The short version of melanocortin signalling fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
The peptide is prone to several degradation pathways. Oxidation of the methionine residue produces a sulfoxide that elutes close to the parent peak in many chromatographic systems. Hydrolysis of peptide bonds and deamidation of susceptible residues in related sequences also reduce purity over time. Lyophilised material kept dry at minus twenty degrees Celsius and shielded from light is the most stable form commonly described in laboratory practice.
Material sold for laboratory use varies widely in stated purity and documentation. A certificate of analysis should list the analytical method, the column and detector used, and the observed purity value. Independent verification by an outside laboratory is the practical way to confirm identity when documentation is absent or internally inconsistent. Regulatory status differs by country, and a product legal in one jurisdiction may be unapproved or controlled in another.
Identity and purity of semax are established with reversed-phase high-performance liquid chromatography coupled to ultraviolet detection, usually at 214 nanometres. Mass spectrometry, most often electrospray ionisation in positive mode, confirms the molecular mass and reveals truncated sequences. Amino acid analysis and peptide mapping after enzymatic digestion provide additional structural confirmation. Laboratories typically report purity as the percentage area of the main peak, a figure that does not capture isomeric or oxidised variants unless the method resolves them.
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.
Pharmacological accounts link semax to melanocortin signalling and to modulation of neurotrophic factor expression, particularly brain-derived neurotrophic factor and nerve growth factor. Much of this evidence comes from rodent studies using intranasal delivery, a route chosen because it allows peptides to reach the central nervous system with limited systemic exposure. Whether the same mechanisms operate in humans at comparable magnitude remains an open question. The precise receptor or receptors responsible for the reported behavioural and neuroprotective effects have not been conclusively identified.
Clinical reports describe use in ischaemic stroke, transient ischaemic attack, optic nerve conditions, and cognitive complaints, but most of these studies are small and were conducted in a single region. Systematic reviews have generally described the evidence base as limited in size and variable in methodological quality. Randomised controlled data suitable for international regulatory assessment are scarce. As a result, major treatment guidelines outside Russia do not include the peptide, and interest in it remains largely research-driven rather than routine clinical.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised solid |
| Solubility class | Freely soluble in water | Also dissolves in aqueous buffers |
| Typical storage temperature | -20 °C | Dry, desiccated, protected from light |
| Typical analytical method | RP-HPLC with UV detection | Often paired with LC-MS |
| Water content | Reported as Karl Fischer value | Freeze-dried material is hygroscopic |
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.
Practical handling follows from those properties. Bulk material is best divided into single-use portions soon after receipt, because each thaw exposes the whole container to moisture and temperature cycling. Vials should be allowed to reach room temperature before opening to prevent condensation on the powder. Low-binding plasticware reduces loss of dilute solutions, and sterile filtration is used when a preparation must remain free of microbial growth. Records of batch number, reconstitution date and storage history are what allow a later analytical result to be interpreted meaningfully.
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.
研究兴趣主要集中在神经营养因子相关的路径上，包括脑源性神经营养因子与神经生长因子的表达变化。部分实验报告称在特定条件下观察到这些因子的水平上升，但具体信号通路和剂量依赖关系仍未完全厘清。多数公开数据来自细胞模型和动物实验，人体对照研究数量有限。因此，该化合物的作用机制在文献中属于活跃讨论，而非已经确立的定论。
Semax 是一种人工合成的七肽，氨基酸序列为 Met-Glu-His-Phe-Pro-Gly-Pro，单字母缩写记作 MEHFPGP。它被归类为促肾上腺皮质激素片段 ACTH(4-10) 的结构类似物，但并不天然存在于生物体内。母体片段 ACTH(4-10) 的序列为 Met-Glu-His-Phe-Arg-Trp-Gly，Semax 替换了中间两个残基，并在羧基端延长了 Pro-Gly-Pro 三肽。这种延长被普遍认为能提升分子对肽酶的耐受性。
该化合物于二十世纪八十年代在俄罗斯被开发，相关工作由俄罗斯科学院分子遗传学研究所的研究团队主导。开发目标并非复制 ACTH 的完整激素活性，而是寻找保留其神经作用方向、同时去除促肾上腺皮质激素释放效应的短肽片段。研究记录显示，这一方向促成了多个相关短肽的合成与筛选，而 Semax 是其中被研究最广泛的一个。当地文献常以 Семакс 这一名称指代它。
Identity and purity are established with standard peptide methods. Reversed-phase HPLC with ultraviolet detection near 214 nm resolves the parent peak from deletion and truncation byproducts, and reports typically quote a main-peak percentage. Mass spectrometry by electrospray or MALDI-TOF confirms the expected molecular mass, while amino acid analysis or peptide mapping can verify composition when the sequence itself is in question. A certificate of analysis that pairs a chromatogram with a mass spectrum is more informative than a purity figure alone. Counter-ion content and residual solvents are separate specifications and are frequently omitted.
