Neurotrophic signalling is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2025-10-15. Numbers and descriptions here follow the published literature rather than marketing material.
Routine characterization relies on reversed-phase high-performance liquid chromatography to establish purity and on mass spectrometry to confirm molecular identity. Electrospray ionization and matrix-assisted laser desorption ionization are both used for mass verification. Amino acid analysis and peptide mapping can detect sequence errors. Common impurities include truncated sequences, methionine sulfoxide formed by oxidation, and deamidated products. Chromatograms are usually recorded near 214 nm, where the peptide backbone absorbs, and purity is reported as the percentage area of the principal peak.
Verification of a supplied batch generally combines a certificate of analysis with independent testing, because certificates are self-reported documents. A typical package includes a chromatographic trace, a mass spectrum, and a stated water or counter-ion content. Batch-to-batch consistency matters more than a single purity figure when results are compared across experiments. No single mandatory standard governs research-grade peptide release, so laboratories are expected to define their own acceptance criteria. Residual trifluoroacetate from purification is a frequently overlooked counter-ion.
Lyophilized material is chemically stable for extended periods when kept dry, cold, and protected from light. The powder is hygroscopic, so vials should be warmed to room temperature before opening to reduce condensation on the contents. Once dissolved, the peptide is far less stable because peptide bonds are susceptible to hydrolysis and the methionine residue can oxidize. Solutions are typically aliquoted and held at 2-8 °C for short intervals or frozen for longer ones, and repeated freeze-thaw cycles should be avoided.
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.
| Property | Value | Notes |
|---|---|---|
| Typical purity | 95% or higher | By reversed-phase HPLC area |
| Identity method | Electrospray mass spectrometry | Confirms molecular mass |
| Purity method | Reversed-phase HPLC | Detection near 214 nm |
| Primary degradation | Methionine oxidation | Sulfoxide product, +16 Da |
| Solution storage | 2-8 °C, short term | Aliquot to avoid freeze-thaw |
Circulation time for the peptide is short because peptidases cleave it readily. The Pro-Gly-Pro tail is thought to slow breakdown compared with the bare ACTH fragment, but the gain appears modest. Absorption after intranasal dosing is limited, and only a fraction of a dose is expected to reach the central nervous system. Laboratory concentrations therefore sit well above levels achieved systemically, a gap that complicates translation from bench findings to clinical claims.
The mechanisms attributed to semax are inferred from animal and cell studies rather than traced to one confirmed target. The most frequently cited pathway involves increased expression of brain-derived neurotrophic factor and nerve growth factor in hippocampal and cortical tissue. Some work points to engagement of melanocortin receptors, particularly MC4, which the parent ACTH fragment can activate. Effects on dopaminergic and serotonergic signalling have also been reported. No single account explains all observed results, and the relative weight of each pathway remains unsettled.
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.
Scientific literature on semax is unevenly distributed. A substantial share of published work originates from a small number of laboratories in Russia, while independent replication elsewhere is limited. Human data consist mostly of small trials with short follow-up, and several reported outcomes rely on subjective rating scales. Questions about how much intact peptide reaches the central nervous system after nasal administration, and how long it persists there, are still unresolved. The compound is best described as an active research subject rather than a settled pharmacological agent.
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.
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。
Noodles (Chinese: 面/麵 miàn) were invented in China over 4,000 years ago and have since spread across the world. Chinese noodles come dry or fresh in a variety of sizes, shapes and textures and are often served in soups or fried as toppings. Some varieties, such as Shou Mian (寿面, literally noodles of longevity), is an avatar of long life and good health according to Chinese traditions. Noodles can be served hot or cold with different toppings, with broth, and occasionally dry (as is the case with mi-fen). Noodles are commonly made with rice flour or wheat flour, but other flours such as soybean are also used in minor groups. Some noodles names describe their methods of creation, such as the hand-pulled noodle.
=== Asymmetric flow === Asymmetric flow FFF (AF4), on the other hand, has only one semi-permeable membrane on the bottom wall of the channel. The cross flow is, therefore, created by the carrier liquid exiting the bottom of the channel. This offers an extremely gentle separation and an “ultra-broad” separation range. The majority of FFF instruments in use are AF4 systems. Main applications are in pharmaceutical research and development for proteins, virus and virus-like particles, and liposomes. AF4 has also been combined with immunoaffinity monolith chromatography for the analysis of plasma-derived extracellular vesicles. CD61-positive platelet-derived vesicles have been isolated using an anti-CD61 monolithic disk and size-fractionated by AF4 coupled with multi-angle and dynamic light-scattering detection. An automated online immunoaffinity chromatography–AF4 system was later used to isolate and fractionate both CD61-positive platelet-derived vesicles and CD9-positive vesicles into size-based subpopulations. The resulting EV fractions were further characterized by Raman spectroscopy and comprehensive two-dimensional gas chromatography. Related AF4 fractionated EV subpopulations were also used in quartz crystal microbalance studies of antibody and ICAM-1 binding. AF4 can be applied in aqueous and organic solvents, therefore also organic polymers can be separated by this technique. High temperature asymmetric flow field-flow fractionation is available for the separation of high and ultra-high molar mass polymers soluble at temperatures above 150 C.
