peptide synthesis comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-07-30. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Purity assessment relies mainly on reversed-phase high-performance liquid chromatography, which separates the target heptapeptide from truncated sequences, deletion analogues, and oxidised forms. Mass spectrometry, usually coupled to liquid chromatography, confirms identity through the expected molecular ion and reveals modifications such as methionine sulfoxide formation. Amino acid analysis can verify composition, and tandem mass spectrometry supports sequence confirmation. Ultraviolet detection near 254 to 280 nanometres is convenient because the phenylalanine and histidine residues absorb in that region. Nuclear magnetic resonance is rarely used for routine release testing.
Common degradation pathways include oxidation of the methionine side chain, hydrolysis of the peptide backbone, and aggregation under unfavourable pH or concentration. Stability studies typically monitor the main peak by chromatography and report total related substances as a percentage. Because no official monograph exists, acceptance criteria vary between laboratories, and reported purity values are not directly comparable across suppliers. Analysts therefore document the method, column, and detection wavelength alongside each result, and open questions remain about how much biological activity the oxidised forms retain.
Solid semax is typically supplied as a lyophilised powder that is hygroscopic and sensitive to moisture, light, and repeated temperature cycling. Long-term storage of the dry peptide is generally recommended at approximately -20 degrees Celsius, while shorter working periods may use refrigeration at 2 to 8 degrees Celsius. Vials should remain tightly closed and desiccated when brought to room temperature, because condensation can damage the material before it is weighed. Dividing a batch into aliquots is preferable to thawing one container repeatedly.
| 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 |
Development took place during the 1980s at institutes of the Russian Academy of Sciences, where peptide fragments of ACTH were screened for cognitive and neuroprotective effects. The compound received regulatory approval in Russia as a nasal preparation, marketed for conditions such as ischemic stroke, transient ischemic attacks, and optic nerve disorders. Registration in other countries has not followed. Most published clinical reports originate from a small number of Russian research groups, and independent replication outside that setting remains limited. The regulatory status therefore differs sharply between Russia and the rest of the world.
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.
常规纯度与身份确认依赖反相高效液相色谱，并辅以质谱测定分子量。氨基酸组成分析可用于验证序列构成，肽图分析则能进一步定位修饰或降解产物。杂质谱通常关注缺失序列肽、截短片段和氧化产物。不同方法的检出限并不相同，因此各实验室报告的纯度数值不宜直接横向比较。
多数实验室与市售的 Semax 以冻干粉形式提供。冻干粉通常建议保存在 -20 °C 或更低温度下，同时避免光照与反复升温。短期运输有时采用冷藏条件，但长期保存仍以冷冻为主。分包操作应尽量减少开盖次数，以降低吸湿和微生物污染的风险。开封后若未一次用完，建议在干燥环境中密封并尽快放回低温储存。
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 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.
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。
稳定性主要由水解与氧化两条路径支配。肽键在中性或弱酸性条件下相对稳定，遇到强碱或长时间高温则明显断裂；甲硫氨酸侧链容易被氧化成亚砜，使主峰前移并拉低实际含量。金属离子、光照和反复冻融会进一步促进降解或聚集。冻干粉在低温避光条件下可存放较长时间，配制后的水溶液通常需要冷藏并尽快用完。
=== Home media === Following its cinematic release in the late 1980s, the film was released to television in a syndicated two-night broadcast. Extra footage was added to the film to fill in the block of time. The film was later released in VHS video format on 5 May 1998. The Region 1 widescreen edition of the film was released on DVD in the United States on 23 February 1999. Special features for the DVD include: production notes, cast and filmmakers' biographies, film highlights, web links, and the theatrical cinematic. It was released on Blu-ray Disc by Umbrella Entertainment in Australia in 2019, and in 2020 by Kino Lorber in the US. It is also available in other media formats such as video on demand.
==== MeSH D12.125.070 – amino acids, branched-chain ==== MeSH D12.125.070.075 – aminoisobutyric acids MeSH D12.125.070.577 – isoleucine MeSH D12.125.070.637 – leucine MeSH D12.125.070.950 – valine MeSH D12.125.070.950.100 – 2-amino-5-phosphonovalerate
The crab is defined as the intensity of X-rays emitted from the Crab Nebula at a given photon energy up to 30 kiloelectronvolts. The Crab Nebula is often used for calibration of X-ray telescopes. For measuring the X-ray intensity of a less energetic source, the milliCrab (mCrab) may be used. One crab is approximately 24 pW/m2.
