intranasal delivery comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-10-05. Numbers and descriptions here follow the published literature rather than marketing material.
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 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.
Semax 是一种人工合成的七肽，氨基酸序列为 Met-Glu-His-Phe-Pro-Gly-Pro，单字母缩写记作 MEHFPGP。它被归类为促肾上腺皮质激素片段 ACTH(4-10) 的结构类似物，但并不天然存在于生物体内。母体片段 ACTH(4-10) 的序列为 Met-Glu-His-Phe-Arg-Trp-Gly，Semax 替换了中间两个残基，并在羧基端延长了 Pro-Gly-Pro 三肽。这种延长被普遍认为能提升分子对肽酶的耐受性。
该化合物于二十世纪八十年代在俄罗斯被开发，相关工作由俄罗斯科学院分子遗传学研究所的研究团队主导。开发目标并非复制 ACTH 的完整激素活性，而是寻找保留其神经作用方向、同时去除促肾上腺皮质激素释放效应的短肽片段。研究记录显示，这一方向促成了多个相关短肽的合成与筛选，而 Semax 是其中被研究最广泛的一个。当地文献常以 Семакс 这一名称指代它。
研究兴趣主要集中在神经营养因子相关的路径上，包括脑源性神经营养因子与神经生长因子的表达变化。部分实验报告称在特定条件下观察到这些因子的水平上升，但具体信号通路和剂量依赖关系仍未完全厘清。多数公开数据来自细胞模型和动物实验，人体对照研究数量有限。因此，该化合物的作用机制在文献中属于活跃讨论，而非已经确立的定论。
| 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 |
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.
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。
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。
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.
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.
Brain failure after clinical death is now known to be due to a complex series of processes called reperfusion injury that occur after blood circulation has been restored, especially processes that interfere with blood circulation during the recovery period. Control of these processes is the subject of ongoing research. In 1990, the laboratory of resuscitation pioneer Peter Safar discovered that reducing body temperature by three degrees Celsius after restarting blood circulation could double the time window of recovery from clinical death without brain damage from 5 minutes to 10 minutes. This induced hypothermia technique is beginning to be used in emergency medicine. The combination of mildly reducing body temperature, reducing blood cell concentration, and increasing blood pressure after resuscitation was found especially effective – allowing for recovery of dogs after 12 minutes of clinical death at normal body temperature with practically no brain injury. The addition of a drug treatment protocol has been reported to allow recovery of dogs after 16 minutes of clinical death at normal body temperature with no lasting brain injury. Cooling treatment alone has permitted recovery after 17 minutes of clinical death at normal temperature, but with brain injury. Under laboratory conditions at normal body temperature, the longest period of clinical death of a cat (after complete circulatory arrest) survived with eventual return of brain function is one hour.
The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The phosphate group and the sugar of each form nucleotide bonds to form the backbone of the nucleic acid, while the sequence of nitrogenous bases stores the information. The most common nitrogenous bases are adenine, cytosine, guanine, thymine, and uracil. The nitrogenous bases of each strand of a nucleic acid will form hydrogen bonds with a specific partner base in a complementary strand of nucleic acid. Adenine binds with thymine or uracil, and cytosine and guanine bind one another. Adenine, thymine, and uracil form two hydrogen bonds, while cytosine and guanine form three. Aside from the genetic material of the cell, nucleic acids often play a role as second messengers, as well as forming the base molecule for adenosine triphosphate (ATP), the primary energy-carrier molecule found in all living organisms. Other nucleotides besides adenosine can also be found forming other, less common, energy-carrying molecules such as guanosine in GTP or uracil in UTP. Also, while adenine, cytosine, and guanine occur in both RNA and DNA, thymine occurs only in DNA and uracil occurs in RNA.
Prolidase deficiency (PD) is an extremely uncommon autosomal recessive disorder associated with collagen metabolism that affects connective tissues and thus a diverse array of organ systems more broadly, though it is extremely inconsistent in its expression. Collagen is a structural protein found i.a. in bone, skin and connective tissues that is broken down into iminodipeptides at the end of its lifecycle. Of these dipeptides, those containing C-terminal proline or hydroxyproline would normally be broken down further by the enzyme Prolidase, recovering and thus recycling the constituent amino acids. Due to a genetic defect, prolidase activity in individuals with PD is either knocked out or severely reduced. Those affected therefore eliminate excessive amounts of iminodipeptides in their urine, wasting this precious resource, with debilitating effects.
Sources: en.wikipedia.org
There is no international consensus on whether the death penalty should be abolished. Each country has the sovereign right to decide on its own judicial system, taking into account its own circumstances. The death penalty has been effective in keeping Singapore one of the safest places in the world to work and live in. The application of the death penalty is only reserved for "very serious crimes". The Ministry of Home Affairs also refuted Amnesty International's claims of the majority of the executed being foreigners, and that it was "mostly the poor, least educated, and vulnerable people who are executed". The Ministry stated: "Singaporeans, and not foreigners, were the majority of those executed... Of those executed from 1993 to 2003, 95% were above 21 years of age, and 80% had received formal education. About 80% of those who had been sentenced to capital punishment had employment before their convictions." Following the hanging of Van Tuong Nguyen in 2005, Prime Minister Lee Hsien Loong reiterated the government's position, stating that "The evil inflicted on thousands of people with drug trafficking demands that we must tackle the source by punishing the traffickers rather than trying to pick up the pieces afterwards... It's a law which is approved of by Singapore's inhabitants and which allows us to reduce the drug problem." In October 2020, Law Minister K. Shanmugam emphasised that the death penalty is a powerful deterrent to capital crimes in Singapore.
