This is a working overview of Cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-09-06. Anything still debated is marked as such rather than presented as settled.
Handling procedures emphasize minimizing moisture uptake, since the dried solid is hygroscopic and can draw water when warmed to room temperature before a vial is opened. Laboratories record lot number, purity, counter-ion content, and residual solvent data supplied by the producer. Impurity profiles are compared run to run, and any shift in retention time or peak shape prompts re-verification against a reference standard. Certificates of analysis are treated as claims to be checked rather than accepted at face value.
Identity and purity testing for this peptide typically relies on reversed-phase high-performance liquid chromatography with ultraviolet detection, reported as area-percent purity. Mass spectrometry, usually in tandem mode, confirms molecular mass and supports quantification in biological matrices. Sequence confirmation may use peptide mapping after enzymatic digestion, while nuclear magnetic resonance and circular dichroism supply supplementary structural detail. No single technique establishes identity alone, so laboratories compare retention time, mass, and fragment pattern against a verified reference standard.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white solid | Lyophilized powder form |
| Solubility class | Freely soluble in water | Also dissolves in polar organic solvents |
| Typical storage temperature | Minus 20 degrees Celsius or lower | Desiccated and protected from light |
| Typical analytical method | Reversed-phase HPLC with UV detection | Purity reported by area normalization |
| Common synonyms | PT-141; bremelanotide | Research code and assigned generic name |
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.
Bremelanotide is a cyclic heptapeptide that binds several melanocortin receptors rather than one. In vitro assays report agonist activity at MC1R, MC3R, MC4R and MC5R, with MC4R generally treated as the subtype most relevant to sexual effects. MC4R is expressed in hypothalamic nuclei involved in appetite, energy balance and motivated behaviour, which provides a plausible route for central action. Selective MC4R agonists studied in animals produce comparable behavioural changes, supporting that interpretation.
How receptor activation translates into a change in desire is not established in detail. Proposed steps include modulation of dopaminergic signalling in reward circuits and downstream effects on autonomic tone. Human data consist mainly of clinical trials measuring self-reported outcomes rather than direct measurements of brain activity or transmitter release. The transient rise in blood pressure sometimes observed after administration is likewise reported consistently but explained only partly by known melanocortin pathways.
Melanocortin receptors form a family of five G-protein-coupled proteins, labelled MC1R through MC5R, that respond to peptides derived from pro-opiomelanocortin. Alpha-melanocyte-stimulating hormone and adrenocorticotropic hormone are the best-known endogenous ligands. The receptors are distributed differently across tissues, so a single agonist can produce effects in the brain, skin, adrenal gland and vasculature. This distribution explains why one peptide can influence both pigmentation and motivated behaviour.
Development of the peptide passed through several delivery formats, including an intranasal version tested in early trials and an injectable version that entered later clinical study. Regulatory approval for a subcutaneous product in the United States was granted in 2019 after review of controlled trials in premenopausal women. Outside the clinic, the compound circulates in research and non-pharmaceutical markets under its code name, where identity and purity vary considerably between suppliers. Synonyms appearing across technical literature include bremelanotide, PT-141, and Palatin 141.
PT-141 is the research designation for bremelanotide, a synthetic cyclic heptapeptide developed as a melanocortin receptor agonist. The peptide contains seven amino acids with an internal lactam bridge that constrains the backbone into a stable ring. Cyclisation of this kind improves resistance to enzymatic degradation relative to linear analogues. The compound was first explored for effects on melanin production, because several melanocortin receptors influence pigmentation. Its later association with sexual desire emerged from observations made during that early work, and the molecule became the subject of a separate development programme.
After subcutaneous administration, plasma concentrations rise within roughly thirty minutes and the elimination half-life is short, on the order of two to three hours. Reported physiological responses include transient increases in blood pressure and nausea, which tended to diminish with repeated dosing in trial settings. Because the peptide clears quickly, effects are not expected to persist long after a dose. Absorption from non-injected routes is poorly characterised, and nasal delivery produced variable plasma levels in older work.
Clinical research typically uses randomised, double-blind, placebo-controlled designs. The most common primary endpoint is the desire domain score of the Female Sexual Function Index, sometimes paired with a distress measure. Secondary outcomes include arousal, satisfaction, and event-based counts of satisfying sexual episodes. Across trials, average improvements are modest and individual responses vary widely. Whether benefits persist beyond a few months, and whether they depend on baseline hormone status, remain open questions rather than settled findings.
=== Other nonspecific signs === Some signs that may be present include changes in the nails (such as Muehrcke's lines, Terry's nails, and nail clubbing). Additional changes may be seen in the hands (Dupuytren's contracture) as well as the skin/bones (hypertrophic osteoarthropathy).
== Utility in prediction == The utility of the criteria in determining the prognosis of patients with acute liver failure is defined by their operating characteristics. The positive predictive value of the criteria in predicting death from acute liver failure has ranged from 70% to 100%. A Canadian meta-analysis assessing various prognostic indices found that the specificity of the King's College criteria in predicting mortality exceeded 90%, with a sensitivity of 69%. As a result, the American Society for Study of Liver Diseases has recommended the King's College Criteria as being helpful early parameters in ascertaining the need for liver transplantation in patients with acute liver failure.
