Semax raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-02-08 and is reviewed periodically as new material appears.
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.
Development of the compound took place in the Soviet Union during the 1980s, largely through peptide research groups affiliated with the Shemyakin-Ovchinnikov Institute and Moscow State University. Investigators screened fragments of adrenocorticotropic hormone for activity on the central nervous system while attempting to separate cognitive effects from hormonal ones. The shortened sequence was selected because it retained behavioral activity in animal models without stimulating corticosteroid release. Early publications described the molecule as an ACTH(4-10) analog.
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.
Development is attributed to researchers at the Institute of Molecular Genetics in Moscow during the early 1980s, building on earlier Soviet work with ACTH fragments. Russian regulatory approval followed for intranasal use, and the compound has remained commercially available there for decades. Most published human data originate from Russian and, later, some Eastern European clinical reports, which are not always accessible in English translation. Outside that region the material is generally handled as a research chemical rather than a licensed medicine.
Regulatory status differs sharply between jurisdictions. In Russia the peptide is registered as a prescription nasal preparation, while agencies such as the United States Food and Drug Administration have not approved it for any indication. Products sold elsewhere are typically labeled for laboratory research only, and such labels shift responsibility for safe handling to the purchaser. Because the same name covers pharmaceutical-grade nasal drops and bulk research powder, identity and purity documentation becomes the main practical concern when comparing sources.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C37H51N9O10S | Seven-residue peptide |
| Molecular mass | 813.9 Da | Monoisotopic value |
| Appearance | White to off-white powder | Lyophilized form |
| Solubility | Freely soluble in water | Also soluble in saline and polar solvents |
| Storage (dry) | -20 °C or lower | Desiccated, protected from light |
各国监管态度分化明显。俄罗斯按处方药管理，部分东欧国家留有使用记录；欧盟与美国未批准其作为药物上市，市面流通品通常标注为研究用化学品。身份差异意味着标示含量、纯度与无菌性缺少统一核查。体育领域还牵涉反兴奋剂名录，跨境携带则受目的地药品法规约束。
Semax 是人工设计的七肽，序列为 Met-Glu-His-Phe-Pro-Gly-Pro，骨架取自促肾上腺皮质激素片段 ACTH(4-10)。它于二十世纪八十年代在苏联的分子遗传学研究机构内合成。设计目标是保留该片段与注意力和记忆相关的活性，同时剔除促皮质激素释放等内分泌作用。此后俄罗斯将其登记为药品并进入临床使用。
当时的短肽研究普遍关注能否穿越血脑屏障、在低剂量下产生中枢效应，Semax 属于这一路线。鼻内给药是其主要使用方式，俄语文献报道的适应症涵盖缺血性卒中、短暂性脑缺血发作、认知功能减退以及视神经病变。这些研究大多发表在当地期刊上，样本规模与终点设置同西方试验惯例存在差异，国际同行对其临床证据的强度看法不一。
Laboratory descriptions of the material are consistent across suppliers. It appears as a white to off-white lyophilized powder that dissolves readily in water and in polar organic solvents such as dimethyl sulfoxide. Aqueous solutions are clear and colorless at low concentrations. Because the peptide contains methionine, oxidation at the sulfur atom is a recognized degradation pathway, and handling notes usually call for protected, desiccated storage. Reported purity for research-grade lots is generally above 95 percent as measured by reversed-phase high-performance liquid chromatography.
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 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.
The heavy isotope plutonium-244 has a half-life long enough that extreme trace quantities should have survived primordially (from the Earth's formation) to the present, but so far experiments have not yet been sensitive enough to detect it. Both plutonium-239 and plutonium-241 are fissile, meaning they can sustain a nuclear chain reaction, leading to applications in nuclear weapons and nuclear reactors. Plutonium-240 has a high rate of spontaneous fission, raising the neutron flux of any sample containing it. The presence of plutonium-240 limits a plutonium sample's usability for weapons or its quality as reactor fuel, and the percentage of plutonium-240 determines its grade (weapons-grade, fuel-grade, or reactor-grade). Plutonium-238 has a half-life of 87.7 years and emits alpha particles. It is a heat source in radioisotope thermoelectric generators, which are used to power some spacecraft. Plutonium isotopes are expensive and inconvenient to separate, so particular isotopes are usually manufactured in specialized reactors. Producing plutonium in useful quantities for the first time was a major part of the Manhattan Project during World War II that developed the first atomic bombs. The Fat Man bombs used in the Trinity nuclear test in July 1945, and in the bombing of Nagasaki in August 1945, had plutonium cores. Human radiation experiments studying plutonium were conducted without informed consent, and several criticality accidents, some lethal, occurred after the war.
