mass spectrometry is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2025-12-14. Where a claim depends on a specific study, the study is described rather than over-claimed.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue with a C-terminal Pro-Gly-Pro tail |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Abbreviated TKPRPGP in most catalogues |
| Molecular mass | About 752 Da | Value for the free peptide |
| Solubility | Freely soluble in water | Aqueous solutions are kept cold and used promptly |
| Typical storage | -20 °C, dry, protected from light | Applies to the lyophilised powder before reconstitution |
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
===== Submitted by South Korea (inscribed 2013) ===== Kimjang, the tradition of making and sharing kimchi that usually takes place in late autumn, was added to the list as "Gimjang, making and sharing kimchi in the Republic of Korea". The practice of Gimjang reaffirms Korean identity and strengthens family cooperation. Gimjang is also an important reminder for many Koreans that human communities need to live in harmony with nature.
== The Strep-tag principle == Just like other short-affinity tags (His-tag, FLAG-tag), the Strep-tag can be easily fused to recombinant proteins during subcloning of its cDNA or gene. For its expression, various vectors for various host organisms (E. coli, yeast, insect, and mammalian cells) are available. A particular benefit of the Strep-tag is its rather small size and the fact that it is biochemically almost inert. Therefore, protein folding or secretion is not influenced and usually it does not interfere with protein function. Strep-tag is especially suited for analysis of functional proteins, because the purification procedure can be kept under physiological conditions. This not only allows the isolation of sensitive proteins in a native state, but it is also possible to purify intact protein complexes, even if just one subunit carries the tag. In the first step of the Strep-tag purification cycle, the cell lysate containing Strep-tag fusion protein is applied to a column with immobilized Strep-Tactin (step 1). After the tagged protein has specifically bound to Strep-Tactin, a short washing step with a physiological buffer (e.g. phosphate buffered saline, PBS) removes all other host proteins (step 2). This is due to Strep-Tactin's low tendency to bind proteins non specifically. Then, the purified Strep-tag fusion protein is gently eluted with a low concentration of desthiobiotin, which specifically competes for the biotin binding pocket (step 3). To regenerate the column, desthiobiotin is removed by application of a HABA containing solution (a yellow azo dye).
=== GDGT-1 – GDGT-4 === GDGT-1, GDGT-2, and GDGT-3 have one, two, and three cyclopentane rings respectively within their isoprenoid biphytane carbon structures, respectively. Nitrososphaerota are the largest producers of these groups in marine and lacustrine environments. Methanogens are not thought to be large synthesizers of these molecules, with the exception of Methanopyrus kandleri, which does produce them. These classes are lower in abundance than GDGT-0 and GDGRT-4. They are used in the TEX86 paleothermometer. GDGT-4 refers to the version with four cyclopentane rings. It is quite abundant (although not easy to differentiate from crenarchaeol on GC/MS, see below). Nitrososphaerota also makes GDGT-4.
So it was proposed that succinyl amino acid derivative should be an ACE inhibitor and succinyl-L-proline was found to be such an inhibitor. It was also known that the nature of penultimate amino acid residue of a peptide substrate for ACE influences binding to the enzyme. The acyl group of the carboxyalkanoyl amino acid binds the zinc ion of the enzyme and occupies the same position at the active site of ACE as the penultimate. Therefore, the substituent of the acyl group might also influence binding to the enzyme. A 2-methyl substituent with D configuration was found to enhance the inhibitory potency by about 15 fold of succinyl-L-proline. Then the search for a better zinc-binding group started. Replacement of the succinyl carboxyl group by nitrogen-containing functionalities (amine, amide or guanidine) did not enhance inhibitory activity. However a potency breakthrough was achieved by the replacement of the carboxyl group with a sulfhydryl function (SH), a group with greater affinity for the enzyme bound zinc ion. This yielded a potent inhibitor that was 1000 times more potent than succinyl-L-proline. The optimal acyl chain length for mercaptoalkanoyl derivates of proline was found to be 3-mercaptopropanoyl-L-proline, 5 times greater than that of 2-mercaptoalkanoyl derivates and 50 times greater than that of 4-mercaptoalkanoyl derivates. So the D-3-mercapto-2-methylpropanoyl-L-proline or Captopril was the most potent inhibitor.
