The short version of BDNF expression fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-08-31. Anything still debated is marked as such rather than presented as settled.
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.
Lyophilised powder is normally kept at -20 °C in a desiccated container, with some suppliers recommending -80 °C for long-term archival storage. Repeated freeze-thaw cycles are the most common cause of avoidable loss, so aliquoting before freezing reduces variability between working sessions. Dissolved peptide is far less stable than the dry solid and is usually prepared fresh or held briefly at 4 °C. Aqueous solutions support both hydrolysis of the backbone and oxidation of the N-terminal methionine, and these two routes dominate degradation under ordinary laboratory conditions.
Identity and purity are confirmed with reversed-phase high-performance liquid chromatography, typically monitored at 214 nanometres where the peptide bond absorbs. Mass spectrometry, either electrospray or MALDI-TOF, verifies molecular mass against the theoretical value and detects truncation or adduct formation. Amino acid analysis and peptide mapping provide additional confirmation when required. The most frequently reported impurities are deletion sequences from incomplete coupling, methionine sulfoxide from oxidation, and dimeric species formed through non-covalent aggregation. Impurity profiles depend strongly on the synthesis and purification route chosen by the producer.
Published research has focused mainly on neurological and cognitive endpoints in animal models, with proposed mechanisms involving brain-derived neurotrophic factor and related signalling pathways. A substantial share of the human data originates from a limited number of research groups, and independent replication in other countries remains sparse. Regulatory status reflects that distribution: the peptide is registered as a medicine in Russia and appears in some neighbouring markets, while elsewhere it is handled as a research chemical without approved therapeutic labelling. Questions about dose-response relationships, long-term effects, and comparability across studies are still open.
| Property | Value | Notes |
|---|---|---|
| Solid storage temperature | -20 °C or below | Desiccated and protected from light |
| Solution storage temperature | -80 °C as single-use aliquots | Avoid repeated freeze-thaw cycles |
| Purity assessment method | RP-HPLC, around 214 nm | Reported as main-peak area percent |
| Identity confirmation method | ESI-MS or MALDI-TOF | Measured mass compared with calculated mass |
| Common synonyms | ACTH(4-10) analog; Met-Glu-His-Phe-Pro-Gly-Pro | Also written as Semaxum in some sources |
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.
Purity assessment relies mainly on reversed-phase high-performance liquid chromatography, which separates the target heptapeptide from truncated sequences, deletion analogues, and oxidised forms. Mass spectrometry, usually coupled to liquid chromatography, confirms identity through the expected molecular ion and reveals modifications such as methionine sulfoxide formation. Amino acid analysis can verify composition, and tandem mass spectrometry supports sequence confirmation. Ultraviolet detection near 254 to 280 nanometres is convenient because the phenylalanine and histidine residues absorb in that region. Nuclear magnetic resonance is rarely used for routine release testing.
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.
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.
Western Region (Vancouver, Seattle, San Francisco Bay Area, Los Angeles) Central Region (Guadalajara, Mexico City, Monterrey, Houston, Dallas, Kansas City) Eastern Region (Atlanta, Miami, Toronto, Boston, Philadelphia, New York/New Jersey) However, even during the group stage, about half of the teams had to play matches in two different regions.
== See also == List of biochemists for people associated with biochemistry. List of biomolecules List of basic biochemistry topics most basic biochemistry topics that should be covered in an encyclopedia, organized by topic. List of chemistry topics, Chemistry basic topics List of biology topics, Biology basic topics List of molecular biology topics List of biochemistry topics
Paraxanthine (84%): Increases lipolysis, leading to elevated glycerol and free fatty acid levels in blood plasma. Theobromine (12%): Dilates blood vessels and increases urine volume. Theobromine is also the principal alkaloid in the cocoa bean (chocolate). Theophylline (4%): Relaxes smooth muscles of the bronchi, and is used to treat asthma. The therapeutic dose of theophylline, however, is many times greater than the levels attained from caffeine metabolism. 1,3,7-Trimethyluric acid is a minor caffeine metabolite. 7-Methylxanthine is also a metabolite of caffeine. Each of the above metabolites is further metabolized and then excreted in the urine. Caffeine can accumulate in individuals with severe liver disease, increasing its half-life. A 2011 review found that increased caffeine intake was associated with a variation in two genes that increase the rate of caffeine catabolism. Subjects who had this mutation on both chromosomes consumed 40 mg more caffeine per day than others. This is presumably due to the need for a higher intake to achieve a comparable desired effect, not that the gene led to a disposition for greater incentive of habituation. Caffeine can be easily protonated by strong acids to form corresponding caffenium salts. They are of interest because these cations are one of the main species in an acidic medium.