== Signal transduction pathway == A glucagon receptor, upon binding with the signaling molecule glucagon, initiates a signal transduction pathway that begins with the activation of adenylate cyclase, which in turn produces cyclic AMP (cAMP). Protein kinase A, whose activation is dependent on the increased levels of cAMP, is responsible for the ensuing cellular response in the form of protein kinase 1 and 2. The ligand-bound glucagon receptor can also initiate a concurrent signaling pathway that is independent of cAMP by activating phospholipase C. Phospholipase C produces DAG and IP3 from PIP2, a phospholipid phospholipase C cleaves off of the plasma membrane. Ca2+ stores inside the cell release Ca2+ when its calcium channels are bound by IP3.
No. 237 Squadron, based in Kenya since before the start of the war, had expanded to 28 officers and 209 other ranks by March 1940. By mid-1940, most of the officers and men Southern Rhodesia had sent overseas were in Kenya, attached to various East African formations, the King's African Rifles (KAR), the RWAFF, or to the colony's own Medical Corps or Survey Unit. The Southern Rhodesian surveyors charted the previously unmapped area bordering Abyssinia and Italian Somaliland between March and June 1940, and the Medical Corps operated No. 2 General Hospital in Nairobi from July. A company of coloured and Indian-Rhodesian transport drivers was also in the country, having arrived in January. The first Southern Rhodesian contingent despatched to North Africa and the Middle East was a draft of 700 from the Rhodesia Regiment who left in April 1940. No white Rhodesian force of this size had ever left the territory before. They were posted to a variety of British units across Egypt and Palestine. The largest concentration of Rhodesian soldiers in North Africa belonged to the King's Royal Rifle Corps (KRRC), whose connections with the colony dated back to World War I. Several Rhodesian platoons were formed in the KRRC's 1st Battalion in the Western Desert. A company of men from the Southern Rhodesian Signal Corps was also present, operating in tandem with the British Royal Corps of Signals.
Abdel Fattah al-Burhan Abdelrahman al-Burhan (born 11 July 1960) is a Sudanese military officer who has been the leader of Sudan since 2019. Following the Sudanese Revolution in April 2019, he was handed control of the military junta, the Transitional Military Council, a day after it was formed, due to protesters' dissatisfaction with the establishment ties of initial leader Ahmed Awad Ibn Auf. He served as chairman of the TMC until a draft constitutional declaration signed with civilians went into effect on 17 August and a collective head of state Transitional Sovereignty Council was formed on 21 August, also to be initially headed by al-Burhan. The 2020 Juba Agreement allowed al-Burhan to continue to lead the Sovereignty Council for another 20 months, rather than stepping down as planned in February 2021. Al-Burhan seized power in a coup d'état in October 2021, dissolved the Sovereignty Council, and reconstituted it the following month with new membership, keeping himself as chairman. He was formerly the General Inspector of the Sudanese Armed Forces (SAF). He is leading the SAF against the Rapid Support Forces (RSF) in the ongoing Sudanese civil war. Al-Burhan survived an assassination attempt in July 2024.
Sources: en.wikipedia.org
The gamma-emitting isotopes iodine-123 (half-life 13.223 hours), and (less commonly) the longer-lived and less energetic iodine-125 (half-life 59.392 days) are used as nuclear imaging tracers to evaluate the anatomic and physiologic function of the thyroid. Abnormal results may be caused by disorders such as Graves' disease or Hashimoto's thyroiditis. Both isotopes decay by electron capture (EC) to the corresponding tellurium nuclides, but in neither case are these the metastable nuclides 123mTe and 125mTe (which are of higher energy, and are not produced from radioiodine). Instead, the excited tellurium nuclides decay immediately (half-life too short to detect). Following EC, the excited 123Te from 123I emits a high-speed 127 keV internal conversion electron (not a beta ray) about 13% of the time, but this does little cellular damage due to the nuclide's short half-life and the relatively small fraction of such events. In the remainder of cases, a 159 keV gamma ray is emitted, which is well-suited for gamma imaging. Excited 125Te resulting from electron capture of 125I also emits a much lower-energy internal conversion electron (35.5 keV), which does relatively little damage due to its low energy, even though its emission is more common. The relatively low-energy gamma from 125I/125Te decay is poorly suited for imaging, but can still be seen, and this longer-lived isotope is necessary in tests that require several days of imaging, for example, fibrinogen scan imaging to detect blood clots.
