synthetic heptapeptide 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.
Last reviewed on 2025-09-08. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
溶液状态的稳定性明显低于冻干粉。肽类在水溶液中可能经历水解、氧化与聚集，其中甲硫氨酸和天冬酰胺等残基常是敏感位点。Semax 含有甲硫氨酸，因此氧化风险相对突出。工作液一般主张现配现用，或冷藏并在数日内用尽。缓冲液种类、pH 和离子强度都会影响降解速率，而关于最佳条件的公开数据并不统一。
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。
| 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 |
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.
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.
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。
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。
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.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. Its chain combines the first seven residues of corticotropin with a C-terminal proline-glycine-proline extension, a modification intended to slow enzymatic breakdown. The free peptide has a molecular mass near 813.9 daltons. It belongs to the class of ACTH-derived fragments studied for central nervous system activity rather than for adrenal steroid stimulation. This structural relationship to a natural hormone fragment is the usual starting point for describing the compound in the literature.
Published studies are dominated by animal models of stroke, ischemia, and cognitive impairment, with a smaller number of human trials conducted in Russia. Many of the human reports are small, single-center, and published in Russian-language journals, which limits independent scrutiny. Outcome measures vary between studies and often rely on clinician-rated scales rather than objective biomarkers. Systematic reviews have noted the methodological weaknesses and called for larger, preregistered trials before firm conclusions can be drawn.
Claims about enhanced focus, memory, or mood in healthy people rest mostly on anecdotal reports and community discussion rather than on controlled data. It remains unclear whether any cognitive benefit observed in patients recovering from brain injury would extend to uninjured users. Dose-response relationships, long-term safety, and interactions with other drugs are not well characterized in the peer-reviewed literature. Questions about optimal route of administration and treatment duration likewise remain open.
Semax binds to melanocortin receptors and is thought to influence neuronal survival and plasticity rather than to act through the adrenal axis. Laboratory work has shown increased expression of brain-derived neurotrophic factor and nerve growth factor in treated tissue. Changes in c-Fos, a marker of neuronal activation, have also been reported. Because the peptide is rapidly degraded by peptidases, its effects are generally attributed to downstream signaling cascades rather than to sustained receptor occupancy.
Pharmacology is the science of drugs and medications, including a substance's origin, composition and interaction with biological systems; specifically through pharmacokinetics, pharmacodynamics, therapeutic use, and toxicology. The discipline examines these interactions through pharmacokinetics (what the body does to the drug) and pharmacodynamics (what the drug does to the body), both of which determine how a substance alters normal or abnormal biochemical function. Substances with medicinal properties are classified as pharmaceuticals, while the term drug encompasses any chemical agent that alters biological processes. Nanopharmacology is the specialization of pharmacology in the nanoscale. The field encompasses drug composition and properties, functions, sources, medicinal chemistry, drug design, molecular and cellular mechanisms, organ/systems mechanisms, signal transduction/cellular communication, molecular diagnostics, interactions, chemical biology, therapy, medical applications, toxicology, and antipathogenic capabilities. The two main areas of pharmacology are pharmacodynamics and pharmacokinetics. Pharmacodynamics studies the effects of a drug on biological systems, and pharmacokinetics studies the effects of biological systems on a drug. In broad terms, pharmacodynamics discusses the chemicals with biological receptors, and pharmacokinetics discusses the liberation, absorption, distribution, metabolism, and excretion (LADME) of chemicals from the biological systems. Pharmacology is not synonymous with pharmacy, though the two terms are frequently confused.
=== C-Acylation === Formation of the 2,5-diketopiperazine ring by enolate acylation was used in the construction of the 2,5-diketopiperazine ring in 11 by intramolecular cyclization of the enolate of 10 onto the carbonyl of the phenyl carbamate to give 11 in 90% yield.
Functional KORs are present on nerve terminals of both oxytocin and vasopressin neurons in the rat neurohypophysis, where agonists inhibit potassium-evoked hormone release. Both dynorphin1-8 and (1–17) suppress stimulated oxytocin release from isolated neurosecretory endings, with effects on the initial and secondary peaks of hormone secretion, while exerting no influence on vasopressin release under similar conditions. These interactions extend to plasma hormone levels, where KOR agonists decrease circulating oxytocin concentrations, while antagonists increase oxytocin release, suggesting that KOR signaling mediates negative regulation of oxytocin secretion during stress or physiological challenges.