== Human blood plasma == Blood plasma is the liquid component of blood, which contains dissolved proteins, nutrients, ions, and other soluble components. In whole blood, red blood cells, white blood cells, and platelets are suspended within the plasma. The goal of plasma purification and processing is to extract specific materials that are present in blood, and use them for restoration and repair. There are several components that make up blood plasma, one of which is the protein albumin. Albumin is a highly water-soluble protein with considerable structural stability. It serves as a transportation device for materials such as hormones, enzymes, fatty acids, metal ions, and medicinal products. It is also used for therapeutic purposes, being essential in restoration and maintenance of circulating blood volume in imperative situations such as severe trauma or surgery. With little room for error, extremely pure samples that are lacking impurities needs to be at hand in good amount. Human blood plasma is important for the body so the nutrients etc. can be stored.
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Greenland (territory of Denmark): Prime Minister Jens-Frederik Nielsen firmly stated that it would be "not respectful" to compare the democratic institutions in Greenland to those in Venezuela, stating that the reasons for another "overnight takeover" were not the same, and called on more direct communication to be had with the United States amid the proposed US acquisition of the territory. Honduras: Outgoing President Xiomara Castro strongly condemned what she described as an act of kidnapping by the United States, calling the events "an affront to the sovereignty and independence of the peoples of Latin America and the Caribbean." President Castro declared that Honduras stands "in solidarity with the brave people of Venezuela, and with President Nicolás Maduro and his wife". Jamaica: As a member of the Bureau of the Conference of Heads of Government of the Caribbean Community, Jamaica joined a statement issued following the U.S. military action that reaffirmed the principles of international law, state sovereignty and territorial integrity, and called for peaceful dialogue through diplomatic channels. Mexico: President Claudia Sheinbaum "strongly condemns and rejects" the US military action, stating that the strikes breached the United Nations Charter. She urged the US to comply with international law and end "all acts of aggression" against the Venezuelan government and people. Nicaragua: The Nicaraguan government condemned the strikes, claiming that peace in Venezuela was "gravely hurt" and called for Maduro's release.
Although narcotics are illegal in the US, they have become integrated into the nation's culture and are seen as a recreational activity by sections of the population. Illicit drugs are considered to be a commodity with strong demand, as they are typically sold at a high value. This high price is caused by a combination of factors that include the potential legal ramifications that exist for suppliers of illicit drugs and their high demand. Despite the constant effort by politicians to win the war on drugs, the US is still the world's largest importer of illegal drugs. Throughout the 20th century, narcotics other than cocaine also crossed the Mexican border, meeting the US demand for alcohol during the 1920s Prohibition, opiates in the 1940s, marijuana in the 1960s, and heroin in the 1970s. Most of the US imports of drugs come from Mexican drug cartels. In the United States, around 195 cities have been infiltrated by drug trafficking that originated in Mexico. An estimated $10bn of the Mexican drug cartel's profits come from the United States, not only supplying the Mexican drug cartels with the profit necessary for survival, but also furthering America's economic dependence on drugs.
== History == The physical principles of ion traps were first explored by F. M. Penning, who observed that electrons released by the cathode of an ionization vacuum gauge follow a long cycloidal path to the anode in the presence of a sufficiently strong magnetic field. Later Wolfgang Paul developed a method to trap ions without magnetic fields that was based on his work with quadrupole mass spectrometers. Ion traps were used in television receivers prior to the introduction of aluminized CRT faces around 1958, to protect the phosphor screen from ions. The ion trap must be delicately adjusted for maximum brightness.
Dextromethorphan/bupropion, sold under the brand name Auvelity, is a combination medication for the treatment of major depressive disorder (MDD) and agitation associated with dementia due to Alzheimer's disease. Its active components are dextromethorphan (DXM) and bupropion. It is taken as a tablet by mouth. Side effects of dextromethorphan/bupropion include dizziness, headache, diarrhea, somnolence, dry mouth, sexual dysfunction, and hyperhidrosis, among others. The mechanism of action of dextromethorphan/bupropion in the treatment of depression is unknown. Dextromethorphan/bupropion was developed by Axsome Therapeutics and was approved for the treatment of major depressive disorder in the United States in August 2022.
