A practical reference on peptide synthesis: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-11-17 and is reviewed periodically as new material appears.
The compound is registered in Russia as a pharmaceutical product, most commonly formulated as a nasal solution, and has been used in that setting since the 1990s. Outside that jurisdiction it is generally handled as a research chemical rather than an approved medicine. Regulatory status therefore differs sharply between countries, and material sold internationally may not correspond to the Russian pharmaceutical formulation. Documentation with commercial samples is typically limited to a certificate of analysis covering purity and identity, not clinical status or local legal classification.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It corresponds to the ACTH(4-7) fragment extended at the C-terminus by a Pro-Gly-Pro tripeptide, an addition intended to slow enzymatic breakdown. The molecular formula is C37H51N9O10S and the molecular mass is approximately 814 daltons. In the literature it is often described as an ACTH(4-10) analog, although that label reflects a naming convention as much as a precise structural relationship. The compound was developed in Russia and remains most closely associated with that research tradition.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C37H51N9O10S | Contains one methionine sulfur atom |
| Molecular mass | Approximately 814 Da | Consistent with a seven-residue peptide |
| Appearance | White to off-white powder | Typical lyophilized form |
| Solubility | Freely soluble in water | Also soluble in dimethyl sulfoxide |
| Typical storage | -20 °C, desiccated | Limits methionine oxidation |
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.
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.
Published research on this peptide originates mainly from Russian laboratories, and the wider international literature is comparatively thin. Studies have used rodent models of stroke, hypoxia, and memory tasks, with a smaller number of human trials reported. Reported outcomes include changes in attention and memory measures, along with effects on neurotrophic factor expression in some experiments. Small sample sizes, inconsistent dosing protocols, and limited independent replication are widely noted limitations, so the strength of the clinical evidence remains an open question.
Semax is a synthetic heptapeptide whose sequence is Met-Glu-His-Phe-Pro-Gly-Pro. The first four residues correspond to the ACTH(4-10) fragment, while the terminal Pro-Gly-Pro extension was added to improve metabolic stability. Its molecular formula is C37H51N9O10S and its monoisotopic mass is approximately 813.9 Da. The compound is classified as a peptide research chemical and as a registered pharmaceutical product in Russia, but it does not hold marketing approval in the European Union or the United States. Naming conventions vary across supplier catalogs.
Homoserine dehydrogenase catalyzes the reaction of aspartate-semialdehyde (ASA) to homoserine. The overall reaction reduces the C4 carboxylic acid functional group of ASA to a primary alcohol and oxidizes the C1 aldehyde to a carboxylic acid. Residues Glu 208 and Lys 117 are thought to be involved in the active catalytic site of the enzyme. Asp 214 and Lys 223 have been shown to be important for hydride transfer in the catalyzed reaction. Once the C4 carboxylic acid is reduced to an aldehyde and the C1 aldehyde is oxidized to a carboxylic acid, experiments suggest that Asp 219, Glu 208 and a water molecule bind ASA in the active site while Lys 223 donates a proton to the aspartate-semialdehyde C4 oxygen. Homoserine dehydrogenase has an NAD(P)H cofactor, which then donates a hydrogen to the same carbon, effectively reducing the aldehyde to an alcohol. (Refer to figures 1 and 2). However, the precise mechanism of complete homoserine dehydrogenase catalysis remains unknown. The homoserine dehydrogenase-catalyzed reaction has been postulated to proceed through a bi-bi kinetic mechanism, where the NAD(P)H cofactor binds the enzyme first and is the last to dissociate from the enzyme once the reaction is complete. Additionally, while both NADH and NADPH are adequate cofactors for the reaction, NADH is preferred. The Km of the reaction is four-times smaller with NADH and the Kcat/Km is three-times greater, indicating a more efficient reaction. Homoserine dehydrogenase also exhibits multi-order kinetics at subsaturating levels of substrate.
=== Aortic insufficiency === Aortic insufficiency (AI) occurs in half to two-thirds of ascending AD, and the diastolic heart murmur of aortic insufficiency is audible in about 32% of proximal dissections. The intensity (loudness) of the murmur depends on the blood pressure and may be inaudible in the event of low blood pressure. Multiple causes exist for AI in the setting of ascending AD. The dissection may dilate the annulus of the aortic valve, preventing the leaflets of the valve from coapting. The dissection may extend into the aortic root and detach the aortic valve leaflets. Alternatively, following an extensive intimal tear, the intimal flap may prolapse into the left ventricular outflow tract, causing intimal intussusception into the aortic valve, thereby preventing proper valve closure.
