Also dissolves in polar organic solvents |
| Storage temperature | -20 degrees Celsius | Dry and protected from light |
Published studies differ in design, population and endpoint definition, so results are not always directly comparable across reports. Some trials used patient-reported measures of desire and distress, while others tracked physiological or behavioural outcomes. Questions that remain open include the durability of effects beyond short follow-up periods, the frequency of transient blood pressure elevation observed after administration, and whether a subtype-selective analogue could separate central effects from pigmentation-related activity. These points are usually framed as unresolved rather than settled in review literature.
Routine characterisation of bremelanotide relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nm, where the peptide backbone absorbs. Mass spectrometry, typically in tandem mode with electrospray ionisation, confirms identity and supports quantification in biological matrices. Additional checks include amino acid analysis, peptide mapping after enzymatic digestion, and confirmation of the lactam bridge, since incomplete cyclisation produces a mass-shifted by-product. Purity values above 95 percent are common in reference-grade material, though reports vary in how strictly related substances are resolved from the parent peak.
The lyophilised solid is relatively stable when kept dry, protected from light and held at reduced temperature, commonly minus 20 degrees Celsius or lower for long-term storage. In solution the peptide is more vulnerable: tryptophan oxidation, hydrolysis of the lactam bridge and aggregation all become relevant over time, and the rate depends on pH, buffer composition and concentration. Repeated freeze-thaw cycles are generally avoided because they promote aggregation. Aqueous working solutions are typically prepared fresh or split into single-use aliquots to limit degradation before analysis.
Bremelanotide acts as a non-selective agonist at melanocortin receptors, with reported activity at MC1R, MC3R, MC4R and MC5R. The proposed basis for its central effects is activation of MC4R populations in the hypothalamus, a region associated with appetite and reproductive signalling. Because the peptide carries a net positive charge and polar side chains, it does not cross biological membranes freely, which is one reason oral administration is not the standard route. Effects generally appear within an hour of parenteral administration and are described as centrally mediated rather than peripheral.
Bremelanotide, developed under the code PT-141, is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone. Its structure is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, with a lactam bridge joining the aspartate and lysine side chains. The molecule has the formula C50H68N14O10 and a monoisotopic mass near 1025 daltons. It is commonly prepared as the acetate salt and appears as a white to off-white lyophilised powder in solid form. The free acid is the pharmacologically relevant species, while the counter-ion improves handling and dissolution.
Early research on PT-141 grew out of work on melanotan II, a related cyclic peptide studied for pigmentation. Investigators observed that centrally acting melanocortin agonists also influenced sexual behaviour in animal models, and the programme shifted toward that endpoint. A nasal formulation was evaluated in clinical trials but showed inconsistent absorption, and later studies used subcutaneous administration instead. Regulatory approval in the United States followed in 2019 for a defined population of premenopausal women with acquired, generalised hypoactive sexual desire disorder. That approval was specific to that group rather than a broad indication.
Certificate of analysis documents usually report purity percentage, molecular weight, and appearance. Researchers verify identity by comparing observed and theoretical mass values. Chain-of-custody records and batch numbers help trace material from source to experiment. Independent verification of supplier claims is considered good practice when material identity is critical to a study. Records should include the storage history of each aliquot, and unexpected deviations in appearance or solubility warrant re-testing before use.
Lyophilized peptide material is generally stored at -20 °C or below to limit degradation, while reconstituted solutions are less stable and are typically kept refrigerated and protected from light. Repeated freeze-thaw cycles can accelerate aggregation and should be minimized. Stability for any specific lot depends on purity, moisture content, and packaging. Handling in a temperature-controlled environment reduces variability across replicates, and exposure to ambient humidity during weighing can introduce error. Aliquotting reduces the number of times a stock container is opened.
Reverse-phase high-performance liquid chromatography is the standard method for assessing purity. Mass spectrometry confirms molecular identity and detects sequence variants or truncation products. Ultraviolet absorbance at 214 or 280 nm is used for quantification, with the choice depending on the peptide sequence. Method validation typically addresses linearity, limit of detection, and precision across a defined concentration range. Impurity profiling may also employ ion-exchange or size-exclusion chromatography, and these techniques complement one another.
==== Polyol process ==== The polyol process is a particularly useful method because it yields a high degree of control over both the size and geometry of the resulting nanoparticles. In general, the polyol synthesis begins with the heating of a polyol compound such as ethylene glycol, 1,5-pentanediol, or 1,2-propylene glycol7. An Ag+ species and a capping agent are added (although the polyol itself is also often the capping agent). The Ag+ species is then reduced by the polyol to colloidal nanoparticles. The polyol process is highly sensitive to reaction conditions such as temperature, chemical environment, and concentration of substrates. Therefore, by changing these variables, various sizes and geometries can be selected for such as quasi-spheres, pyramids, spheres, and wires. Further study has examined the mechanism for this process as well as resulting geometries under various reaction conditions in greater detail.
