BDNF expression 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 2025-08-09. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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 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.
| Property | Value | Notes |
|---|---|---|
| Typical purity specification | ≥ 95 % of peak area by HPLC | Some suppliers quote 98 % or higher |
| Identity confirmation | Mass spectrometry (electrospray or MALDI) | Observed mass is compared with the calculated mass |
| Common analytical method | Reversed-phase HPLC on a C18 column | Acetonitrile and water gradients with trifluoroacetic acid |
| Primary degradation route | Oxidation of the methionine residue | Yields a sulfoxide that separates cleanly on chromatography |
| Storage of dissolved material | Aliquoted and frozen at −20 °C or below | Single-use aliquots avoid repeated temperature cycling |
Published studies examine a fairly narrow set of endpoints. Rodent experiments commonly measure maze learning, infarct volume after induced ischemia, and tissue levels of neurotrophic factors. Clinical reports from Russian centres describe attention, memory and recovery scores in patients after stroke or transient ischemic attack. Most of those human studies are small and few have been repeated by independent groups. Outcome measures differ between studies, which limits direct comparison.
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.
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.
Once dissolved, the peptide is considerably less stable than the solid. Aqueous solutions are usually prepared at neutral to slightly acidic pH, filtered, and divided into single-use aliquots before freezing. Repeated freeze-thaw cycles are a common cause of avoidable loss and are best prevented by never refreezing a thawed aliquot. Adsorption to plastic and glass surfaces can lower the measured concentration of dilute solutions, particularly below roughly 0.1 mg/mL. Buffer choice, salt content, and container material all influence how much peptide remains detectable after storage.
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.
==== City 17 ==== During the development of Half-Life 2, Antonov was promoted from a concept artist to being the game's art director. He was the principal designer of its dystopian setting of City 17: a decaying Eastern European city in an unspecified location, occupied by the Combine, an alien empire that invaded Earth (during and after the events of the first Half-Life) and established an oppressive world government. City 17 features numerous Soviet-era concrete buildings in the Brutalist style, as well as structures constituting the Combine's surveillance state which are built like a series of panopticons: a type of prison in which a single guard can monitor every prisoner simultaneously from a central tower, but each prisoner is not able to see whether they are being watched. Ted Litchfield writes for PC Gamer that the Combine's "invasive, angular, [and] alien" architecture "latch[es] onto the human architecture underneath like tumors". In the middle of City 17 is the Combine's Citadel, a skyscraper far taller than any of its surroundings, at one to five miles high (according to fan estimates). The empire uses it as a stronghold, to expand its army, and to surveil the city's residents. Half-Life 2's player character Gordon Freeman must travel to and enter the Citadel to damage the Combine's infrastructure. Antonov used Half-Life 2 as an opportunity to game explore an urban Eastern European setting. He felt that such a setting was underused in popular fiction, and that putting it in Half-Life 2 would lead to a "specific, as opposed to generic" aesthetic.
=== Foreskin retraction === During puberty, if not before, the tip and opening of a male's foreskin becomes wider, progressively allowing for retraction down the shaft of the penis and behind the glans, which ultimately should be possible without pain or difficulty. The membrane that bonds the inner surface of the foreskin with the glans disintegrates and releases the foreskin to separate from the glans. The foreskin then gradually becomes retractable. Research by Øster (1968) found that with the onset and continuation of puberty, the proportion of males able to pull back their foreskins increased. At ages 12–13, Øster found that only 60% of males were able to retract their foreskins; this increased to 85% by ages 14–15, and 95% by 16–17. He also found that 1% of those unable to fully retract experienced phimosis at ages 14–17, the remainder were partially able to. The findings were supported by further research by Kayaba et al (1996) on a sample of over 600 males, and Ishikawa and Kawakita (2004) found that by age 15, 77% of their sample of males could retract their foreskins. Beaugé (1997) reports that males may assist the development of retractile foreskin by manual stretching.
== Sovereign Principality of the United Netherlands (1813–1815) == Following the collapse of the Napoleonic regime, and allied forces drove out the French in 1813, the Dutch called back William Frederick, the son of the last stadtholder William V, to head the new government. He was proclaimed "sovereign prince" and the country briefly existed as the Sovereign Principality of the United Netherlands.
Sources: en.wikipedia.org
In addition, people with trisomy 21 (Down syndrome), most of whom have an extra copy of the gene for APP, almost universally develop the symptoms and neuropathology of Alzheimer's disease by 40 years of age. Conversely, people with a rare mutation in the APP gene that reduces the production of Aβ and its tendency to aggregate are protected against Alzheimer's disease. Additionally, a major genetic risk factor for Alzheimer's disease is a specific isoform of apolipoprotein E, APOE4. Of the three major isoforms (APOE2, APOE3 and APOE4), APOE4 is linked to the least efficient removal of Aβ by astrocytes, which promotes the buildup of Aβ in the brain. The most efficient clearance of Aβ is achieved by cells bearing the APOE2 isoform, which protects against Alzheimer's disease. Evidence from tests such as imaging of protein deposits in the brain and measurement of brain-derived substances in cerebrospinal fluid and blood implicates abnormalities of Aβ as the earliest and most robust disease-specific change in Alzheimer's disease. The tau hypothesis proposes that abnormalities of the tau protein initiate the disease cascade, at least in cases of idiopathic Alzheimer's disease. The tau hypothesis is supported by the histopathological findings of Heiko Braak and colleagues that tauopathy can be detected in certain neurons before Aβ plaques are evident. Specifically, Alzheimer's starts with the hyperphosphorylation of tau in specific vulnerable neuronal populations such as the locus coeruleus and projection neurons of the association cortex.
