The short version of peptide synthesis fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-11-18. Anything still debated is marked as such rather than presented as settled.
The C-terminal Pro-Gly-Pro extension is not incidental. Proline-rich tails are known to resist several common peptidases, and the published literature attributes the longer half-life of Semax, relative to unmodified ACTH fragments, to this feature. The modification also removes the melanocyte-stimulating and corticosteroidogenic activity that characterizes longer ACTH-derived sequences. Because the molecule is small and hydrophilic, it is typically formulated as an aqueous solution for intranasal or parenteral delivery. Acetylation or amidation at the termini appears in closely related research peptides and shifts the mass by a fixed increment.
Reported pharmacological work centers on neurotrophic signaling, including changes in BDNF and NGF expression in hippocampal tissue in animal models. Human data come largely from studies conducted in Russia, and how well those results generalize to other populations remains an open question. Regulatory status differs sharply by jurisdiction: Semax is a registered prescription medicine in Russia, while it holds no approved marketing status in the United States or the European Union. Outside such jurisdictions it is generally handled as a research chemical, which affects both documentation and quality expectations.
Semax is a synthetic heptapeptide whose sequence is Met-Glu-His-Phe-Pro-Gly-Pro. It was developed as a fragment analog of adrenocorticotropic hormone, modeled specifically on the ACTH(4-10) region. The first four residues reproduce that fragment, while a Pro-Gly-Pro tripeptide is appended at the C-terminus. Work on the compound originated in Russia, where it entered clinical use as an intranasal preparation. Its sequence places it among short regulatory peptides studied for effects on the central nervous system rather than on the adrenal axis.
Material sold for laboratory use varies widely in stated purity and documentation. A certificate of analysis should list the analytical method, the column and detector used, and the observed purity value. Independent verification by an outside laboratory is the practical way to confirm identity when documentation is absent or internally inconsistent. Regulatory status differs by country, and a product legal in one jurisdiction may be unapproved or controlled in another.
Identity and purity of semax are established with reversed-phase high-performance liquid chromatography coupled to ultraviolet detection, usually at 214 nanometres. Mass spectrometry, most often electrospray ionisation in positive mode, confirms the molecular mass and reveals truncated sequences. Amino acid analysis and peptide mapping after enzymatic digestion provide additional structural confirmation. Laboratories typically report purity as the percentage area of the main peak, a figure that does not capture isomeric or oxidised variants unless the method resolves them.
| Property | Value | Notes |
|---|---|---|
| Molecular weight | ~813.9 Da (free heptapeptide) | N-acetylated form is about 42 Da heavier |
| Residue count | 7 (heptapeptide) | Four residues from ACTH(4-10), three added |
| Appearance | White to off-white powder | Usually supplied lyophilized |
| Solubility class | Freely soluble in water | Also dissolves in DMSO and polar organic solvents |
| Related parent fragment | ACTH(4-10) | Parent motif is Met-Glu-His-Phe |
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.
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.
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.
纯度评估以反相高效液相色谱为主，通过主峰面积百分比给出粗略结果，再配合电喷雾质谱核对分子量。氨基酸分析可验证组成比例，手性色谱或毛细管电泳用于检查残基构型。常见杂质包括缺失序列的短肽、氧化产物与二聚体。由于多数市售品不附带完整检验报告，独立第三方检测常被用来核实标称值。
从分子层面看，Semax 是线性七肽，没有二硫键、糖基或脂链修饰，N 端为游离氨基，C 端为游离羧基。分子含组氨酸与谷氨酸侧链，因此在水和甲醇等极性溶剂中溶解良好，在非极性溶剂中溶解有限。计算分子量约为 814 Da，与其质子化离子的质荷比吻合，可用于质谱确认。
== Oxidative bisulfite sequencing == 5-Methylcytosine and 5-hydroxymethylcytosine both read as a C in bisulfite sequencing. In oxidative bisulfite sequencing (oxBS), Tet is used to convert 5-hydroxymethylcytosine to 5-formylcytosine, which subsequently converts to uracil during bisulfite treatment. The only base that then reads as a C is 5‑methylcytosine, giving a map of the true methylation status in the DNA sample. Levels of 5‑hydroxymethylcytosine can also be quantified by measuring the difference between bisulfite and oxidative bisulfite sequencing. Another method, Tet-assisted oxidative bisulfite sequencing (TAB-Seq) by Chuan He at the University of Chicago, converts the bases differently: 5hmC reads as C, while 5mC and C both read as T. To achieve this, 5hmC bases are first "protected" by conversion to β-glucosyl-5-hydroxymethylcytosine (5gmC). The Tet enzyme is introduced to convert all 5mC to 5caC. Bisulfite then converts both C and 5caC into uracil. 5gmC will be read out like C in PCR amplification.