=== McClintock's work on maize === Barbara McClintock began her career as a maize cytogeneticist. In 1931, McClintock and Harriet Creighton demonstrated that cytological recombination of marked chromosomes correlated with recombination of genetic traits (genes). McClintock, while at the Carnegie Institution, continued previous studies on the mechanisms of chromosome breakage and fusion flare in maize. She identified a particular chromosome breakage event that always occurred at the same locus on maize chromosome 9, which she named the "Ds" or "dissociation" locus. McClintock continued her career in cytogenetics studying the mechanics and inheritance of broken and ring (circular) chromosomes of maize. During her cytogenetic work, McClintock discovered transposons, a find which eventually led to her Nobel Prize in 1983.
This spectrometer may consist of magnetic or electric sectors, and so-called velocity selectors, which utilizes both electric fields and magnetic fields. After this stage, no background is left, unless a stable (atomic) isobar forming negative ions exists (e.g. 36S if measuring 36Cl), which is not suppressed at all by the setup described so far. Thanks to the high energy of the ions, these can be separated by methods borrowed from nuclear physics, like degrader foils and gas-filled magnets. Individual ions are finally detected by single-ion counting (with silicon surface-barrier detectors, ionization chambers, and/or time-of-flight telescopes). Thanks to the high energy of the ions, these detectors can provide additional identification of background isobars by nuclear-charge determination.
Most drugs were discovered by empirical means, including observation, accident, and trial and error. One famous example is the discovery of penicillin, the first antibiotic in the world. The substance was discovered by Alexander Fleming in 1928 after a combination of unanticipated events occurred in his laboratory during his summer vacation. The Penicillium mold on the petri dish was believed to secrete a substance (later named "penicillin") that inhibited bacterial growth. Large pharmaceutical companies then started to establish their microbiological departments and search for new antibiotics. The screening program for antimicrobial compounds also led to the discovery of drugs with other pharmacological properties, such as immunosuppressants like Cyclosporin A.The discovery of penicillin was a serendipitous (i.e. chance) discovery. Another, more advanced approach to drug discovery is rational drug design. The method is underpinned by an understanding of the biological targets of the drugs, including enzymes, receptors, and other proteins. In the late 19th century, Paul Ehrlich observed the selective affinity of dyes for different tissues and proposed the existence of chemoreceptors in our bodies. Receptors were believed to be the specific binding sites for drugs. The drug-receptor recognition was described as a key-and-lock interplay by Emil Fischer in the early 1890s. It was later found that the receptors can either be stimulated or inhibited by chemotherapeutic agents to attain the desired physiological response.
Sources: en.wikipedia.org
== D == Dendrite A branched projection of a neuron that receives synaptic input from other neurons and transmits electrical signals toward the cell body. Dendritic spine A small, membranous protrusion from a neuron's dendrite that typically receives input from a single synapse of an axon. Spines are key sites for synaptic strength and plasticity. Depolarization A change in membrane potential that makes the interior of a neuron more positive relative to the outside, often initiating an action potential if a threshold is reached. Descending neuron A neuron that originates in the brain or brainstem and projects downward through the spinal cord to influence motor circuits and autonomic function. Descending neurons are critical for voluntary movement, postural control, and reflex modulation. Major descending pathways include the corticospinal, reticulospinal, rubrospinal, and vestibulospinal tracts. Developmental neuroscience A branch of neuroscience focused on how the nervous system develops from embryonic stages through adulthood, including neurogenesis, synaptogenesis, and pruning. Diffusion tensor imaging (DTI) A form of magnetic resonance imaging that maps the diffusion of water molecules in brain tissue to visualize white matter tracts and structural connectivity. Diencephalon A region of the forebrain that includes structures such as the thalamus and hypothalamus. It plays a role in sensory relay, autonomic function, and endocrine regulation.
==== Fidelity ==== Unlike the proofreading mechanisms of DNA polymerase those of RNAP have only recently been investigated. Proofreading begins with separation of the mis-incorporated nucleotide from the DNA template. This pauses transcription. The polymerase then backtracks by one position and cleaves the dinucleotide that contains the mismatched nucleotide. In the RNA polymerase this occurs at the same active site used for polymerization and is therefore markedly different from the DNA polymerase where proofreading occurs at a distinct nuclease active site. The overall error rate is around 10−4 to 10−6.
=== Safer supply === Safer supply programs prescribe medications (including stimulants, opioids, and benzodiazepines) to people at high risk of overdose. This is meant to provide a safer alternative to an illegal drug supply that contains high levels of fentanyl and other dangerous chemicals. The structure of such programs is more flexible than opioid agonist therapy. The drugs dispensed by these programs can result in intoxication, unlike methadone or buprenorphine. Safer supply projects exist in a number of Canadian cities. Critics of these programs point to the risk of drug diversion and argue that patients should be encouraged to enter drug rehabilitation programs instead of being given drugs.
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.
不是。Semax 是完全人工合成的七肽，自然界中没有对应的已知肽段。它的设计灵感来自促肾上腺皮质激素片段 ACTH(4-10)，但序列经过了替换和延长。