The short version of ACTH fragment fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-02-01. Anything still debated is marked as such rather than presented as settled.
Common degradation pathways include oxidation of the methionine side chain, hydrolysis of the peptide backbone, and aggregation under unfavourable pH or concentration. Stability studies typically monitor the main peak by chromatography and report total related substances as a percentage. Because no official monograph exists, acceptance criteria vary between laboratories, and reported purity values are not directly comparable across suppliers. Analysts therefore document the method, column, and detection wavelength alongside each result, and open questions remain about how much biological activity the oxidised forms retain.
Solid semax is typically supplied as a lyophilised powder that is hygroscopic and sensitive to moisture, light, and repeated temperature cycling. Long-term storage of the dry peptide is generally recommended at approximately -20 degrees Celsius, while shorter working periods may use refrigeration at 2 to 8 degrees Celsius. Vials should remain tightly closed and desiccated when brought to room temperature, because condensation can damage the material before it is weighed. Dividing a batch into aliquots is preferable to thawing one container repeatedly.
Dissolution is normally performed in water, phosphate-buffered saline, or normal saline, since the peptide is freely soluble in aqueous media and is rarely handled with strong organic solvents. Solution pH should be kept near neutral, because extreme acidity or alkalinity accelerates backbone hydrolysis and encourages oxidation of the methionine side chain. Once dissolved, the material is less stable than the dry powder and is commonly divided into single-use portions and frozen. Buffers containing primary amines, such as Tris, are often avoided because of possible side reactions.
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.
| Property | Value | Notes |
|---|---|---|
| Typical analytical method | Reversed-phase HPLC with UV detection | Separates target peptide from truncated and oxidised forms |
| Identity confirmation | LC-MS or ESI-MS | Compares observed and calculated molecular ion |
| Primary degradation route | Methionine oxidation | Forms the sulfoxide; monitored as an early-eluting peak |
| Short-term storage | 2 to 8 degrees Celsius | Applies to working vials and reconstituted portions |
| Common synonyms | ACTH(4–10) analogue, MEHFPGP | Descriptive names used in laboratory catalogues |
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.
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.
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.
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.
Identity and purity are commonly assessed by reversed-phase high-performance liquid chromatography, with ultraviolet detection near 214 nanometers for the peptide backbone. Mass spectrometry, either electrospray or matrix-assisted laser desorption, confirms molecular mass and detects truncation or modification products. Amino acid analysis can verify composition. Because the sequence contains no strongly absorbing aromatic residue apart from phenylalanine, detection wavelengths are chosen carefully. Purity values above 95 percent are typical for research-grade material.
Quality documentation for research-grade peptide usually includes a certificate of analysis stating purity, identity, and residual counterion content. Batch-to-batch variation in purity and salt form is a recognized issue, and comparisons across suppliers require attention to the exact counterion, for example acetate versus trifluoroacetate. Sequence verification by tandem mass spectrometry provides stronger evidence than a single mass measurement. For any study reporting biological results, the analytical method and the measured purity should be stated explicitly. Independent verification of supplier claims is considered good practice.
=== Pharmacodynamics === 3-HO-PCP acts as a high-affinity uncompetitive NMDA receptor antagonist via the PCP site with a Ki of 30 nM. It has a higher affinity than PCP, which has a Ki of 250 nM for this site (eight-fold higher). Unlike many other arylcyclohexylamines, including close analogues such as 3-Chloro-PCP and 3-MeO-PCP, 3-HO-PCP has a high affinity for various opioid receptors. It has a Ki value of 39–60 nM for the μ-opioid receptor, 140 nM for the κ-opioid receptor, and 42 nM for the σ1 receptor. It has weaker activity at the δ-opioid receptor, with a Ki of 2,300 nM.
MR-2034, or Mr-2034, also known as (–)-MR-2033, is a selective κ-opioid receptor (KOR) agonist of the benzomorphan family. Unlike other benzomorphan KOR agonists like cyclazocine and alazocine, MR-2034 does not also act on sigma receptors. In addition to the KOR, it has affinity for the μ-opioid receptor (MOR), but does not activate this receptor. The drug produces dose-dependent hallucinogenic and dysphoric effects in humans, as well as other effects such as dizziness, anxiety, and sedation. These effects can be blocked by the non-selective opioid receptor antagonist naloxone. The preceding findings led to the conclusion that the hallucinogenic and dysphoric effects of benzomorphans are mediated by the KOR rather than by sigma receptors. MR-2034 was first described in the scientific literature by 1975 and its hallucinogenic effects in humans were described in 1986.