=== Wine laws and regulations === In the United States, the Alcohol and Tobacco Tax and Trade Bureau (TTB) limits the use of diammonium phosphate as a nitrogen additive to 968 mg/L (8 lbs/1000 gal) which provides 203 mg N/L of YAN. In the European Union, most countries follow the guidelines of the International Organisation of Vine and Wine (OIV) which dictates a limit of 300 mg/L. In Australia, the limit is based on the level of inorganic phosphate with a maximum limit of 400 mg/L of phosphate permitted.
==== Rebuilding links with the West ==== In 1999, Libya began secret talks with the British government to normalize relations. In 2001, Gaddafi publicly condemned the September 11 attacks on the US by al-Qaeda, expressing sympathy with the victims and calling for Libyan involvement in the US-led war on terror against militant Islamism. His government continued suppressing domestic Islamism, at the same time as Gaddafi called for the wider application of sharia law. Libya also cemented connections with China and North Korea, being visited by Chinese President Jiang Zemin in April 2002. However, relations with China became strained in May 2006 due to a visit to Tripoli by Taiwanese President Chen Shui-bian. Influenced by the events of the Iraq War, in December 2003, Libya renounced its possession of weapons of mass destruction, decommissioning its chemical and nuclear weapons programs. Relations with the US improved as a result. British Prime Minister Tony Blair visited Gaddafi in March 2004; the pair developed close personal ties. In 2003, Libya paid US$2.7 billion to the families of the victims of the Lockerbie bombing as it was the condition the US and UK had made for terminating the remaining UN sanctions. Libya continued to deny any role in the bombing. In 2009, Gaddafi attempted to strong-arm global energy companies operating in Libya to cover Libya's settlement with the families of the victims of Lockerbie.
The injury was determined to be caused by the full power of the magnetron; the pulsating sensation was caused either by the stirrer (a mechanical mirror distributing the microwave beam across the oven space to prevent formation of hot and cold spots), or by the arterial pulsation in combination with increased nerve sensitivity. Damage to the A beta fibers, A delta fibers, and group C nerve fibers was the cause of the burning sensation. The increased hypersensitivity to radiant heat is caused by the damage to the A beta, A delta, and polymodal nociceptors (the group C fibers); this damage is induced by a single-time overheating of the skin to 48.5–50 °C, and the resulting sensitivity persists for a long time. Degeneration of the alpha motor neurons is also caused by the exposure to heat and radiation. Most of the major nerve trunks were not affected. Damage to the A beta fibers (located in the skin), discovered by the two-point discrimination test, is permanent; the Pacinian corpuscles, Meissner corpuscles, and Merkel nerve endings, which degenerated after denervation, do not regenerate. The sympathetic nervous system was involved as well; the reduction in active sweat glands was caused by destruction of their innervation, the initial edema and reddening was also caused by sympathetic nerve damage. In 1983, a 35-year-old male was heating a sandwich in a microwave oven at work. After opening the door, the magnetron did not shut off and his right hand was exposed to microwave radiation as he retrieved the sandwich.
A measure to determine the CPU speed. It was invented by Linus Torvalds and is nowadays present on every Linux operating system. However, it is not a meaningful measure to assess the actual CPU performance.
Sources: en.wikipedia.org
==== Employees and DuPont exposed community ==== In 2010, the three members of the C8 Science Panel published a review of the epidemiological evidence on PFOA exposure in Environmental Health Perspectives. Insufficient evidence exists to conclude PFOA causes adverse health effects in humans, but consistent evidence exists on associations with higher cholesterol and uric acid. Whether or not these potential effects result in an increase in cardiovascular disease is unknown. Further data on the 69,030 member cohort that is being studied by the panel is scheduled for release through 2012. A 2011 epidemiological study demonstrated "probable link" between PFOA and kidney cancer, testicular cancer, thyroid disease, high cholesterol, pre-eclampsia and ulcerative colitis. Facial birth defects, an effect observed in rat offspring, occurred with the children of two out of seven female DuPont employees from the Washington Works facility from 1979 to 1981. Bucky Bailey is one of the affected individuals; DuPont, however, does not accept any liability from the toxicity of PFOA. While 3M sent DuPont results from a study that showed birth defects to rats administered PFOA and DuPont moved the women out of the Teflon production unit, subsequent animal testing led DuPont to conclude there was no reproductive risk to women, and they were returned to the production unit. However, data released in March 2009 on the community around DuPont's Washington Works plant showed "a modest, imprecise indication of an elevation in risk ... above the 90th percentile ...