Gene doping agents are a relatively recently described class of athletic performance-enhancing substances. These drug therapies, which involve viral vector-mediated gene transfer, are not known to currently be in use as of 2020.
This helium-nitrogen mixture was injected and stored in the Cliffside gas field until needed, at which time it was further purified. By 1995, a billion cubic meters of the gas had been collected and the reserve was US$1.4 billion in debt, prompting the Congress of the United States in 1996 to discontinue the reserve. The resulting Helium Privatization Act of 1996 (Public Law 104–273) directed the United States Department of the Interior to empty the reserve, with sales starting by 2005. Helium produced between 1930 and 1945 was about 98.3% pure (2% nitrogen), which was adequate for airships. In 1945, a small amount of 99.9% helium was produced for welding use. By 1949, commercial quantities of Grade A 99.95% helium were available. For many years, the United States produced more than 90% of commercially usable helium in the world, while extraction plants in Canada, Poland, Russia, and other nations produced the remainder. In the mid-1990s, a new plant in Arzew, Algeria, producing 17 million cubic metres (600 million cubic feet) began operation, with enough production to cover all of Europe's demand. Meanwhile, by 2000, the consumption of helium within the U.S. had risen to more than 15 million kg per year. In 2004–2006, additional plants in Ras Laffan, Qatar, and Skikda, Algeria were built. Algeria quickly became the second leading producer of helium. Through this time, both helium consumption and the costs of producing helium increased. From 2002 to 2007 helium prices doubled.
Sources: en.wikipedia.org
According to Grünwedel, "the circles (mandalâni) undoubtedly refer to the edges made of foliage and human skulls", that is the Classical border of acanthus leaves and Buddhist skulls painted along the inferior border of the mural. The word Rumakama, or Romakam appears in the Kizil paintings as well as in the later Tibetan document, and is thought to refer to a painter who came from the Roman Empire or the Byzantine Empire.
=== Separation methods === Since astatine is the main product of the synthesis, after its formation it must only be separated from the target and any significant contaminants. Several methods are available, "but they generally follow one of two approaches—dry distillation or [wet] acid treatment of the target followed by solvent extraction." The methods summarized below are modern adaptations of older procedures, as reviewed by Kugler and Keller. Pre-1985 techniques more often addressed the elimination of co-produced toxic polonium; this requirement is now mitigated by capping the energy of the cyclotron irradiation beam.
== Four engineering approaches == Synthetic biology has traditionally been divided into four different engineering approaches: top down, parallel, orthogonal and bottom up. To replicate emergent behaviours from natural biology and build artificial life, unnatural chemicals are used. The other looks for interchangeable components from biological systems to put together and create systems that do not work naturally. In either case, a synthetic objective compels researchers to venture into new area in order to engage and resolve issues that cannot be readily resolved by analysis. Due to this, new paradigms are driven to arise in ways that analysis cannot easily do. In addition to devices that oscillate, creep, and play tic-tac-toe, synthetic biology has produced diagnostic instruments that enhance the treatment of patients with infectious diseases.
The 'father of modern chemistry', Antoine Lavoisier, had viewed fermentation as a simple chemical reaction and rejected the notion that living organisms could be involved. By the 19th century, this was seen as vitalism, which was lampooned in an anonymous 1839 publication by Justus von Liebig and Friedrich Wöhler. In 1837, Charles Cagniard de la Tour, Theodor Schwann and Friedrich Traugott Kützing independently published papers concluding, as a result of microscopic investigations, that yeast is a living organism that reproduces by budding. Schwann boiled grape juice to kill the yeast and found that no fermentation would occur until new yeast was added. The turning point came when Louis Pasteur (1822–1895), during the 1850s and 1860s, repeated Schwann's experiments and showed fermentation is initiated by living organisms in a series of investigations. In 1857, Pasteur showed lactic acid fermentation is caused by living organisms. In 1860, he demonstrated how bacteria cause souring in milk, a process formerly thought to be merely a chemical change. His work in identifying the role of microorganisms in food spoilage led to the process of pasteurization. In 1877, working to improve the French brewing industry, Pasteur published his famous paper on fermentation, "Etudes sur la Bière", which was translated into English in 1879 as "Studies on fermentation". He defined fermentation (incorrectly) as "Life without air".