There is evidence from both human and animal studies that inhalation exposure to ethylene oxide can result in a wide range of carcinogenic effects. Ethylene oxide is toxic by inhalation, with a US OSHA permissible exposure limit calculated as a TWA (time weighted average) over 8 hours of 1 ppm, and a short term exposure limit (excursion limit) calculated as a TWA over 15 minutes of 5 ppm. At concentrations in the air about 200 parts per million, ethylene oxide irritates mucous membranes of the nose and throat; higher contents cause damage to the trachea and bronchi, progressing into the partial collapse of the lungs. High concentrations can cause pulmonary edema and damage the cardiovascular system; the damaging effect of ethylene oxide may occur only after 72 hours after exposure. The maximum content of ethylene oxide in the air according to the US standards (ACGIH) is 1.8 mg/m3 (0.00079 gr/cu ft). NIOSH has determined that the Immediately Dangerous to Life and Health level (IDLH) is 800 ppm. Because the odor threshold for ethylene oxide varies between 250 and 700 ppm, the gas is already at toxic concentrations when it can be smelled. Even then, the odor of ethylene oxide is sweet and aromatic and can easily be mistaken for the aroma of diethyl ether, a common laboratory solvent of very low toxicity. In view of these insidious properties, continuous electrochemical monitoring is standard practice, and it is forbidden to use ethylene oxide to fumigate building interiors in the EU and some other jurisdictions.
== Regulation == While most steps in gluconeogenesis are the reverse of those found in glycolysis, three regulated and strongly endergonic reactions are replaced with more kinetically favorable reactions. Hexokinase/glucokinase, phosphofructokinase, and pyruvate kinase enzymes of glycolysis are replaced with glucose-6-phosphatase, fructose-1,6-bisphosphatase, and PEP carboxykinase/pyruvate carboxylase. These enzymes are typically regulated by similar molecules, but with opposite results. For example, acetyl CoA and citrate activate gluconeogenesis enzymes (pyruvate carboxylase and fructose-1,6-bisphosphatase, respectively), while at the same time inhibiting the glycolytic enzyme pyruvate kinase. This system of reciprocal control allow glycolysis and gluconeogenesis to inhibit each other and prevents a futile cycle of synthesizing glucose to only break it down. Pyruvate kinase can be also bypassed by 86 pathways not related to gluconeogenesis, for the purpose of forming pyruvate and subsequently lactate; some of these pathways use carbon atoms originated from glucose. The majority of the enzymes responsible for gluconeogenesis are found in the cytosol; the exceptions are mitochondrial pyruvate carboxylase and, in animals, phosphoenolpyruvate carboxykinase. The latter exists as an isozyme located in both the mitochondrion and the cytosol. The rate of gluconeogenesis is ultimately controlled by the action of the enzyme fructose-1,6-bisphosphatase, which is also regulated through signal transduction by cAMP and its phosphorylation.
== Protein databases == The Human Protein Atlas contains information about the human proteins in cells, tissues, and organs. All the data in the knowledge resource is open access to allow scientists both in academia and industry to freely access the data for exploration of the human proteome. The organization ELIXIR has selected the protein atlas as a core resource due to its fundamental importance for a wider life science community. The Plasma Proteome database Archived 2021-01-27 at the Wayback Machine contains information on 10,500 blood plasma proteins. Because the range in protein contents in plasma is very large, it is difficult to detect proteins that tend to be scarce when compared to abundant proteins. This is an analytical limit that may possibly be a barrier for the detections of proteins with ultra low concentrations. Databases such as neXtprot and UniProt are central resources for human proteomic data.