He was initiated into the Tau chapter of Alpha Chi Sigma at Cornell in 1949. At Cornell he elaborated and refined his Baker Lectures into his magnum opus, Principles of Polymer Chemistry which was published in 1953 by Cornell University Press. This quickly became a standard text for all workers in the field of polymers, and is still widely used to this day. Flory introduced the concept of excluded volume, coined by Werner Kuhn in 1934, to polymers. Excluded volume refers to the idea that one part of a long chain molecule can not occupy space that is already occupied by another part of the same molecule. Excluded volume causes the ends of a polymer chain in a solution to be further apart (on average) than they would be were there no excluded volume. The recognition that excluded volume was an important factor in analyzing long-chain molecules in solutions provided an important conceptual breakthrough, and led to the explanation of several puzzling experimental results of the day. It also led to the concept of the theta point, the set of conditions at which an experiment can be conducted that causes the excluded volume effect to be neutralized. At the theta point, the chain reverts to ideal chain characteristics – the long-range interactions arising from excluded volume are eliminated, allowing the experimenter to more easily measure short-range features such as structural geometry, bond rotation potentials, and steric interactions between near-neighboring groups.
Bush publicly condemned Kim Jong-il of North Korea and identified North Korea as one of three states in an "axis of evil". He said that "the United States of America will not permit the world's most dangerous regimes to threaten us with the world's most destructive weapons." Within months, "both countries had walked away from their respective commitments under the U.S.–DPRK Agreed Framework of October 1994." North Korea's October 9, 2006, detonation of a nuclear device further complicated Bush's foreign policy, which centered for both terms of his presidency on "[preventing] the terrorists and regimes who seek chemical, biological, or nuclear weapons from threatening the United States and the world". Bush condemned North Korea's position, reaffirmed his commitment to "a nuclear-free Korean Peninsula", and said that "transfer of nuclear weapons or material by North Korea to states or non-state entities would be considered a grave threat to the United States", for which North Korea would be held accountable. On May 7, 2007, North Korea agreed to shut down its nuclear reactors immediately pending the release of frozen funds held in a foreign bank account. This was a result of a series of three-way talks initiated by the United States and including China. On September 2, 2007, North Korea agreed to disclose and dismantle all its nuclear programs by the end of 2007. By May 2009, North Korea had restarted its nuclear program and threatened to attack South Korea.
Through the late 1950s and early 1960s, numerous papers were published on various topics in RNA structure, including RNA-DNA hybridization, triple stranded RNA, and even small-scale crystallography of RNA di-nucleotides—G-C, and A-U—in primitive helix-like arrangements. For a more in-depth review of the early work in RNA structural biology, see the article The Era of RNA Awakening: Structural biology of RNA in the early years by Alexander Rich.
Sources: en.wikipedia.org
The initial product from the hydrolysis reaction is de-watered and further processed by dry cracking at 500 °C. The "SlurryCarb" process operated by EnerTech uses similar technology to decarboxylate wet solid biowaste, which can then be physically dewatered and used as a solid fuel called E-Fuel. The plant at Rialto is said to be able to process 683 tons of waste per day.
== Effects and properties == The effects of argiotoxin, when it enters an organism by a spider bite, are harmless to humans, although in certain cases the bite of argiotoxin spiders can produce mild swelling and itching. Argiotoxin antagonizes the actions of the neurotransmitter glutamate, blocks the functioning of ion channel and affects the synaptic transmission of preys. These toxins, like all the other low-molecular-weight toxins, have a huge potential to be used in neurochemical studies to develop novel drugs of neurotherapeutic applications.
Barry Windsor-Smith, who had come to prominence illustrating Marvel's Conan the Barbarian series, collaborated with Claremont for the "Wounded Wolf" story that was published as Uncanny X-Men #205 (May 1986), focusing entirely on Wolverine. The story introduced a new adversary for Wolverine, Lady Deathstrike. The "Mutant Massacre" story arc of 1986 brought Sabretooth into conflict with the X-Men and particularly Wolverine. Byrne had previously designed Sabretooth as an enemy of the martial artist superhero Iron Fist in Iron Fist #14 (August 1977), written by Claremont. Sabretooth's face was based on a preliminary and unused drawing Byrne had proposed for Wolverine; he became Wolverine's archenemy. Marvel launched an ongoing Wolverine title written by Claremont with art by John Buscema in November 1988. In the late 1980s, Wolverine featured in self-contained crossover stories with two other characters: Spider-Man, in Spider-Man versus Wolverine (1987), by Christopher Priest and M.D. Bright, and Nick Fury, in Wolverine/Nick Fury: The Scorpio Connection (1989), written by Archie Goodwin with art by Howard Chaykin.
