neurotrophic signaling raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-04-20. Anything still debated is marked as such rather than presented as settled.
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.
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.
Published research covers ischemic stroke, traumatic brain injury, cognitive impairment, optic nerve conditions and attention-related measures. Much of the human evidence comes from small trials conducted in one country, which limits how far the results generalize. Animal models supply the larger share of the data, and effects seen in rodents do not transfer automatically to people. Reviews have noted that methodological reporting is often incomplete, making it difficult to pool results or compare treatment schedules across studies.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C37H51N9O10S | Contains one methionine sulfur atom |
| Molecular mass | Approximately 814 Da | Consistent with a seven-residue peptide |
| Appearance | White to off-white powder | Typical lyophilized form |
| Solubility | Freely soluble in water | Also soluble in dimethyl sulfoxide |
| Typical storage | -20 °C, desiccated | Limits methionine oxidation |
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。
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。
=== Extracellular matrix === Extracellular matrix (or "ECM") is the external structural framework that cells attach to in multicellular organisms. The dermis lies below the epidermis, and these two layers are collectively known as the skin. Dermal skin is primarily a combination of fibroblasts growing in this matrix. The specific species of ECM of connective tissues often differ chemically, but collagen generally forms the bulk of the structure. Through the interaction of a cell with its extracellular matrix (transmitted through the anchoring molecules classed as integrins) there forms a continuous association between the cell interior, cell membrane and its extracellular matrix components that helps drive various cellular events in a regulated fashion. Wound healing is a localized event involving the reaction of cells to the damage sustained. The cells break down damaged ECM and replace it, generally increasing in number to react to the harm. The process is activated, though perhaps not exclusively, by cells responding to fragments of damaged ECM, and the repairs are made by reassembling the matrix by cells growing on and through it. Because of this, extracellular matrix is often considered as a 'conductor of the wound healing symphony'. In the Inflammatory phase, neutrophils and macrophages recruit and activate fibroblasts which in subsequent granulation phase migrate into the wound, laying down new collagen of the subtypes I and III. In the initial events of wound healing, collagen III predominates in the granulation tissue.
==== Pharmacokinetics ==== Nabiximol is rapidly absorbed from the buccal mucosa (membranes inside the mouth). It is then widely distributed in different body tissues, especially fatty tissues due to its high lipophilicity. Thus, it may be stored in the fatty tissues for as long as four weeks, which then slowly release back into the blood stream. THC and CBD, the two components of nabiximol is mainly metabolised in the liver via CYP450 enzymes (2C9, 2C19, 2D6 and 3A4) to 11-hydroxy-tetrahydrocannabinol and 7-hydroxy-cannabidiol respectively. Excretion is primarily in faeces.
=== Response to injury === Since several immune mechanisms involved in the response to injury are widely shared among modern eukaryotes, it has been suggested that they were present in the LECA. These mechanisms include receptors, calcium signalling, reactive oxygen species, adenosine triphosphate release, kinase cascades, and oxylipin signalling. Single-celled eukaryotes, such as choanoflagellates, substantially share the pathways found in plants and animals for detecting damage and pathogens. Extracellular adenosine triphosphate is a signal that promotes healing of wounds to the epithelium in animals. The signal is detected by a P2X receptor. The cell biologist Thibaut Brunet and the molecular biologist Detlev Arendt propose that the LECA possessed a calcium-based wound healing response. They argue that the mechanism's purpose was to detect and heal a potentially fatal opening in the cell membrane. They propose that it worked by detecting an inflow of calcium ions, which provoked a contraction in muscle-like actomyosin proteins. This in turn caused vesicles to fuse with the cell membrane (exocytosis), healing the opening and preventing the cell from splitting open.
A 2014 study of 18 Latin American countries in the 20th-century study found the legislative powers of the presidency does not influence coup frequency. A 2019 study found that when a country's politics is polarized and electoral competition is low, civilian-recruited coups become more likely. A 2023 study found that civilian elites are more likely to be associated with instigating military coups while civilians embedded in social networks are more likely to be associated with consolidating military coups.
