Everything below concerns heptapeptide. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-08-12. Where a claim depends on a specific study, the study is described rather than over-claimed.
Scientific literature on semax is unevenly distributed. A substantial share of published work originates from a small number of laboratories in Russia, while independent replication elsewhere is limited. Human data consist mostly of small trials with short follow-up, and several reported outcomes rely on subjective rating scales. Questions about how much intact peptide reaches the central nervous system after nasal administration, and how long it persists there, are still unresolved. The compound is best described as an active research subject rather than a settled pharmacological agent.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It was derived from the ACTH(4-10) fragment, a short segment of adrenocorticotropic hormone that lacks the hormonal activity associated with the full-length peptide. Researchers at the Institute of Molecular Genetics in Moscow developed the compound during the 1980s. It has been registered as a pharmaceutical product in Russia and several neighbouring countries, where it is supplied as a nasal solution, and it is also sold internationally as a research chemical.
The proposed mechanism centres on neurotrophic signalling rather than direct receptor activation. Semax is reported to increase expression of brain-derived neurotrophic factor and nerve growth factor in several brain regions, and to shift the balance between excitatory and inhibitory neurotransmitter systems. Interaction with melanocortin receptors has been suggested because of the parent ACTH fragment. Many of these findings come from rodent studies, and the extent to which they translate to human physiology remains an open question.
Verification of a supplied batch generally combines a certificate of analysis with independent testing, because certificates are self-reported documents. A typical package includes a chromatographic trace, a mass spectrum, and a stated water or counter-ion content. Batch-to-batch consistency matters more than a single purity figure when results are compared across experiments. No single mandatory standard governs research-grade peptide release, so laboratories are expected to define their own acceptance criteria. Residual trifluoroacetate from purification is a frequently overlooked counter-ion.
Lyophilized material is chemically stable for extended periods when kept dry, cold, and protected from light. The powder is hygroscopic, so vials should be warmed to room temperature before opening to reduce condensation on the contents. Once dissolved, the peptide is far less stable because peptide bonds are susceptible to hydrolysis and the methionine residue can oxidize. Solutions are typically aliquoted and held at 2-8 °C for short intervals or frozen for longer ones, and repeated freeze-thaw cycles should be avoided.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C37H51N9O10S | Calculated for the free peptide |
| Molar mass | 813.9 g/mol | Anhydrous free base |
| Peptide class | Synthetic heptapeptide | ACTH(4-10) analogue |
| Parent fragment | ACTH(4-10) | Adrenocorticotropic hormone segment |
| Developmental origin | Institute of Molecular Genetics, Moscow | Work began in the 1980s |
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.
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.
Pharmacokinetic accounts emphasize rapid breakdown. After intravenous dosing the intact peptide disappears from blood within minutes, and nasal delivery produces low but measurable concentrations. Metabolites rather than the parent molecule may account for part of the observed activity, although the relative contribution is unresolved. Dosing in the literature varies widely and no optimal schedule has been agreed. These gaps are regularly cited as a reason the findings have not produced broad clinical adoption beyond the original research setting.
Proposed mechanisms center on neurotrophic signaling rather than on classical melanocortin receptor activation. Rodent experiments have reported shifts in the expression of brain-derived neurotrophic factor and nerve growth factor after administration, together with changes in the associated receptor systems. Several authors argue that the peptide acts largely through its degradation products and their interaction with peptidergic pathways, but this remains a hypothesis rather than a settled finding. No single molecular target has been identified in a way that the field broadly accepts.
=== Historical development === Milk is presently the most mature system to produce recombinant proteins from transgenic organisms. Blood, egg white, seminal plasma, and urine are other theoretically possible systems, but all have drawbacks. Blood, for instance, as of 2012 cannot store high levels of stable recombinant proteins, and biologically active proteins in blood may alter the health of the animals. Expression in the milk of a mammal, such as a cow, sheep, or goat, is a common application, as milk production is plentiful and purification from milk is relatively easy. Hamsters and rabbits have also been used in preliminary studies because of their faster breeding. One approach to this technology is the creation of a transgenic mammal that can produce the biopharmaceutical in its milk (or blood or urine). Once an animal is produced, typically using the pronuclear microinjection method, it becomes efficacious to use cloning technology to create additional offspring that carry the favorable modified genome. In February 2009 the US FDA granted marketing approval for the first drug to be produced in genetically modified livestock. The drug is called ATryn, which is antithrombin protein purified from the milk of genetically modified goats. Marketing permission was granted by the European Medicines Agency in August 2006.
