A practical reference on reversed-phase HPLC: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-04-27 and is reviewed periodically as new material appears.
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.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It corresponds to the ACTH(4-7) fragment extended at the C-terminus by a Pro-Gly-Pro tripeptide, an addition intended to slow enzymatic breakdown. The molecular formula is C37H51N9O10S and the molecular mass is approximately 814 daltons. In the literature it is often described as an ACTH(4-10) analog, although that label reflects a naming convention as much as a precise structural relationship. The compound was developed in Russia and remains most closely associated with that research tradition.
Laboratory descriptions of the material are consistent across suppliers. It appears as a white to off-white lyophilized powder that dissolves readily in water and in polar organic solvents such as dimethyl sulfoxide. Aqueous solutions are clear and colorless at low concentrations. Because the peptide contains methionine, oxidation at the sulfur atom is a recognized degradation pathway, and handling notes usually call for protected, desiccated storage. Reported purity for research-grade lots is generally above 95 percent as measured by reversed-phase high-performance liquid chromatography.
The compound is registered in Russia as a pharmaceutical product, most commonly formulated as a nasal solution, and has been used in that setting since the 1990s. Outside that jurisdiction it is generally handled as a research chemical rather than an approved medicine. Regulatory status therefore differs sharply between countries, and material sold internationally may not correspond to the Russian pharmaceutical formulation. Documentation with commercial samples is typically limited to a certificate of analysis covering purity and identity, not clinical status or local legal classification.
| 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 |
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.
各国监管态度分化明显。俄罗斯按处方药管理，部分东欧国家留有使用记录；欧盟与美国未批准其作为药物上市，市面流通品通常标注为研究用化学品。身份差异意味着标示含量、纯度与无菌性缺少统一核查。体育领域还牵涉反兴奋剂名录，跨境携带则受目的地药品法规约束。
Semax 是人工设计的七肽，序列为 Met-Glu-His-Phe-Pro-Gly-Pro，骨架取自促肾上腺皮质激素片段 ACTH(4-10)。它于二十世纪八十年代在苏联的分子遗传学研究机构内合成。设计目标是保留该片段与注意力和记忆相关的活性，同时剔除促皮质激素释放等内分泌作用。此后俄罗斯将其登记为药品并进入临床使用。
当时的短肽研究普遍关注能否穿越血脑屏障、在低剂量下产生中枢效应，Semax 属于这一路线。鼻内给药是其主要使用方式，俄语文献报道的适应症涵盖缺血性卒中、短暂性脑缺血发作、认知功能减退以及视神经病变。这些研究大多发表在当地期刊上，样本规模与终点设置同西方试验惯例存在差异，国际同行对其临床证据的强度看法不一。
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.
Semax is a synthetic seven-amino-acid peptide whose sequence extends the ACTH(4-10) fragment with a C-terminal proline-glycine-proline tripeptide. The commonly cited sequence is Met-Glu-His-Phe-Pro-Gly-Pro, giving a molecular formula near C37H51N9O10S and a molecular weight close to 813.9 g/mol. It belongs to the broader class of synthetic ACTH fragments studied for central nervous system effects rather than for adrenal steroid stimulation. In practice the material appears as a lyophilized white powder for laboratory work or as a dilute saline solution in clinical settings.
Development is attributed to researchers at the Institute of Molecular Genetics in Moscow during the early 1980s, building on earlier Soviet work with ACTH fragments. Russian regulatory approval followed for intranasal use, and the compound has remained commercially available there for decades. Most published human data originate from Russian and, later, some Eastern European clinical reports, which are not always accessible in English translation. Outside that region the material is generally handled as a research chemical rather than a licensed medicine.
