The short version of Cyclic heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-08-06 and is reviewed periodically as new material appears.
The lactam ring that closes the peptide backbone improves resistance to exopeptidase attack, but the molecule stays susceptible to hydrolysis and oxidation once dissolved. Degradation accelerates with temperature, extreme pH, and light exposure, and repeated freeze-thaw cycles promote aggregation and material loss. Lyophilized powder held desiccated at or below minus twenty degrees Celsius is the common way to keep reference material. Reconstituted solutions are generally kept cold and used within a short window because their stability is far lower than that of the dry solid.
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.
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.
| 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 |
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.
Receptor activation in hypothalamic and limbic circuits is the mechanism most often cited for the observed effects on sexual desire. Signalling through MC4R couples to Gs proteins and raises intracellular cyclic AMP, which in turn modulates dopaminergic tone in reward-related pathways. Because the peptide reaches the central nervous system after subcutaneous administration, peripheral vascular changes are regarded as secondary rather than primary. The precise neural circuits that translate receptor occupancy into behavioural change remain incompletely mapped, and published accounts describe the pathway in general terms rather than as a fully resolved sequence.
Development began with intranasal formulations investigated for erectile dysfunction, but blood pressure elevation limited that route and prompted a switch to subcutaneous delivery. Clinical testing then shifted toward hypoactive sexual desire disorder in premenopausal women, and a subcutaneous product received United States approval in 2019. Later trials examined other populations with mixed results, and questions about effect size, durability and patient selection remain open in the peer-reviewed literature. Research interest continues in parallel with the broader melanocortin field, where several synthetic analogues are studied together.
PT-141 is the research code for bremelanotide, a cyclic heptapeptide derived from alpha-melanocyte-stimulating hormone. The molecule belongs to the melanocortin receptor agonist family and shows highest affinity for the MC4 receptor subtype, with weaker activity at MC1, MC3 and MC5. Its structure retains the core His-Phe-Arg-Trp sequence that defines melanocortin recognition, while cyclization and terminal modifications improve metabolic stability relative to the parent hormone. Early work classified the compound as a centrally acting agent rather than a peripherally acting vasodilator, which shaped subsequent development priorities.
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.
Tramadol is metabolised in the liver via the cytochrome P450 isozyme CYP2B6, CYP2D6, and CYP3A4, being O- and N-demethylated to five different metabolites. Of these, desmetramadol (O-desmethyltramadol) is the most significant, since it has 200 times the μ-affinity of (+)-tramadol, and furthermore has an elimination half-life of 9 hours, compared with 6 hours for tramadol itself. As with codeine, in the 6% of the population who have reduced CYP2D6 activity (hence reducing metabolism), a reduced analgesic effect is seen. Those with decreased CYP2D6 activity require a dose increase of 30% to achieve the same degree of pain relief as those with a normal level of CYP2D6 activity. Phase II hepatic metabolism renders the metabolites water-soluble, which are excreted by the kidneys. Thus, reduced doses may be used in renal and hepatic impairment. Its volume of distribution is around 306 L after oral administration and 203 L after parenteral administration.
=== Traditional and religious leaders === Brigadier-General Sa'adu Abubakar – Sultan of Sokoto. Ibrahim Dabo – Emir of Kano (1819–46). Muhammadu Attahiru I - The last independent Sultan of Sokoto before the Caliphate was taken over by the British. Muhammadu Dikko – Emir of Katsina (1906–44). Sir Usman Nagogo – Emir of Katsina (1944–1981). Muhammadu Kabir Usman – Emir of Katsina (1981–2008). Abdullahi Bayero – Emir of Kano (1926–1953). Muhammadu Sanusi I – Emir of Kano (1954–1963). Ado Bayero – Emir of Kano (1963–2014). Sanusi Lamido Sanusi – Emir of Kano, former governor Central Bank of Nigeria. Sir Siddiq Abubakar III – former Sultan of Sokoto. Ibrahim Dasuki – former Sultan of Sokoto. Muhammadu Maccido – former Sultan of Sokoto. Zubeiru bi Adama - Last independent Lamido of Adamawa before British colonisation. Mohammed Jega - Emir of Gwandu. Ja'afaru Dan Isiyaku - Emir of Zazzau. Hameem Nuhu Sanusi - Emir of Dutse. Abubakar Shehu-Abubakar - Emir of Gombe. Ahmed Suleiman – Emir of Misau. Umaru Nagwamatse - First Sarkin Sudan, Founder of Kontogora Emirate. Modibbo Adama – Islamic Scholar and founder of the Adamawa Emirate.
