A practical reference on melanocortin signalling: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-07-20. 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 is described in the literature as an analogue of the ACTH(4–10) fragment, a short N-terminal portion of adrenocorticotropic hormone that retains some neurotropic activity without the full hormonal effects of the parent peptide. The molecule carries a methionine residue at the N-terminus and two proline residues near the C-terminus, features that shape both its interactions with receptor systems and its chemical stability. The free peptide corresponds to the formula C37H51N9O10S and a molecular mass near 813.9 Da.
The compound was developed in the 1980s at the Institute of Molecular Genetics in Moscow, where it emerged from research on short ACTH fragments and their effects on the central nervous system. Russian pharmaceutical listings describe it as a nootropic and neuroprotective agent, most often formulated as nasal drops. It is not a marketed medicine in the United States or the European Union, and no pharmacopoeial monograph covers it. Consequently, most published clinical experience with the substance originates from a small number of research centres, mainly in Russia and neighbouring countries.
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。
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C37H51N9O10S | Free acid form of the heptapeptide; depends on terminal groups |
| Molecular mass | About 813.9 g/mol | Average mass used for mass spectrometry confirmation |
| Appearance | White to off-white solid | Supplied as a lyophilised powder; hygroscopic |
| Solubility class | Freely soluble in aqueous media | Water, saline, and phosphate buffers; limited organic solubility |
| Typical storage temperature | -20 degrees Celsius | Long term and dry; short working periods may use 2 to 8 degrees Celsius |
Semax is a synthetic peptide created in the Soviet Union during the early 1980s by researchers working in Moscow. It was built from the short adrenocorticotropic hormone fragment known as ACTH(4-10), and the chain was then extended with three additional amino acids. The resulting molecule was named semax and entered clinical use in Russia in 1994. It is generally described as a nootropic and neuroprotective agent rather than as a hormone analogue.
The parent fragment ACTH(4-10) carries the sequence Met-Glu-His-Phe-Arg-Trp-Gly. Semax replaces the arginine and tryptophan positions with a proline-glycine-proline tail, giving Met-Glu-His-Phe-Pro-Gly-Pro. That change removes residues associated with adrenal stimulation, so the peptide does not drive cortisol release the way full ACTH does. This distinction shapes how the compound is grouped in the literature, where it sits with neuropeptides and peptide neuromodulators rather than with corticosteroids.
Identity and purity of Semax are established mainly by reversed-phase high-performance liquid chromatography coupled with mass spectrometry. The chromatographic trace gives a purity estimate as a percentage of total peak area, while electrospray or matrix-assisted laser desorption ionization confirms the molecular mass against the calculated value. Amino acid analysis and sequence-specific fragmentation provide further confirmation when a supplier's chain of custody is unclear. Vendors frequently quote a purity figure without stating the detection wavelength or the integration method, which limits how far one number can be compared with another.
Stability depends heavily on physical state. Lyophilized powder held dry, cold and dark retains its content over long periods, whereas dissolved peptide begins to change within days at room temperature. The most cited degradation route is oxidation of the methionine residue, which converts the peptide to a sulfoxide form that elutes differently on chromatography. Hydrolysis of amide bonds and adsorption onto container walls contribute smaller losses. Buffers that exclude oxygen from the headspace slow the oxidation pathway, but no single condition prevents all change indefinitely.
In Bangladesh, a member of parliament is an individual who serves in the unicameral Jatiya Sangsad or House of the Nation. Members of the Jatiya Sangsad are elected at a general election, usually held once every five years unless Parliament is dissolved sooner by the president on the advice of the prime minister. Under the Constitution of Bangladesh, an individual is required to be a citizen of Bangladesh and must have attained the age of 25 years in order to qualify for election to Parliament. The Parliament consists of 300 directly elected members from general seats elected by use of first past the post who represent single-constituencies, while 50 seats are reserved exclusively for women and are allocated on a proportional basis. After an election, the Election Commission allocates reserved seats to parties based on the number of general seats they won. A party then presents a list of candidates, each requiring a presenter and a seconder. If the number of candidates presented and seats allocated is equal, then there is no election and the reserved seats are filled in accordance with the candidate lists prepared by parties. In the event there are more candidates than seat allocations, the 300 MPs elected from general seats vote through use of the single transferable vote system to determine the reserved seats. In reality, there has never been an election for reserved seats as parties have never nominated more candidates than they have been allocated. In order to form a Government, a political party or alliance usually requires a simple majority in Parliament.