In the remote troposphere, hydrogen peroxide (H₂O₂) and methyl hydroperoxide (CH₃OOH) are among the most abundant hydroperoxides and act as reservoirs for HOx (OH + HO₂), buffering radical concentrations and tracing oxidation chemistry. Formation in the remote troposphere is dominated by peroxy-radical chemistry: HO₂ + HO₂ → H₂O₂ + O₂ and CH₃O₂ + HO₂ → CH₃OOH + O₂ Global aircraft observations during NASA's Atmospheric Tomography (ATom) mission show that their distributions reflect formation via peroxy-radical chemistry and are modulated by season and recent convection. Under atmospheric conditions, the reaction of organic peroxyl radicals (RO₂) with HO₂—an important source of ROOH—exhibits a generally negative temperature dependence, and its product branching competes with RO₂ autoxidation (isomerization) and RO₂+RO₂ channels. Many functionalized RO₂ types (for example, β-hydroxy or highly oxygenated RO₂) still lack good laboratory data on rates and products. Because of that, the predicted ROOH yields—and how they change with temperature—remain uncertain.
'The All-Species Living Tree' Project (LTP) is a collaboration between various academic groups/institutes, such as ARB, SILVA rRNA database project, and LPSN, with the aim of assembling a database of 16S rRNA sequences of all validly published species of Bacteria and Archaea. At one stage, 23S sequences were also collected, but this has since stopped. Currently there are over 10,950 species in the aligned dataset and several more are being added either as new species are discovered or species that are not represented in the database are sequenced. Initially the latter group consisted of 7% of species. Similar (and more recent) projects include the Genomic Encyclopedia of Bacteria and Archaea (GEBA), which focused on whole genome sequencing of bacteria and archaea.
In 2024, Apple Inc. released Apple Vision Pro. This device features hardware such as dual panels that offer 24 million pixels, surpassing devices such as the Oculus Rift. The integration of the R1 chip, working in tandem with the M2 chip, results in a polling rate of 12 milliseconds, getting rid of the dizzying latency issues that were prevalent in previous devices.
Sources: en.wikipedia.org
Extracting oil (or "bitumen") from oil/tar sand and oil shale deposits requires mining the sand or shale and heating it in a vessel or retort, or using "in-situ" methods of injecting heated liquids into the deposit and then pumping the liquid back out saturated with oil.
== Genetic coding == In 1993, the gene sequence of CK1δ was initially described by Graves et al. who isolated the cDNA from testicles of rats. After sequencing and characterization of the gene, the construct was described as a 1284 nucleotide sequence resulting in a protein consisting of 428 amino acids after transcription. The molecular weight of the according protein was published as 49 kDa. Three years later, the same gene was identified in humans. The human CSNK1D contains 1245 nucleotides and is transcribed into a protein consisting of 415 amino acids. Ever since, CK1δ was investigated and described in various animals, plants, as well as parasites (Caenorhabditis elegans, 1998; Drosophila melanogaster, 1998; Mus musculus, 2002; Xenopus laevis, 2002.)
As a paramilitary unit, the BSAP fought in the Second Boer War and in German East Africa during the First World War, while some members were seconded to the Rhodesia Native Regiment. From 1923, Southern Rhodesia was a self-governing colony of the British Empire, but the BSAP retained its title and its position as the senior regiment of the Southern Rhodesian armed forces. One of the first casualties of the BSAP in the Second World War was Keppel Bagot Levett, born in 1919, who died in active service with the BSAP in March 1941. Between the World Wars, the Permanent Staff Corps of the Rhodesian Army consisted of only 47 men. The BSAP were trained as both policemen and soldiers until 1954.
The basal lamina is a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits. It is one of two layers of the basement membrane. The basal lamina is visible only with the electron microscope, where it appears as an electron-dense layer that is 20–100 nm thick. It is thicker in the alveoli of the lungs, and in the kidney glomeruli.