Manchester United defeat Manchester City 2–1 to win the 2024 FA Cup final. 26 May – British event rider Georgie Campbell dies after falling from her horse at the Bicton International Horse Trials in Devon. 27 May 2024 general election: Lucy Allan, outgoing Conservative MP for Telford is suspended from her party for backing Alan Adams, the Reform UK candidate to be her replacement. The RAF temporarily grounds its Spitfire planes following the fatal crash two days earlier. The FBI is reported to be investigating the sale of hundreds of British Museum artefacts to buyers in the United States. 28 May – Diane Abbott is readmitted as a Labour MP, following her suspension the previous year. 30 May 2024 general election: The Parliament elected in 2019 is dissolved. Buckingham Palace confirms that Charles III will attend the 2024 Trooping the Colour ceremony. 31 May – BBC News reports that the Battle of Britain Memorial Flight will not fly as part of D-Day anniversary events following the death of Squadron Leader Mark Long.
The epidermis and dermis are separated by a thin sheet of fibers called the basement membrane, which is made through the action of both tissues. The basement membrane controls the traffic of the cells and molecules between the dermis and epidermis but also serves, through the binding of a variety of cytokines and growth factors, as a reservoir for their controlled release during physiological remodeling or repair processes.
== Sources == This article incorporates text from a free content work. Licensed under CC BY 4.0 (license statement/permission). Text taken from World Food and Agriculture – Statistical Yearbook 2025, Food and Agriculture Organization of the United Nations. This article incorporates text from a free content work. Licensed under CC BY 4.0 (license statement/permission). Text taken from The State of Food Security and Nutrition in the World 2026, Food and Agriculture Organization of the United Nations.
As of September 2022, 163 members, or 46.7% of the 349 members are women. Five parties have a majority representation of female MPs as of 2022: the Left Party (17 of 24, 70.8%), the Green Party (12 of 18, 66.7%), the Liberals (9 of 16, 56.3%), the Centre Party (13 of 24, 54.2%), and the Social Democratic Party (55 of 107, 51.4%). The party with the lowest share of female MPs is the Sweden Democrats (18 of 73, 24.7%). Members of the Riksdag are full-time legislators with a base remuneration of SEK 81,400 per month, as of 1 January 2026. Committee chairs receive an additional 20% and deputy chairs receive an additional 15%. According to a survey investigation by the sociologist Jenny Hansson, Members of the Riksdag have an average work week of 66 hours, including side responsibilities. Hansson's investigation further reports that the average member sleeps 6.5 hours per night.
Sources: en.wikipedia.org
The grouping consistent with transfer of nitrogenous groups is EC 2.6. This includes enzymes like transaminase (also known as "aminotransferase"), and a very small number of oximinotransferases and other nitrogen group transferring enzymes. EC 2.6 previously included amidinotransferase but it has since been reclassified as a subcategory of EC 2.1 (single-carbon transferring enzymes). In the case of aspartate transaminase, which can act on tyrosine, phenylalanine, and tryptophan, it reversibly transfers an amino group from one molecule to the other. The reaction, for example, follows the following order: L-aspartate +2-oxoglutarate
=== Making use of the differences === The differences between the bacterial and eukaryotic ribosomes are exploited by pharmaceutical chemists to create antibiotics that can destroy a bacterial infection without harming the cells of the infected person. Due to the differences in their structures, the bacterial 70S ribosomes are vulnerable to these antibiotics while the eukaryotic 80S ribosomes are not. Even though mitochondria possess ribosomes similar to the bacterial ones, mitochondria are not affected by these antibiotics because they are surrounded by a double membrane that does not easily admit these antibiotics into the organelle. A noteworthy counterexample is the antineoplastic antibiotic chloramphenicol, which inhibits bacterial 50S and eukaryotic mitochondrial 50S ribosomes. Ribosomes in chloroplasts, however, are different: Antibiotic resistance in chloroplast ribosomal proteins is a trait that has to be introduced as a marker, with genetic engineering.
The treatment of slaves in the United States varied widely depending on conditions, times, and places. The power relationships of slavery corrupted many whites who had authority over slaves, with children showing their own cruelty. Masters and overseers resorted to physical punishments to impose their wills. Slaves were punished by whipping, shackling, hanging, beating, burning, mutilation, branding and imprisonment. Punishment was most often meted out in response to disobedience or perceived infractions, but sometimes abuse was carried out to re-assert the dominance of the master or overseer of the slave. Treatment was usually harsher on large plantations, which were often managed by overseers and owned by absentee slaveholders. William Wells Brown, who escaped to freedom, reported that on one plantation, slave men were required to pick 80 pounds (36 kg) of cotton per day, while women were required to pick 70 pounds (32 kg) per day; if any slave failed in their quota, they were subject to whip lashes for each pound they were short. The whipping post stood next to the cotton scales. A New York man who attended a slave auction in the mid-19th century reported that at least three-quarters of the male slaves he saw at sale had scars on their backs from whipping. By contrast, small slave-owning families had closer relationships between the owners and slaves; this sometimes resulted in a more humane environment but was not a given.