== Genetics == Six genes have been found to be associated with the condition. These genes include BANP-ZNF469, COL4A4, FOXO1, FNDC3B, IMMP2L and RXRA-COL5A1. Others likely also exist. Patients with a parent, sibling, or child who has keratoconus have 15 to 67 times higher risk in developing corneal ectasia compared to patients with no affected relatives.
===== MeSH D08.811.277.352 – esterases (EC 3.1) ===== MeSH D08.811.277.352.100 – carboxylic-ester hydrolases MeSH D08.811.277.352.100.050 – acetylesterase MeSH D08.811.277.352.100.100 – carboxylesterase MeSH D08.811.277.352.100.150 – cholesterol esterase MeSH D08.811.277.352.100.170 – cholinesterases MeSH D08.811.277.352.100.170.176 – acetylcholinesterase MeSH D08.811.277.352.100.170.250 – butyrylcholinesterase MeSH D08.811.277.352.100.170.710 – pseudocholinesterase MeSH D08.811.277.352.100.220 – dehydroascorbatase MeSH D08.811.277.352.100.400 – lipase MeSH D08.811.277.352.100.400.745 – pancrelipase MeSH D08.811.277.352.100.430 – lipoprotein lipase MeSH D08.811.277.352.100.500 – monoacylglycerol lipases MeSH D08.811.277.352.100.550 – naphthol as d esterase MeSH D08.811.277.352.100.680 – phospholipases MeSH D08.811.277.352.100.680.510 – lysophospholipase MeSH D08.811.277.352.100.680.750 – phospholipases a MeSH D08.811.277.352.100.680.750.500 – 1-alkyl-2-acetylglycerophosphocholine esterase MeSH D08.811.277.352.335 – deoxyribonucleases MeSH D08.811.277.352.335.350 – endodeoxyribonucleases MeSH D08.811.277.352.335.350.025 – aspergillus nuclease s1 MeSH D08.811.277.352.335.350.137 – deoxyribonuclease (pyrimidine dimer) MeSH D08.811.277.352.335.350.250 – deoxyribonuclease i MeSH D08.811.277.352.335.350.250.900 – streptodornase and streptokinase MeSH D08.811.277.352.335.350.275 – deoxyribonuclease iv (phage t4-induced) MeSH D08.811.277.352.335.350.300 – dna restriction enzymes MeSH D08.811.277.352.335.350.300.250 – deoxyribonucleases, type i site-specific MeSH D08.811.277.352.335.350.300.260 – deoxyribonucleases, type ii site-specific MeSH D08.811.277.352.335.350.300.260.240 – deoxyribonuclease bamhi MeSH D08.811.277.352.335.350.300.260.250 – deoxyribonuclease ecori MeSH D08.811.277.352.335.350.300.260.260 – deoxyribonuclease hindiii MeSH D08.811.277.352.335.350.300.260.300 – deoxyribonuclease hpaii MeSH D08.811.277.352.335.350.300.270 – deoxyribonucleases, type iii site-specific MeSH D08.811.277.352.335.350.400 – holliday junction resolvases MeSH D08.811.277.352.335.350.500 – micrococcal nuclease MeSH D08.811.277.352.335.375 – exodeoxyribonucleases MeSH D08.811.277.352.335.375.750 – exodeoxyribonuclease V MeSH D08.811.277.352.355 – endonucleases MeSH D08.811.277.352.355.325 – endodeoxyribonucleases MeSH D08.811.277.352.355.325.025 – aspergillus nuclease s1 MeSH D08.811.277.352.355.325.300 – dna restriction enzymes MeSH D08.811.277.352.355.325.300.250 – deoxyribonucleases, type i site-specific MeSH D08.811.277.352.355.325.300.260 – deoxyribonucleases, type ii site-specific MeSH D08.811.277.352.355.325.300.260.240 – deoxyribonuclease bamhi MeSH D08.811.277.352.355.325.300.260.250 – deoxyribonuclease ecori MeSH D08.811.277.352.355.325.300.260.260 – deoxyribonuclease hindiii MeSH D08.811.277.352.355.325.300.260.300 – deoxyribonuclease hpaii MeSH D08.811.277.352.355.325.300.270 – deoxyribonucleases, type iii site-specific MeSH D08.811.277.352.355.325.350 – flap endonucleases MeSH D08.811.277.352.355.325.400 – holliday junction resolvases MeSH D08.811.277.352.355.325.500 – micrococcal nuclease MeSH D08.811.277.352.355.350 – endoribonucleases MeSH D08.811.277.352.355.350.025 – aspergillus nuclease s1 MeSH D08.811.277.352.355.350.500 – micrococcal nuclease MeSH D08.811.277.352.355.350.700 – ribonuclease h, calf thymus MeSH D08.811.277.352.355.350.715 – ribonuclease, pancreatic MeSH D08.811.277.352.355.350.725 – ribonuclease t1 MeSH D08.811.277.352.355.350.810 – RNA-induced silencing complex MeSH D08.811.277.352.365 – exonucleases MeSH D08.811.277.352.365.290 – exodeoxyribonucleases MeSH D08.811.277.352.365.300 – exoribonucleases MeSH D08.811.277.352.640 – phosphoric diester hydrolases MeSH D08.811.277.352.640.050 – annexin A3 MeSH D08.811.277.352.640.125 – 3',5'-cyclic-GMP phosphodiesterase MeSH D08.811.277.352.640.150 – 3',5'-cyclic-nucleotide phosphodiesterase MeSH D08.811.277.352.640.160 – 2',3'-cyclic-nucleotide phosphodiesterases MeSH D08.811.277.352.640.295 – glycerophosphoinositol inositolphosphodiesterase MeSH D08.811.277.352.640.430 – phosphodiesterase i MeSH D08.811.277.352.640.700 – phospholipases MeSH D08.811.277.352.640.700.700 – phospholipase c MeSH D08.811.277.352.640.700.700.500 – phosphatidylinositol diacylglycerol-lyase MeSH D08.811.277.352.640.700.700.750 – phospholipase c gamma MeSH D08.811.277.352.640.700.710 – phospholipase d MeSH D08.811.277.352.640.750 – sphingomyelin phosphodiesterase MeSH D08.811.277.352.650 – phosphoric monoester hydrolases MeSH D08.811.277.352.650.025 – acid phosphatase MeSH D08.811.277.352.650.035 – alkaline phosphatase MeSH D08.811.277.352.650.200 – fructose-bisphosphatase MeSH D08.811.277.352.650.225 – glucose-6-phosphatase MeSH D08.811.277.352.650.300 – histidinol-phosphatase MeSH D08.811.277.352.650.575 – 4-nitrophenylphosphatase MeSH D08.811.277.352.650.600 – nucleotidases MeSH D08.811.277.352.650.600.600 – 5'-nucleotidase MeSH D08.811.277.352.650.620 – phosphatidate phosphatase MeSH D08.811.277.352.650.622 – phosphofructokinase-2 MeSH D08.811.277.352.650.625 – phosphoprotein phosphatase MeSH D08.811.277.352.650.625.150 – calcineurin MeSH D08.811.277.352.650.625.300 – glycogen-synthase-d phosphatase MeSH D08.811.277.352.650.625.475 – myosin light-chain phosphatase MeSH D08.811.277.352.650.625.650 – phosphorylase phosphatase MeSH D08.811.277.352.650.625.700 – protein-tyrosine-phosphatase MeSH D08.811.277.352.650.625.700.150 – antigens, cd45 MeSH D08.811.277.352.650.625.700.200 – cdc25 phosphatase MeSH D08.811.277.352.650.625.725 – pyruvate dehydrogenase (lipoamide)-phosphatase MeSH D08.811.277.352.650.700 – 6-phytase MeSH D08.811.277.352.650.850 – pten phosphohydrolase MeSH D08.811.277.352.660 – phosphoric triester hydrolases MeSH D08.811.277.352.660.500 – aryldialkylphosphatase MeSH D08.811.277.352.700 – ribonucleases MeSH D08.811.277.352.700.350 – endoribonucleases MeSH D08.811.277.352.700.350.025 – aspergillus nuclease s1 MeSH D08.811.277.352.700.350.262 – eosinophil cationic protein MeSH D08.811.277.352.700.350.381 – eosinophil-derived neurotoxin MeSH D08.811.277.352.700.350.500 – micrococcal nuclease MeSH D08.811.277.352.700.350.700 – ribonuclease h, calf thymus MeSH D08.811.277.352.700.350.707 – ribonuclease iii MeSH D08.811.277.352.700.350.711 – ribonuclease p MeSH D08.811.277.352.700.350.715 – ribonuclease, pancreatic MeSH D08.811.277.352.700.350.725 – ribonuclease t1 MeSH D08.811.277.352.700.350.810 – RNA-induced silencing complex MeSH D08.811.277.352.700.375 – exoribonucleases MeSH D08.811.277.352.827 – sulfatases MeSH D08.811.277.352.827.070 – arylsulfatases MeSH D08.811.277.352.827.070.060 – n-acetylgalactosamine-4-sulfatase MeSH D08.811.277.352.827.070.250 – cerebroside-sulfatase MeSH D08.811.277.352.827.070.625 – steryl-sulfatase MeSH D08.811.277.352.827.180 – chondroitinases and chondroitin lyases MeSH D08.811.277.352.827.180.175 – chondroitinsulfatases MeSH D08.811.277.352.827.180.175.060 – n-acetylgalactosamine-4-sulfatase MeSH D08.811.277.352.827.180.175.275 – chondro-4-sulfatase MeSH D08.811.277.352.827.500 – iduronate sulfatase MeSH D08.811.277.352.897 – thiolester hydrolases MeSH D08.811.277.352.897.075 – acetyl-CoA hydrolase MeSH D08.811.277.352.897.700 – palmitoyl-coa hydrolase MeSH D08.811.277.352.897.850 – ubiquitin thiolesterase
