If you have been reading about melanocortin signalling and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-06-18. Where a claim depends on a specific study, the study is described rather than over-claimed.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. Its design combines the ACTH(4-7) core fragment with a C-terminal Pro-Gly-Pro extension, a modification intended to improve stability and prolong activity. The molecule is hydrophilic, carries no lipid chains or glycosylation, and has a theoretical mass just over 810 daltons in its free form. All seven residues are proteinogenic amino acids, so no non-natural building blocks appear in the backbone. A free N-terminal methionine and C-terminal proline define the unmodified parent peptide.
The compound was developed during the 1980s at the Institute of Molecular Genetics in Moscow as part of research on fragments of adrenocorticotropic hormone. Early work examined short ACTH-derived sequences that retained neurotrophic effects while lacking the endocrine activity of the full hormone. Semax entered clinical use in Russia during the 1990s, where it received registration for several neurological indications. Outside that region it remained primarily a laboratory research material rather than an approved therapeutic. English-language literature on it grew more slowly and frequently cited the original Russian studies.
Terminology around the compound varies by source. It appears in catalogues and papers as Semax, as the heptapeptide ACTH(4-7)-Pro-Gly-Pro, and under various alphanumeric laboratory codes used by individual suppliers. These names refer to the same sequence but may imply different salt forms, purity grades, or counter-ions. Peptide databases usually list the free base mass, while product descriptions sometimes report acetate or trifluoroacetate salts with a different formula weight. Because naming conventions for research peptides are not standardised across vendors, checking the declared sequence and measured mass is more reliable than relying on a trade name alone.
Pharmacological accounts link semax to melanocortin signalling and to modulation of neurotrophic factor expression, particularly brain-derived neurotrophic factor and nerve growth factor. Much of this evidence comes from rodent studies using intranasal delivery, a route chosen because it allows peptides to reach the central nervous system with limited systemic exposure. Whether the same mechanisms operate in humans at comparable magnitude remains an open question. The precise receptor or receptors responsible for the reported behavioural and neuroprotective effects have not been conclusively identified.
Clinical reports describe use in ischaemic stroke, transient ischaemic attack, optic nerve conditions, and cognitive complaints, but most of these studies are small and were conducted in a single region. Systematic reviews have generally described the evidence base as limited in size and variable in methodological quality. Randomised controlled data suitable for international regulatory assessment are scarce. As a result, major treatment guidelines outside Russia do not include the peptide, and interest in it remains largely research-driven rather than routine clinical.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | ACTH(4-7) analogue |
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Free N terminus, unmodified side chains |
| Molecular weight | 813.9 Da | Free base; salt forms differ |
| Appearance | White to off-white powder | Lyophilised solid |
| Solubility | Freely soluble in water | Hydrophilic; polar solvents preferred |
Regulatory status varies sharply by country. Semax is registered for medical use in Russia, where it appears in formularies as a nasal solution, and it also holds registration in a small number of neighbouring states. It has no approval from the United States Food and Drug Administration or the European Medicines Agency, and it is not a scheduled controlled substance in most jurisdictions. Elsewhere it circulates mainly as laboratory material, so purity documentation comes from suppliers rather than from a national pharmacopoeia.
Semax is a synthetic peptide created in the Soviet Union during the early 1980s by researchers working in Moscow. It was built from the short adrenocorticotropic hormone fragment known as ACTH(4-10), and the chain was then extended with three additional amino acids. The resulting molecule was named semax and entered clinical use in Russia in 1994. It is generally described as a nootropic and neuroprotective agent rather than as a hormone analogue.
The parent fragment ACTH(4-10) carries the sequence Met-Glu-His-Phe-Arg-Trp-Gly. Semax replaces the arginine and tryptophan positions with a proline-glycine-proline tail, giving Met-Glu-His-Phe-Pro-Gly-Pro. That change removes residues associated with adrenal stimulation, so the peptide does not drive cortisol release the way full ACTH does. This distinction shapes how the compound is grouped in the literature, where it sits with neuropeptides and peptide neuromodulators rather than with corticosteroids.
Laboratory work points toward modulation of neurotrophic signaling, particularly expression of brain-derived neurotrophic factor and nerve growth factor in hippocampal tissue. Studies also describe effects on monoamine turnover, inflammatory mediators, and oxidative markers. These observations come mainly from animal models and cultured cells, so the causal chain in humans is not firmly established. Whether the reported molecular changes translate into measurable clinical benefit is an open question. Reviews generally present the mechanism as plausible rather than demonstrated.