== Differential diagnosis == Other disorders that may be accompanied by chorea include benign hereditary chorea, bilateral striatal necrosis, abetalipoproteinemia, ataxia–telangiectasia, biotin-thiamine-responsive basal ganglia disease (BTBGD), Fahr disease, familial dyskinesia–facial myokymia (Bird–Raskind syndrome) due to an ADCY5 gene mutation, glutaric aciduria, Lesch–Nyhan syndrome, mitochondrial disorders, Huntington's disease, Wilson disease, hyperthyroidism, lupus erythematosus, pregnancy (chorea gravidarum), drug intoxication and side effects of certain anticonvulsants (e.g. phenytoin) or psychotropic agents. Although some of these can similarly present in an acute way, there will typically be other neurological signs (such as ataxia or cognitive impairment), or other disease manifestations, or positive family history, which will help distinguish between them.
=== Figure skating scandals === Attack on Nancy Kerrigan - Nancy Kerrigan was attacked after a practice session at the 1994 U.S. Figure Skating Championships. Kerrigan's main team competitor, Tonya Harding, was accused of being involved in the attack. Kamila Valieva's failed drug test - Kamila Valieva failed a drug test for a banned heart medication in December 2021. This drug test result only surfaced after the figure skating team event in the 2022 Beijing Olympic Games, in which she competed for the ROC. Despite the result of the drug test, Kamila Valieva was cleared to skate in the Beijing 2022 singles event by the Court of Arbitration for Sport the following week, as she was considered a protected person due to being only 15 years of age. This decision was highly controversial and has resulted in the minimum age for competing in the Olympic Games for figure skating to rise from 15 years of age to 17 years of age.
==== Formation of the UPP ==== The Unidade de Polícia Pacificadora (Pacifying Police Units) or UPP was a security program in Rio de Janeiro that aimed to reclaim favelas from criminal organizations, such as CV, ADA, and TCP, through community policing. The strategy worked in two parts: deployment of the Military Police of Rio (PMERJ) into the favelas, and then increasing the amount of police officers who were meant to interact with the community through units, in hopes of creating a healthier relationship between favela residents and law enforcement than what existed in years prior. For decades, interactions with police in Rio de Janeiro were abrasive; violent conflicts between drug traffickers and the police led to widespread civilian casualties, and numerous instances of abuses of power by the police led to a general distrust by favela residents. The creation of the UPP aimed to both restructure the police force and its interactions with civilians, while also deterring criminal activity leading up to the 2014 World Cup and 2016 Summer Olympics. A secondary component of the UPP plan was the creation of UPP Social, which aimed to address the social welfare needs of the favelas by UPP units. This included improvements to sanitation, education, and healthcare, among other social issues. In 2008, the first UPP was set up in the Santa Marta favela, with more quickly following -- coalescing in 32 units overall, spanning all of Rio de Janeiro's zones (though most were located in Zona Norte).
Sources: en.wikipedia.org
== Benefits to fresh produce == Modifying the atmosphere inside fresh produce packaging to provide lowered levels of O2 and elevated levels of CO2 is beneficial for many fresh produce items and "can reduce respiration, decrease ethylene production and action, retard tissue ripening and softening, retard chlorophyll degradation and biosynthesis of carotenoids and anthocyanins, reduce enzymatic browning, alleviate physiological disorders and chilling injury, retard development of decay, and maintain nutritional quality of produce. The effect of decreased O2 and increased CO2 on senescence and ripening process are additive and can be synergistic." "In vegetative tissues MAP can also reduce leaf regrowth (green onion and leek), stem toughening (asparagus), and leaf sprouting and rooting in root vegetables (parsnip, radishes). The delay of ripening and senescence of fruits and vegetables also reduces their susceptibility to pathogens."
== Early life and education == Gibson was born in Montreal and studied psychology at the University of Victoria, where between 1973 and 1974 he drew weekly comics for the student newspaper. After completing his Bachelor of Arts degree in 1974 he moved to Vancouver. He lived in London, England from 1983 to 1989. He received a Master of Science degree in Interactive Art and Technology from Simon Fraser University, Surrey in 2004.
These emigrants primarily consisted Trekboers, frontier farmers in the East who had been at the front of the colony's eastward expansion. The emigration became known as the Great Trek and the emigrants Voortrekkers. Details on the various motives behind the Great Trek are laid out in the Voortrekker leader, Piet Retief's 1837 manifesto. The Voortrekkers first moved east into the territory later known as Natal. In 1839, they founded the Natalia Republic as a new Boer homeland. Other Voortrekker parties moved north, settling beyond the Orange and Vaal rivers. Disregarding the Voortrekkers' effortful attempt to claim independence, Britain annexed the Natalia Republic in 1843, which became the Crown colony of Natal. After 1843, British government policy turned strongly against further expansion in South Africa. Although there were some abortive attempts to annex more territories to the north, Britain formally recognised their independence by the Sand River Convention of 1852 and the Orange River Convention of 1854, for the Transvaal and the Orange Free State, respectively.
Sources: en.wikipedia.org
Suppliers normally quote a percentage of total chromatographic peak area, most often from reversed-phase HPLC. That figure says nothing about what the remaining percentage contains, and it depends on the detection wavelength used. A mass spectrometry result is a separate and stronger check on identity.
The methionine residue at the start of the chain is vulnerable to oxidation, producing a sulfoxide variant. Amide bonds can also hydrolyze, though more slowly under neutral conditions. Cold storage, oxygen exclusion and minimization of freeze-thaw cycles slow both processes but do not stop them.
A purity number on a certificate does not establish that a powder is the same product as a registered nasal medicine. Counter-ion content, residual solvents and peptide-related impurities may differ between the two. Independent verification is the only way to narrow that gap.
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.