The hydrocarbon-generating potential and thermal maturity of petroleum source rocks are commonly evaluated using Rock-Eval pyrolysis and vitrinite reflectance measurements, which provide quantitative indicators of organic matter type, maturation level, and the likelihood of oil or gas generation. Catagenesis was pyrolytic despite the fact that it happened at relatively low temperatures (when compared to commercial pyrolysis plants) of 60 to several hundred °C. Pyrolysis was possible because of the long reaction times involved. Heat for catagenesis came from the decomposition of radioactive materials of the crust, especially 40K, 232Th, 235U and 238U. The heat varied with geothermal gradient and was typically 10–30 °C per km of depth from the Earth's surface. Unusual magma intrusions, however, could have created greater localized heating.
== External links == UniProt: Bisphosphoglycerate mutase - Homo sapiens (Human) UniProt-Information about bisphosphoglycerate mutase A live model of the effect of changing 2,3-bisphosphoglycerate on the oxyhaemoglobin saturation curve
FO is a water insoluble protein with eight subunits and a transmembrane ring. The ring has a tetrameric shape with a helix-loop-helix protein that goes through conformational changes when protonated and deprotonated, pushing neighboring subunits to rotate, causing the spinning of FO which then also affects conformation of F1, resulting in switching of states of alpha and beta subunits. The FO region of ATP synthase is a proton pore that is embedded in the mitochondrial membrane. It consists of three main subunits, a, b, and c. Six c subunits make up the rotor ring, and subunit b makes up a stalk connecting to F1 OSCP that prevents the αβ hexamer from rotating. Subunit a connects b to the c ring. Humans have six additional subunits, d, e, f, g, F6, and 8 (or A6L). This part of the enzyme is located in the mitochondrial inner membrane and couples proton translocation to the rotation that causes ATP synthesis in the F1 region. In eukaryotes, mitochondrial FO forms membrane-bending dimers. These dimers self-arrange into long rows at the end of the cristae, possibly the first step of cristae formation. An atomic model for the dimeric yeast FO region was determined by cryo-EM at an overall resolution of 3.6 Å.
Sources: en.wikipedia.org
=== Preparation and size === Particularly for older samples, it may be useful to enrich the amount of 14C in the sample before testing. This can be done with a thermal diffusion column. The process takes about a month and requires a sample about ten times as large as would be needed otherwise, but it allows more precise measurement of the 14C/12C ratio in old material and extends the maximum age that can be reliably reported. Once contamination has been removed, samples must be converted to a form suitable for the measuring technology to be used. Where gas is required, CO2 is widely used. For samples to be used in liquid scintillation counters, the carbon must be in liquid form; the sample is typically converted to benzene. For accelerator mass spectrometry, solid graphite targets are the most common, although gaseous CO2 can also be used. The quantity of material needed for testing depends on the sample type and the technology being used. There are two types of testing technology: detectors that record radioactivity, known as beta counters, and accelerator mass spectrometers. For beta counters, a sample weighing at least 10 grams (0.35 ounces) is typically required. Accelerator mass spectrometry is much more sensitive, and samples containing as little as 0.5 milligrams of carbon can be used.
=== Outpatient treatment === Outpatient treatment involves periodic visits to a psychiatrist for consultation in his or her office, or at a community-based outpatient clinic. During initial appointments, a psychiatrist generally conducts a psychiatric assessment or evaluation of the patient. Follow-up appointments then focus on making medication adjustments, reviewing potential medication interactions, considering the impact of other medical disorders on the patient's mental and emotional functioning, and counseling patients regarding changes they might make to facilitate healing and remission of symptoms. The frequency with which a psychiatrist sees people in treatment varies widely, from once a week to twice a year, depending on the type, severity and stability of each person's condition, and depending on what the clinician and patient decide would be best. Increasingly, psychiatrists are limiting their practices to psychopharmacology (prescribing medications), as opposed to previous practice in which a psychiatrist would provide traditional 50-minute psychotherapy sessions, of which psychopharmacology would be a part, but most of the consultation sessions consisted of "talk therapy". This shift began in the early 1980s and accelerated in the 1990s and 2000s. A major reason for this change was the advent of managed care insurance plans, which began to limit reimbursement for psychotherapy sessions provided by psychiatrists.
In 1974, under the Local Government Act 1972, the administrative county and county borough were abolished and their former area was combined with Westmorland and parts of Lancashire and the West Riding of Yorkshire to form the new county of Cumbria. The area from Cumberland went on to form the districts of Carlisle, Allerdale, Copeland and part of Eden.