=== Cap snatching in Hantaviridae === Cap snatching has also been investigated in depth for the family Hantaviridae (Bunyavirales). There is evidence that the N protein binds to the 5' cap and protects them from degradation by cellular machinery. The N protein accumulates in cytoplasmic cellular processing bodies (P bodies), sequestering the protected 5' caps as a pool of available primers for the RdRp to begin viral mRNA synthesis. There are four nucleotides on the vRNA that are adjacent the 5' cap for binding. The virus preferentially cleaves mRNA cap at a G residue 14 nucleotides downstream from the cap. Additionally, it usually cleaves caps from nonsense mRNA instead of actively translated mRNA. The N protein can guard host mRNA caps without P-bodies, but they are not used as efficiently by the RdRp. The Hantaviridae RdRp can also engage in a "prime and realign" mechanism: The host oligonucleotide primes mRNA transcription and initiates transcription with a terminal G residue. After several nucleotides are added, the nascent RNA realigns by moving two nucleotides backwards on the repeated terminal sequence (AUCAUCAUC) so that the host G is once again the first nucleotide, creating a 5' end extension.
An L-ribonucleic acid aptamer (L-RNA aptamer, trade name Spiegelmer) is an RNA-like molecule built from L-ribose units. It is an artificial oligonucleotide named for being a mirror image of natural oligonucleotides. L-RNA aptamers are a form of aptamers. Due to their L-nucleotides, they are highly resistant to degradation by nucleases. L-RNA aptamers are considered potential drugs and are currently being tested in clinical trials.
Sources: en.wikipedia.org
arbuscula, correcting its earlier misassignment and clarifying the status of the others—using historical material alone. In 2025, whole genome sequencing was successfully carried out on historical lichen specimens, including type material, yielding broad genomic coverage for both the fungal and algal partners and allowing genome-wide phylogenetic analysis of the fungal symbiont. Target-capture and genome skimming now recover mitochondrial and chloroplast genomes from both partners, adding new markers for analysis. Photobiont genomics is revealing how frequently algae switch fungal partners (and vice versa). A phylogenomic study of trebouxiophycean green algae showed that lichenization evolved repeatedly in the group and pinpointed stress-tolerance and carbohydrate-exchange gene families that support the symbiosis. Despite recent advances, whole-genome data are still rare in routine lichen taxonomy. By the early 2020s, relatively few lichen-forming fungi had published genomes, and still fewer species descriptions relied on genome-scale evidence. A survey by Lendemer (2021) found that of the hundreds of taxa named in 2018–2020, just one included an organelle genome and metagenomic data. Constraints include cost, limited bioinformatic capacity, and the difficulty of disentangling fungal, algal, and microbial DNA within a single thallus. The outlook is improving as costs fall and new methods such as long-read platforms and lab protocols that separate symbiont DNA become available.