Sources: en.wikipedia.org
CH3COOH + H2O ⇌ CH3COO− + H3O+ CH3COOH + NH3 ⇌ CH3COO− + NH+4 Both theories easily describe the first reaction: CH3COOH acts as an Arrhenius acid because it acts as a source of H3O+ when dissolved in water, and it acts as a Brønsted acid by donating a proton to water. In the second example CH3COOH undergoes the same transformation, in this case donating a proton to ammonia (NH3), but does not relate to the Arrhenius definition of an acid because the reaction does not produce hydronium. Nevertheless, CH3COOH is both an Arrhenius and a Brønsted–Lowry acid. Brønsted–Lowry theory can be used to describe reactions of molecular compounds in nonaqueous solution or the gas phase. Hydrogen chloride (HCl) and ammonia combine under several different conditions to form ammonium chloride, NH4Cl. In aqueous solution HCl behaves as hydrochloric acid and exists as hydronium and chloride ions. The following reactions illustrate the limitations of Arrhenius's definition:
==== Production of "Instant" 99mTc ==== The feasibility of 99mTc production with the 22-MeV-proton bombardment of a 100Mo target in medical cyclotrons was demonstrated in 1971. The recent shortages of 99mTc reignited the interest in the production of "instant" 99mTc by proton bombardment of isotopically enriched 100Mo targets (>99.5%) following the reaction 100Mo(p,2n)99mTc. Canada is commissioning such cyclotrons, designed by Advanced Cyclotron Systems, for 99mTc production at the University of Alberta and the Université de Sherbrooke, and is planning others at the University of British Columbia, TRIUMF, University of Saskatchewan and Lakehead University. A particular drawback of cyclotron production via (p,2n) on 100Mo is the significant co-production of 99gTc. The preferential in-growth of this nuclide occurs due to the larger reaction cross-section pathway leading to the ground state, which is almost five times higher at the cross-section maximum in comparison with the metastable one at the same energy. Depending on the time required to process the target material and recovery of 99mTc, the amount of 99mTc relative to 99gTc will continue to decrease, in turn reducing the specific activity of 99mTc available. It has been reported that ingrowth of 99gTc as well as the presence of other Tc isotopes can negatively affect subsequent labelling and/or imaging; however, the use of high purity 100Mo targets, specified proton beam energies, and appropriate time of use have shown to be sufficient for yielding 99mTc from a cyclotron comparable to that from a commercial generator.
Unlike many medicines, insulin cannot be taken orally at the present time. Like nearly all other proteins introduced into the gastrointestinal tract, it is reduced to fragments (single amino acid components), whereupon all activity is lost. There has been some research into ways to protect insulin from the digestive tract, so that it can be administered in a pill. So far this is entirely experimental.
Thermoplastic polymers Thermoset polymers Dendrimers Vitrimers / Covalent adaptable networks (CANs) Covalent organic frameworks (COFs) When considering organometallic materials within the scope, this may also include metal organic frameworks (MOFs). Additionally, when also considering other non-covalent bonding, such as hydrogen bonds or pi-stacking many different types of supramolecular networks are also included.
