The short version of reversed-phase HPLC fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-10-25 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.
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.
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.
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.
| 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 |
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.
The C-terminal Pro-Gly-Pro extension is not incidental. Proline-rich tails are known to resist several common peptidases, and the published literature attributes the longer half-life of Semax, relative to unmodified ACTH fragments, to this feature. The modification also removes the melanocyte-stimulating and corticosteroidogenic activity that characterizes longer ACTH-derived sequences. Because the molecule is small and hydrophilic, it is typically formulated as an aqueous solution for intranasal or parenteral delivery. Acetylation or amidation at the termini appears in closely related research peptides and shifts the mass by a fixed increment.
Reported pharmacological work centers on neurotrophic signaling, including changes in BDNF and NGF expression in hippocampal tissue in animal models. Human data come largely from studies conducted in Russia, and how well those results generalize to other populations remains an open question. Regulatory status differs sharply by jurisdiction: Semax is a registered prescription medicine in Russia, while it holds no approved marketing status in the United States or the European Union. Outside such jurisdictions it is generally handled as a research chemical, which affects both documentation and quality expectations.
Semax is a synthetic heptapeptide whose sequence is Met-Glu-His-Phe-Pro-Gly-Pro. It was developed as a fragment analog of adrenocorticotropic hormone, modeled specifically on the ACTH(4-10) region. The first four residues reproduce that fragment, while a Pro-Gly-Pro tripeptide is appended at the C-terminus. Work on the compound originated in Russia, where it entered clinical use as an intranasal preparation. Its sequence places it among short regulatory peptides studied for effects on the central nervous system rather than on the adrenal axis.
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.
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.
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。
Agrobacterium tumefaciens is the causal agent of crown gall disease (the formation of tumours) in over 140 species of eudicots. It is a rod-shaped, Gram-negative soil bacterium. Symptoms are caused by the insertion of a small segment of DNA (known as T-DNA, for 'transfer DNA', not to be confused with tRNA that transfers amino acids during protein synthesis), from a plasmid into the plant cell, which is incorporated at a semi-random location into the plant genome. Plant genomes can be engineered by use of Agrobacterium for the delivery of sequences hosted in T-DNA binary vectors. Agrobacterium tumefaciens is an Alphaproteobacterium of the family Rhizobiaceae, which includes the nitrogen-fixing legume symbionts. Unlike the nitrogen-fixing symbionts, tumor-producing Agrobacterium species are pathogenic and do not benefit the plant. The wide variety of plants affected by Agrobacterium makes it of great concern to the agriculture industry. Economically, A. tumefaciens is a serious pathogen of walnuts, grape vines, stone fruits, nut trees, sugar beets, horseradish, and rhubarb, and the persistent nature of the tumors or galls caused by the disease make it particularly harmful for perennial crops. Agrobacterium tumefaciens grows optimally at 28 °C (82 °F). The doubling time can range from 2.5–4h depending on the media, culture format, and level of aeration. At temperatures above 30 °C (86 °F), A. tumefaciens begins to experience heat shock which is likely to result in errors in cell division.
== Side effects == Drinking alcohol while taking tinidazole causes an unpleasant disulfiram-like reaction, which includes nausea, vomiting, headache, increased blood pressure, flushing, and shortness of breath.
== Structural classifications of proteins == Protein structures can be grouped based on their structural similarity, topological class or a common evolutionary origin. The Structural Classification of Proteins database and CATH database provide two different structural classifications of proteins. When the structural similarity is large the two proteins have possibly diverged from a common ancestor, and shared structure between proteins is considered evidence of homology. Structure similarity can then be used to group proteins together into protein superfamilies. If shared structure is significant but the fraction shared is small, the fragment shared may be the consequence of a more dramatic evolutionary event such as horizontal gene transfer, and joining proteins sharing these fragments into protein superfamilies is no longer justified. Topology of a protein can be used to classify proteins as well. Knot theory and circuit topology are two topology frameworks developed for classification of protein folds based on chain crossing and intrachain contacts respectively.
=== SELDI-TOF-MS === Samples spotted on a SELDI surface are typically analyzed using time-of-flight mass spectrometry. An irradiating laser ionizes peptides from crystals of the sample/matrix mixture. The matrix absorbs the energy of the laser pulse, preventing destruction of the molecule, and transfers charge to the sample molecules, forming ions. The ions are then briefly accelerated through an electric potential and travel down a field-free flight tube where they are separated by their velocity differences. The mass-to-charge ratio of each ion can be determined from the length of the tube, the kinetic energy given to ions by the electric field, and the velocity of the ions in the tube. The velocity of the ions is inversely proportional to the square root of the mass-to-charge ratio of the ion; ions with low mass-to-charge ratios are detected earlier than ions with high mass-to-charge ratios.
== Further reading == Sigel, Roland K. O.; Skilandat, Miriam; Sigel, Astrid; Operschall, Bert P.; Sigel, Helmut (2013). "Chapter 8. Complex formation of cadmium with sugar residues, nucleobases, phosphates, nucleotides and nucleic acids". In Sigel, Astrid; Sigel, Helmut; Sigel, Roland K. O. (eds.). Cadmium: From Toxicology to Essentiality (PDF). Metal Ions in Life Sciences. Vol. 11. Springer. pp. 191–274. doi:10.1007/978-94-007-5179-8_8. ISBN 978-94-007-5178-1. PMID 23430775. Sóvágó, Imre; Várnagy, Katalin (2013). "Chapter 9. Cadmium(II) complexes of amino acids and peptides". In Sigel, Astrid; Sigel, Helmut; Sigel, Roland K. O. (eds.). Cadmium: From Toxicology to Essentiality. Metal Ions in Life Sciences. Vol. 11. Springer. pp. 275–302. doi:10.1007/978-94-007-5179-8_9. ISBN 978-94-007-5178-1. PMID 23430776. Yatsimirsky, Konstantin Borisovich; Vasilyev, Vladimir Pavlovich (1960). Instability Constants of Complex Compounds. Translated by Patterson, D. A. OUP.