The ELISA template, commonly used for performing immunoassays and other enzyme-based biochemical assays, has been adapted for use with the DMF platform for the detection of analytes such as IgE and IgG. In one example, a series of bioassays were conducted to establish the quantification capabilities of DMF devices, including an ELISA-based immunoassay for the detection of IgE. Superparamagnetic nanoparticles were immobilized with anti-IgE antibodies and fluorescently labeled aptamers to quantify IgE using an ELISA template. Similarly, for the detection of IgG, IgG can be immobilized onto a DMF chip, conjugated with horseradish-peroxidase (HRP)-labeled IgG, and then quantified through measurement of the color change associated with product formation of the reaction between HRP and tetramethylbenzidine. To further expand the capabilities and applications of DMF immunoassays beyond colorimetric detection (i.e., ELISA, magnetic bead-based assays), electrochemical detection tools (e.g., microelectrodes) have been incorporated into DMF chips for the detection of analytes such as TSH and rubella virus. For example, Rackus et al. integrated microelectrodes onto a DMF chip surface and substituted a previously reported chemiluminescent IgG immunoassay with an electroactive species, enabling detection of rubella virus. They coated magnetic beads with rubella virus, anti-rubella IgG, and anti-human IgG coupled with alkaline phosphatase, which in turn catalyzed an electron transfer reaction that was detected by the on-chip microelectrodes.
==== VAT systems ==== In Europe, Value-Added Tax (VAT) rates vary among member states, with a standard rate that cannot be less than 15%. Countries like Hungary, Croatia, Denmark, and Sweden have higher standard VAT rates, while Luxembourg, Malta, Cyprus, Greece, Germany, and Romania have lower rates. In China, wholesalers were subject to a Value-Added Tax (VAT) of either 9% or 13% on imported goods, depending on the type of product. Additionally, consumption tax is levied on products such as tobacco, alcohol, and luxury goods. These taxes are part of China's broader strategy to promote domestic consumption and regulate imports. A recent set of summaries of China's VAT law changes describes a maintained multi-rate VAT structure, including 13% for many goods sales/imports and other rates for specific categories. On the other hand, Vietnam imposed a standard VAT rate of 10% on most goods and services, with exemptions for certain agricultural products and essential services. In recent years, Vietnam has used a temporary VAT reduction policy with an extension of an 8% rate for many goods and services (with notable exclusions) through the end of 2026.
== External links == International Emergency Economic Powers Act as amended (PDF/details) in the GPO Statute Compilations collection International Emergency Economic Powers Act as enacted (details) in the US Statutes at Large
Sources: en.wikipedia.org
=== Predators === This species is preyed upon by jumping spiders of the Salticidae family. Some of these spiders simply leap into the webs of their prey and attack them. Others employ a certain strategy known as mimicry in order to trick P. phalangioides and capture them. A jumping spider whose aggressive mimicry behavior towards P. phalangioides has been well studied is the species Portia fimbriata. During mimicry, the jumping spider produces certain specialized vibrations near the edge of the webs of P. phalangioides. These vibrations cause the webs of P. phalangioides to oscillate in such a way that they mimic the oscillations that would be produced when a form of prey gets stuck in the web. The jumping spider will then continue on with these vibrations for very long durations of time, up to three days in some instances. P. phalangioides often assume that this is an indication that they have caught some sort of prey and will move toward the host of the vibrations. At this point, the jumping spider is in an optimal position to leap onto and attack P. phalangioides, thus subduing them in many instances. In addition to employing mimicry, these jumping spiders are also particularly good at preventing P. phalangioides from inducing their whirling defense mechanism, which tends to be an effective way for P. phalangioides spiders to defend themselves from predators.