Clinical evidence consists largely of small trials with modest sample sizes, often without independent replication. Reported endpoints include cognitive scores, recovery after stroke, and visual function, but study designs vary widely and few trials meet contemporary reporting standards. Systematic reviewers have noted a high risk of bias in several of these reports. No large multicenter trial conducted outside Russia has been published. The compound is therefore best described as investigational in most jurisdictions, with its clinical role still unresolved.
该化合物于二十世纪八十年代在俄罗斯被开发，相关工作由俄罗斯科学院分子遗传学研究所的研究团队主导。开发目标并非复制 ACTH 的完整激素活性，而是寻找保留其神经作用方向、同时去除促肾上腺皮质激素释放效应的短肽片段。研究记录显示，这一方向促成了多个相关短肽的合成与筛选，而 Semax 是其中被研究最广泛的一个。当地文献常以 Семакс 这一名称指代它。
研究兴趣主要集中在神经营养因子相关的路径上，包括脑源性神经营养因子与神经生长因子的表达变化。部分实验报告称在特定条件下观察到这些因子的水平上升，但具体信号通路和剂量依赖关系仍未完全厘清。多数公开数据来自细胞模型和动物实验，人体对照研究数量有限。因此，该化合物的作用机制在文献中属于活跃讨论，而非已经确立的定论。
Semax 是一种人工合成的七肽，氨基酸序列为 Met-Glu-His-Phe-Pro-Gly-Pro，单字母缩写记作 MEHFPGP。它被归类为促肾上腺皮质激素片段 ACTH(4-10) 的结构类似物，但并不天然存在于生物体内。母体片段 ACTH(4-10) 的序列为 Met-Glu-His-Phe-Arg-Trp-Gly，Semax 替换了中间两个残基，并在羧基端延长了 Pro-Gly-Pro 三肽。这种延长被普遍认为能提升分子对肽酶的耐受性。
Sandra Pizzarello (24 April 1933 – 24 October 2021) was an Italian biochemist known for her co-discovery of amino acid enantiomeric excess in carbonaceous chondrite meteorites. Her research interests concerned the characterization of meteoritic organic compounds in elucidating the evolution of planetary homochirality. Pizzarello was a project collaborator and co-investigator for the NASA Astrobiology Institute (NAI), the president of the International Society for the Study of the Origin of Life (2014-2017), and an emerita professor at Arizona State University (ASU).
== Organic chemistry == Because there are so many analogues of fentanyl, the naming for them tends to follow classical or IUPAC nomenclature conventions. This section is written to help illustrate the basic ring structure of fentanyl and what popular analogues reference on the carbon skeleton, helping a chemist working with fentanyl analogues quickly and consistently navigate the nomenclature system.
G banding Also Giemsa banding or G-banding. A technique used in cytogenetics to produce a visible karyotype by staining the condensed chromosomes with Giemsa stain. The staining produces consistent and identifiable patterns of dark and light "bands" in regions of chromatin, which allows specific chromosomes to be easily distinguished.
==== Enantiomeric excesses observed in extraterrestrial amino acids ==== More recently, amino acids from several carbonaceous chondrites have been identified with significant L-enantiomeric excesses. L-excesses from 3–15% in several non-protein α-dialkyl amino acids have been found in the Murchison and Murray meteorites. Their extraterrestrial origin is indicated by their absence in biological systems and significant heavy isotope enrichments in 13C and deuterium compared to terrestrial values. Further characterisation of L-isovaline excesses up to 20.5% in a range of carbonaceous chondrite groups have supported a hypothesis that increasing hydrothermal alteration of the host meteorite correlates with increasing observed L-enantiomeric excess. Large L-excesses for α-H amino acids have also been reported, but these are more problematic due to the potential for terrestrial contamination. The ungrouped C2 chondrite Tagish Lake has L-aspartic acid excesses up to ~60%, with carbon isotope measurements indicating an extraterrestrial origin due to significant enrichments in 13C. In Tagish Lake, proteinogenic amino acids show both significant L-excesses, and racemic mixtures: glutamic acid, serine, and threonine were found to have ~50 – 99% L-excesses, while alanine was racemic. It has been proposed that extraterrestrial amino acid L-excesses observed in carbonaceous chondrites are a result of differences in the crystallisation behaviour of the enantiomers.
Sources: en.wikipedia.org
On 1 June 2020, the United States Pharmacopeia (USP) decided to cancel the proposal to include recombinant technology for endotoxin testing in chapter 85, Bacterial Endotoxins, and start the development of a separate chapter that expands on the use, validation, and comparability of endotoxin tests based on recombinantly derived reagents. A separate guidance-only chapter 1085.1 was proposed by the USP, though comments and feedback published on 11 December 2020 show that pharmaceutical companies and the FDA did not support this chapter and requested compendial status. In response, USP subsequently developed General Chapter <86>, Bacterial Endotoxins Test Using Recombinant Reagents, which provides compendial requirements for endotoxin testing using non-animal-derived reagents such as recombinant factor C (rFC). Chapter <86> became official in USP–NF in May 2025, establishing rFC as a pharmacopeially recognized alternative to the Limulus amebocyte lysate test.