Equilibrium chemistry is concerned with systems in chemical equilibrium. The unifying principle is that the free energy of a system at equilibrium is the minimum possible, so that the slope of the free energy with respect to the reaction coordinate is zero. This principle, applied to mixtures at equilibrium provides a definition of an equilibrium constant. Applications include acid–base, host–guest, metal–complex, solubility, partition, chromatography and redox equilibria.
Sources: en.wikipedia.org
Other sources have defined deficiency as less than 25 nmol/L, insufficiency as 30–50 nmol/L and a level for "optimal" intake remains controversial and under research, as of 2026. Part of the controversy is because studies have reported differences in serum levels of 25(OH)D between ethnic groups, with studies pointing to genetic as well as environmental reasons behind these variations. African-American populations have lower serum 25(OH)D than their age-matched white population, but at all ages have superior calcium absorption efficiency, a higher bone mineral density, and as elderly, a lower risk of osteoporosis and fractures. Using the 25(OH)D assay as a screening tool of the generally healthy population to identify and treat individuals is considered not as cost-effective as a government-mandated fortification program. Instead, there is a recommendation that testing should be limited to those showing symptoms of vitamin D deficiency or who have health conditions known to cause vitamin deficiency.
=== Urinary tract infections === A UTI affects parts of the urinary system including the urethra, bladder, and kidneys. There is about a 1% risk of UTIs in boys under two years old, and most incidents occur in the first year of life. There is good but not ideal evidence that circumcision reduces the incidence of UTIs in boys under two, and there is fair evidence that the reduction in incidence is by a factor of 3 to 10 (100 circumcisions prevent one UTI). Circumcision is most likely to benefit boys who have a high risk of UTIs due to anatomical defects and may be used to treat recurrent UTIs. There is a plausible biological explanation for the reduction in UTI risk after circumcision. The orifice through which urine passes at the tip of the penis (the urinary meatus) hosts more urinary system disease-causing bacteria in uncircumcised boys than in circumcised boys, especially in those under six months of age. As these bacteria are a risk factor for UTIs, circumcision may reduce the risk of UTIs through a decrease in the bacterial population.
=== Florists' attitudes === Many traditional retail florists have a deep-rooted disdain for modern wire services. This comes from the perception that companies such as FTD, 1800flowers, From You Flowers and Teleflora take floral orders away from the local business and extract excessive commission. FTD was formerly a co-op, owned by its member florists. In 1994 the board of directors made the decision to sell the co-op to Perry Capital. The revenue from the sale was disbursed amongst the member florists, more senior florists being paid substantially more than the more junior florists. At this point FTD became a for-profit company.
=== Pet food === Semi-moist pet food such as chewy dog treats and soft cat treats are shelf-stable, soft and do not have a high moisture content. Ingredients added to intermediate moisture pet food to achieve lower water activity are soy flakes and wheat flour in addition to solutes such as glycerol, salt, and sugar. Processing techniques such as extrusion are employed to attain the final intermediate moisture pet food. Intermediate moisture pet food are convenient products because they leave less odor and are less messy than canned wet pet food. Additionally, they have been found to be more palatable to pets than dry pet food products.
== Structure == Theoretical calculations have predicted the existence of metastable O4 molecules with two different shapes: a "puckered" square like cyclobutane or S4, and a "pinwheel" with three oxygen atoms surrounding a central one in a trigonal planar formation similar to boron trifluoride or sulfur trioxide. It was previously pointed out that the "pinwheel" O4 molecule should be the natural continuation of the isoelectronic series BO3−3, CO2−3, NO−3, and analogous to SO3; that observation served as the basis for the mentioned theoretical calculations.
Sources: en.wikipedia.org
It is registered as a pharmaceutical product in Russia, where it is typically supplied as a nasal solution. In most other countries it is not an approved drug and is traded as a research chemical instead. Approval status depends entirely on the jurisdiction involved.
Most published work uses intranasal administration, matching the route of the registered Russian formulation. Some animal experiments use intravenous or intraperitoneal injection. The route matters because the intact peptide is cleared rapidly from blood, so exposure differs between methods.
A purity value describes the share of the powder accounted for by the target peptide, usually by high-performance liquid chromatography. It does not confirm that the sequence is correct, which requires mass spectrometry or amino acid analysis. Purity and identity are separate checks.
Semax is a synthetic seven-amino-acid peptide derived from a fragment of corticotropin. It is used in Russia as a nasal preparation, while elsewhere it is studied as a research compound. It is not approved as a medicine in most countries.