Fish is a highly perishable product: the "fishy" smell of dead fish is due to the breakdown of amino acids into biogenic amines and ammonia. Live food fish are often transported in tanks at high expense for an international market that prefers its seafood killed immediately before it is cooked. Delivery of live fish without water is also being explored. While some seafood restaurants keep live fish in aquaria for display purposes or cultural beliefs, the majority of live fish are kept for dining customers. The live food fish trade in Hong Kong, for example, is estimated to have driven imports of live food fish to more than 15,000 tonnes in 2000. Worldwide sales that year were estimated at US$400 million, according to the World Resources Institute. If the cool chain has not been adhered to correctly, food products generally decay and become harmful before the validity date printed on the package. As the potential harm for a consumer when eating rotten fish is much larger than for example with dairy products, the U.S. Food and Drug Administration (FDA) has introduced regulation in the USA requiring the use of a time temperature indicator on certain fresh chilled seafood products. Because fresh fish is highly perishable, it must be eaten promptly or discarded; it can be kept for only a short time. In many countries, fresh fish are filleted and displayed for sale on a bed of crushed ice or refrigerated. Fresh fish is most commonly found near bodies of water, but the advent of refrigerated train and truck transportation has made fresh fish more widely available inland.
SeV can replicate to high titers in human monocyte-derived DCs. With the multiplicity of infection of 2, approximately 1/3 of the DCs begin to express encoded SeV proteins 8 hours after infection. This proportion increases to 2/3, 24 hours and decreases to 1/3, 48 hours after infection. SeV demonstrates high cytopathic effect on DCs; the virus can kill a third of DC even with a very low multiplicity of infection such as 0.5. Most important observation is that SeV infection triggers DC maturation, which is manifested in DC cell surface markers composition. The virus increases the expression of class I and class II molecules of the major histocompatibility complex (MHC) (HLA-A, HLA-B, HLA-C and HLADR), CD83, as well as costimulatory molecules CD40 and CD86.
=== Acute === Acute inflammation is a short-term process, usually appearing within a few minutes or hours and beginning to cease upon the removal of the injurious stimulus. It involves a coordinated and systemic mobilization response of various immune, endocrine and neurological mediators of acute inflammation. In a normal healthy response, it becomes activated, clears the pathogen and begins a repair process and then ceases. Acute inflammation occurs immediately upon injury, lasting only a few days. Cytokines and chemokines promote the migration of neutrophils and macrophages to the site of inflammation. Pathogens, allergens, toxins, burns, and frostbite are some of the typical causes of acute inflammation. Toll-like receptors (TLRs) recognize microbial pathogens. Acute inflammation can be a defensive mechanism to protect tissues against injury. Inflammation lasting 2–6 weeks is designated subacute inflammation.
== Medical uses == d-ribose has been suggested for use in management of congestive heart failure (as well as other forms of heart disease) and for chronic fatigue syndrome (CFS), also called myalgic encephalomyelitis (ME) in an open-label non-blinded, non-randomized, and non-crossover subjective study. Supplemental d-ribose can bypass part of the pentose phosphate pathway, an energy-producing pathway, to produce d-ribose-5-phosphate. The enzyme glucose-6-phosphate-dehydrogenase (G-6-PDH) is often in short supply in cells, but more so in diseased tissue, such as in myocardial cells in patients with cardiac disease. The supply of d-ribose in the mitochondria is directly correlated with ATP production; decreased d-ribose supply reduces the amount of ATP being produced. Studies suggest that supplementing d-ribose following tissue ischemia (e.g. myocardial ischemia) increases myocardial ATP production, and therefore mitochondrial function. Essentially, administering supplemental d-ribose bypasses an enzymatic step in the pentose phosphate pathway by providing an alternate source of 5-phospho-d-ribose 1-pyrophosphate for ATP production. Supplemental d-ribose enhances recovery of ATP levels while also reducing cellular injury in humans and other animals. One study suggested that the use of supplemental d-ribose reduces the instance of angina in men with diagnosed coronary artery disease. d-Ribose has been used to treat many pathological conditions, such as chronic fatigue syndrome, fibromyalgia, and myocardial dysfunction.
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.
PT-141 was the development code used for bremelanotide during its preclinical and early clinical programme. The peptide is now generally referred to by its international nonproprietary name.