The small-pox so fatal and so general amongst us is here entirely harmless by the invention of ingrafting (which is the term they give it). There is a set of old women who make it their business to perform the operation. Every autumn in the month of September, when the great heat is abated, people send to one another to know if any of their family has a mind to have the small-pox. They make parties for this purpose, and when they are met (commonly fifteen or sixteen together) the old woman comes with a nutshell full of the matter of the best sort of small-pox and asks what veins you please to have opened. She immediately rips open that you offer to her with a large needle (which gives you no more pain than a common scratch) and puts into the vein as much venom as can lye upon the head of her needle, and after binds up the little wound with a hollow bit of shell, and in this manner opens four or five veins. ... The children or young patients play together all the rest of the day and are in perfect health till the eighth. Then the fever begins to seize them and they keep their beds two days, very seldom three. They have very rarely above twenty or thirty in their faces, which never mark, and in eight days time they are as well as before the illness. ... There is no example of any one that has died in it, and you may believe I am very well satisfied of the safety of the experiment since I intend to try it on my dear little son.
Sources: en.wikipedia.org
Dracaena cinnabari, the Socotra dragon tree, or dragon blood tree, is a dragon tree native to the Socotra archipelago, part of Yemen, located in the Arabian Sea. It is named after the blood-like color of the red sap that the trees produce. It is also the national tree of Yemen.
=== Ground transportation === The passenger terminal can be accessed from Interstate 240 via Plough Boulevard and Jim McGehee Parkway. It can also be reached via Winchester Road. The airport is served by the Memphis Area Transit Authority route 28 bus, which offers service to Hudson Transit Center in downtown Memphis, as well as Airways Transit Center. The Ground Transportation Center, completed in March 2013, contains the airport's economy parking and parking for all car rental companies. It is seven stories tall and features 4,500 economy parking spaces and 1,200 rental car spaces.
== History == Pachamanca dates back to pre-incan times, used in religious festivities and celebrations. It was made as a way to give back to the Incan earth goddess Pachamama. In certain parts of the country, this dish has a godmother and a godfather who are in charge of placing a cross and flowers on the buried food, which is a traditional custom in Andean festivals and celebrations. The definition of pachamanca is the combination of the words pacha and manca, pacha (earth) and manca (cooking pot). The heated stones symbolize Inti, the Sun God, and the source of warmth. The tradition of burying the food underground signifies a return to the womb of Pachamama. A band of musicians usually accompanies the proceedings, while chicha and beer are also served.
A poll found that California voters thought the most important issue for Newsom and the state legislature to work on in 2020 was homelessness. In his first week of office, Newsom threatened to withhold state funding for infrastructure to communities that failed to take actions to alleviate California's housing shortage. In late January 2019, he announced that he would sue Huntington Beach for preventing the construction of affordable housing. A year later, the city acted to settle the lawsuit by the state. Newsom opposes NIMBY (not-in-my-back-yard) sentiment, declaring in 2022 that "NIMBYism is destroying the state". In 2021, he signed a pair of bills into law that made zoning regulations for housing less restrictive, allowing construction of duplexes and fourplexes in lots that were previously zoned exclusively for single-family homes. Newsom also signed a bill that expedites the environmental review process for new multifamily developments worth at least $15,000,000. To participate, developers must apply directly through the governor's office. In 2022, Newsom signed 39 bills into law intended to address California's housing crisis, three of which entailed major land use reform. One bill eliminated minimum parking requirements for housing near mass transit stations throughout the state. Michael Manville, an urban planning professor at UCLA's Luskin School of Public Affairs, called it "one of the biggest land-use reforms in the country".
== In proteins == In proteins, a structural motif describes the connectivity between secondary structural elements. An individual motif usually consists of only a few elements, e.g., the 'helix-turn-helix' motif which has just three. Note that, while the spatial sequence of elements may be identical in all instances of a motif, they may be encoded in any order within the underlying gene. In addition to secondary structural elements, protein structural motifs often include loops of variable length and unspecified structure. Structural motifs may also appear as tandem repeats.