Semax is normally supplied as a lyophilized powder, and that form is the most stable. Suppliers commonly recommend storage at -20 °C in a desiccated container protected from light, with short-term handling at room temperature limited to weighing and transfer. Powder that has absorbed moisture degrades faster, so vials should be warmed to ambient temperature before opening to prevent condensation on the contents. Hygroscopic behavior is typical of short hydrophilic peptides, and humidity control matters more than temperature alone for long-term retention.
=== Leaders of the Liberal Party === H. H. Asquith, 1st Earl of Oxford and Asquith, 1925 (1916–1926) Donald Maclean, Acting Leader (1919–1920) David Lloyd George (1926–1931) Sir Herbert Samuel (1931–1935) Sir Archibald Sinclair (1935–1945) Clement Davies (1945–1956) Jo Grimond (1956–1967) Jeremy Thorpe (1967–1976) Jo Grimond, Interim Leader (1976) David Steel (1976–1988)
The hospital specialized in the treatment of heart, lung and eye problems. UCC also provided a $2.2 million grant to Arizona State University to establish a vocational-technical centre in Bhopal, which was opened, but was later closed by the state government. They also donated $5 million to the Indian Red Cross after the disaster. They also developed a Responsible Care system with other members of the chemical industry as a response to the Bhopal crisis, which was designed to help prevent such an event in the future.
The most complex RPR synthesized by that point was called 24-3, which was newly capable of polymerizing the sequences of a substantial variety of nucleotide sequences and navigating through complex secondary structures of RNA substrates inaccessible to previous ribozymes. In fact, this experiment was the first to use a ribozyme to synthesize a tRNA molecule. Starting with the 24-3 ribozyme, Tjhung et al. applied another fourteen rounds of selection to obtain an RNA polymerase ribozyme by in vitro evolution termed '38-6' that has an unprecedented level of activity in copying complex RNA molecules. However, this ribozyme is unable to copy itself and its RNA products have a high mutation rate. In a subsequent study, the researchers began with the 38-6 ribozyme and applied another 14 rounds of selection to generate the '52-2' ribozyme, which compared to 38-6, was again many times more active and could begin generating detectable and functional levels of the class I ligase, although it was still limited in its fidelity and functionality in comparison to copying of the same template by proteins such as the T7 RNA polymerase. An RPR called t5(+1) adds triplet nucleotides at a time instead of just one nucleotide at a time. This heterodimeric RPR can navigate secondary structures inaccessible to 24-3, including hairpins. In the initial pool of RNA variants derived only from a previously synthesized RPR known as the Z RPR, two sequences separately emerged and evolved to be mutualistically dependent on each other.
Sources: en.wikipedia.org
== Young children == Single episodes of hypoglycemia may occur due to gastroenteritis or fasting, but recurrent episodes nearly always indicate either an inborn error of metabolism, congenital hypopituitarism, or congenital hyperinsulinism. A list of common causes:
=== Use of Oriented Peptide Libraries to determine phosphopeptide binding specificity and protein kinase substrate specificity === In 1994, the Cantley lab published a novel strategy to determine the sequence specificity of phosphopeptide binding domains (initially SH2 domains). Subsequently, the oriented peptide library approach was extended to identify the substrate specificity of protein kinases toward synthetic peptides. This approach was then extended to characterize the specificity of Ser/Thr kinases and phospho-Ser/Thr binding domains. This approach was used to characterize the substrate specificity of a large number of protein kinases. The kinase specificity matrices generated from these experiments served as the basis for creating the website Scansite, allowing the de novo identification of candidate phosphorylation sites in an arbitrary protein. In later research, the oriented peptide library approach has also been used to characterize protease cleavage specificity. Modification of the original oriented peptide approach has allowed for large scale, kinome-wide determination of protein kinase specificity.