Argon has approximately the same solubility in water as oxygen and is 2.5 times more soluble in water than nitrogen. Argon is colorless, odorless, nonflammable and nontoxic as a solid, liquid or gas. Argon is chemically inert under most conditions and forms no confirmed stable compounds at room temperature. Although argon is a noble gas, it can form some compounds under various extreme conditions. Argon fluorohydride (HArF), a compound of argon with fluorine and hydrogen that is stable below 17 K (−256.1 °C; −429.1 °F), has been demonstrated. Although the neutral ground-state chemical compounds of argon are presently limited to HArF, argon can form clathrates with water when atoms of argon are trapped in a lattice of water molecules. Ions, such as ArH+, and excited-state complexes, such as ArF, have been demonstrated. Theoretical calculation predicts several more argon compounds that should be stable but have not yet been synthesized.
== Clinical implications == Defects in the GnRHR are a cause of hypogonadotropic hypogonadism (HH). Normal puberty begins between ages 8 and 14 in girls and between 9 and 14 in boys. Puberty, however, for some children can come much sooner (precocious puberty) or much later (delayed puberty). In some cases puberty never occurs and thereby contributes to the estimated 35-70 million infertile couples worldwide. Among children, the abnormally early or late onset of puberty exerts intense emotional and social stress that too often goes untreated. The timely onset of puberty is regulated by many factors and one factor that is often referred to as the master regulator of puberty and reproduction is GnRH. This peptide hormone is produced in the hypothalamus but gets secreted and acts upon GnRHRs in the anterior pituitary to exert its effects on reproductive maturation. Understanding how GnRHR functions has been key to developing clinical strategies to treat reproductive-related disorders.
=== Dogs === Hyperthyroidism is much less common in dogs compared to cats. Hyperthyroidism may be caused by a thyroid tumor. This may be a thyroid carcinoma. About 90% of carcinomas are very aggressive; they invade the surrounding tissues and metastasize (spread) to other tissues, particularly the lungs. This has a poor prognosis. Surgery to remove the tumor is often very difficult due to metastasis into arteries, the esophagus, or the windpipe. It may be possible to reduce the size of the tumor, thus relieving symptoms and allowing time for other treatments to work. About 10% of thyroid tumors are benign; these often cause few symptoms. In dogs treated for hypothyroidism (lack of thyroid hormone), iatrogenic hyperthyroidism may occur as a result of an overdose of the thyroid hormone replacement medication, levothyroxine; in this case, treatment involves reducing the dose of levothyroxine. Dogs which display coprophagy, the consumption of feces, and also live in a household with a dog receiving levothyroxine treatment, may develop hyperthyroidism if they frequently eat the feces from the dog receiving levothyroxine treatment. Hyperthyroidism may occur if a dog eats an excessive amount of thyroid gland tissue. This has occurred in dogs fed commercial dog food.
Sources: en.wikipedia.org
Semax is based on the ACTH(4-10) fragment, a seven-amino-acid segment of adrenocorticotropic hormone. The synthetic peptide retains the core sequence while removing regions associated with endocrine activity. This modification is intended to isolate effects on the nervous system.
It is registered for clinical use in Russia and a few other countries, typically as a nasal drop formulation. It does not hold approval from the United States Food and Drug Administration or the European Medicines Agency. Outside those markets it is generally handled as a research chemical.
The compound was developed in Moscow and the earliest studies were conducted there, so the primary literature is largely in Russian-language journals. Translation and indexing have been incomplete, which limits access for outside researchers. Independent groups have since published some work, but the total volume remains modest.
Dry powder is normally held at -20 °C or lower, away from light and moisture. Sealed vials can also be kept at 2-8 °C for shorter intervals. Warming to room temperature before opening prevents condensation.