== Further reading == Schüring, J.; Schulz, H. D.; Fischer, W. R.; Böttcher, J.; Duijnisveld, W. H., eds. (1999). Redox: Fundamentals, Processes and Applications. Heidelberg: Springer-Verlag. p. 246. hdl:10013/epic.31694.d001. ISBN 978-3-540-66528-1. Tratnyek, Paul G.; Grundl, Timothy J.; Haderlein, Stefan B., eds. (2011). Aquatic Redox Chemistry. ACS Symposium Series. Vol. 1071. doi:10.1021/bk-2011-1071. ISBN 978-0-8412-2652-4.
=== Optimal solution === The optimal "threading" of a protein sequence onto a known structure and the production of an optimal multiple sequence alignment have been shown to be NP-complete. However, this does not imply that the structural alignment problem is NP-complete. Strictly speaking, an optimal solution to the protein structure alignment problem is only known for certain protein structure similarity measures, such as the measures used in protein structure prediction experiments, GDT_TS and MaxSub. These measures can be rigorously optimized using an algorithm capable of maximizing the number of atoms in two proteins that can be superimposed under a predefined distance cutoff. Unfortunately, the algorithm for optimal solution is not practical, since its running time depends not only on the lengths but also on the intrinsic geometry of input proteins.
Sources: en.wikipedia.org
=== Security === A post–September 11 development, explosive detection systems have become a part of all US airports. These systems run on a host of technologies, many of them based on GC–MS. There are only three manufacturers certified by the FAA to provide these systems, one of which is Thermo Detection (formerly Thermedics), which produces the EGIS, a GC–MS-based line of explosives detectors. The other two manufacturers are Barringer Technologies, now owned by Smith's Detection Systems, and Ion Track Instruments, part of General Electric Infrastructure Security Systems.
=== Lithium-ion batteries === Li2TiO3 is used in the cathode of some lithium-ion batteries, along with an aqueous binder and a conducting agent. Li2TiO3 is used because it is capable of stabilizing the high capacity cathode conducting agents; LiMO2 (M=Fe, Mn, Cr, Ni). Li2TiO3 and the conduction agents (LiMO2) are layered in order to create the cathode material. These layers allow for the occurrence of lithium diffusion.
==== Enzyme-linked immunosorbent assay ==== The enzyme-linked immunosorbent assay (ELISA) technique used for the analysis of YTXs is a recently developed method by Briggs et al. This competitive, indirect immunoassay uses polyclonal antibodies against YTX to determine its concentration in the sample. The assay is commercially available, and is a rapid technique for the analysis of YTXs in shellfish, algal cells, and culture samples. ELISA has several advantages: it is very sensitive, has a limit of quantification of 75 μg/kg, is relatively cheap, and is easy to carry out. The major disadvantage to this method is it cannot differentiate between the different YTX analogues and takes a long time to generate results.
=== Tumors in CUX1 transgenic mice === CUX1 transgenic mice develop tumors in multiple organs and tissues after a long latency period. Transgenic mice expressing either p75, p110 or p200 CUX1 in mammary epithelial cells develop mammary tumours with a low penetrance (~20%) and with a long latency period. Metastasis to the lung was observed in three cases of mammary tumors expressing p75 CUX1. The mechanisms of action differ widely between p110 CUX1 and p200 CUX1. Transgenic mice expressing p110 CUX1 in mammary epithelial cells develop mammary tumors that exhibit a sub-tetraploid chromosome number, suggesting passage through tetraploidy resulting from cytokinesis failure. Cells do not usually survive as tetraploid with multiple centrosomes. Overexpression of p110 CUX1 was shown to activate a transcriptional program that reinforces the spindle assembly checkpoint and delays mitosis until extranumerary centrosomes have clustered to two poles, thereby enabling bipolar mitosis and survival of tetraploid cells. Yet, passage through a multipolar intermediate enriches for merotelic chromosome attachments, leading to chromosome mis-segregation and the rapid generation of aneuploid populations from which tumorigenic cells emerge. Tumors that develop in p200 CUX1 transgenic mice reveal a different mode of action, as 44% of these tumors harboured a spontaneous mutation activating the Kras gene. The cooperation between RAS and p200 CUX1 was confirmed by lentiviral infections in the lung. RAS oncogenes do not transform primary cells, but instead cause cellular senescence.
Sources: en.wikipedia.org
Dry powder is normally held at -20 °C or lower, away from light and moisture. Sealed vials can also be kept at 2-8 °C for shorter intervals. Warming to room temperature before opening prevents condensation.
In solution, hydrolysis of peptide bonds and oxidation of the methionine residue are the principal concerns. Oxidation converts methionine to its sulfoxide form, shifting the mass by sixteen daltons. Both processes are slowed by cold storage and by avoiding alkaline conditions.
A certificate documents what the supplier measured on a specific lot, not how a laboratory will use the material. Independent verification of identity and purity is common practice. Acceptance criteria should be defined before a batch is ordered.
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.