== Further reading == Collins R (2017). "Lowering Restrictions on Performance Enhancing Drugs in Elite Sports". Inquiries Journal. 9 (3). Retrieved 7 July 2017. Franke WW, Berendonk B (July 1997). "Hormonal doping and androgenization of athletes: a secret program of the German Democratic Republic government". Clinical Chemistry. 43 (7): 1262–79. doi:10.1093/clinchem/43.7.1262. PMID 9216474. Mottram, David (2005); Drugs in Sport, Routledge. ISBN 978-0-415-37564-1. Murray, Thomas H. (2008); "Sports Enhancement", in From Birth to Death and Bench to Clinic: The Hastings Center Bioethics Briefing Book for Journalists, Policymakers, and Campaigns. Pope J, Harrison G, Wood RI, Rogol A, Nyberg F, Bowers L, Bhasin S (2014). "Adverse health consequences of performance-enhancing drugs: An endocrine society scientific statement". Endocrine Reviews. 35 (3): 341–375. doi:10.1210/er.2013-1058. PMC 4026349. PMID 24423981. Waddington and Smith (2008); An Introduction to Drugs in Sport, Routledge. ISBN 978-0-415-43125-5. Collins R (2017). "Lowering Restrictions on Performance Enhancing Drugs in Elite Sports". Inquiries Journal. 9 (3). Retrieved 7 July 2017. Toby M (2024). The History of Performance-Enhancing Drugs In Thoroughbred Racing. University of Kentucky Press. ISBN 9780813197975.
==== Methanol ==== The methanol produced by aspartame metabolism is unlikely to be a safety concern for several reasons. The amount of methanol produced from aspartame-sweetened foods and beverages is likely to be less than that from food sources already in diets. With regard to formaldehyde, it is rapidly converted in the body, and the amounts of formaldehyde from the metabolism of aspartame are trivial when compared to the amounts produced routinely by the human body and from other foods and drugs. At the highest expected human doses of consumption of aspartame, there are no increased blood levels of methanol or formic acid, and ingesting aspartame at the 90th percentile of intake would produce 25 times less methanol than what would be considered toxic.
Sources: en.wikipedia.org
=== DNA concentration === The concentration of DNA can affect the rate of ligation, and whether the ligation is an inter-molecular or intra-molecular reaction. Ligation involves joining up the ends of a DNA with other ends, however, each DNA fragment has two ends, and if the ends are compatible, a DNA molecule can circularize by joining its own ends. At high DNA concentration, there is a greater chance of one end of a DNA molecule meeting the end of another DNA, thereby forming intermolecular ligation. At a lower DNA concentration, the chance that one end of a DNA molecule would meet the other end of the same molecule increases, therefore intramolecular reaction that circularizes the DNA is more likely. The transformation efficiency of linear DNA is also much lower than circular DNA, and for the DNA to circularize, the DNA concentration should not be too high. As a general rule, the total DNA concentration should be less than 10 μg/ml. The relative concentration of the DNA fragments, their length, as well as buffer conditions are also factors that can affect whether intermolecular or intramolecular reactions are favored. The concentration of DNA can be artificially increased by adding condensing agents such as cobalt hexamine and biogenic polyamines such as spermidine, or by using crowding agents such as polyethylene glycol (PEG) which also increase the effective concentration of enzymes.