== Further reading == Duckworth WC (August 1988). "Insulin degradation: mechanisms, products, and significance". Endocrine Reviews. 9 (3): 319–45. doi:10.1210/edrv-9-3-319. PMID 3061785. Affholter JA, Hsieh CL, Francke U, Roth RA (August 1990). "Insulin-degrading enzyme: stable expression of the human complementary DNA, characterization of its protein product, and chromosomal mapping of the human and mouse genes". Molecular Endocrinology. 4 (8): 1125–35. doi:10.1210/mend-4-8-1125. PMID 2293021. Duckworth WC, Hamel FG, Bennett R, Ryan MP, Roth RA (February 1990). "Human red blood cell insulin-degrading enzyme and rat skeletal muscle insulin protease share antigenic sites and generate identical products from insulin". The Journal of Biological Chemistry. 265 (5): 2984–7. doi:10.1016/S0021-9258(19)39898-9. PMID 1689296. Kuo WL, Gehm BD, Rosner MR (October 1990). "Cloning and expression of the cDNA for a Drosophila insulin-degrading enzyme". Molecular Endocrinology. 4 (10): 1580–91. doi:10.1210/mend-4-10-1580. PMID 2126597. Ding L, Becker AB, Suzuki A, Roth RA (February 1992). "Comparison of the enzymatic and biochemical properties of human insulin-degrading enzyme and Escherichia coli protease III". The Journal of Biological Chemistry. 267 (4): 2414–20. doi:10.1016/S0021-9258(18)45895-4. PMID 1733942. Mukherjee A, Song E, Kihiko-Ehmann M, Goodman JP, Pyrek JS, Estus S, et al. (December 2000). "Insulysin hydrolyzes amyloid beta peptides to products that are neither neurotoxic nor deposit on amyloid plaques". The Journal of Neuroscience. 20 (23): 8745–8749.
Glypromate (Gly-Pro-Glu, GPE) is a tripeptide fragment derived from the N-terminus of the endogenous growth factor IGF-1. It has antiinflammatory and neuroprotective effects and is of interest in the treatment of neurological conditions such as Alzheimer's disease and Parkinson's disease. The simple GPE peptide has poor blood-brain barrier penetration and is rapidly metabolised in the body, however a number of synthetic derivatives of GPE have been developed with improved properties.
Popular protests broke out in early 2011, led by both secular and Islamist opposition groups. Longtime rebel groups like the Houthis and the Southern Movement also participated in the protests. Saleh responded with a violent crackdown, and the country nearly disintegrated into an all-out civil war as several army elements broke with the government and joined the protesters, beginning in March. Saleh was almost killed when a bomb went off in a mosque where he and other top government officials were praying on 3 June, apparently in an assassination attempt. While his condition initially appeared grave, Saleh recovered and returned to work on 23 September after several months of medical treatment in Saudi Arabia. He left Vice President Hadi in charge during his absence. As acting president, Hadi met with the opposition and reportedly expressed openness to political reforms. However, he rejected the idea of forcing Saleh from power without the president's consent.
is the standard entropy change. Since the enthalpy should be approximately the same for the two reactions, the difference between the two stability constants is due to the effects of entropy. In equation (1) there are two particles on the left and one on the right, whereas in equation (2) there are three particles on the left and one on the right. This difference means that less entropy of disorder is lost when the chelate complex is formed with bidentate ligand than when the complex with monodentate ligands is formed. This is one of the factors contributing to the entropy difference. Other factors include solvation changes and ring formation. Some experimental data to illustrate the effect are shown in the following table.
