electrospray ionization 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.
Updated 2025-12-11. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| 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 |
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
Pharmacokinetic data are sparse and largely derived from animal work. After intranasal administration the peptide appears in plasma within minutes, and reported half-lives are short, on the order of minutes to tens of minutes. Degradation proceeds through ordinary proteolytic cleavage into constituent amino acids and smaller fragments. Direct evidence that intact Selank reaches brain tissue in meaningful amounts is limited, and the extent of blood-brain barrier penetration is debated. Some authors argue that fragments, not the parent peptide, carry much of the observed activity.
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
=== Pain === Ketamine infusions are used for acute pain treatment in emergency departments and in the perioperative period for individuals with refractory or intractable pain. The doses are lower than those used for anesthesia, usually referred to as sub-anesthetic doses. Adjunctive to morphine or on its own, ketamine reduces morphine use, pain level, nausea, and vomiting after surgery. Ketamine is likely to be most beneficial for surgical patients when severe post-operative pain is expected, and for opioid-tolerant patients. Ketamine is especially useful in the pre-hospital setting due to its effectiveness and low risk of respiratory depression. Ketamine has similar efficacy to opioids in a hospital emergency department setting for the management of acute pain and the control of procedural pain. It may also prevent opioid-induced hyperalgesia and postanesthetic shivering. For chronic pain, ketamine is used as an intravenous analgesic, mainly if the pain is neuropathic. It has the added benefit of counteracting spinal sensitization or wind-up phenomena experienced with chronic pain. In multiple clinical trials, ketamine infusions delivered short-term pain relief in neuropathic pain diagnoses, pain after a traumatic spine injury, fibromyalgia, and complex regional pain syndrome (CRPS).
==== United Kingdom ==== The UK National Health Service (NHS) recommends that people at risk of vitamin D deficiency, breast-fed babies, formula-fed babies taking no more than 500 ml of infant formula a day, and children aged 6 months to 4 years, should take daily vitamin D supplements throughout the year to ensure sufficient intake. This includes people with limited skin synthesis of vitamin D, who are not often outdoors, are frail, housebound, living in a care home, or usually wearing clothes that cover up most of the skin, or with dark skin, such as having an African, African-Caribbean or south Asian background. Other people may be able to make adequate vitamin D from sunlight exposure from April to September. The NHS and Public Health England recommend that everyone, including those who are pregnant and breastfeeding, consider taking a daily supplement containing 10 μg (400 IU) of vitamin D during autumn and winter because of inadequate sunlight for vitamin D synthesis.
Jung identified two primary 'attitudinal types'—introvert and extrovert. While the terms 'introversion' and 'extraversion' had prior use in European thought, Jung was the first to integrate them into a comprehensive structural theory of personality. He redefined these concepts not merely as social traits, but as fundamental directions of psychic energy (libido), establishing the first systematic model of psychological types based on the movement of psychic energy libido toward the subject or the object. In Psychological Types, Jung defined the primary attitudinal types (introvert and extrovert), comparing them to the ancient archetypes: Apollo and Dionysus. The introvert is likened to Apollo, who shines a light on understanding. The introvert is focused on the internal world of reflection, dreaming, and vision. Thoughtful and insightful, the introvert can sometimes be uninterested in joining the activities of others. The introvert's libido flows inwards towards subjective factors and is influenced by 'inner necessity'. By contrast, the extravert is associated with Dionysus, interested in joining the activities of the world. The extravert is focused on the outside world of objects, sensory perception, and action. Energetic and lively, the extravert may lose their sense of self in the intoxication of Dionysian pursuits. For the extravert, the libido flows outwards, and the person has an interest, relationship and dependence on events, people and things. Jung's concepts of introversion and extraversion differ fundamentally from their common usage in modern trait psychology.
Baechu-kimchi (배추김치) spicy napa cabbage kimchi, made from whole cabbage leaves Baechu-geotjeori (배추겉절이) unfermented napa cabbage kimchi Bossam-kimchi (보쌈김치) wrapped kimchi Baek-kimchi (백김치) white kimchi, made without chili pepper Dongchimi (동치미) a non-spicy watery kimchi Nabak-kimchi (나박김치) a mildly spicy watery kimchi Chonggak-kimchi (총각김치) cubed chonggak "ponytail" radish, a popular spicy kimchi Kkakdugi (깍두기) spicy cubed Korean radish strongly-scented kimchi containing fermented shrimp Oi-sobagi (오이소박이) cucumber kimchi that can be stuffed with seafood and chili paste, and is a popular choice during the spring and summer seasons Pa-kimchi (파김치) spicy green onion kimchi Yeolmu-kimchi (열무김치) is also a popular choice during the spring and summer, and is made with yeolmu radishes, and does not necessarily have to be fermented. Gat-kimchi (갓김치), made with Indian mustard Yangbaechu-kimchi (양배추 김치) spicy cabbage kimchi, made from "headed" cabbage leaves (as opposed to napa cabbage) Kimchi from the northern parts of Korea tend to have less salt and red chili and usually do not include brined seafood for seasoning. Northern kimchi often has a watery consistency. Kimchi made in the southern parts of Korea, such as Jeolla Province and Gyeongsang Province, uses salt, chili peppers and myeolchijeot (멸치젓, brined anchovy allowed to ferment) or saeujeot (새우젓, brined shrimp allowed to ferment), myeolchiaekjeot (멸치액젓), anchovy fish sauce, kkanariaekjeot (까나리액젓), liquid anchovy jeot, similar to fish sauce used in Southeast Asia, but thicker.