Like all sugar compounds, honey caramelizes if heated sufficiently, becoming darker in color, and eventually burns. However, honey contains fructose, which caramelizes at lower temperatures than glucose. The temperature at which caramelization begins varies, depending on the composition, but is typically between 70 and 110 °C (158 and 230 °F). Honey also contains acids, which act as catalysts for caramelization. The specific types of acids and their amounts play a primary role in determining the exact temperature. Of these acids, the amino acids, which occur in very small amounts, play an important role in the darkening of honey. The amino acids form darkened compounds called melanoidins, during a Maillard reaction. The Maillard reaction occurs slowly at room temperature, taking from a few to several months to show visible darkening, but speeds up dramatically with increasing temperatures. However, the reaction can also be slowed by storing the honey at colder temperatures. Unlike many other liquids, honey has very poor thermal conductivity of 0.5 W/(m⋅K) at 13% water content (compared to 401 W/(m⋅K) of copper), taking a long time to reach thermal equilibrium. Due to its high kinematic viscosity honey does not transfer heat through momentum diffusion (convection) but rather through thermal diffusion (more like a solid), so melting crystallized honey can easily result in localized caramelization if the heat source is too hot or not evenly distributed. However, honey takes substantially longer to liquefy when just above the melting point than at elevated temperatures.
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Architecturally, all Chipotle restaurants are built using most of the same material finishes (plywood, corrugated metal, stainless steel, exposed ductwork), although each store is unique. The interiors have been described as having an "industrial, sheet metal look". Chipotle has built restaurants using white ceramic tile instead of stainless steel. It costs the company approximately $850,000 to open a new restaurant. When the first Chipotle opened, Steve Ells asked his friend, sculptor Bruce Gueswel, to design the chairs and a styled Mayan king whose face was loosely based on that of civil rights movement leader Martin Luther King Jr., a personal inspiration of Gueswel, for the restaurant. Both items were made from wood and metal. Gueswel has continued to design and build the art and chairs for all subsequent Chipotle restaurants. Most Chipotle locations display a photograph of the original restaurant, which is near the University of Denver campus on Evans Avenue. Instead of a photograph of itself, the original location has a photograph of the Dolly Madison Ice Cream that previously occupied the location. In 2010, Chipotle began opening smaller concept locations that have lower costs of development and occupancy. Chipotle has made arrangements to add solar panels to 75 of its restaurants. Chipotle was the defendant in a lawsuit for failure to comply with the Americans with Disabilities Act (ADA). Maurizio Antoninetti, a customer who used a wheelchair, claimed he was denied the "Chipotle Experience", because he was unable to see the food preparation.
Kyowa Kirin Co., Ltd. (協和キリン株式会社, Kyōwa Kirin Kabushiki Kaisha) is a Japanese pharmaceutical and biotechnology company under the Kirin Holdings, and was among the 40 largest in the world by revenue in 2012. The company is headquartered in Chiyoda-ku, Tokyo and is a member of the Nikkei 225 stock index.
=== Roles in endocrine regulation === Decreases basal corticotropin level and blocks its release. Stimulates release of luteinizing hormone (LH). Stimulates release of somatoliberin and somatotrophin secretion and inhibits somatostatin secretion.
Some crashed on flight decks, but the majority ditched into the sea. Some pilots intentionally went down in groups to facilitate rescue, and more ditched individually either in a controlled landing with a few gallons of fuel left or in a crash after their engines ran dry. Approximately three-quarters of the crews were rescued from the sea, either that night from crash locations within the task forces, or over the next few days for those further out, as search planes and destroyers criss-crossed the ocean looking for them.
Sources: en.wikipedia.org
Selank is a seven-amino-acid peptide built from the tuftsin sequence plus a Pro-Gly-Pro tail. It is produced by chemical synthesis rather than extracted from a natural source. The free peptide is usually supplied as a lyophilised powder or in an aqueous formulation.
Tuftsin is a natural tetrapeptide derived from the Fc portion of immunoglobulin G. Selank retains that tetrapeptide at its N-terminus and adds three residues to improve resistance to enzymatic breakdown. The relationship is structural, and the two molecules are not interchangeable in experimental work.
It holds a product registration in Russia for intranasal use as an anxiolytic. Registrations of that kind are not automatically accepted by regulators elsewhere. In most other countries it is treated as an unapproved substance or a research material.
The most common approach combines reverse-phase liquid chromatography with mass spectrometry. Chromatography separates the components while mass spectrometry confirms the molecular mass. Peptide sequencing or tandem mass analysis can further verify the amino acid order.