Sources: en.wikipedia.org
== Structural classes == Enzyme inhibitors are a chemically diverse set of substances that range in size from organic small molecules to macromolecular proteins. Small molecule inhibitors include essential primary metabolites that inhibit upstream enzymes that produce those metabolites. This provides a negative feedback loop that prevents over production of metabolites and thus maintains cellular homeostasis (steady internal conditions). Small molecule enzyme inhibitors also include secondary metabolites, which are not essential to the organism that produces them, but provide the organism with an evolutionary advantage, in that they can be used to repel predators or competing organisms or immobilize prey. In addition, many drugs are small molecule enzyme inhibitors that target either disease-modifying enzymes in the patient or enzymes in pathogens which are required for the growth and reproduction of the pathogen. In addition to small molecules, some proteins act as enzyme inhibitors. The most prominent example are serpins (serine protease inhibitors) which are produced by animals to protect against inappropriate enzyme activation and by plants to prevent predation. Another class of inhibitor proteins is the ribonuclease inhibitors, which bind to ribonucleases in one of the tightest known protein–protein interactions. A special case of protein enzyme inhibitors are zymogens that contain an autoinhibitory N-terminal peptide that binds to the active site of enzyme that intramolecularly blocks its activity as a protective mechanism against uncontrolled catalysis.
As for second-hand smoke, the NIH study points to the large amount of smoke generated by one cigar, saying "cigars can contribute substantial amounts of tobacco smoke to the indoor environment; and, when large numbers of cigar smokers congregate in a cigar smoking event, the amount of passive smoke produced is sufficient to be a health concern for those regularly required to work in those environments". Smoking also tends to increase blood cholesterol levels. Furthermore, the ratio of high-density lipoprotein (HDL, commonly referred to as "good" cholesterol) to low-density lipoprotein (LDL, "bad" cholesterol) tends to be lower in smokers compared to non-smokers. Smoking also raises the levels of fibrinogen and increases platelet production (both involved in blood clotting), which makes the blood thicker and more likely to clot. Carbon monoxide binds to hemoglobin (the component carrying the oxygen in red blood cells), resulting in a much more stable complex than hemoglobin bound with oxygen or carbon dioxide and therefore permanent loss of blood cell functionality. Blood cells are naturally recycled after a certain period, allowing for the creation of new, functional red blood cells. However, if carbon monoxide exposure reaches a certain point before it can be recycled, hypoxia (and later death) occurs. All these factors make smokers more at risk of developing various forms of arteriosclerosis (hardening of the arteries).
=== 7 May === Mikhail Razvozhayev, the Russian-installed governor of Crimea, claimed that Russian forces stopped a Ukrainian drone attack using air defence and electronic warfare, downing three of the drones without property damage or casualties.
=== Contamination recalls === Considering the animal source of pharmaceutical heparin, the number of potential impurities is relatively large compared with a wholly synthetic therapeutic agent. The range of possible biological contaminants includes viruses, bacterial endotoxins, transmissible spongiform encephalopathy (TSE) agents, lipids, proteins, and DNA. During the preparation of pharmaceutical-grade heparin from animal tissues, impurities such as solvents, heavy metals, and extraneous cations can be introduced. However, the methods employed to minimize the occurrence and to identify and/or eliminate these contaminants are well established and listed in guidelines and pharmacopeias. The major challenge in the analysis of heparin impurities is the detection and identification of structurally related impurities. The most prevalent impurity in heparin is dermatan sulfate (DS), also known as chondroitin sulfate B. The building block of DS is a disaccharide composed of 1,3-linked N-acetyl galactosamine (GalN) and a uronic acid residue, connected via 1,4 linkages to form the polymer. DS is composed of three possible uronic acids (GlcA, IdoA, or IdoA2S) and four possible hexosamine (GalNAc, Gal- NAc4S, GalNAc6S, or GalNAc4S6S) building blocks. The presence of iduronic acid in DS distinguishes it from chondroitin sulfate A and C and likens it to heparin and HS. DS has a lower negative charge density overall compared to heparin.
=== Cannabinoid hyperemesis syndrome === Aprepitant has been identified as having strong potential in treating protracted vomiting episodes in individuals with cannabinoid hyperemesis syndrome. This syndrome is characterized by nausea, cyclical vomiting, and cramping abdominal pain resulting from prolonged, frequent cannabis use. Standard first-line antiemetics such as ondansetron and prochlorperazine are often ineffective in treating cannabinoid hyperemesis syndrome.
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.
It is registered as a pharmaceutical product in Russia, where it is typically supplied as a nasal solution. In most other countries it is not an approved drug and is traded as a research chemical instead. Approval status depends entirely on the jurisdiction involved.