Sources: en.wikipedia.org
=== BIT Index === The branched:isoprenoid tetraether (BIT) index relates the relative abundances of brGDGTs in a natural sample to the relative abundance of soil organic matter in that sample. It is calculated by ratioing a sum of bacterially-produced brGDGT abundances over a sum of archaeal isoGDGT abundances and is based on the fundamental idea that brGDGTs are produced most commonly in terrestrial environments (most ubiquitous in soils and peats) while archaeal isoGDGTs (particularly crenarchaeol) are produced in marine environments. While caveats and analytical uncertainties remain an issue, the BIT index is a potentially useful proxy for assessing the amount of fluvially transported soil organic matter compared to marine organic matter.
=== Prokaryotic === Predicted serpin genes are sporadically distributed in prokaryotes. In vitro studies on some of these molecules have revealed that they are able to inhibit proteases, and it is suggested that they function as inhibitors in vivo. Several prokaryote serpins are found in extremophiles. Accordingly, and in contrast to mammalian serpins, these molecules possess elevated resistance to heat denaturation. The precise role of most bacterial serpins remains obscure, although Clostridium thermocellum serpin localises to the cellulosome. It is suggested that the role of cellulosome-associated serpins may be to prevent unwanted protease activity against the cellulosome.
=== Opioid liability === Systemic agmatine can potentiate opioid analgesia, and prevent tolerance to chronic morphine in laboratory rodents. Since then, cumulative evidence amply shows that agmatine inhibits opioid dependence and relapse in several animal species.
Sources: en.wikipedia.org
A record in the form of proof of baptisms shall be made, containing the time and hour of birth. An extract from this register may be used to prove the age of majority or minority and will serve as full legal evidence for this purpose. Before this legal requirement, fifteen Parisian parishes already kept baptismal registers, three kept marriage registers, and one kept burial registers. Presided over by Pope Paul III from 1545 to 1563, the Council of Trent also required priests to keep a register of baptisms performed in their parish. The names of godparents had to be included to prevent marriages between people linked by spiritual kinship (e.g., a godfather and his goddaughter could not marry). The council also mandated that marriages, freely contracted before a priest and two or three witnesses, be preceded by the publication of banns and recorded in a designated register. It also advocated for the union of children without requiring parental consent. In May 1579, the Ordinance of Blois extended the obligation to keep marriage and burial registers throughout France. The Ordinance of Saint-Germain-en-Laye of April 1667, known as the "Code Louis," required these registers to be kept in duplicate: the first copy (the minute) remained in the parish, while the duplicate (the grosse) was deposited at the court registry. In Paris, the Châtelet registry preserved the second copy, with the oldest dating back to 1668. By 1790, the capital had around fifty parishes.
The first human to human heart transplantation was performed in 1967 by the South African surgeon Christiaan Barnard at Groote Schuur Hospital in Cape Town. This marked an important milestone in cardiac surgery, capturing the attention of both the medical profession and the world at large. However, long-term survival rates of patients were initially very low. Louis Washkansky, the first recipient of a donated heart, died 18 days after the operation while other patients did not survive for more than a few weeks. The American surgeon Norman Shumway has been credited for his efforts to improve transplantation techniques, along with pioneers Richard Lower, Vladimir Demikhov and Adrian Kantrowitz. By mid-2018, the International Society for Heart and Lung Transplantation registry had recorded more than 146,000 heart transplantations worldwide. The first successful transplant of a heart from a genetically modified pig to a human was performed on 7 January 2022 in Baltimore by heart surgeon Bartley P. Griffith. The recipient, 57-year-old David Bennett, survived for 60 days before dying on 8 March 2022. By the middle of the 20th century, heart disease had surpassed infectious disease as the leading cause of death in the United States, and it is currently the leading cause of deaths worldwide. Since 1948, the ongoing Framingham Heart Study has shed light on the effects of various influences on the heart, including diet, exercise, and common medications such as aspirin.
== Amino acids selective pressure == It has been shown that putting an amino acid bio-synthesizing gene like HIS4 gene under amino acid selective pressure in yeast causes enhancement of expression of adjacent genes which is due to the transcriptional co-regulation of two adjacent genes in Eukaryota.
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.
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.