{\displaystyle {\begin{aligned}\mathrm {M} _{p}({\ce {OH}})_{q}&\leftrightharpoons \mathrm {M} _{p}({\ce {OH}})_{q-1}^{+}+{\ce {OH-}}\\K_{\mathrm {b} }&={\frac {[\mathrm {M} _{p}({\ce {OH}})_{q-1}^{+}][{\ce {OH-}}]}{[\mathrm {M} _{p}({\ce {OH}})_{q}]}}\\\end{aligned}}}
=== Middle East === A Taco Bell opened in the United Arab Emirates in November 2008 in Dubai at the Dubai Mall. A fourth UAE location was also planned for Bawadi Mall in the city of Al Ain. The locations at Dubai Mall, Deira City Centre, and Mirdif City Centre have all closed and Taco Bell has completely pulled out of the Emirati market. Taco Bell is still open in Kuwait and has not been pulled out ever since from the Kuwaiti market, as the chain is franchised in this region by Kout Food Group.
Sources: en.wikipedia.org
The other common way for isotopes with a high neutron to proton ratio (n/p) to decay is beta decay, in which the nuclide changes elemental identity while keeping the same mass number and lowering its n/p ratio. For some isotopes with a relatively low n/p ratio, there is an inverse beta decay, by which a proton is transformed into a neutron, thus moving towards a stable isotope; however, since fission almost always produces products which are neutron heavy, positron emission or electron capture are rare compared to electron emission. There are many relatively short beta decay chains, at least two (a heavy, beta decay and a light, positron decay) for every discrete weight up to around 207 and some beyond, but for the higher mass elements (isotopes heavier than lead) there are only four pathways which encompass all decay chains. This is because there are just two main decay methods: alpha radiation, which reduces the mass number by 4, and beta, which leaves it unchanged. The four paths are termed 4n, 4n + 1, 4n + 2, and 4n + 3; the remainder from dividing the atomic mass by four gives the chain the isotope will follow in its decay. There are other decay modes, but they invariably occur at a lower probability than alpha or beta decay.
Michel Chrétien (born March 26, 1936) is a Canadian medical researcher specializing in neuroendocrinology research at the Institut de recherches cliniques de Montréal, or Clinical Research Institute of Montreal, (IRCM). He is a younger brother of former Canadian prime minister, Jean Chrétien.
11 January 1919: The Germans recapture Sarnowa and win in Battle of Zbąszyń; Polish victory in Battle of Szubin and capture Łabiszyn, Złotniki and Żnin. 12 January 1919: fighting near Leszno and Lipno. 13 January 1919: The Germans recapture Szamocin. 14 January 1919: The Commission of the NRL appeals to Roman Dmowski for help negotiate a ceasefire. 15 January 1919: failed attempt to recapture Szamocin by Poles. 16 January 1919 The first number of Tygodnik Urzędowy Naczelnej Rady Ludowej, with the laws of the NRL, is published. The Polish government of Ignacy Paderewski has two politicians of Greater Poland: Józef Englich, the minister of treasury, and Kazimierz Hącia, the minister of industry and trade. 17 January 1919: Men born in 1897, 1898, and 1899 are called up and drafted into Great Polish Army. 20 January 1919: the transfer of money to banks of Germany on the other side of the front line is forbidden. 21 January 1919 NRL creates oath of soldiers of Great Polish Army. 22 January 1919 Northern front: Poles are forced to leave Potulice. Southern front: Poles win the Battle of Robaczysko. Joseph Noulens is nominated by Supreme Council of Allied Countries as chief of Allied mission in Poland. 23 January 1919: Poles defend Miejska Górka after heavy fighting. 25 January 1919 Poles capture Babimost and Kargowa. All communication between Greater Poland and Germany is broken. Decree cancels Prussian prohibition of Polish language in schools.
Sources: en.wikipedia.org
Dry powder is usually kept at about -20 degrees Celsius for long-term storage and at 2 to 8 degrees Celsius for short working periods. Containers should stay sealed and protected from light and moisture to limit degradation.
Oxidation of the methionine residue to the sulfoxide is a frequently reported change, and it usually appears as an earlier-eluting peak in reversed-phase chromatography. Backbone hydrolysis products can also accumulate in aqueous solution.
Liquid chromatography coupled with mass spectrometry is the usual approach, because the observed molecular ion can be compared with a calculated mass of about 813.9 Da. Retention time alone does not establish identity.
Semax is based on the ACTH(4-10) fragment, a seven-amino-acid segment of adrenocorticotropic hormone. The synthetic peptide retains the core sequence while removing regions associated with endocrine activity. This modification is intended to isolate effects on the nervous system.