There was a large outbreak of eosinophilia-myalgia syndrome (EMS) in the U.S. in 1989, with more than 1,500 cases reported to the CDC and at least 37 deaths. After preliminary investigation revealed that the outbreak was linked to intake of tryptophan, the U.S. Food and Drug Administration (FDA) recalled tryptophan supplements in 1989 and banned most public sales in 1990, with other countries following suit. Subsequent studies suggested that EMS was linked to specific batches of L-tryptophan supplied by a single large Japanese manufacturer, Showa Denko. It eventually became clear that recent batches of Showa Denko's L-tryptophan were contaminated by trace impurities, which were subsequently thought to be responsible for the 1989 EMS outbreak. However, other evidence suggests that tryptophan itself may be a potentially major contributory factor in EMS. There are also claims that a precursor reached sufficient concentrations to form a toxic dimer. The FDA loosened its restrictions on sales and marketing of tryptophan in February 2001, but continued to limit the importation of tryptophan not intended for an exempted use until 2005. The fact that the Showa Denko facility used genetically engineered bacteria to produce the contaminated batches of L-tryptophan later found to have caused the outbreak of eosinophilia-myalgia syndrome has been cited as evidence of a need for "close monitoring of the chemical purity of biotechnology-derived products".
The concept of "set and setting" also generally appears to be more applicable to psychedelics than to other types of hallucinogens such as deliriants, hypnotics and dissociative anesthetics. Psychedelics include naturally occurring tryptamines like psilocybin and DMT, the naturally occurring phenethylamine mescaline, and naturally occurring lysergamides like ergine (lysergic acid amide; LSA), as well as synthetic analogues and derivatives like LSD and 2C-B. Many of these psychedelics cause remarkably similar effects, despite their different chemical structures. However, many users anecdotally report that the three major families have subjectively different qualities in the "feel" of the experience, which are difficult to describe. There can also be very substantial differences between the drugs; for instance, 5-MeO-DMT rarely produces the visual effects typical of other psychedelics. As additional examples, DiPT is said to primarily affect the auditory sense, 2C-T, 2C-T-17, MiPT, and ASR-3001 (5-MeO-iPALT) are said to produce psychedelic effects on thinking or "head space" with few or no visuals, and N-methyltryptamine (NMT) is said to be a spatial psychedelic. The visuals of psychedelics have been reproduced, with these creations known as psychedelic replications. Some rare individuals do not experience hallucinogenic effects with serotonergic psychedelics.
=== Parathyroid glands === A lateral and ventral view of an embryo showing the third (inferior) and fourth (superior) parathyroid glands during the 6th week of embryogenesis Once the embryo reaches four weeks of gestation, the parathyroid glands begins to develop. The human embryo forms five sets of endoderm-lined pharyngeal pouches. The third and fourth pouch are responsible for developing into the inferior and superior parathyroid glands, respectively. The third pharyngeal pouch encounters the developing thyroid gland and they migrate down to the lower poles of the thyroid lobes. The fourth pharyngeal pouch later encounters the developing thyroid gland and migrates to the upper poles of the thyroid lobes. At 14 weeks of gestation, the parathyroid glands begin to enlarge from 0.1 mm in diameter to approximately 1 – 2 mm at birth. The developing parathyroid glands are physiologically functional beginning in the second trimester. Studies in mice have shown that interfering with the HOX15 gene can cause parathyroid gland aplasia, which suggests the gene plays an important role in the development of the parathyroid gland. The genes, TBX1, CRKL, GATA3, GCM2, and SOX3 have also been shown to play a crucial role in the formation of the parathyroid gland. Mutations in TBX1 and CRKL genes are correlated with DiGeorge syndrome, while mutations in GATA3 have also resulted in a DiGeorge-like syndrome. Malformations in the GCM2 gene have resulted in hypoparathyroidism. Studies on SOX3 gene mutations have demonstrated that it plays a role in parathyroid development.
Sources: en.wikipedia.org
The sequence is Met-Glu-His-Phe-Pro-Gly-Pro, a seven-residue peptide. The first four residues correspond to the ACTH(4-10) fragment, and Pro-Gly-Pro is added at the C-terminus. N-acetylated versions also appear in the literature and differ in mass.
Semax is a synthetic analog of the ACTH(4-10) fragment rather than a copy of the full hormone. Truncation plus the added tail removes the steroidogenic portion of ACTH. That distinction explains why it is studied for nervous-system effects instead of adrenal stimulation.
It is registered as a prescription product in Russia and has been used there clinically, chiefly by the intranasal route. No approval exists in the United States or the European Union. Availability elsewhere typically falls under research-chemical distribution, with varying purity documentation.
Reversed-phase high-performance liquid chromatography is the standard method, with detection in the ultraviolet range. Peak area percentage yields a purity figure for the main component. Mass spectrometry is normally run alongside to confirm molecular identity.