The NADH formed in the third oxidative step cannot be reoxidized in the peroxisome, so reducing equivalents are exported to the cytosol. β-oxidation in the peroxisome requires the use of a peroxisomal carnitine acyltransferase (instead of carnitine acyltransferase I and II used by the mitochondria) for transport of the activated acyl group into the mitochondria for further breakdown. The first oxidation step in the peroxisome is catalyzed by the enzyme acyl-CoA oxidase. The β-ketothiolase used in peroxisomal β-oxidation has an altered substrate specificity, different from the mitochondrial β-ketothiolase. Peroxisomal oxidation is induced by a high-fat diet and administration of hypolipidemic drugs like clofibrate.
Sources: en.wikipedia.org
=== Cysteine and cystine === As the functional group of the proteinogenic amino acid cysteine, the thiol group plays a very important role in biology. When the thiol groups of two cysteine residues (as in monomers or constituent units) are brought near each other in the course of protein folding, an oxidation reaction can generate a cystine unit with a disulfide bond (−S−S−). Disulfide bonds can contribute to a protein's tertiary structure if the cysteines are part of the same peptide chain, or contribute to the quaternary structure of multi-unit proteins by forming fairly strong covalent bonds between different peptide chains. A physical manifestation of cysteine-cystine equilibrium is provided by hair straightening technologies. Sulfhydryl groups in the active site of an enzyme can form noncovalent bonds with the enzyme's substrate as well, contributing to covalent catalytic activity in catalytic triads. Active site cysteine residues are the functional unit in cysteine protease catalytic triads. Cysteine residues may also react with heavy metal ions (Zn2+, Cd2+, Pb2+, Hg2+, Ag+) because of the high affinity between the soft sulfide and the soft metal (see hard and soft acids and bases). This can deform and inactivate the protein, and is one mechanism of heavy metal poisoning.
=== Reverse transcription === Reverse transcribing viruses replicate their genomes by reverse transcribing DNA copies from their RNA; these DNA copies are then transcribed to new RNA. Retrotransposons also spread by copying DNA and RNA from one another, and telomerase contains an RNA that is used as template for building the ends of eukaryotic chromosomes.
=== Campaign methods === Unlike the other major candidates, Sanders relied on small-dollar donations. His presidential campaign raised $1.5 million within 24 hours of his official announcement. At the end of the year, the campaign had raised a total of $73 million from more than one million people, making 2.5 million donations, with an average donation of $27.16. The campaign reached 3.25 million donations by the end of January 2016, raising $20 million in that month alone. Sanders used social media to help his campaign gain momentum, posting content to online platforms such as Twitter and Facebook and answering questions on Reddit. He gained a large grassroots organizational following online. A July 29, 2015, meetup organized online brought 100,000 supporters to more than 3,500 simultaneous events nationwide. To his surprise, Sanders's June 2015 campaign events drew overflow crowds across the country. When Clinton and Sanders made public appearances within days of each other in Des Moines, Iowa, he drew larger crowds, even though he had already made many stops around the state and Clinton's visit was her first in 2015. On July 1, 2015, his campaign stop in Madison, Wisconsin, drew the largest crowd of any 2016 presidential candidate to that date, with an estimated turnout of 10,000. Over the following weeks, he drew even larger crowds: 11,000 in Phoenix; 15,000 in Seattle; and 28,000 in Portland, Oregon.
=== Polymer shell protein core === A polymer shell is formed by conjugation of multiple molecules of polymers onto the protein core. The polymer shell can either protect the protein core from unwanted degradation or create desired interactive sites for guest molecules. The first generation of polymer shell protein core structures mainly used of Polyethylene glycol (PEG) chains to increase the hydrodynamic radius and reduce immune response to proteins. However, the PEG shell can reduce protein activity in the inner core. More advanced designs use biodegradable linkers to achieve programmed release of the protein core in specific tissues. Several therapeutic designs with biodegradable PEG shells are already being developed in vivo. Direct conjugation of polymers ("grafting to" strategy) can efficiently construct a polymer shell with diverse polymer types, however, it has low polymer density, especially with large polymers. In contrast, "grafting from" strategy allows the formation of a dense and uniform polymer shell. The protein core can also function as a carrier for other therapeutic molecules, such as plasmid DNA. Dendrite polymer shells have a high volume to molecular weight ratio compared with traditional polymer shells. Using branched carbohydrates can give unique biological properties while maintaining molecular definition.
=== Definition by Waterlow === In the 1970s, John Conrad Waterlow established a new classification system for malnutrition. Instead of using just weight for age measurements, Waterlow's system combines weight-for-height (indicating acute episodes of malnutrition) with height-for-age to show the stunting that results from chronic malnutrition. One advantage of the Waterlow classification is that weight for height can be calculated even if a child's age is unknown.