Stanley Airport is used by internal flights and provides connections to British bases in Antarctica. Flights to Argentina ended after the 1982 conflict. A weekly flight to Punta Arenas in Chile commenced in 1993, which now operates out of RAF Mount Pleasant. Scheduled passenger flights between the Mount Pleasant airfield and the UK are also operated twice a week by a civilian airline contractor on behalf of the Royal Air Force. Stanley was occupied by Argentine troops for about 10 weeks during the Falklands War in 1982. The Argentinians renamed the town Puerto Argentino, and although Spanish names for places in the Falklands were historically accepted as alternatives, this one is considered to be extremely offensive by many islanders. Stanley suffered considerable damage during the war, from both the Argentine occupation and the British naval shelling of the town, which killed three civilians. After the British secured the high ground around the town the Argentines surrendered with no fighting in the town itself. The beaches and land around it were heavily mined and some areas remain marked minefields. Since the Falklands War, Stanley has benefited from the growth of the fishing and tourism industries in the Islands. Stanley itself has developed greatly in that time, with the building of a large amount of residential housing, particularly to the east of the town centre. Stanley is now more than a third bigger than it was in 1982.
=== Metabolic and covalent labeling of glycans === Metabolic labeling of glycans can be used as a way to detect glycan structures. A well known strategy involves the use of azide-labeled sugars which can be reacted using the Staudinger ligation. This method has been used for in vitro and in vivo imaging of glycans.
Sources: en.wikipedia.org
Produced by Mike Tomlinson, made by Orlando Television Productions with WGBH 21 October The Mind Benders, in May 1991, the Broadcasting Complaints Commission, ruled that this episode should have been broadcast under the title Open Mind; about the Hemi-Sync method; the Float Centre, in St John's Wood with Samantha O'Connor, which cost £22 an hour; Peter Fenwick and flotation tanks; the EEG Mind Mirror of Geoffrey Blundell; the voice of Robert Monroe, and a hemi-sync session in Cambridge, where 200hz is played in one ear, and 206hz in the other ear; a so-called mind gymnasium in Japan, launched in 1975; Australian psychologist Dorothy Rowe, who questioned the veracity of the methods, which could be explained through the placebo effect, which is often not an unimportant effect on health. Narrated by Peter Jones, produced by Patrick Uden, directed by Gary Burczak, made by Uden Associates. Much of the techniques demonstrated were not dissimilar to techniques advocated by the 1990s Natural Law Party 28 October The Winning Streak, about East German methods in women athletics; with Katrin Krabbe. Narrated by Tony Ward, produced by Mike Johnstone, directed by Nikolas L.
Another prospective cohort study on a sample of 79 coronary patients spanning in excess of 12 years found improved metrics of physical endurance, circadian rhythm, and carbohydrate and lipid metabolism in the treated group relative to the control group following 3 years of biannual epithalamin treatments, as well as a 50% lower rate of cardiovascular mortality, a 50% lower rate of cardiovascular failure and serious respiratory disease, and a 28% lower rate of overall mortality.
Naloxone works by temporarily blocking the effects of opioids, including respiratory depression and sedation. Naloxone is safe and side effects are rare, generally limited to allergic reactions. It should be given if there is any suspicion of an opioid overdose. Naloxone is available to the public in the United States in two routes of administration: intranasal and intramuscular/subcutaneous. Intranasal forms include Narcan, approved in 2015, and Kloxxado, approved in 2021. Formulations that are injectable into the intramuscular or subcutaneous spaces include Evzio, approved in 2014, and Zimhi, approved in 2021. The doses are approved for both children and adults and may be repeated every 2–3 minutes. Synthetic opioids like fentanyl and carfentanil are much more potent than prescription opioids and heroin. There is some debate about whether increased doses of naloxone are required to reverse overdose from synthetic opioids; however, this concern has prompted FDA approval of higher dose naloxone formulations such as Kloxxado and Zimhi. The effects of naloxone last for approximately 30-90 minutes, at which point opioids present in the body may begin to take effect again depending on the specific opioids duration of action. Therefore, transport to a hospital is indicated after naloxone administration, and the medication may need to be re-administered.
CAT was acquired by AstraZeneca, who also acquired MedImmune, combining the two into a biologics division. MedImmune renamed CAT-8015 to moxetumomab pasudotox. On 16 May 2013, AstraZeneca announced that CAT-8015 had started Phase III clinical trials.
Sources: en.wikipedia.org
Chemical degradation such as hydrolysis and oxidation proceeds more slowly as temperature falls. Cold storage also limits microbial growth in reconstituted material. Repeated warming should be avoided because thermal cycling stresses the peptide.
Retention time supports consistency but does not establish structure by itself. A different compound can elute at a similar time under one set of conditions. Mass spectrometry or comparison with a verified standard is normally required alongside the chromatographic result.
The lactam bridge constrains the peptide backbone and limits attack by some exopeptidases. It does not protect against hydrolysis of amide bonds inside the ring or against oxidative modification of susceptible residues. Stability therefore still depends heavily on storage conditions.
It belongs to the melanocortin receptor agonist family of peptides. Its cyclic structure distinguishes it from linear peptides and shapes its receptor binding profile.