intranasal delivery raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-01-19 and is reviewed periodically as new material appears.
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.
常规纯度与身份确认依赖反相高效液相色谱，并辅以质谱测定分子量。氨基酸组成分析可用于验证序列构成，肽图分析则能进一步定位修饰或降解产物。杂质谱通常关注缺失序列肽、截短片段和氧化产物。不同方法的检出限并不相同，因此各实验室报告的纯度数值不宜直接横向比较。
多数实验室与市售的 Semax 以冻干粉形式提供。冻干粉通常建议保存在 -20 °C 或更低温度下，同时避免光照与反复升温。短期运输有时采用冷藏条件，但长期保存仍以冷冻为主。分包操作应尽量减少开盖次数，以降低吸湿和微生物污染的风险。开封后若未一次用完，建议在干燥环境中密封并尽快放回低温储存。
溶液状态的稳定性明显低于冻干粉。肽类在水溶液中可能经历水解、氧化与聚集，其中甲硫氨酸和天冬酰胺等残基常是敏感位点。Semax 含有甲硫氨酸，因此氧化风险相对突出。工作液一般主张现配现用，或冷藏并在数日内用尽。缓冲液种类、pH 和离子强度都会影响降解速率，而关于最佳条件的公开数据并不统一。
| Property | Value | Notes |
|---|---|---|
| Typical purity | ≥95% by HPLC | Research-grade material |
| Detection wavelength | 214 nm | Peptide bond absorbance |
| Reconstitution medium | Sterile water or saline | Prepare fresh or aliquot immediately |
| Storage (solution) | -80 °C, single-use aliquots | Avoid repeated freeze-thaw cycles |
| Common salt form | Acetate or trifluoroacetate | Affects mass and solubility |
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.
Published research covers ischemic stroke, traumatic brain injury, cognitive impairment, optic nerve conditions and attention-related measures. Much of the human evidence comes from small trials conducted in one country, which limits how far the results generalize. Animal models supply the larger share of the data, and effects seen in rodents do not transfer automatically to people. Reviews have noted that methodological reporting is often incomplete, making it difficult to pool results or compare treatment schedules across studies.
Pharmacokinetic accounts emphasize rapid breakdown. After intravenous dosing the intact peptide disappears from blood within minutes, and nasal delivery produces low but measurable concentrations. Metabolites rather than the parent molecule may account for part of the observed activity, although the relative contribution is unresolved. Dosing in the literature varies widely and no optimal schedule has been agreed. These gaps are regularly cited as a reason the findings have not produced broad clinical adoption beyond the original research setting.
Proposed mechanisms center on neurotrophic signaling rather than on classical melanocortin receptor activation. Rodent experiments have reported shifts in the expression of brain-derived neurotrophic factor and nerve growth factor after administration, together with changes in the associated receptor systems. Several authors argue that the peptide acts largely through its degradation products and their interaction with peptidergic pathways, but this remains a hypothesis rather than a settled finding. No single molecular target has been identified in a way that the field broadly accepts.
While neurotherapy is a relatively young medical treatment in conventional Western biomedicine (that relies on a scientific approach and evidence-based practice), different age-old cultural practices of traditional Indian, Egyptian, and Chinese medicine have been using neuromodulation elements thousands of years ago. Long before humans discovered the science of electricity, ancient physicians used electric currents to treat various physical and mental conditions, including epilepsy, vertigo, and depression. In the ancient world, nature fulfilled many roles now served by technology, including providing sources of electricity. Before electricity was formally understood, people utilized electric fish to deliver therapeutic shocks. The Egyptians knew of the Nile catfish (Malapterurus electricus), capable of producing electric shocks. A depiction of this fish, dating back to 2750 BC, is found in a mural in the tomb of the architect Ti at Saqqara, Egypt. Egyptians weren't the only Mediterranean culture to feature the catfish in their art; similar murals appeared in the Roman city of Pompeii some 3,000 years later, though 1,000 miles to the north. While these murals don't confirm whether the fish were used medically, ancient Egyptian writings on papyri from 4,700 years ago document their use in pain relief. Later historians like Pliny and Plutarch also noted that Egyptians employed electric eels to treat joint pain, migraines, depression, and epilepsy.
Homoserine dehydrogenase catalyzes the reaction of aspartate-semialdehyde (ASA) to homoserine. The overall reaction reduces the C4 carboxylic acid functional group of ASA to a primary alcohol and oxidizes the C1 aldehyde to a carboxylic acid. Residues Glu 208 and Lys 117 are thought to be involved in the active catalytic site of the enzyme. Asp 214 and Lys 223 have been shown to be important for hydride transfer in the catalyzed reaction. Once the C4 carboxylic acid is reduced to an aldehyde and the C1 aldehyde is oxidized to a carboxylic acid, experiments suggest that Asp 219, Glu 208 and a water molecule bind ASA in the active site while Lys 223 donates a proton to the aspartate-semialdehyde C4 oxygen. Homoserine dehydrogenase has an NAD(P)H cofactor, which then donates a hydrogen to the same carbon, effectively reducing the aldehyde to an alcohol. (Refer to figures 1 and 2). However, the precise mechanism of complete homoserine dehydrogenase catalysis remains unknown. The homoserine dehydrogenase-catalyzed reaction has been postulated to proceed through a bi-bi kinetic mechanism, where the NAD(P)H cofactor binds the enzyme first and is the last to dissociate from the enzyme once the reaction is complete. Additionally, while both NADH and NADPH are adequate cofactors for the reaction, NADH is preferred. The Km of the reaction is four-times smaller with NADH and the Kcat/Km is three-times greater, indicating a more efficient reaction. Homoserine dehydrogenase also exhibits multi-order kinetics at subsaturating levels of substrate.