Sources: en.wikipedia.org
Haemophilus influenzae (formerly called Pfeiffer's bacillus or Bacillus influenzae) is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria are mesophilic and grow best at temperatures between 35 and 37 °C. H. influenzae was first described in 1893 by Richard Pfeiffer during an influenza pandemic when he incorrectly identified it as the causative microbe, which is why the bacterium was given the name "influenzae". H. influenzae is responsible for a wide range of localized and invasive infections, typically in infants and children, including pneumonia, meningitis, or bloodstream infections. Treatment consists of antibiotics; however, H. influenzae is often resistant to the penicillin family, but amoxicillin/clavulanic acid can be used in mild cases. Serotype B H. influenzae (hib) can cause illness, called Hib infections, among other names. It has been a major cause of meningitis in infants and small children, frequently causing deafness and mental degradation. However, the development in the 1980s of a vaccine effective in this age group (the Hib vaccine) has almost eliminated this in developed countries. This species was the first organism to have its entire genome sequenced.
120 g acetic acid (60 g/mol, 2.0 mol) was reacted with 230 g ethanol (46 g/mol, 5.0 mol), yielding 132 g ethyl acetate (88 g/mol, 1.5 mol). The yield was 75%. The molar amount of the reactants is calculated from the weights (acetic acid: 120 g ÷ 60 g/mol = 2.0 mol; ethanol: 230 g ÷ 46 g/mol = 5.0 mol). Ethanol is used in a 2.5-fold excess (5.0 mol ÷ 2.0 mol). The theoretical molar yield is 2.0 mol (the molar amount of the limiting compound, acetic acid). The molar yield of the product is calculated from its weight (132 g ÷ 88 g/mol = 1.5 mol). The % yield is calculated from the actual molar yield and the theoretical molar yield (1.5 mol ÷ 2.0 mol × 100% = 75%).
=== Acquired === Methemoglobinemia may be acquired. Classical drug causes of methemoglobinemia include various antibiotics (trimethoprim, sulfonamides, and dapsone), local anesthetics (especially articaine, benzocaine, prilocaine, and lidocaine), and aniline dyes, metoclopramide, rasburicase, umbellulone, chlorates, bromates, and nitrites. Nitrates are suspected to cause methemoglobinemia. In otherwise healthy individuals, the protective enzyme systems normally present in red blood cells rapidly reduce the methemoglobin back to hemoglobin and hence maintain methemoglobin levels at less than one percent of the total hemoglobin concentration. Exposure to exogenous oxidizing drugs and their metabolites (such as benzocaine, dapsone, and nitrates) may lead to an increase of up to a thousandfold of the methemoglobin formation rate, overwhelming the protective enzyme systems and acutely increasing methemoglobin levels. Infants under six months of age have lower levels of a key methemoglobin reduction enzyme (NADH-cytochrome b5 reductase) in their red blood cells. This results in a major risk of methemoglobinemia caused by nitrates ingested in drinking water, dehydration (usually caused by gastroenteritis with diarrhea), sepsis, or topical anesthetics containing benzocaine or prilocaine resulting in blue baby syndrome. Nitrates used in agricultural fertilizers may leak into the ground and may contaminate well water. The current EPA standard of 10 ppm nitrate-nitrogen for drinking water is specifically set to protect infants.
Rönnberg also filmed himself firing various guns at a shooting range to make the gun animations more authentic. Throughout the mod's development, Team Psykskallar released "videocasts" on the Mod DB page for Cry of Fear, which were medium-length videos that documented the team's development on the mod, as well as showcased new and improved features. The videos consisted of various team members, but most notably Rönnberg, Marchant, and Sydtangen.
==== Recombinant DNA ==== Biotechnology in the modern sense of genetic engineering began in the 1970s, with the invention of recombinant DNA techniques. Restriction enzymes were discovered and characterized in the late 1960s, following on the heels of the isolation, then duplication, then synthesis of viral genes. Beginning with the lab of Paul Berg in 1972 (aided by EcoRI from Herbert Boyer's lab, building on work with ligase by Arthur Kornberg's lab), molecular biologists put these pieces together to produce the first transgenic organisms. Soon after, others began using plasmid vectors and adding genes for antibiotic resistance, greatly increasing the reach of the recombinant techniques. Wary of the potential dangers (particularly the possibility of a prolific bacteria with a viral cancer-causing gene), the scientific community as well as a wide range of scientific outsiders reacted to these developments with both enthusiasm and fearful restraint. Prominent molecular biologists led by Berg suggested a temporary moratorium on recombinant DNA research until the dangers could be assessed and policies could be created. This moratorium was largely respected, until the participants in the 1975 Asilomar Conference on Recombinant DNA created policy recommendations and concluded that the technology could be used safely. Following Asilomar, new genetic engineering techniques and applications developed rapidly. DNA sequencing methods improved greatly (pioneered by Frederick Sanger and Walter Gilbert), as did oligonucleotide synthesis and transfection techniques.
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.
Dry powder is usually kept at about -20 degrees Celsius for long-term storage and at 2 to 8 degrees Celsius for short working periods. Containers should stay sealed and protected from light and moisture to limit degradation.