Sources: en.wikipedia.org
Mimosa tenuiflora is an entheogen used by the Jurema Cult (O Culto da Jurema) in northeastern Brazil. Dried Mexican Mimosa tenuiflora root bark has been shown to have a dimethyltryptamine (DMT) content of about 1-1.7%. The stem bark has about 0.03% DMT. The parts of the tree are traditionally used in northeastern Brazil in a psychoactive decoction also called Jurema or Yurema. Analogously, the traditional Western Amazonian sacrament Ayahuasca is brewed from indigenous ayahuasca vines. However, to date no β-carbolines such as harmala alkaloids have been detected in Mimosa tenuiflora decoctions, yet the Jurema is used in combination with several plants. This presents challenges to the pharmacological understanding of how DMT from the plant is rendered orally active as an entheogen, because the psychoactivity of ingested DMT requires the presence of a monoamine oxidase inhibitor (MAOI), such as a β-carboline. If an MAOI is neither present in the plant nor added to the mixture, the enzyme monoamine oxidase (MAO) will metabolize DMT in the human gut, preventing the active molecule from entering the blood and brain. The plant is also used in clandestine manufacture of crystalline dimethyltryptamine (DMT). In this form, it is psychoactive by itself when vaporized and inhaled. The isolation of the chemical compound yuremamine from Mimosa tenuiflora as reported in 2005 represents a new class of phytoindoles, which may explain an apparent oral activity of DMT in Jurema.
The NBOMe drugs, primarily 25I-NBOMe, were encountered as novel recreational drugs by 2010, and by 2012 had eclipsed other psychedelics like LSD and psilocybin-containing mushrooms in popularity, at least for a time. Various NBOMes, such as 25I-NBOMe, became Schedule I controlled substances in the United States in 2013.
Invasive garlic mustard, Alliaria petiolata, and its allelochemical benzyl isothiocyanate were shown to inhibit the growth of three species of EcM fungi grown on white pine seedlings. Changes in EcM communities can have drastic effects on nutrient uptake and community composition of native trees, with far-reaching ecological ramifications.
==== February 2024 ==== Between 3 and 5 February, five Amal movement fighters were reported killed: two in airstrikes in Blida and three in Bayt Lif. On 8 February, the IDF conducted a drone strike on a car in Nabatieh. Israeli media said a regional Hezbollah commander named Abbas al-Dabs was assassinated in the attack. A day before, two Hezbollah members, including al-Dabs, were named by Israeli intelligence as reportedly working alongside IRGC officers on building Iranian air defenses in Syria. On 10 February, an Israeli drone struck a car near Sidon, killing at least two people and wounding two others. An Israeli security source said the target of the strike was Hamas official Basel Saleh, who was "injured to an unknown extent". Saleh was responsible for enlisting new Hamas recruits in Gaza and the West Bank. On 12 February, another assassination attempt took place targeting Hezbollah official Mohammed Abd al-Rasoul Alawiya in his car in Bint Jbeil. On 14 February, in the deadliest day of fighting, a barrage of eleven rockets fired from Lebanon struck Safed and an army base in northern Israel, killing an Israeli soldier and injuring eight others. Israel responded with widespread airstrikes against targets belonging to Hezbollah infrastructure in Jabal al-Braij, Kfar Houneh, Kafr Dunin, Aadchit and Souaneh, killing a total of ten people. In Nabatieh, an attack on a residential building killed seven members of a family, including a child. Another attack in the town of al-Suwana killed a woman and her two children.
The most widely used method to determine absolute molar mass is size-exclusion chromatography (SEC) coupled with multi-angle laser light scattering (MALS). SEC can separate macromolecules based on their size by passing an analyte containing molecules of different sizes through a column containing porous substrate. Larger components of the analyte spend less time traveling through these pores and therefore elute faster, while smaller components can access more of these pores and are therefore retained longer. However, molar masses determined through SEC require calibration curves constructed from standards, and calculating absolute molar masses require absolute detection systems. The two primary detection systems used to determine absolute molar mass are light scattering photometers and viscometers. Static light scattering (SLS) experiments measure the difference between the light scattered by a dilute solution and the light scattered through pure solvent. Given a dilute enough solution and at an angle of θ = 0° between the incident light and the scattering direction, this difference, known as the excess Rayleigh ratio ΔR(θ), can be approximately related to the weight-average molar mass Mw through the equation:
Sources: en.wikipedia.org
It is a synthetic seven-amino-acid peptide built from the ACTH(4-7) sequence plus a Pro-Gly-Pro tail. It belongs to the family of short ACTH fragments studied for nervous-system effects. Its backbone contains only standard amino acids.
It contains the 4-7 fragment of adrenocorticotropic hormone extended at the C terminus. That truncation removes the region associated with steroidogenic activity. The design intent was to keep neurotrophic properties while avoiding full hormonal effects.
No natural source of the intact heptapeptide is known. It is produced by solid-phase peptide synthesis. Some related ACTH fragments arise as hormone processing products, but the Pro-Gly-Pro extension is a designed addition rather than a natural sequence.
It is described as a synthetic analogue of the ACTH(4–10) fragment, a short segment of adrenocorticotropic hormone. Its sequence differs from that fragment and includes two proline residues, which influence stability and behaviour in solution.