Sources: en.wikipedia.org
== Selecting discriminatory peptides == Finally, sophisticated normalization methods are used to remove systematic artefacts in the peptide intensity values between LC-MS measurements. Then, discriminatory peptides are identified by selecting the peptides whose normalized intensities are different (e.g., p-value < 0.05) among multiple groups of samples. In addition, newer hybrid mass spectrometers like LTQ OrbiTrap offer the possibility to acquire MS/MS peptide identifications in parallel to the high mass precision measurement of peptides on the MS1 level. This raises the computational challenge for the processing and integration of these two sources of information and has led to the development of novel promising quantification strategies.
Inkjet (dot on demand or continuous) systems are capable of printing high resolution (300 dpi or higher for dot on demand) images at press speed (up to 1000fpm). These solutions can be deployed either on-press or off-line. Laser marking can be employed to ablate a coating or to cause a color change in certain materials. The advantage of laser is fine detail and high speed for character printing, and no consumables. Not all substrates accept a laser mark, and certain colors (e.g. red) are not suitable for barcode reading. Thermal Transfer and Direct Thermal. For lower speed off-press applications, thermal transfer and direct thermal printers are ideal for printing variable data on labels. Software systems are available for managing traceability throughout the entire production, processing, marketing and distribution system. Some of these software systems combine multiple software modules allowing the producer to capture traceability information from all farming, processing and packing activities. Others, capture data in the field and packing operations to integrate with retail buying platforms and carry data all the way to the end consumer. Leveraging new advancements in mobile technology, food brands are now incorporating mobile messaging and QR codes on product labels. Consumers can text or scan the barcode with smartphones for immediate retrieval of product information. Consumers can also trace the origins of their purchased produce at websites.
In season four, she starts working as a receptionist at the Luncheonette, her uncles' recording studio. At her cousin Victor Graham's baseball game, she meets Ryan York, a young Afghanistan war veteran. The two start a relationship and are shown to be fairly steady for several episodes. However, after a heated argument about his drinking habits and poor decision-making, Amber breaks up with Ryan because he reminds her too much of her own father, who abandoned her family prior to the series. The two reconcile in the fourth-season finale and are shown to be very happy. In the first episode of season five, Ryan proposes to Amber after he returns from a third tour of duty in Afghanistan. She accepts the proposal. He buys her a very expensive engagement ring that she is uncomfortable accepting since he used all his money from the army to purchase it. This leads to tension between the couple. Ryan becomes upset when he feels as though a member of the band that the Luncheonette is recording is flirting with Amber, and when he picks her up from a bar, he gets into a fight with one of the guys, leading to his being arrested. The band decides not to press charges, but Amber is not sure where their relationship stands, especially after Crosby and Adam ask that Ryan not come around the Luncheonette for a while. After a talk with her grandfather, she tells Ryan that she loves him and wants to work through things and have a family with him. However, he tells her that he has reenlisted in the army. He ends their engagement, which leads to Amber going on a bender.
==== Stages of genital development ==== The first stage occurs roughly four weeks before the spider's final molt. Unlike adult males, young males possess a broad tarsus that does not appear to consist of any internal structures or appendages. Their pedipalps are greatly bent at a joint connecting the between the tibia and patella. The testes at this point in the young male's life appear very similar to those of the adult males both in terms of physical structure and presence of all stages of spermatogenesis. This spermatogenesis takes place in cysts which contain spermatids. During this time, there is very little observable secretory activity in the testes. In a similar manner to the adult genital system, the vas deferens in young males is connected to the distal, thin part of the testis. The distal portion of the vas deferens is incredibly narrow and is not characterized by the presence of spermatozoa or other secretions. On the other hand, the proximal region consists of a thick epithelium and intricate luminal region containing spermatozoa. The second stage of development is observed two weeks prior the spider's final molt. At this point, the pedipalps of the spider are only partially bent, and the internal structures of the tarsus can be seen. The testes are dimensionally very similar to those of subadult stage one males and adult males. The distal portion of the vas deferens becomes thinner and twists in a tube-like shape. Spermatozoa and other secretions are extensively present in proximal portion of the vas deferens.
=== Disease control intervention === Due to the suspicions that food markets could have played a role in the emergence of COVID-19, a group of US lawmakers, NIAID director Anthony Fauci, UNEP biodiversity chief Elizabeth Maruma Mrema, and CBCGDF secretary general Zhou Jinfeng called in April 2020 for the global closure of wildlife markets due to the potential for zoonotic diseases and risk to endangered species. In April 2021, the World Health Organization called for a total ban on the sale of live animals in food markets in order to prevent future pandemics. Planetary health studies have called for disease control intervention measures, in lieu of outlawing live-animal markets, to be implemented in markets. These include proposals for "standardised global monitoring of water, sanitation, and hygiene (WASH) conditions", which the World Health Organization announced in April 2020 that it was developing as requirements for markets to open. Other proposals include less homogeneous policies that are specialized for local social, cultural, and financial factors, as well as new proposed rapid assessment tools for monitoring the hygiene and biosecurity of live animal stalls in markets.
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.
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.