== Diagnosis == Because of the varying symptoms of aortic dissection, the diagnosis is sometimes difficult to make. Concern should be increased in those with low blood pressure, neurological problems, and unequal pulses. The diagnosis of aortic dissection is made by visualization of the intimal flap on a diagnostic imaging test. The gold standard test is CT angiography of the aorta. Other possible tests include a CT scan of the chest, cardiac magnetic resonance (MRI), or echocardiography.
Hodgkin and Huxley approached the problem by developing a set of differential equations for the parameters that govern the ion channel states, known as the Hodgkin-Huxley equations. These equations have been extensively modified by later research, but form the starting point for most theoretical studies of action potential biophysics.
== Keratin removal == Keratin that is present in the hair, scales and in the epidermis of the skin is hydrolyzed in the presence of alkali (at pH values greater than 11.5). The disulfide bridges found in keratin protein are cleaved but can be reformed. Long periods of liming will result in hair removal. The main removal of keratin is performed during the unhairing operation. In traditional processing, liming and unhairing were indivisible and took place at the same time. During modern liming methods, and in particular the processing of sheepskins, the hair is removed first and then limed in a liming drum. In hair-save technology, the hides are unhaired first and then limed for a further 12–18 hours.
Sources: en.wikipedia.org
==== With under-18s ==== In July 2025, the Government announced their intention to reduce the voting age to 16 before the next general election. Following this, some pollsters conducted polling including 16–17-year-olds, although the voting age has not yet been reduced by law.
However, there has been another resurgence in interest in methenamine for recurrent UTI prevention since 2010 owing to increasing rates of bacterial resistance with antibiotics. Larger and higher-quality clinical trials of methenamine for UTI prevention, such as the United Kingdom ALTAR trial, have started to be published in the 2020s, and additional trials, such as the international European ImpresU trial, are also underway as of 2024.
== Functions == The protein encoded by this gene is a member of the fibroblast growth factor (FGF) family. FGF family members possess broad mitogenic and cell survival activities, and are involved in a variety of biological processes including embryonic development cell growth, morphogenesis, tissue repair, tumor growth and invasion. This growth factor is a high affinity, heparin dependent ligand for FGFR4. Expression of this gene was detected only in fetal but not adult brain tissue. Synergistic interaction of the chick homolog and Wnt-8c has been shown to be required for initiation of inner ear development. The orthologous protein in mouse is FGF15, which shares about 50% amino acid identity and has similar functions. Together they are often referred to as FGF15/19. FGF19 has important roles as a hormone produced in the ileum in response to bile acid absorption. Bile acids bind to the farnesoid X receptor (FXR), stimulating FGF19 transcription. Several FXR / bile acid response elements have been identified in the FGF19 gene. Human FGF19 transcripts have been shown to be stimulated approximately 300-fold by physiological concentrations of bile acids including chenodeoxycholic acid, glycochenodeoxycholic acid and obeticholic acid in explants of ileal mucosa. FGF19 regulates new bile acid synthesis, acting through the FGFR4/Klotho-β receptor complexes in the liver to inhibit CYP7A1. FGF19 also has metabolic effects, affecting glucose and lipid metabolism when used in experimental mouse models.
The Southern Oscillation is the atmospheric component of ENSO. This component is an oscillation in surface air pressure between the tropical eastern and the western Pacific Ocean waters. The strength of the Southern Oscillation is measured by the Southern Oscillation Index (SOI). The SOI is computed from fluctuations in the surface air pressure difference between Tahiti (in the Pacific) and Darwin, Australia (on the Indian Ocean). El Niño episodes have negative SOI, meaning there is lower pressure over Tahiti and higher pressure in Darwin. La Niña episodes on the other hand have positive SOI, meaning there is higher pressure in Tahiti and lower in Darwin. Low atmospheric pressure tends to occur over warm water and high pressure occurs over cold water, in part because of deep convection over the warm water. El Niño episodes are defined as sustained warming of the central and eastern tropical Pacific Ocean, thus resulting in a decrease in the strength of the Pacific trade winds, and a reduction in rainfall over eastern and northern Australia. La Niña episodes are defined as sustained cooling of the central and eastern tropical Pacific Ocean, thus resulting in an increase in the strength of the Pacific trade winds, and the opposite effects in Australia when compared to El Niño. Although the Southern Oscillation Index has a long station record going back to the 1800s, its reliability is limited due to the latitudes of both Darwin and Tahiti being well south of the Equator, so that the surface air pressure at both locations is less directly related to ENSO.