On 11 December 1944, the unit was again renamed, becoming 309 Dywizjon Myśliwski "Ziemi Czerwieńskiej" or 309 "Land of Czerwien" Polish Fighter Squadron. In 1945, 303 "Kościuszko" Sqn received 20 Mustangs Mk IV/Mk IVA replacements. Postwar, between 6 December 1946 and 6 January 1947, all five Polish squadrons equipped with Mustangs were disbanded. Poland returned about 80 Mustang Mk IIIs and 20 Mustangs Mk IV/IVAs to the RAF, which transferred them to the US government. Somalia The Somali Air Force operated eight P-51Ds in post-World War II service. South Africa
Sources: en.wikipedia.org
=== Receptor ectodomain shedding === When the extracellular domain of GHR is proteolytically cleaved (see: proteolytic cleavage) from the rest of the receptor protein, the extracellular domain is released as the water-soluble, carrier protein GHBP. As the extracellular domain alone, the polypeptide consists of 246 amino acids and is roughly 60 kDA in size. This cleaving process is called “receptor ectodomain shedding. In humans and rabbits, tumor-necrosis factor alpha converting enzyme (T.A.C.E.) is postulated to play a significant role in the post-translational processing activity that sheds GHBP from GHR. Studies show that this activity primarily occurs in the liver. When growth hormone is bound to two dimerized GH receptors, the shedding activity is inhibited. This occurs because when the ligand binds to the receptors, a conformational change occurs in them that potentially blocks the proteolytic activity of T.A.C.E.
acts as a self-standard. Ultramicroporous, microporous, and mesoporous conditions may be analyzed using this technique. Typical standard deviations for full isotherm fits including porous samples are less than 2%. Notice that in this description of physical adsorption, the entropy of adsorption is consistent with the Dubinin thermodynamic criterion, that is the entropy of adsorption from the liquid state to the adsorbed state is approximately zero.
Chymopapain (EC 3.4.22.6, chymopapain A, chymopapain B, chymopapain S, brand name Chymodiactin) is a proteolytic enzyme isolated from the latex of papaya (Carica papaya). It is a cysteine protease which belongs to the papain-like protease (PLCP) group. Because of its proteolytic activity, it is the main molecule in the process of chemonucleolysis, used in some procedures like the treatment of herniated lower lumbar discs in the spine by a nonsurgical method.
== Surface energy determination == The main application of IGC is to measure the surface energy of solids (fibers, particulates, and films). Surface energy is defined as the amount of energy required to create a unit area of a solid surface; analogous to surface tension of a liquid. Also, the surface energy can be defined as the excess energy at the surface of a material compared to the bulk. The surface energy (γ) is directly related to the thermodynamic work of adhesion (Wadh) between two materials as given by the following equation:
The role of caregivers for youth with mental health needs is valuable, and caregivers benefit most when they have sufficient psychoeducation and peer support. Depression is one of the leading causes of illness and disability among adolescents. Suicide is the fourth leading cause of death in 15-19-year-olds. Exposure to childhood trauma can cause mental health disorders and poor academic achievement. Ignoring mental health conditions in adolescents can impact adulthood. 50% of preschool children show a natural reduction in behavioral problems. The remaining experience long-term consequences. It impairs physical and mental health and limits opportunities to live fulfilling lives. A result of depression during adolescence and adulthood may be substance abuse. The average age of onset is between 11 and 14 years for depressive disorders. Only approximately 25% of children with behavioral problems refer to medical services. The majority of children go untreated. A global study of more than 275,000 adolescents aged 12–17 years across 82 countries found that 14% had experienced suicidal thoughts and 9% had anxiety over a 12-month period; adolescents with fewer peer and parental supports and greater exposure to peer conflict, victimisation, and loneliness were at higher risk, and 36 of the 82 countries studied had no specific national mental health policy.
Sources: en.wikipedia.org
It is registered as a pharmaceutical product in Russia, where it is typically supplied as a nasal solution. In most other countries it is not an approved drug and is traded as a research chemical instead. Approval status depends entirely on the jurisdiction involved.
Most published work uses intranasal administration, matching the route of the registered Russian formulation. Some animal experiments use intravenous or intraperitoneal injection. The route matters because the intact peptide is cleared rapidly from blood, so exposure differs between methods.
A purity value describes the share of the powder accounted for by the target peptide, usually by high-performance liquid chromatography. It does not confirm that the sequence is correct, which requires mass spectrometry or amino acid analysis. Purity and identity are separate checks.
The main proposal is modulation of neurotrophic factors such as brain-derived neurotrophic factor, supported largely by animal experiments. Receptor-level targets have not been firmly established. Most reviews describe the mechanism as only partially characterized.