The short version of RP-HPLC fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-08-19. 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.
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.
Lyophilized material is chemically stable for extended periods when kept dry, cold, and protected from light. The powder is hygroscopic, so vials should be warmed to room temperature before opening to reduce condensation on the contents. Once dissolved, the peptide is far less stable because peptide bonds are susceptible to hydrolysis and the methionine residue can oxidize. Solutions are typically aliquoted and held at 2-8 °C for short intervals or frozen for longer ones, and repeated freeze-thaw cycles should be avoided.
Routine characterization relies on reversed-phase high-performance liquid chromatography to establish purity and on mass spectrometry to confirm molecular identity. Electrospray ionization and matrix-assisted laser desorption ionization are both used for mass verification. Amino acid analysis and peptide mapping can detect sequence errors. Common impurities include truncated sequences, methionine sulfoxide formed by oxidation, and deamidated products. Chromatograms are usually recorded near 214 nm, where the peptide backbone absorbs, and purity is reported as the percentage area of the principal peak.
| 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 |
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。
纯度评估以反相高效液相色谱为主，通过主峰面积百分比给出粗略结果，再配合电喷雾质谱核对分子量。氨基酸分析可验证组成比例，手性色谱或毛细管电泳用于检查残基构型。常见杂质包括缺失序列的短肽、氧化产物与二聚体。由于多数市售品不附带完整检验报告，独立第三方检测常被用来核实标称值。
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。
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 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.
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.
Semax is supplied as a lyophilized powder that appears white to off-white. It dissolves readily in water, phosphate-buffered saline, and other aqueous media, which simplifies preparation of working solutions for laboratory use. The nasal products registered in Russia are dilute aqueous solutions, typically around 0.1 percent peptide by weight. Organic solvents are rarely necessary and can complicate handling. Because the peptide is hygroscopic, weighing should be performed quickly and with minimal exposure to ambient humidity.
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.
Tofisopam (Emandaxin, Grandaxin, Sériel) is an anxiolytic that is marketed in several European countries. Chemically, it is a 2,3-benzodiazepine. Unlike other anxiolytic benzodiazepines (which are generally 1,4- or 1,5-substituted) however, tofisopam does not have anticonvulsant, sedative, skeletal muscle relaxant, motor skill-impairing or amnestic properties. While it may not be an anticonvulsant in and of itself, it has been shown to enhance the anticonvulsant action of classical 1,4-benzodiazepines (such as diazepam) and muscimol, but not sodium valproate, carbamazepine, phenobarbital, or phenytoin. Tofisopam is indicated for the treatment of anxiety and alcohol withdrawal, and is prescribed in a dosage of 50–300 mg per day divided into three doses. Peak plasma levels are attained two hours after an oral dose. Tofisopam is not reported as causing dependence to the same extent as other benzodiazepines, but is still recommended to be prescribed for a maximum of 12 weeks. Tofisopam is not approved for sale in the United States or Canada. However, Vela Pharmaceuticals of New Jersey is developing the D-enantiomer (dextofisopam) as a treatment for irritable bowel syndrome, with moderate efficacy demonstrated in clinical trials so far. Tofisopam is also claimed to be a PDE10A inhibitor, which may provide an alternative mechanism of action for its various therapeutic effects, and this action has been proposed to make tofisopam potentially useful as a treatment for schizophrenia.
=== Legal status === In February 2023, the Committee for Medicinal Products for Human Use of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Hyftor, intended for the treatment of angiofibroma. The applicant for this medicinal product is Plusultra pharma GmbH. Hyftor was authorized for medical use in the European Union in May 2023. Sirolimus, as Rapamune solution, was approved for medical use in the United States in 1999; and as Rapamune tablets in August 2000. Sirolimus, as Fyarro, was approved for medical use in the United States in November 2021. Sirolimus, as Hyftor, was approved for medical use in the United States in March 2022.
Transgender health care includes the prevention, diagnosis and treatment of physical and mental health conditions which affect transgender individuals. A major component of transgender health care is gender-affirming care, the medical aspect of gender transition. Questions implicated in transgender health care include gender variance, sex reassignment therapy, health risks (in relation to violence and mental health), and access to healthcare for trans people in different countries around the world. Gender-affirming health care can include psychological, medical, physical, and social behavioral care. The purpose of gender-affirming care is to help a transgender individual conform to their desired gender identity. In the 1920s, physician Magnus Hirschfeld conducted formal studies to understand gender dysphoria and human sexuality and advocated for communities that were marginalized. His research and work provided a new perspective on gender identity, gender expression, and sexuality. This was the first time there was a challenge against societal norms. In addition to his research, Hirschfeld also coined the term transvestite, which in modern terms is known as "transgender". Hirschfeld's work was ended during the Nazi German era when many transgender individuals were arrested and sent to concentration camps.
Sources: en.wikipedia.org
With the development of X-ray crystallography, it became possible to determine protein structures as well as their sequences. The first protein structures to be solved were hemoglobin by Max Perutz and myoglobin by John Kendrew, in 1958. The use of computers and increasing computing power has supported the sequencing of complex proteins. In 1999, Roger Kornberg sequenced the highly complex structure of RNA polymerase using high intensity X-rays from synchrotrons. Since then, cryo-electron microscopy (cryo-EM) of large macromolecular assemblies has been developed. Cryo-EM uses protein samples that are frozen rather than crystals, and beams of electrons rather than X-rays. It causes less damage to the sample, allowing scientists to obtain more information and analyze larger structures. Computational protein structure prediction of small protein structural domains has helped researchers to approach atomic-level resolution of protein structures. As of April 2024, the Protein Data Bank contains 181,018 X-ray, 19,809 EM and 12,697 NMR protein structures.
Dogs, the first domesticated animal, have been used in hunting, in security and in warfare, as have horses, pigeons and birds of prey; while other terrestrial and aquatic animals are hunted for sports, trophies or profits. Non-human animals are also an important element of human culture, having appeared in cave arts and totems since the earliest times, and are frequently featured in mythology, religion, arts, literature, heraldry, politics, and sports.
==== Autonomic problems ==== Although neurogastroenterological manifestations in connective tissue disorders are common, their root cause is not yet known. Splanchnic circulation, small fiber neuropathy and altered vascular compliance have all been named as potential contributors to gastrointestinal complaints, particularly for patients who have a known, comorbid autonomic condition. Dysautonomia symptoms, autonomic system dysfunction, in hEDS is associated with exercise intolerance and cardiac atrophy.
=== First signs === The first sign of flerovium was found in December 1998 by a team of scientists at Joint Institute for Nuclear Research (JINR), Dubna, Russia, led by Armenian nuclear scientist Yuri Oganessian, who bombarded a target of plutonium-244 with accelerated nuclei of calcium-48:
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.
Dry powder is normally held at -20 °C or lower, away from light and moisture. Sealed vials can also be kept at 2-8 °C for shorter intervals. Warming to room temperature before opening prevents condensation.