Most applications of NMR involve full NMR spectra, that is, the intensity of the NMR signal as a function of frequency. Early attempts to acquire the NMR spectrum more efficiently than simple CW methods involved illuminating the target simultaneously with more than one frequency. A revolution in NMR occurred when short radio-frequency pulses began to be used, with a frequency centered at the middle of the NMR spectrum. In simple terms, a short pulse of a given "carrier" frequency "contains" a range of frequencies centered about the carrier frequency, with the range of excitation (bandwidth) being inversely proportional to the pulse duration, i.e. the Fourier transform of a short pulse contains contributions from all the frequencies in the neighborhood of the principal frequency. The restricted range of the NMR frequencies for most light spin-1/2 nuclei made it relatively easy to use short (1 - 100 microsecond) radio frequency pulses to excite the entire NMR spectrum. Applying such a pulse to a set of nuclear spins simultaneously excites all the single-quantum NMR transitions. In terms of the net magnetization vector, this corresponds to tilting the magnetization vector away from its equilibrium position (aligned along the external magnetic field). The out-of-equilibrium magnetization vector then precesses about the external magnetic field vector at the NMR frequency of the spins. This oscillating magnetization vector induces a voltage in a nearby pickup coil, creating an electrical signal oscillating at the NMR frequency.
However, the Nomenclature of Steroids recommends the locant of a double bond to be always adjacent to the syllable designating the unsaturation, therefore, having it as a suffix rather than a prefix, and without the use of the Δ character, i.e. pregn-4-ene-11β,17α-diol-3,20-dione or androst-4-ene-3,11,17-trione. The double bond is designated by the lower-numbered carbon atom, i.e. "Δ4-" or "4-ene" means the double bond between positions 4 and 5. The saturation of carbons of a parent steroid can be done by adding "dihydro-" prefix, i.e., a saturation of carbons 4 and 5 of testosterone with two hydrogen atoms is 4,5α-dihydrotestosterone or 4,5β-dihydrotestosterone. Generally, when there is no ambiguity, one number of a hydrogen position from a steroid with a saturated bond may be omitted, leaving only the position of the second hydrogen atom, e.g., 5α-dihydrotestosterone or 5β-dihydrotestosterone. The Δ5-steroids are those with a double bond between carbons 5 and 6 and the Δ4 steroids are those with a double bond between carbons 4 and 5. The abbreviations like "P4" for progesterone and "A4" for androstenedione for refer to Δ4-steroids, while "P5" for pregnenolone and "A5" for androstenediol refer to Δ5-steroids. The suffix -ol denotes a hydroxy group, while the suffix -one denotes an oxo group. When two or three identical groups are attached to the base structure at different positions, the suffix is indicated as -diol or -triol for hydroxy, and -dione or -trione for oxo groups, respectively.
=== Early years === Sidney Fox was the son of Jacob Fox, a wig-maker, and Louise Berman, a Ukrainian immigrant. Fox married Raia Joffe Fox and they had three sons: Lawrence, Ronald, and Thomas. All three of his sons became scientists. His family was Jewish. Fox obtained a Bachelor of Arts degree from University of California, Los Angeles in Chemistry. He went on to earn a Ph.D. from California Institute of Technology in 1940 and did his postdoctoral work at the Linus Pauling Laboratory where he grew close with Linus Pauling.
Over the coming decade, Libya developed stronger political and economic links with Dom Mintoff's Maltese administration, and under Libya's urging Malta did not renew the UK's airbases in 1980. Orchestrating a military build-up, the RCC began purchasing weapons from France and the Soviet Union. The commercial relationship with the latter led to an increasingly strained relationship with the US, which was then engaged in the Cold War with the Soviets.
Sources: en.wikipedia.org
Reversed-phase high-performance liquid chromatography is the standard method, with detection in the ultraviolet range. Peak area percentage yields a purity figure for the main component. Mass spectrometry is normally run alongside to confirm molecular identity.
Dry lyophilised powder is generally kept at minus twenty degrees Celsius, protected from light and moisture. Repeated freeze-thaw cycles are avoided because they encourage aggregation and moisture uptake. Solutions are less stable than the solid form and degrade faster at room temperature.
A certificate documents what the supplier measured, not what an independent party confirmed. Methods, instruments and acceptance criteria can differ between suppliers. Third-party testing is the usual way to resolve discrepancies.
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.