== In culture == Black peppercorns were found stuffed in the nostrils of Ramesses II, placed there as part of the mummification rituals shortly after his death in 1213 BCE. Little else is known about the use of pepper in ancient Egypt and how it reached the Nile from the Malabar Coast of India.
{\displaystyle {\begin{array}{lll}M({\ce {NaCl}})&=[22.98976928(2)+35.453(2)]\times M_{\text{u}}\\&=58.443(2){\text{ g/mol}}\\M({\ce {C12H22O11}})&=[12\times 12.0107(8)+22\times 1.00794(7)+11\times 15.9994(3)]\times M_{\text{u}}\\&=342.297(14){\text{ g/mol}}\end{array}}}
Sources: en.wikipedia.org
== Career == In December 1986, Cameron joined the Department of Chemical Engineering at the University of Wisconsin—Madison, as an assistant professor and advanced to full professor. The focus of his research was metabolic engineering (a field now more commonly known as synthetic biology) and industrial microbiology. One of his first projects was the engineering of the microbial pathway for 1,3-propanediol in Escherichia coli. This work was an early step in a process that was eventually commercialized by DuPont and Tate & Lyle. He is also the inventor of a process for the microbial production of 3-hydroxypropionic acid, which provides a bio-based route to industrial chemicals such as acrylic acid. In 1996 he did a sabbatical at the ETH Zurich (Switzerland) in the laboratory of James (Jay) E. Bailey. In 1998 he took a leave of absence to start the Biotechnology Development Center (BioTDC) at Cargill, Inc. in Minneapolis. In 2000 he officially left the University of Wisconsin. Cameron was at Cargill, Inc. from 1998 to 2006, where he was Director of Biotechnology and chief scientist. While at Cargill he worked closely with NatureWorks on the development of a low-pH process for lactic acid as a feedstock for polylactic acid. He and his team also worked with Cargill Ventures on deal-sourcing and due-diligence. In June 2006, Cameron moved from Cargill to join the newly formed Silicon Valley venture capital firm, Khosla Ventures, as chief scientific officer. In 2008, Cameron returned to the Midwest to help Piper Jaffray build and grow its clean tech investment business.
Seaborg was notified and the team left to sleep. Additional analysis and further experimentation showed the produced mendelevium isotope to have the expected mass of 256 and decay by electron capture to fermium-256 (half-life 157.6 minutes), the source of the observed fission.
=== Activation === PAR1 is activated when the terminal 41 amino acids of its N-terminus are cleaved by thrombin, a serine protease. Thrombin recognizes PAR1 by a Lysine-Aspartate-Proline-Arginine-Serine sequence at the N-terminal, where it cuts the peptide bond between Arginine-41 and Serine-42. The affinity of thrombin to this specific cleavage site in PAR1 is further aided by secondary interactions between thrombin's exosite and an acidic region of amino acid residues located C-terminal to Ser-42. This proteolytic cleavage is irreversible and the loose peptide, often referred to as parstatin, is then released outside of the cell. The newly revealed N-terminus acts as a tethered ligand that binds to a binding region between extracellular loops 3 and 4 of PAR1, therefore activating the protein. The binding instigates conformational changes in the protein that ultimately allow for the binding of G-proteins to sites on the intracellular region of PAR1.
The nervous system is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body. In vertebrates it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to all remaining body parts. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves.
=== Seizures === Phenobarbital is used in the treatment of all types of seizures, except absence seizures. It is no less effective at seizure control than phenytoin, but phenobarbital is not as well tolerated. Phenobarbital may provide a clinical advantage over carbamazepine for treating partial seizures. Carbamazepine may provide a clinical advantage over phenobarbital for generalized tonic–clonic seizures. The first-line drugs for treatment of status epilepticus are benzodiazepines, such as lorazepam, clonazepam, midazolam, or diazepam. If these fail, then phenytoin may be used, with phenobarbital being an alternative in the US (favored in infants), but used only third-line in the UK. Failing that, the only treatment is anesthesia in intensive care. The World Health Organization (WHO) gives phenobarbital a first-line recommendation in the developing world and it is commonly used there. Phenobarbital is the first-line choice for the treatment of neonatal seizures. Concerns that neonatal seizures in themselves could be harmful make most physicians treat them aggressively. However, no reliable evidence supports this approach.
Sources: en.wikipedia.org
It belongs to the melanocortin receptor agonist family of peptides. Its cyclic structure distinguishes it from linear peptides and shapes its receptor binding profile.
It emerged from research on melanotan II. Investigators exploring derivatives observed distinct pharmacological features related to sexual function.
Common names include bremelanotide and PT-141. Chemical databases may also list early development codes and descriptive names.
It is frequently described as an MC4 receptor agonist, but binding assays show activity at more than one melanocortin subtype. Selectivity is therefore relative rather than absolute. This matters when interpreting side effects tied to other receptor subtypes.