Bone morphogenetic proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Professor Marshall Urist and Professor Hari Reddi discovered their ability to induce the formation of bone and cartilage, BMPs are now considered to constitute a group of pivotal morphogenetic signals, orchestrating tissue architecture throughout the body. The important functioning of BMP signals in physiology is emphasized by the multitude of roles for dysregulated BMP signalling in pathological processes. Cancerous disease often involves misregulation of the BMP signalling system. Absence of BMP signalling is, for instance, an important factor in the progression of colon cancer, and conversely, overactivation of BMP signalling following reflux-induced esophagitis provokes Barrett's esophagus and is thus instrumental in the development of esophageal adenocarcinoma. Recombinant human BMPs (rhBMPs) are used in orthopedic applications such as spinal fusions, nonunions, and oral surgery. rhBMP-2 and rhBMP-7 are Food and Drug Administration (FDA)-approved for some uses. rhBMP-2 causes more overgrown bone than any other BMPs and is widely used off-label.
Sources: en.wikipedia.org
=== Beta counting === Libby's first detector was a Geiger counter of his own design. He converted the carbon in his sample to lamp black (soot) and coated the inner surface of a cylinder with it. This cylinder was inserted into the counter in such a way that the counting wire was inside the sample cylinder, in order that there should be no material between the sample and the wire. Any interposing material would have interfered with the detection of radioactivity, since the beta particles emitted by decaying 14C are so weak that half are stopped by a 0.01 mm thickness of aluminium. Libby's method was soon superseded by gas proportional counters, which were less affected by bomb carbon (the additional 14C created by nuclear weapons testing). These counters record bursts of ionization caused by the beta particles emitted by the decaying 14C atoms; the bursts are proportional to the energy of the particle, so other sources of ionization, such as background radiation, can be identified and ignored. The counters are surrounded by lead or steel shielding, to eliminate background radiation and to reduce the incidence of cosmic rays. In addition, anticoincidence detectors are used; these record events outside the counter and any event recorded simultaneously both inside and outside the counter is regarded as an extraneous event and ignored.
In 1979, a possible association between autism and opioids was proposed, it was noted that injecting small amounts of opiates into young laboratory animals resulted in symptoms similar to those seen in autistic children. The possibility of a relationship between autism and the consumption of gluten and casein was first articulated by Kalle Reichelt in 1991. Opiate theory hypothesizes that autism is the result of a metabolic disorder in which opioid peptides gliadorphin (aka gluteomorphin) and Casomorphin, produced through metabolism of gluten (present in wheat and related cereals) and casein (present in dairy products), pass through an abnormally permeable intestinal wall and then proceed to exert an effect on neurotransmission through binding with opioid receptors. It has been postulated that the resulting excess of opioids affects brain maturation and causes autistic symptoms including: behavioral difficulties, attention problems, and alterations in communicative capacity and social and cognitive functioning. Although high levels of these opioids are eliminated in the urine, it has been suggested that a small part of them cross into the brain causing interference of signal transmission and disruption of normal activity. Three studies have reported that urine samples of people with autism show an increased 24-hour peptide excretion. A study with a control group found no appreciable differences in opioid levels in urine samples of people with autism compared to controls. Two studies showed an increased opioid levels in cerebrospinal fluid of people with autism.
Griffith's work was largely ignored by the engineering community until the early 1950s. The reasons for this appear to be (a) in the actual structural materials the level of energy needed to cause fracture is orders of magnitude higher than the corresponding surface energy, and (b) in structural materials there are always some inelastic deformations around the crack front that would make the assumption of linear elastic medium with infinite stresses at the crack tip highly unrealistic.
=== Corruption === "Oil rents" have been described as connected with corruption in political literature. A 2011 study suggests that increases in oil rents increased corruption in countries with heavy government involvement in the production of oil. The study found that increases in oil rents "significantly deteriorates political rights". The investigators say that oil exploitation gave politicians "an incentive to extend civil liberties but reduce political rights in the presence of oil windfalls to evade redistribution and conflict".
Sources: en.wikipedia.org
Solid peptide is best kept frozen at about minus 20 degrees Celsius in a sealed container with desiccant. It should be allowed to reach room temperature before opening to prevent condensation. Repeated warming and cooling of the same vial is discouraged.
Reversed-phase liquid chromatography establishes purity, while mass spectrometry confirms molecular mass. The two techniques are normally used together. Retention time alone is not sufficient evidence of identity.
Different counterions change the mass per unit of peptide and can shift chromatographic behavior. Two samples of equal stated purity may therefore not be directly comparable. Reports should specify the counterion whenever quantitative comparisons are made.
一般不建议常温长期保存。多数说明指向 -20 °C 冷冻避光。常温运输通常被视为短期可接受，但会加快降解风险。