Sources: en.wikipedia.org
Based on MIC data and other studies, dalbavancin is more potent and bactericidal and therefore requires lower concentrations than vancomycin against these organisms. Dalbavancin also shows in vitro activity against vancomycin-susceptible Enterococcus faecium and Enterococcus faecalis. Other Gram-positive organisms belonging to the Bacillus spp., Listeria spp., and Corynebacterium spp. may show in vitro susceptibility, and dalbavancin may exhibit activity against enterococci expressing the VanB or VanC phenotype of acquired resistance against vancomycin. There is no clinically significant activity against Gram-negative bacteria.
=== Death and legacy === Several retrospective sources state that Liu was greatly saddened by Zhou Enlai's death in January 1976 and, according to Guangming Daily, even had himself carried on a stretcher to the Beijing Hospital to bid farewell to Zhou's remains. Having been diagnosed with cancer in 1975, Liu's own health deteriorated shortly after, and he died of his illness in Beijing on June 24, 1976. He was 81. His memorial service was held at the Babaoshan Revolutionary Cemetery and was presided by Vice Premier and general Chen Xilian. The June 30, 1976 issue of the People's Daily reported that Vice Chairperson Li Suwen delivered Liu's eulogy. According to the eulogy, Liu Wenhui supported Chairman Mao, the Cultural Revolution, the movement to criticize Lin Biao and Confucius, and finally the ongoing campaign against Deng Xiaoping. He had also called for the liberation of Taiwan from Kuomintang rule. Present at his funeral were several politicians including Wu De, Li Jingquan, Ngapoi Ngawang Jigme, and Zhou Jianren, among others. Marshals Zhu De, Ye Jianying, and Liu Bocheng sent wreaths to the funeral, as well as Hua Guofeng and Song Qingling.
Measurement of the electrical activity of the heart (ECG) Measurement of blood pressure, heart rate, and body temperature Blood sampling Urine sampling Weight and height measurement Drug abuse testing Pregnancy testing It has been observed that participants in clinical trials are disproportionately white. Often, minorities are not informed about clinical trials. One recent systematic review of the literature found that race/ethnicity as well as sex were not well-represented nor at times even tracked as participants in a large number of clinical trials of hearing loss management in adults. This may reduce the validity of findings in respect of non-white patients by not adequately representing the larger populations.
Conolidine is an indole alkaloid. Preliminary reports suggest that it could provide analgesic effects with few of the detrimental side-effects associated with opioid. Conolidine was first isolated in 2004 from the bark of the Tabernaemontana divaricata (crape jasmine) shrub which is used in traditional Chinese medicine. The first asymmetric total synthesis of conolidine was developed by Micalizio and coworkers in 2011. This synthetic route allows access to either enantiomer (mirror image) of conolidine via an early enzymatic resolution. Notably, evaluation of the synthetic material resulted in the discovery that both enantiomers of the synthetic compound show analgesic effects.
Sources: en.wikipedia.org
Each freeze-thaw cycle can degrade a fraction of the peptide and promote aggregation. Dividing a stock solution into single-use volumes removes repeated cycling as a variable. It also limits the time a thawed solution spends at room temperature.
A high main-peak percentage says little about identity, counter-ion content, or residual solvents. It also does not distinguish an isomer or a closely eluting analog. Mass confirmation and the accompanying documentation cover those gaps.
Salt form changes mass, solubility, and hygroscopicity, and acetate and trifluoroacetate salts behave differently in solution. Storage guidance still centers on -20 °C for powder and lower temperatures for solutions. The certificate should state which salt is present.
Reversed-phase HPLC gives the main purity figure, most often with UV detection near 214 nanometres. Mass spectrometry then confirms the molecular mass. Together the two methods distinguish a correct sequence from a closely related impurity.