Sources: en.wikipedia.org
A low-GI food will cause blood glucose levels to increase more slowly and steadily, which leads to lower postprandial (after meal) blood glucose readings. A high-GI food causes a more rapid rise in blood glucose level and is suitable for energy recovery after exercise or for a person experiencing hypoglycemia. The glycemic effect of foods depends on various factors, such as the type of starch (amylose versus amylopectin), physical entrapment of the starch molecules within the food, fat and protein content of the food and organic acids or their salts in the meal. The presence of fat or soluble dietary fiber can slow the gastric emptying rate, thus lowering the GI. In general, coarse, grainy breads with higher amounts of fiber have a lower GI value than white breads. Many modern diets rely on the glycemic index, including the South Beach Diet, Transitions by Market America and NutriSystem Nourish Diet. However, others have pointed out that foods generally considered to be unhealthy can have a low glycemic index, for instance, chocolate cake (GI 38), ice cream (37), or pure fructose (19), whereas foods like potatoes and rice have GIs around 100 but are commonly eaten in some countries with low rates of diabetes.
On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10% rare-earth elements) with mineral acids. Ramsay was looking for argon but, after separating nitrogen and oxygen from the gas, liberated by sulfuric acid, he noticed a bright yellow line that matched the D3 line observed in the spectrum of the Sun. These samples were identified as helium by Lockyer and British physicist William Crookes. It was independently isolated from cleveite in the same year by chemists Per Teodor Cleve and Abraham Langlet in Uppsala, Sweden, who collected enough of the gas to accurately determine its atomic weight. Before he was aware of the identity with Lockyer's helium, Ramsay originally intended to name the new gas krypton, a name he later reused for one of the heavier noble gases. Helium was also isolated by American geochemist William Francis Hillebrand prior to Ramsay's discovery, when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed the lines to nitrogen. His letter of congratulations to Ramsay offers an interesting case of discovery, and near-discovery, in science. In 1907, Ernest Rutherford and Thomas Royds demonstrated that alpha particles are helium nuclei by allowing the particles to penetrate the thin glass wall of an evacuated tube, then creating a discharge in the tube, to study the spectrum of the new gas inside.
=== Class I === Small soluble cytochrome c proteins with a molecular weight of 8-12 kDa and a single heme group belong to class I. It includes the low-spin soluble cytC of mitochondria and bacteria, with the heme-attachment site located towards the N-terminus, and the sixth ligand provided by a methionine residue about 40 residues further on towards the C-terminus. The typical class I fold contains five α-helices. On the basis of sequence similarity, class I cytC were further subdivided into five classes, IA to IE. Class IB includes the eukaryotic mitochondrial cyt c and prokaryotic 'short' cyt c2 exemplified by Rhodopila globiformis cyt c2; class IA includes 'long' cyt c2, such as Rhodospirillum rubrum cyt c2 and Aquaspirillum itersonii cyt c550, which have several extra loops by comparison with class IB cyt c. The linked InterPro entry represents mono-haem cytochrome c proteins (excluding class II and f-type cytochromes), such as cytochromes c, c1, c2, c5, c555, c550-c553, c556, c6 and cbb3. Diheme cytochrome c (InterPro: IPR018588) are proteins with a class I cluster and a unique cluster.
Post-translational modifications (PTMs) are the covalent processes of changing proteins following their synthesis, and release from ribosomes. PTMs are reversible editing events used and carried out in the overall process of post-translational regulation – the control of the levels of active protein; an irreversible event is proteolysis (protein degradation). PTMs enable the protein's function to be diversified and extended beyond the dictates of transcription. As of 2023 there are more than 650 known types of PTM. PTMs are also prokaryotic processes. PTMs may involve enzymes or occur spontaneously. Proteins are created by ribosomes, which translate mRNA into polypeptide chains, which may then change to form the mature protein product, which is then released from the ribosome. PTMs are important components in cell signalling, as for example when prohormones are converted to hormones. Post-translational modifications can occur on the amino acid side chains or at the protein's C- or N- termini. They can expand the chemical set of the 22 amino acids by changing an existing functional group or adding a new one such as phosphate. Phosphorylation is highly effective for controlling the enzyme activity and is the most common change after translation. Many eukaryotic and prokaryotic proteins also have carbohydrate molecules attached to them in a process called glycosylation, which can promote protein folding and improve stability as well as serving regulatory functions.
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.
一般不建议常温长期保存。多数说明指向 -20 °C 冷冻避光。常温运输通常被视为短期可接受，但会加快降解风险。