An embalmer is someone who has been trained and qualified in the art and science of sanitization, presentation, and preservation of the human deceased. The term mortician is far more generic; it may refer to someone who is a funeral director, an embalmer, or just a person who prepares the deceased, with or without the formal qualification of an embalmer. Thus while all embalmers are morticians, many morticians are not embalmers and the terms are not intrinsically synonymous. Embalming training commonly involves formal study in anatomy, thanatology, chemistry, and specific embalming theory (to widely varied levels depending on the region of the world one lives in) combined with practical instruction in a mortuary with a resultant formal qualification granted after the passing of a final practical examination and acceptance into a recognized society of professional embalmers. The roles of a funeral director and embalmer are different, depending on local customs and the licensing body of the region in which they both operate. A funeral director arranges for the final disposition of the deceased, and may or may not prepare the deceased (by embalming, preparing for viewing or other legal requirements). Legal requirements over who can practice vary geographically. Some regions or countries do not have specific requirements, while others have clear prohibitions. In the United States, the title of an embalmer is largely based on the state in which they are licensed.
Sources: en.wikipedia.org
=== Resistance === Three mechanisms of resistance to chloramphenicol are known: reduced membrane permeability, mutation of the 50S ribosomal subunit, and elaboration of chloramphenicol acetyltransferase. It is easy to select for reduced membrane permeability to chloramphenicol in vitro by serial passage of bacteria, and this is the most common mechanism of low-level chloramphenicol resistance. High-level resistance is conferred by the cat-gene; this gene codes for an enzyme called chloramphenicol acetyltransferase, which inactivates chloramphenicol by covalently linking one or two acetyl groups, derived from acetyl-S-coenzyme A, to the hydroxyl groups on the chloramphenicol molecule. The acetylation prevents chloramphenicol from binding to the ribosome. Resistance-conferring mutations of the 50S ribosomal subunit are rare. Chloramphenicol resistance may be carried on a plasmid that also codes for resistance to other drugs. One example is the ACCoT plasmid (A=ampicillin, C=chloramphenicol, Co=co-trimoxazole, T=tetracycline), which mediates multiple drug resistance in typhoid (also called R factors). As of 2014 some Enterococcus faecium and Pseudomonas aeruginosa strains are resistant to chloramphenicol. Some Veillonella spp. and Staphylococcus capitis strains have also developed resistance to chloramphenicol to varying degrees. Some other resistance genes beyond cat are known, such as chloramphenicol hydrolase, and chloramphenicol phosphotransferase.
==== Bacterial proteasomes ==== Actinobacteria have acquired a proteasome degradation pathway, including its own 20S core particle and a AAA protein motor, MPA (mycobacterial proteasome activator). Unlike the base subcomplex of the 19S, MPA is a homohexameric motor complex, containing the ATPase sites, a tandem (oligosaccharide/oligonucleotide-binding) OB ring, and Coiled coils that extend off N-termini off the OB ring. The C-terminus contains HBXY motifs that contact the 20S core particle in a similar way as with other regulatory particles. Targeting to MPA requires a prokaryotic protein, Prokaryotic ubiquitin-like protein (or Pup) that functions as ubiquitin as a tag that can be attached to a protein substrate, though the structure of Pup is unrelated to that of ubiquitin. Once attached, a puplyated protein can be targeted to MPA through the coiled-coil and can be directed through the AAA motor into the 20S for degradation.
intermetallic A type of alloy that forms an ordered solid-state compound between two or more metallic elements. Intermetallics are generally hard and brittle, and have useful mechanical properties at high temperatures.
Therapeutic, diagnostic and preventive monoclonal antibodies are clones of a single parent cell. When used as drugs, the International Nonproprietary Names (INNs) end in -mab. The remaining syllables of the INNs, as well as the column Source, are explained in Nomenclature of monoclonal antibodies.
Sources: en.wikipedia.org
It is a synthetic peptide of seven amino acids. Its backbone corresponds to a fragment of adrenocorticotropic hormone extended at the carboxyl end. The material is distributed as a lyophilized solid for laboratory use.
The extension was introduced to slow enzymatic breakdown of the peptide in biological systems. Natural ACTH fragments are degraded rapidly by peptidases. Adding the tripeptide was intended to extend the window during which the molecule remains intact.
Most published work consists of animal experiments conducted in a small number of laboratories. Human data are limited in number and size. Whether the observed effects translate into reliable clinical benefit is still unresolved.
It is a short synthetic peptide built from seven amino acids: methionine, glutamic acid, histidine, phenylalanine and three prolines. The sequence derives from the 4-10 fragment of adrenocorticotropic hormone with an added proline-glycine-proline tail. No plant or animal extract is involved; the material is produced by solid-phase peptide synthesis.