Paliperidone, sold under the brand name Invega among others, is an atypical antipsychotic. It is used for the treatment of schizophrenia and schizoaffective disorder. It is marketed by Janssen Pharmaceuticals. Paliperidone was approved by the US Food and Drug Administration (FDA) for the treatment of schizophrenia in December 2006, and in the European Union in June 2007. Paliperidone palmitate is a long-acting injectable formulation of paliperidone palmitoyl ester. It is on the World Health Organization's List of Essential Medicines. Paliperidone is available as a generic medication.
Each neurotransmitter has very specific degradation pathways at regulatory points, which may be targeted by the body's regulatory system or medication. Cocaine blocks a dopamine transporter responsible for the reuptake of dopamine. Without the transporter, dopamine diffuses much more slowly from the synaptic cleft and continues to activate the dopamine receptors on the target cell.
Sources: en.wikipedia.org
The US's UEP guidelines suggest that in egg laying strains of chickens, the length of the upper beak distal from the nostrils that remains following trimming, should be 2 to 3 mm. In the UK, the Farm Animal Welfare Council stated: "The accepted procedure is to remove not more than one third of the upper and lower beaks or not more than one third of the upper beak only" but went on to recommend: "Where beak trimming is carried out, it should, wherever possible, be restricted to beak tipping; that is the blunting of the beak to remove the sharp point which can be the cause of the most severe damage to other birds."
The multiplex or Fellgett's advantage (named after Peter Fellgett). This arises from the fact that information from all wavelengths is collected simultaneously. It results in a higher signal-to-noise ratio for a given scan-time for observations limited by a fixed detector noise contribution (typically in the thermal infrared spectral region where a photodetector is limited by generation-recombination noise). For a spectrum with m resolution elements, this increase is equal to the square root of m. Alternatively, it allows a shorter scan-time for a given resolution. In practice multiple scans are often averaged, increasing the signal-to-noise ratio by the square root of the number of scans. The throughput or Jacquinot's advantage (named after Pierre Jacquinot). This results from the fact that in a dispersive instrument, the monochromator has entrance and exit slits which restrict the amount of light that passes through it. The interferometer throughput is determined only by the diameter of the collimated beam coming from the source. Although no slits are needed, FTIR spectrometers do require an aperture to restrict the convergence of the collimated beam in the interferometer. This is because convergent rays are modulated at different frequencies as the path difference is varied. Such an aperture is called a Jacquinot stop. For a given resolution and wavelength this circular aperture allows more light through than a slit, resulting in a higher signal-to-noise ratio. The wavelength accuracy or Connes's advantage (named after Janine Connes).
== Production == As 225Ac does not occur in any appreciable quantities in nature, it must be synthesized in specialized nuclear reactors or accelerators. The majority of 225Ac results from the alpha decay of 229Th, but this supply is limited because the decay of 229Th (half-life 7920 years) is slow. It is also possible to breed 225Ac from radium-226 in the 226Ra(p,2n) reaction. This was first done in 2005, though the production and handling of 226Ra are difficult because of the respective cost of extraction and hazards of decay products such as radon-222. Alternatively, 225Ac can be produced in spallation reactions on a 232Th target irradiated with high-energy proton beams. Current techniques enable the production of millicurie quantities of 225Ac; however, it must then be separated from other reaction products. This is done by allowing some of the shorter-lived nuclides to decay; actinium isotopes are then chemically purified in hot cells and 225Ac is concentrated. Special care must be taken to avoid contamination with the longer-lived beta-emitting actinium-227. For decades, most 225Ac was produced in one facility—the Oak Ridge National Laboratory in Tennessee—further reducing this isotope's availability even with smaller contributions from other laboratories. Additional 225Ac is now produced from 232Th at Los Alamos National Laboratory and Brookhaven National Laboratory. The TRIUMF facility and Canadian Nuclear Laboratories have formed a strategic partnership around the commercial production of actinium-225.
Sources: en.wikipedia.org
It is described as a synthetic analogue of the ACTH(4–10) fragment, a short segment of adrenocorticotropic hormone. Its sequence differs from that fragment and includes two proline residues, which influence stability and behaviour in solution.
It appears in Russian pharmaceutical listings as a nasal formulation, but it is not an authorised medicine in the United States or the European Union. Outside those markets it is normally encountered as a research chemical rather than a prescription product.
Laboratory and animal work points to melanocortin signalling and changes in neurotrophic factor levels, especially brain-derived neurotrophic factor. The exact receptor targets and the degree to which these findings transfer to humans are still unresolved.
电喷雾或基质辅助激光解吸电离质谱是常用手段，测得的质子化离子质荷比可换算为分子量。结果与理论值落在合理误差内，才支持结构一致的判断。